OXIDATIVE COUPLING OF METHANE IN A FLUIDIZED-BED REACTOR OVER A HIGHLY-ACTIVE AND SELECTIVE CATALYST

Oxidative coupling of methane to C-2+ hydrocarbons over a Zr/LaiSr cat alyst was investigated in an atmospheric-pressure shallow fluidized-be d reactor (i.d. = 5 cm; H-mf = 1.4-3.2 cm) at temperatures between 800 and 880 degrees C. The catalyst was mechanically and catalytically st able, but its fluidizability was limited; agglomeration and channeling occurred. The highest C-2+ yield amounted to 18.0% (X(CH4) = 36.5%, S c-2+ = 49.4%) and 17.2% (X(CH4) = 36.6%, Sc-2+ = 46.9%) for the dilute d (p(o2) = 17 kPa, p(CH4) = 41.5 kPa, P-N2 = 41.5 kPa) and undiluted f eed (p(o2) = 28 kPa, p(CH4) = 72 kPa), respectively. These yields are among the highest ones reported in the open literature for OCM in flui dized beds. In the whole investigated temperature range higher selecti vities and yields were obtained upon reducing partial pressures of met hane and oxygen but keeping their ratio constant (p(CH4)/p(o2) = 2.5). An increased gas velocity (from u/u(mf) = 6 to 10) or bed height (fro m 1.4 to 3.2 cm) resulted in a drop of C-2+ selectivity.