Furfural production from xylose using sulfonic ion-exchange resins (Amberlyst) and simultaneous stripping with nitrogen I. Agirrezabal-Telleria ⇑ , A. Larreategui, J. Requies, M.B. Güemez, P.L. Arias Department of Chemical and Environmental Engineering, Engineering School of the University of the Basque Country, Alameda Urquijo s/n, Bilbao 48013, Spain article info Article history: Received 31 March 2011 Received in revised form 6 May 2011 Accepted 8 May 2011 Available online 14 May 2011 Keywords: Furfural Process optimization Xylose dehydration Amberlyst Stripping abstract The aim of this work deals with the development of new approaches to the production of furfural from xylose. It combines relatively cheap heterogeneous catalysts (Amberlyst 70) with simultaneous furfural stripping using nitrogen under semi-batch conditions. Nitrogen, compared to steam, does not dilute the vapor phase stream when condensed. This system allowed stripping 65% of the furfural converted from xylose and almost 100% of selectivity in the condensate. Moreover, high initial xylose loadings led to the formation of two water–furfural phases, which could reduce further purification costs. Constant liquid–vapor equilibrium along stripping could be maintained for different xylose loadings. The modeling of the experimental data was carried out in order to obtain a liquid–vapor mass-transfer coefficient. This value could be used for future studies under steady-state continuous conditions in similar reaction- systems. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Furfural (FUR) is a versatile key derivative produced from pentosan-rich biomass (Mamman et al., 2008; Mansilla et al., 1998). It is considered a selective solvent for organic compounds and serves as a building-block for its hydrogenation to furfuryl alcohol, for components of P-series fuels or liquid alkanes (Chheda et al., 2007; Weingarten et al., 2010). It is produced from the hemi- cellulosic fraction of the biomass. This fraction is produced through hydrolysis processes (Chareonlimkun et al., 2010; Matsumoto et al., 2011; Wang et al., 2011). During the initial stage of hemicellulose hydrolysis, the xylans generate pentose carbohydrates, which are further cyclodehydrated to furfural. Commercially, FUR is produced using sulfuric acid as homogeneous catalyst. Moreover, high steam to product ratio is used in order to strip the FUR and to avoid its further degradation (Mamman et al., 2008). However, these condi- tions show several drawbacks: high vapor product dilution leading to expensive purification stages, safety issues and environmental problems due to toxic waste effluents. For these reasons, the improvement of appropriate chemical technology remains of great interest for the growth of furan-based industry. Optimization studies of the current processes aim to reduce furfural degradation reactions operating at 230 °C (SUPRATHERM process), reducing yield–loss reactions (Zeitsch, 2000). In the SUPRAYIELD process, higher product purity is obtained using adia- batic flash distillation, leading to yields of up to 65% in the FUR vapor phase (Arnold and Buzzard, 2003). Nevertheless, 70% of the total industrial FUR production is still based on the fixed-bed reac- tor process using steam as stripping agent and reaching an overall yield of 50%. Recently, alternative liquid solvents instead of water have been researched, such as dimethylsulfoxide (Dias et al., 2005b), ionic- liquids (Lima et al., 2009; Zhao et al., 2007) or supercritical CO 2 (Kim and Lee, 2001). All of them have shown efficient solvent capacity using carbohydrates as model compounds. Biphasic sys- tems using water and butanol, methyl isobutyl ketone or toluene (Román-Leshkov et al., 2006; Zhang et al., in press) as phase mod- ifiers have been also applied to the dehydration of xylose (Dias et al., 2005a,b, 2006b; Lima et al., 2008; Moreau et al., 1998). Addi- tional solvents show high capacity as isolating ‘‘chambers’’, where secondary reactions are minimized and as a result selectivity to FUR is improved. However, they present significant drawbacks: high furfural–solvent separation costs and their use would require separate hydrolysis and dehydration steps (Mamman et al., 2008). Another important field of research deals with the development of novel catalysts. Recent studies report hydrothermally stable heterogeneous catalysts, with strong acid capacity and shape/ adsorption selectivity for the dehydration of xylose as model com- pound. Zeolitic structures range from ZSM-5 in its protonated form (O’Neill et al., 2009) or layered zeolites with high active site acces- sibility (Lima et al., 2008) to H-mordenite/faujasite-HY type arrangements (90% selectivity at 30% X X )(Moreau et al., 1998). Other studies achieved a maximum yield of 55% using crystalline 0960-8524/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2011.05.015 ⇑ Corresponding author. Tel.: +34 61 7912 295; fax: +34 94 6014 179. E-mail address: iker_agirrezabal@ehu.es (I. Agirrezabal-Telleria). Bioresource Technology 102 (2011) 7478–7485 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech