Effect of CeO2 and MgO promoters on the performance of a Ni/Al2O3 catalyst in the steam reforming of biomass pyrolysis volatiles

A Ni/Al2O3 catalyst has been modified incorporating CeO2 and MgO promoters in order to improve its performance in the steam reforming of biomass pyrolysis volatiles. Ni/Al2O3, Ni/CeO2-Al2O3 and Ni/MgO-Al2O3 catalysts have been prepared and fresh and deactivated catalysts have been characterized by N2 adsorption/ desorption, X-ray Fluorescence (XRF), Temperature Programmed Reduction (TPR), X-ray powder diffraction (XRD), Temperature Programmed Oxidation (TPO), Transmission Electron Microscopy (TEM) and a technique based on Fourier Transform Infrared Spectroscopy-Temperature Programmed Oxidation (FTIR-TPO). The results obtained revealed a similar initial activity for the three catalysts tested (conversion higher than 98%), whereas stability has been greatly improved by incorporating CeO2 as promoter, as it enhances the gasification of coke precursors. However, Ni/MgO-Al2O3 catalyst is slightly less stable than Ni/Al2O3, presumably as a result of its lower reducibility due to the formation of MgAl2O4 spinel phase. Catalysts deactivation has been associated with coke deposition, although sintering phenomenon became also evident when the Ni/CeO2-Al2O3 catalyst was tested. The coke deposited on the catalysts does not present any specific morphology, which is evidence of its amorphous structure in the three catalysts studied. This work was carried out with financial support from the Ministry of Economy and Competitiveness of the Spanish Government (CTQ2016-75535-R (AEI/FEDER, UE) and CTQ-2015-69436-R (MINECO/FEDER, UE)), Ministry of Science, Innovation and Universities of the Spanish Government (RTI2018-101678-B-I00 (MCIU/AEI/FEDER, UE)), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 823745, and the Basque Government (IT1218-19).