HCN消除反应机理的理论研究

采用密度泛函理论方法从HCN氧化和水解两个方面研究了HCN消除反应机理，并考虑了HCN的直接消除反应(途径Ⅰ和途径Ⅱ)和CuO上的HCN消除反应(途径Ⅲ和途径Ⅳ)。途径Ⅰ为HCN与2个O2分子生成CO2、NO和H原子；途径Ⅱ为HCN与1个O2分子和1个H2O分子生成 CO2和NH3；途径Ⅲ为CuO上HNCO水解为CO2和NH3；途径Ⅳ为CuO上HCN水解为CO和NH3。研究发现，途径III速控步骤的活化自由能垒为157.32 kJ/mol，比途径Ⅱ中HNCO水解降低12.34 kJ/mol；比途径Ⅳ降低了63.8 kJ/mol。可见，HNCO是HCN净化过程中的重要中间体，CuO的加入降低了反应能垒，促进了HCN消除。

Theoretical Study on the Reaction Mechanism of HCN Elimination

The reaction mechanism of HCN elimination was studied from two aspects of HCN oxidation and hydrolysis by density functional theory method, and the direct elimination of HCN (pathway I and pathway II) and the elimination of HCN on CuO (pathway III and pathway IV) were considered. HCN reacted with two O2 molecules to form CO2, NO and H atom in the pathway I. HCN reacted with one O2 molecule and one H2O molecule to form CO2 and NH3 in the pathway II. HNCO was hydrolyzed to CO2 and NH3 on CuO in the pathway III. HCN was hydrolyzed to CO and NH3 on CuO in the pathway IV. It was found that the activation free energy barrier of the rate-controlling step of pathway III was 157.32 kJ/mol, which was 12.34 kJ/mol lower than that of HNCO hydrolysis in the pathway II, and 63.8 kJ/mol lower than that of pathway IV. It can be seen that HNCO is an important intermediate in the purification process of HCN, and the addition of CuO effectively reduces the reaction energy barrier and promotes the elimination of HCN.