Mechanistic origins of accelerated hydrogenation of mixed alkylaromatics by synchronised adsorption over Rh/SiO2

Nikolay Cherkasov; Shusaku Asano; Yuta Tsuji; Kazuki Okazawa; Kazunari Yoshizawa; Hiroyuki Miyamura; Jun-ichiro Hayashi; Alexander A. Kunitsa; S. David Jackson

doi:10.1039/D3RE00032J

Mechanistic origins of accelerated hydrogenation of mixed alkylaromatics by synchronised adsorption over Rh/SiO₂

Nikolay Cherkasov,*^ab Shusaku Asano,

*^c Yuta Tsuji,

^e Kazuki Okazawa,^d Kazunari Yoshizawa,

^d Hiroyuki Miyamura,^f Jun-ichiro Hayashi,^c Alexander A. Kunitsa^g and S. David Jackson

^h

Author affiliations

* Corresponding authors

^a School of Engineering, University of Warwick, Coventry, UK

^b Stoli Chem Ltd, Wellesbourne Campus, Wellesbourne, Coventry, UK
E-mail: n.cherkasov@stolichem.com

^c Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8580, Japan
E-mail: shusaku_asano@cm.kyushu-u.ac.jp

^d Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan

^e Faculty of Engineering Sciences, Kyushu University, Kasuga 816-8580, Japan

^f Interdisciplinary Research Center for Catalytic Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan

^g Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

^h Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK

Abstract

Catalytic reactions of mixed substrates sometimes behave differently from those of individual substrates. For example, the hydrogenation of propylbenzene over Rh/SiO₂ proceeds 120% faster in the presence of toluene. Such an acceleration effect does not agree with the well-accepted Langmuir–Hinshelwood reaction model. In this paper, we examined its mechanism experimentally and computationally. The hydrogenation experiment of vaporised aromatics confirmed that the acceleration was specific to the liquid phase with the isopropanol solvent. Direct adsorption measurements revealed that toluene adsorption synchronises with propylbenzene adsorption. Density functional theory calculations confirmed the associates of toluene and propylbenzene on the catalyst surface in the polar environment. The formation of associates increased the adsorption energy of toluene and decreased that of propylbenzene. Lowered adsorption energy reduces the activation barrier for catalytic reaction and intensifies the reaction rate beyond the Langmuir–Hinshelwood model prediction.

Reaction Chemistry & Engineering

Mechanistic origins of accelerated hydrogenation of mixed alkylaromatics by synchronised adsorption over Rh/SiO₂

Abstract

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Mechanistic origins of accelerated hydrogenation of mixed alkylaromatics by synchronised adsorption over Rh/SiO₂

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