Aqueous phase reforming of glycerol for hydrogen production over Pt-Re supported on carbon

Hydrogen production from the aqueous phase reforming of glycerol over 3%Pt-Re/C (1 and 3% Re) has been studied in the absence and presence of base, and the results compared with a Re-free 3%Pt/C catalyst. Although the Pt/C catalyst is very selective toward the production of hydrogen, catalytic activity is low. Addition of Re significantly increases the conversion of glycerol, at some loss of hydrogen selectivity to light hydrocarbons and water-soluble oxygenates. Addition of 1%KOH to the feedstock results in a small increase in glycerol conversion with 3%Pt-3%Re/C, an increase in the gas phase product selectivity in terms of H₂/CO₂ ratio, and an increase in production of aqueous phase oxygenates. A modest increase in hydrogen gas phase selectivity with base addition with 3%Pt-3%Re/C arises primarily from reducing the selectivity toward C₂⁺ alkanes, products that consume H₂. In comparison, KOH addition to the glycerol feed with the Re-free 3%Pt/C catalyst provides an increase in glycerol conversion but results in a decline in both H₂ and alkane selectivity relative to aqueous phase oxygenates. The highest hydrogen productivity among the catalysts tested is achieved with a 3%Pt-3%Re/C catalyst with added KOH base. The observed product distributions can be understood in terms of the different reaction pathways that become emphasized depending on catalyst composition and pH.