Embedded Ni Nanoparticles in Ceo2-Zro2 as Robust Catalyst for Levulinic Acid Hydrogenation

Abstract

Ni-catalysts are ideal candidate for lauric acid hydrogenation, but are restrained by their poor GVL selectivity and durability. Herein, mesoporous Ni/CeO2-ZrO2 catalysts with different ZrO2 loading were prepared by precipitation and impregnation, yielding 94.3% GVL yield at 99.3% LA conversion. This catalyst also displayed desired stability during the recycle test, affording 84.6% GVL yield at 90.2% LA conversion after six consecutive runs. Experimental data displayed that ZrO2-addition strongly effected hydrogenation selectivity. OV species formed on partial reduced CeO2-ZrO2 surface tightly grasp Ni NPs and activate C=O bond, increasing Ni NPs dispersion and simultaneously stimulating ketone C=O→CH-OH conversion. The synergism between electron-rich Ni site and OV species strengthens the interaction of reactant and catalyst surface and resultantly form desired η2(C,O)-aldehyde configuration, promoting the formation of HPA intermediate. The Brønsted acidity of the Ni/CeO2-ZrO2 catalysts is affected by ZrO2 addition and is vital for enhancing the catalyst activity toward the intramolecular esterification of HPA intermediate, contributing to the high yield of GVL.

Keywords: lauric acid, γ-valerolactone, hydrogenation, Ni/CeO2-ZrO2 catalysts, 2(C, O)-aldehyde configuration