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

The oxidative coupling of methane to C₂-hydrocarbons (OCM) over a La₂O₃/CaO catalyst (27 at.%) was investigated in an internally circulating fluidized-bed (ICFB) reactor (ID_eff = 1.9 cm, H_riser = 20.5 cm). The experiments were performed in the following range of conditions: T = 800?900°C, p_CH4:p_O2p_N2 = 57.1–64:16–22.9:20 kPa. The obtained C₂ selectivities and C₂ yields were compared with the corresponding data from a spouted-fluid-bed reactor (ID = 5 cm) and a bubbling fluidized-bed (FIB) reactor (ID = 5 cm). The maximum C₂ yield in the internally circulating fluidized-bed (ICFB) reactor amounted to 12.2% (T = 860°C, 38.7% C₂ selectivity, 31.5% methane conversion), whereas in the FIB reactor a maximum C₂ yield of 13.8% (T = 840°C, 40.4% C₂ selectivity, 34.2% methane conversion) was obtained. The lowest C₂ yield was achieved in the spouted-bed (SFB) reactor (Y = 11.6%, T = 840°C, 36.2% C₂ 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 FIB reactor only a space-time yield of 9.6 mol/kg_catcould 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.