Predictive Multi-Scale Modeling of Base Catalysis in Functionalized Zeolites

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Proposal Title: Predictive Multi-Scale Modeling of Base Catalysis in Functionalized Zeolites Proposal Number: CTS-0553577 Principal Investigator: Scott M Auerbach Institution: University of Massachusetts Amherst The coming paradigm shift from fossil fuels to biofuels - those derived from renewable biomass - requires significant research into new catalysts that selectively transform biomass to biofuels. Efficient biorefining requires shape-selective catalysts with strong basic sites, because of the significant oxygen content in biomass. Although standard zeolites contain weak base sites, functionalized zeolites offer strong base sites by replacing zeolite oxygens with bridging amine (NH) groups. Initial calculations conducted in the principal investigator's group suggest that base-catalyzed reactions are faster by a factor of 100,000 at room temperature by substituting amine groups into zeolites. As interest in amine-substituted zeolites continues to grow, several fundamental questions remain, which can be addressed by molecular modeling: What is the maximum basicity attainable by amine-substituted zeolites? How is catalytic activity in these functionalized zeolites influenced by ion exchange? This project will assess the relative base strengths of several zeolites (various frameworks and compositions) with and without amine substitution, by computing adsorption energies of various Lewis-acid guest molecules. Quantum chemical energy calculations will be performed on embedded clusters in collaboration with scientists at Gaussian, Inc. The research will establish convergence of these energy calculations by comparing 2-layer and 3-layer embeddings with fully periodic quantum calculations. The calculations conducted in this research project will provide performance estimates for a burgeoning class of new catalysts: amine-substituted zeolites. This will assist zeolite chemists in the design and fabrication of advanced catalysts for biorefining applications. The collaboration with experimentalist C. Grey will help validate the theoretical predictions, and the collaboration with Gaussian, Inc. will lead to benchmarked software for the entire catalysis community to use for modeling reactions in zeolites. The research will be disseminated widely, especially through high school lectures entitled "High Octane Computing." Undergraduates and graduate students will be recruited from under-represented groups through two NSF-funded University of Massachusetts organizations: the Louis Stokes Alliances for Minority Participation, and the Northeast Alliance for Graduate Education. The broadest technical impact of this research translates to energy: shape-selective basic zeolites are important for catalyzing the future of biofuels.