CHEMICAL ENGINEERING TRANSACTIONS VOL. 81, 2020 A publication of The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Petar S. Varbanov, Qiuwang Wang, Min Zeng, Panos Seferlis, Ting Ma, Jiří J. Klemeš Copyright © 2020, AIDIC Servizi S.r.l. ISBN 978-88-95608-79-2; ISSN 2283-9216 Surface Area of Oil Shale and its Solid Pyrolysis Products Depending on the Particle Size Heliis Pikkor, Birgit Maaten, Zachariah Steven Baird, Oliver Järvik, Alar Konist, Heidi Lees* Department of Energy Technology, Tallinn University of Technology, Ehitajate tee 5, Tallinn, 19086, Estonia heidi.lees@taltech.ee Oil shale is currently used for electricity and oil production. The production of the latter produces large quantities of residue, i.e. semi-coke, from which it could be possible to create valuable porous materials with high surface areas. These adsorbents could be used in a wide range of environmental and industrial applications. To produce adsorbents, it is first important to characterise the source material and to find out to what extent the surface area differs depending on the particle size. Considering the above, seventeen oil shale fractions, with particle sizes ranging from 36 μm to 8 mm, were characterised in terms of total organic carbon (TOC) content, specific surface area (SSA) and porosity. Special attention was paid to the analysis of SSA using Brunauer-Emmett-Teller (BET) theory. The SSA of the studied oil shale was found to vary from 4 to 13 m 2 /g depending on the particle size. The analyses performed supported the known trend that the finer fractions have slightly higher contents of organic matter (i.e. kerogen) as well as higher surface areas. In addition, preliminary pyrolysis tests with the oil shale fractions were also carried out to see the effect of thermal treatment on surface area. After treatment, BET surface areas were in the range of 19–38 m 2 /g. As the final goal is to obtain activated carbon with a large SSA, it is important to know if and how much the results are affected by the source material. The present study provides fundamental knowledge about the source material that will enable applied research in the future. 1. Introduction Oil shale is a sedimentary rock consisting of mineral and organic matter (i.e. kerogen) (Foltin et al., 2017). Kerogen can be converted into oil, gas and semi-coke by thermal degradation (Ma and Li, 2018). Shale oil is a liquid fuel produced from oil shale and obtained by thermal decomposition of the organic part of oil shale and condensation of oil vapours. In 2018, 16 M t of oil shale was mined in Estonia. Today, Estonia is one of the largest producers of shale oil in the world – 1.1 M t of shale oil was produced in 2018 (Maaten et al., 2020). It can be calculated that for producing one ton of shale oil, approximately four t of semi-coke waste is inevitably generated (Gusca et al., 2015). Currently, semi-coke is predominantly going to waste, namely deposited in landfills (Pihu et al., 2019). However, oil shale semi-cokes could be used after pre-treatment potentially as adsorbents, which could be applied in separation, purification, and recovery processes. Preparation of an adsorbent generally involves conversion of the organic material, which is achieved by thermal treatment. As mentioned above, thermal treatment (in particular pyrolysis) is already used for shale oil production (Neshumayev et al., 2019). This makes the idea of this study also very practical as the by-product semi-coke could be effectively used. For producing a porous adsorbent material, the specific surface area (SSA) and porosity of the product are two of the main parameters related to material adsorption efficiency. Generally, the higher the SSA and more evolved porosity, the better the adsorbent. In fact, the sorptive potential of oil shale semi-coke has been investigated before. In this regard, Külaots et al. (2010) analysed oil shale samples from Estonia, China and the United States. Authors pyrolysed samples at 500 and 1,000 °C and analysed the products for organic char content, surface area and porosity. Pyrolysis of the oil shales at 500 and 1,000 °C yielded semi-cokes with BET surface areas of 4.4–57 m 2 /g. Bai et al. (2012) studied experimentally the effects of pyrolysis temperature (350–450 °C) and heating rate (2.5 to 20 °C/min) on DOI: 10.3303/CET2081161 Paper Received: 28/04/2020; Revised: 28/05/2020; Accepted: 31/05/2020 Please cite this article as: Pikkor H., Maaten B., Baird Z.S., Järvik O., Konist A., Lees H., 2020, Surface Area of Oil Shale and its Solid Pyrolysis Products Depending on the Particle Size, Chemical Engineering Transactions, 81, 961-966 DOI:10.3303/CET2081161 961