Performance evaluation of Pt- and Pd-based catalysts on nickel & copper foams for methanol combustion in a microreactor

Catalytic combustion of methanol is regarded as a potential heat source for portable hydrogen generators. This study focuses on the synthesis and performance of catalysts consisting of metallic foams (copper and nickel) coated with alumina supported platinum (Pt/Al 2 O 3 ) and palladium (Pd/Al 2 O 3 ) for methanol combustion at atmospheric pressure. Catalysts were prepared at active metal loading of 2.4 and 3.6 mg/cm 3 foam (bulk volume) and their performances were evaluated in a dedicated microreactor at gas hourly space velocities ranging from 5200 to 10,010 h − 1 . The feed consisted solely of methanol and oxygen with oxygen/methanol ratios from 15% deficient to 15% excess to stoichiometric value. By identification of microreactor’s exhaust composition, it was found that some side reactions such as methanol steam reforming, reverse water-gas shift (RWGS) and methanation took place along with the main combustion reaction. The tendency for RWGS and methanation reactions was higher in the nickel foam. As an active catalyst metal, palladium showed higher methanol combustion affinity than platinum. Also, by reducing the oxygen to methanol ratio in feed, the contribution of reforming and RWGS reactions increased significantly. Increasing the active metal loading enhanced the share of combustion and consequently leads to a higher temperature in the reaction zone. The combination of palladium catalyst on nickel foam showed superior performance regarding combustion affinity, reaction and mechanical stability, over all other combinations of nickel/copper foams with platinum/palladium catalytically active metals. For copper foam based catalysts, its poor mechanical behavior during numerous temperature cycles of the reactor’s startup/shutdown steps, precludes it from being a suitable support for methanol combustion catalyst.