Ce modified Cu/Zn/Al catalysts for direct liquefaction of microcrystalline cellulose in supercritical methanol

Conventional Cu/Zn/Al catalysts were modified by the incorporation of cerium (Ce) through co-precipitation method, and were then applied to the catalytic liquefaction of microcrystalline cellulose (MCC) in supercritical methanol at 300 °C for 1 h. Catalyst Cu_1.2Zn_4.8Al_1.9Ce_0.1 exhibited the best activity, with the MCC conversion of 87.6% and the selectivity of alcohols in liquid products of 88.3% (mainly C4–C7 alcohols), compared with Cu_1.2Zn_4.8Al_2.0 (MCC conversion of 69.62% and alcohol selectivity of 31.37%). The incorporation of CeO₂ improved the dispersion of active CuO and its interface interaction with catalyst support, which made the dispersed CuO easier to be reduced at lower temperature, and thus significantly improved catalyst activity and MCC conversion. CeO₂ also promoted the performance of the catalyst both in the methanol reforming reaction and the dehydration of intermediates to ketones, which benefited the production of C4–C7 alcohols through the synergism of CeO₂ with CuO and ZnO in the Cu-based catalysts. However, excess addition of Ce generated bulk CeO₂ crystals on the catalyst surface, which inversely reduced catalyst activity and the production of C4–C7 alcohols.