EFFECTS OF CO2 DURING OXIDATIVE COUPLING OF METHANE OVER LI MGO - MECHANISMS AND MODELS/

The effects Of CO2 partial pressure on oxidative methane coupling over a Li/MgO catalyst were studied under low conversion conditions in a f low reactor. Methane to oxygen ratios from 0.5 to 35 and temperatures from 973 to 1073 K were used in the experiments and modeling. Varying flow rates Of CO2 were mixed with the methane and oxygen prior to the reaction. Results indicate that CO2 has a poisoning effect on both car bon oxides (CO and CO2) and C2 hydrocarbon (C2H4 and C2H6) formation r ates, while selectivity to the C2 hydrocarbon was not significantly af fected. The apparent activation energy increased with CO2 partial pres sure in the feed. Results also indicate that a small amount of methane reacts with carbon dioxide to produce carbon monoxide. Empirical rate expressions and rate expressions rigorously derived from proposed mec hanisms were obtained. The rate expressions agree well with the measur ed rates and also predict the observed trend in apparent activation en ergy.