CA1254716A - Chlorosilane dispropotionation catalyst and method for producing a silane compound by means of the catalyst - Google Patents
Chlorosilane dispropotionation catalyst and method for producing a silane compound by means of the catalystInfo
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- CA1254716A CA1254716A CA000489782A CA489782A CA1254716A CA 1254716 A CA1254716 A CA 1254716A CA 000489782 A CA000489782 A CA 000489782A CA 489782 A CA489782 A CA 489782A CA 1254716 A CA1254716 A CA 1254716A
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Abstract
ABSTRACT OF DISCLOSURE
A chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:
(A) where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and a tertiary amine hydrochloride of the formula:
A chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:
(A) where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more, and a tertiary amine hydrochloride of the formula:
Description
~lZ.~71~
TIT:LE OF THE INVENTIO~
CHLOROSIL~NE DISPROPORTIONATION CAT~LYST
AND METHOD FOR PRODUCING A SILANE COMPO~ND
BY MEANS OF THE CATALYST
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a chlorosilane disproportionation catalyst and a method for producing a silane compound by means oE the catalyst. More particularly, the present invention relates to a chlorosilane disproportionation catalyst comprising a specific tertiary amine and a hydrochloride -thereof as the main components, and a method for con-tinuously producing a silane compound such as dichlorosilanei monochlorosilane or monosilane, by supplying a starting material chlorosilane and the catalyst into a reaction tower, whereby the disproportionation reaction by means of the specific catalyst and the separation by distillation are conducted simultaneously. Further, the present invention relates to a process for producing a silane compound efficiently by combining a process for synthesizing trichlorosilane from sillcon of metallurgical grade or silicon tetrachloride, with the above method for producing a silane compound.
. ;
~l~SL~71ti DESCRIPTION_OF THE PRIOR ART
Demands for silane compounds such as dichlorosilane (SiH2C12), monochlorosilane (SiH3Cl) and monosilane (SiH4~ are expected to increase more and more as they are useful as the raw materials for the high purity silicon to be used ~or elements for semiconductors, solar cells 7 etc. In particular, it has been desired that dichlorosilane and monosilane be produced efficiently and in a large quantity.
It is known to obtain a silane by the disproportionation reaction of SiHC13 in the presence of a catalyst, in accordance with the following equilibrium reactions.
(1) 2SiHC13 ~=~ SiH2C12 ~ SiC14
TIT:LE OF THE INVENTIO~
CHLOROSIL~NE DISPROPORTIONATION CAT~LYST
AND METHOD FOR PRODUCING A SILANE COMPO~ND
BY MEANS OF THE CATALYST
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a chlorosilane disproportionation catalyst and a method for producing a silane compound by means oE the catalyst. More particularly, the present invention relates to a chlorosilane disproportionation catalyst comprising a specific tertiary amine and a hydrochloride -thereof as the main components, and a method for con-tinuously producing a silane compound such as dichlorosilanei monochlorosilane or monosilane, by supplying a starting material chlorosilane and the catalyst into a reaction tower, whereby the disproportionation reaction by means of the specific catalyst and the separation by distillation are conducted simultaneously. Further, the present invention relates to a process for producing a silane compound efficiently by combining a process for synthesizing trichlorosilane from sillcon of metallurgical grade or silicon tetrachloride, with the above method for producing a silane compound.
. ;
~l~SL~71ti DESCRIPTION_OF THE PRIOR ART
Demands for silane compounds such as dichlorosilane (SiH2C12), monochlorosilane (SiH3Cl) and monosilane (SiH4~ are expected to increase more and more as they are useful as the raw materials for the high purity silicon to be used ~or elements for semiconductors, solar cells 7 etc. In particular, it has been desired that dichlorosilane and monosilane be produced efficiently and in a large quantity.
It is known to obtain a silane by the disproportionation reaction of SiHC13 in the presence of a catalyst, in accordance with the following equilibrium reactions.
(1) 2SiHC13 ~=~ SiH2C12 ~ SiC14
(2) 2SiH2C12~=~ SiHC13 ~ SiH3Cl
(3) 2SiH3C1 ~ ~ SiH + SiH Cl
(4) 4SiHC13 ~=~ SiH4 ~ 3SiC14 (as a whole) The disproportionation of chlorosilanes has been studied since old, and various proposals have been made.
However, they still have disadvantages. For exa~ple, (i) the method of using nitriles as taught in U.S. Patent No.
2,732,282 has to be conducted at a reaction temperature of 150C and above; (ii) the method of using aliphatic cyanamides as taught in U.S. Patent No. 2,732,280 requires the pretreatment with a Lewis acid; (iii) the method of using dimethylformamide or dimethylbutylamide as taught in U.S. Patent No. 3,222~511 is liable to . :
t~
deterlorate the catalyst used for the reaction; and (iv) the method of using a tertiary amine containing a hydrocarbon composed of an alkyl group with 1 or 2 carbon atoms, as taught in U.S. Patent No. 2,834,648 is required to be conducted at a temperature o 150C and above, as is the case with the catalyst of the above-mentioned method (i), besides which a pressure resistant vessel has to be used, and, in spite of its equilibrated conversion ratio (calculated value) being lS~ at the reaction temperature of 150C, the actual conversion ratio is as low as about 10%, hence a large size apparatus is required to attain a desired quantity of production.
Fur-ther, U.S. Patent No. 4,113,S45 discloses use of a fixed bed type reactor packed w~th an anion exchange resin containing a tertiary amine as the catalyst, wherein a starting material chlorosilane such as trichlorosilane or dichlorosilane is supplied in a liquid state rom one port of the reactor and reacted at a temperature of from 30 to 200C under a pressure of from 1 to 30 atm, whereby a reaction product comprising monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride is obtainable from the other port of the reactor. However, since the above~mentioned equations (1), (2) and (3) for the 25 disproportionation reaction are equilibrium reactions, it is not possible to complete the reaction o the starting material chlorosilane 100~, even if -the reaction is l~S'~7~i conducted for an extended period oE time. For example, the following Table indicates the equilibrated composition of monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride at a temperature of 80C when the disproportionation reaction of trichlorosilane or dichlorosilane as the starting material has reached the state of equilibrium.
(mol ~) Starting ~-~ - Mono- _ Tri- Silicon materiai Mono- chloro- Dichloro- chloro- tetra-10 silane silane silane silane silane chloride .. _ _ .___ __ Trichloro- 0.04 0.52 10.6 77.1 11.8 silane Dichloro- 10.2 15.6 38.8 34.7 0.65 sllane _ _ Further, even when the disproportionation reaction is brought to the equilibrated condition by using trichlorosilane as the starting material, monosilane and rnonochlorosilane contained in the reaction product are 0.04 mol ~ and 0.52 mol ~, respectively, which figures indica-te a very low reaction rate for producing monosilane or monochlorosilane in a single stage reaction~ Therefore, when, for example, monosilane is produced by using trichlorosilane as the starting material, the reaction product from the reaction vessel at the first stage is charged in a distilling device to separate a mixture containing therein monosilane, monochlorosilane, and dichlorosilane, wherein lZS~7~fi dichlorosilane is the principal component (composition ~) and a mixture of trichlorosila~e and silicon -tetrachloride (composition B), and then the composition A
is fed into the reaction vessel at the second stage, whereupon, since the equilibrated composition from the disproportionation reaction contains 10.2 mol % of monosilane, as is apparen-t from the table, monosilane can be separated and recovered by feeding this reaction product into the distilling apparatus. However, since the rate of reaction in the disproportionation reaction is low, the unreacted substance should be circulated in a large quantity for use, with the consequence that enormous amount of energy was disadvantageously required for the operations of the reaction vessel and the distilling tower.
Furthermore, N-methyl-2-pyrrolidone, methyl-imidazole, tetramethylurea, tetramethylguanidine, trimethylsilylimidazole, benzothiazole, N,N-dimethylacetamide and the like, as disclosed e.g.
U.S. Patents No. 4,018,871 and 4,038,371 or Japanese Unexamined Patent Publication No. 17918/1981, exhibit catalytic activities in the disproportionation reaction of silane compounds. ~owever, they are per se solid, or become powdery solid when brought in contact with a silane compound such as trichlorosilane or dichlorosilane. Consequently, it becomes difficult to separate them ~rom the silane compound produced by the ~12S~7~
disproportionation reaction. Thus, they are hardly applicable to a practical operation on an industrial scale.
SUMMARY OF THE INVENTION
It is an object of the presen-t invention to provide a chlorosilanè dispropor-tiona-tion catalyst whereby a disproportionation reaction can be completed in a short period o time at a low temperature ~ith a high conversion, by using a speciEic tertiary amine and a hydrochloride thereof as the disproportionation catalyst.
A second object of the present invention is to provide a method for continuously producing a silane compound such as monosilane, monochlorosilane or dichlorosilane from a starting material chlorosilane such 1~ as trichlorosilane.
A third object of the present invention is to reuse silicon tetrachloride formed as a by-product by -the disproportionation reaction. As shown in the foregoing equation (4), when 1 mol of SiH4 is produced by the disproportionation reaction, 3 mol of SiC14 is obtained as a by-product. In terms of weight, 17 kg of SiC14 is produced with respect to 1 kg of SiH4. When SiH4 is to be obtained in a large quantity and at a low cost, this by-product ~iC14 is required to be re-used.
Heretofore, in the method of using an ion-exchange resin, the by-product SiC14 is introduced into a reaction system consis-ting of silicon of metallurgical grade, ~L~S4~7~;
hydrogen, and hydrogen chloride, then treated at a temperature of 600C or so, and re-converted to trichlorosilane (SiHCl3). However, as described in the Eoregoing, since the reac-tion rate in the disproportionation reaction is low, a large amount of unreacted substance needs to be used by recycling, on account of which the reaction vessel and the distilling apparatus should be made large in scale. Thus, an enormous amount of energy is disadvantageously requlred.
That is to say, the third object of the present invention is to provide an integral process with the least amount of recycling of -the unreacted substance and less energyi~consumption by use of the method according to the second object oE the present invention which is excellent in the rate of disproportionation reaction, including the re-use of SiCl4 as a by-product.
Namely, the present invention provides a chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:
R\
~ N-R (A) where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more~ and a tertiary amine hydrochloride of the formula:
R\ +
/ N~RH Cl (B) where R is as defined above.
i2S9L'~
Further, the present invention provides a method for continuously producing a silane compound such as monosilane or dichlorosilane by the disproportionation reac-tion of a starting ma-terial chlorosilane such as trichlorosilane, which comprises:
a) supplying the starting material chlorosilane and the above-mentioned chlorosilane disproportionation catalyst into a reaction tower having a distilling function;
b) obtaini.ng, from the top of the tower, a silane compound containing more hydrogen atoms than the starting material chlorosilane;
c) withdrawing, from the bottom of the tower, a liquid mixture comprising the catalyst and silane compounds containing more chlorine atoms as by-products;
d) separating the silane compounds and the catalyst in the liquid mixture; and e) recycling the separated catalyst to the reaction tower.
BRIEF DESCRIPTION OF T~E DRAWINGS
Figure l is a schematic diagram illustrating an apparatus used for the production of silane compounds as described in Examples.
Figures 2 is a schematic diagram illustrating the process for the preparation of the starting material according to a Comparative Example.
Figures 3 and ~ are schematic diagrams illustrating the processes for the production of the starting ~S~
g materials according to the Examples of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the chlorosilane is at least one chlorosilane selected from SiHC13, SiH2C12 and The reason why the sum of carbon atoms in the aliphatic hydrocarbon groups as R is limited to 12 or more in the present invention is that when a -tertiary amine having less than 12 carbon atoms is added to the chlorosilane, white solid will form and it becomes impossible to conduct the reaction in a uniform liquid phase, and as will be apparent from Examples given hereinafter, the tertiary amine having less than 12 ~5 carbon atoms is inferior in the disproportionation reaction rate to the one having 12 or more carbon atoms.
There is no particular restriction as to the upper limit of the sum of carbon atoms. However, from the viewpoints of the performance and costs, the sum of carbon atoms is preferably from 12 to 36.
As the compound of the formula (A), there may be mentioned trl-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n decylamine and tri-n-dodecylamine.
The compound of the formula (B) is a hydrochloride of the compound represented by the formula (A) and is usually readily obtained by adding hydrochloric acid or 12S~7~6 -- 10 -- . , -hydrogen chloride gas to a solution of the above-mentioned tertiary amine..
When the compounds of the Eormulas (A) and (B) are to be used as a catalyst, the tertiary amine and its hydrochloride are preferably used in such proportions that the former constitutes from 20 to 98 mol % and the latter constitutes from 2 to 80 mol %. If the latter is less than 2 mol %, -the catalytic activity is weak, and if the latter exceeds 80 mol ~, hydrochloric acid is likely to be freed during the reaction, thus leading to the following reactions, whereby it becomes difficult to obtain the desired silane compound having a greater number of hydrogen atoms efficiently.
SiH4 + HCl SiH3Cl H2 SiH3Cl + HCl > SiH2Cl2 ~ H2 SiH2C12 ~ HCl ~ SiHCl3 ~ H2 SiHCl3 + HCl- ' SiC14 + H2 It is particularly preferred that the catalyst comprises from 70 to 90 mol % of the tertiary amine of ~ 20 the formula (A) and from 10 to 30 mol % of the tertiary amine hydrochloride of the formula (B).
The catalyst is used preferably in an amount of from 2 to 50 mol % relative to the starting material chlorosilane.
A particularly preferred catalyst comprises from 70 to 90 mol ~ o~ tri-n-butylamine and/or tri-n-octylamine, and from 10 to 30 mol ~ of tri-n-butylamine hydrochloride and/or tri-n-octylamine hydrochloride.
~S~t~
According to the present invention as described in . _ -the foregoing, the following e~fects will be obtained.
(1) The catalyst of the presen-t invention provides a conversion which is closer to the equilibrated conversion, at a temperature of less than 150C in comparison with the conventional catalyst.
(2) When the catalyst of the present invention is used, the equilibrated conversion is reached in a short period of time, which means a high disproportionation velocity, and which makes it possible to reduce -the size of the reaction apparatus.
(3) The catalyst according to the present invention is completely soluble in the chlorosilane starting material, and also has a boiling point of 200C and above. Accordingly, it serves to lower the vapor pressure in the reaction liquid, and advantageously contributes to saEety in the operation.
(4) The catalyst can be readily separated from the reaction product such as SiH2C12 or SiH4.
However, they still have disadvantages. For exa~ple, (i) the method of using nitriles as taught in U.S. Patent No.
2,732,282 has to be conducted at a reaction temperature of 150C and above; (ii) the method of using aliphatic cyanamides as taught in U.S. Patent No. 2,732,280 requires the pretreatment with a Lewis acid; (iii) the method of using dimethylformamide or dimethylbutylamide as taught in U.S. Patent No. 3,222~511 is liable to . :
t~
deterlorate the catalyst used for the reaction; and (iv) the method of using a tertiary amine containing a hydrocarbon composed of an alkyl group with 1 or 2 carbon atoms, as taught in U.S. Patent No. 2,834,648 is required to be conducted at a temperature o 150C and above, as is the case with the catalyst of the above-mentioned method (i), besides which a pressure resistant vessel has to be used, and, in spite of its equilibrated conversion ratio (calculated value) being lS~ at the reaction temperature of 150C, the actual conversion ratio is as low as about 10%, hence a large size apparatus is required to attain a desired quantity of production.
Fur-ther, U.S. Patent No. 4,113,S45 discloses use of a fixed bed type reactor packed w~th an anion exchange resin containing a tertiary amine as the catalyst, wherein a starting material chlorosilane such as trichlorosilane or dichlorosilane is supplied in a liquid state rom one port of the reactor and reacted at a temperature of from 30 to 200C under a pressure of from 1 to 30 atm, whereby a reaction product comprising monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride is obtainable from the other port of the reactor. However, since the above~mentioned equations (1), (2) and (3) for the 25 disproportionation reaction are equilibrium reactions, it is not possible to complete the reaction o the starting material chlorosilane 100~, even if -the reaction is l~S'~7~i conducted for an extended period oE time. For example, the following Table indicates the equilibrated composition of monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride at a temperature of 80C when the disproportionation reaction of trichlorosilane or dichlorosilane as the starting material has reached the state of equilibrium.
(mol ~) Starting ~-~ - Mono- _ Tri- Silicon materiai Mono- chloro- Dichloro- chloro- tetra-10 silane silane silane silane silane chloride .. _ _ .___ __ Trichloro- 0.04 0.52 10.6 77.1 11.8 silane Dichloro- 10.2 15.6 38.8 34.7 0.65 sllane _ _ Further, even when the disproportionation reaction is brought to the equilibrated condition by using trichlorosilane as the starting material, monosilane and rnonochlorosilane contained in the reaction product are 0.04 mol ~ and 0.52 mol ~, respectively, which figures indica-te a very low reaction rate for producing monosilane or monochlorosilane in a single stage reaction~ Therefore, when, for example, monosilane is produced by using trichlorosilane as the starting material, the reaction product from the reaction vessel at the first stage is charged in a distilling device to separate a mixture containing therein monosilane, monochlorosilane, and dichlorosilane, wherein lZS~7~fi dichlorosilane is the principal component (composition ~) and a mixture of trichlorosila~e and silicon -tetrachloride (composition B), and then the composition A
is fed into the reaction vessel at the second stage, whereupon, since the equilibrated composition from the disproportionation reaction contains 10.2 mol % of monosilane, as is apparen-t from the table, monosilane can be separated and recovered by feeding this reaction product into the distilling apparatus. However, since the rate of reaction in the disproportionation reaction is low, the unreacted substance should be circulated in a large quantity for use, with the consequence that enormous amount of energy was disadvantageously required for the operations of the reaction vessel and the distilling tower.
Furthermore, N-methyl-2-pyrrolidone, methyl-imidazole, tetramethylurea, tetramethylguanidine, trimethylsilylimidazole, benzothiazole, N,N-dimethylacetamide and the like, as disclosed e.g.
U.S. Patents No. 4,018,871 and 4,038,371 or Japanese Unexamined Patent Publication No. 17918/1981, exhibit catalytic activities in the disproportionation reaction of silane compounds. ~owever, they are per se solid, or become powdery solid when brought in contact with a silane compound such as trichlorosilane or dichlorosilane. Consequently, it becomes difficult to separate them ~rom the silane compound produced by the ~12S~7~
disproportionation reaction. Thus, they are hardly applicable to a practical operation on an industrial scale.
SUMMARY OF THE INVENTION
It is an object of the presen-t invention to provide a chlorosilanè dispropor-tiona-tion catalyst whereby a disproportionation reaction can be completed in a short period o time at a low temperature ~ith a high conversion, by using a speciEic tertiary amine and a hydrochloride thereof as the disproportionation catalyst.
A second object of the present invention is to provide a method for continuously producing a silane compound such as monosilane, monochlorosilane or dichlorosilane from a starting material chlorosilane such 1~ as trichlorosilane.
A third object of the present invention is to reuse silicon tetrachloride formed as a by-product by -the disproportionation reaction. As shown in the foregoing equation (4), when 1 mol of SiH4 is produced by the disproportionation reaction, 3 mol of SiC14 is obtained as a by-product. In terms of weight, 17 kg of SiC14 is produced with respect to 1 kg of SiH4. When SiH4 is to be obtained in a large quantity and at a low cost, this by-product ~iC14 is required to be re-used.
Heretofore, in the method of using an ion-exchange resin, the by-product SiC14 is introduced into a reaction system consis-ting of silicon of metallurgical grade, ~L~S4~7~;
hydrogen, and hydrogen chloride, then treated at a temperature of 600C or so, and re-converted to trichlorosilane (SiHCl3). However, as described in the Eoregoing, since the reac-tion rate in the disproportionation reaction is low, a large amount of unreacted substance needs to be used by recycling, on account of which the reaction vessel and the distilling apparatus should be made large in scale. Thus, an enormous amount of energy is disadvantageously requlred.
That is to say, the third object of the present invention is to provide an integral process with the least amount of recycling of -the unreacted substance and less energyi~consumption by use of the method according to the second object oE the present invention which is excellent in the rate of disproportionation reaction, including the re-use of SiCl4 as a by-product.
Namely, the present invention provides a chlorosilane disproportionation catalyst comprising a tertiary amine of the formula:
R\
~ N-R (A) where each R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups as R is 12 or more~ and a tertiary amine hydrochloride of the formula:
R\ +
/ N~RH Cl (B) where R is as defined above.
i2S9L'~
Further, the present invention provides a method for continuously producing a silane compound such as monosilane or dichlorosilane by the disproportionation reac-tion of a starting ma-terial chlorosilane such as trichlorosilane, which comprises:
a) supplying the starting material chlorosilane and the above-mentioned chlorosilane disproportionation catalyst into a reaction tower having a distilling function;
b) obtaini.ng, from the top of the tower, a silane compound containing more hydrogen atoms than the starting material chlorosilane;
c) withdrawing, from the bottom of the tower, a liquid mixture comprising the catalyst and silane compounds containing more chlorine atoms as by-products;
d) separating the silane compounds and the catalyst in the liquid mixture; and e) recycling the separated catalyst to the reaction tower.
BRIEF DESCRIPTION OF T~E DRAWINGS
Figure l is a schematic diagram illustrating an apparatus used for the production of silane compounds as described in Examples.
Figures 2 is a schematic diagram illustrating the process for the preparation of the starting material according to a Comparative Example.
Figures 3 and ~ are schematic diagrams illustrating the processes for the production of the starting ~S~
g materials according to the Examples of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the chlorosilane is at least one chlorosilane selected from SiHC13, SiH2C12 and The reason why the sum of carbon atoms in the aliphatic hydrocarbon groups as R is limited to 12 or more in the present invention is that when a -tertiary amine having less than 12 carbon atoms is added to the chlorosilane, white solid will form and it becomes impossible to conduct the reaction in a uniform liquid phase, and as will be apparent from Examples given hereinafter, the tertiary amine having less than 12 ~5 carbon atoms is inferior in the disproportionation reaction rate to the one having 12 or more carbon atoms.
There is no particular restriction as to the upper limit of the sum of carbon atoms. However, from the viewpoints of the performance and costs, the sum of carbon atoms is preferably from 12 to 36.
As the compound of the formula (A), there may be mentioned trl-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n decylamine and tri-n-dodecylamine.
The compound of the formula (B) is a hydrochloride of the compound represented by the formula (A) and is usually readily obtained by adding hydrochloric acid or 12S~7~6 -- 10 -- . , -hydrogen chloride gas to a solution of the above-mentioned tertiary amine..
When the compounds of the Eormulas (A) and (B) are to be used as a catalyst, the tertiary amine and its hydrochloride are preferably used in such proportions that the former constitutes from 20 to 98 mol % and the latter constitutes from 2 to 80 mol %. If the latter is less than 2 mol %, -the catalytic activity is weak, and if the latter exceeds 80 mol ~, hydrochloric acid is likely to be freed during the reaction, thus leading to the following reactions, whereby it becomes difficult to obtain the desired silane compound having a greater number of hydrogen atoms efficiently.
SiH4 + HCl SiH3Cl H2 SiH3Cl + HCl > SiH2Cl2 ~ H2 SiH2C12 ~ HCl ~ SiHCl3 ~ H2 SiHCl3 + HCl- ' SiC14 + H2 It is particularly preferred that the catalyst comprises from 70 to 90 mol % of the tertiary amine of ~ 20 the formula (A) and from 10 to 30 mol % of the tertiary amine hydrochloride of the formula (B).
The catalyst is used preferably in an amount of from 2 to 50 mol % relative to the starting material chlorosilane.
A particularly preferred catalyst comprises from 70 to 90 mol ~ o~ tri-n-butylamine and/or tri-n-octylamine, and from 10 to 30 mol ~ of tri-n-butylamine hydrochloride and/or tri-n-octylamine hydrochloride.
~S~t~
According to the present invention as described in . _ -the foregoing, the following e~fects will be obtained.
(1) The catalyst of the presen-t invention provides a conversion which is closer to the equilibrated conversion, at a temperature of less than 150C in comparison with the conventional catalyst.
(2) When the catalyst of the present invention is used, the equilibrated conversion is reached in a short period of time, which means a high disproportionation velocity, and which makes it possible to reduce -the size of the reaction apparatus.
(3) The catalyst according to the present invention is completely soluble in the chlorosilane starting material, and also has a boiling point of 200C and above. Accordingly, it serves to lower the vapor pressure in the reaction liquid, and advantageously contributes to saEety in the operation.
(4) The catalyst can be readily separated from the reaction product such as SiH2C12 or SiH4.
(5) Since the reaction system is a uniform liquid phase system, there is no necessity for agitation and other homogenizing operations. Thus, the transportion and various handling of the catalyst become advantageously simple. There are of course various advantages besides the above.
Now, the method for the disproportionation o a chlorosilane by means o the catalyst of the present l~S4~7~;
invention will be described. Conven-tionai methods may be employed for the production of silane compounds such as SiH2CL2 and SiH4 by the disproportionation reaction by means of the catalyst of the pres~nt inven-tion. For instance, there may be employed a series of operations which comprises mixing the chlorosilane and the catalyst, subjecting the mixture to the disproportionation reaction, and separating the resulting silane compounds such as SiH2C12 and SiH4 by condensation or distillation.
These operations may be carried out simultaneous:ly.
Namely, the disproportionation and/or redistribution of the present invention may be conducted by contacting the chlorosilane with the catalyst of the present inven-tion.
The reaction is conducted preferably at a temperature of from 10 to 300C, more preferably from 20 to 150C.
To activate and reuse the used catalys-t, it- is desirable -to add at least one of hydrogen chloride gas, hydrochloric acid and water, to the used catalyst.
Hydrogen chloride, hydrochloric acid or water may be added to a recycling line for the catalyst or directly to the reaction tower. Further, in the case of hydrogen chloride, it may be added to the line for supplying the starting material chlorosilane to the reaction tower.
The disproportionation may be conducted in a batch system or in a continuous system. However, the following continuous method i 5 preferred.
~4~
In the method for continuously producing a silane compound such as monosilane or dichlorosilane by the disproportionation reaction of a starting material chlorosilane such as trichlorosilane, the above-mentioned catalyst of the present invention and the starting material chlorosilane were supplied to a reaction tower having a distilling function; a silane compound containing more hydrogen atoms than the starting material chlorosilane is obtained from the top of the tower, while a liquid mixture comprising the catalyst and by-product silane compounds containing more chlorine atoms, is withdrawn from the bottom of the reaction tower; then, the silane compounds and the catalyst in the ;
above-mentioned liquid mixture, are separated; and the separated catalyst is then recycled to the reaction tower.
In this method, the reason why -the sum of carbon atoms in the three aliphatic hydrocarbon groups as R of the catalyst is limited to 12 or more, is that compounds containing less than 12 carbon atoms are undesirable since they are likely to form solid substances when contacted with a silane compound such as trichlorosilane, dichlorosilane or silicon tetrachloride, although they have catalytic activities. Namely, the reaction tower to be used in the present invention is a trays tower or a packed tower having a distilling function. Accordingly, the solid substances are likely to clog the plates or the lZS~71t~
packing materials, whereby smooth continuous operation . ._ can hardly be conducted.
The sum of carbon atoms in the three aliphatic hydrocarbon groups as R of the catalyst is preEerably from 12 to 36. A preferred catalyst comprises tri-n-butylamine and/or tri-n-octylamine. The most preferred catalyst is the one obtained by adding at least one member selected from the group consisting of hydrogen chloride gas, hydrochloric acid and water, to tri-n-butylamine and/or tri-n-octylamine. The amount of the addition is adjusted to bring the hydrochloride concentration in the catalyst to a level of from 2 to 80 mol ~, preferably from 10 to 30 mol %.
The catalyst is used preferably in an amount of from 2 to 50 mol ~, more preferably from 5 to 40 mol relative to the starting material chlorosilane.
Now, the reaction tower to be used in the present invention will be described. The reaction tower is of a distillation tower type. For instance, it is a plate tower with its interior being partitioned by sieve trays or bubble cap trays, or a packed tower with its interior filled with packing material such as Raschig rings or pall rings. While the reaction tower may be of any structure, provided that it has a distillation function, the more desirable is a reaction tower having a large liquid hold-up capacity, because the disproportionation reaction of the silane compound according to the present ~ZS~
invention is conducted in a liquid phase. In the reaction tower according -to the present invention, the separation by distillation of the reaction product is carried out simultaneously with the reaction, and accordingly the temperature at the top of the reac-tion tower is low, while the temperature at the bottom of the tower is high. Thus, a temperature gradient is produced within the reaction tower, whereby the reaction temperature is not constant. However~ the reaction is usually conducted at a temperature of from 10 to 300C, preferably from 20 to 150C. If the temperature is less than 10C, the reaction rate is low, and the disproportionation reaction does not substantia]ly proceed. On the other hand, if the temperature exceeds 300C, the thermal decomposition of the catalyt is likely to take place, such being undesirable. The reaction is conducted in a boiling state, and in order to keep the reaction temperature to the above-mentioned ran~e, the gauge pressure is usually maintained at a level of from 0 to 40 kg/cm2, preferably from 0 to 20 kg/cm2.
When the disproportionation reaction of the starting material chlorosilane is conducted in the presence of the catalyst in the reaction tower having the distilling function, the above-mentioned disproportionation - 25 reactions (1), (2) and (3) proceed simultaneously, whereby monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride will be formed.
~s~
Their boiling points are -118C, -30C, 8C, 32C and 56C, respectively. Further, since the reaction -tower per se has the distilling function, there will be a concentration distribution from the top of the tower in the sequence of monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride.
Now, the method for the production o~ a silane compound according to the present invention will be described with reference to the drawings.
Figure 1 is a schematic diagram illustrating the apparatus to be used in Examples of the present invention. The starting material chlorosilane such as trichlorosilane or dichlorosilane is supplied to an upper portion of the reaction tower 1 via a starting material supply line 4. The reaction tower 1 is a stainless steel distilling tower having a diameter o~ 83 mm and a height o~ 2000 mm with la stages. Each tray is a sieve tray having 37 perEorations with a diameter of 1.5 mm. Above the tower 1, a condenser 3 made o stainless steel is provided, which is adapted to be cooled by circulating methanol dry ice in a jacket. At the lower portion of the reaction tower 1, a reboiler 2 equipped with a heater havi~lg a maximum output power o l KW is provided.
In the reaction tower l, separation by distillation takes place simultaneously with the disproportionation reaction, whereby the gas rich in the low boiling point components formed by the disproportionation reaction moves upward and cooled by the condenser 3, whereby the accompanying high boiling point components will be condensed. The low boiling point components will then be condensed by a condenser 6 made of stainless steel and cooled with liquid nitrogen, and recovered in a liquid state in a collecting tank 7.
On the other hand, the high boiling point components such as trichlorosilane and silicon tetrachloride formed by the disproportionation reaction, will move to the bottom of the tower, and will then be withdrawn together with the catalyst to the evaporation tank 9 while the liquid level is controlled by the reboiler 2. The evaporation tank 9 is a stainless steel vessel having an internal capaeity of 3 liters and equipped with an agitator. A jaeke-t is provided thereon, and a heating oil is eirculated in the jacket to heat the evaporation tank. This evaporation tank 9 is operated at a temperature which is higher than the boiling point of silicon tetrachloride formed by the disproportionation reaction and lower than the boiling point of the eatalyst. Triehlorosilane and silieon tetraehloride withdrawn from the reboiler 2 are evaporated, collected in a condenser 11 eooled with methanol dry iee, and recovered in a tank 12. The catalyst remaining in the evaporation tank 9 is withdrawn by a pump 10 and reeycled to the top of the reaction tower 1. If necessary, at l~S4'7~6 least one of hydrogen chloride gas, hydrochloric acid and water is supplemented via any one of supply lines 13 to 16.
For the purpose of the comparison, Figure 2 illustrates a conventional disproportionation method wherein an ion exchange resin is employed. Referring to Figure 2, reference numeral 20 designates a trichlorosilane synthesizing tower, from which produced gas 26, consisting principally of SiHC13 and SiC14, enters into the subsequent distilling tower 21. The principal components of the gas at the top part of the distilling tower are SiHC13 and SiH~C12 which enter further into the subsequent distilling tower 22. On the other hand, SiHC13 is taken out of the bottom part 31 of the distilling tower 22, then introduced into a disproportionation tower 2~ filled with an ion-exchange resin, and disproportionated~ The disproportionated mixture o silanes enters into the distilling tower 21, from the bottom part 30 of which a high boiling point substance of SiC14 is taken out and sent back to the trichlorosilane synthesizing tower 20.
On the other hand, SiH2C12 as the principal component at the top part of the distilling tower 22 enters into disproportionation tower 25 filled with an ion-exchange resin. The silane compound as disproportionated therein is then introduced into a silane distilling tower 23, from the top 29 of which SiH4 is taken out. A high i~S4~6 boiling point component from -the bottom 32 of the distllling tower 23 is returned to the distilling tower 22.
As described in the above, the conven-tional disproportionation process required two units of disproportionation tower and three units of the distilling tower, the total process steps for the reaction being six, including the synthesis of trichlorosilane.
In the following, explanations will be given in reference to Figure 3 as to the disproportionation reaction according to the present invention. Referring to the flow chart in Figure 3, a reference numeral 4Q
designates a trichlorosilane synthesizing vessel to carry out the first step of the hydrogenation reaction according to the present invention. Produced gas 44 contains SiHCl3 and SiCl4 as the principal components which are sent into a distilling tower 41 to carry out the second step of the distillation. The component at the top of the distilling tower 41 is mainly SiHCl3 which is introduced into a reaction tower 43 which carries out the third step of the reaction and in which the tertiary amine and its hydrochloride are present as the catalyst.
From the top of this tower 43, a mixture of silanes 49 consisting principally of SiH4 is taken out, and forwarded to a silane distilling tower 42 to carry out the fifth step of the distillation, from which SiH4 as the end product is taken out as the tower top component.
On the o-ther hand, the high boiling point component in -the silane distilling tower 42 is returned to the reac-tion and distilling tower 43. Since the high boiling point componen-t in the reaction tower contains a mixture oE silanes with SiHC13 and SiC14 as the principal components as well as the catalyst, this high boiling point component is introduced into a distilling vessel 52 to carry ou-t the fourth step of -the separation where the mixture of silanes and the catalyst are separated. The catalyst 4~ is returned to the reaction tower 43, while -the mixture of silanes is recycled to the distilling tower 41. SiC14 is sent back to the trichlorosilane synthesizing vessel 40.
Thus, the present invention suffices with a single unit of the reaction tower and two units of the distilling tower, and the total process steps can be five, even inclusive of the trichlorosilane synthesizing vessel and the evaporator, hence the me-thod of the present invention provides a simplified process in comparison with the conventional method.
The operating condi-tions at each process step are as ~ollows: the first step is conducted at the operating temperature of from 400 -to 700C under a pressure range of Erom zero to 30 kg/cm2G; the second step is carried 25 out under a pressure in a range of from zero to 2 kg/cm2G; the third step is carried out at a temperature in a range oE Erom zero to 300C under a pressure range l~S~716 of from zero to 40 kg/cm2G; the fourth step is done a-t a _ temperature in a range of from 70 to 200C under a pressure range of from zero to 4 kg/cm2G; and the fiEth step is conducted at a temperature in a range of from -lO to -40C under a pressure range of from 15 to 40 kg/cm2G, although such temperature and pressure conditions depend also on the purity oE SiH4 as the ultimate product.
As will be described in E~amples, the present invention provides a high rate of disproportionation reactionr besides the afore-described various effects, hence the recycling quantity of the unreacted substances becomes decreased with the-consequent reduction in size of the distilling tower andr further, least utility, and other advantages.
- In the foregoing explanations of the present invention, -there has been shown a process of obtaining SiH4 as the end product. It should however be noted that the same effect as mentioned above can be obtained in the case of taking out SiH2C12 as the end product.
In the trichlorosilane synthesizing vessel in the first step, trichlorosilane i5 prepared from silicon of metallurgical grade as a starting material. Ins-tead of this process, there may be employed a process as shown in Figure 4 wherein silica, carbon and chlorine as starting materials are reac-ted at a high temperature in a silicon tetrachloride synthesizing furnace to produce silicon 1;~Sg~ 6 tetrachloride, and the silicon tetrachloride thus obtained is purified in a low boiling component removal tower B and a high boiling component removal tower C, then introduced into a trichlorosilane synthesizing tower D and converted to trichlorosilane by reduction with hydrogen. This method is advantageous in the case where silane gas is produced in a large amountr since the power consumption is thereby essentially small, and the cost for the operation is low. Here, the synthesis of silicon 1~ tetrachloride is conducted usually at a temperature of from llO0 to 1400C in a reaction system such as a fixed bed system, a transfer bed system or a fluidized bed system. Further, when silicon carbide is added to the starting material as a catalyst in an amount of from l to 10% by weight, the reaction rate is improved. Further, from the viewpoint of the efficiency of energy, the synthesis of trichlorosilane by reduction with hydrogen is advantageously conducted at a molar ratio of SiCl4/H2 within a range of from l : l to l : 2, at a temperature within a range of from 1200 to 1400C.
Now, the present invention will be described in detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by these specific Examples.
Using trichlorosilane (SiHCl3), which was placed in an autoclave (SUS 304) of 500 cc capacity and provided , ~S~7~l6 - 23 ~
with a jacket and an agitator, the disproportionation reaction was conducted in a hermetically sealed condition by varying the reac-tion temperature, and the kind and amount oE the catalyst, as shown in Table 1 below. The quantity of the chlorosilane in the gas phase was quantitatively measured by gas chromatography time-sequentially. The amount of the hydrochloride in each case was 20 mol % relative to the tertiary amine.
The hydrochloride was formed by in-troducin~ the tertiary amine into the autoclave and then blowing HC1 thereinto.
A change in the quantity of SiHCl3 in the gas phase corresponds to its conversion ra-tio, and Table 1 below indicates the time until the concentration of SiHCl3 takes a constant value and the concentrations of SiHC13 and SiC14 at that time. Table 1 shows that -the shorter the time is, the faster is the conversion veloci-ty (i.e.
disproportionation velocity), and the lower the concentration value of SiHCl3 is, the better becomes the conversion. Also, in Table l below, the equilibrated concentration of SiHCl3 obtained by calculation is shown as a reference.
For the purpose of comparison, under the same conditions as in E~ample l above, the dispropor-tionation reactions were carried out by using trimethylamine, 25 triethylamine, tri-n-propylamine, trimethylamine hydrochloride, and triethylamine hydrochloride as the catalysts, at the reaction temperatures of 25C, 50C, :lZS~71ti and 100C, respectlvely~ The results are shown in Table 1 below (experiments No. 20 - No. 30). The catalysts were present as solid substance in the reaction liquid, and the agitator was employed for sufficient dispersion of the catal~sts.
According to the present invention as shown in Table l, the equilibrated conversion was obtained in 38 min.
and 5 min. at the respective reaction temperatures of 25C and 100C in experiments No. 8 and No. 9. In contrast to this, according to comparative experiments No. 20 and No. 22, the equilibrated conversion was not obtained even at the end of 240 min. and lO min., respectiveLy. This diffexence leads to a difference in the production quantity of SiH2Cl2 which amounts to 7 times and 2 times, respectively, when manufacturing SiH2C12 from SiHC13 in the reaction vessels of the same capacity. This proves that the effect to be derived from the present invention is apparently superior.
- ~5 -Table 1 iL~59L7~
, . _ Time lapsed 8iHCl3 con- SiCl4 con- Equilibrated E~cpeIi- ~eac- Quantity Starting until SiHC13 centration centration SiHC14 con-ment Kind of catalyst tion of material concentra- when it when it centration No. temp. catalyst SiHCl3 tion becomes became became (~) (mol~ (mol) constant(min) constant(96) constant t%) (%) _ 1 Tri-n-butylamine50 0.1 1 779. 8 10.3 79. 0 2 Tli-n-pentylamine 50 0. 1 1 7 79. 4 10.5 79.0 3 Tri-n-ha~ylamine50 0. 1 1 679.5 10.3 79. 0 4 Tri-n-heptylamine 50 0.1 1 6 79.3 11.0 79. 0 Tri-n-octylamine50 0. 1 1 679. 4 10. 9 79. 0
Now, the method for the disproportionation o a chlorosilane by means o the catalyst of the present l~S4~7~;
invention will be described. Conven-tionai methods may be employed for the production of silane compounds such as SiH2CL2 and SiH4 by the disproportionation reaction by means of the catalyst of the pres~nt inven-tion. For instance, there may be employed a series of operations which comprises mixing the chlorosilane and the catalyst, subjecting the mixture to the disproportionation reaction, and separating the resulting silane compounds such as SiH2C12 and SiH4 by condensation or distillation.
These operations may be carried out simultaneous:ly.
Namely, the disproportionation and/or redistribution of the present invention may be conducted by contacting the chlorosilane with the catalyst of the present inven-tion.
The reaction is conducted preferably at a temperature of from 10 to 300C, more preferably from 20 to 150C.
To activate and reuse the used catalys-t, it- is desirable -to add at least one of hydrogen chloride gas, hydrochloric acid and water, to the used catalyst.
Hydrogen chloride, hydrochloric acid or water may be added to a recycling line for the catalyst or directly to the reaction tower. Further, in the case of hydrogen chloride, it may be added to the line for supplying the starting material chlorosilane to the reaction tower.
The disproportionation may be conducted in a batch system or in a continuous system. However, the following continuous method i 5 preferred.
~4~
In the method for continuously producing a silane compound such as monosilane or dichlorosilane by the disproportionation reaction of a starting material chlorosilane such as trichlorosilane, the above-mentioned catalyst of the present invention and the starting material chlorosilane were supplied to a reaction tower having a distilling function; a silane compound containing more hydrogen atoms than the starting material chlorosilane is obtained from the top of the tower, while a liquid mixture comprising the catalyst and by-product silane compounds containing more chlorine atoms, is withdrawn from the bottom of the reaction tower; then, the silane compounds and the catalyst in the ;
above-mentioned liquid mixture, are separated; and the separated catalyst is then recycled to the reaction tower.
In this method, the reason why -the sum of carbon atoms in the three aliphatic hydrocarbon groups as R of the catalyst is limited to 12 or more, is that compounds containing less than 12 carbon atoms are undesirable since they are likely to form solid substances when contacted with a silane compound such as trichlorosilane, dichlorosilane or silicon tetrachloride, although they have catalytic activities. Namely, the reaction tower to be used in the present invention is a trays tower or a packed tower having a distilling function. Accordingly, the solid substances are likely to clog the plates or the lZS~71t~
packing materials, whereby smooth continuous operation . ._ can hardly be conducted.
The sum of carbon atoms in the three aliphatic hydrocarbon groups as R of the catalyst is preEerably from 12 to 36. A preferred catalyst comprises tri-n-butylamine and/or tri-n-octylamine. The most preferred catalyst is the one obtained by adding at least one member selected from the group consisting of hydrogen chloride gas, hydrochloric acid and water, to tri-n-butylamine and/or tri-n-octylamine. The amount of the addition is adjusted to bring the hydrochloride concentration in the catalyst to a level of from 2 to 80 mol ~, preferably from 10 to 30 mol %.
The catalyst is used preferably in an amount of from 2 to 50 mol ~, more preferably from 5 to 40 mol relative to the starting material chlorosilane.
Now, the reaction tower to be used in the present invention will be described. The reaction tower is of a distillation tower type. For instance, it is a plate tower with its interior being partitioned by sieve trays or bubble cap trays, or a packed tower with its interior filled with packing material such as Raschig rings or pall rings. While the reaction tower may be of any structure, provided that it has a distillation function, the more desirable is a reaction tower having a large liquid hold-up capacity, because the disproportionation reaction of the silane compound according to the present ~ZS~
invention is conducted in a liquid phase. In the reaction tower according -to the present invention, the separation by distillation of the reaction product is carried out simultaneously with the reaction, and accordingly the temperature at the top of the reac-tion tower is low, while the temperature at the bottom of the tower is high. Thus, a temperature gradient is produced within the reaction tower, whereby the reaction temperature is not constant. However~ the reaction is usually conducted at a temperature of from 10 to 300C, preferably from 20 to 150C. If the temperature is less than 10C, the reaction rate is low, and the disproportionation reaction does not substantia]ly proceed. On the other hand, if the temperature exceeds 300C, the thermal decomposition of the catalyt is likely to take place, such being undesirable. The reaction is conducted in a boiling state, and in order to keep the reaction temperature to the above-mentioned ran~e, the gauge pressure is usually maintained at a level of from 0 to 40 kg/cm2, preferably from 0 to 20 kg/cm2.
When the disproportionation reaction of the starting material chlorosilane is conducted in the presence of the catalyst in the reaction tower having the distilling function, the above-mentioned disproportionation - 25 reactions (1), (2) and (3) proceed simultaneously, whereby monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride will be formed.
~s~
Their boiling points are -118C, -30C, 8C, 32C and 56C, respectively. Further, since the reaction -tower per se has the distilling function, there will be a concentration distribution from the top of the tower in the sequence of monosilane, monochlorosilane, dichlorosilane, trichlorosilane and silicon tetrachloride.
Now, the method for the production o~ a silane compound according to the present invention will be described with reference to the drawings.
Figure 1 is a schematic diagram illustrating the apparatus to be used in Examples of the present invention. The starting material chlorosilane such as trichlorosilane or dichlorosilane is supplied to an upper portion of the reaction tower 1 via a starting material supply line 4. The reaction tower 1 is a stainless steel distilling tower having a diameter o~ 83 mm and a height o~ 2000 mm with la stages. Each tray is a sieve tray having 37 perEorations with a diameter of 1.5 mm. Above the tower 1, a condenser 3 made o stainless steel is provided, which is adapted to be cooled by circulating methanol dry ice in a jacket. At the lower portion of the reaction tower 1, a reboiler 2 equipped with a heater havi~lg a maximum output power o l KW is provided.
In the reaction tower l, separation by distillation takes place simultaneously with the disproportionation reaction, whereby the gas rich in the low boiling point components formed by the disproportionation reaction moves upward and cooled by the condenser 3, whereby the accompanying high boiling point components will be condensed. The low boiling point components will then be condensed by a condenser 6 made of stainless steel and cooled with liquid nitrogen, and recovered in a liquid state in a collecting tank 7.
On the other hand, the high boiling point components such as trichlorosilane and silicon tetrachloride formed by the disproportionation reaction, will move to the bottom of the tower, and will then be withdrawn together with the catalyst to the evaporation tank 9 while the liquid level is controlled by the reboiler 2. The evaporation tank 9 is a stainless steel vessel having an internal capaeity of 3 liters and equipped with an agitator. A jaeke-t is provided thereon, and a heating oil is eirculated in the jacket to heat the evaporation tank. This evaporation tank 9 is operated at a temperature which is higher than the boiling point of silicon tetrachloride formed by the disproportionation reaction and lower than the boiling point of the eatalyst. Triehlorosilane and silieon tetraehloride withdrawn from the reboiler 2 are evaporated, collected in a condenser 11 eooled with methanol dry iee, and recovered in a tank 12. The catalyst remaining in the evaporation tank 9 is withdrawn by a pump 10 and reeycled to the top of the reaction tower 1. If necessary, at l~S4'7~6 least one of hydrogen chloride gas, hydrochloric acid and water is supplemented via any one of supply lines 13 to 16.
For the purpose of the comparison, Figure 2 illustrates a conventional disproportionation method wherein an ion exchange resin is employed. Referring to Figure 2, reference numeral 20 designates a trichlorosilane synthesizing tower, from which produced gas 26, consisting principally of SiHC13 and SiC14, enters into the subsequent distilling tower 21. The principal components of the gas at the top part of the distilling tower are SiHC13 and SiH~C12 which enter further into the subsequent distilling tower 22. On the other hand, SiHC13 is taken out of the bottom part 31 of the distilling tower 22, then introduced into a disproportionation tower 2~ filled with an ion-exchange resin, and disproportionated~ The disproportionated mixture o silanes enters into the distilling tower 21, from the bottom part 30 of which a high boiling point substance of SiC14 is taken out and sent back to the trichlorosilane synthesizing tower 20.
On the other hand, SiH2C12 as the principal component at the top part of the distilling tower 22 enters into disproportionation tower 25 filled with an ion-exchange resin. The silane compound as disproportionated therein is then introduced into a silane distilling tower 23, from the top 29 of which SiH4 is taken out. A high i~S4~6 boiling point component from -the bottom 32 of the distllling tower 23 is returned to the distilling tower 22.
As described in the above, the conven-tional disproportionation process required two units of disproportionation tower and three units of the distilling tower, the total process steps for the reaction being six, including the synthesis of trichlorosilane.
In the following, explanations will be given in reference to Figure 3 as to the disproportionation reaction according to the present invention. Referring to the flow chart in Figure 3, a reference numeral 4Q
designates a trichlorosilane synthesizing vessel to carry out the first step of the hydrogenation reaction according to the present invention. Produced gas 44 contains SiHCl3 and SiCl4 as the principal components which are sent into a distilling tower 41 to carry out the second step of the distillation. The component at the top of the distilling tower 41 is mainly SiHCl3 which is introduced into a reaction tower 43 which carries out the third step of the reaction and in which the tertiary amine and its hydrochloride are present as the catalyst.
From the top of this tower 43, a mixture of silanes 49 consisting principally of SiH4 is taken out, and forwarded to a silane distilling tower 42 to carry out the fifth step of the distillation, from which SiH4 as the end product is taken out as the tower top component.
On the o-ther hand, the high boiling point component in -the silane distilling tower 42 is returned to the reac-tion and distilling tower 43. Since the high boiling point componen-t in the reaction tower contains a mixture oE silanes with SiHC13 and SiC14 as the principal components as well as the catalyst, this high boiling point component is introduced into a distilling vessel 52 to carry ou-t the fourth step of -the separation where the mixture of silanes and the catalyst are separated. The catalyst 4~ is returned to the reaction tower 43, while -the mixture of silanes is recycled to the distilling tower 41. SiC14 is sent back to the trichlorosilane synthesizing vessel 40.
Thus, the present invention suffices with a single unit of the reaction tower and two units of the distilling tower, and the total process steps can be five, even inclusive of the trichlorosilane synthesizing vessel and the evaporator, hence the me-thod of the present invention provides a simplified process in comparison with the conventional method.
The operating condi-tions at each process step are as ~ollows: the first step is conducted at the operating temperature of from 400 -to 700C under a pressure range of Erom zero to 30 kg/cm2G; the second step is carried 25 out under a pressure in a range of from zero to 2 kg/cm2G; the third step is carried out at a temperature in a range oE Erom zero to 300C under a pressure range l~S~716 of from zero to 40 kg/cm2G; the fourth step is done a-t a _ temperature in a range of from 70 to 200C under a pressure range of from zero to 4 kg/cm2G; and the fiEth step is conducted at a temperature in a range of from -lO to -40C under a pressure range of from 15 to 40 kg/cm2G, although such temperature and pressure conditions depend also on the purity oE SiH4 as the ultimate product.
As will be described in E~amples, the present invention provides a high rate of disproportionation reactionr besides the afore-described various effects, hence the recycling quantity of the unreacted substances becomes decreased with the-consequent reduction in size of the distilling tower andr further, least utility, and other advantages.
- In the foregoing explanations of the present invention, -there has been shown a process of obtaining SiH4 as the end product. It should however be noted that the same effect as mentioned above can be obtained in the case of taking out SiH2C12 as the end product.
In the trichlorosilane synthesizing vessel in the first step, trichlorosilane i5 prepared from silicon of metallurgical grade as a starting material. Ins-tead of this process, there may be employed a process as shown in Figure 4 wherein silica, carbon and chlorine as starting materials are reac-ted at a high temperature in a silicon tetrachloride synthesizing furnace to produce silicon 1;~Sg~ 6 tetrachloride, and the silicon tetrachloride thus obtained is purified in a low boiling component removal tower B and a high boiling component removal tower C, then introduced into a trichlorosilane synthesizing tower D and converted to trichlorosilane by reduction with hydrogen. This method is advantageous in the case where silane gas is produced in a large amountr since the power consumption is thereby essentially small, and the cost for the operation is low. Here, the synthesis of silicon 1~ tetrachloride is conducted usually at a temperature of from llO0 to 1400C in a reaction system such as a fixed bed system, a transfer bed system or a fluidized bed system. Further, when silicon carbide is added to the starting material as a catalyst in an amount of from l to 10% by weight, the reaction rate is improved. Further, from the viewpoint of the efficiency of energy, the synthesis of trichlorosilane by reduction with hydrogen is advantageously conducted at a molar ratio of SiCl4/H2 within a range of from l : l to l : 2, at a temperature within a range of from 1200 to 1400C.
Now, the present invention will be described in detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by these specific Examples.
Using trichlorosilane (SiHCl3), which was placed in an autoclave (SUS 304) of 500 cc capacity and provided , ~S~7~l6 - 23 ~
with a jacket and an agitator, the disproportionation reaction was conducted in a hermetically sealed condition by varying the reac-tion temperature, and the kind and amount oE the catalyst, as shown in Table 1 below. The quantity of the chlorosilane in the gas phase was quantitatively measured by gas chromatography time-sequentially. The amount of the hydrochloride in each case was 20 mol % relative to the tertiary amine.
The hydrochloride was formed by in-troducin~ the tertiary amine into the autoclave and then blowing HC1 thereinto.
A change in the quantity of SiHCl3 in the gas phase corresponds to its conversion ra-tio, and Table 1 below indicates the time until the concentration of SiHCl3 takes a constant value and the concentrations of SiHC13 and SiC14 at that time. Table 1 shows that -the shorter the time is, the faster is the conversion veloci-ty (i.e.
disproportionation velocity), and the lower the concentration value of SiHCl3 is, the better becomes the conversion. Also, in Table l below, the equilibrated concentration of SiHCl3 obtained by calculation is shown as a reference.
For the purpose of comparison, under the same conditions as in E~ample l above, the dispropor-tionation reactions were carried out by using trimethylamine, 25 triethylamine, tri-n-propylamine, trimethylamine hydrochloride, and triethylamine hydrochloride as the catalysts, at the reaction temperatures of 25C, 50C, :lZS~71ti and 100C, respectlvely~ The results are shown in Table 1 below (experiments No. 20 - No. 30). The catalysts were present as solid substance in the reaction liquid, and the agitator was employed for sufficient dispersion of the catal~sts.
According to the present invention as shown in Table l, the equilibrated conversion was obtained in 38 min.
and 5 min. at the respective reaction temperatures of 25C and 100C in experiments No. 8 and No. 9. In contrast to this, according to comparative experiments No. 20 and No. 22, the equilibrated conversion was not obtained even at the end of 240 min. and lO min., respectiveLy. This diffexence leads to a difference in the production quantity of SiH2Cl2 which amounts to 7 times and 2 times, respectively, when manufacturing SiH2C12 from SiHC13 in the reaction vessels of the same capacity. This proves that the effect to be derived from the present invention is apparently superior.
- ~5 -Table 1 iL~59L7~
, . _ Time lapsed 8iHCl3 con- SiCl4 con- Equilibrated E~cpeIi- ~eac- Quantity Starting until SiHC13 centration centration SiHC14 con-ment Kind of catalyst tion of material concentra- when it when it centration No. temp. catalyst SiHCl3 tion becomes became became (~) (mol~ (mol) constant(min) constant(96) constant t%) (%) _ 1 Tri-n-butylamine50 0.1 1 779. 8 10.3 79. 0 2 Tli-n-pentylamine 50 0. 1 1 7 79. 4 10.5 79.0 3 Tri-n-ha~ylamine50 0. 1 1 679.5 10.3 79. 0 4 Tri-n-heptylamine 50 0.1 1 6 79.3 11.0 79. 0 Tri-n-octylamine50 0. 1 1 679. 4 10. 9 79. 0
6 Tri-n-decylamine50 0. 1 1 679. 4 10.5 79. 0
7 Tri-n-dodecylamine 50 0. 1 1 6 79.5 10.2 79. 0
8 Tri-n-butylamine25 0. 1 1 3880. 2 11.5 80. 0
9 .. 100 0.1 l 276.0 13.6 76.0 .. 150 0.1 1 1.574.5 14.4 74.0 11 Tri-n-octylamine25 0.1 1 25ao. 5 10.5 80.0 12 .. 100 0.1 1 276.2 12.8 76.0 13 .. 150 0.1 1 1.574.5 14.~1 74.0 14 Tri-n-butylamine50 0.04 1 5585. 8 7.1 79. 0 .. 50 0.05 1 3081.0 10.1 79.0 16 .. 50 0.2 1 679.8 10.7 q9.0 17 . Tri-n-octylnmine50 0.04 1 40 84.7 8.1 79. 0 18 .. 50 0.05 1 24 80.5 9.7 79. 0 19 . .......... 50 0.2 1 5 79.0 11,3 79.0 Trimethylamine25 0. 1 1 24095. 6 3.1 80. 0 21 ." 50 0.1 1 60 92.0 5.0 79.0 22 .. 100 0.1 1 10 80.3 10.9 76.0 23 Triethylamine 25 0. 1 1 24097.3 1.5 80. D
24 .. 50 1 0.1 1 60 91.0 5.1 7g.0 ,. 100 0. 1 1 11 80. o 10.7 76. 0 26 Tri-n-propylamine ¦25 0. l 1 210 93. 2 4.2 80. 0 27 ,. 50 0.1 1 55 88.8 7.0 79.0 28 ,. lO0 0.1 1 10 79. 0 10.6 76. 0 29 Trimethylamine 50 0. 1 1 220 87.5 7.3 79. 0 hydrochloride Triethylamine ¦ 50 0. 1 1 250 86. o 8.2 79. 0. hydrochloride .
__ _ __ ~S~'~16 i' EXAMPLE 2: i SiHC13 used as the starting material in Example 1 ;i above was changed to SiH2C12, and the disproportiona-tion reac-tion was conducted under the conditions as shown in Table 2 below, while quantitatively measuring concentration o~ SiH4 in the gas phase by gas chromatography. Table 2 indicates the time when the concentration of SiH4 became constant and the concentration thereof at that time. Also, in Table 2 below, the equilibrated conCentratiQn o~ SiH4 obtained by calculation is shown as a reference.
For the purpose oE comparison, under the same condi-tions as in Example 2 above, the disproportionation reactions were conducted by using triethylamine, tri-n-propylamine and trimethylamine hydrochloride as the catalysts, at reaction temperatures of 25C, 50C, and 100C, respectively. The results are shown in Table 2 below (experiments No. 42 - No. 48). The experiments were carried out by use of the agitator as was the case with the above-mentioned comparative experiments No. 20 -No. 30.
~4~71~ ~
.
.
Table 2 _ Time lapsed SiH4 Experi- K' d f c tal Reaction Quantity Starting until SiH4 concentration Equi]ibrated ment No I ln o a yst temp. of material concentration when it SiH4 catalystsiH2C12 becc~mes con- became concentration (C) tmol)(mol) stant (min) constant (%) (%) 31 Tri-n-butylamine 50 0. 1 1 5 65. 5 66. 0 32 Tri-n-pentylamine 50 0. 1 1 4 66.3 66. 0 33 Tri-n-hexylamine 50 0.1 1 4 65. 9 66. 0 34 Tri-n-heptylamine 50 0.1 1 4 65.9 66. 0 Tri-n-octylamine 50 0.1 1 3.5 66. 2 .66. 0 36 Tri-n-decylamine 50 0.1 1 4 65. 8 66. 0 37 Tri-n-dodecylamine 50 0. 1 1 4 66. 4 66.0 38 Tri-n-butylamine 25 0.1 1 20 72. 5 73.5 39 ,. 100 0.1 1 0.5 S1.0 50.7 Tri-n-octylamine 25 0. l 1 . 18 72.2 73. 5 41 I~ ioo o.l 1 0.5 50.6 50.7 42 Triethylamine 25 0.1 1 79 60.3 73.5 43 ,. 50 0.1 1 23 52.1 66. 0 44 ll 100 0. 1 1 12 39. 9 50.7 Tri-n-propylamine 25 0.1 1 68 68. 4 73.5 46 ,. 50 0.1 1 21 60.5 66.0 47 ll 100 0.1 1 10 45.2 50.7 48 Trimethylamine 50 0.1 1 6S 67. a 66.0 hydrochloride _ lZS'~71~i Experiments were conducted in the same manner as in experiments No. 1 and No. 5 of Example 1 except that the Z
concentration of the hydrochloride was varied by changing 5 the amount of -the introduction of ~Cl. The conditions and the results are shown in Table 3. Experiments No.
49, No. 50, No. 59, No. 60 and No. 67 in Table 3 are comparative examples.
1~5~71~i .
Table 3 _ _ Time lap~ed Equilibrated Hydro- Reaction until SiHC13 SiHC13 SiCl4 SiHC13 Experi- Kind of catalyst chloride temp. concentra- concentra- concentra- concentra-ment content tion become~ tion tion tion (%) (mol ~) tC) (min) (%)t%) (as calculated) 49 Trioctylamine _ 50 12 80.1 11.2 79.0 ~0 ,. l 50 11 79.6 11.0 79.0 51 1! 2 50 7 78. ~ 10.5 79.0 S2 ,. , 5 50 7 79.0 10.8 79.0 53 ,. 10 50 6 78.8 10.4 79.0 5g ,. 20 50 6 79.~ 10.9 79.0 ,. 30 50 6 79.0 10.9 79.0 56 ,. 40 50 6 78.9 11.5 79.0 57 ,. 80 50 6 78.6 11.7 79.0 58 . " . 80 50 6 76.3 11.9 79.0 59 ,. 85 50 6 72.6 14.9 79.0 . 60 Tributylamine _ 50 14 80.2 11.3 79.0 61 ,. 1 50 13 80.1 11.1 79.0 62 ,. 2 50 8 79.6 10.8 79.0 63 ,. 10 50 7 78.3 10.9 79.0 64 ,. 20 50 7 79.8 10.3 79.0 " 30 50 6 78.2 11.9 79.0 66 " 80 50 6 76.g 12.0 79.0 67 . 85 50 6 7~.6 17.0 7~.0 t7~6 As described in the foregoing, the presen-t invention provides a chlorosilane disproportionation catalyst composed essentially of a specific tertiary amine and its hydrochloride, and a method for the disproportionation of a chlorosilane by means of the catalyst. The following eEfects are obtainable by the present invention.
(1) The catalyst of the present invention provides a conversion which is closer to the equilibrated conversion, a-t a temperature of less than 150C in comparison with the conventional catalyst.
(2) When the catalyst of the present inven-tion is used, the equilibrated conversion is reached in a short period of time, which means a high disproportionation velocity, and which makes it possible to reduce the size of the reaction apparatus.
(3) The catalyst according to the present invention is completely soluble in the chlorosilane as the star-ting material, and also has a boiling point of 200C and above. Accordingly, it serves to lower the vapor pressure in the reaction liquid, and advan-tageously contributes to safety in the operation.
(4) The catalyst can be readily separated from the reaction product such as SiH2C12 or SiH4.
(5) Since the reaction system is a uniform liquid phase sys-tem, there is no necessity for agitation and other homogenizing operations. Thus, the transportion and various handling of the catalyst become advan-tageous]y simple.
~5~7~
EXAMPLE 4 ,~
Into the evaporation tank 9, ~ liters of tri-n- ji octylamine was charged, and then 21 li-ters of hydrogen chloride gas was blown into it to prepare a catalyst con-taining 20 mol % of tri-n-octylamine hydrochloride.
Then, the heating medium oil in the jacket was heated and maintained a-t a temperature of 100C. On the other hand, the condenser 3 above the reaction tower was cooled with me-thanol dry ice of -60C. The reboiler 2 at the bottom of the reaction tower was then heated by an electric heater. Trichlorosilane was continuously supplied from the starting material supply conduit 4 into the reaction tower 1 at a flow rate of 4.0 kg/hr. At the same time, -the catalyst in the evaporation tank 9 was circulated to the reaction tower 1 at a flow rate of 1.07 kg/hr by the operation of the catalyst circulation pump 10. The internal pressure of the reaction tower 1 was adjusted by an adjusting valve 5 and maintained at a gauge pressure of 2 kg/cm2. Also, the liquid level of the reboiler 2 was adjusted by an adjusting valve 8 so that the liquid surface was maintained at a constant level, and the reac-tion solution containing the catalyst in the reboiler was withdrawn to the evaporation tank 9. While supplying hydrogen chloride gas to the recovered catalyst at a flow rate of 50 cc/min through the supply line 13, the recovered catalyst was continuously recycled to the reaction tower. The reaction was continuously carried li~S~'7~
~, out for 20 hours while maintaining -the temperature of the . _ .
reboiler 2 at the bottom of the reaction tower at 85C, whereby a low boiling gas was obtained from the top at a J
rate of 180 g/hr. The recovered liquia collected in the 5 collecting tank 7 was analyzed by gas chromatography, and it was Eound that the recovered liquid con-tained ~5 mol %
of monosilane, 8.5 mol % of monochlorosilane and 6.5 mol % of dichlorosilane.
On the other hand, the chlorosilane evaporated from
24 .. 50 1 0.1 1 60 91.0 5.1 7g.0 ,. 100 0. 1 1 11 80. o 10.7 76. 0 26 Tri-n-propylamine ¦25 0. l 1 210 93. 2 4.2 80. 0 27 ,. 50 0.1 1 55 88.8 7.0 79.0 28 ,. lO0 0.1 1 10 79. 0 10.6 76. 0 29 Trimethylamine 50 0. 1 1 220 87.5 7.3 79. 0 hydrochloride Triethylamine ¦ 50 0. 1 1 250 86. o 8.2 79. 0. hydrochloride .
__ _ __ ~S~'~16 i' EXAMPLE 2: i SiHC13 used as the starting material in Example 1 ;i above was changed to SiH2C12, and the disproportiona-tion reac-tion was conducted under the conditions as shown in Table 2 below, while quantitatively measuring concentration o~ SiH4 in the gas phase by gas chromatography. Table 2 indicates the time when the concentration of SiH4 became constant and the concentration thereof at that time. Also, in Table 2 below, the equilibrated conCentratiQn o~ SiH4 obtained by calculation is shown as a reference.
For the purpose oE comparison, under the same condi-tions as in Example 2 above, the disproportionation reactions were conducted by using triethylamine, tri-n-propylamine and trimethylamine hydrochloride as the catalysts, at reaction temperatures of 25C, 50C, and 100C, respectively. The results are shown in Table 2 below (experiments No. 42 - No. 48). The experiments were carried out by use of the agitator as was the case with the above-mentioned comparative experiments No. 20 -No. 30.
~4~71~ ~
.
.
Table 2 _ Time lapsed SiH4 Experi- K' d f c tal Reaction Quantity Starting until SiH4 concentration Equi]ibrated ment No I ln o a yst temp. of material concentration when it SiH4 catalystsiH2C12 becc~mes con- became concentration (C) tmol)(mol) stant (min) constant (%) (%) 31 Tri-n-butylamine 50 0. 1 1 5 65. 5 66. 0 32 Tri-n-pentylamine 50 0. 1 1 4 66.3 66. 0 33 Tri-n-hexylamine 50 0.1 1 4 65. 9 66. 0 34 Tri-n-heptylamine 50 0.1 1 4 65.9 66. 0 Tri-n-octylamine 50 0.1 1 3.5 66. 2 .66. 0 36 Tri-n-decylamine 50 0.1 1 4 65. 8 66. 0 37 Tri-n-dodecylamine 50 0. 1 1 4 66. 4 66.0 38 Tri-n-butylamine 25 0.1 1 20 72. 5 73.5 39 ,. 100 0.1 1 0.5 S1.0 50.7 Tri-n-octylamine 25 0. l 1 . 18 72.2 73. 5 41 I~ ioo o.l 1 0.5 50.6 50.7 42 Triethylamine 25 0.1 1 79 60.3 73.5 43 ,. 50 0.1 1 23 52.1 66. 0 44 ll 100 0. 1 1 12 39. 9 50.7 Tri-n-propylamine 25 0.1 1 68 68. 4 73.5 46 ,. 50 0.1 1 21 60.5 66.0 47 ll 100 0.1 1 10 45.2 50.7 48 Trimethylamine 50 0.1 1 6S 67. a 66.0 hydrochloride _ lZS'~71~i Experiments were conducted in the same manner as in experiments No. 1 and No. 5 of Example 1 except that the Z
concentration of the hydrochloride was varied by changing 5 the amount of -the introduction of ~Cl. The conditions and the results are shown in Table 3. Experiments No.
49, No. 50, No. 59, No. 60 and No. 67 in Table 3 are comparative examples.
1~5~71~i .
Table 3 _ _ Time lap~ed Equilibrated Hydro- Reaction until SiHC13 SiHC13 SiCl4 SiHC13 Experi- Kind of catalyst chloride temp. concentra- concentra- concentra- concentra-ment content tion become~ tion tion tion (%) (mol ~) tC) (min) (%)t%) (as calculated) 49 Trioctylamine _ 50 12 80.1 11.2 79.0 ~0 ,. l 50 11 79.6 11.0 79.0 51 1! 2 50 7 78. ~ 10.5 79.0 S2 ,. , 5 50 7 79.0 10.8 79.0 53 ,. 10 50 6 78.8 10.4 79.0 5g ,. 20 50 6 79.~ 10.9 79.0 ,. 30 50 6 79.0 10.9 79.0 56 ,. 40 50 6 78.9 11.5 79.0 57 ,. 80 50 6 78.6 11.7 79.0 58 . " . 80 50 6 76.3 11.9 79.0 59 ,. 85 50 6 72.6 14.9 79.0 . 60 Tributylamine _ 50 14 80.2 11.3 79.0 61 ,. 1 50 13 80.1 11.1 79.0 62 ,. 2 50 8 79.6 10.8 79.0 63 ,. 10 50 7 78.3 10.9 79.0 64 ,. 20 50 7 79.8 10.3 79.0 " 30 50 6 78.2 11.9 79.0 66 " 80 50 6 76.g 12.0 79.0 67 . 85 50 6 7~.6 17.0 7~.0 t7~6 As described in the foregoing, the presen-t invention provides a chlorosilane disproportionation catalyst composed essentially of a specific tertiary amine and its hydrochloride, and a method for the disproportionation of a chlorosilane by means of the catalyst. The following eEfects are obtainable by the present invention.
(1) The catalyst of the present invention provides a conversion which is closer to the equilibrated conversion, a-t a temperature of less than 150C in comparison with the conventional catalyst.
(2) When the catalyst of the present inven-tion is used, the equilibrated conversion is reached in a short period of time, which means a high disproportionation velocity, and which makes it possible to reduce the size of the reaction apparatus.
(3) The catalyst according to the present invention is completely soluble in the chlorosilane as the star-ting material, and also has a boiling point of 200C and above. Accordingly, it serves to lower the vapor pressure in the reaction liquid, and advan-tageously contributes to safety in the operation.
(4) The catalyst can be readily separated from the reaction product such as SiH2C12 or SiH4.
(5) Since the reaction system is a uniform liquid phase sys-tem, there is no necessity for agitation and other homogenizing operations. Thus, the transportion and various handling of the catalyst become advan-tageous]y simple.
~5~7~
EXAMPLE 4 ,~
Into the evaporation tank 9, ~ liters of tri-n- ji octylamine was charged, and then 21 li-ters of hydrogen chloride gas was blown into it to prepare a catalyst con-taining 20 mol % of tri-n-octylamine hydrochloride.
Then, the heating medium oil in the jacket was heated and maintained a-t a temperature of 100C. On the other hand, the condenser 3 above the reaction tower was cooled with me-thanol dry ice of -60C. The reboiler 2 at the bottom of the reaction tower was then heated by an electric heater. Trichlorosilane was continuously supplied from the starting material supply conduit 4 into the reaction tower 1 at a flow rate of 4.0 kg/hr. At the same time, -the catalyst in the evaporation tank 9 was circulated to the reaction tower 1 at a flow rate of 1.07 kg/hr by the operation of the catalyst circulation pump 10. The internal pressure of the reaction tower 1 was adjusted by an adjusting valve 5 and maintained at a gauge pressure of 2 kg/cm2. Also, the liquid level of the reboiler 2 was adjusted by an adjusting valve 8 so that the liquid surface was maintained at a constant level, and the reac-tion solution containing the catalyst in the reboiler was withdrawn to the evaporation tank 9. While supplying hydrogen chloride gas to the recovered catalyst at a flow rate of 50 cc/min through the supply line 13, the recovered catalyst was continuously recycled to the reaction tower. The reaction was continuously carried li~S~'7~
~, out for 20 hours while maintaining -the temperature of the . _ .
reboiler 2 at the bottom of the reaction tower at 85C, whereby a low boiling gas was obtained from the top at a J
rate of 180 g/hr. The recovered liquia collected in the 5 collecting tank 7 was analyzed by gas chromatography, and it was Eound that the recovered liquid con-tained ~5 mol %
of monosilane, 8.5 mol % of monochlorosilane and 6.5 mol % of dichlorosilane.
On the other hand, the chlorosilane evaporated from
10 the evaporation tank 9 was cooled in the condenser 11 and recovered in the tank 12 at a rate of 3.82 k~/hr. The composition of the recovered liquid was analy~ed by gas chromatography, and it was found that the liquid consisted of 48 mol % of trichlorosilane and 52 mol ~ of 15 silicon tetrachloride.
The operation was conducted in the same manner as in Example 4 except that 2 liters of tri-n-butylamine was charged to the evaporation tank 9 and 38 liters o~
20 hydrogen chloride gas was blown into it to prepare a catalyst containing 20 mol % of tri-n-butylamine hydrochloride, and the catalyst thereby obtained was recycled to the reaction tower 1 at a flow rate of 570 g/
hr. ~s the results, a low boiling gas was obtained from 25 the top of the tower at a rate of 170 g/hr. The recovered liquid consisted of 81.5 mol % of monosilane, 9.5 mol ~ of monochlorosilane, 8.0 mol % of dichloro-silane and 1.0 mol ~ of trichlorosilane. On the other 12S~16 hand,_the chlorosilane mixture evaporated from the evaporation -tank 9 was cooled in the condenser 11, and recovered in the storage tank 12 at a rate of 3.83 kg/hr.
The recovered liquid consisted of 55 mol % of trichlorosilane and 45 mol % of silicon tetrachloride.
The operation was conducted in the same manner as in Example 4 except that the condenser 3 was cooled by circulating a saline of -10C. As the results, a gas mixture comprising 7 mol % of monosilane, 13 mol % of monochlorosilane, 66 mol ~ of dichlorosilane and 14% of tirchlorosilane was obtained at a rate of 950 g/hr from the condenser 3. On the other hand, ~he chlorosilane mixture comprising 43 mol % oE trichlorosilane and 57 mol % of silicon tetrachloride was recovered at a rate of 3.05 kg/hr from the evaporation -tank 9.
The operation was conducted in the same manner as in Example 4 except that instead of hydrogen chloride gas, steam was supplied from the line 16 of Figure 1 at a flow rate of 30 cc/min. The yield of the low boiling gas from the top was 175 g/hr, and the composition of the gas was substantially the same as the one obtained in Example 4.
The operation was conducted in the same manner as in Example 4 except that instead of hydrogen chloride gas, a 35~ hydrochloric acid aqueous solution was supplied from ~2S~
the line 16 in Figure 1 at a flow rate of 40 cc/min, whereby substantially the same results as in Example 7 were obtained~
EX~MPLE 9 The operation was conducted in the same manner as in Example 4 except that hydrogen chloride gas was supplied from the line 15 in Figure l at a flow rate of 50 cc/min, whereby substan-tially the same r~sults as in Example 4 were obtained.
An experimen-t for the production of monosilane was conducted in accordance with the flow chart shown in Figure 3, to demonstrate the production of monosilane by the combination of the step for synthesizing trichloro-sllane from silicon of methallurgical grade, hydrogenchloride, hydrogen and silicon tetrachloride, with a monosilane reaction and distillation process oE Example 4. ~Q ~..~J~ ~ ~
A E~astelloy/reactor ha~ing an internal capacity of 20 liters was used as the trichlorosilane synthesizing furnace 40, and operated at 600C under a pressure of 2 kg/cm G. The conversion of trichlorosilane in this step was 30~. The conditions for the reaction tower 43 and the evaporator 52 were the same as in Example 4.
As the results, the consumption of the starting material silicon of metallurgical grade was about 65 g/
hr under a monosilane production condition of 68 g/hr.
;~5~7~
In or_er to show -the effects of the present invention clearly, the compositions of the silane mixtures around the distillation tower 41 were measured, and the results are shown in Table 4. For the purpose of comparison, comparative experiments were conducted by tlsing the conventional ion exchange resins under the same conditions for the production of monosilane. The temperature of the ion exchange resin bed was 60C. The compositions of the silane mixtures around the distillation -tower 21 are likewise shown in Table 4.
It is apparent from Table 4 that the amount of txeatment in the distillation tower according to the present invention is about 8 kg/hr which is more than 50 less than 14 kg/hr of the comparative example. This means that the apparatus can be made compact and simplified.
- 36~
, .
_ _ __ _ _ _ ~i c~i E c~ _~
CD _ _ _ _ a~ N _ . ~ .
_ _ ~, I _ N j ~ N
~ r~ ,, 1~ ~ I q I 1~ ~ I o ~ ~ ~~
_ C~ C~ _ _ ~
-I '' CD _ O ~ C~ .
_ _ _ _ _ _ _ ~ C~ O _ ~ . ~D
~ o ~ co r- c~ E u~q c~
E~ r- _ _ _ _ _ _ _ C~ ~ C'~ OD ~ ~9 CO
, L-- O CO CO N ~ Il~
~C~ ~ _ oC~,cD CO
_ _ __ _ -I
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XI
~ ~ :
The operation was conducted in the same manner as in Example 4 except that 2 liters of tri-n-butylamine was charged to the evaporation tank 9 and 38 liters o~
20 hydrogen chloride gas was blown into it to prepare a catalyst containing 20 mol % of tri-n-butylamine hydrochloride, and the catalyst thereby obtained was recycled to the reaction tower 1 at a flow rate of 570 g/
hr. ~s the results, a low boiling gas was obtained from 25 the top of the tower at a rate of 170 g/hr. The recovered liquid consisted of 81.5 mol % of monosilane, 9.5 mol ~ of monochlorosilane, 8.0 mol % of dichloro-silane and 1.0 mol ~ of trichlorosilane. On the other 12S~16 hand,_the chlorosilane mixture evaporated from the evaporation -tank 9 was cooled in the condenser 11, and recovered in the storage tank 12 at a rate of 3.83 kg/hr.
The recovered liquid consisted of 55 mol % of trichlorosilane and 45 mol % of silicon tetrachloride.
The operation was conducted in the same manner as in Example 4 except that the condenser 3 was cooled by circulating a saline of -10C. As the results, a gas mixture comprising 7 mol % of monosilane, 13 mol % of monochlorosilane, 66 mol ~ of dichlorosilane and 14% of tirchlorosilane was obtained at a rate of 950 g/hr from the condenser 3. On the other hand, ~he chlorosilane mixture comprising 43 mol % oE trichlorosilane and 57 mol % of silicon tetrachloride was recovered at a rate of 3.05 kg/hr from the evaporation -tank 9.
The operation was conducted in the same manner as in Example 4 except that instead of hydrogen chloride gas, steam was supplied from the line 16 of Figure 1 at a flow rate of 30 cc/min. The yield of the low boiling gas from the top was 175 g/hr, and the composition of the gas was substantially the same as the one obtained in Example 4.
The operation was conducted in the same manner as in Example 4 except that instead of hydrogen chloride gas, a 35~ hydrochloric acid aqueous solution was supplied from ~2S~
the line 16 in Figure 1 at a flow rate of 40 cc/min, whereby substantially the same results as in Example 7 were obtained~
EX~MPLE 9 The operation was conducted in the same manner as in Example 4 except that hydrogen chloride gas was supplied from the line 15 in Figure l at a flow rate of 50 cc/min, whereby substan-tially the same r~sults as in Example 4 were obtained.
An experimen-t for the production of monosilane was conducted in accordance with the flow chart shown in Figure 3, to demonstrate the production of monosilane by the combination of the step for synthesizing trichloro-sllane from silicon of methallurgical grade, hydrogenchloride, hydrogen and silicon tetrachloride, with a monosilane reaction and distillation process oE Example 4. ~Q ~..~J~ ~ ~
A E~astelloy/reactor ha~ing an internal capacity of 20 liters was used as the trichlorosilane synthesizing furnace 40, and operated at 600C under a pressure of 2 kg/cm G. The conversion of trichlorosilane in this step was 30~. The conditions for the reaction tower 43 and the evaporator 52 were the same as in Example 4.
As the results, the consumption of the starting material silicon of metallurgical grade was about 65 g/
hr under a monosilane production condition of 68 g/hr.
;~5~7~
In or_er to show -the effects of the present invention clearly, the compositions of the silane mixtures around the distillation tower 41 were measured, and the results are shown in Table 4. For the purpose of comparison, comparative experiments were conducted by tlsing the conventional ion exchange resins under the same conditions for the production of monosilane. The temperature of the ion exchange resin bed was 60C. The compositions of the silane mixtures around the distillation -tower 21 are likewise shown in Table 4.
It is apparent from Table 4 that the amount of txeatment in the distillation tower according to the present invention is about 8 kg/hr which is more than 50 less than 14 kg/hr of the comparative example. This means that the apparatus can be made compact and simplified.
- 36~
, .
_ _ __ _ _ _ ~i c~i E c~ _~
CD _ _ _ _ a~ N _ . ~ .
_ _ ~, I _ N j ~ N
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_ _ _ _ _ _ _ ~ C~ O _ ~ . ~D
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XI
~ ~ :
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for disproportionating at least one chlorosilane selected from the group consisting of monochlorosi-lane, dichlorosilane and trichlorosilane, comprising: conducting said disproportionation in the presence of a chlorosilane dispro-portionation catalyst comprising (1) a tertiary amine of the for-mula:
!
wherein each R group represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups is at least 12, and (2) a tertiary amine hydrochloride of the formula wherein R is as defined above.
!
wherein each R group represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups is at least 12, and (2) a tertiary amine hydrochloride of the formula wherein R is as defined above.
2. A method for continuously producing monosilane and/or dichlorosilane by the disproportionation of trichlorosi-lane or dichlorosilane, which comprises: (a) supplying the chlorosilane starting material and a chlorosilane disproportiona-tion catalyst comprising a tertiary amine of the formula:
wherein R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups is at least 12, and a tertiary amine hydrochloride of the formula:
wherein R is as defined above, into a reaction tower having a distilling function; (b) obtaining from the top of the tower, a silane compound containing more hydrogen atoms than the chlorosi-lane starting material; (c) withdrawing, from the bottom of the tower, a liquid mixture comprising the catalyst and silane com-pounds containing more chlorine atoms as byproducts; (d) separat-ing the silane compounds and the catalyst in the liquid mixture;
and (e) recycling the separated catalyst to the reaction tower.
wherein R represents an aliphatic hydrocarbon group and the sum of carbon atoms in the three aliphatic hydrocarbon groups is at least 12, and a tertiary amine hydrochloride of the formula:
wherein R is as defined above, into a reaction tower having a distilling function; (b) obtaining from the top of the tower, a silane compound containing more hydrogen atoms than the chlorosi-lane starting material; (c) withdrawing, from the bottom of the tower, a liquid mixture comprising the catalyst and silane com-pounds containing more chlorine atoms as byproducts; (d) separat-ing the silane compounds and the catalyst in the liquid mixture;
and (e) recycling the separated catalyst to the reaction tower.
3. The method according to claim 2, wherein the cat-alyst is present in an amount of from 2 to 50 mol% relative to the chlorosilane starting material.
4. The method according to claim 2, wherein the reac-tion tower is operated at a temperature of from 10° to 300°C
under a gauge pressure of from 0 to 40 kg/cm2.
under a gauge pressure of from 0 to 40 kg/cm2.
5. The method according to claim 2, wherein the chlorosilane starting material is trichlorosilane prepared by reacting metallurgical grade silicon metal, hydrogen, hydrogen chloride and the silicon tetrachloride, followed by distillation.
6. The method according to claim 2, wherein the chlorosilane starting material is trichlorosilane prepared by reacting silica, carbon and chlorine gas thereby forming silicon tetrachloride, condensing the formed silicon tetrachloride gas and subjecting it to distillation to remove low and high boiling components, followed by reduction with hydrogen to convert the silicon tetrachloride to trichlorosilane.
7. The method according to claim 1, wherein the ter-tiary amine catalyst is tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-decy-lamine or tri-n-dodecylamine.
8. The method according to claim 1, wherein the sum of the carbon atoms in all three groups ranges from 12 to 36.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000489782A CA1254716A (en) | 1985-08-30 | 1985-08-30 | Chlorosilane dispropotionation catalyst and method for producing a silane compound by means of the catalyst |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000489782A CA1254716A (en) | 1985-08-30 | 1985-08-30 | Chlorosilane dispropotionation catalyst and method for producing a silane compound by means of the catalyst |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1254716A true CA1254716A (en) | 1989-05-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000489782A Expired CA1254716A (en) | 1985-08-30 | 1985-08-30 | Chlorosilane dispropotionation catalyst and method for producing a silane compound by means of the catalyst |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1254716A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111921480A (en) * | 2020-09-01 | 2020-11-13 | 新疆协鑫新能源材料科技有限公司 | A device and process for regeneration of high boiler auxiliary agent |
-
1985
- 1985-08-30 CA CA000489782A patent/CA1254716A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111921480A (en) * | 2020-09-01 | 2020-11-13 | 新疆协鑫新能源材料科技有限公司 | A device and process for regeneration of high boiler auxiliary agent |
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