CHEMICAL ENGINEERING TRANSACTIONS VOL. 37, 2014 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Eliseo Ranzi, Katharina Kohse- Höinghaus Copyright © 2014, AIDIC Servizi S.r.l., I SBN 978-88-95608-28-0; I SSN 2283-9216 Supercritical Water Gasification of Glucose/Phenol Mixtures as Model Compounds for Ligno-Cellulosic Biomass Daniele Castello* a , Andrea Kruse b,c , Luca Fiori a a Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77 – 38123 Trento, Italy b Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz, 1 – 76344 Eggenstein-Leopoldshafen, Germany c Institute of Agricultural Engineering, Conversion Technology and Life Cycle Assessment of Renewable Resources, University of Hohenheim, Garbenstrasse 9 – 70599 Stuttgart, Germany daniele.castello@ing.unitn.it Supercritical water gasification (SCWG) of biomass is one of the most promising ways to convert wet biomass into a valuable gas mainly composed of methane and/or hydrogen, according to the selected experimental conditions. A wide range of biomass can be classified as ligno-cellulosic, meaning that its main components are represented by cellulose and lignin. Such two main constituents of biomass behave in a completely different manner. It is known that lignin is much more difficult to gasify than cellulose. However, the effect of such inhibition has never been studied in great detail. In this work, glucose and phenol are used as model compounds for cellulose and lignin, respectively. Four aqueous mixtures were prepared, with a fixed organics content of 5 wt %, the remaining part being constituted by water. The organics content was represented by glucose/phenol in different relative amounts, ranging from a phenol concentration of 0 wt % (glucose only) to 30 wt %. Such mixtures underwent SCWG in a continuous tubular reactor at 400°C and 25.0 MPa, with different residence times, ranging from 10 to 240 s. Results show that phenol gives a limited contribution to gas production. On the other hand, phenol does not seem to be an inert, since it reacts in the liquid phase to form other compounds, probably tar and/or solids. 1. Introduction In the field of renewable energy from biomass, supercritical water gasification (SCWG) has been proposed during the last few years as a valuable technology to efficiently convert biomass into energy (Matsumura et al., 2005). The reaction of biomass with water results in a fuel gas, which can be rich in methane and/or oxygen, according to the operating conditions (Castello and Fiori, 2011). SCWG benefits of the unique properties of water at supercritical state. Indeed, supercritical water (T > 374 °C and P > 22.1 MPa) exhibits a behaviour intermediate between a liquid and a gas. Like a liquid, it has still quite high density and good solvent power; at the same time, however, it has the diffusivity and the reactivity typical of a gas. Moreover, water at supercritical state shows a very peculiar behaviour as solvent. Indeed, at high temperature and pressure, the dielectric constant of water dramatically decreases. This means that water starts behaving like a non-polar solvent, with an increased ability to dissolve many organic compounds that would not be dissolved in normal conditions (Kruse, 2009). Dealing with gasification, this translates into a great advantage: optimal mixing allows reducing the occurrence of tar formation, which is one of the factors hampering the diffusion of traditional gasification technologies (Bridgwater, 2003). Furthermore, the great advantage of SCWG is its ability to deal with wet biomass, with moisture contents even higher than 80 wt %. The energy valorisation of such class of feedstock is not commonly achievable with traditional thermochemical technologies, for which dry biomass is mandatory. SCWG opens new perspectives for the treatment of residual biomass (Myréen et al., 2011) and also algae (Freitas and Guirardello, 2013), one of the most promising energy feedstock for the future. DOI: 10.3303/CET1437033 Please cite this article as: Castello D., Kruse A., Fiori L., 2014, Supercritical water gasification of glucose/phenol mixtures as model compounds for ligno-cellulosic biomass, Chemical Engineering Transactions, 37, 193-198 DOI: 10.3303/CET1437033 193