OXIDATIVE COUPLING OF METHANE IN A BUBBLING FLUIDIZED-BED REACTOR

The oxidative coupling of methane to higher hydrocarbons (C2+) was studied in a bubbling fluidized bed reactor between 700-degrees-C and 820-degrees-C, and with partial pressures of methane from 40 to 70 kPa and of oxygen from 2 to 20 kPa; the total pressure was ca 100 kPa. CaO, Na2CO3/CaO and PbO/gamma-Al2O3 were used as catalytic materials. C2+ selectivity depends markedly on temperature and oxygen partial pressure. The optimum temperature for maximizing C2+ selectivity varies between 720 and 800-degrees-C depending on the catalyst. Maximum C2+ selectivities were achieved at low oxygen and high methane partial pressures and amounted to 46% for CaO (T = 780-degrees-C; P(CH4) = 70 kPa; P(o2) = 5 kPa), 53% for Na2CO3/CaO (T = 760-degrees-C; P(CH4) = 60 kPa; P(O2) = 6 kPa) and 70% for PbO/gamma-Al2O3 (T = 720-degrees-C; P(CH4) = 60 kPa; P(O2) = 5 kPa). Maximum yields were obtained at low methane-to-oxygen ratios; they amounted to 4.5% for CaO (T = 800-degrees-C; P(CH4) = 70 kPa; P(O2) = 12 kPa), 8.8% for Na2CO3/CaO (T = 820-degrees-C; P(CH4) = 60 kPa; P(O2) = 20 kPa) and 11.3% for PbO/gamma-Al2O3 (T = 800-degrees-C; P(CH4) = 60 kPa; P(O2) = 20 kPa).