Coating powdered copper catalyst with yttria sol

A commercial Y2O3 sol was tested as a binder for coating CuZnAl catalyst powder onto microchannels of a stainless steel plate (SSP). Coated plates were used to fabricate microchannel reactors that generate hydrogen via the steam reforming of methanol (SRM). Washcoating slurries were prepared by suspending catalyst powders into the sol. Slurry parameters, such as solid content, binder content, pH value, and stir time, were optimized to achieve a stable catalyst coating and good SRM performance. The expected stable coating could be obtained from neutral (pH 7) Y2O3 slurry that is required for a negligible dissolution of the copper component of the catalyst. The experimental coating stability generally improved with the slurry stir time. Observed improvements were attributed to a dispersion of catalyst powders in the slurry through a two-step mechanism: the mechanical disassembly of agglomerated CuZnAl powders into primary particles, and the repelling of dissembled particles through adsorption of positively charged Y2O3 binders. A reasonable reaction temperature of 280 °C was found for 95% conversion of methanol in SRM from the resulted microchannel reactors. A low CO fraction of 0.3% was also found in the hydrogen-rich gas reformed.

Research highlights
► The neutral Y2O3 sol is an effective binder for coating powders of CuZnAl catalyst.
► A particle size ratio of 15 for catalyst to binder is suggested for stable coating.
► Sufficient stirring is an important step in the catalyst slurry preparation.