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. 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.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.

Ultraselective cycloaddition of dimethylfuran for renewable p-xylene with H-BEA zeolite

248th National Meeting (2014)

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