LAUSR

Abstract To investigate the kinetics of hydrogen addition reactions of intermediate-sized unsaturated fatty acid methyl esters at C = C sites, the reaction rate constants of methyl 5-decenoate at 300–2500 K were computed. The potential energy surface was determined using quantum chemical methods at different levels of theory, including M06-2X, ONIOM and CGA-ONIOM. The high-pressure limit rate constants were computed by conventional transition state theory including the one-dimensional torsional anharmonicity and Eckart tunneling corrections. The pressure-dependence of the rate constants of hydrogen addition and the subsequent dissociation reactions was considered by master equation analysis. The results show that the mean absolute deviations of the barrier heights by M06-2X and ONIOM are 1.0 and 0.6 kcal/mol from that by CGA-ONIOM respectively, which results in a factor of 2.7 difference in rate constants at 500 K between the M06-2X and CGA-ONIOM results. The calculated rate constants were applied in a combustion model of methyl 5-decenoate and the modeling mole fractions of hexene and heptane agreed better with experimental data. The barrier heights of hydrogen addition reactions of a series of unsaturated fatty acid methyl esters were studied, and the recommended rate constants for the development of the combustion model of unsaturated fatty acid methyl esters were given.