CN109987594A - A kind of preparation method of potassium dihydrogen phosphate - Google Patents

Abstract

The invention discloses a preparation method of potassium dihydrogen phosphate, which comprises the following steps: (1) preparing a phosphoric acid raw material: putting 0.08-0.15 kg of a sedimentation agent into each ton of wet-process phosphoric acid, and naturally settling to obtain a phosphoric acid raw material; In parts by mass, the settling agent includes 15-30 parts of anionic flocculants and 1-20 parts of nonionic flocculants, the anionic flocculants are anionic polyacrylamide flocculants, and the nonionic flocculants are The flocculant is a non-ionic polyacrylamide flocculant; (2) Preparation of urea phosphate: the phosphoric acid raw material is synthesized with carbonamide, separated and filtered to obtain urea phosphate; (3) Preparation of potassium dihydrogen phosphate: the Urea phosphate reacts with a potassium source to produce potassium dihydrogen phosphate. The preparation method has low production cost, no waste gas, waste water, and waste residue to prepare the potassium dihydrogen phosphate, and the prepared potassium dihydrogen phosphate has high purity and high phosphorus yield.

Description

A kind of preparation method of potassium dihydrogen phosphate

technical field

The present invention relates to the technical field of potassium dihydrogen phosphate, in particular to a preparation method of potassium dihydrogen phosphate.

Background technique

Potassium dihydrogen phosphate has a wide range of uses in industrial and agricultural production. Industrially used as buffer, enhancer, flavoring agent, etc. In agriculture, potassium dihydrogen phosphate is a high-concentration phosphorus and potassium fertilizer, which has obvious effects on increasing crop production and income. Potassium dihydrogen phosphate is also a fully soluble high-efficiency spray fertilizer, which is widely used in spray and dropper systems.

At present, the production methods of potassium dihydrogen phosphate mainly include neutralization method, metathesis method, solvent extraction method, etc. The domestic process of producing potassium dihydrogen phosphate by solvent extraction is as follows: wet phosphoric acid desulfurization and defluorination, and then extraction and purification with organic solvent, and the extracted acid residue produced in the purification process is used to produce fertilizer; the purified phosphoric acid is added with potassium chloride The aqueous solution and the organic solvent are extracted and separated. The aqueous solution is a solution of potassium dihydrogen phosphate, and the potassium dihydrogen phosphate product is obtained after concentration and drying. NPK ternary compound fertilizer was obtained. This method requires the use of two organic solvents, has a two-stage extraction process, and has high operating costs.

In addition, after the purified acid is obtained by the wet phosphoric acid solvent extraction method, the ammonium dihydrogen phosphate solution is obtained by neutralization with ammonia, and then potassium chloride is added to carry out the metathesis reaction. The purity of the potassium dihydrogen phosphate product obtained by this method is not high, but secondary crystallization is required.

It can be seen from this that the existing technologies all have incomplete impurity removal, the mother liquor cannot be reasonably utilized, and the extraction agent consumes a lot, which makes the phosphorus yield on the low side and the production cost increase. These are the problems to be solved in the art.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for preparing potassium dihydrogen phosphate with low production cost and no discharge of waste gas, waste water and waste residue, and the prepared potassium dihydrogen phosphate has high purity and high phosphorus yield.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a preparation method of potassium dihydrogen phosphate, comprising the following steps:

(1) make phosphoric acid raw material: put 0.08-0.15kg sedimentation agent into every ton of wet-process phosphoric acid, and settle naturally to obtain phosphoric acid raw material; in parts by mass, the sedimentation agent includes 15-30 parts of anionic flocculants and 1-20 parts of a nonionic flocculant, the anionic flocculant is an anionic polyacrylamide flocculant, and the nonionic flocculant is a nonionic polyacrylamide flocculant;

(2) urea phosphate is prepared; the phosphoric acid raw material and carbonamide are subjected to synthesis reaction, separation and filtration to obtain urea phosphate;

(3) Preparation of potassium dihydrogen phosphate: the urea phosphate reacts with a potassium source to obtain potassium dihydrogen phosphate.

The anionic flocculant and the nonionic flocculant used in the present invention are easy to buy and simple to prepare; the settling time of the concentrated wet-process phosphoric acid can be greatly shortened with a small amount of the settling agent. Anionic flocculants and non-ionic flocculants can effectively reduce the content of cations such as Al ³⁺ , Fe ³⁺ , Ca ²⁺ , Mg ²⁺ , Si ⁴⁺ , etc.

Preferably, in step (1), in terms of parts by mass, the sedimentation agent further includes 1-20 parts of an adsorbent.

Preferably, the adsorbent is one or more of diatomite, bentonite, activated carbon and molecular sieve.

Preferably, in step (1), in parts by mass, the sedimentation agent further includes 5-20 parts of a defluorination agent. The fluorine remover can effectively reduce the fluorine content.

Preferably, the fluorine removing agent is one or more of sodium chloride, sodium hydroxide, sodium carbonate, calcium oxide, calcium hydroxide, potassium hydroxide and potassium carbonate.

Preferably, in step (1), the anionic flocculant and the non-ionic flocculant are stirred and mixed at 60-70° C., and allowed to stand to obtain the sedimentation agent;

Preferably, the stirring rate is 100-180r/min, and the stirring time is 8-20min;

Preferably, the standing time is 10-35min.

Preferably, in step (2), the molar ratio of the carbonamide to the phosphoric acid raw material is, carbonic acid amide: phosphoric acid raw material=0.6-0.85;

Preferably, in step (2), the reaction temperature of the synthesis reaction is 50-75°C;

Preferably, in step (2), the reaction time of the synthesis reaction is 50-110 min.

Preferably, in step (3), the urea phosphate and potassium source are mixed at 50-75°C, stirred, cooled to a temperature ≤ 50°C, cooled, crystallized to obtain crystals, and the crystals are centrifuged to obtain The filter cake is dried to obtain the described potassium dihydrogen phosphate;

Preferably, the stirring time is 30-80 min.

Preferably, in step (3), the potassium source is potassium hydroxide, and the mol ratio of the urea phosphate to potassium hydroxide is, urea phosphate: potassium hydroxide=(1-1.2): 1;

Preferably, in step (3), the potassium source is potassium carbonate, and the molar ratio of the urea phosphate to potassium carbonate is urea phosphate:potassium carbonate=(2-2.05):1.

Preferably, in step (1), the wet-process phosphoric acid concentration is 15%-75%;

Preferably, in step (1), the natural sedimentation time is 8-12 hours.

The carbon amide used in the present invention is urea (CO(NH ₂ ) ₂ ), which has an amide structure, so it has the general chemical properties of an amide. Since there are two amino groups that are directly connected to the carbonyl group, they affect each other, so that the carbon amide and the carbonyl group are directly connected to each other. General amides are different, but show some special properties. In the carbonamide molecule, the unshared electron pairs on the two nitrogen atoms are conjugated with the carbonyl π electrons, so compared with the amide, the electron cloud density on the nitrogen atom decreases less, and the binding ability with protons is stronger. , so the basicity of carbonamide is slightly stronger than that of amide, and it can produce salt with strong acid. Since the resulting salt is crystalline, slightly soluble in water and insoluble in acid, the carbonamide can be separated by using this property.

The product of carbonamide and wet-process phosphoric acid is phosphate urea CO(NH ₂ ) _2. H ₃ PO ₄ , which has certain chemical properties and can form potassium dihydrogen phosphate product with higher purity with potassium hydroxide or potassium carbonate.

Compared with the prior art, the present invention has the advantages of short process route, low energy consumption, stable product quality, low production cost, convenient operation and safe production. No waste residue is produced in the preparation process, the solid product in the step (3) is potassium dihydrogen phosphate, and the liquid product is a slurry containing carbonamide, wherein the carbonamide can be recovered and recycled, which realizes clean production and makes the whole production process. Environmentally friendly, clean and pollution-free, no waste gas, waste water and waste residue discharge. In the present invention, the wet-process phosphoric acid is pretreated with a precipitation agent, which can obviously shorten the settling time of the wet-process phosphoric acid, effectively reduce the content of cations such as Al ³⁺ , Fe ³⁺ , Ca ²⁺ , Mg ²⁺ , Si ⁴⁺ , etc., so that the production The concentrated wet-process phosphoric acid comes out with a clear and bright texture and low impurity content. The purity of potassium dihydrogen phosphate prepared by the invention can reach more than 99%.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments.

Example 1

(1) Preparation of phosphoric acid raw material: put 0.08 kg of sedimentation agent into the wet-process phosphoric acid with a concentration of 16% per ton, and settle naturally for 10 hours to obtain the phosphoric acid raw material. In parts by mass, the settling agent includes 15 parts of anionic polyacrylamide flocculant and 8 parts of non-ionic polyacrylamide flocculant; the preparation process of the settling agent is: mixing anionic polyacrylamide flocculant and nonionic polyacrylamide flocculant Type polyacrylamide flocculant was stirred at 60°C for 20min, the stirring rate was 100r/min, and the product was left to stand for 15min. The product was a sedimentation agent.

(2) Preparation of urea phosphate: the raw material of phosphoric acid and carbonamide are subjected to a synthesis reaction at 50° C., the reaction is 110 min, the molar ratio of carbonamide to the raw material of phosphoric acid is, carbonamide: raw material of phosphoric acid=0.6, separation and filtration to obtain urea phosphate ;

(3) prepare potassium dihydrogen phosphate: the mol ratio is urea phosphate: urea phosphate of potassium hydroxide=1:1 and potassium hydroxide are mixed at 50 ℃, stirred 30min; After the reaction finishes, be cooled to-15 ℃, cooling Crystallization, after the crystals are separated out, put them into a centrifuge for centrifugation, the filtrate is a slurry containing carbonamide, and the carbonamide is recovered. The filter cake is a potassium dihydrogen phosphate product, and the product quality reaches the first-class standard of industrial-grade potassium dihydrogen phosphate. , package after drying. After calculation, the yield of the product of this example, potassium dihydrogen phosphate, is 96.2%, and the purity is 99.3%.

Example 2

(1) Preparation of phosphoric acid raw material: put 0.08 kg of sedimentation agent into the wet-process phosphoric acid with a concentration of 16% per ton, and settle naturally for 10 hours to obtain the phosphoric acid raw material. In parts by mass, the sedimentation agent includes 15 parts of anionic polyacrylamide flocculant, 8 parts of non-ionic polyacrylamide flocculant, 1 part of adsorbent diatomaceous earth, and 5 parts of fluorine scavenger sodium chloride; sedimentation The preparation process of the agent is as follows: the anionic polyacrylamide flocculant, the non-ionic polyacrylamide flocculant, the adsorbent and the defluorination agent are stirred at 65°C for 15min, the stirring speed is 120r/min, and the product is left standing for 20min. as a sedimentation agent.

(2) Preparation of urea phosphate: the raw material of phosphoric acid and carbonamide are subjected to a synthesis reaction at 55° C., the reaction is 90 min, and the molar ratio of carbonamide to the raw material of phosphoric acid is, carbonamide: raw material of phosphoric acid=0.7, separation and filtration to obtain urea phosphate ;

(3) prepare potassium dihydrogen phosphate: the mol ratio is urea phosphate: potassium hydroxide=1.2:1, urea phosphate and potassium hydroxide are mixed at 50 ℃, stirred 30min; Crystallization, after the crystals are separated out, put them into a centrifuge for centrifugation, the filtrate is a slurry containing carbonamide, and the carbonamide is recovered. The filter cake is a potassium dihydrogen phosphate product, and the product quality reaches the first-class standard of industrial-grade potassium dihydrogen phosphate. , package after drying. After calculation, the yield of the product potassium dihydrogen phosphate in this example is 96.5%, and the purity is 99.5%.

Example 3

(1) Preparation of phosphoric acid raw material: put 0.1 kg of sedimentation agent into the wet-process phosphoric acid with a concentration of 30% per ton, and settle for 8 hours naturally to obtain the phosphoric acid raw material. In parts by mass, the settling agent includes 20 parts of anionic polyacrylamide flocculant and 15 parts of non-ionic polyacrylamide flocculant; the preparation process of the settling agent is as follows: combining anionic polyacrylamide flocculant, nonionic polyacrylamide flocculant Type polyacrylamide flocculant was stirred at 65°C for 15min, the stirring rate was 120r/min, and the product was allowed to stand for 20min, and the product was a settling agent.

(2) Preparation of phosphoric acid urea: the phosphoric acid raw material and carbonamide are subjected to a synthesis reaction at 60 DEG C, and the reaction is 100 min. The molar ratio of carbonamide and phosphoric acid raw material is, carbonic acid amide: phosphoric acid raw material=0.8, separate, filter, and obtain phosphoric acid urea ;

(3) prepare potassium dihydrogen phosphate: the mol ratio is urea phosphate: the urea phosphate of potassium carbonate=2:1 is mixed with potassium carbonate at 60 ℃, stirred 50min; After precipitation, put it into a centrifuge for centrifugal separation, the filtrate is a slurry containing carbonamide, and the carbonamide is recovered. The filter cake is a potassium dihydrogen phosphate product, and the product quality reaches the first-class standard of industrial-grade potassium dihydrogen phosphate. After drying Package. After calculation, the yield of the product of this example, potassium dihydrogen phosphate, is 96.8%, and the purity is 99.7%.

Example 4

(1) Preparation of phosphoric acid raw material: put 0.12 kg of sedimentation agent into the wet-process phosphoric acid with a concentration of 60% per ton, and naturally settle for 12 hours to obtain the phosphoric acid raw material. In parts by mass, the settling agent includes 25 parts of anionic polyacrylamide flocculant, 15 parts of non-ionic polyacrylamide flocculant, 18 parts of activated carbon, and 20 parts of potassium carbonate; the preparation process of the settling agent is: Type polyacrylamide flocculant, non-ionic polyacrylamide flocculant, adsorbent, and defluorinating agent were stirred at 70 °C for 8 minutes, the stirring rate was 180 r/min, and the product was allowed to stand for 30 minutes, and the product was a settling agent.

(2) Preparation of urea phosphoric acid: the raw material of phosphoric acid and carbonamide are subjected to a synthesis reaction at 70° C. for 60 min, and the molar ratio of carbonamide to the raw material of phosphoric acid is, carbonamide: raw material of phosphoric acid=0.8, separation and filtration to obtain urea phosphate ;

(3) prepare potassium dihydrogen phosphate: the mol ratio is urea phosphate: the urea phosphate of potassium carbonate=2.05:1 and potassium carbonate are mixed at 70 ℃, stirred 30min; After the crystals are separated out, put them into a centrifuge for centrifugal separation. The filtrate is a slurry containing carbonamide, and the carbonamide is recovered. The filter cake is a potassium dihydrogen phosphate product. The product quality reaches the first-class standard of industrial-grade potassium dihydrogen phosphate. after packing. After calculation, the yield of the product of this example, potassium dihydrogen phosphate, is 96.75%, and the purity is 99.73%.

Example 5

(1) Preparation of phosphoric acid raw material: put 0.15 kg of sedimentation agent into the wet-process phosphoric acid with a concentration of 75% per ton, and settle naturally for 12 hours to obtain the phosphoric acid raw material. In parts by mass, the sedimentation agent includes 30 parts of anionic polyacrylamide flocculant and 1 part of non-ionic polyacrylamide flocculant; the preparation process of the sedimentation agent is as follows: Type polyacrylamide flocculant was stirred at 70°C for 8min, the stirring rate was 180r/min, and the product was allowed to stand for 30min, and the product was a settling agent.

(2) Preparation of urea phosphate: the raw material of phosphoric acid and carbonamide are subjected to a synthesis reaction at 75°C, and the reaction is carried out for 50 min. The molar ratio of carbonamide to the raw material of phosphoric acid is, carbonamide: raw material of phosphoric acid=0.85, separation and filtration to obtain urea phosphate ;

(3) prepare potassium dihydrogen phosphate: the mol ratio is urea phosphate: the urea phosphate of potassium carbonate=2.05:1 and potassium carbonate are mixed at 70 ℃, stirred 30min; After the crystals are separated out, put them into a centrifuge for centrifugation. The filtrate is a slurry containing carbonamide, and the carbonamide is recovered. The filter cake is a potassium dihydrogen phosphate product, and the product quality reaches the first-class standard of industrial-grade potassium dihydrogen phosphate. after packing. After calculation, the yield of the product of this example, potassium dihydrogen phosphate, is 96.57%, and the purity is 99.85%.

Example 6

(1) Preparation of phosphoric acid raw material: put 0.15 kg of sedimentation agent into the wet-process phosphoric acid with a concentration of 75% per ton, and settle naturally for 12 hours to obtain the phosphoric acid raw material. In parts by mass, the settling agent includes 30 parts of anionic polyacrylamide flocculant, 1 part of non-ionic polyacrylamide flocculant, 20 parts of bentonite, and 5 parts of calcium hydroxide; the preparation process of the settling agent is: Anionic polyacrylamide flocculant, non-ionic polyacrylamide flocculant, adsorbent and fluorine removal agent were stirred at 70°C for 8 minutes, the stirring rate was 180r/min, and the product was settling agent after standing for 30 minutes.

(2) Preparation of urea phosphate: the raw material of phosphoric acid and carbonamide are subjected to a synthesis reaction at 75°C, and the reaction is carried out for 50 min. The molar ratio of carbonamide to the raw material of phosphoric acid is, carbonamide: raw material of phosphoric acid=0.85, separation and filtration to obtain urea phosphate ;

(3) prepare potassium dihydrogen phosphate: the mol ratio is urea phosphate: potassium hydroxide=1.2:1, urea phosphate and potassium hydroxide are mixed at 70 ℃, stirred 30min; After the reaction finishes, be cooled to -20 ℃, cooling Crystallization, after the crystals are separated out, put them into a centrifuge for centrifugation, the filtrate is a slurry containing carbonamide, and the carbonamide is recovered. The filter cake is a potassium dihydrogen phosphate product, and the product quality reaches the first-class standard of industrial-grade potassium dihydrogen phosphate. , package after drying. After calculation, the yield of the product of this example, potassium dihydrogen phosphate, is 96.96%, and the purity is 99.92%.

The above contents are only preferred embodiments of the present invention. For those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific embodiments and application scope. limits.

Claims (10)

1. a preparation method of potassium dihydrogen phosphate, is characterized in that, comprises the steps: (1) Preparation of phosphoric acid raw materials: put 0.08-0.15kg of sedimentation agent into each ton of wet-process phosphoric acid, and settle naturally to obtain phosphoric acid raw materials; in parts by mass, the sedimentation agent includes 15-30 parts of anionic flocculants and 1-20 parts of a nonionic flocculant, the anionic flocculant is an anionic polyacrylamide flocculant, and the nonionic flocculant is a nonionic polyacrylamide flocculant; (2) Preparation of urea phosphate: the phosphoric acid raw material is synthesized with carbonamide, separated and filtered to obtain urea phosphate; (3) Preparation of potassium dihydrogen phosphate: the urea phosphate reacts with a potassium source to prepare potassium dihydrogen phosphate. 2 . The preparation method according to claim 1 , wherein in step (1), in terms of parts by mass, the sedimentation agent further comprises 1-20 parts of an adsorbent. 3 . 3. The preparation method according to claim 2, wherein the adsorbent is one or more of diatomite, bentonite, activated carbon and molecular sieve. 4. The preparation method according to claim 1 or 2, characterized in that: in step (1), in terms of parts by mass, the sedimentation agent further comprises 5-20 parts of a defluorination agent. 5. preparation method according to claim 4 is characterized in that: described fluorine removing agent is a kind of in sodium chloride, sodium hydroxide, sodium carbonate, calcium oxide, calcium hydroxide, potassium hydroxide, potassium carbonate or more. 6 . The preparation method according to claim 1 , wherein in step (1), the anionic flocculant and the nonionic flocculant are stirred and mixed at 60-70° C., and left to stand to obtain the obtained 6 . the settling agent; Preferably, the stirring rate is 100-180r/min, and the stirring time is 8-20min; Preferably, the standing time is 10-35min. 7. The preparation method according to claim 1, characterized in that: in step (2), the molar ratio of the carbonamide to the phosphoric acid raw material is, carbonic acid amide: phosphoric acid raw material=0.6-0.85; Preferably, in step (2), the reaction temperature of the synthesis reaction is 50-75°C; Preferably, in step (2), the reaction time of the synthesis reaction is 50-110 min. The preparation method according to claim 1, characterized in that: in step (3), the urea phosphate and potassium source are mixed at 50-75°C, stirred, cooled to a temperature of ≤50°C, cooled, and crystallized , to obtain crystals, the crystals are centrifuged, and the obtained filter cake is dried to obtain the described potassium dihydrogen phosphate; Preferably, the stirring time is 30-80 min. 9. preparation method according to claim 1 is characterized in that: in step (3), described potassium source is potassium hydroxide, and the mol ratio of described urea phosphate and potassium hydroxide is, urea phosphate: potassium hydroxide =(1-1.2):1; Preferably, in step (3), the potassium source is potassium carbonate, and the molar ratio of the urea phosphate to potassium carbonate is urea phosphate:potassium carbonate=(2-2.05):1. 10. The preparation method according to claim 1, characterized in that: in step (1), the wet-process phosphoric acid concentration is 15%-75%; Preferably, in step (1), the natural sedimentation time is 8-12 hours.