Highly dispersed MoOx-Ru/C bimetallic catalyst for efficient hydrogenolysis of esters

Generating energy from renewable sources instead of fossil resources is pivotal for realizing a sustainable and carbon-neutral society. At present, biomass-derived transportation fuels have been produced at the level of nearly 2 million barrels per day (MBD). By 2030, this figure is expected to rise to about 6 MBD, accounting for nearly 6% of the consumed fuels. In this context, the hydrodeoxygenation (HDO) of plant oils or fats into liquid hydrocarbon biodiesel has attracted considerable attention in recent decades. Recently, bifunctional metal-acid catalysts have been developed and shown high catalytic performance for producing alkanes from plant oils or fats. However, high temperature (260 ℃) and abundant acid sites caused the formation of coke or hydrocracking reactions, which resulted in severe carbon loss. Although Ru-Mo bimetallic catalysts had shown intriguing performance for the hydrogenolysis of carboxylic acids, the structure-performance relationship remained unexplored and their attempts to upgrading long-chain fatty acids/esters or natural oils into diesel-range alkanes with high yields have not been successful due to the poor dispersion of both Ru and Mo species.

Recently, a research team led by Prof. Jianchun Jiang, Prof. Junming Xu (Institute of Chemical Industry of Forest Products) & Prof. Zupeng Chen (Nanjing Forestry University) reported a highly dispersed MoO_x-Ru/C bimetallic catalyst for the efficient hydrogenolysis of esters to alkanes under 150 ℃. The optimal catalyst exhibits >99% conversion of methyl stearate and 99% selectivity to diesel-range alkanes, reaching a high rate of up to 2.0 mmol g_cat^-1·h^-1, 5 times higher than that of the Ru/C catalyst (MoO_x/C is inert). The results were published in the Chinese Journal of Catalysis (DOI: 10.1016/S1872-2067(24)60254-8).

The catalyst containing a Mo/Ru molar ratio of 0.2 exhibited exceptional catalytic performance with almost full conversion of methyl stearate and 99% selectivity for diesel-range alkanes. Comprehensive experimental and theoretical analyses showed that such high HDO performance was mainly attributed to the unique synergistic effect between Ru and MoO_x species, in which the highly dispersed MoO_x brought abundant Brønsted and Lewis acid sites for promoting the conversion of esters into alkanes, while the adjacent Ru provided sufficient active hydrogen atoms for the HDO reaction. Compared with previously reported HDO catalytic systems of biomass-relevant esters, the as-prepared MoO_x-Ru/C bimetallic catalyst has the following advantages: (1) maximizing active interfaces for the hydrogenolysis of esters, and (2) mainly yielding HDO products without carbon loss by suppressing the hydrogenolysis activity of Ru towards C─C bonds. This study provides a facile and novel strategy for designing HDO catalysts with the atomic-scale active interface for the efficient hydrogenolysis of biomass-derived esters to alkanes.

About the journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top six journals in Applied Chemistry with a current SCI impact factor of 15.7.

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