Fischer–Tropsch synthesis using Co and Co-Ru bifunctional nanocatalyst supported on carbon nanotube prepared via chemical reduction method

We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co(0.1 to 0.4 wt%) with keeping a fixed amount of cobalt(10 wt%). Moreover, for comparison purpose, CNTs supported Co-and Co(Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy–dispersive X-ray(EDX), Transmission Electron Microscopy(TEM), Brunauer–Emmett–Teller(BET),Hydrogen-Temperature-Programmed Reduction(H_2-TPR), Hydrogen-Temperature-Programmed Desorption(H_2-TPD) and O_2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst prepared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demonstrated that the use of chemical reduction method led to decrease the average Co oxide cluster size to8.7 nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons(C_(5+)), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/γ-Al_2O_3(61._20%), Co/CNTs(43.68%) and Co/γ-Al_2O_3(37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C_(5+) selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst.

Fischer-Tropsch Reaction Kinetics of Cobalt Catalyst in Supercritical Phase

Fischer-Tropsch synthesis under supercritical phase condition was examined in a continuous and a high-pressure fixed bed reactor by employing a cobalt catalyst （Co-Ru/γ-Al2O3）. An integral reactor model involving Fischer-Tropsch reaction kinetics in the supercritical fluid n-hexane was used to describe the overall performance. On the basis of Langmuir-Hinshelwood-Hougen-Watson （LHHW） model, the reaction rate constants were obtained for the rate equations of CO conversion to CH4 formation under supercritical conditions.

Implementation of electrolyte CPA EoS to model solubility of CO2 and CO2+ H2S mixtures in aqueous MDEA solutions

The electrolyte version of SRK plus association equation of state(e SRK-CPA Eo S) was employed to correlate CO2 solubility in MDEA aqueous solutions. The applied model comprises the classic form of CPA Eo S including SRK Eo S plus Wertheim association term in addition to MSA theory and Born terms so that the two last terms are responsible for the long-range interactions. A reaction-containing bubble pressure computation technique comprising two nested loops was utilized to model the systems. The internal loop, calculates the liquid phase concentrations via reaction, mass and charge balance equation solving, whereas, the vapor phase concentrations will be obtained in the external one. 470 experimental data were used to correlate binary subsystems and the H2O + MDEA + CO2 ternary system. Since, there not exist any binary VLE data for MDEA + CO2 subsystem, two fitting scenarios were applied. At the first scenario, the binary interaction parameter was assumed equal to zero, while, in second approach the parameter was obtained through ternary system correlation. Both scenarios show very good accuracy in that the Absolute Average Deviation percentages(AAD) obtained were 19.12% and 18.85%, respectively. Also, to show the efficiency of the used model, a comparison between our results and those of the best-known models was made.Finally, having model parameters for H2S solubility from our previous work [A. Afsharpour, Petroleum Science and Technology 35(3)(2017) 292-298], simultaneous solubility of CO2+ H2S mixtures in MDEA solutions was predicted using the e SRK-CPA Eo S with no new optimizable parameters. As the results show,the applied model has a good performance for correlation and prediction of acid gas solubility in a wide range of pressures, temperatures, acid gas loadings, and MDEA concentrations.

Comprehensive study of nanostructured supports with high surface area for Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure -y-alumina, single wall carbon nanotubes （SWNTs）, and the hybrid of SWNTs/nanostructure -y-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer- Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions （220-240 ℃, 15-25 bar, H2/CO ratio of 2, GHSV of 900-1400） in order to study the effects of temperature, pressure and gas hourly space velocity （GHSV） changes on hydrocarbon selec- tivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, inductively coupled plasma （ICP）, hydrogen （H2） chemisorption and temperature-programmed reduction （TPR）. The results showed that the yield of hybrid supported catalyst （55.4%） is higher than that of nanos- tructure -y-alumina supported catalyst （55.0%） and lower than that of SWNTs supported cobalt catalyst （71.0%）. The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selec- tivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.