Contents lists available at ScienceDirect Molecular Catalysis journal homepage: www.elsevier.com/locate/mcat Lewis acidity induced heteropoly tungustate catalysts for the synthesis of 5- ethoxymethyl furfural from fructose and 5-hydroxymethylfurfural P. Krishna Kumari, B. Srinivasa Rao, D. Padmakar, Nayeem Pasha, N. Lingaiah ⁎ Catalysis Laboratory, Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad, 500 007, Telangana, India ARTICLE INFO Keywords: 5-Hydroxymethylfurfural Fructose 5-Ethoxymethylfurfural Etherification Tungstophosphoric acid ABSTRACT Heteropoly tungstate with tantalum ions in its secondary structure were prepared and subsequently dispersed on tin oxide. The prepared materials physical and chemical properties were estimated by different spectroscopic methods Characterization results indicate that the stable Keggin ion of tantalum heteropoly tungstate was well preserved on support. New Lewis acidic sites were generated with the presence of Ta ions in heteropoly tung- state. These samples were tested for their catalytic performance towards conversion of fructose to 5-ethoxy methyl furfural (EMF) and selective etherification of 5-hydroxymethylfurfural (HMF) with ethanol. The catalyst with 30 wt% of active component on SnO 2 exhibited highest HMF etherification activity with 90% of 5-ethox- ymethylfurfural yield with in 45 min. The catalysts also able to converted fructose into EMF in one-pot with a yield of 68%. The etherification activity over these catalysts was studied under the influence of different reaction parameters such as reaction temperature, reaction time, catalyst weight and reactants mole ratio. 1. Introduction The world energy system is mostly dependent on the non renewable fossil fuel resources, particularly petroleum, coal and natural gas [1]. The gradual depletion of these energy sources, concerns regarding Green House Gases (GHG) emissions in the atmosphere and high de- mand for energy has become severe concern for researchers [2]. In order to overcome the problems of fossil fuels, researchers’ attention was focused on finding alternative sustainable and eco-friendly energy sources [3]. Among the renewable resources, biomass is the only sus- tainable source to produce fuels, chemicals and carbon-based materials [4]. Biomass is broadly available in nature and different primary compounds like carbohydrates can be derived [5]. Carbohydrates are desirable resources for manufacture of bio fuels and valuable chemicals. Different methodologies have been explored to process abundant and cheaper biomass to chemicals/fuels [6]. Production of different bulk chemicals is possible from biomass and among different chemicals 5-hydroxymethylfurfural (HMF) is con- sidered as potential substitute for petroleum derived building blocks [7]. It is considered as a useful platform molecule to produce fine chemicals and fuel/fuel additives. HMF can be transformed to fine chemicals by hydrogenation, oxidation, esterification and etherification [8–10]. Among the wide range of possibilities, HMF etherification to 5- ethoxymethylfurfural (EMF) is important approach to synthesis fuel additives. EMF has energy density as diesel, high cetane number and in certain cases it enhances the fuel properties [11,12]. In addition, EMF is able to convert to 5-ethoxymethylfurfuryl alcohol by hydrogenation. This hydrogenated product is more miscible with diesel and has ana- logous combustion properties as that of ethanol [13]. Therefore, EMF synthesis from renewable sources has gained considerable interest. EMF can be prepared using different substrates like 5-chlor- omethylfurfural by nucleophilic substitution with ethanol [14], direct etherification of carbohydrates like fructose into EMF with alcohol in one-pot reaction as shown in Scheme 1. The etherification and direct conversion of fructose to EMF are acid catalyzed reactions. Therefore it is reasonable to carry fructose dehydration to HMF and its etherifica- tion into EMF in one-pot reaction. Etherification of HMF to EMF reac- tion was conceded using acidic catalysts like ionic liquids, organic-in- organic hybrid catalyst [15], H 3 PW 12 O 40 [16] and AlCl 3 [17]. The solubility of these catalysts in reaction mixture and/or polar solvents becomes difficult to separate the product from catalyst. In this contest there is a need to develop heterogeneous catalyst for one-pot conver- sion of fructose to EMF. Recently few researchers has studied hetero- geneous catalysts such as MCM-41 supported HPW [18], silica coated magnetic Fe 3 O 4 nano particles supported tungstophosphoric acid cat- alysts for both HMF and fructose etherification [19]. Recently Xiao fang Liu et al. used sulphated porous coordinated polymer (MIL 101- SO 3 H) as a catalyst towards EMF synthesis from carbohydrates [20]. Lanza- fame and co-workers were used a mesoporous silica based catalysts for the translation of HMF to EMF [21]. Arenesulfonic acid-modified SBA- https://doi.org/10.1016/j.mcat.2018.01.034 Received 21 August 2017; Received in revised form 26 December 2017; Accepted 29 January 2018 ⁎ Corresponding author. E-mail address: nakkalingaiah@iict.res.in (N. Lingaiah). Molecular Catalysis 448 (2018) 108–115 2468-8231/ © 2018 Elsevier B.V. All rights reserved. T