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

• A kinetic model for oxidative coupling of methane on Li/MgO catalyst was developed.
• The kinetic rate parameters were estimated by genetic algorithm optimization method.
• The proposed model predicted the parameters of rate equations with AARD of ±9.9%.
• The inhibiting effect of O2 and CO2 should be considered in kinetic evaluations.
• The catalyst exhibited constant catalytic activity and stability during experiments.

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%.