Construction of Ni–Co alloy/zeolite nanosheet catalysts for the hydrodeoxygenation of fatty acids to alkanes†

Abstract

Hydrodeoxygenation of bio-lipids into renewable alkanes is a promising strategy to substitute fossil resources. Bifunctional metals/zeolites have demonstrated high performance in hydrodeoxygenation reactions but suffer from severe mass transfer limitation and low carbon atom economy. Here, we synthesize a hierarchically porous metal/zeolite catalyst consisting of ZSM-5 zeolite nanosheet-supported bimetallic Ni–Co alloy nanoparticles. The strategy utilizes self-pillared ZSM-5 nanosheets as supports to grow layered bimetallic Ni–Co silicates. Following a hydrogen reduction, bimetallic Ni–Co alloy nanoparticles are anchored on zeolites. Compared to conventional metals/zeolites, the nanosheet self-supported Ni–Co alloy/ZSM-5 composites feature a rich mesoporous structure, high specific surface area, and highly dispersed alloy nanoparticles with tailored loading and atomic ratios of each metal component. In the hydrodeoxygenation of stearic acid, the prepared Ni–Co alloy/ZSM-5 catalysts achieve complete conversion of stearic acid within 50 minutes, with a reaction rate of 25.5 g g_cat⁻¹ h⁻¹, five times higher than that of commercial ZSM-5-supported bimetallic Ni–Co alloy catalysts. In addition, the selectivity for octadecane in the product reaches 88%, which is 13.4% higher than that of monometallic Ni/ZSM-5 catalysts. The remarkable enhanced hydrodeoxygenation performance of the bifunctional catalysts is attributed to the open mesoporous nanoarchitecture and the synergistic effects of uniformly dispersed Ni–Co alloy nanoparticles and abundant Brønsted acid sites exposed by the ZSM-5 nanosheets. This synthetic strategy paves a pathway toward the rational construction of hierarchically porous metal alloy/zeolite catalysts for diverse potential applications.