Theoretical chemical kinetics for catalytic pyrolysis of methyl acetate over H-ZSM-5 zeolites

Abstract

The catalytic chemistry of methyl acetate (MA) over zeolites was investigated theoretically at the M06-2X/6–311++G(d,p) level, and its chemical reaction rate constants were calculated by using the transition state theory. With particular interest in looking for feasible reactions of the protolytic cracking channels, the present study reveals that the ketene formation in the concerted mechanism and that of acetyloxy + CH3 are competitive reactions during MA consumption. Furthermore, comparisons between the catalytic and conventional pyrolysis of MA were carried out to demonstrate the benefits of introducing the catalysts to MA combustion. It is demonstrated that the energy barriers of the dissociation reactions for MA over H-ZSM-5 zeolites decrease significantly compared with the conventional pyrolysis of MA. Changes of production distributions were also observed between the catalytic pyrolysis and the conventional pyrolysis. The results also provides new insight into the mechanism of the MA catalytic pyrolysis that will guide the improvements in the engine combustion efficiency and in the control of volatile organic compounds, and will also help to improve the selectivity of the conversion of methanol to hydrocarbon and olefin products.