Effect of different alumina supports on performance of cobalt Fischer-Tropsch catalysts

LHHW/RSM reaction rate modeling for Co-Mn/SiO2 nanocatalyst in Fishcher-Tropsch synthesis

This study aims to assess the kinetics of Fischer-Tropsch (FT) reaction over the cobalt-manganese nanoparticles supported by silica oxide. Nanoparticles were synthesized by the thermal decomposition method using "[Co(NH3)4CO3]MnO4" complex and characterized by XRD, TEM, and BET techniques. The kinetics of the process were evaluated using a combination of Langmuir-Hinshelwood-Hougen-Watson (LHHW) and response surface methodology. Correlation factors of 0.9902 and 0.962 were obtained for the response surface method (RSM) and LHHW, respectively. The two methods were in good agreement, and the results showed that the rate-determining step was the reaction of the adsorbed methylene with the adsorbed hydrogen atom, and only carbon monoxide molecules were the most active species on the catalyst surface. A temperature of 502.53 K and a CO partial pressure of 2.76 bar are proposed as the optimal conditions by RSM analysis. The activation energy of CO consumption reaction was estimated to be 61.06 kJ/mol.

Facile Preparation and Promising Hydrothermal Stability of Spherical γ-Alumina Support with High Specific Surface Area

It is of great importance to develop a spherical γ-alumina support with high hydrothermal stability to be used in platinum reforming catalyst processes. The porous pseudo-boehmite powder with a high surface area was first synthesized via a simple separate nucleation and aging steps method, and was then used as a precursor to produce a spherical γ-Al2O3 support via an oil–ammonia column method. The as-synthesized pseudo-boehmite has a substantially greater specific surface area of 336.0 m2·g−1 in comparison with the commercial Sasol boehmite powder (293.0 m2·g−1) from Sasol Chemicals. In addition, the as-prepared spherical γ-Al2O3 support derived from the as-synthesized pseudo-boehmite also possesses a higher specific surface area of 280.0 m2·g−1 compared to the corresponding Sasol sample. Moreover, the as-prepared spherical γ-Al2O3 balls demonstrate a much higher specific surface area of 185.0 m2·g−1 compared with the Sasol sample of 142.0 m2·g−1 after hydrothermal tests at 600 °C, suggesting its promising application in the chemical industry.

Thermodynamic Equilibrium Analysis of Product Distribution in the Fischer-Tropsch Process Under Different Operating Conditions

Thermodynamic equilibrium analysis is necessary to provide a fundamental understanding of the distribution of the products formed in the Fischer-Tropsch process. The thermodynamic equilibrium distribution of the products formed at constant temperature and pressure was studied based on the minimization of the total Gibbs free energy of the system. The effects of temperature, pressure, and feed ratio on the product distribution were investigated under typical operating conditions. The distribution of the total products obtained from the reactions of added ethylene or ethanol was also studied. The results indicated that the products formed in a state of thermodynamic equilibrium follow Anderson-Schulz-Flory's general polymerization distribution at carbon numbers greater than about three. Both olefins and paraffins are primary products and there are essentially no alcohol and water at high degrees of conversion when the conditions for thermodynamic equilibrium are satisfied. The olefins formed in the Fischer-Tropsch process consist essentially of propylene. The product distribution is very sensitive to feed composition, and to temperature and pressure to a lesser extent. The product spectrum can be described broadly by the probability of chain growth relative to chain termination. This parameter decreases with increasing temperature, the feed ratio of hydrogen to carbon monoxide, and after the addition of ethanol to the feed, but increases with increasing pressure and after the addition of ethylene to the feed. An increase in reaction temperature results in a shift in selectivity towards low carbon number hydrocarbons and more hydrogenated products.

Mesoporous Fe-based spindles designed as catalysts for the Fischer–Tropsch synthesis of C5+ hydrocarbons

Novel active phase assembled mesoporous spindles are designed. This unique structure avoids metal-support interactions and displays high C₅₊ selectivity.