Kinetic modeling of oxidative coupling of methane over Li/MgO catalyst by genetic algorithm

摘要

A comprehensive kinetic model for oxidative coupling of methane (OCM) on Li/MgO catalyst was developed based on a fixed bed cylindrical reactor data. The methane conversion and ethylene, ethane, carbon monoxide, carbon dioxide, propane and propylene selectivity were obtained in a wide range of operating conditions including 710 < T < 850 °C, 1 < CH4/O2 < 4 and gas hourly space velocity (GHSV) between 35 and 150 h~(-1) at P = 760 mmHg. A 16-step reaction scheme defined to the description of a reaction network that considers both catalytic and gas-phase as well as primary and consecutive reaction steps to predict the performance of the OCM. The kinetic rates involved Langmuir-Hinshelwood-Hougen-Watson type rate equations, which considered the inhibiting effect of carbon dioxide and oxygen on oxidation reactions and power-law rate equations for remained reactions. The kinetic rate parameters were estimated using genetic algorithm optimization method. Comparing the experimental and model predicted data showed that presented model has a reasonable fit between the experimental data and the predicted values with average absolute relative deviation of ±9.9%.