Chinese Journal of Chemical Engineering, Vol.28, No.3, 793-807, 2020
Numerical investigation of complex chemistry performing in Pt-catalyzed oxidative dehydrogenation of ethane fixed-bed reactors
Ethylene is one of the most important basic chemicals in the modern chemical industry. Thermal or catalytic cracking of hydrocarbons is the main industrial technologies nowadays, which suffer from equilibrium-limitation and rapid coke formation. The oxidative dehydrogenation of ethane (ODHE) is considered to be a promising alternative process since it overcomes equilibrium-limitations, avoids catalyst deactivation by coke formation, and decreases the number of side reactions. In this study, particle-resolved 2D CFD simulations of fixed-beds filled with eggshell catalysts coupled with micro-kinetics of Pt-catalyzed ODHE were performed to understand the effect of operation conditions and catalyst properties on ethylene selectivity. The catalyst bed was created by discrete element method (DEM) and the central longitudinal section of the reactor tube was defined as the 2D simulation region. Both of the homogeneous and catalytic heterogeneous chemical reactions were described by detailed micro-kinetics within the particle-resolved CFD simulation. At first, the established model of monolith reactors was verified by comparing the simulated results with experimental results reported in literature. Then, the effects of operation conditions and catalyst concentration on the ethylene selectivity in randomly packed beds were explored. The specific variation of certain operation conditions including inlet flow rate, inlet temperature, pressure, inlet C2H6/O-2 ratio and N-2 dilution ratio can effectively increase ethylene selectivity. And the reduction of ratio of catalytic active area to geometric area F-cat/geo representing catalyst properties from 140 to 30 increases the selectivity from 42.2% to 59.3%. This research can provide reference for the industrialization of ODHE process in the future. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.