p-Xylene, the precursor for PET bottles, was synthesized at 90% yield by [4 + 2] cycloaddition of biomass-derived ethylene and dimethylfuran followed by subsequent dehydration with Beta zeolite. Scheme 1 Diels-Alder cycloaddition of dimethylfuran [1] and ethylene produces an oxa-norbornene cycloadduct [2] which dehydrates to p-xylene [3]. Water hydrolyzes dimethylfuran [1] to 2,5-hexanedione [4] in equilibrium. † Electronic supplementary information (ESI) available. See

Renewable production of p-xylene from [4 + 2] Diels− Alder cycloaddition of 2,5-dimethylfuran (DMF) and ethylene with H−Y zeolite catalyst in n-heptane solvent is investigated. Experimental studies varying the solid acid catalyst concentration reveal two kinetic regimes for the p-xylene production rate: (i) a linear regime at low acid site concentrations with activation energy E a = 10.8 kcal/mol and (ii) a catalyst-independent kinetic regime at high acid site concentrations with activation energy E a = 20.1 kcal/mol. We carry out hybrid QM/MM calculations with a three-layer embedded cluster ONIOM model to compute the energetics along the main reaction pathway, and a microkinetic model is constructed for the interpretation of the experimental kinetic data. At high solid acid concentrations, p-xylene production is limited by the homogeneous Diels−Alder reaction, whereas at low acid concentrations, the overall rate is limited by the heterogeneously catalyzed dehydration of the Diels−Alder cycloadduct of DMF and ethylene because of an insufficient number of acid sites, despite the dehydration reaction requiring significantly less activation energy. A reduced kinetic model reveals that the production of p-xylene follows the general kinetics of tandem reactions in which the first step is uncatalyzed and the second step is heterogeneously catalyzed. Reaction orders and apparent activation energies of quantum mechanical and microkinetic simulations are in agreement with experimental values.

The electrocatalytic hydrogenation of biomass derived oxygenates in a continuous electrocatalytic membrane reactor presents a promising method of fuel and chemical production that minimizes usage of solvents and has the potential to be powered using renewable electricity. In this paper we demonstrate the use of a continuous-flow electrocatalytic membrane reactor for the reduction of aqueous solutions of furfural into furfuryl alcohol (FA), tetrahydrofurfuryl alcohol (THFA), 2-methylfuran (MF) and 2-methyltetrahydrofuran (MTHF). Protons needed for hydrogenation were obtained from the electrolysis of water at the anode of the reactor. Pd was identified as the most active monometallic catalyst of 5 different catalysts tested for the hydrogenation of aqueous furfural with hydrogen gas in a high-throughput reactor.Thus Pd/C was tested as a cathode catalyst for the electrocatalytic hydrogenation of furfural. At a power input of 0.1W, Pd/C was 4.4 times more active ( per active metal site) as a cathode catalyst in the electrocatalytic hydrogenation of furfural than Pt/C. The main products for the electrocatalytic hydrogenation of furfural were FA (54-100% selectivity) and THFA (0-26% selectivity). MF and MTHF were also detected in selectivities of 8%. Varying the reactor temperature between 30 °C and 70 °C had a minimal effect on reaction rate for furfural conversion. Using hydrogen gas at the anode, in place of water electrolysis, produced slightly higher rates of product formation at a lower power input. Sparging hydrogen gas on the cathode had no effect on reaction rate or selectivity, and was used to examine the addition of recycling loops to the continuous electrocatalytic membrane reactor. † Electronic supplementary information (ESI) available. See