Aqueous-phase reforming of n-BuOH over Ni/Al2O3 and Ni/CeO2 catalysts

Abstract

The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al2O3 and CeO2 catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al2O3 catalyst showed significant deactivation compared to the Ni/CeO2 catalyst, both in terms of production rates and the selectivity to H2 and CO2. The Ni/CeO2 catalyst demonstrated higher selectivity for H2 and CO2, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al2O3 sample. For the Ni/Al2O3 catalyst, the selectivity to CO increased with temperature, while the Ni/CeO2 catalyst produced no CO. For the Ni/CeO2 catalyst, the activation energies for H2 and CO2 production were 146 and 169 kJ mol−1, while for the Ni/Al2O3 catalyst these activation energies were 158 and 175 kJ mol−1, respectively. The difference of the active metal dispersion on Al2O3 and CeO2 supports, as measured from H2-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al2O3 catalyst. It is unlikely that carbon would build up on the Ni/CeO2 catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO2 lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO2 mostly through water gas shift. Ethane and methane are formed via Fischer–Tropsch reactions of CO/CO2 with H2.