Ab Initio Surface Phase Diagrams for Coadsorption of Aromatics and Hydrogen on the Pt(111) Surface

Glen A. Ferguson, Vassili Vorotnikov, Nicholas Wunder, Jared Clark, Kenny Gruchalla, Timothy Bartholomew, David J. Robichaud, Gregg T. Beckham

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Supported metal catalysts are commonly used for the hydrogenation and deoxygenation of biomass-derived aromatic compounds in catalytic fast pyrolysis. To date, the substrate-adsorbate interactions under reaction conditions crucial to these processes remain poorly understood, yet understanding this is critical to constructing detailed mechanistic models of the reactions important to catalytic fast pyrolysis. Density functional theory (DFT) has been used in identifying mechanistic details, but many of these works assume surface models that are not representative of realistic conditions, for example, under which the surface is covered with some concentration of hydrogen and aromatic compounds. In this study, we investigate hydrogen-guaiacol coadsorption on Pt(111) using van der Waals-corrected DFT and ab initio thermodynamics over a range of temperatures and pressures relevant to bio-oil upgrading. We find that relative coverage of hydrogen and guaiacol is strongly dependent on the temperature and pressure of the system. Under conditions relevant to ex situ catalytic fast pyrolysis (CFP; 620-730 K, 1-10 bar), guaiacol and hydrogen chemisorb to the surface with a submonolayer hydrogen (∼0.44 ML H), while under conditions relevant to hydrotreating (470-580 K, 10-200 bar), the surface exhibits a full-monolayer hydrogen coverage with guaiacol physisorbed to the surface. These results correlate with experimentally observed selectivities, which show ring saturation to methoxycyclohexanol at hydrotreating conditions and deoxygenation to phenol at CFP-relevant conditions. Additionally, the vibrational energy of the adsorbates on the surface significantly contributes to surface energy at higher coverage. Ignoring this contribution results in not only quantitatively, but also qualitatively incorrect interpretation of coadsorption, shifting the phase boundaries by more than 200 K and ∼10-20 bar and predicting no guaiacol adsorption under CFP and hydrotreating conditions. The implications of this work are discussed in the context of modeling hydrogenation and deoxygenation reactions on Pt(111), and we find that only the models representative of equilibrium surface coverage can capture the hydrogenation kinetics correctly. Last, as a major outcome of this work, we introduce a freely available web-based tool, dubbed the Surface Phase Explorer (SPE), which allows researchers to conveniently determine surface composition for any one- or two-component system at thermodynamic equilibrium over a wide range of temperatures and pressures on any crystalline surface using standard DFT output. (Graph Presented).

Original languageEnglish (US)
Pages (from-to)26249-26258
Number of pages10
JournalJournal of Physical Chemistry C
Volume120
Issue number46
DOIs
StatePublished - Nov 23 2016
Externally publishedYes

Fingerprint

Phase diagrams
Hydrogen
Guaiacol
phase diagrams
hydrogen
deoxygenation
Hydrogenation
Density functional theory
hydrogenation
Pyrolysis
pyrolysis
Aromatic compounds
Adsorbates
aromatic compounds
density functional theory
Thermodynamics
hydrogen compounds
Phase boundaries
upgrading
Phenol

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

Ferguson, G. A., Vorotnikov, V., Wunder, N., Clark, J., Gruchalla, K., Bartholomew, T., ... Beckham, G. T. (2016). Ab Initio Surface Phase Diagrams for Coadsorption of Aromatics and Hydrogen on the Pt(111) Surface. Journal of Physical Chemistry C, 120(46), 26249-26258. https://doi.org/10.1021/acs.jpcc.6b07057

Ab Initio Surface Phase Diagrams for Coadsorption of Aromatics and Hydrogen on the Pt(111) Surface. / Ferguson, Glen A.; Vorotnikov, Vassili; Wunder, Nicholas; Clark, Jared; Gruchalla, Kenny; Bartholomew, Timothy; Robichaud, David J.; Beckham, Gregg T.

In: Journal of Physical Chemistry C, Vol. 120, No. 46, 23.11.2016, p. 26249-26258.

Research output: Contribution to journalArticle

Ferguson, GA, Vorotnikov, V, Wunder, N, Clark, J, Gruchalla, K, Bartholomew, T, Robichaud, DJ & Beckham, GT 2016, 'Ab Initio Surface Phase Diagrams for Coadsorption of Aromatics and Hydrogen on the Pt(111) Surface', Journal of Physical Chemistry C, vol. 120, no. 46, pp. 26249-26258. https://doi.org/10.1021/acs.jpcc.6b07057
Ferguson GA, Vorotnikov V, Wunder N, Clark J, Gruchalla K, Bartholomew T et al. Ab Initio Surface Phase Diagrams for Coadsorption of Aromatics and Hydrogen on the Pt(111) Surface. Journal of Physical Chemistry C. 2016 Nov 23;120(46):26249-26258. https://doi.org/10.1021/acs.jpcc.6b07057
Ferguson, Glen A. ; Vorotnikov, Vassili ; Wunder, Nicholas ; Clark, Jared ; Gruchalla, Kenny ; Bartholomew, Timothy ; Robichaud, David J. ; Beckham, Gregg T. / Ab Initio Surface Phase Diagrams for Coadsorption of Aromatics and Hydrogen on the Pt(111) Surface. In: Journal of Physical Chemistry C. 2016 ; Vol. 120, No. 46. pp. 26249-26258.
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