The kinetics of Fischer-Tropsch synthesis (FTS) over a 25%Co/Al2O3 catalyst was studied using a 1-L continuously stirred tank reactor (CSTR) under the conditions of 205-230 degrees C, 1.4-2.5 MPa, H-2/CO = 1.0-2.5 and 3-16 NL/g-cat/h (X-CO = 7-54%). Thirty-one sets of kinetic data collected at 220 degrees C with a low extent of deactivation were used for kinetic parameter regression. The CAER empirical kinetic model (r(FT) = kP(CO)(a) P-H2(b)/(1 broken vertical bar mP(H2O)/PH2)) was employed to study the kinetic effect of water. A positive kinetic water effect was first evidenced using the kinetic approach, consistent with the results of the effect of co-fed water on cobalt FTS in this work and the literature (e.g. Loegdberg et al., 2011 [21]) for CO/Al2O3 catalysts. The current kinetic results are based on kinetic data taken following an initial catalyst induction period, where the CO conversion had stabilized. These data are different from our earlier investigations where reversible oxidation of small cobalt crystallites and/or catalyst support effects likely impacted the cobalt site densities, resulting in a negative water effect. Thus, in this study, we decoupled the effect of reversible oxidation from the kinetics, so that the effect of water on stable (i.e., presumably larger) metallic cobalt particles could be assessed.In this study, an additional eleven classical FT kinetic models for Co catalysts were tested using the kinetic data. Five of them were also found to adequately describe the kinetic data, including two mechanistic models developed based on carbide mechanisms. The CAER model containing a water effect term and the mechanistic model of Botes et al. (2009) [31] yielded comparable reaction orders for the partial pressures of H-2 and CO, resulted in a better fit of the kinetic data. (C) 2013 Elsevier B.V. All rights reserved.

Modeling of the supercritical fluid mixture indicated that an important increase in density occurs above a threshold of approximately 4 MPa for the reaction temperature of 220degreesC studied. While transport parameters of the fluid are largely retained, the observed improvement in wax solubility was noteable.A cobalt catalyst (25%Co/-gamma-Al2O3) was used in a fixed bed reactor under a pressure/density tuned supercritical fluid mixture of n-pentane/n-hexane. By using inert gas as a balancing gas to maintain a constant pressure, the density of the supercritical fluid could be tuned near the supercritical point while maintaining constant space velocity within the reactor. The benefits of the mixture allowed for optimization of transport and solubility properties at an optimum reaction temperature for Fischer-Tropsch synthesis with a cobalt catalyst. Indeed, above 4 MPa, increases in wax yields from sampling and carefully controlled gas measurements using an internal standard demonstrated an important increase in conversion due to greater accessibility to active sites after extraction of heavy wax from the catalyst. Additional benefits included decreased methane and carbon dioxide selectivities. Decreased paraffin/(olefin + paraffin) selectivities with increasing carbon number were also observed, in line with extraction of the hydrocarbon from the pore. Faster diffusion rates of wax products resulted in lower residence times in the catalyst pores, and therefore, decreased probability for readsorption and reaction to the hydrogenated product. Even so, there was not an observable increase in the alpha value for higher carbon number products over that obtained with just the inert gas. (C) 2003 Elsevier Science Ltd. All rights reserved.

A Slurry Bubble Column Reactor (SBCR) is a gas-liquid-solid reactor in which the finely divided solid catalyst is suspended in the liquid by the rising gas bubbles. SBCR offers many advantages over fixed-bed type reactors such as: 1) improved heat transfer and mass transfer; 2) isothermal temperature profile is maintained; and 3) relatively low capital and operating cost. Fischer-Tropsch Synthesis (FTS) takes place in a SBCR where the synthesis gas is converted on catalysts suspended as fine particles in a liquid. The synthesis gas flows in a bubble phase through the catalyst/wax suspension. The volatile products are removed with unconverted gases, and the liquid products are separated from the suspension. A gas distributor located in the bottom of the reactor produces the bubbles in the reactor.A considerable interest has been expressed in using the SBCR to carry out FTS particularly for the conversion of stranded natural gas into liquids. Currently, the Center for Applied Energy Research (CAER) is utilizing a Prototype Integrated Process Unit (PIPU) system for scale-up research of the FTS. The purpose of this study was to compare the performance and activity decline of a precipitated Fe/K Fischer-Tropsch Synthesis (FTS) catalyst in a revamped slurry bubble column reactor (SBCR) to that of previous CSTR and SBCR runs using the same catalyst and operating conditions. The activity decline measured in the revamped SBCR system was shown to be similar to that of the CSTR experiments. The apparent activity decline in a previous SBCR run was due a transient startup effect from the slurry filtration system.

The goal of our work is to develop a catalyst with a high selectivity for straight α-chain olefins and wax by optimizing promoters and reaction conditions. The effects of potassium and copper promotion on the activity and selectivity of precipitade iron catalysts used in the slutrry phase Fischer Tropsch synthesis is the subject of this work

The data presented in this study illustrate the similarities and differences in the yield and selectivities obtained from different types of coal liquefaction reactors. The results suggest that the comparison of data in the literature obtained from different reactors should be done with careful consideration. The differences and similarities in the yields obtained depend not only on the reactor type but also on the feedstock employed and the residence time in the reactors. Data generated using microreactors are adequate for the selection of operating conditions for conversion in larger scale reactors.