Development of a detailed high-pressure reaction model for methane/methanol mixtures under pyrolytic and oxidative conditions and comparison with experimental data

Abstract

Experimental data of methanol in a flow reactor are obtained under pyrolysis, fuel lean condition ( φ=0.75), and stoichiometric condition ( φ=1.0), and as mixtures with methane; both temperature and pressure are varied. Methanol pyrolysis is studied at 1073 K over a pressure range of 1–10 atm. Methanol oxidation experiments are conducted over a temperature range of 873–1073 K and a pressure range of 1–5 atm. Oxidation experiments on methane/methanol mixtures are performed under total stoichiometric conditions, with ratios of the two fuels from 0:2 to 2:0. Under pyrolytic conditions, the methanol decay rate increases as pressure increases from 1 to 10 atm. The addition of methanol increases the methane oxidation rate nonlinearly up to 1:1 mole ratio for methanol/methane. The rate of CH 4 decay is slower above a CH 4/CH 3OH ratio of 3:1. The maximum decay rate of CH 4 occurs at an equimolar concentration of CH 4/CH 3OH. A pressure-dependent mechanism for the methane/methanol oxidation and pyrolysis reaction system has been developed and compared with experimental data. Pressure- and temperature-dependent rate constants are determined by utilizing quantum RRK (QRRK) combined with “master equation” analysis for falloff on bimolecular (chemical activation) association, addition, and insertion reactions, and in unimolecular dissociation and isomerization reactions. Methanol dissociation reaction channels, transition states (TS), product energies, and structures are calculated at the CBS-APNO level with kinetic parameters for simple bond dissociations estimated by variational transition state theory.