(416f) Inhibition of Xylene Isomerization in the Cycloaddition of 2,5-Dimethylfuran and Ethylene for the Production of Renewable p-Xylene

Authors: 
Williams, C. L., Idaho National Lab
Chang, C. C., University of Massachusetts Amherst
Wiatrowski, M. R., University of Delaware
Fan, W., University of Massachusetts Amherst
Dauenhauer, P. J., University of Massachusetts Amherst



Increasing demand for renewable and domestic energy and materials has led to an accelerated research effort to develop biomass-derived fuels and chemicals. One sustainable feedstock for these renewable chemicals is sugars produced by the saccharification of biopolymers (e.g., cellulose, hemicellulose). The catalytic conversion of these sugars to commodity chemicals, like p-xylene (used in the production of PET plastics), is currently a research area of great interest [1,2].In previous work, the conversion of 2,5-dimethylfuran (DMF) and ethylene to p-xylene by a two-step reaction (Diels-Alder cycloaddition followed by dehydration), demonstrated a 75% yield of p-xylene [1].  This step completes the entire process of (a) glucose dehydration to hydroxymethylfurfural (HMF), (b) reduction of HMF to dimethylfuran, and (c) cycloaddition/dehydration of DMF to p-xylene.

In this work, diffuse reflectance infrared spectroscopy (DRIFTS) has shown competitive binding of DMF over p-xylene to the Brønsted acid sites located in the super and sodalite cages of H-Y faujasite. The persistence of these Brønsted acid sites after reaction has been shown through the use of 27Al-NMR.  Furthermore, the use of thermogravimetric analysis (TGA) indicates that DMF molecules can be adsorbed to Brønsted acid sites at a reaction temperature of 300 °C, while p-xylene will be completely desorbed. The combined use of DRIFTS, 27Al-NMR, and TGA, in addition to detailed isomerization inhibition experiments, has allowed us to elucidate the source of p-xylene isomerization inhibition during the production of renewable aromatics from furans.

References

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

[2] N. Nikbin, P.T. Do, S. Caratzoulas, R.F. Lobo, P.J. Dauenhauer, 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

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