CHARACTERIZATION OF MASS-TRANSFER IN SUPERCRITICAL-PHASE FISCHER-TROPSCH SYNTHESIS REACTION

Mass transfer, which includes the diffusion of either reactant or hydrocarbon products in the supercritical-phase Fischer-Tropsch synthesis reaction, was studied experimentally as well as by numerical simulations. On the diffusion of the reactant gas, the relationship between catalyst effectiveness factor and the catalyst particle size or reaction temperature was studied in supercritical phase, gas phase and liquid phase, respectively. The lowest apparent Arrhenius activation energy appearing in the liquid-phase reaction could be attributed to the lowest catalyst effectiveness factor shown in this reaction phase, which was caused by the slowest diffusion of reactant in the liquid-filled catalyst pores. The higher carbon-chain growth probability achieved on the catalyst calcined at high temperature is attributed partly to the quick diffusion of CO inside the catalyst pellets as well as to the quick transportation of the primary a-olefin products. Secondary reaction and diffusion behavior of the primary a-olefins were studied in the various reaction phases. The effect of catalyst pellet size or contact time is also discussed.