Design of Efficient Noble Metal Free Copper-Promoted Nickel-Ceria-Zirconia Nanocatalyst for Bio-Fuel Upgrading

A new series of noble metal free bimetallic Cu-Ni supported ceria-zirconia catalysts (Cu-Ni/CZ) has been developed with various Cu/Ni ratios by a simple co-precipitation/impregnation method. Aqueous-phase hydrodeoxygenation (HDO) of vanillin a typical compound of lignin-derived bio-oil, in promoting biomass refining was carried out to investigate catalytic performances under 25bar of H-2 pressure at 160(o)C. All the as-synthesized catalysts were thoroughly characterised employing powder XRD, Raman spectroscopy, H-2-TPR, HR-TEM, HAADF-STEM, EDS Mapping, and XPS. It was found that 15wt% Cu on Ni/CZ (Cu-Ni/CZ-B) nanocomposite enhanced activity significantly in comparison with other bimetallic or monometallic catalysts, exhibiting similar to 98% of vanillin conversion and similar to 94% of selectivity toward 2-methoxy-4-methylphenol as a desired product. The Cu-Ni/CZ-B catalyst shows similar to 4-fold increase in activity compared with Cu-Ni/CeO2 and Cu-Ni/ZrO2, the mono oxide supported counterparts. The superior catalytic performance with improved stability were explained by synergistic effects at the interfaces of each species, in which electron interactions between Ni, Cu, and ceria-zirconia support generated novel active sites. XRD and HR-TEM revealed that Cu-Ni bimetallic phases were created on the ceria-zirconia, which were responsible for enhancement of catalytic performance with no significant drop in catalytic activity with desired product selectivity for eleven successive catalytic cycles demonstrating the excellent stability and reproducibility of this catalyst system.