Brief Communication Second generation biofuels: Thermochemistry of glucose and fructose A. Osmont a , L. Catoire b,c, * , P. Escot Bocanegra c , I. Gökalp c , B. Thollas d , J.A. Kozinski e a DGA/Centre d’Etudes de Gramat (CEG), 46500 Gramat, France b Department of Chemistry, Faculty of Sciences, University of Orléans, 1, Rue de Chartres, B.P. 6759, 45067 Orléans Cedex 2, France c C.N.R.S.—I.N.S.I.S., I.C.A.R.E., 1C, Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France d Polymaris Biotechnology, CCI de Morlaix, Aéroport, 29600 Morlaix, France e College of Engineering, University of Saskatchewan, 3B48 Engineering Building, 57 Campus Drive, Saskatoon, SK, Canada S7N 5A9 article info Article history: Received 27 July 2009 Received in revised form 20 October 2009 Accepted 2 December 2009 Available online 25 February 2010 abstract The energetic conversion of biomass into syngas or biogas is a more and more important topic. In the framework of these studies, improved understanding of glucose and fructose thermal decomposition and oxidation appears crucial. For this task, thermodynamic data are needed to make possible, for instance, the building of a detailed chemical kinetic model of glucose and fructose reactivity at high tem- perature. A semitheoretical protocol, presented elsewhere, is used for the estimation of the thermody- namic data of glucose and fructose in the gas phase. Five isomers of glucose and five isomers of fructose are considered and the lowest-energy conformers are found to be b-D-glucopyranose for glucose and b- D-fructopyranose for fructose. The data for all 10 isomers are provided in the CHEMKIN-NASA format. Ó 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1. Introduction First generation biofuels are bioethanol and biodiesel. They may not be totally ‘‘green,” but they address some of the drawbacks of current fossil fuels and their production is rapidly increasing. We have published studies dealing with the thermochemistry of bio- diesel components, obtained from vegetable oils [1–3]. However, it is highly probable that first generation biofuels are not able to replace fossil fuels entirely. Furthermore, their production is expected to cause damage to the environment such as deforesta- tion and intensive use of pesticides and is therefore questionable. Consequently, other fuel resources are needed. Second generation biofuels are obtained from biomass other than sugary or oleagi- nous plants, i.e., from plants that are not cultivated (wood), from agricultural residues (sugar cane and sugar beet residues, for in- stance), or from nonalimentary crops. Major constituents are cellu- lose, hemicellulose, and lignin; their amounts depend on the type of biomass. Biomass can be converted to syngas or biogas using various thermal processes. One of them is supercritical water gas- ification (SCWG) [4]. The chemistry of biomass in supercritical water might be complex and numerous molecules might form [4–6]. This is strongly dependent on the feedstock [7]. It is known that cellulose is converted into glucose and therefore the conver- sion of glucose to syngas has been studied thoroughly. Chemical processes in supercritical water are often interpreted in terms of detailed chemical kinetic models as encountered in the high-tem- perature chemistry field (combustion, chemical vapor deposition, waste incineration, etc.), i.e., gas-phase chemistry [8]. The creation of these models requires knowledge of the thermochemistry of reactants, intermediates (radicals and molecules), and products [9,10]. For glucose conversion in supercritical water, products are numerous. CO 2 , CO, CH 4 , and H 2 are identified in the gas phase and 23 compounds (acetic acid, propanoic acid, etc.) are identified in the liquid phase [6]. Some reaction pathways have been pro- posed to explain the conversion of glucose. Most of these reactions are global ones, whereas elementary reactions are required to ex- plain fundamentally the course of the conversion of glucose. It is, however, premature to propose a detailed chemical kinetic model constituted of elementary reactions, and the proposal of global reactions is therefore highly justified. The first step in the proposal of a detailed chemical kinetic mod- el of the conversion of glucose or fructose in a thermal process, whatever it is, is the establishment of the thermochemistries of glucose and fructose in the gas phase. The existence of glucose in the gas phase has not been assessed. The same holds for fructose. There is a vapor pressure above solid glucose, but the chemical nat- ure of this vapor has not been reported [11]. For modeling pur- poses the following sequence can be assumed: liquid glucose ! gaseous glucose ! intermediates ! products: Once the thermochemistries of glucose and fructose in the gas phase are known, it is then possible to discuss bond breaking in the molecules and propose elementary reactions able to explain the formation of products. 0010-2180/$ - see front matter Ó 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.combustflame.2009.12.002 * Corresponding author. Address: Department of Chemistry, Faculty of Sciences, University of Orléans, 1, Rue de Chartres, B.P. 6759, 45067 Orléans Cedex 2, France. Fax: +33 238696004. E-mail address: catoire@cnrs-orleans.fr (L. Catoire). Combustion and Flame 157 (2010) 1230–1234 Contents lists available at ScienceDirect Combustion and Flame journal homepage: www.elsevier.com/locate/combustflame