Many important chemicals in use today are derived from non-renewable petroleum resources. An important example is butadiene, which is converted to synthetic rubber used in manufacture of tires. One approach to make tire manufacture more sustainable is to find a non-petroleum substitute for butadiene. Ethanol produced from renewable cellulosic biofuel and bio-refinery operations is potentially an alternative feedstock for synthetic rubber production, if a suitable catalyst to drive the conversion of ethanol to butadiene can be found. This project will seek fundamental understanding of the interaction of ethanol with metal oxide catalyst surfaces at the molecular level to discover the best type of catalyst and the optimal conditions needed to convert ethanol to butadiene. The proposed research has the potential to lead to a viable pathway to produce synthetic rubber from sustainable feedstocks with a lower carbon footprint. The educational activities associated with the project include international opportunities for student research at a renowned catalyst research institute in Germany, as well as the development of modules for outreach on sustainable chemicals and fuels.
The overall goal of the research is to elucidate the molecular level structure-reactivity/selectivity relationships for the catalytic conversion of bioethanol to butadiene. This goal will be accomplished through an integrated study of catalyst synthesis, spectroscopic analysis of surface chemistry, molecular calculations, and transient reaction kinetics analysis. A well-defined series of catalysts will be synthesized to explore the effects of the silica-supported active metal oxide phase domain size, local structure, oxidation state, acid-base-redox characteristics and interactions between the active metal oxides. The catalysts will be characterized at the molecular level with in situ and operando spectroscopy under reaction conditions. The ethanol surface chemistry will be probed with Temperature Programmed Surface Reaction (TPSR) spectroscopy, and isotopic labeling will assist in revealing the reaction pathways of specific molecular functionalities involving in the coupling reaction to yield butadiene. Steady State Isotopic Transient Kinetic Analysis (SSITKA) reaction studies will provide additional kinetic details about the reaction network and rate-determining-steps. The experimental findings will be complemented with theoretical calculations to get a deeper, molecular- level understanding of the active sites required for each catalytic step. All of this information will be combined to establish structure-activity/selectivity relationships to guide the molecular design of improved catalysts for the conversion of bioethanol to butadiene.
