Biomass conversion to biofuels and value-added chemicals has been receiving increased attention in recent years. Due to the large number of functional groups in biomass, its utilization is rather complex and therefore hard to understand and optimize. In this work, we use several simple glycols, such as ethylene glycol and 1,2- and 1,3-propylene glycols, as biomass surrogates, and probe their conversion on a model reducible oxide surface, rutile TiO2(110). For ethylene and 1,2-propylene glycols, two reaction channels are observed: one leading to alkenes, the other to aldehydes/ketones. The alkene formation dominates at low glycol coverages, while the aldehydes and ketones are primarily observed at high coverages. For 1,3-propylene glycol, an additional C-C cleavage channel yielding formaldehyde and ethylene, and a disproportionation channel yielding 1-propanol and acrolein are observed. At high coverages, the carbon containing products are accompanied by hydrogen. This is in sharp contrast to alcohols, from which only water is observed. Experiments with OD-labelled glycols show that hydrogen originates exclusively from the glycol hydroxyl groups. Increasing the steric hindrance around the OD groups by methyl side groups is found to inhibit and eventually eliminate hydrogen formation. Damaging the surface order or scavenging the available surface charge of TiO2(110) are also shown to completely suppress hydrogen formation. Combined, these results suggest that hydrogen formation results from proximal glycol pairs, and that the redox reaction is driven by defect electrons of TiO2(110).

Glycols as models for biomass: Surface chemistry and mechanism of hydrogen formation on rutile TiO<sub>2</sub>(110)

248th National Meeting (2014)

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Glycols as models for biomass: Surface chemistry and mechanism of hydrogen formation on rutile TiO2(110)

Glycols as models for biomass: Surface chemistry and mechanism of hydrogen formation on rutile TiO₂(110)