ntroduction Nowadays, a large range of acids are produced from biomass via either chemical or biochemical transformations. The production of levulinic acid from lignocellulosic derivatives under acidic conditions has been described since the early nineteen’s, but large scale applications were reported more recently involving continuous processing by the Biofine technology [1]. Besides, biosuccinic acid is now produced via an economically viable process from renewable sources by different companies [2, 3]. These acids are considered as platform molecules that can be further transformed into added value products. The hydrogenation of these acids leads to the formation of lactone, cyclic ether or diol and represents promising alternatives to current petrochemical productions [4, 5]. To avoid the use of undesirable stoechiometric hydride reductants, the catalytic hydrogenation of biobased carboxylic acids has received strong interest. The preparation of heterogeneous catalysts which are s table under the reaction conditions and selective to a specific product is essential to achieve a competitive route. In the present work, the reactivity of mono and bimetallic catalysts in the hydrogenation of levulinic acid (LEV) and succinic acid (SUC) is reported, paying special attention to the optimization of the selectivity into diols. The reactivity of both acids will be compared. Experimental Catalyst preparation Active carbon and titanium oxide were used as supports. The monometallic catalysts were synthesized by wet impregnation or cationic exchange method. The amount of precursor was adjusted in order to achieve ca 2-3% weight. Bimetallic xwt.%Me-ywt.%Re catalysts were prepared by impregnation of the monometallic catalysts with NH4ReO4 precursor salt. Finally, the bimetallic catalysts were reduced under hydrogen flow at 450°C for 3 h. The metallic phase was characterized by means of various physicochemical methods: ICP-OES (inductively coupled plasma optical emission spectrometry), H2 chemisorption, TEM (transmission electron microscopy), TPR (temperature programmed reduction) and XPS (X-ray photoelectron spectroscopy); as well as by the gas phase model reaction of cyclohexane dehydrogenation. Acid hydrogenation In a typical batch reaction, the reactor (Hastelloy) was loaded with an aqueous solution of the considered acid (SUC or LEV) and the catalyst. After purging with Ar, the reactor was heated to the desired temperature under H2 pressure. The samples taken from the reactor at regular intervals during reaction were analyzed using both GC and HPLC. The main reaction products consisted of lactones (GBL, GVL), cyclic ethers (THF, MeTHF) and diols (BDO, PDO) with some by-products (monoalcohols, mono acids) (Scheme 1). The mass balance was checked by measuring Total Organic Carbon (TOC) in the liquid phase. Scheme 1: Hydrogenation of succinic acid (SucA) and levulinic acid (LevA) to lactone, cyclic ether and diol. Results and discussion The distribution of the products was affected by the nature of the catalyst and the reaction conditions. When monometallic catalysts were used in the reaction, lactones were formed as the main product regardless the nature of the metal. In order to observe the formation of diols or cyclic ethers, bimetallic catalysts must be used. As an example, the catalytic performances of a Re-Ru/C catalyst for levulinic (LEV) and succinic (SUC) acid hydrogenation are reported in Fig. 1. Figure 1: Main products distribution during the hydrogenation of LEV and SUC (reaction conditions: [acid]0= 0.43 mol/l, 160°C, 150 bar, 4%Re-2%Ru/C) Since the hydrogenation of a ketone group is easier than the hydrogenation of a carboxylic group, LEV is much more easily converted to the lactone than SUC. As a consequence, a very high selectivity in GVL (90%) was achieved from LEV within less than 1 h, while SUC yielded ca. 40% GBL after 8 h. Subsequent hydrogenation of the lactones to the corresponding diols was then possible. However concomitant overhydrogenolysis occurred and almost 40% of mass balance were missing in the case of LEV. To overcome this drawback, the reaction has been carried out at lower temperature. As expected, the reaction rate decreased with the temperature but a significant positive effect on the selectivity to the diol was observed. In the presence of RuRe/C, GVL was completely hydrogenated after 22 h at 160°C (Fig. 1a), while 48 h and 72 h are necessary to achieve complete hydrogenation at 140°C and 120°C, respectively. However, the selectivity to PDO increased from 69% up to 80% while the temperature was lower (Fig. 2). Simultaneously, the selectivity to ether (MTHF) and monoalcohols (1-pentanol, 2-pentanol and 2-butanol) decreased and the mass balance was much better (from 60% at 160°C up to 90% at 120°C). This was mainly attributed to the lower formation of degradation products issued from cracking of the substrate or the intermediates. Figure 2: Influence of the temperature on the product distribution at 100% GVL conversion. Reaction conditions: [LEV]0 = 0.43 mol/l, 2.2%Ru-3.8%Re/C, molar ratio LEV/Ru = 2000, 150 bar. Alcohols = 1-PeOH + 2-PeOH + 2-BuOH. The different physicochemical techniques used to characterize PdRe catalysts evidenced interactions between both metallic species that could be responsible of the peculiar reactivity of these bimetallic catalysts. Conclusions The heterogeneous hydrogenation of biobased acids can be efficiently carried out in water in the presence of supported mono or bimetallic catalysts and leads to the formation of the lactone or the diol depending on the reaction conditions and the nature of the catalyst. Acknowledgements This work was supported by the French Agence Nationale de la Recherche within the Programme Chimie et Procédés pour le Développement Durable CP2D 2009 (HCHAIB) and IFPen. References [1] S.W. Fitzpatrick, US5608105 (1995). [2] J.B. McKinlay, C. Vieille, J.G. Zeikus, Appl. Microbiol. Biotechnol. 76 (2007) 727. [3] J.J. Beauprez, M. De Mey, W.K. Soetaert, Process Biochem. 45 (2010) 1103. [4]D.P. Minh, M. Besson, C. Pinel, P. Fuertes, C. Petitjean, Top Catal. 53 (2010) 1270. [5]B.K. Ly, D.P. Minh, C. Pinel, M. Besson, B. Tapin, F. Epron, C. Especel, Top Catal. 55 (2012) 466.