Carbon dioxide hydrogenation over nickel-, ruthenium- and copperbased catalysts: review of kinetics and mechanism

Abstract: This study critically reviews the mechanism of CO2 hydrogenation over Ni, Ru and Cu, and the effect of catalyst properties and operating conditions on reaction kinetics. Most studies have reported the presence of CO and formate species on Ni-, Ru- and Cu-based catalysts, where subsequent conversion of these species depends on the type of catalyst and the physicochemical properties of the catalyst support. Methane is the major product that forms during CO2 hydrogenation over Ni and Ru catalysts, while methanol and CO are mainly produced on Cu catalysts. A different approach for catalyst formulations and/or process development is required where long chain hydrocarbons are desired

Fischer-Tropsch synthesis Over titaniasupported cobalt catalyst : optimum pressure for C5+ hydrocarbons production

Abstract: Fischer-Tropsch (FT) runs were performed using a titania-supported cobalt catalyst at total operating pressures of 1, 10 and 20 bar respectively, to determine the optimal pressure for C5+ hydrocarbons production. The reaction temperature and feed flowrates were kept constant as 220oC and 20 Nml/gCat/min respectively. Lower methane and higher C5+ hydrocarbons selectivities were measured at higher pressure. However the highest rate of C5+ hydrocarbons production was measured at an optimum pressure of 10 bar

Effect of pressure, temperature and steam to carbon ratio on steam reforming of vegetable oils : simulation study

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Simulation of vegetable oils steam reforming process and comparison with literature experimental data

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Effect of space velocity on Fischer-Tropsch reaction over Co/TiO2 catalyst

Abstract: The effect of space velocity on FT reaction has been evaluated over a 10%Co/TiO2 catalyst prepared by incipient wetness impregnation method. The catalyst was tested in a fixed-bed reactor at 220oC, 20 bar and various feed gas space velocities (20, 40 and 60 Nml/gCat/min). The CO consumption rate, olefin to paraffin ratio, C5+ selectivity and the chain growth probability (alpha) were found to increase with an increase in feed gas flow rate. The results were explained in terms of reactants partial pressures and mass transfer in the reactor as function of CO conversion levels

Fischer-Tropsch synthesis over Co/Tio2 catalyst : effect of catalyst activation by CO compared to H2

Abstract: Co/TiO2 catalyst activation for Fischer-Tropsch (FT) reaction by CO in comparison to H2 has been performed. The catalyst, prepared by incipient wetness impregnation, has been characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses after separate reduction using CO and H2 respectively. Temperature programmed reduction (TPR) analyses were also conducted to study the reduction behaviour of the catalyst in presence of H2 and CO respectively. CO improved catalyst reduction and produced a more stable and active catalyst with higher selectivity and yield for C5+ hydrocarbons at extended time-on-stream

Vegetable oil to biofuel by cracking : equilibrium product selectivities

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Effect of temperature on CO rate and product distribution during Fischer-Tropsch reaction over Co/TiO2 catalyst

Abstract: A 10%Co/TiO2 catalyst has been synthesized by incipient wetness impregnation method and tested in a fixedbed reactor at 20 bar and various temperatures to assess the effect of operating temperature on Fischer-Tropsch (FT) reaction. Increasing the operating temperature (from 200oC - 220oC) led to an increase in methane and light product selectivity but increased the CO conversion rate and the net C5+ production rate. Apparent activation energy for CO conversion and light alkanes (up to C4) formation has also been estimated using Arrhenius plot

Fischer Tropsch synthesis over supported cobalt catalysts: effect of ethanol addition, precursors and gold doping

The effect of the addition of ethanol (2% and 6%) during the Fischer-Tröpsch (FT) synthesis has been investigated using a 10%Co/TiO2 catalyst in a stirred basket reactor (T = 220°C, P = 8 bar, H2/CO = 2). The transformation of ethanol vapour (2% and 6% in nitrogen) over the Co/TiO2 catalyst was also studied in the absence of the synthesis gas under FT reaction conditions. Ethanol was observed to be incorporated in the growing chain and was found to (i) increase the selectivity to light products, (ii) increase the olefin to paraffin ratio and (iii) significantly decrease the catalyst activity. These effects were almost completely reversed when the ethanol in the feed was removed. Thermodynamic predictions, TPR and XRD analysis have shown that cobalt metal particles were oxidised to CoO by ethanol but that re-reduction to Co metal was possible when ethanol was removed from the feed stream allowing the catalyst to recover most of its initial performance, in particular when high flow rates were used. The effect of the cobalt carboxylate chain length (C2, C5 and C9) used in the preparation of alumina supported cobalt catalysts has been studied by TPR, XRD and hydrogen chemisorption techniques. The activity and selectivity of the prepared catalysts have been evaluated for the Fischer-Tröpsch (FT) reaction in a stirred basket reactor. It is shown that for catalysts with Co content of 10 wt.% the activity increases as the carboxylate chain length increases while the selectivity towards methane and light hydrocarbons decreases with the carboxylate chain length. The catalyst prepared using cobalt acetate was found to present the highest metal-support interaction and the poorest performance for the Fischer-Tröpsch reaction. When the metal content was increased to 15 wt.% Co and 20 wt.% Co respectively, the metal-support interaction for the catalyst prepared from cobalt acetate significantly decreased making it a better catalyst for the FT reaction compared to the catalysts prepared from C5 and C9 cobalt carboxylates. The effect of the addition of Au to a Co FT catalyst supported on titania, alumina and silica respectively, has been investigated by varying the amount of Au (0.2 to 5 wt.%) added to the catalyst. The catalysts were characterized by atomic absorption spectroscopy, XRD, XPS and TPR analysis. The catalyst evaluation for the Fischer- Tröpsch reaction activity and selectivity was achieved in a fixed bed micro-reactor (H2:CO = 2; 20 bar; 220°C). Addition of Au to supported Co catalysts improved the catalyst reduction and the cobalt dispersion on the catalyst surface. The catalyst activity for the FT reaction and the methane and light product selectivity increased with Au loading in the catalyst

Energy requirement estimates for two step ethanolysis of waste vegetable oils for biodiesel production

ChemCad 6.4 simulation package was used to model a two-step biodiesel production process from waste vegetable oils (WVO) and ethanol using homogeneous acid and alkali catalysts respectively. The developed process flowsheet consisted of pre-esterification and transesterification of WVO, ethanol and glycerol recovery, and biodiesel refining. The energy required for each processing unit as well as the energy required for the whole process have been estimated. Ethanol recovery accounted for the highest portion of the energy required for the entire process estimated as 2.75 MJ per kg of biodiesel produced