Simultaneous hydrogen injection and in-situ H2O removal in a novel thermally coupled two-membrane reactor concept for Fischer–Tropsch synthesis in GTL technology

Abstract

Gas-to-Liquids (GTL) technology converts natural gas, through Fischer–Tropsch synthesis, into liquid and ultra-clean hydrocarbons such as gasoline, light oils, naphtha, diesel, and wax. In this study, a novel thermally coupled multi-tubular two-membrane reactor (TCTMR) is proposed in order to enhance of gasoline production. Fischer–Tropsch synthesis is carried out in the exothermic side with two different membranes and supplies the necessary heat for the endothermic side. Decomposition of ammonia is carried out in the endothermic side with hydrogen-permselective Pd/Ag membrane layer. Therefore, the proposed reactor consists of two different membranes, one for permeation of pure hydrogen from exothermic into endothermic side and another one for separation of water from exothermic side. Water produced during FTS negative influences the reaction by re-oxidation of catalysts, increasing water/gas shift activity and decreasing partial pressures of the products. A steady-state heterogeneous model of the two fixed beds predicts the performance of this novel configuration. The achieved results of this simulation have been compared with the results of the conventional fixed-bed reactor (CR) at identical process conditions. The simulation results show 27.14% enhancement in the gasoline yield and 35.2% decrease in CO2 yield of TCTMR in comparison with the one in CR due to a favorable profile of temperature along the TCTMR.