CO Total and Preferential Oxidation over Stable Au/TiO2 Catalysts Derived from Preformed Au Nanoparticles

DIVINS, NÚRIA J.; LÓPEZ, EDUARDO; ANGURELL, INMACULADA; NEUBERG, STEFAN; ZAPF, RALF; KOLB, GUNTHER; LLORCA, JORDI

Catalysts

MDPI

Lugar: Basel; Año: 2020 vol. 10

CO preferential oxidation (PROX) is an eective method to clean reformate H2 streams tofeed low-temperature fuel cells. In this work, the PROX and CO oxidation reactions were studied onpreformed Au nanoparticles (NPs) supported on TiO2 anatase. Preformed Au NPs were obtainedfrom gold cores stabilized by dodecanethiols or trimethylsilane-dendrons. A well-controlled sizeof ca. 2.6 nm and narrow size distributions were achieved by this procedure. The catalysts werecharacterized by high-resolution transmission electron microscopy and ex situ and in situ X-rayphotoelectron spectroscopy (XPS). The XPS results showed that the preformed Au NPs exhibitedhigh thermal stability. The dierent ligand-derived Au catalysts, as well as a conventional goldcatalyst for comparison purposes, were loaded onto cordierite supports with 400 cells per squareinch. The activity and selectivity of the samples were eValuated for various operation conditions.The catalyst prepared using dodecanethiol-capped Au NPs showed the best performance. In fact, CO conversions of up to 70% at 40% CO2 selectivity and 90% O2 conversion were observed operating at 363 K in H2-rich atmospheres. The performance of the best catalysts was subsequently tested on stainless steel microreactors. A 500-hour stability test was carried out under a real post-reformate stream, including 18 vol.% CO2 and 29 vol.% H2O. A mean CO conversion of ca. 24% was measured for the whole test operating at 453 K and a gas hourly space velocity (GHSV) of 1.3 104 h􀀀1. These results reveal our dodecanethiol- and carbosilane-derived Au catalysts as extremely promising candidates to conduct a PROX reaction while avoiding deactivation, which is one of the major drawbacks of Au/TiO2 catalysts.