Catalytic gasification of glucose to H 2 in supercritical water Ning Ding a , Ramin Azargohar a , Ajay K. Dalai a, ⁎, Janusz A. Kozinski b a Department of Chemical and Biological Engineering, College of Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK S7N 5A9, Canada b Department of Science and Engineering, York University, 88 The Pond Rd, Toronto, ON M3J 1P3, Canada abstract article info Article history: Received 4 February 2013 Accepted 19 May 2014 Available online xxxx Keywords: Supercritical water Glucose Gasification Hydrogen Catalyst Gasification of glucose in supercritical water with and without catalysts (NaOH and Ni based) was investigated at 400 °C and 500 °C with a residence time of 30 min. The products from glucose gasification without catalyst con- sist of ~ 8–17 wt.% gas, 21–24 wt.% solid, 9–16 wt.% acetone phase and 8–10 wt.% water phase. As expected, all the gas product yields increased by an increase in process temperature and higher water to biomass ratio benefits the yields of gas phase and water phase. For the experimental runs with catalysts, NaOH had the best activity for im- proving H 2 formation, the H 2 yield increased by 135% with NaOH compared to that for run without catalyst at 500 °C with water to biomass ratio of 3. At the same operating conditions, the presence of Ni/activated carbon (AC) contributed to 81% increase in H 2 yield, followed by 62% with Ni/MgO, 60% with Ni/CeO 2 /Al 2 O 3 and 52% with Ni/Al 2 O 3 . The net effect of Ni was studied by using activated carbon and Ni/AC at 500 °C with water to bio- mass ratio of 7 for 30 min. The results showed that the hydrogen production was further increased by 6.9% with activated carbon and 36.9% with Ni/AC. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Energy shortage and environmental pollution are two main chal- lenges that require immediate attention. With the increasing consump- tion of fossil fuels, much research has been focused on renewable energies such as solar and biomass in the recent years [1]. Bio-energy (energy derived from biomass) is an immense source of renewable energy which will not run out [2]. As a renewable energy, biomass can reduce the reliance on fossil fuels. Cellulose, hemicelluloses, and lignin form the basic structure of the lignocelluloses, and are the building blocks of biomass. Real biomass typically consists of ~25 wt.% lignin and 75 wt.% carbohydrates (i.e. cellulose and hemicellulose). Meanwhile, bio- mass contains other substances, including minerals and organic mole- cules, such as tannins, terpenes, waxes, fatty acids and proteins [3]. Generally, the conventional gasification is carried out at 700–1000 °C, atmospheric pressures without catalyst and the gas product can be used in different methods depending on the composition [2]. The feedstock needs to be dry enough to ensure a high conversion efficiency in conven- tional gasification process which makes biomass not a suitable feedstock for conventional gasification technologies. However, for gasification of biomass in supercritical water (Tc N 374 °C, Pc N 22.1 MPa), there is no need to evaporate the water prior to the gasification process because water is used as a medium to provide the desired operating condition. Therefore, for wet biomass containing large amounts of water up to 90%, supercritical water gasification appears as a useful technology [4]. Supercritical water (SCW) has the unique characteristic of dissolving ma- terials which are not normally soluble in either liquid or vapor phase. The low dielectric constant of supercritical water makes it a good solvent for organic compounds. Also, SCW possesses low viscosity which provides a high diffusion coefficient and a better ability of mass transfer [1]. Com- pared with the conventional gasification methods, the supercritical water gasification (SCWG) process has high reaction efficiency and H 2 se- lectivity; the reactions proceed very rapidly and completely [5]. Another advantage of gasification in supercritical water is the high solid conver- sion, i.e. low amount of char and tar formations [3]. Therefore, SCWG is one of the efficient hydrogen production methods with great potential. The main reactions during the gasification of glucose in SCW are as follows [6]: Char gasification: C þ H 2 O↔CO þ H 2 ð1Þ C þ 1=2O↔CO ð2Þ C þ CO 2 ↔2CO ð3Þ Water–gas shift: CO þ H 2 O↔CO 2 þ H 2 ð4Þ Methanation: CO þ 3H 2 ↔CH 4 þ H 2 O ð5Þ Fuel Processing Technology 127 (2014) 33–40 ⁎ Corresponding author. Tel.: +1 306 9664760; fax: +1 306 9664777. E-mail address: ajay.dalai@usask.ca (A.K. Dalai). http://dx.doi.org/10.1016/j.fuproc.2014.05.014 0378-3820/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc