Understanding the Chemistry of H2 Production for 1‑Propanol Reforming: Pathway and Support Modification Effects

The liquid-phase reforming of 1-propanol over a platinum-based catalyst on a number of supports was investigated. Propanol is being used as a surrogate for biomass-derived glycerol as a source of hydrogen in the conversion of cellulose to transportation fuels. The test conditions were high temperature (230–260 °C) and pressure (69 bar) in the presence of liquid water. Under these conditions, Pt over alumina coated (via atomic layer deposition) with a layer of approximately 1 nm of Al2O3, TiO2, or Ce2O3 (Pt–Al, Pt–Ti, Pt–Ce) is active for the reforming of 1-propanol. The Pt–Ti catalyst had the highest 1-propanol conversion rate per gram of catalyst followed by the Pt–Al and Pt–Ce catalysts, which had similar rates of reaction. Selectivity for each catalyst was primarily to ethane and CO2, with the ratio between the two products being close to unity regardless of temperature. The hydrogen yield was constantly higher than twice the ethane yield, indicating that H2 formation occurs before ethane is formed. Decarbonylation of propanal did not appear to contribute significantly to the formation of ethane. The propionic acid, which can produce ethane and CO2 through decarboxylation, is believed to form from the disproportionation of propanal. In contrast to the Canizzarro reaction, this reaction appears to be catalyzed by the supported Pt and not the support or in solution (through base catalysis). Our analyses also showed that well dispersed Pt sinters under the high temperature and high partial pressure of water in the reactor, and under reaction conditions that the surface of the Pt has high concentrations of CO (43% of the coverage of CO at room temperature) and water (96% of the coverage of water at 230 °C and 34 bar).