(266c) Cycloaddition of Biomass Derived Furans for the Renewable Production of p-Xylene

Increasing demand for domestic energy and renewable materials
has led to an accelerated research effort to develop biomass-derived fuels and chemicals
[1]. One sustainable feedstock for
these renewable chemicals is sugars produced by the saccharification of
biopolymers (e.g., cellulose, hemicellulose) [2]. The catalytic conversion of
sugars to high value commodity chemicals, like p-xylene (used in the production
of PET plastics [3]), is currently a research area of interest [4]. In this
work, we investigate the conversion of dimethylfuran to p-xylene by a
two-part reaction (Diels-Alder cycloaddition followed by dehydration).  By
reacting dimethylfuran with high-pressure ethylene, competitive side reactions
that reduce p-xylene yield are identified and minimized. Multiple
catalyst types are investigated providing insight into the relevant catalyst active
sites and microstructure. 75% yield of p-xylene is demonstrated using Y-zeolite
in combination with an aliphatic solvent at high temperature.  Additionally, it
is found that Diels-Alder cycloaddition (the first step in conversion of DMF to
p-xylene) is promoted by confinement within microstructured
zeolites and the second step (dehydration) is catalyzed by Brønsted acid sites,
rendering the first step (cycloaddition) rate limiting. Gas phase DFT
calculations supporting the necessity of Brønsted acid sites are also
presented. This catalytic system introduces a new chemical pathway to convert
biomass-derived furans to high-value aromatic feedstocks.

References:

[1] Climent, M. J.; Corma, A.; Iborra, S. Green Chemistry 2011,
13, 520-540

[2] Vlachos, D. G.; Chen, J. G.; Gorte, R. J.; Huber, G. W.; Tsapatsis,
M. Catalysis Letters 2010, 140, 77-84.

[3] Sheehan, R. J. In Ulmann's
Encyclopedia of Industrial Chemistry; Wiley-VCH Verlag GmbH & Co. KGaA,
Weinheim, 2011; pp. 17-28

[4] 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