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The kinetics of the Fischer–Tropsch (FT) reaction was evaluated through detailed experimentation with a KMo bimetallic promoted Fe catalyst supported on carbon nanotubes (CNTs). The kinetic tests were conducted in a fixed‐bed reactor under operating conditions of P = 6.9–41.3 bar, T = 543–563 K, H2/CO = 1, gas hourly specific velocity (GHSV) = 2000 h−1. This study aimed to investigate the mechanism prevailing in CO activation and the rate equation for CO consumption during FT reactions over a 0.5K5Mo10Fe/CNTs catalyst. To evaluate the synergistic effects of Fe, Mo, and K phases on the catalyst activity, both fresh and spent catalysts were thoroughly characterized using X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy and energy‐dispersive spectroscopy (SEM‐EDS), X‐ray absorption near edge structure (XANES), and extended X‐ray absorption fine structure (EXAFS) to ascertain the different phases (active sites) present and relevant interactions. Based on the adsorption of carbon monoxide and hydrogen, 22 possible mechanisms for monomer formation were proposed for FT synthesis in accordance with the Langmuir–Hinshelwood–Hougen–Watson (LHHW) and Eley–Rideal (ER) adsorption theories. The best fit kinetic model was identified through a multi‐variable non‐linear regression analysis. The selected mechanistic model was based on carbide formation approach, where H2‐assisted adsorption of CO was considered for the derivation. Kinetic parameters such as activation energy, adsorption enthalpies of H2, and CO were estimated to be 65.0, −13.0, and −54.0 kJ/mol, respectively. Considering the developed kinetic model, the effects of reaction temperature and pressure were assessed on Fischer–Tropsch synthesis (FTS) product distribution. Additionally, the kinetic model was compared with the typical Anderson–Schulz–Flory model, suggesting the effects of water‐gas‐shift and the existence of additional formation pathway such as secondary re‐adsorption of olefins for heavier hydrocarbons. [ABSTRACT FROM AUTHOR]

Hydroprocessing of vegetable oil to high‐quality jet fuel range hydrocarbons (HRJ) plays a significant role in the development of completely interchangeable substitute for conventional petroleum‐derived jet fuel and has drawn the attention of aviation experts due to its capacity to mitigate greenhouse gas emissions associated with the aviation industry. The limited performance of 1 wt. % Sn promoted Fe(3)‐Cu(13)/SiO2‐Al2O3 catalyst in our previous study has been attributed to the successive consideration of one variable at a time in its evaluation. Maximization of oleic acid conversion and selectivity of jet fuel range hydrocarbons from hydroprocessing of oleic acid over 1 wt. % Sn promoted Fe(3)‐Cu(13)/SiO2‐Al2O3 catalyst with the best combination of the process parameter involved via multivariate approach, and evaluation of kinetic and thermodynamic activation parameters is the focus of this study. Reduced cubic oleic acid conversion model and reduced quadratic jet fuel range hydrocarbons selectivity model of high significance levels, adequate precision, and high correlation coefficient were developed. Reaction temperature of 339.5°C, 1.6 MPa H2 pressure, 6.2 wt.% catalyst concentration, and 8.0 h reaction time were optimum process parameters that can maximize oleic acid conversion and selectivity of jet fuel range hydrocarbons at 98.2% and 82.2%, respectively. This process was found to be endothermic, irreversible, and nonspontaneous with 45.8 KJ/mol activation enthalpy of reaction, 0.25 KJ/mol entropy of reaction, and the reaction's Gibb's free energy of 198.8 KJ/mol at 340°C. The minimum energy required for the reaction to take place was evaluated as 50.7 KJ/mol. [ABSTRACT FROM AUTHOR]

Productionof Fischer–Tropsch catalysts is challenging becauseit involves controlling and optimizing multiple parameters in numeroustechnical steps. Here, we present C-supported nanometric Fe and Cocatalysts synthesized by plasma spraying, a method that contractscatalyst production into a single step, in contrast to traditionalmultistep catalyst production by precipitation or impregnation. Thecatalysts were reduced in situand then tested forFischer–Tropsch synthesis in a gas–solid fixed-bed reactorat 230 °C and 30-bar pressure for 24 h. The performance of plasma-synthesizedcatalysts was superior at a gas hourly space velocity of 6,000 mL·gcat–1·h–1, with Fe/C catalysts showing about 30%CO conversion per pass while Co/C catalysts yielded about 20% CO conversion.Identical C-supported Co and Fe catalysts prepared by impregnationor precipitation gave CO conversions of about 7% under similar reactionconditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydroprocessing of oleic acid was done to produce aviation turbine fuel range hydrocarbons. • Sn(1)-Fe(3)-Cu(13)/SiO 2 -Al 2 O 3 was identified as the most promising catalyst. • Catalyst with high oxophilic reduced iron has a positive influence on product selectivity. • Catalyst with high surface area and greater pore volume resulted in high catalyst productivity. • Catalyst with weak metal–support interaction was highly productive for aviation turbine fuel. In this work, the synergistic effects of 1 wt.% Ti, 1 wt.% Zr, and Sn in the range of 0.5−2 wt.% on Fe(3)-Cu(13)/SiO 2 -Al 2 O 3 catalyst were ascertained through extensive characterization and their subsequent evaluation for the production of aviation turbine fuel range hydrocarbons (C 8 -C 16) via hydroprocessing of oleic acid. The largest surface area (571 m2/g) and pore volume (0.65 cm3/g) were obtained from the N 2 physisorption analysis of 1 wt.% Sn-promoted catalyst (E). Cu 2 O and CuO were identified in the X-ray diffractograms (XRD) of all the catalysts except for catalyst E, which revealed only the peaks of Cu 2 O owing to the small particle size of CuO below the threshold of detection of XRD. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of both oxidized and reduced phases of Cu, Fe, Ti, Zr and Sn in their respective catalysts, with the highest and lowest atomic compositions of reduced Fe and CuO, respectively, detected in catalyst E; corroborating findings from XRD analyses. The relatively homogeneous dispersion of phases present in catalyst E (revealed by its smallest crystallite size of 5.1 nm) was also evidenced by the weakest metal-support interaction from the H 2 -TPR analysis of the same catalyst. Hydroprocessing of oleic acid using catalyst E at 320 °C under H 2 pressure of 2.1 MPa and reaction time of 8 h resulted in the highest aviation turbine fuel range hydrocarbons selectivity of 76.8 % and yield of 71.7 %. This was due to its high metal dispersion, desirable textural properties and high oxophilic reduced iron content. [ABSTRACT FROM AUTHOR]