Catalysis Today 223 (2014) 97–107 Contents lists available at ScienceDirect Catalysis Today jou rn al hom epage: www.elsevier.com/locate/cattod Aqueous phase reforming of xylitol over Pt-Re bimetallic catalyst: Effect of the Re addition Alexey V. Kirilin a , Anton V. Tokarev a , Haresh Manyar b , Chris Hardacre b , Tapio Salmi a , J.-P. Mikkola a,c , Dmitry Yu. Murzin a,∗ a Laboratory of Industrial Chemistry and Reaction Engineering Process Chemistry Centre, Åbo Akademi University, FI-20500 Åbo-Turku, Finland b CenTACat School of Chemistry, Queen’s University of Belfast, UK c Department of Chemistry, Technical Chemistry, Chemical Biological Centre, Umeå University, SE-901 87 Umeå, Sweden a r t i c l e i n f o Article history: Received 4 February 2013 Received in revised form 20 August 2013 Accepted 5 September 2013 Available online 17 October 2013 Keywords: Biomass conversion Aqueous phase reforming of xylitol Pt-Re/TiO2 Hydrogen formation Bimetallic catalyst a b s t r a c t The aqueous phase reforming (APR) of xylitol was studied in a continuous fixed bed reactor over three catalysts: Pt/Al 2 O 3 , Pt/TiO 2 and Pt-Re/TiO 2 . The data obtained in the case of the monometallic Pt catalysts was compared to the bimetallic Pt-Re sample. The effect of Re addition on the catalyst stability, activ- ity, product formation and selectivity toward hydrogen and alkanes was studied. The bimetallic catalyst demonstrated a higher selectivity to alkanes compared to the monometallic samples. The monometal- lic catalyst was more selective toward hydrogen formation. A plausible reaction scheme explaining differences in selectivity toward hydrogen and alkanes was proposed and discussed. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The constant increase in the consumption of fossil fuels such as oil, natural gas and coal, within last decades required new alternative sources of energy, energy-rich materials and chemi- cals. Biomass can be regarded as a renewable source of platform chemicals, biofuels, energy-rich materials such as hydrogen [1–3]. Aqueous phase reforming (APR) firstly introduced in 2002 [4] has attracted a lot of attention all over the world, since this process is efficient in terms of hydrogen and light hydrocarbons produc- tion from biomass-derived sugars and sugar alcohols. The process is typically carried out at 210–250 ◦ C at elevated pressures (≥30 bar) utilizing water solutions of polyols containing from 1 to 10 wt.% of reactants. Numerous publications on APR of ethylene glycol (EG) [5], glycerol [6], sorbitol [1,7,8] in the presence of either monometallic or bimetallic catalysts [9] can be found in the lit- erature. In fact, Pt supported catalysts have been shown to be the most effective among monometallic catalysts for aqueous phase reform- ing of polyols in terms of activity, stability and selectivity toward desired products (either hydrogen or hydrocarbon mixture) [9]. Addition of Re to Pt/C has been studied to improve the reforming of ∗ Corresponding author. Tel.: +358 22154985. E-mail address: dmurzin@abo.fi (D.Yu. Murzin). glycerol [10–15] and other polyols [15] and led to improved glycerol conversion. Usually Pt-Re catalysts supported on different carbon materials with a metal ratio of 1:1 (wt.%/wt.%) have been applied containing 3 wt.% of Pt and 3 wt.% of Re. All studies have shown that Pt-Re/C catalysts are very stable with time-on-stream and much more active compared to monometallic catalysts. Likewise, it has been demonstrated that introduction of Re facilitates cleavage of C C bonds in the substrate [11] and leads to elevated rates of water gas shift and alkane formation reactions [12]. Rhenium oxide species (ReO x ) have been proposed to impose additional acidity to the catalyst surface, thus facilitating dehydration processes which result in hydrocarbons formation [14]. Kim et al. studied aqueous- phase reforming of EG, propyleneglycol, glycerol and sorbitol in the presence of Pt-Re catalysts supported on mesoporous carbon and compared to other supports, such as SiO 2 , Al 2 O 3 and activated car- bon (AC) [15]. The activity of supported Pt-Re catalysts decreased in the following order: mesoporous carbons > AC > SiO 2 > Al 2 O 3 . It is worth mentioning that monometallic Re catalysts themselves showed no or just an insignificant activity in the aqueous reform- ing of polyols. Recently King and co-workers studied a correlation between properties of Pt-Re supported on carbon and their cat- alytic performance in APR of glycerol [16]. It was revealed that addition of Re to Pt increases surface acidity of the material and thereby leads to more prominent contribution of dehydration reac- tions (C O cleavage) compared to decarbonylation reaction (C C cleavage). However, all the studies reported in the literature on the 0920-5861/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cattod.2013.09.020