Collaborative Research: Rational design of bifunctional catalysts for the conversion of Ievulinic acid to gamma-valerolactone

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The modern petrochemical industry has achieved impressive efficiencies in meeting societaldemands through selective transformations of a few, key building block chemicals. A future self-sustaining biorefining industry will similarly be based on a selected platform of renewable building blocks which may yield transportation fuels or commodity and specialty chemicals. A recent study has identified 10 promising biomass derivatives that have the potential to serve as building blocks for future bio-refineries. Of those, Levulinic Acid (LA) is particularly promising as it can be produced inexpensively and in high yields by sulfuric acid hydrolysis of a variety of lignocellulosic feedstocks. Conversion processes of LA to fuel additives, chemicals, and monomers for plastics and textiles have been demonstrated, but not commercialized. A derived chemical, ?×-valerolactone (GVL), is a promising and extremely flexible intermediate, from which these same numerous desirable end-products can be obtained. Despite a myriad of applications for GVL, its large scale production is not yet established, owing largely to difficulties associated with the purification of its immediate precursor, LA.Professor Andreas Heyden from the University of South Carolina and Professor Jesse Q. Bond from Syracuse University believe these issues have solutions, and have received this NSF award to establish the underlying science that can make feasible the production of the lignocellulosic biomass-derived platform chemical GVL on a commercial scale. In the present state of the art, LA must undergo a costly purification scheme to remove residual sulfuric acid from cellulose hydrolysis prior to conversion to GVL. H2SO4 must be recovered and recycled, in line with a commitment to the long term sustainability of biorefining processes. GVL is sufficiently hydrophobic to allow an energy efficient separation from aqueous sulfuric acid by extraction with a low-boiling acetate followed by facile distillation. A catalytic approach to streamline this step has been proposed. However, the new challenge is the inadequacy of presently available HDO catalysts for processing of unrefined LA. Heyden and Bond propose to use a combined computational and experimental approach to obtain fundamental understanding of the reaction mechanism of the mild, heterogeneously catalyzed hydrodeoxygenation of LA to GVL over Ru/C and RuRe/C catalysts in both aqueous and dilute sulfuric acid solutions, leading to potential improved catalysts and thus making the entire strategy more industrially relevant.The fundamental objective of this project is to create a scientific basis for the rational design of novel heterogeneous catalysts with superior activity, selectivity, and stability for the HDO of LA to GVL in aqueous sulfuric acid. A successful outcome is broadly relevant in aqueous phase processing of lignocellulosic biomass. Further, success of the combined computational and experimental research approach illustrates that such a strategy not only increases our understanding of reaction mechanisms, but also reduces the time and financial resources needed for the design of new heterogeneous catalysts tailored to meet the changing needs of a world with limited resources. The PhD students involved in this project will become experts in the practice and integration of computational and experimental catalysis. Also, the research results will be incorporated into the elective classes ¡§Multiscale Modeling: From Electrons to Chemical Reactors¡¨ being taught by Heyden at the University of South Carolina and ¡§Heterogeneous Catalysis¡¨ being offered by Bond at Syracuse University.