Bimetallic Pt–Ni composites on ceria-doped alumina supports as catalysts in the aqueous-phase reforming of glycerol

Abstract

Although Pt is the most appropriate catalyst for aqueous phase reforming (APR) of glycerol to generate H₂, it is expensive. We studied its possible minimisation to levels where acceptable H₂ yields are still maintained. When an additional catalytic metal, Ni, was introduced to our Pt/CeO₂–Al₂O₃ catalyst, the Pt content could be reduced from 3 to 1 wt%, with a slight increase in H₂ production. In this study, Pt and Ni in various ratios were supported on alumina doped with 3 wt% ceria, and the resulting materials were characterised and tested as catalysts for the APR of glycerol. Amongst the catalysts tested, bimetallic 1Pt–6Ni/3CeAl (containing 1 wt% Pt and 6 wt% Ni) gave the highest H₂ yield (86%) and gas-phase C yield (94%). Thus, although 1Pt–6Ni/3CeAl and our reported 3Pt/3CeAl catalyst produced almost same amount of H₂ (1.8 and 1.9 mmol, respectively) per gram of catalyst per hour, the latter produced three times as much H₂ per gram of Pt per hour (195 mmol); this measure is crucial to the competitiveness of a catalyst in large-scale H₂ production. X-ray diffraction (XRD) patterns and thermogravimetric analyses of the spent catalysts showed no serious catalyst deactivation by carbon deposition after 30 h on stream, except in the case of Pt-free 6Ni/3CeAl, which ceased to produce H₂ after 15 h on stream. XRD and X-ray photoelectron spectroscopic analyses demonstrated that adding Ni impacted both the crystallite and electronic structure of Pt. These effects likely conspired to produce the high glycerol conversion and gas phase C yield and, ultimately, the high H₂ yield observed over 1Pt–6Ni/3CeAl.