(703f) Prediction and Screening of Product Distribution in Nanoporous Material-Catalyzed Propene Dimerization Via Molecular Simulations

Authors: 
Liu, M., University of California, Berkeley
Smit, B., École polytechnique fédérale de Lausanne
The ability to predict the product distribution of a nanoporous catalyst in silico would enable better understanding of catalyst structure-function relationships and advance discovery of more selective catalysts for industrially important reactions. One such reaction is the propene dimerization reaction, which yields a mixture of branched and linear C6 olefin isomers, of which the linear isomers are valued as industrial feedstocks for fuels and lubricants[1]. We have developed a conceptual framework based on shape selectivity theory[2] to explain and predict changes in the product distribution of the propene dimerization reaction resulting from the use of different zeolites and metal-organic frameworks (MOFs) as catalysts.

Using our model, experimentally observed changes in the product distribution from the literature[1] could be explained with quantitative agreement in terms of the contribution of the pores to the free energies of formation of the product isomers, which were computed using molecular simulations. We applied our model to screen a database of 118 existing and hypothetical MOF and zeolite structures to study how product distribution could be tuned by changing pore size, shape, and composition of porous materials. The screening identified a few not-yet-synthesized materials with improved linear isomer selectivity compared to experimentally identified catalysts, and determined catalyst properties that enhanced selectivity toward the valued linear olefin isomers, such as presence of open metal sites. This molecular picture of the mechanisms influencing product distribution provides insights for prediction and rational design of improved catalyst materials.

[1] Mlinar, A. N.; Keitz, B. K.; Gygi, D.; Bloch, E. D.; Long, J. R.; Bell, A. T. ACS Catal. 2014, 4, 717–721.

[2] Smit, B.; Maesen, T. L. M. Nature 2008, 451, 671–678.