A Kinetic Approach to the Temperature-Programmed Pyrolysis of Turkish Oil Shales in a Fixed Bed Reactor: Determination of Kinetic Parameters for n-Paraffins and 1-Olefins Evolution Levent Ballice* and Mithat Yu ¨ ksel University of Ege, Faculty of Engineering, Department of Chemical Engineering, 35100 Bornova, Izmir, Turkey Received March 30, 2001. Revised Manuscript Received July 14, 2001 The thermal degradation of both Go ¨ynu ¨ k oil shales (GOS) and Beypazari oil shales (BOS) has been investigated under nonisothermal conditions. The recovery of organic carbon as 1-olefins and n-paraffins was determined by temperature-programmed pyrolysis of oil shales. A fixed bed reactor under argon flow was used to pyrolyze small samples of oil shales. A special gas-phase sampling technique was used to determine the composition of products eluted from the reactor as a function of temperature and time. Hydrocarbon evolution data have been analyzed by Coats- Redfern and Chen-Nuttall combinations. It must be emphasized that the evaluation of temper- ature-programmed pyrolysis data by combined use of Coats-Redfern and Chen-Nuttall methods provide satisfactory mathematical approaches to obtain kinetic parameters for 1-olefins and n-paraffins formation from thermal degradation of Turkish oil shales. Using this method, it is possible to identify every stage of pyrolysis and derive values for kinetic parameters. Introduction The most important reaction in oil shale processing is that leading to shale oil. It is possible to develop global rate constants for this reaction that predict the timing of oil generation. These rate constants can help deter- mine processing times and consequently, reactor vol- ume, since reactor volume depends on throughput times the processing time. Rate constants can be also devel- oped for secondary reactions that affect both oil quality and quantity. The kinetics of decomposition of oil shales have been studied by many investigators, and various suggestions for the decomposition mechanisms have been re- ported. 1,2 Although some attempts have been made to understand the complex nature of decomposition of oil shale, involving numerous organic compounds, some authors have found it sufficient to consider a global first- order kinetic expression to represent the overall decom- position rate of oil shale. 1-4 Overall kinetics can be easily obtained by measuring the change in weight of a sample with time based on isothermal or nonisothermal thermogravimetric data. 1,2,5 The processing of oil shale involves numerous chemi- cal reactions and in addition to desired products, the chemical reactions also generate byproducts that can lead to environmentally undesirable emission. An un- derstanding of all these chemical reactions and their rates can help design processes that minimize the total processing cost, including the cost associated with meeting environmental regulations. 6 In this work, a kinetic study on the thermal decom- position of Go ¨ynu ¨ k oil shale (GOS) and Beypazari oil shale (BOS) is presented. The thermal degradation of the oil shales is investigated under nonisothermal conditions. An innovative approach to the data obtained by temperature-programmed pyrolysis of GOS and BOS 7,8 led us to determine the energies of activation for linear 1-olefins and n-paraffins formation. In the present study, the contribution of the activation energies of linear 1-olefins and n-paraffins formation to the apparent activation energy of overall degradation was determined. Theory Pyrolytic Decomposition of Kerogen and Hy- drocarbon Generation. Thermal breakdown of kero- gen in oil shale embodies three broad classes of reaction. These are decarboxylation reactions (involving princi- pally the decomposition of -COOH groups), major breakdown of kerogen to form oil and gas, with hydro- carbons as the main products and carbonization of the aromatic char. 9 Previous investigations have led to the * Corresponding author. E-mail: ballice@eng.ege.edu.tr. (1) Scala, D.; Kopsch, H.; Sokic, M.; Neumann, H. J.; Jovanovic, J. A. Fuel 1987, 66, 1185. (2) Scala, D.; Kopsch, H.; Sokic, M.; Neumann, H. J.; Jovanovic, J. A. Fuel 1990, 69, 490. (3) Yang, H. S.; Sohn, H. Y. Fuel 1985, 64, 1511. (4) Braun, R. L.; Burnham, A. K.; Reynolds, J. G.; Clarkson, J. E. Energy Fuels 1991, 5, 192. (5) Ballice, L.; Yu ¨ ksel, M.; Sag ˇ lam, M.; Schulz, H.; Hanog ˇ lu, C. Fuel 1995, 74, 1618. (6) Burnham, A. K. NATO ASI-Akcay-Tu ¨ rkiye, 1993, UCRL-JC- 114129, preprint. (7) Ballice, L.; Yu ¨ ksel, M.; Sag ˇlam, M.; Schulz, H. Fuel 1996, 75, 453. (8) Ballice, L.; Yu ¨ ksel, M.; Sag ˇlam, M.; Schulz, H. Fuel 1997, 76, 375. 96 Energy & Fuels 2002, 16, 96-101 10.1021/ef010077o CCC: $22.00 © 2002 American Chemical Society Published on Web 01/16/2002