Catalytic Mechanism of Calcium on the Formation of HCN during Pyrolysis of Pyrrole and Indole: A Theoretical Study

• Published in: Energy & fuels 2019-11, Vol.33 (11), p.11516-11523
• Main Authors: Liu, Ji, Fan, Xin-rui, Zhao, Wei, Hu, Bin, Liu, Ding-jia, Lu, Qiang, Yang, Yong-ping
• Format: Article
• Language: English
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.9b02955

Calcium-based compounds are major inorganic components in coal and also widely used as additives in thermal conversion of coal and, thus, have important effects on the decomposition of nitrogen-containing compounds to form NO x . In this work, the influence of Ca2+ on the pyrolysis of pyrrole and benzopyrrole (indole) to form HCN, a precursor of NO x , was investigated via a density functional theory (DFT) calculation with B3LYP/6-31+G­(d,p) basis set. The results suggest that Ca2+ has strong interactions with pyrrole and indole by altering the original electron density distribution of the pyrrole ring and the configurations of pyrrole derivatives, respectively. Ca2+ affects the energy barriers of the elementary pyrolytic reactions (i.e., internal hydrogen transfer, isomerization, and concerted decomposition) and particularly reduces the energy barriers of the rate-determining steps for HCN formation. In comparison to alkali metal ion Na+, alkali earth metal ion Ca2+ has a stronger influence on the pyrrole and indole pyrolysis to form HCN.