Size effect of Ru particles on the self-reforming-driven hydrogenolysis of a lignin model compound?

Catalysis Science & Technology Pub Date: 2022-06-27 DOI: 10.1039/D2CY00688J

Abstract

Particle size always has a great influence on catalytic performance. In this study, we investigated the size effect of Ru colloids on the self-reforming-driven hydrogenolysis of a lignin model compound by taking 4-(3-hydroxypropyl)-2-methoxyphenol (PG-OH) as the substrate and NiAl2O4 spinel as the support. This reaction provides a strategy to produce alkylphenols from lignin without the consumption of exogenous hydrogen. Three catalysts with different Ru particle sizes (Ru1.5, Ru2.6, and Ru3.3) were prepared, and the catalytic results showed that the reaction activity presented a volcanic curve with the increase in the Ru particle sizes, in which Ru2.6/NiAl2O4 possessed the best performance. Reaction pathway studies showed two different reaction routes over small (Ru1.5 and Ru2.6) and large (Ru3.3) Ru particles. The reforming-driven hydrogenolysis of the methoxy group dominated over small Ru particles, with 4-ethylphenol (4-EP) as the main product; while the hydrogenation of hydroxypropyl and hydrolysis of the methoxy group dominated over the larger particles, with 4-propylcatechin (4-PC) as the main product. Comprehensive investigations indicates the difference in catalytic performance came from the interaction between Ru colloids and the NiAl2O4 spinel support, which led to different Ruδ+/Ru0 ratios and finally changed the reaction routes or reaction rate in these three catalysts. This study proves that the particle size really affects catalytic reactions, and indeed, the self-reforming-driven hydrogenolysis of lignin (the model compound) to alkylphenols is structure-sensitive.

Graphical abstract: Size effect of Ru particles on the self-reforming-driven hydrogenolysis of a lignin model compound
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