Hydrodeoxygenation of HMF over Pt/C in a continuous flow reactor

Abstract

The three-phase hydrodeoxygenation reaction of 5-hydroxymethylfurfural (HMF) with H 2 was studied over a 10 wt % Pt/C catalyst using both batch and flow reactors, with ethanol, 1-propanol, and toluene solvents. The reaction is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products. These intermediate products then form dimethyl furan (DMF), which in turn reacts further to undesired products. Furfuryl ethers were found to react to DMF much faster than HMF, explaining the higher reactivity of HMF when alcohol solvents were used. With the optimal residence time, it was possible to achieve yields approaching 70% in the flow reactor with the Pt/C catalyst. Much higher selectivities and yields were obtained in the flow reactor than in the batch reactor because side products are formed sequentially, rather than in parallel, demonstrating the importance of choosing the correct type of reactor in catalyst screening.

Base metal-Pt alloys: A general route to high selectivity and stability in the production of biofuels from HMF

“…The fact that the D products form at the same space times for which DMF yields begin to decrease suggests that they are formed from DMF. The major D product observed with the Pt 6 Ni/C catalyst was 2-hexanone, the same major product formed on Pt catalysts [8,22], while with PtNi/C 2,5-hexandione was observed, which was also the primary product formed on Ni/C catalysts [8].…”

“…It is not likely that the higher yields are due to the increase in temperature. In addition to the fact that previous work indicated that selectivities are not very different between 100 and 200 °C [11,22], one would expect the reaction of DMF to over-hydrogenated products to increase with temperature. The maximum in the yield as a function of space time in Figure 6 is clearly less steep than that found for Pt 6 Ni/C and PtNi/C catalysts.…”

“…All these intermediates can react further to form DMF (C), which in turn reacts to overhydrogenated products (D), such as DMTHF 2-hexanone, 2-hexanol, 2,5-hexanedione, and their etherification derivatives, 1-propoxy-1-methylpentane (2-propoxyhexane) and 1,4-dipropoxy-1,4-dimethylbutane (2,5-dipropoxyhexane). All of the studied monometallic catalysts, including carbon-supported Pt, Pd, Ir, Ru, Co, and Ni, were found to exhibit relatively poor selectivity for DMF formation [8,11,22]. DMF yields varied with the particular metal catalyst and the reaction conditions but were typically less than about 50%.…”

“…In previous studies, we showed that the HDO reaction for HMF in several alcohol solvents is a series reaction, with products forming as shown in Scheme 1 [8,22]. The HMF (A)…”

“…The liquid-phase HDO of HMF was performed in a continuous flow reactor which has been described elsewhere [8,22]. The reactor was a stainless-steel tube, 20 cm long and with a 4.6-mm ID.…”