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

Authors: 
Fan, W., University of Massachusetts Amherst
Chang, C. C., University of Massachusetts Amherst
Green, S. K., University of Massachusetts Amherst
Williams, C. L., Idaho National Lab
Dauenhauer, P., University of Massachusetts Amherst



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.

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