Green Chemistry PAPER Cite this: Green Chem., 2014, 16, 708 Received 5th June 2013, Accepted 6th January 2014 DOI: 10.1039/c3gc41071d www.rsc.org/greenchem Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts† Jechan Lee, Yong Tae Kim and George W. Huber* The reaction rate on a per site basis for aqueous-phase hydrogenation (APH) of propanal, xylose, and fur- fural was measured over various alumina-supported bimetallic catalysts (Pd–Ni, Pd–Co, Pd–Fe, Ru–Ni, Ru–Co, Ru–Fe, Pt–Ni, Pt–Co, and Pt–Fe) using a high-throughput reactor (HTR). The results in this paper demonstrate that the activity of bimetallic catalysts for hydrogenation of a carbonyl group can be 110 times higher than monometallic catalysts. The addition of Fe to a Pd catalyst increased the activity for hydrogenation of propanal, xylose, and furfural. The Pd 1 Fe 3 catalyst had the highest reaction rate for APH of propanal among all catalyststested in the HTR. The addition of Fe to the Pd catalyst increased the reac- tion rate for xylose hydrogenation bya factor of 51, compared to the monometallic Pd catalyst. However, no bimetallic catalyst tested in this study was more active than the monometallic Ru catalyst for hydro- genation of xylose. The Pd 1 Fe 3 catalyst had the highest reaction rate for APH of furfural, which was 9 times higher than the rate of the Pd catalyst. The Pd 1 Fe 3 /Zr–P, a bimetallic bifunctional catalyst, was 14 times more active on a per site basis than a Pd/Zr–P catalyst for aqueous-phase hydrodeoxygenation (HDO) of sorbitol in a continuous flow reactor. The addition of Fe to the Pd catalyst increased the rate of C–C cleavage reactions and promoted the conversion of sorbitan and isosorbide in HDO of sorbitol. Pd 1 Fe 3 /Zr–P also had a higher yield of gasoline-range products than the Pd/Zr–P catalyst. 1. Introduction Aqueous-phase hydrogenation (APH) reactions, a critical fundamental reaction of aqueous-phase processing (APP), are used in a variety of processes for the conversion of biomass into fuels and chemicals. 1–7 APH involves the hydrogenation of a range of functionalities including aldehydes, ketones, furans, carbohydrates, and alkenes. 8–10 Bimetallic catalysts often have a higher activity than either of their parent metals. 11 For example, Co and Ni promoted Pt catalysts exhibited a higher activity for the hydrogenation of CvO bonds than the corresponding monometallic cata- lysts. 12,13 A bimetallic Ni–Pd catalyst was more active than RANEY® Ni for the hydrogenation of HMF and furfural. 14 The addition of Ni, Co, and Fe to a Pt catalyst increased the activity for aqueous-phase reforming (APR) of ethylene glycol up to 3 times. 15 It was proposed that this increase in catalytic activity was because the Ni, Co, and Fe decrease the adsorption energy of carbon monoxide (CO) and H on the Pt metal surface. 16–19 Bimetallic catalysts have also been shown to have a higher activity for electrocatalytic reactions. 20–24 For example, Pt–Ru bimetallic catalyst was more active than monometallic Pt cata- lyst for electrocatalytic oxidation of glycerol. 24 Bimetallic catalysts can also modify the reaction selecti- vity. 11 For instance, Pd–Cu and Ni–Fe bimetallic catalysts had a higher selectivity toward hydrogenation products but lower selectivity toward decarbonylation products for furfural conver- sion than the pure monometallic Pd and Ni catalysts. 25,26 Pt–Ni and Pt–Co bimetallic catalysts showed a higher selecti- vity toward deoxygenation products than monometallic Pt cata- lyst for hydrodeoxygenation (HDO) of meta-cresol. 27 The addition of Sn to Ni catalysts can increase the hydrogen selecti- vity from 47% to 93% for APR of ethylene glycol. 28 In spite of the clear advantages of bimetallic catalysts, they have not been widely used for biomass conversion reactions. More infor- mation about the use of bimetallic catalysts for fundamental reactions like APH reactions of model biomass compounds is needed to properly design bimetallic catalytic processes for realistic biomass conversion processes. High-throughput techniques have been developed that make possible the rapid screening of large numbers of cata- lytic materials. 10,15,29–33 We have previously used a high- † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c3gc41071d Department of Chemical and Biological Engineering, University of Wisconsin- Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA. E-mail: huber@engr.wisc.edu 708 | Green Chem. , 2014, 16, 708–718 This journal is © The Royal Society of Chemistry 2014 Published on 07 January 2014. Downloaded by University of Science and Technology of China on 22/04/2014 02:24:18. View Article Online View Journal | View Issue