Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt-Hydroxyapatite Catalyst

Wang, Q.-N. and Weng, X.-F. and Zhou, B.-C. and Lv, S.-P. and Miao, S. and Zhang, D. and Han, Y. and Scott, S.L. and Schüth, F. and Lu, A.-H.

Volume: 9 Pages: 7204-7216
DOI: 10.1021/acscatal.9b02566
Published: 2019

Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-derived aromatic hydrocarbons suffer from low selectivity due to facile overoxidation reactions which produce aromatic aldehydes, acids, and esters. Here we report a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol directly to methylbenzyl alcohols (MB-OH, predominantly 2-MB-OH) at 325 °C. The dehydrogenation of ethanol to acetaldehyde, which is catalyzed by Co2+, has the highest reaction barrier. Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms the key intermediate, 2-butenal, which yields aromatic aldehydes through self-condensation and then MB-OH via hydrogenation. In the presence of Co2+, 2-butenal is selectively hydrogenated to 2-butenol. This reaction does not hinder aromatization because cross-coupling between 2-butenal and 2-butenol leads directly to MB-OH without passing through MBâ•O. Using these insights a dual-bed catalyst configuration was designed for use in a single reactor to improve the aromatic alcohol selectivity. Its successful use supports the proposed reaction mechanism. Copyright © 2019 American Chemical Society.

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