Theoretical Study on Catalytic Pyrolysis of Benzoic Acid as a Coal-Based Model Compound

Abstract

Benzoic acid (C6H5COOH) is selected as a coal-based model compound, and its catalytic pyrolysis mechanisms on ZnO, γ-Al2O3, CaO, and MgO catalysts are studied using density functional theory (DFT) compared to the non-catalytic pyrolysis mechanism. DFT calculation shows that the pyrolysis process of C6H5COOH in the gas phase occurs via the direct decarboxylation pathway (C6H5COOH → C6H6 + CO2) or the stepwise decarboxylation pathway (C6H5COOH → C6H6COO → C6H6 + CO2). For C6H5COOH catalytic pyrolysis on the ZnO (1010) surface, the preferred reaction pathway is C6H5COOH → C6H5COO + H → C6H6 + CO2, whereas the preferred reaction pathway on γ-Al2O3 (110), CaO (100), and MgO (100) surfaces is C6H5COOH → C6H5COO + H → C6H5 + CO2 + H → C6H6 + CO2, indicating that the presence of catalysts changed the pyrolysis mechanism of C6H5COOH. In addition, dissociative adsorption of C6H5COOH is observed on these surfaces. It is found that ZnO (1010), MgO (100), and CaO (100) are beneficial to C6H5COOH decomposition, but γ...