(380c) Aqueous-Phase Reforming of Ethylene Glycol with Supported Pt and Pd Bimetallic Catalysts
More than 130 Pt and Pd bimetallic catalysts were screened for hydrogen production by aqueous-phase reforming (APR) of ethylene glycol solutions using a high-throughput reactor. Promising catalysts were characterized by CO chemisorption and tested further in a fixed bed reactor. Bimetallic PtNi, PtCo, PtFe and PdFe catalysts were significantly more active per gram of catalyst and had higher turnover frequencies for hydrogen production (TOFH2) than monometallic Pt and Pd catalysts. The PtNi/Al2O3 and PtCo/Al2O3 catalysts, with Pt to Co or Ni atomic ratios ranging from 1:1 to 1:9, had TOFH2 values (based on CO chemisorption uptake) equal to 2.8 to 5.2 min-1 at 483 K for APR of ethylene glycol solutions, compared to 1.9 min-1 for Pt/Al2O3 under similar reaction conditions. A Pt1Fe9/Al2O3 catalyst showed TOFH2 values of 0.3 to 4.3 min-1 at 453 to 483 K, about 3 times higher than Pt/Al2O3 under identical reaction conditions. A Pd1Fe9/Al2O3 catalyst had values of TOFH2 equal to 1.4 and 4.3 min-1 at temperatures of 453 and 483 K, respectively, and these values are 39 to 46 times higher than Pd/Al2O3 at the same reaction conditions. Catalysts consisting of Pd supported on high surface area Fe2O3 (Nanocat) showed the highest turnover frequencies for H2 production among those catalysts tested, with values of TOFH2 equal to 14.6, 39.1 and 60.1 min-1 at temperatures of 453, 483, and 498 K respectively. These results suggest that the activity of Pt based catalysts for APR can be increased by alloying Pt with a metal (Ni or Co) that decreases the strengths with which CO and hydrogen interact with the surface (because these species inhibit the reaction), thereby increasing the fraction of catalytic sites available for reaction with ethylene glycol. The activity of Pd based catalysts for APR can be increased by adding a water-gas shift promoter (e.g. Fe2O3).