Tailoring the Electronic Ru-Al₂O₃ Interaction to Regulate Reaction Barriers for Selective Hydrogenolysis of Aromatic Ether

Abstract

Aromatics are desirable products from the depolymerization/valorization of lignin; however, it is still challenging to achieve selective hydrogenolysis of the C–O bond with the preservation of aromatic rings. In this work, the electronic Ru-Al2O3 interaction was tailored by controlling the sizes of supported Ru nanoparticles to regulate the profiles of energy barriers for selective hydrogenolysis of diphenyl ether (DPE, modeling compound of lignin). Complementary characterizations and kinetic studies demonstrate that a stronger electronic metal–support interaction (EMSI) occurs between smaller Ru nanoparticles and Al2O3, leading to a more electron-deficient Ru domain. This tailored electronic structure dramatically increases the barrier of an undesired secondary reaction (i.e., ring hydrogenation), outstripping that of DPE hydrogenolysis for the production of aromatics. In addition, although the latter barrier also increases over smaller and more electron-deficient Ru, the much more abundant active site compensates for the increased barrier and enhanced the apparent reactivity. The catalyst bearing the smallest Ru particle displays the highest activity and selectivity under the tested conditions. This work provides an approach to control selectivity in hydrotreatment by regulating the energy barriers along the reaction pathway.

Photocatalytic transfer hydrogenolysis of aryl ethers

“…The 4-O-5 linkage is one of the basic and most inert linkages in lignin, and its cleavage has drawn considerable attention. [6][7][8][9][10][11] Well-designed molecular catalysts and heterogeneous catalysts have been developed to break the 4-O-5 linkage via hydrogenolysis under a H 2 atmosphere, [12][13][14][15][16][17][18][19] and in particular, much effort has been devoted to realizing this transformation under mild conditions, such as additivefree, low-pressure H 2 , and low-temperature conditions. [20][21][22][23][24][25][26][27][28] The transfer hydrogenation strategy utilizes biomass-derived alcohols, carboxylic acids, and even water as hydrogen donors, avoiding the use of hydrogen gas.…”