(64b) Enhancing Performance of Oxidative Coupling of Methane (OCM) Adiabatic Reactors with a Multi-Zone, Multi-Feed Optimization Framework

Oxidative coupling of methane (OCM) is a direct route to convert methane to ethylene, however being a highly exothermic reaction, heat management in OCM is of utmost importance. Majority of current research involves studying OCM by undertaking efficient reactor design. Some of those studies have attempted to optimize and determine the best conditions for OCM in isothermal operation, but not many studies have been undertaken studying OCM in adiabatic operation; which is practical during scale-up. It has also been known that side-feeding the reactants across the bed coupled with staged, intermediate cooling can help improve OCM performance by managing a better temperature profile. Yet, most current studies do not study effects of side-feeding strategies and consider the entire reactor as a single zone. Earlier, we developed, a multi-zone reactor framework, with efficient feeding strategies for OCM, combining principles of optimization along with reactor design. The reactor zones are modeled as fixed, packed-bed, one-dimensional (1-D) and pseudo-homogeneous. The optimal settings for design decisions are identified using Simulated Annealing (SA). In this study, optimum design of the reactor framework is determined by using the overall C­₂ yield as an objective function, starting from a single-zone analysis to eventually modeling about 30 reactor zones. It was found that by sequentially distributing the reactor into more zones with staged, intermediate cooling, the overall C₂ yield was improved from 5.7% in a single-zone case to approximately 46.5% after 30 zones, all while using the same catalyst. Moreover, a stable temperature profile was also obtained with the sequential distribution into multiple zones without compromising on the overall C₂ selectivity. This result has not been reported before especially while studying adiabatic OCM operation on the fixed-bed reactor. The development of the simulator and the implementation of the SA search scheme will be presented in detail. This framework allows room to even study and optimize isothermal operation of OCM given the similar chemistry being used and can be an important precursor in OCM scale-up.