The growing focus on biofuels globally has led to a significant amount of glycerol production with no current economic value. Various catalytic process classes are hunting for potential ways to transform glycerol into valuable compounds with industrial interests. Glycerol can be oxidized to produce valuable C3 products such as dihydroxyacetone (DHA) and glyceraldehyde (GLD); however, these face a substantial selectivity challenge between various C1, C2, and C3 oxidation derivatives due to the multifunctional nature of glycerol. Despite the development of new heterogeneous catalytic processes for glycerol conversion, the atomistic understanding between reaction pathways and catalyst structure is limited. Recent theoretical models offer effective tools to unveil the introductory chemistry in selective glycerol oxidation on various metal nanoparticles and can be utilized to design novel selective catalysts. In this work, we utilize density functional theory (DFT) calculations to elucidate glycerol oxidation mechanisms yielding GLD and DHA on transition metal catalysts. We observe that (111) and (100) crystal facets promote glycerol decomposition via different C-H/O-H bond scission pathways, suggesting the structure sensitivity of glycerol oxidation. Comparisons of the relative stabilities of dehydrogenated intermediates along with detailed activation energy barriers for dehydrogenation together offer insights into the nature of the selectivity challenge. Moreover, leveraging a modified scaling method based on metal stability, we show that glycerol reactivity can be described as a function of surface structure, enabling prediction of reaction energetics on nanoparticle models with improved computational efficiency. We finally highlight the importance of considering co-adsorbed oxygen species presence that shows a significant enhancement in dehydrogenation energetics and kinetics due to stabilization of glycerol on the catalyst surface. Together, these insights offer strategies by which the selective formation of GLD or DHA may be realized.

Structure-sensitive catalytic glycerol oxidation on late transition metals

ACS Spring Meeting 2021

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