Performance of an internally circulating fluidized-bed reactor for the catalytic oxidative coupling of methane

The oxidative coupling of methane to C-2-hydrocarbons (OCM) over a La2O3/CaO catalyst (27 at.%) was investigated in an internally circulating fluidized-bed (ICFB) reactor (IDeff = 1.9 cm, H-riser = 20.5 cm). The experiments were performed in the following range of conditions: T = 800-900 degrees C, p(CH4):p(O2):p(N2) = 57.1-64:16-22.9:20 kPa. The obtained C-2 selectivities and C-2 yields were compared with the corresponding data from a spouted-fluid-bed reactor (ID = 5 cm) and a bubbling fluidized-bed (F1B) reactor (ID = 5 cm). The maximum C-2 yield in the internally circulating fluidized-bed (ICFB) reactor amounted to 12.2% (T 860 degrees C, 38.7% C-2 selectivity, 31.5% methane conversion), whereas in the FIB reactor a maximum C-2 yield of 13.8% (T= 840 degrees C, 40.4% C-2 selectivity, 34.2% methane conversion) was obtained. The lowest C-2 yield was achieved in the spouted-bed (SFB) reactor (Y-C2 = 11.6%, T= 840 degrees C, 36.2% C-2 selectivity, 32.0% methane conversion). The highest space-time yield of 24.0 mol/kg(cat).h was obtained in the ICFB reactor, whereas in a F1B reactor only a space-time yield of 9.6 mol/kg(cat).h could be obtained. The performance of the ICFB reactor was strongly influenced by gas-phase reactions. Furthermore, stable reactor operation was possible only over a narrow range of gas velocities.