ARTICLE IN PRESS JID: JTICE [m5G;December 9, 2017;23:25] Journal of the Taiwan Institute of Chemical Engineers 000 (2017) 1–9 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Hydrogen production from olive-pomace by catalytic hydrothermal gasification Murat Sert ∗ , Dilek Selvi Gökkaya, Nihal Cengiz, Levent Ballice, Mithat Yüksel, Mehmet Sa ˘ glam Department of Chemical Engineering, Ege University, 35100 Bornova, Izmir, Turkey a r t i c l e i n f o Article history: Received 29 August 2017 Revised 16 November 2017 Accepted 19 November 2017 Available online xxx Keywords: Biomass Olive pomace Hydrothermal gasification Hydrogen a b s t r a c t Hydrogen as a clean energy source has great potential to reducing the dependence on fossil fuels and en- vironmental pollution. For this reason, the production of hydrogen from renewable source will decrease this dependence and pollution. In this study, production of hydrogen from olive pomace was investigated. The experiments were performed at batch autoclave between 300 °C and 600 °C temperatures and a pres- sure of 200 atm–425 atm range. In addition to these parameters, the effect of catalyst (Trona, K 2 CO 3 and KOH) was also investigated. H 2 , CO 2 , CH 4 , CO and small amount of C 2 –C 4 hydrocarbons were identified in gaseous products. H 2 formation increased with increasing temperature and decreased with pressure increase. Hydrogen formation has the highest value as 16.80 mol/kg biomass at 600 °C in the presence of KOH catalyst. Besides the effect of KOH, the presence of K 2 CO 3 and Trona catalysts also increased the formation of hydrogen. The pressure affected the gasification yield and hydrogen composition in gaseous product. © 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Today, world energy demand is supplied by fossil fuels and al- most all motor vehicles are powered by gasoline, diesel and natu- ral gas [1]. Due to environmental concerns, especially greenhouse gases, economical reasons and also depletion of the fossil fuels or non-renewable energy resources, researches have focused on pro- duction of valuable chemicals and energy from clean and renew- able sources like biomass [2]. So, replacing the intermediates or the products derived from petroleum with renewable sources is in- dispensable. The most promising alternative for valuable chemicals and for oil today is biomass. As an inexhaustible energy resource, biomass is abundant and can be grown almost each part of the world. The most important feature of biomass is to be converted to valuable chemicals such as hydrogen, methane, carbon dioxide and energy. The most outstanding title alternative to petroleum de- rived products is hydrogen which is clean energy source. For more than three decades, hydrogen energy is one of the most researched topics [3–6]. It can be used for transportation as well as power sta- tions [7]. Hydrogen is mainly produced by thermochemical meth- ods; such as steam reforming from fossil fuels due to economic reasons when compared to biomass energy [4,8,9]. But this way of ∗ Corresponding author. E-mail address: murat.sert@ege.edu.tr (M. Sert). hydrogen production give rise to increase in carbon dioxide emis- sion in the atmosphere. In contrast to conventional methods like pyrolysis, reforming or thermal gasification, hydrogen production from biomass by sub or supercritical water is one of the remark- able research fields. Especially, high water content biomass can be converted to combustible gases like hydrogen, methane or carbon monoxide by supercritical water gasification (SCWG) without dry- ing procedure. Conversely, water as a reaction medium, behaves as reactant during SCWG process [5,10,11]. The main purpose of SCWG which is accepted as environmental friendly process is to obtain hydrogen from wet biomass at lower temperatures when compared to classical gasification techniques. Supercritical water has unique characteristics and ability to suppress char formation during the decomposition of organic compounds. At temperatures of near-critical and supercritical point (347.8 °C and 22.1 MPa), wa- ter dissociated to form both the H 3 O + and the OH − ions. Because of acidic and alkaline character of supercritical water, it behaves as a catalytic precursor for acidic or basic reactions [10,12]. The olive oil industry is mainly located in Mediterranean coun- tries such as Spain, Turkey, Italy or Tunisia. The olive oil extraction produces large amount of waste which pollutes soil and water. So, olive mill wastes represent an important environmental problem in Mediterranean areas where they are generated in huge quanti- ties in short periods of time. Turkey is one of the Mediterranean countries and produces approximately 700 kt of olive and 120 kt of olive pomace in a year [13,14]. Olive pomace has high phenol https://doi.org/10.1016/j.jtice.2017.11.026 1876-1070/© 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Please cite this article as: M. Sert et al., Hydrogen production from olive-pomace by catalytic hydrothermal gasification, Journal of the Taiwan Institute of Chemical Engineers (2017), https://doi.org/10.1016/j.jtice.2017.11.026