Low‐Temperature Catalytic Hydrogenolysis of Guaiacol to Phenol over Al‐Doped SBA‐15 Supported Ni Catalysts

Abstract

Abstract Selective hydrogenolysis of aromatic carbon‐oxygen (C aryl −O) bonds is a key strategy for the generation of aromatic chemicals from lignin. However, this process is usually operated at high temperatures and pressures over hydrogenation catalysts, resulting in a low selectivity for aromatics and an extra consumption of hydrogen. Here, a series of Al‐doped SBA‐15 mesoporous materials with different Si/Al molar ratios (Al‐SBA‐15) were prepared via a post‐synthesis method using NaAlO 2 as the Al source, and then Al‐SBA‐15 supported Ni catalysts (Ni/Al‐SBA‐15) were prepared by a deposition‐precipitation method using urea as the hydrolysis reagent. The prepared supports and catalysts were extensively characterized using various techniques such as XRD, N 2 adsorption/desorption, TEM, 27 Al NMR, NH 3 ‐TPD, XPS, H 2 ‐TPR, and pyridine‐FT‐IR, and the catalysts were evaluated in the hydrogenolysis of the C aryl −O bond in guaiacol and lignin derived compounds under mild conditions. The effects of the Si/Al ratio in catalyst and reaction parameters on guaiacol conversion and product distribution were investigated in detail, associated with solvent effect. The incorporation of Al into the framework of SBA‐15 can improve the Lewis acidity and the dispersion of the supported Ni particles and yet modulate the metal‐support interactions, which are propitious to the hydrogenolysis of the C aryl −O bond in guaiacol. The catalyst Ni/Al‐SBA‐15 with a Si/Al molar ratio of 10 shows the best performance with a guaiacol conversion of 87.4 % and a phenol selectivity of 76.9 % under the mild conditions conducted, because of its proper acidity, suitable metal‐support interactions, and high dispersion of the active species. The present study would stimulate research and development in multi‐functional catalysts for the generation of valuable chemicals from biomass.

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