Please cite this article in press as: N. Alonso-Fagúndez, et al., Poly-(styrene sulphonic acid): An acid catalyst from polystyrene waste for reactions of interest in biomass valorization, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.01.041 ARTICLE IN PRESS G Model CATTOD-8889; No. of Pages 10 Catalysis Today xxx (2014) xxx–xxx Contents lists available at ScienceDirect Catalysis Today j our na l ho me page: www.elsevier.com/locate/cattod Poly-(styrene sulphonic acid): An acid catalyst from polystyrene waste for reactions of interest in biomass valorization N. Alonso-Fagúndez a , V. Laserna a , A.C. Alba-Rubio a,1 , M. Mengibar b , A. Heras b , R. Mariscal a , M. López Granados a,∗ a Institute of Catalysis and Petrochemistry (CSIC), C/Marie Curie, 2, Campus de Cantoblanco, 28049 Madrid, Spain b Department of Physical Chemistry II, Faculty of Pharmacy, Institute of Biofunctional Studies, Complutense University, Po Juan XXIII no. 1, 28040 Madrid, Spain a r t i c l e i n f o Article history: Received 15 November 2013 Received in revised form 14 December 2013 Accepted 26 January 2014 Available online xxx Keywords: Biodiesel Xylose Furfural Maleic acid Succinic acid a b s t r a c t This article reports on the use of poly-(styrene sulphonic acid) (PSSA) prepared by sulphonation of polystryrene waste as catalyst in reactions demanding acid sites. Two different waste derived catalysts (waste to catalyst, WTC) were studied: soluble PSSA (WTC-PSSA) and solid SiO 2 -PSSA nanocomposite (WTC-SiO 2 -PSSA). The catalytic properties of these waste derived acid catalysts have been explored in three different reactions of interest in biomass valorization: biodiesel synthesis, xylose dehydration to furfural and furfural oxidation to maleic and succinic acids. The results show that both soluble and nanocomposite WTC catalysts present promising catalytic properties. The WTC-PSSA requires ultrafiltra- tion for reutilization whereas the WTC-SiO 2 -PSSA can be separated from the reaction mixtures by more usual techniques (centrifugation or conventional filtration). Further research is required for improving the hydrothermal stability of WTC-SiO 2 -PSSA in order to substantially reduce the leaching of polymer that takes place during the catalytic runs. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Important achievements have been already accomplished in the catalytic processing of biomass to biofuels and biobased products. Many breakthroughs are still to come but there is a consensus that many of the processes are being or will be conducted in liq- uid phase at relatively high reaction temperature and by utilizing polar solvents (like water and/or oxygenated organic solvents). This implies that the catalysts must withstand phenomena like leaching of active species, thermal and chemical deterioration and fouling by deposition of heavy products. Another relevant property of the catalyst must be its low price. We have demonstrated that commercial poly-(styrene sul- phonic acid) (PSSA) can be used as an effective catalyst for biodiesel synthesis and xylose to furfural dehydration [1]. PSSA is essentially not crosslinked (it is a linear macromolecule) and it is soluble in water and in other polar organic solvents. Therefore the transport ∗ Corresponding author at: Institute of Catalysis and Petrochemsitry (CSIC), Marie Curie, 2, Campus de Cantoblanco, 28049 Madrid, Spain. Tel.: +34 91 585 4937; fax: +34 91 585 47 60. E-mail address: mlgranados@icp.csic.es (M.L. Granados). 1 Current address: Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA. restrictions of the reactants to (or products from) all the active sites are diminished with respect to other solid porous catalysts. Leaching, thermal degradation and fouling phenomena were not detected during utilization in the reaction mixture and PSSA could be reused for a number of runs in both reactions. However reutilization of PSSA requires the separation from the reaction medium by ultrafiltration which is not a conventional pro- cedure [1]. To circumvent the ultrafiltration, we have proposed to retain the PSSA polymer by anchoring it on an inorganic solid: SiO 2 . Thus the so formed solid organic–inorganic nanocomposite can be separated from the reaction medium by more conventional pro- cedures like filtration or centrifugation. Part of the PSSA polymer chains are still exposed to the liquid phase, solvated by the sol- vent molecules and in good contact with reactants and products. A sol–gel methodology to hydrolyse and condensate SiO 2 organosi- lane precursors (TEOS) was used. Organosilane with aminopropyl functionalities (APTES) is also involved (see Scheme 1). Acid PSSA itself catalyzes the hydrolysis and condensation reactions impli- cated in the sol–gel process. Electrostatic interactions between the amine groups and part of the sulphonic functionalities are respon- sible of retaining the polymer molecules on SiO 2 . The solid catalyst displayed satisfactory hydrothermal stability and could be reuti- lized in the xylose to furfural reaction [2]. The objective of this article is to explore if PS waste can be effectively sulphonated to form PSSA catalysts and therefore be 0920-5861/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cattod.2014.01.041