Industrial hydrogen production through methane steam reforming exceeds 50 million tons annually and accounts for 2–5% of global energy consumption. The hydrogen product, even after processing by the water–gas shift, still typically contains ∼1% CO, which must be removed for many applications. Methanation (CO + 3H₂ → CH₄ + H₂O) is an effective solution to this problem, but consumes 5–15% of the generated hydrogen. The preferential oxidation (PROX) of CO with O₂ in hydrogen represents a more-efficient solution. Supported gold nanoparticles, with their high CO-oxidation activity and notoriously low hydrogenation activity, have long been examined as PROX catalysts, but have shown disappointingly low activity and selectivity. Here we show that, under the proper conditions, a commercial Au/Al₃O₂ catalyst can remove CO to below 10 ppm and still maintain an O₂-to-CO₂ selectivity of 80–90%. The key to maximizing the catalyst activity and selectivity is to carefully control the feed-flow rate and maintain one to two monolayers of water (a key CO-oxidation co-catalyst) on the catalyst surface.

Nature Chemistry (2016) doi:10.1038/nchem.2494
Received 01 May 2015 Accepted 08 March 2016 Published online 18 April 2016

http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2494.html