Electrodeposited Cu-based Catalysts for Alcohols from CO Hydrogenation and Electrodeposition of CuNiW/CuNi Multilayered Alloys

Abstract

Ethanol and higher alcohols can be used as a fuel or fuel additive in gasoline engines as well as a hydrogen carrier. One of the promising methods to synthesize these alcohols is based on thermochemical conversion of CO and H2 (CO hydrogenation). Conventional catalysts used for the conversion CO and H2 (syngas) to ethanol typically give yields less than 20% with the balance resulting mostly in the formation of the thermodynamically favored products CH4 and CO2. New catalysts with compositions designed to kinetically favor the formation of ethanol and higher alcohols are needed. Electrodeposition of nanowires offers a means to control the surface properties of multimetallic catalysts in a way that is not possible with conventional catalyst preparation methods such as co-precipitation and impregnation. A principle advantage of electrodeposition over conventional methods centers on its ability to control the active metal environment at the atomic level. In this work, Cu-ZnO and Mn-Cu-ZnO novel nanowire/tube catalysts have been prepared by electrodeposition using a template synthesis technique. To the best of our knowledge, electrodeposited Cu-based nanowires have never been used as heterogeneous catalysts. Different current and pulsed current schemes were used to control composition and morphology of the resulting nanowire/tube catalysts. Pulse waveforms with suitable on-time (cathodic current) and off-times (no current) were used to tailor the atomic environment of the nanowire catalysts. A fixed bed tubular reactor was used to synthesize alcohols from CO and H2 (syngas). In addition to C2-C4 alcohols products of interest, methanol, methane, propylene, and CO2 were the main side products at various reaction conditions. The reaction was performed at varying temperature (250C-310C), pressure (10-20 bar), H2/CO ratio (1-3), and GHSV (7,500-33,000 scc/h-gcat). The addition of Mn to the Cu-ZnO catalyst increased the selectivity toward ethanol and higher alcohols by reducing methanation. Schulz-Flory distributions of the products suggest that the synthesis of alcohols and hydrocarbons require different sites.