Deactivation Behavior of Co/TiO2 Catalysts during Fischer–Tropsch Synthesis

Kinetic study of Fe & Co perovskite catalyst in Fischer-Tropsch synthesis

The investigation of the reaction's kinetics is one of the most crucial aspects of the design of a commercial process. The current research investigates the kinetics of Fischer-Tropsch synthesis using a perovskite catalyst. The LaFe0.7 Co0.3 O3 perovskite catalyst was prepared via the thermal sol-gel technique and characterized using BET, XRD, SEM, and H2-TPR techniques. According to operating conditions (e.g. H2/CO: 1-2, pressure: 10-20 barg, temperature: 240-300 °C, and GHSV: 3000 1/h), Fischer-Tropsch reaction kinetics (CO conversion) were carried out in a fixed-bed reactor. Using the framework of Langmuir-Hinshelwood-Hougen-Watson (LHHW) theories, 18 kinetic expressions for CO conversion were derived, and all were fitted to experimental data one by one to determine the optimum condition. The correlation was derived from experimental data and well-fitted using LHHW form (according to the enol mechanism, carbon monoxide and dissociated hydrogen atoms are adsorbed and reacted on the surface of the catalyst) -rCO = kpbCOPCO(bH2PH2)0.5/(1 + bCOPCO + (bH2PH2)0.5)2. Finally, the activation energy of the optimum kinetic model was determined with respect to the Arrhenius equation under various operating conditions. The activation energy of perovskite catalyst is about 106.25 kJ/mol at temperatures 240-300 °C, pressures 10-20 barg, and H2/CO ratios 1-2, which is lower than other types of catalyst. Therefore, the catalyst was activated at a high temperature and demonstrated stable performance without any temperature runaway and coking issues.

Production efficiency and safety assessment of the solid waste-derived liquid hydrocarbons

Global fossil resource utilisation remains a concern. Organic fuels and chemicals produced through catalytic synthesis out of biomass/waste feedstock can help reduce the share of fossil resource utilisation. In this study, a solid waste-derived producer gas from the cross/updraft sliding bed gasification process was applied in a fixed bed catalytic reactor with the goal of producing rich hydrocarbon chains. The specific producer gas with CO = 10%vol., H2 = 9%vol. and CH4 = 4%vol. was applied into the catalytic reactor along with catalysts Cat-Co or Cat-CoMnK at 15 bar pressure. Both catalysts were investigated in temperature regimes of 250, 280 and 310 °C, and the liquefaction number and hydrocarbon production were determined. The liquid products were qualitatively analysed afterwards, and the safety assessment, comprising the autoignition test, was performed. The obtained results defined an optimal operating temperature close to 280 °C a value for both catalysts. The individual hydrocarbon compounds were defined mostly by alkanes and alkenes of C10-C14 hydrocarbon groups in the case of both applied catalysts. The application of MnK-promoted catalyst resulted in the production of a significant amount of C6 hydrocarbon groups as well. The results point out a wide range of compounds utilisable in many different applications throughout the production sphere and suggest the possibility of autothermal air gasification of solid recovered fuel with the goal of producing gas for catalytic synthesis with reduced operation costs. From the safety point of view, the temperature of 227.7 °C was defined as the lowest value when autoignition occurs. This lowest temperature is relevant to the Cat-Co 280 °C synthesis scenario.

H2O Derivatives Mediate CO Activation in Fischer-Tropsch Synthesis: A Review

The process of Fischer-Tropsch synthesis is commonly described as a series of reactions in which CO and H₂ are dissociated and adsorbed on the metals and then rearranged to produce hydrocarbons and H₂O. However, CO dissociation adsorption is regarded as the initial stage of Fischer-Tropsch synthesis and an essential factor in the control of catalytic activity. Several pathways have been proposed to activate CO, namely direct CO dissociation, activation hydrogenation, and activation by insertion into growing chains. In addition, H₂O is considered an important by-product of Fischer-Tropsch synthesis reactions and has been shown to play a key role in regulating the distribution of Fischer-Tropsch synthesis products. The presence of H₂O may influence the reaction rate, the product distribution, and the deactivation rate. Focus on H₂O molecules and H₂O-derivatives (H*, OH* and O*) can assist CO activation hydrogenation on Fe- and Co-based catalysts. In this work, the intermediates (C*, O*, HCO*, COH*, COH*, CH*, etc.) and reaction pathways were analyzed, and the H₂O and H₂O derivatives (H*, OH* and O*) on Fe- and Co-based catalysts and their role in the Fischer-Tropsch synthesis reaction process were reviewed.

Recent Advances in the Mitigation of the Catalyst Deactivation of CO2 Hydrogenation to Light Olefins

The catalytic conversion of CO2 to value-added chemicals and fuels has been long regarded as a promising approach to the mitigation of CO2 emissions if green hydrogen is used. Light olefins, particularly ethylene and propylene, as building blocks for polymers and plastics, are currently produced primarily from CO2-generating fossil resources. The identification of highly efficient catalysts with selective pathways for light olefin production from CO2 is a high-reward goal, but it has serious technical challenges, such as low selectivity and catalyst deactivation. In this review, we first provide a brief summary of the two dominant reaction pathways (CO2-Fischer-Tropsch and MeOH-mediated pathways), mechanistic insights, and catalytic materials for CO2 hydrogenation to light olefins. Then, we list the main deactivation mechanisms caused by carbon deposition, water formation, phase transformation and metal sintering/agglomeration. Finally, we detail the recent progress on catalyst development for enhanced olefin yields and catalyst stability by the following catalyst functionalities: (1) the promoter effect, (2) the support effect, (3) the bifunctional composite catalyst effect, and (4) the structure effect. The main focus of this review is to provide a useful resource for researchers to correlate catalyst deactivation and the recent research effort on catalyst development for enhanced olefin yields and catalyst stability.

Solvent Additive-Induced Deactivation of the Cu-ZnO(Al2O3)-Catalyzed γ-Butyrolactone Hydrogenolysis: A Rare Deactivation Process

This work reports initial results on the effect of low concentrations (ppm level) of a stabilizing agent (2,6-di-tert-butyl-4-methylphenol, BHT) present in an off-the-shelf solvent on the catalyst performance for the hydrogenolysis of γ-butyrolactone over Cu-ZnO-based catalysts. Tetrahydrofuran (THF) was employed as an alternative solvent in the hydrogenolysis of γ-butyrolactone. It was found that the Cu-ZnO catalyst performance using a reference solvent (1,4-dioxane) was good, meaning that the equilibrium conversion was achieved in 240 min, while a zero conversion was found when employing tetrahydrofuran. The deactivation was studied in more detail, arriving at the preliminary conclusion that one phenomenon seems to play a role: the poisoning effect of a solvent additive present at the ppm level (BHT) that appears to inhibit the reaction completely over a Cu-ZnO catalyst. The BHT effect was also visible over a commercial Cu-ZnO-MgO-Al₂O₃ catalyst but less severe than that over the Cu-ZnO catalyst. Hence, the commercial catalyst is more tolerant to the solvent additive, probably due to the higher surface area. The study illustrates the importance of solvent choice and purification for applications such as three-phase-catalyzed reactions to achieve optimal performance.

Impact of Coordination Features of Co(II)-Glycine Complex on the Surface Sites of Co/SiO2 for Fischer–Tropsch Synthesis

To investigate the effect of coordination features of Co(II)-glycine complex on the performance of Co/SiO2 for Fischer–Tropsch (FT) synthesis, Co(II)-glycine complex precursors were prepared by the conventional method, i.e., simply adding glycine to the solution of Co nitrate and novel route, i.e., reaction of glycine with cobalt hydroxide. The SiO2-supported Co catalysts were prepared by using the different Co(II)-glycine complexes. It is found that glycine is an effective chelating agent for improving the dispersion of Co and the mass-specific activity in FT synthesis when the molar ratio of glycine/Co2+ = 3, which is independent to the preparation method in this study. Significantly, the surface Co properties were significantly influenced by the coordination features of the Co2+ and the molar ratio of glycine to Co2+ in the Co(II)-glycine complex. Specifically, the Co(3gly)/SiO2 catalyst prepared by the novel route exhibits smaller and homogenous Co nanoparticles, which result in improved stability compared to Co-3gly/SiO2 prepared by the conventional method. Thus, the newly developed method is more controllable and promising for the synthesis of Co-based catalysts for FT synthesis.

Kinetic data acquisition in high-throughput Fischer–Tropsch experimentation

The emergence of high-throughput experimentation gives new opportunities for accurate and rapid data acquisition for a wide variety of chemical reactions in different fields of application such as hydrocracking, isomerization and syngas conversion.

Preparation of Cobalt Nanocrystals Supported on Metal Oxides To Study Particle Growth in Fischer-Tropsch Catalysts

Colloidal synthesis of nanocrystals (NC) followed by their attachment to a support and activation is a promising route to prepare model catalysts for research on structure-performance relationships. Here, we investigated the suitability of this method to prepare well-defined Co/TiO2 and Co/SiO2 catalysts for the Fischer-Tropsch (FT) synthesis with high control over the cobalt particle size. To this end, Co-NC of 3, 6, 9, and 12 nm with narrow size distributions were synthesized and attached uniformly on either TiO2 or SiO2 supports with comparable morphology and Co loadings of 2-10 wt %. After activation in H2, the FT activity of the TiO2-supported 6 and 12 nm Co-NC was similar to that of a Co/TiO2 catalyst prepared by impregnation, showing that full activation was achieved and relevant catalysts had been obtained; however, 3 nm Co-NC on TiO2 were less active than anticipated. Analysis after FT revealed that all Co-NC on TiO2 as well as 3 nm Co-NC on SiO2 had grown to ∼13 nm, while the sizes of the 6 and 9 nm Co-NC on SiO2 had remained stable. It was found that the 3 nm Co-NC on TiO2 already grew to 10 nm during activation in H2. Furthermore, substantial amounts of Co (up to 60%) migrated from the Co-NC to the support during activation on TiO2 against only 15% on SiO2. We showed that the stronger interaction between cobalt and TiO2 leads to enhanced catalyst restructuring as compared to SiO2. These findings demonstrate the potential of the NC-based method to produce relevant model catalysts to investigate phenomena that could not be studied using conventionally synthesized catalysts.

Determining the Catalytic Activity of Transition Metal-Doped TiO2 Nanoparticles Using Surface Spectroscopic Analysis

The modified TiO₂ nanoparticles (NPs) to enhance their catalytic activities by doping them with the five transition metals (Cr, Mn, Fe, Co, and Ni) have been investigated using various surface analysis techniques such as scanning electron microscopy (SEM), Raman spectroscopy, scanning transmission X-ray microscopy (STXM), and high-resolution photoemission spectroscopy (HRPES). To compare catalytic activities of these transition metal-doped TiO₂ nanoparticles (TM-TiO₂) with those of TiO₂ NPs, we monitored their performances in the catalytic oxidation of 2-aminothiophenol (2-ATP) by using HRPES and on the oxidation of 2-ATP in aqueous solution by taking electrochemistry (EC) measurements. As a result, we clearly investigate that the increased defect structures induced by the doped transition metal are closely correlated with the enhancement of catalytic activities of TiO₂ NPs and confirm that Fe- and Co-doped TiO₂ NPs can act as efficient catalysts.

Active phase distribution changes within a catalyst particle during Fischer–Tropsch synthesis as revealed by multi-scale microscopy

A new combination of three chemical imaging methods has been developed and applied to fresh and spent co-based Fischer–Tropsch catalysts.