DFT Investigation of Isomeric Butanol Reactivity on TiO₂/Au(111) Catalysts

In this presentation we explore isomer effects on the reactivity and selectivity of butanol, a biofuel that can be utilized to minimize global fossil fuel reliance, over a heterogeneous model catalyst. Temperature-programmed desorption (TPD) experiments demonstrate that 1-butanol shows little reactivity and produces only elimination products while 2-butanol has higher reactivity and produces both oxidation and elimination products. To gain an atomically-detailed perspective on these processes, we used density-functional theory (DFT) to investigate energetic trends and identify comparisons between 1- and 2-butanol as they adsorb on Ti₃O_x nanoparticles supported on a Au(111) surface. There are two favorable interactions between the butanol and the catalyst material; the oxygen on butanol covalently bonds to the nanoparticle and the alkane chain interacts with the gold surface through dispersion forces. DFT calculations conclude that more active sites are available for 2-butanol to interact favorably with both the nanoparticle and the gold surface compared to 1-butanol. Preliminary calculations of the reaction pathways for butanol elimination and oxidation indicate that the binding geometry of 2-butanol with the catalyst surface is also more favorable for oxidation relative to 1-butanol. These computational results support the experimentally observed differences between butanol isomers in both reactivity and selectivity, providing insight into design of more efficient catalysts.