Multicomponent catalysis: Interfacial properties directing furfuryl alcohol hydrodeoxygenation pathways at doped TiO2-Pd core shell catalysts
Open Access
- Author:
- Weikel, Kelly
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Michael John Janik, Thesis Supervisor
Michael John Janik, Thesis Honors Advisor
Robert Rioux, Faculty Reader - Keywords:
- catalysis
hydrodeoxygenation
biomass
furfuryl alcohol
Density Functional Theory
vacancies - Abstract:
- 2-methylfuran (2-MF) is an emerging second-generation biofuel produced by hydrodeoxygenation (HDO) of hemicellulose-derived furfuryl alcohol (FA). Our research group has previously demonstrated that a TiO2-Pd catalyst provides interfacial active sites that favor selectivity for HDO of FA to 2-MF over de-carbonylation (DCO) of FA to furan. A TiO2 nanowire adsorbed atop an extended Pd(111) surface was developed as an atomistic model to represent the active site for HDO. Doping the TiO2-Pd nanowire, by substituting a portion of Ti cations with other metal cations, could alter the redox properties of the interface to further energetically favor HDO, resulting in greater 2-MF to furan selectivity. Using density functional theory (DFT) calculations, different cation-doped catalysts were investigated to understand influences of electronic perturbation at the TiO2-Pd interface. The optimal dopant would both lower the HDO activation energy barrier and also promote reduction (oxygen vacancy formation) to form active interfacial sites. Doping TiO2 favored the formation of active sites most favorably at the TiO2-Pd interface; when the nanowires were doped, active site formation was further favored. Oxygen vacancy formation energy was not found to be a reliable predictor of the HDO energy barrier, which indicates that dopants have more complex interactions in the TiO2 nanowire than simply altering reducibility. However, doping does significantly alter HDO reaction energy barrier; Cr, Mo, Rh, Ru, and V provide substantial reduction in HDO activation energy despite more favorable oxygen vacancy formation energies. Understanding the electronic interactions and reaction kinetics of FA to 2-MF over doped TiO2-Pd indicates that metal doping provides an additional design variable in catalyst design for increasing the selectivity towards HDO.