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

Abstract

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 Ca 2+ 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 Ca 2+ 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. Ca 2+ 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 ratedetermining steps for HCN formation. In comparison to alkali metal ion Na + , alkali earth metal ion Ca 2+ has a stronger influence on the pyrrole and indole pyrolysis to form HCN.

Recent Progress in Quantum Chemistry Modeling on the Pyrolysis Mechanisms of Lignocellulosic Biomass

“…In the recent decades, computational methods, including QC modeling, molecular dynamics (MD), ab initio molecular dynamics (AIMD), and machine learning, have been prevailing and played important roles in the mechanism studies of many fields. ,− QC modeling is currently the most popular computational method to investigate the pyrolysis mechanism of biomass. Generally, QC modeling can give relatively accurate results, and the calculated thermodynamic data are useful to build the microkinetic models.…”

Virtual Special Issue of 7th Sino-Australian Symposium on Advanced Coal and Biomass Utilisation Technologies

“…Yang et al (10.1021/acs.energyfuels.9b03310) prepare different hierarchical HZSM-5 for enhancing the light aromatic yield from lignite pyrolysis. Liu et al (10.1021/acs.energyfuels.9b02955) investigate the catalytic mechanisms of calcium (Ca) and sodium (Na) on the formation of HCN during pyrolysis of pyrrole and indole via density functional theory (DFT) calculations. Li et al (10.1021/acs.energyfuels.9b02924) prepare nitrogen-doped hierarchical porous biochar from corn stalks for enhanced phenol adsorption.…”