A method for preparing thiourea

By converting sulfur paste into thiourea using ammonium polysulfide intermediates, the problems of high energy consumption and safety hazards in sulfur paste processing are solved, and high-purity thiourea is prepared, which has significant environmental and economic benefits.

CN122102985APending Publication Date: 2026-05-29SHANDONG YANGGU HUATAI CHEM
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
SHANDONG YANGGU HUATAI CHEM
Filing Date
2026-03-23
Publication Date
2026-05-29

AI Technical Summary

Technical Problem

In existing technologies, the treatment of sulfur paste has problems such as high energy consumption, serious pollution and waste of resources. In addition, hydrogen sulfide gas poses safety hazards in the production of thiourea and it is difficult to efficiently convert sulfur paste with complex components into high-purity thiourea.

Method used

Using ammonium polysulfide as an intermediate, the sulfur source is reacted with ammonium sulfide to generate ammonium polysulfide, which is then reacted with calcium cyanamide to generate calcium thiocyanate. The product is then carbonized with CO2 and isomerized by adding an ammonia source to finally generate thiourea. The entire process is carried out at a mild temperature to avoid the emission of harmful gases.

Benefits of technology

This technology enables the conversion of low-value sulfur paste into high-purity thiourea in a safe and environmentally friendly process that reduces energy consumption and avoids harmful gas emissions, resulting in significant environmental and economic benefits.

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Abstract

The application provides a method for preparing thiourea, and belongs to the technical field of industrial solid waste resource utilization and fine chemical product synthesis. The method comprises the following steps: mixing a sulfur source with an ammonium sulfide aqueous solution, and performing reaction to obtain a solution containing ammonium polysulfide, wherein the sulfur source contains elemental sulfur; reacting the solution containing ammonium polysulfide with calcium cyanamide to obtain a solution containing calcium thiocyanate; introducing CO2 into the solution containing calcium thiocyanate to perform carbonization, and then adding an ammonia source to perform isomerization reaction to obtain thiourea. In the application, elemental sulfur is finally synthesized into thiourea through a key intermediate, ammonium polysulfide, and the production process is more inherently safe, which can be used for directly high-valuing hazardous waste sulfur paste into thiourea, the whole process is free of harmful gas emission, is environment-friendly, and has significant economic value.
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