(47a) Ultra-Selective Cycloaddition of Dimethylfuran for Renewable p-Xylene

The need for sustainable production of everyday materials in addition to market volatility of petroleum-based feedstocks has motivated research into the production of renewable aromatic chemicals from biomass. Specific chemicals of interest include p-xylene, the feedstock for polyethylene terephthalate (PET). We have proposed a renewable method of producing renewable p-xylene by cycloaddition of biomass-derived dimethylfuran (DMF) and ethylene, which serves as the last step in a complete process for producing p-xylene from cellulose [1,2]. Further investigation into the design of this process indicates potential for economic viability, and sensitivity analysis of considered process parameters highlights the need for improved selectivity to p-xylene in the conversion of DMF [3].

In this work we highlight enhanced selectivity to p-xylene from the reaction of DMF and ethylene using H-BEA catalyst in heptane solvent. High selectivity to p-xylene (~90%) can be achieved when the conversion of DMF increases to >99%.  It is shown that 2,5-hexanedione, formed by the hydrolysis of DMF in the initial stage of the reaction (conversion of DMF <60%), can reform DMF to maintain the equilibrium between DMF/water and 2,5-hexanedione, which significantly improves overall selecitivty to p-xylene. This study reveals that the superior performance of H-BEA for selective production of p-xylene can be attributed to: (a) its resistance to deactivation, allowing for high conversion of DMF, (b) its superior activity relative to other solid-acid catalysts, and (c) its ability to catalyze dehydration of the Diels-Alder cycloadduct without catalyzing important side reactions. It is also found that p-xylene, once formed from DMF, does not readily isomerize to o- or m-xylene at the considered reaction conditions, which provides a significant process advantage by eliminating the expensive separation of xylene isomers. The discovery that H-BEA in heptane exhibits high selectivity with high catalytic reaction rate significantly improves the potential for lignocellulosic biomass to serve as a renewable feedstock for aromatic chemicals.

Reference:

[1] C. L. Williams, C.-C. Chang, P. Do, N. Nikbin, S. Caratzoulas, D. G. Vlachos, R. F. Lobo, W. Fan and P. J. Dauenhauer, ACS Catal., 2012, 2, 935-939

[2] N. Nikbin, P.T. Do, S. Caratzoulas, R.F. Lobo, P.J. Dauenhauer and D.G. Vlachos, “A DFT study of the acid-catalyzed conversion of 2,5-dimethylfuran and ethylene to p-xylene,” Journal of Catalysis 2013, 297, 35-43.

[3] Z. Lin, M. Ierapetritou and V. Nikolakis, AIChE Journal, 2013, in press. DOI:10.1002/aic.13969.