Hydrodeoxygenation of guaiacol over orthorhombic molybdenum carbide: a DFT and microkinetic study

Kushagra Agrawal,Nanda Kishore,Alberto Roldan,Andrew J Logsdail

doi:10.1039/d1cy01273h

Kushagra Agrawal, Nanda Kishore + Show 2 more

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https://doi.org/10.1039/d1cy01273h

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Abstract

The hydrodeoxygenation of guaiacol is modelled over a (100) β-Mo2C surface using density functional theory and microkinetic simulations.

Highlights

In the quest for a viable renewable source of energy, biomass feedstocks have emerged as a strong contender because of the abundance of natural flora on the planet
The adsorption was conducted on 5 different sites on the surface (atop, bridge, fcc, Mo-hcp and Chcp, as illustrated in Figure 1(A)), with the adsorbed structures and energetics shown in Tables S1-S3 of the Supplementary Information (SI)
The strongest adsorption of guaiacol is via the aromatic ring over the C-hcp position of the surface, with an adsorption energy of -4.67 eV, which is at least 2.21 eV stronger than reported for the precious metal surfaces such as Ru (Eads = -2.46 eV)[53], Pd (Eads = -1.43 eV)[54] and Pt (Eads = -2.41 eV) 55; the adsorption energy for guaiacol on tungsten carbide is closer to our calculated results, having been previously reported as -3.04 eV, 56 though we note this is still 1.63 eV weaker than the molybdenum carbide

Summary

Introduction

In the quest for a viable renewable source of energy, biomass feedstocks have emerged as a strong contender because of the abundance of natural flora on the planet. Bio-oil obtained from the thermal treatment of biomass contains oxygen carrying compounds like guaiacol, anisole, and ferulic acid, and these oxy-compounds need to be reduced before being suitable as fuel 3 This is because the oxygen carrying compounds are known to provide unfavorable properties to the crude bio-oil (such as low pH, high viscosity, etc.), and reduce its energy density 4. Nørskov et al 8 have shown that the performance of a catalyst is significantly influenced by the electronic structure at its surface, with the position of the d-band center, relative to the Fermi level, identified as a suitable indicator of the materialsDOaId: 1s0o.1r0p3V9ite/iwDoA1nCrtiYcl0e1O2n7l3inHe strength and catalytic activity 9. Considering the valorization of biomass, the crude bio-oil obtained after fast pyrolysis has a relatively high concentration of guaiacol (5-15% of the phenolic fraction) 2 Guaiacol contains both a methoxy and a hydroxyl functional group, which represents most of the oxygencontaining functional groups in bio-oils. The thermochemistry of all the proposed reactions is presented (Section 3) and subsequently, microkinetic modelling is applied to determine the kinetic parameters (Section 4) of the upgrading process

Computational Details

Results and Discussions

Energy profile of the upgrading routes

Conclusions

Supporting Information