Study on mechanism of isomerization between ammonium thiocyanate and thiourea

• Mechanism of isomerization from ammonium thiocyanate to thiourea.
• Relationship between equilibrium constant of the isomerization and temperature.
• Lowered activation energy of the isomerization catalyzed by NH3.

Application of ammonium thiocyanate that can be separated from wastewater in coking plant is limited. It may isomerize to thiourea which has widely applied in industry. However, the isomerization yield is low. Moreover, the isomerization temperature is more than 145 °C. In this paper, the isomerization was investigated. The mechanism of the isomerization was supposed based on quantum chemistry calculations. Ammonia was employed as a catalyst to lower isomerization temperature and improved the yield of thiourea in the isomerization reaction. Results of quantum chemical calculation and experiments support the supposed mechanism. The mechanism can be applied in production of thiourea from isomerization of ammonium thiocyanate. The paper suggests a useful way of resourcizing ammonium thiocyanate in wastewater.

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