321 ISSN 0965-5441, Petroleum Chemistry, 2020, Vol. 60, No. 3, pp. 321–328. © Pleiades Publishing, Ltd., 2020. Published in Russian in Neftekhimiya, 2020, Vol. 60, No. 3, pp. 353–361. Kinetic-Based Models for Alumina and Titania Claus Catalysts Based on Experimental Data Sepehr Sadighi a, b, *, Seyed Reza Seif Mohaddecy a, b , Mehdi Rashidzadeh a, b , and Parisa Nouriasl c a Catalysis Development Technologies Division, Research Institute of Petroleum Industry (RIPI), West Side of Azadi Complex, Tehran, P.O. Box 1485733111 Iran b Gas Processing Institute (GPI), Research Institute of Petroleum Industry (RIPI), West Side of Azadi Complex, Tehran, P.O. Box 1485733111 Iran c Research and Technology Development Department, National Iranian Gas Company (NIGC), Tehran, P.O. Box 1416613631 Iran *e-mail: sadighis@ripi.ir Received February 13, 2019; revised August 19, 2019; accepted November 18, 2019 Abstract—Catalytic section of Claus process is significant for increasing the efficiency of sulfur recovery, and decreasing the amount of H 2 S emission to the environment. In this research, experiments at different gas hourly space velocities (GHSVs) and temperatures were carried out in a bench scale plant in the presence of both alumina (Al 2 O 3 ) and titania (TiO 2 ) commercial Claus catalysts. The feed composition and operating conditions were selected within the range of a target industrial scale plant. Thereafter, an isotherm model was constructed for the bench scale reactor, and its kinetic parameters were estimated using the obtained data. Results showed that H 2 S and CS 2 conversions over Al 2 O 3 and TiO 2 Claus catalysts could be predicted with the average absolute deviation (AAD) of 9.86 and 30.03%, and 15.31 and 4.22%, respectively. Keywords: sulfur recovery unit, Claus reactor, catalytic beds, kinetic modeling DOI: 10.1134/S0965544120030196 INTRODUCTION Due to the tough environmental regulations, the emission of toxic compounds such as H 2 S, SO 2 , and CS 2 to the atmosphere should be strictly controlled. In industrial facilities, these rules are tremendously strict for H 2 S which is highly toxic and corrosive gas, and upon reception, it can deteriorate the central nervous system at low dose of exposure in living souls [1, 2]. The modified sulfur recovery unit (SRU) has been extensively used to convert H 2 S to elemental sulfur exist in exhaust gases coming from natural gas plants, oil refineries, petrochemical units and coal gasifica- tion industries [3, 4]. This process consists of thermal and catalytic sections to promote desired reactions. For the catalytic bed of SRU, commercially catalysts such as activated alumina (for example CR3S of Axens and S-2001 of UOP) and TiO 2 (for example CRS31 of Axens and S-7001 of UOP) are used which may be uti- lized in a single layer or combined bed depending on the required performance [5]. In these reactors, H 2 S and CS 2 are converted to sulfur or other compounds through the following reactions [6]: (1) (2) (3) Respect to the mentioned perspectives, there is the necessity to develop a reliable and robust model to adequately infer the missing data from SRU [7]. Moreover, these models are beneficial for simulating Claus process and enhancing its performance [8]. There are many works that developed a kinetic model for the thermal-stage (reaction furnace) of the Claus process [9–14]. However, kinetic modeling of cata- lytic section of Claus process (convertors) based on laboratory or bench scale experiments was scarcely reported in the literature, and few studies only aimed the kinetic of the Al 2 O 3 catalyst. In this respect, Kerr et al. [15–17] developed a kinetic model for evaluating and studying the deactivation of alumina and bauxite catalysts. In this model, a power law equation was con- sidered for the reaction between H 2 S and SO 2 (i.e. main Claus reaction), and also hydrolysis of COS and CS 2 with water. The experiments were carried out in a laboratory scale isotherm reactor, and the model could adequately describe the behavior of catalysts in different reaction temperatures (230 to 300°C). Besher [18] studied the kinetic of Claus reaction on the Al 2 O 3 catalyst, and he concluded that thermodynamic equi- librium was not achievable in Claus reactors. Gem- + ↔ + 2 2 2 3 2H S SO 2H O S, n n + → + 2 2 2 2 CS 2H O 2H S CO , + → + 2 2 2 3 CS SO CO S. n n