Integrated autothermal oxidative coupling and steam reforming of methane. Part 1: Design of a dual-function catalyst particle

Abstract

A dual-function catalyst particle which integrates the exothermic oxidative coupling and endothermic steam reforming of methane for the simultaneous autothermal production of ethylene and synthesis gas has been designed and studied by detailed numerical simulations. Compared to conventional oxidative coupling of methane, the introduction of a catalytic reforming activity significantly increases the methane conversion without deteriorating the productivity towards the desired ethylene and ethane. Moreover, the presence of an intra-particle heat sink enables local autothermal operation, opening the possibility to couple these reactions in a packed bed membrane reactor with improved product yield. It is proposed to use a catalyst particle in which the two processes are physically separated by an inert, porous layer, such that additional diffusional resistances are intentionally created. The reforming activity is located in the particle center, while the oxidative coupling catalyst is present only in the outer shell of the particle.It has been demonstrated by means of numerical simulations that at low oxygen concentration (representing conditions in a packed bed membrane reactor), the internal mass transfer limitations can be effectively utilized to regulate the total reforming reaction rates and to prevent oxygen from reaching the reforming catalyst. Additionally, the size of the reforming catalytic core can, together with the effective diffusion properties inside the particle (viz. particle porosity and tortuosity) and the bulk gas phase concentrations, be used to tune the process to local autothermal operation.