A DFT study of furan hydrogenation and ring opening on Pd(111)

Shengguang Wang,Dionisios G Vlachos,Vassili Vorotnikov

doi:10.1039/c3gc41183d

Shengguang Wang, Dionisios G Vlachos + Show 1 more

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https://doi.org/10.1039/c3gc41183d

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Journal: Green Chem.	Publication Date: Jan 1, 2014
Citations: 79	License type: cc-by

Affiliation: Center for Innovation, University of Delaware

Abstract

The reaction energies and the corresponding energy barriers of hydrogenation and ring opening of furan on Pd(111) for the formation of tetrahydrofuran (THF), 1-butanol and small hydrocarbons were studied using density functional theory (DFT). THF forms via sequential hydrogenation of carbon atoms of the furan ring in the order of α-carbon, adjacent β-carbon, second β-carbon, and the remaining α-carbon. Upon hydrogenation of the α-carbon of furan, ring opening becomes facile. Thus, hydrofuran (HF) is a reactive intermediate in both hydrogenation and ring opening. The fate of HF determines the selectivity of the overall reaction. A simple kinetic analysis indicates that coverage effects are important and the hydrogen partial pressure is a key factor in controlling selectivity. Dihydrofuran (DHF) was found to be a stable intermediate, consistent with experimental findings. Once DHF is formed, ring opening is not favored due to the high energy barriers of ring opening of DHF, trihydrofuran (TriHF) and THF. 1-Butanol is a thermodynamically favored product, while THF is kinetically preferred. Our theoretical work agrees well with experimental observations that 1-butanol is a major product at high temperatures whereas THF is a major product at low temperatures. Insights gained into selectivity toward ring hydrogenation and ring opening can assist future studies in catalyst selection.

Highlights

With increasing interest in renewable fuels, fuel additives, and chemicals, considerable attention has recently shifted toward furan derivatives, which can be obtained from sugars
A simple kinetic analysis reveals that coverage effects are important and the partial pressure of hydrogen is a critical factor in controlling the selectivity toward ring opening vs. further hydrogenation to DHF and THF
Once DHF is formed, ring opening is no longer likely because of the high energy barriers associated with ring opening of DHF, TriHF and THF

Summary

Introduction

With increasing interest in renewable fuels, fuel additives, and chemicals, considerable attention has recently shifted toward furan derivatives, which can be obtained from sugars. Xu performed DFT calculations for furan ring opening and dehydrogenation on Pd(111) up to CO formation.[5] It was found that the decomposition of furan begins with ring opening at the C–O bond, giving a C4H4O aldehyde species that rapidly loses the α-H to form C4H3O (see Fig. 1 for labeling of C atoms). Furan hydrogenation intermediates furfuryl alcohol is lower than that for decarbonylation to furan.[6] That work provided a detailed mechanism of the hydrogenolysis of furfural and its derivatives but did not consider the important problem of ring opening and hydrogenation. In order to understand ring hydrogenation and ring opening, in this paper, we perform DFT calculations for the first time on the mechanism of furan hydrogenation to THF and ring opening followed by decarbonylation to C3 species and CO or hydrogenation to butanol-1. Our calculations provide significant insights into the principles of selectivity control that can guide catalyst selection

Methods and models

Summary of reaction energetics and pathways

Conclusions