Oxidative coupling of methane over a La 2 O 3 /CaO catalyst. Optimization of reaction conditions in a bubbling fluidized‐bed reactor

Oxidative coupling of methane over a La 2 O 3 /CaO catalyst was investigated in laboratory‐scale fluidized‐bed reactors (ID = 5 and 7 cm) in the following range of reaction conditions: T = 700 – 880°C, P   CH   4= 41 – 72 kPa and P   O   2= 6 – 29 kPa. The maximum C 2+ selectivity and yield amounted to 73.8% ( T = 800°C, X   CH   4= 13.1%, Y   C   2+= 9.7%) and 16.0% ( T = 840°C, X   CH   4= 34.0%, S   C   2+= 47.2%), respectively. Axial gas concentration profiles revealed that C 2+ selectivity was not only influenced by oxidative consecutive reactions, but also by steam reforming of ethylene. When diluting the catalytic bed ( m cat = 145 g) with quartz ( m   siO   2= 200 and 400 g), a slight decrease of the selectivity (1–2%) was observed. The dilution of the feed gas with nitrogen only led to only a small increase (< 2%) of the C 2+ selectivity.