Mechanism of the effect of Fe/Ca oxide on coal pyrolysis to HCN

LI Jingkuan; YE Lei; YANG Benjun; ZHAO Zhicheng; WU Jiao; GUO Congxiu; MENG Jiangtao; WANG Yanlin

doi:10.13225/j.cnki.jccs.2024.0845

Abstract：Fe2O3 and CaO are the main metal oxides in coal,which have an effect on NOx precursor-HCN generation dur-ing coal pyrolysis.In order to reveal the mechanism of Fe2O3 and CaO on HCN generation during coal pyrolysis,this pa-per adopts pyrrole as a nitrogen-containing model compound in coal,and investigates the different reaction paths of pyrrole pyrolysis for the generation of HCN,as well as the effects of Fe2O3 and CaO on HCN generation under different reaction paths,using the Density Functional Theory(DFT)and molecular simulation means.And Fe2O3 and CaO in differ-ent reaction paths on the pyrolysis of pyrrole to HCN.The results show that the best path of pyrrole pyrolysis to generate HCN is:H atom migrate from the interval of pyrrole-N to the neighbor,then pyrrole-N is disconnected from the adjacent C,the opening reaction occurs,finally the H atom on pyrrole-N migrate to the adjacent C,C—C bond is disconnected,the transition step of the path is the internal H transfer reaction,compared with the other path,the transition step has the low-est activation energy(2.54 eV).Under the action of Fe2O3 and CaO,the pyrrole heat to generate HCN optimal reaction path is:pyrrole-N and neighbor C,open the ring,its H atom migration to the neighbor C,the last pyrrole-N neighbor C and interval,the path of the path is open ring reaction(Fe2O3)reaction and internal H transfer reaction(CaO),compared to oth-er path,the path is the lowest activation energy,3.44 eV(Fe2O3)and 1.69 eV(CaO).Under the action of Fe2O3,the activa-tion energy of snap steps in different reaction paths increases,that is,Fe2O3 inhibited the generation of HCN.CaO shows different effects(inhibition or promotion)on different paths.In the optimal path under the action of CaO,the activation energy of the burst step is reduced to 1.69 eV,that is,CaO catalyzes the generation of HCN.In the same reaction path,CaO is more prominent than Fe2O3 in catalytic pyrrole pyrolysis to generate HCN,and HCN forms faster.