KR102831978B1 - Bimetallic Catalyst for Nonoxidative Conversion of Methane and Method of Producing the Same - Google Patents

Abstract

The present invention relates to a heterometal catalyst for non-oxidative direct conversion of methane and a method for producing the same, and more particularly, to a catalyst for non-oxidative direct conversion of methane, which can minimize coke formation by the catalyst surface and maximize methane conversion reactivity by using a highly crystalline catalyst containing iron (Fe) and platinum (Pt) components optimized for the direct conversion reaction of methane in producing hydrocarbons by non-oxidative direct conversion of methane, and a method for producing the same.

Description

Bimetallic catalyst for nonoxidative direct conversion of methane and method of producing the same

The present invention relates to a heterometal catalyst for non-oxidative direct conversion of methane and a method for producing the same, and more specifically, to a catalyst for non-oxidative direct conversion of methane useful for producing hydrocarbons by non-oxidative direct conversion of methane and a method for producing the same.

Recently, efforts have been made steadily to convert methane ( _CH4 ), which can be obtained from natural gas, shale gas, etc., into high value-added products such as transportation fuel or chemical raw materials. Representative examples of high value-added products that can be obtained from methane include light olefins (ethylene, propylene, butylene, etc.), and the MTO (Methanol to Olefins) technology, which produces light olefins via methanol from synthesis gas (H2 + CO) obtained through methane reforming, and the FTO (Fischer-Tropsch to Olefins) technology, which directly produces light olefins from synthesis gas, are known to be the most feasible technologies. However, in the case of technologies that produce high value-added products via synthesis gas, H2 or CO is additionally required to remove O atoms from CO, which results in a decrease in the utilization efficiency of H or C atoms in the overall process.

Therefore, a new technology is required to directly convert methane into high value-added products without going through synthesis gas. In order to directly convert methane into high value-added products, it is necessary to first activate methane by cleaving the C-H bond (434 kJ/mol) that is strongly formed in methane. From this perspective, research has been actively conducted on the oxidative coupling of methane (OCM) technology that activates methane using oxygen. However, in the OCM reaction, the strong reactivity of O ₂ results in the formation of a large amount of thermodynamically stable H ₂ O and CO _{2 ,} which reduces the utilization efficiency of H or C atoms, which is still a problem.

To solve these problems, technology for producing ethylene, aromatic compounds, etc. by direct conversion of methane under anaerobic or anoxic conditions has been developed recently. However, due to the low reactivity of methane, it is being conducted at high temperature and high pressure, and catalyst development is essential. However, according to research results to date, the problem of rapid decrease in catalytic activity due to carbon (coke) deposition on the catalyst under high temperature and high pressure conditions has emerged as a key issue (see Non-Patent Documents 0001 and 0002).

Accordingly, in US Patent Publication No. 2014-0336432, a non-oxidative conversion method of methane by reacting a methane-containing raw material was used, in order to suppress carbon (coke) deposition of the catalyst under high temperature/high pressure conditions, a catalyst doped with a metal element in an amorphous molten material lattice formed by combining at least one of C, N, and O and Si was used, and US Patent Publication No. 2016-0362351 disclosed a non-oxidative coupling method of methane, which applies a catalyst doped with a chemically active metal in an amorphous molten material lattice formed by combining at least one of C, N, and O and at least one of B, Al, Si, Ti, Zr, and Ge.

However, the catalyst disclosed in the above literature simply shows results in which coke formation is suppressed and the catalytic reaction rate is improved compared to a catalyst for non-oxidative direct conversion of methane manufactured by a conventional sol-gel or impregnation method, and a method for manufacturing a catalyst optimized for non-oxidative direct conversion of methane or conditions for manufacturing the catalyst are not presented.

Meanwhile, if the reaction conditions in the non-oxidative conversion reaction of methane are not appropriate, there is a problem that as the conversion rate of methane increases, the selectivity of coke also increases, and the selectivity and production rate of hydrocarbon compounds decrease. Therefore, in order to maximize the high catalytic reaction rate while minimizing coke production, there remains the task of configuring a reactor that includes a catalyst that can additionally cause a radical reaction.

U.S. Patent Publication No. 2014-0336432 (Published on November 13, 2014) U.S. Patent Publication No. 2016-0362351 (Published on December 15, 2016)

X, Guo et al., Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen, Science, 344, 2014, 616 ~ 619 Mann Sakbodin et al., Hydrogen-Permeable Tubular Membrane Reactor: Promoting Conversion and Product Selectivity for Non-Oxidative Activation of Methane over an FeVSiO2 Catalyst, Angew. Chem. 2016, 128, 16383 ~ 16386

The main purpose of the present invention is to solve the above-mentioned problems, and to provide a catalyst for non-oxidative direct conversion of methane and a methane conversion method using the same, which can maximize the catalytic reaction rate by optimizing the active phase and support characteristics of a heterometal catalyst in the non-oxidative direct conversion of methane, while simultaneously suppressing side reactions to minimize coke formation and improving the deactivation rate of the catalyst.

In order to achieve the above object, one embodiment of the present invention provides a method for producing a catalyst for non-oxidative direct conversion of methane, comprising the steps of: (a) impregnating a platinum (Pt) precursor into a catalyst support compound; (b) drying and calcining the impregnated substance; (c) mixing the calcined impregnated substance with fayalite and then pulverizing the same in an inert atmosphere using a ball mill; (d) introducing the pulverized mixture into a reactor and then melting it to obtain a molten substance; and (e) solidifying the obtained molten substance.

In a preferred embodiment of the present invention, step (a) may be characterized by impregnating 0.1 to 2 parts by weight of a platinum (Pt) precursor with respect to 100 parts by weight of a catalyst carrier compound.

In a preferred embodiment of the present invention, the sintering in step (b) may be performed by heating at a heating rate of 1°C/min or more from 300°C to 900°C.

In a preferred embodiment of the present invention, step (c) may be characterized by including 0.1 to 4 parts by weight of fayalite per 100 parts by weight of the catalyst carrier compound.

In a preferred embodiment of the present invention, step (c) may be characterized by grinding using a ball mill at a speed of 100 rpm to 300 rpm for 4 to 18 hours.

In a preferred embodiment of the present invention, the melting in step (d) may be performed by heating at a heating rate of 6°C/min or more to 1,200°C to 2,000°C.

In a preferred embodiment of the present invention, the catalyst carrier compound may be characterized by being at least one selected from the group consisting of silica, alumina, titania, zirconia, and silicon carbide.

In addition, another embodiment of the present invention provides a catalyst for non-oxidative direct conversion of methane, which is manufactured by the method for manufacturing the catalyst for non-oxidative direct conversion of methane, comprises a catalyst carrier including the catalyst carrier compound, and is characterized in that it has a high crystalline structure with a specific surface area of 5 m ² /g or less.

In a preferred embodiment of the present invention, the amount of iron supported may be 0.1 to 2.0 wt% with respect to the total weight of the catalyst.

In a preferred embodiment of the present invention, the amount of platinum (Pt) supported may be 0.1 to 2.0 wt% based on the total weight of the catalyst.

In a preferred embodiment of the present invention, the catalyst carrier may be characterized as being in a molten crystalline state.

According to the present invention, in the non-oxidative direct conversion reaction of methane, the activity for methane can be maximized while simultaneously minimizing coke production, and a high yield for aromatic hydrocarbon products can be provided.

Figure 1 is a schematic diagram of a method for producing a catalyst for non-oxidative direct conversion of methane according to the present invention.
Figure 2 is a flow chart of a method for manufacturing a catalyst for non-oxidative direct conversion of methane according to the present invention.
Figure 3 is a graph showing the correlation between coke selectivity and methane conversion over a catalyst for methane conversion reaction.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

When it is said throughout this specification that a part "includes" a component, this does not exclude other components, but rather includes other components, unless otherwise stated.

In one aspect, the present invention relates to a method for producing a catalyst for non-oxidative direct conversion of methane, comprising the steps of: (a) impregnating a platinum (Pt) precursor into a catalyst support compound; (b) drying and calcining the impregnated substance; (c) mixing the calcined impregnated substance with fayalite and then pulverizing the same in an inert atmosphere using a ball mill; (d) introducing the pulverized mixture into a reactor and then melting it to obtain a molten substance; and (e) solidifying the obtained molten substance.

More specifically, the method for manufacturing a catalyst for non-oxidative direct conversion of methane according to the present invention maximizes the catalytic reaction rate by including a heterometal catalyst, and at the same time increases the uniformity and dispersibility of the catalyst through atomization before the melting step, while including an atomization step and a melting step under specific conditions to prevent the catalyst from being reduced and sintered due to the heat generated during the atomization process, thereby maximizing the catalytic reaction rate into a product while minimizing coke formation, and easily providing a catalyst for non-oxidative direct conversion of methane having stable catalytic performance even during long-term operation.

Hereinafter, a method for manufacturing a catalyst for non-oxidative direct conversion of methane according to the present invention will be described in more detail with reference to the attached drawings.

Figures 1 and 2 are a schematic diagram and a flow chart, respectively, of a method for manufacturing a catalyst for non-oxidative direct conversion of methane according to the present invention.

The method for producing a catalyst for non-oxidative direct conversion of methane according to the present invention first impregnates a platinum (Pt) precursor into a catalyst carrier compound [step (a)].

As an example, step (a) comprises preparing a platinum precursor solution by dissolving a platinum precursor in distilled water, and then dispersing a catalyst carrier compound to prepare an impregnation.

At this time, as a solvent for preparing a platinum precursor solution, a polar organic solvent such as alcohol or acetone can be used instead of distilled water, or a mixed solvent including distilled water and one or more polar organic solvents can be used.

As an example, when preparing a platinum precursor solution using 30 to 60 ml of the above solvent, it is preferable to use a weight of 0.05 to 0.2 g of the platinum precursor.

In addition, the catalyst carrier compound for forming the catalyst carrier may include at least one selected from the group consisting of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), ceria (CeO ₂ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), activated carbon (AC), silicon carbide (SiC), and silicon nitride (SiN), preferably silica, alumina, titania, zirconia, or silicon carbide, and more preferably silica.

In addition, when the catalyst carrier compound is silica, it is specifically preferred to be quartz.

In the manufacturing method according to the present invention, platinum hexachloride (H ₂ PtCl ₆ ), platinum ammonium chloride (Pt(NH ₃ ) ₄ Cl ₂ ) or platinum ammonium nitrate (Pt(NH ₃ ) ₄ (NO ₃ ) ₂ ) can be used as the platinum precursor, and platinum ammonium nitrate (Pt(NH ₃ ) ₄ (NO ₃ ) ₂ ) is preferably used.

Here, 0.1 to 2 parts by weight of a platinum (Pt) precursor may be included with respect to 100 parts by weight of the catalyst carrier compound.

The impregnation concentration of the supported platinum precursor is an important variable in the activity of the catalyst. If the content of the platinum precursor is less than 0.1 parts by weight, the catalytic activity is low, the catalytic reaction rate decreases, and stable catalytic performance cannot be exhibited. If it exceeds 2 parts by weight, the problem occurs that the reactivity is lowered compared to expensive precious metals.

Thereafter, the catalyst carrier compound impregnated with the platinum precursor manufactured in step (a) is dried and then calcined [step (b)].

The above drying process is performed at a temperature of 80 to 200°C for 3 to 10 hours in air or an inert atmosphere using the impregnation prepared in step (a).

Next, the calcination process of the impregnation that has undergone the drying process can be performed by heating in air or an inert atmosphere to a temperature of 350 to 900°C at a heating rate of 1°C/min or more, and through this drying and calcination process, moisture and impurities contained in the catalyst carrier are removed, and thermal durability and catalytic activity are improved.

Next, the impregnated material dried and calcined in step (b) is mixed with fayalite and then pulverized in an inert atmosphere using a ball mill [step (c)].

The above fayalite (Fe2SiO4) is a silicate containing iron components, and can be manufactured using a silicon precursor and an iron precursor, or a commercialized one can be used without limitation.

As an example of the above method for manufacturing fayrite, it can be obtained by dispersing a silicon precursor and an iron precursor in a solvent such as water or alcohol, and performing a sol-gel reaction such as hydrolysis and/or condensation.

At this time, the solvent is not particularly limited, but water, alcohol, benzene, toluene, xylene, and mixtures thereof can be used, and it is preferable to use an amount of the solvent equivalent to 5 to 20 times the weight of the silicon precursor and iron precursor used. If the amount is less than 5 times, the dispersion effect is reduced, and if it is more than 20 times, the gelation process may be delayed.

As the above silicon precursor, gaseous, liquid and solid silicon precursors can be used. The liquid silicon precursor can be tetraethyl silicate, silicon tetrachloride, organic silane, etc., and the solid silicon precursor can be silica, silicon carbide, silicon nitride, etc.

In addition, the iron precursor may include iron chlorides such as FeCl2 and FeCl3; iron oxides such as FeO, Fe2O3 and Fe3O4; iron carbides such as Fe5C2 and Fe3C; iron nitrides such as Fe2N, Fe4N and Fe7N3; iron silicides such as Fe2SiO4 and Fe2O3·SiO2; and iron silicates.

The sol-gel reaction of the reactants in which the above silicon precursor and iron precursor are dissolved can be performed at room temperature to 150°C for 1 to 15 hours. If the reaction temperature is lower than room temperature, the gelation time becomes longer, and if it exceeds 150°C, gelation may be excessive and the structure may collapse.

The reactant thus obtained can be dried and calcined to produce fayalite (Fe2SiO4). To prevent reduction of the reactant, the reactant can be dried at 20 to 80° C. for 1 to 24 hours in an inert atmosphere such as Ar or He, and then calcined at 500 to 1,000° C. for 1 to 5 hours in an inert atmosphere.

If the drying is less than 20°C or 1 hour, the drying efficiency is poor; if it exceeds 80°C or 24 hours, the catalytic performance may be adversely affected; if the calcination is less than 500°C or 1 hour, it is difficult to remove reactive impurities; if it exceeds 5 hours, the catalytic performance may be adversely affected; and if it exceeds 1,000°C, the atomization described later is difficult and the sintering phenomenon may occur.

In addition, fayalite (Fe2SiO4) can be obtained by performing a mechanical synthesis method such as physically mixing an iron precursor such as Fe2O3, Fe and a silicon precursor such as SiO2 and heating them at a high temperature. Thermodynamically, FeO can be stably formed in the Fe-O system at a temperature of 570 ℃ or higher, and this can react with a silicon precursor to form fayalite.

Thereafter, the above-mentioned fairlite is mixed with an impregnation material including the dried and calcined platinum and catalyst carrier in the step (b), and then pulverized using a ball mill in an inert atmosphere such as Ar or He to prevent reduction of the reactants.

With respect to 100 parts by weight of the above catalyst carrier compound, 0.1 to 4 parts by weight of pearlite can be mixed.

At this time, if the amount of fayalite is less than 0.1 parts by weight with respect to 100 parts by weight of the catalyst carrier compound, not only is the active component of the catalyst low, making it difficult to maximize the catalytic reaction rate, but the density of the catalyst is low, making it difficult to exhibit stable catalytic performance; and if it exceeds 4 parts by weight, the particle size of the iron particles, which are the active sites of methane activation, increases and the amount increases, which may cause a problem in that the coke production rate increases.

In addition, as a preferred embodiment, the amount of the pearlite is preferably 150 to 300 parts by weight with respect to 100 parts by weight of the platinum precursor.

In this way, the mixture of fayalite and a platinum-supported catalyst is atomized using a ball mill. There is no particular limitation on the ball mill device used to atomize the mixture of fayalite and a platinum-supported catalyst, and a general ball mill device can be used.

As an example, the impregnated material dried and calcined in step (b) may be mixed with fayalite and then ground using a ball mill in an inert atmosphere at a speed of 100 rpm to 300 rpm for 4 to 18 hours.

The above ball mill is milled at a speed of 100 rpm to 300 rpm for 4 to 18 hours in an inert atmosphere to prevent reduction of fayalite and to increase the atomization and uniform mixing effect. When the proximity of fayalite and the platinum-supported catalyst increases through the ball mill, the uniformity and density of the catalyst increase. If the rotation speed and time of the ball mill are less than 100 rpm or less than 4 hours, respectively, there is a limit to controlling the particle size and the proximity between particles when atomizing fayalite and the platinum-supported catalyst, and if it exceeds 300 rpm or 18 hours, a problem of deactivation of the product due to sintering of the catalyst support and the active metal may occur.

The atomized mixture may have an average diameter of 60 ㎛ or less, preferably 50 nm to 50 ㎛. If the average diameter of the atomized mixture exceeds 60 ㎛, there is a limit to controlling the proximity between the particles when the fayalite and the platinum-supported catalyst are melted, and as a result, problems may occur in selective reduction of iron particles in the fayalite and in controlling the particle size of the iron particles.

Thereafter, the mixture that has been atomized through the ball mill is put into a reactor and then melted to obtain a melt [step (d)], and the obtained melt is solidified [step (e)].

At this time, the reactor can be used without limitation if it is a material that has thermal stability at the melting temperature, and if the height to diameter ratio of the reactor is less than 0.2, it is difficult to uniformly melt the catalyst carrier and the catalytic active component, making it difficult to manufacture a uniform catalyst, and if the height to diameter ratio of the reactor exceeds 3, the reduction rate of the active metal of the catalyst increases when melted, and the uniformity and density of the catalyst particles tend to decrease when the melt is solidified through cooling.

The mixture introduced into the above reactor can be melted at a temperature at which the entire mixture can be melted, and the melting can be performed by heating in air or an inert atmosphere at a temperature of 1,200°C to 2,000°C at a heating rate of 6°C/min or higher, preferably 6°C/min to 15°C/min.

When the melting temperature is less than 1,200°C, it is difficult to melt both the catalyst carrier and the catalytic active component, which may cause problems in producing a uniform catalyst. When it exceeds 2,000°C, the catalyst carrier and the catalytic active component may vaporize and be lost, which may cause problems in producing a uniform catalyst. At this time, the melting time may be a sufficient time to ensure sufficient melting, and may preferably be about 3 to 9 hours.

At this time, the catalyst undergoes a phase transformation according to the melting speed, and as a result, a high-density catalyst with high crystallinity can be manufactured. However, if the melting temperature increase speed is less than 6°C/min, problems may arise in which the reduction of fayalite to metal is promoted and the uniformity and density of the catalyst are lowered.

In addition, after melting, the solidification step can be performed by rapid cooling or natural cooling. The rapid cooling can be performed by gas cooling, water cooling, oil cooling, liquid nitrogen cooling, etc., and preferably, the rapid cooling can be performed in the condition range of 0.2 ℃/s to 150 ℃/s. When the rapid cooling is performed in the above range, the uniformity of the catalyst can be improved by suppressing the unevenness due to the difference in melting points of the active metal and the carrier component.

In the above gas cooling, the gas may be at least one selected from the group consisting of inert gases and air, and in the oil cooling, the oil may be mineral oil, rapeseed oil, silicone oil, etc.

In addition, the catalyst for direct conversion of methane without oxidation of the present invention can further reduce the pore volume of the catalyst by repeatedly performing the melting step and the solidification step described above. At this time, the number of repetitions of the melting step and the solidification step may be 2 or more times, and preferably 2 to 5 times.

The catalyst for direct conversion of methane to non-oxidation manufactured in this manner is uniformly mixed with an inorganic binder, an organic binder, water, etc. to obtain a catalyst mixture for granulation, and this is molded to manufacture a catalyst molded body.

The organic binder may be one used in the art, and is not particularly limited thereto, but it is preferable to use at least one selected from methyl cellulose, ethylene glycol, polyol, food oil, and organic fatty acid. For example, as the organic binder, it is preferable to use hydroxy methyl cellulose or polyvinyl alcohol. In addition, the inorganic binder may be one used in the art, and is not particularly limited thereto, but it is preferable to use at least one selected from solid silica, solid alumina, solid silica-alumina, silica sol, alumina sol, and water glass. For example, as the inorganic binder, it is preferable to use fumed silica, silica solution, boehmite, or alumina solution.

The above catalyst mixture is typically manufactured into a catalyst molded body by coating the catalyst mixture on a catalyst structure such as a honeycomb structure or a monolithic structure, or by directly extruding the catalyst component of the catalyst mixture. At this time, the coating and extrusion of the catalyst mixture can be easily manufactured by a method used in the art, and a detailed description thereof will be omitted.

The above catalyst-shaped body can be charged one or more times according to the shape of the catalyst-shaped body manufactured in the catalyst charging section inside the reactor for non-oxidation direct conversion of methane. The charging method of the above catalyst-shaped body can also be easily charged using a method used in the art.

The present invention, from another aspect, relates to a catalyst for non-oxidative direct conversion of methane, characterized in that it is manufactured by the aforementioned manufacturing method, includes a catalyst carrier comprising a catalyst carrier compound, and has a highly crystalline structure having a specific surface area of 5 m ² /g or less. In this case, iron and platinum components, which are different active metals, are present on the catalyst carrier in the form of nanoparticles, and iron, which is an active material, is dispersed on the carrier in a form in which it is atomic in unit.

That is, the above-mentioned catalyst for non-oxidative direct conversion of methane can exist in a form in which iron, which is a catalytically active component, is doped within a lattice of a platinum-supported catalyst support compound in a crystalline molten state.

At this time, the average diameter of the platinum or iron particles dispersed and supported on the catalyst carrier may be 5 nm, which is preferable because it increases the density of the carrier by controlling the micro-stress of the carrier and reduces the number of defect sites present in the carrier, thereby allowing the methane reaction to proceed smoothly.

For example, the above-described non-oxidative direct conversion catalyst of methane may have a structure in which two C atoms and one Si atom are bonded to an Fe single atom and embedded in a silica base when the catalyst support compound is composed of silica. In this case, the crystal structure of the catalyst support is α-crystobalite, and is characterized in that it is reversibly converted into β-crystobalite when heated to 200°C to 300°C.

The amount of platinum (Pt), which is the above-mentioned catalytically active component, may be 0.1 to 2.0 wt% based on the total weight of the catalyst. If the amount of platinum supported is less than 0.1 wt% based on the total weight of the catalyst, the catalytic activity may be low, thereby lowering the efficiency of the non-oxidative direct conversion of methane. If it exceeds 2.0 wt%, the problem occurs that the reactivity is lowered compared to expensive precious metals.

In addition, the amount of iron, which is the catalytically active component, may be 0.1 to 2.0 wt% based on the total weight of the catalyst. If the amount of iron supported is less than 0.1 wt% based on the total weight of the catalyst, the content of iron that can act as a dopant may be small, thereby lowering the efficiency of the non-oxidative direct conversion of methane. If it exceeds 2.0 wt%, the amount of iron particles, which are active sites for methane activation, may increase, which may cause a problem in that the rate of coke production increases.

In addition, as a preferred embodiment, the content ratio of platinum and iron, which are active components in the catalyst, is preferably 1:1.5 to 1:3.

The catalyst for non-oxidative direct conversion of methane according to the present invention described above produces olefins and aromatic compounds by reacting an inert and/or non-inert gas with methane at high temperature in the presence of a catalyst.

Specifically, the catalyst according to the present invention is formed, the formed catalyst body is placed in the catalyst charging section of a reactor, and then methane, an inert gas, and/or a non-inert gas are introduced.

The methane may be 80 to 100% (v/v), more preferably 90 to 100% (v/v), based on the volume of the total gas introduced into the reactor, and the inert gas and/or non-inert gas may be 20% (v/v) or less, more preferably 10% (v/v) or less, based on the volume of the total gas.

The above inert gas and non-inert gas play a role in stably generating and maintaining a reaction state, and the inert gas may be nitrogen, helium, neon, argon, or krypton, and the non-inert gas may be air, carbon monoxide, hydrogen, carbon dioxide, water, monohydric alcohols (having 1 to 5 carbon atoms), dihydric alcohols (having 2 to 5 carbon atoms), or alkanes (having 2 to 8 carbon atoms), and preferably, the inert gas and non-inert gas may be nitrogen or air.

The above reaction temperature may be 900 ℃ to 1,150 ℃, specifically 1,000 ℃ to 1,100 ℃, and the pressure may be 0.1 bar to 10 bar, preferably 0.1 bar to 5 bar. This is in consideration of the selectivity and yield of hydrocarbons, and has the advantage of maximizing the selectivity of methane to hydrocarbons. That is, under the above conditions, coke production is minimized, so that the pressure drop due to coke production during the reaction and the carbon efficiency due to coke production can be minimized.

If the above reaction temperature is lower than 900°C, the rate of radical production due to methane activation is low, resulting in low energy efficiency. If it exceeds 1150°C, there may be a problem that the residence time of methane in the reactor must be minimized in order to suppress coke production.

Products produced by direct conversion of methane in this way may be hydrocarbons including paraffins, olefins, alkynes, such as ethane, ethylene, acetylene, propylene, butylene, and may include aromatic compounds such as benzene, toluene, xylene, ethylbenzene, and naphthalene.

The method for converting methane according to the present invention has the effect of enabling activation of methane without precise control of reaction conditions, minimizing coke production, and maintaining a stable yield of hydrocarbon compounds even during long-term operation.

Hereinafter, the present invention will be described more specifically through specific examples. The following examples are merely examples to help understand the present invention, and the scope of the present invention is not limited thereto.

Manufacturing Example 1: CRS Catalyst

6 g of quartz, a silicon precursor, was placed in a reactor and melted at 8°C/min for 4 hours up to 1700°C in air to obtain a molten catalyst (CRS) having a highly crystalline cristobalite structure.

Manufacturing Example 2: Fe@CRS Catalyst

Quartz (6 g), which is a silicon precursor, and fayalite (0.056 g and 0.112 g) were ball milled (250 rpm) in an Ar atmosphere for 5 hours, and then the ball-milled mixture was put into a reactor and melted in air at 8 ℃/min for 4 hours up to 1700 ℃ to obtain molten catalysts (0.5Fe@CRS, 1.0Fe@CRS) having iron loadings of 0.5 wt% and 1.0 wt%, respectively.

Manufacturing Example 3-6: Me/Fe@CRS Catalyst

0.296 g of cobalt nitrate hexahydrate, a cobalt precursor, was dissolved in 50 ml of distilled water, and 6 g of quartz, a silicon precursor, was dispersed therein. The mixture was stirred and evaporated at 100 °C for 4 hours and then dried in an oven at 120 °C overnight. Thereafter, the dried impregnation was calcined at 400 °C in an air atmosphere to produce a Co/SiO ₂ catalyst having a loading of 0.5 wt%.

6 g of the manufactured Co/SiO2 catalyst and 0.112 g of fayalite were ball milled (250 rpm) in an Ar atmosphere for 5 hours, and then the ball-milled mixture was put into a reactor and melted in air at 8 ℃/min for 4 hours up to 1700 ℃ to obtain a molten catalyst (0.5Co1.0Fe@CRS) having an iron loading of 1.0 wt% and a cobalt loading of 0.5 wt%. A catalyst was manufactured using the same method.

Next, a catalyst was manufactured under the conditions described in Table 1 below, wherein 0.112 g of fayalite was ball milled (250 rpm) with 6 g of 0.5 wt% Me/SiO ₂ (Me=Ni, Pd, Pt) in an Ar atmosphere for 5 hours, and then the ball-milled mixture was put into a reactor and melted in air at 8 ℃/min for 4 hours up to 1700 ℃ to obtain a molten catalyst (0.5Me1.0Fe@CRS) having an iron loading of 1.0 wt%, another metal loading of 0.5 wt%, and a specific surface area of 2 m ² /g or less.

[Table 1]

[Experimental Example 1]: Methane Non-oxidative Direct Conversion Reaction

Using the catalysts manufactured in the above examples and comparative examples, the non-oxidative direct conversion reaction of methane was performed at atmospheric pressure and 1020 ℃ for 10 hours, and the conversion rate and selectivity were confirmed. For the reaction experiment, a 1/4 inch fixed-bed reactor made of quartz with an internal diameter of 0.4 cm was used. The catalysts manufactured in the examples and comparative examples were ground to an average particle size of 630 ㎛, and 0.6 g of the ground catalyst was fixed to the center of the reactor with quartz wool. A quartz rod was inserted under the catalyst packing layer in the reactor to minimize the residual space. While the reactor temperature was increased to 1020 ℃, He gas was injected at a flow rate of 40 ml/min, and thereafter, the reactant containing methane was injected under the condition of 990 mlg _cat ^-1 hr ^-1 (reactant composition: 90% CH ₄ , 10% Ar) using a mass flow controller. Ar gas was used as an internal standard.

The hydrocarbons of the obtained products were analyzed using GC of Series 6100 of YL Instrument, and the gaseous products were analyzed by a thermal conductivity detector (TCD) connected to a ShinCarbon ST column and a flame ionization detector (FID) detector connected to a Rt-alumina BOND column. H ₂ , CH ₄ , and CO were separated from the ShinCarbon ST column and detected by the TCD, and the conversion rate was calculated from the area of methane compared to the area of Ar, the internal standard. Hydrocarbons in the range of C ₁ to C ₁₀ were separated by the Rt-alumina BOND column and detected by the FID. All gases were quantified using standard samples. The coke selectivity was calculated by [Scoke = 100 - Σproduct selectivity]. The results measured in this way are shown in Table 2.

[Table 2]

As shown in Table 2 above, the CRS catalyst and the Fe@CRS catalyst showed relatively low selectivity for aromatic compounds and high coke selectivity compared to the blank experiment. Therefore, it can be seen that inducing the reaction for C2 product through a gas-phase reaction after initial activation of methane is advantageous in terms of selectivity. Meanwhile, the 0.5Pt-1,0Fe@CRS catalyst prepared in Example 1 showed high methane conversion, high yield of aromatic compounds, and low coke selectivity compared to the Fe@CRS catalyst, confirming that the gas-phase C2 oligomerization reaction can be induced using a heterometal catalyst having an appropriate ratio and composition.

To better demonstrate the effect of the heterometal catalyst, the coke selectivity with respect to the methane conversion in the methane conversion reaction is plotted as shown in Fig. 3 below. As a result, it was confirmed that the addition of the heterometal did not significantly deviate from the correlation between the coke selectivity with respect to the methane conversion in the case of the 0.5Fe@CRS catalyst.

However, in the case of the 0.5Pt-1.0Fe@CRS catalyst, it was observed that the coke selectivity shifted toward a lower side in the correlation between the coke selectivity and the methane conversion on the Fe@CRS catalyst, and it was confirmed that the coke formation was suppressed by inducing the gas-phase oligomerization reaction of the C2 product from the region close to the Blank-CRS region.

[Experimental Example 2]: Raman analysis of the catalyst after direct methane conversion reaction

Raman analysis was performed on the catalyst after the non-oxidative direct conversion reaction of methane, and the results are shown in Table 3 below.

[Table 3]

As shown in Table 3 above, the 0.5Pt-1.0Fe@CRS catalyst, which showed a relatively high methane conversion, exhibited the lowest I _D1 /I _G peak ratio. This shows that disordered coke derived from aromatic compounds was not well generated in the 0.5Pt-1.0Fe@CRS catalyst during the reaction.

Accordingly, it was confirmed that the catalyst for non-oxidative direct conversion of methane according to the present invention can maximize the catalytic reaction rate while minimizing coke production and providing a high yield of aromatic compounds in the production of hydrocarbons.

Although the present invention has been described with reference to the above-described embodiments and the attached drawings, it is possible to construct different embodiments within the concept and scope of the present invention. Accordingly, the scope of the present invention is defined by the appended claims and their equivalents, and is not limited to the specific embodiments described herein.

Claims (11)

(a) a step of impregnating a platinum (Pt) precursor into a catalyst carrier compound;
(b) a step of drying and calcining the impregnated substance;
(c) The calcined impregnation is mixed with fayalite and then used in a ball mill.
Step of grinding in an inert atmosphere;
(d) The above pulverized mixture is put into a reactor and then melted to obtain a molten product.
is the step; and
(e) comprising a step of solidifying the obtained melt,
The step (a) above comprises a platinum (Pt) precursor for 100 parts by weight of a catalyst carrier compound.
A method for producing a catalyst for non-oxidative direct conversion of methane, characterized in that the step (c) comprises 0.1 to 4 parts by weight of fayalite per 100 parts by weight of the catalyst carrier compound.
delete In the first paragraph,
A method for producing a catalyst for non-oxidative direct conversion of methane, characterized in that the calcination in step (b) is performed by heating at a heating rate of 1 ℃/min or more from 300 ℃ to 900 ℃.
delete In the first paragraph,
A method for producing a catalyst for non-oxidative direct conversion of methane, characterized in that the step (c) above comprises grinding using a ball mill at a speed of 100 to 300 rpm for 4 to 18 hours.
In the first paragraph,
A method for producing a catalyst for non-oxidative direct conversion of methane, characterized in that the melting in step (d) is performed by heating at a heating rate of 6 ℃/min or more from 1,200 ℃ to 2,000 ℃.
In the first paragraph,
A method for producing a catalyst for non-oxidative direct conversion of methane, characterized in that the catalyst carrier compound is at least one selected from the group consisting of silica, alumina, titania, zirconia, and silicon carbide.
Manufactured by any one of the manufacturing methods of Article 1, Article 3, Article 5 to Article 7,
A catalyst for non-oxidative direct conversion of methane, comprising a catalyst carrier comprising the above catalyst carrier compound, having a highly crystalline structure having a specific surface area of 5 m ² /g or less, and characterized in that the amount of iron supported is 0.1 to 2.0 wt% with respect to the total weight of the catalyst.
delete In Article 8,
A catalyst for non-oxidative direct conversion of methane, characterized in that the amount of platinum (Pt) supported is 0.1 to 2.0 wt% with respect to the total weight of the catalyst.
In Article 8,
A catalyst for non-oxidative direct conversion of methane, characterized in that the catalyst carrier is in a molten crystalline state.