CN113501532A

CN113501532A - Synthesis method of potassium thiocyanate

Info

Publication number: CN113501532A
Application number: CN202110840425.3A
Authority: CN
Inventors: 何斌; 陈虎; 艾甜碧; 许慧娟
Original assignee: Anhui Yingruiqi Biotechnology Co ltd
Current assignee: Anhui Yingruiqi Biotechnology Co ltd
Priority date: 2021-07-24
Filing date: 2021-07-24
Publication date: 2021-10-15

Abstract

A method for synthesizing potassium thiocyanate comprises the following steps: taking ammonium thiocyanate and potassium hydroxide with a molar ratio of 1:1 as raw materials, adding a water-carrying organic solvent, wherein 3-5mL of the organic solvent is added into every 1g of the raw materials, the water-carrying organic solvent is one of benzene, toluene, xylene, n-butanol, dichloroethane and ethyl acetate, removing generated water through heating reflux, directly filtering after cooling crystallization, drying the crude product to obtain the finished product of potassium thiocyanate, and directly returning the obtained organic filtrate for application, wherein the crude product drying mode is one of blast drying, vacuum double-cone drying and positive-air rake type. The potassium thiocyanate prepared by the method has high purity, and complicated procedures such as activated carbon decoloration and impurity removal are not needed, so that the operation links are greatly reduced, and a large amount of energy consumption is saved.

Description

Synthesis method of potassium thiocyanate

Technical Field

The invention relates to a method for synthesizing potassium thiocyanate.

Background

The application range of potassium thiocyanate (KSCN) is very wide. The compound is mainly used for synthetic resin, pesticides, bactericides, mustard oil, thiourea, medicaments and the like, can also be used as a chemical reagent, is a common indicator of ferric ions, and generates a red flocculent complex after being added; the reagent is also used for preparing a thiocyanate solution, detecting ferric ions, copper and silver, urine test, a tungsten color developing agent and an indicator of titanium with legal capacity; can be used as refrigerant and photographic thickening agent.

The first is potassium cyanide (KCN) sulfur synthesis process, which includes the reaction of KCN and sulfur to produce potassium thiocyanate, and the subsequent impurity removal, decolorizing, filtering, evaporation and crystallization to obtain the product. The process has the advantages of high product purity, good product quality and stable product quality. The disadvantage is that the highly toxic chemical KCN is used, and has strict restriction system in purchase, transportation and use. The second method is an arsenic-alkali by-product method, wherein arsenic trioxide is used as a catalyst, potassium carbonate is used as an absorbent, waste liquid from oxidative desulfurization and decyanation is used as a raw material, and the potassium thiocyanate is obtained by purification in a mode of multiple concentration and fractional crystallization or an organic solvent recrystallization method. The process has the advantages of cheap and easily available raw materials and low cost. The defects are that the produced product has poor quality and low purity, can not be exported and can only be sold as a low-grade product. The third method is an ammonium thiocyanate conversion method, which adopts ammonium thiocyanate and potassium hydroxide as raw materials and obtains the product after impurity removal, decoloration, filtration, evaporation and crystallization. The process has the advantages of simple production process, easy operation, great influence of raw material purity and high raw material cost.

Among the several methods reported in the prior art, the ammonium thiocyanate method is applied by more manufacturers, but the procedures are relatively complicated, the product quality is not high, and generally the content is 95-99%. If high-quality potassium thiocyanate (more than 99.7%) is to be obtained, firstly, the requirements on raw materials are extremely strict, namely, the sodium thiocyanate is more than 99% and the potassium hydroxide is more than 95% (the potassium hydroxide of some domestic manufacturers is unqualified after being used, and the requirement on the initial raw material potassium chloride is higher). Or refining (dissolving, decolorizing, and crystallizing) with 99% potassium thiocyanate. In summary, high quality potassium thiocyanate contents of > 99.7% have been rarely reported.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for synthesizing potassium thiocyanate, the potassium thiocyanate prepared by the method has high purity, and complicated procedures such as activated carbon decoloration and impurity removal are not needed, so that the operation links are greatly reduced, and a large amount of energy consumption is saved.

In order to solve the technical problem, the invention provides a method for synthesizing potassium thiocyanate, which comprises the following steps: taking ammonium thiocyanate and potassium hydroxide with a molar ratio of 1:1 as raw materials, adding a water-carrying organic solvent, wherein 3-5mL of the organic solvent is added into every 1g of the raw materials, the water-carrying organic solvent is one of benzene, toluene, xylene, n-butanol, dichloroethane and ethyl acetate, removing generated water through heating reflux, directly filtering after cooling crystallization, drying the crude product to obtain the finished product of potassium thiocyanate, and directly returning the obtained organic filtrate for application, wherein the crude product drying mode is one of blast drying, vacuum double-cone drying and positive-air rake type.

Preferably, the organic solvent with water is toluene.

Preferably, the crude product drying mode is a vacuum double-cone mode.

The invention has the advantages that: the potassium thiocyanate prepared by the method has high quality (the content is more than 99.7 percent), and complicated procedures such as activated carbon decoloration, impurity removal and the like are not needed, so that the operation links are greatly reduced, and a large amount of energy consumption is saved.

Detailed Description

The first embodiment is as follows:

adding 270mL of toluene into a 500mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 62.344g (90% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 4h until no new water is separated from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 96.208g of finished product potassium thiocyanate with the yield of 99%. The appearance is white crystal with 99.73% content, no ammonium salt, no potassium hydroxide, 6.8 pH value and 0.003 sulfate. The product quality far exceeds the superior product (99.0%) of the national index. 194.444g of ammonia water with the content of 18 percent is co-produced.

The water in the water separator and the ammonia water sprayed and absorbed by the tail gas water are combined to form clean ammonia water with the content of about 20%, and the ammonia water can be used or sold by other projects, so that real zero emission and circular economy are realized.

Example two:

adding 270mL of dimethylbenzene into a 500mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 62.344g (90% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 4h until no new water is separated from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 95.236g of finished product potassium thiocyanate with the yield of 98%. The appearance is white crystal with 99.3% content, no ammonium salt, 7.3 pH value, no potassium hydroxide and 0.02% sulfate. The product quality far exceeds the superior product (99.0%) of the national index. 175g of ammonia water with the content of 20 percent is produced.

Example three:

adding 240mL of dichloroethane into a 500mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 62.344g (90% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 6 hours until no new water is separated from a water separator, cooling a reaction system to 30 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 92.321g of finished product potassium thiocyanate with the yield of 95%. The appearance character is white crystal, the content is 99.1 percent, the ammonium salt is 0.02 percent, the potassium hydroxide is not detected, the pH value is 7.1, and the sulfate is 0.02 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example four:

adding 240mL of n-butanol into a 500mL reaction bottle, adding 79.291g of ammonium thiocyanate (96% in content, 1.0mol) under stirring, adding 62.344g of potassium hydroxide (90% in content, 1.0mol), heating and refluxing for about 6 hours until no new water is separated out from a water separator, cooling the reaction system to 5 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 75.800g of finished product potassium thiocyanate with the yield of 78%. The appearance of the product is white powder, the content of the product is 99.8 percent, ammonium salt is not detected, potassium hydroxide is not detected, the pH value is 6.8, and sulfate is 0.001 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example five:

adding 240mL of ethyl acetate into a 500mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 62.344g (90% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 6 hours until no new water is separated from a water separator, cooling a reaction system to 30 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 85.518g of finished product potassium thiocyanate with the yield of 88%. The appearance of the product is white powder, the content of the product is 99.6 percent, ammonium salt is not detected, potassium hydroxide is not detected, the pH value is 6.6, and sulfate is 0.01 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example six:

adding toluene as a solvent (about 238 mL) into a 500mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate, 62.344g (90% content, 1.0mol) of potassium hydroxide under the stirring condition, heating and refluxing for about 4h until no new water is separated from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying the filtrate, and performing vacuum drying on a filter cake to obtain 94.264g of finished product potassium thiocyanate with the yield of 97%. The appearance character is white crystal, the content is 99.8 percent, ammonium salt is not detected, potassium hydroxide is not detected, the pH value is 6.6, and sulfate is 0.015 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example seven:

adding 450mL of toluene into a 1000mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 62.344g (90% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 4h until no new water is separated from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 93.293g of finished product potassium thiocyanate with the yield of 96%. The appearance is white powder with the content of 99.6 percent, no ammonium salt is detected, the pH value is 6.8, and the sulfate is 0.002 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example eight:

adding 270mL of toluene into a 1000mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 59.063g (95% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 4h until no new water is separated from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 93.293g of finished product potassium thiocyanate with the yield of 96%. The appearance is white powder with the content of 99.6 percent, no ammonium salt is detected, the pH value is 6.8, and the sulfate is 0.002 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example nine:

adding 270mL of toluene into a 1000mL reaction bottle, adding 76.889g (99% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 62.344g (90% content, 1.0mol) of potassium hydroxide, heating and refluxing for about 4h until no new water is separated from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 93.293g of finished product potassium thiocyanate with the yield of 96%. The appearance is white powder with the content of 99.6 percent, no ammonium salt is detected, the pH value is 6.8, and the sulfate is 0.0012 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example ten:

adding 270mL of toluene into a 1000mL reaction bottle, adding 79.291g (96% content, 1.0mol) of ammonium thiocyanate under the stirring condition, adding 116.896g (48% content, 1.0mol) of liquid potassium hydroxide, heating and refluxing for about 7h until no new water is separated out from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 91.349g of finished product potassium thiocyanate with the yield of 94%. The appearance of the product is white powder, the content of the product is 99.6 percent, ammonium salt is not detected, the pH value is 6.8, and sulfate is 0.001 percent. The product quality far exceeds the superior product (99.0%) of the national index.

Example eleven:

adding 1620mL of toluene into a 30L reaction bottle, adding 4.757kg (96% content, 60.0mol) of ammonium thiocyanate under the stirring condition, adding 3.740kg (90% content, 60.0mol) of potassium hydroxide, heating and refluxing for about 4h until no new water is separated out from a water separator, cooling a reaction system to 40 +/-5 ℃, filtering, mechanically applying filtrate, and drying a filter cake in vacuum to obtain 5.598kg of finished product potassium thiocyanate with the yield of 96%. The appearance is white crystal with 99.8% content, no ammonium salt, 6.9 pH value and 0.003% sulfate. The product quality far exceeds the superior product (99.0%) of the national index.

In the above embodiment, the optimal temperature for heating reflux is controlled at 77-150 deg.C, and the filtration mode can be direct suction filtration, centrifugation or filter pressing.

Comparative analysis with respect to drying conditions:

the crude product separated out was dried in different forms at different temperatures to give the product quality shown in table 1.

TABLE 1

In the embodiment of the invention, the raw materials with other qualities sold in the market are as follows: 99 percent of ammonium thiocyanate, 90 percent of potassium hydroxide, 95 percent of high-quality potassium hydroxide and 48 percent of liquid potassium hydroxide (the potassium hydroxide of 4 manufacturers of Qinghai salt lake, Tangshan Sanfu, Chengdu Hua-Rong and Jiangsu Youlide is purchased, the content of each batch needs to be re-measured before each use, and the proportioning feeding is carried out aiming at the real content), all meet the requirements of the invention, and the requirements of the invention on the product quality of the raw materials are not high.

The foregoing description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the present invention in any way, although the present invention has been disclosed in connection with the preferred embodiments, it is not intended to limit the present invention, and it will be appreciated by those skilled in the art that changes and modifications may be made to the embodiments without departing from the scope of the invention. However, any modification, equivalence and equivalent changes made to the above embodiments according to the present invention are still within the scope of the technical solution of the present invention, without departing from the spirit of the technical solution of the present invention.

Claims

1. A method for synthesizing potassium thiocyanate is characterized by comprising the following steps: taking ammonium thiocyanate and potassium hydroxide with a molar ratio of 1:1 as raw materials, adding a water-carrying organic solvent, wherein 3-5mL of the organic solvent is added into every 1g of the raw materials, the water-carrying organic solvent is one of benzene, toluene, xylene, n-butanol, dichloroethane and ethyl acetate, removing generated water through heating reflux, directly filtering after cooling crystallization, drying the crude product to obtain the finished product of potassium thiocyanate, and directly returning the obtained organic filtrate for application, wherein the crude product drying mode is one of blast drying, vacuum double-cone drying and positive-air rake type.

2. The method for synthesizing potassium thiocyanate according to claim 1, wherein: the organic solvent with water is toluene.

3. The method for synthesizing potassium thiocyanate according to claim 1, wherein: the crude product drying mode is a vacuum double-cone mode.