(416e) Production of Dimethylfuran From Hydroxymethylfurfural Through Catalytic Transfer Hydrogenation With Ruthenium Supported On Carbon

The hydrogenation of biomass-derived 5-(hydroxymethyl) furfural (HMF) to 2,5-dimethylfuran (DMF) is a key reaction in upgrading biomass derived furanic compounds into platform molecules toward the production of chemicals and liquid transportation fuels. For instances, DMF itself can be used as a gasoline additive or further upgraded into p-xylene through Diels-Alder reaction with ethylene. The hydrogenation of HMF to DMF has been studied over various metal catalysts (Cu, Pd, Ni, and Ru) using molecular hydrogen [1-4]. Copper-based catalysts, carbon supported copper-ruthenium and copper chromite, have been identified as the best metal for selective production of DMF (71% yield) [1]. However, hydrogenation utilizing petroleum-derived H₂ is neither entirely green nor economic because it requires high-pressure H₂ increasing process costs. In this study we introduce an alternative route for the conversion of HMF to DMF through catalytic transfer hydrogenation (CTH) where a hydrogen donor is used as a hydrogen source, instead of molecular H₂.

            We have investigated the CTH of HMF using secondary alcohols and show that DMF is selectively produced with up to 80% yield over a carbon-supported Ru catalyst. Initial reaction kinetic studies were performed using 2-propanol (Isopropyl alcohol(IPA)) as a hydrogen donor in a batch reactor. It was found that the CTH reaction occurs at reaction temperatures lower than 373 K and the selectivity of the DMF increases with increasing reaction temperature. At low temperatures, the primary product is 2,5-bis(hydroxymethyl)furan (BHMF) and upon increasing the reaction temperature to 463 K, BHMF is completely converted with a selectivity to DMF of up to 81%. The main by-products detected are those formed through etherification of BHMF or 5-methyl furfuryl alcohol (MFA) with IPA. However, these ethers are slowly converted into DMF, especially at higher temperatures (e.g. 463 K). During the CTH reaction, H₂ needed for hydrogenation of HMF is supplied from dehydrogenation of IPA. We have found that dehydrogenation of IPA to acetone and H₂ is a faster reaction than hydrogenation of HMF. The acetone yield reaches chemical equilibrium with the carbon yield of 11.5% at 463 K after 1 hour while the corresponding H₂ partial pressure is 0.95 MPa in the closed reactor. Importantly, the hydrogen transfer hydrogenation of HMF to DMF can be carried out with other hydrogen donors, including 1-propanol, 1-butanol, and 2-butanol. XRD and TEM analyses of the fresh and spent catalysts showed the presence of Ru metal particles. The active site of the catalyst has been identified with a series of experiments. Overall, our work suggests that the catalytic transfer hydrogenation can be a vial route to upgrade other biomass-derived molecules in an efficient and sustainable way without utilizing petroleum-derived H₂.

[1] Y. Roman-Leshkov, C.J. Barrett, Z.Y. Liu, J.A. Dumesic, Nature, 447 (2007) 982-U985.

[2] S. Sitthisa, T. Sooknoi, Y.G. Ma, P.B. Balbuena, D.E. Resasco, J. Catal., 277 (2011) 1-13.

[3] S. Sitthisa, D.E. Resasco, Catal. Lett., 141 (2011) 784-791.

[4] J.P. Lange, E. van der Heide, J. van Buijtenen, R. Price, ChemSusChem, 5 (2012) 150-166.