Liquid Phase Fischer-Tropsch Synthesis Research Articles

Ru-doped transition metal catalysts for liquid-phase Fischer–Tropsch synthesis

In this paper the catalytic activity of the Ru-doped polymer-based catalysts synthesized by the hydrothermal deposition is described. The catalytic properties of the synthesized systems were studied in the liquid-phase Fischer–Tropsch synthesis for the production of liquid gasoline and diesel-range hydrocarbons. The catalysts showed high CO hydrogenating activity allowing more than 20% of CO conversion to be obtained for one cycle. The yield of liquid hydrocarbons (mainly linear C5-C13) was found to be more than 80%. The addition of the ruthenium to the commonly used Co, Ni, and Fe enhances both the catalytic activity and the yield of the liquid hydrocarbons. The catalysts seem to be stable for minimum 80 h on stream.

Modification of the hypercrosslinked polystyrene surface. New approaches to the synthesis of polymer-stabilized catalysts

The structure and activity of novel combined ruthenium-containing catalysts based on hypercrosslinked polystyrene modified with Fe3O4 and SiO2 were studied. The modification of the polymeric support surface aimed at imparting new properties to the catalysts is a prospective approach for the development of highly efficient catalytic systems involved in various processes. The synthesized samples are characterized by a high specific surface area and a high catalytic activity in the liquid-phase Fischer—Tropsch synthesis providing a yield of liquid hydrocarbons C6-C12 up to 82%.

Ru-содержащие катализаторы для жидкофазного синтеза Фишера-Тропша

The search for new stable and active catalysts of Fischer-Tropsch synthesis is one of the key directions for production of liquid fuels from alternative raw materials. Stabilization of the active phase is the main task in the development of catalysts for hydrogenation of CO into liquid fuels. This problem can be solved by choosing the optimal support, as well as the synthesis method. This work is devoted to the development of new polymer mono– and bimetallic Ru-containing catalysts for liquid phase Fischer-Tropsch synthesis. It is shown that the use of 1% Ru-HPS and 10% Co — 1% Ru-HPS allows to obtain a high yield of gasoline hydrocarbons (more than 70%), providing a high conversion of CO (up to 23%). The selected polymer-based systems showed high stability in the Fischer-Tropsch synthesis process.

Study of the Structure of Cobalt-Containing Catalysts Synthesized under Subcritical Conditions

A physicochemical study of cobalt-containing (10 wt %) silica-supported Fischer–Tropsch catalysts was carried out. The catalysts were obtained under subcritical conditions (T = 200°C, P = 8 MPa) using water (Tc = 374.1°C, Pc = 22.1 MPa) and propanol-2 (Tc = 235.6°C, Pc = 5.8 MPa). The obtained samples were compared with a 10 wt % Co/SiO2 catalyst prepared by incipient-wetness impregnation. Comparison of the properties of catalysts in the liquid-phase Fischer–Tropsch synthesis showed that the sample prepared in subcritical water was the most active and selective to aliphatic C6–C7 hydrocarbons. This sample is characterized by a high surface area (131.7 m2/g), a uniform distribution of particles in the active phase with an average size of 5 nm and higher accessibility of cobalt species for reagents. According to XPS data, the composition of catalyst active phase is mainly represented by two compounds: Co(OH)2 and Co3O4.

Co- and Fe-containing Silica-based Catalysts Synthesized in Subcritical Water

A study of the structure and catalytic properties of the cobalt- and iron-containing catalysts synthesized by the subcritical deposition in the water medium was performed in the current work. The catalyst synthesis was carried out at a temperature of 200 °C and a total pressure of 7.5 MPa using silica as support. The catalytic activity of the synthesized materials was studied in the liquid-phase Fischer-Tropsch synthesis. The study of catalyst structure and composition showed that the use of silica as catalyst support allows the formation of Co- and Fe-containing particles consisted of metal oxides. Testing of the synthesized catalysts in liquid phase Fischer-Tropsch synthesis showed that Co-based catalyst allowed the formation of gasoline-range hydrocarbons. It is noteworthy that Co/SiO2 showed higher selectivity towards the formation of linear C5-C8 hydrocarbons. In the case of Fe-containing catalyst, the formation of a significant amount of oxygenates (C3-C4 alcohols) was found.

A density functional theory based elementary reaction mechanism for early steps of Fischer-Tropsch synthesis over cobalt catalyst. 2. Microkinetic modeling of liquid-phase vs. gaseous-phase process

The process of Fischer-Tropsch synthesis (FTS) is conducted commercially under both gaseous- and liquid-phase conditions. For decades, numerous studies have been performed to better understand this heterogeneous catalytic process, where some of them have tried to compare the reaction rates and product distributions of FTS under different phase conditions. In spite of several provided models, the actual reaction mechanisms and kinetics of important elementary steps at each phase condition are still under investigation, especially in the liquid-phase. In this work, we have utilized the generalized-gradient approximation method of density functional theory (DFT-GGA) to estimate the rate parameters of elementary reactions in liquid-phase FTS on a flat Co(0001) catalyst surface. In this regard, using the continuum-based conductor-like screening model (COSMO) for the liquid solvent environment, the activation energies and rate constants of individual reactions, suggested in an existing microkinetic model, have been calculated in the presence of n-hexane solvent at T=493K and P=25bar. The preferred reaction pathway has been discussed and the quantitative results have been compared to that of the gaseous-phase in order to find the impact of liquid solvent, as well as differences in the probable surface reactions under each phase condition. It has been found that while the carbide mechanism is the dominant mechanism of chain growth under both phase conditions, the presence of the liquid solvent enhanced the CO insertion sub-mechanism of chain growth, which can describe some of the experimental observations in FTS studies.

Synthesis of iron nanoparticles in water-in-oil microemulsions for liquid-phase Fischer–Tropsch synthesis in polyethylene glycol

Abstract Iron nanoparticles were prepared by chemical reduction in water-in-oil microemulsions. The investigation on the microemulsion compositions indicated that the size and morphology of iron nanoparticles were affected by the size and interfacial property of microemulsion droplets. The resultant particles were characterized to be mainly amorphous Fe–B alloys. Selected nanoparticles with spherical and rod-like morphologies were dispersed in polyethylene glycol (PEG) for Fischer–Tropsch synthesis (FTS) under mild conditions. The results revealed that the nanoparticles exhibited high activities and the product distribution slightly shifted to heavier hydrocarbons on the rod-like nanoparticles.

Effects of impregnation solvent on Co/SiO2 catalyst for Fischer-Tropsch synthesis: A highly active and stable catalyst with bimodal sized cobalt particles

Silica-supported cobalt (20 wt%) catalysts were prepared by incipient-wetness impregnation of silica with different cobalt nitrate solutions. The catalyst prepared from dehydration ethanol solution exhibited stable and the highest activity, as well as significantly low methane selectivity. Cobalt crystalline size of the catalyst prepared from dehydrated ethanol was smaller than that of the catalyst prepared from aqueous solution, and existed two different size where the large particles showed low bulk density with cluster-like structure. But only larger clusters existed in the catalyst prepared from aqueous solution. The increased amount of active sites and more reactive adsorbed CO on the surface determined the highest activity of the catalyst prepared from dehydrated ethanol solution in liquid-phase Fischer-Tropsch synthesis (FTS) reaction.

The effect of acetic acid pretreatment for cobalt catalysts prepared from cobalt nitrate

Abstract The effects of acetic acid pretreatment for dried catalysts prepared from cobalt nitrate were investigated. Cobalt catalyst prepared from cobalt nitrate, followed by treatment of 2.2 M acetic acid, namely CoN/2.2Ac catalyst, showed the highest CO conversion as well as the lowest CO2 and CH4 selectivities in liquid-phase Fischer–Tropsch synthesis. On the contrary, cobalt catalyst prepared from cobalt acetate exhibited poor catalytic activity due to very low reduction degree of supported cobalt. The higher catalytic activity for CoN/2.2Ac catalyst could be ascribed to the formation of the mixture of cobalt nitrate and cobalt acetate with suitable ratio between them during acetic acid treatment, which led to an optimum balance between the dispersion and reduction degree of supported cobalt, eventually realizing the higher catalytic activity. Various catalysts were characterized by XRD, TPR and H2 chemisorption.

Development of bimodal cobalt catalysts for Fischer–Tropsch synthesis

A new and simple method for preparing multi-functional nano-sized silica-silica or zirconia-silica bimodal pore catalyst support was developed by direct introduction of silica or zirconia sols into silica gel. The pores of the obtained bimodal pore supports distributed distinctly as two kinds of main pores. On the other hand, the increased BET surface area and decreased pore volume, compared to those of original silica gel, indicated that the obtained bimodal pore supports formed according to the designed route, and it is found that the zirconia-silica bimodal support improved catalyst activity significantly via not only spatial effect, the intrinsic property of the bimodal structure, but also chemically promotional effect of zirconia, when this kind of support was applied in the liquid-phase Fischer–Tropsch synthesis (FTS) as a cobalt-loading catalyst.

New bimodal pore catalysts for Fischer–Tropsch synthesis

A simple preparation method of bimodal pore supports was developed by introducing SiO 2 or ZrO 2 sols into large pores of SiO 2 gel pellets directly. The pores of the obtained bimodal pore supports distributed distinctly as two kinds of main pores. On the other hand, the increased BET surface area and decreased pore volume, compared to those of original silica gel, indicated that the obtained bimodal pore supports formed according to the designed route. The obtained bimodal pore supports were applied in liquid-phase Fischer–Tropsch synthesis (FTS) where cobalt was supported. The bimodal pore catalysts presented the best reaction performance in liquid-phase Fischer–Tropsch synthesis (FTS) as higher reaction rate and lower methane selectivities, because the spatial promotional effect of bimodal pore structure and chemical effect of the porous zirconia behaved inside the large pores of original silica gel.

A New Preparation Method of Bimodal Catalyst Support and Its Application in Fischer–Tropsch Synthesis

The silica-based supports that contained distinct bimodal structure were prepared by incipient-wetness impregnation of silica or zirconia sols into the large pores of silica gel. The pore-size distributions of the obtained supports proved that two kinds of pores coexisted according to the bimodal structure. For these bimodal supports, the increased specific surface area and decreased pore volume indicated that the particles of silica or zirconia sols had entered the large pores of the silica gel. The obtained supports were applied in liquid-phase Fischer–Tropsch synthesis (FTS) after cobalt had been loaded. The catalytic properties of these catalysts exhibited increased activity and decreased selectivities of CH4 and CO2 due to the spatial promotional effect of the bimodal pore structure and chemical effects of the porous zirconia inside the large pores of the original silica gel.

Overview of reactors for liquid phase Fischer–Tropsch synthesis

The following overview is divided roughly into three sections. The first section covers the period from the late 1920s when the first liquid phase synthesis was first conducted until about 1960 when the interest in Fischer–Tropsch synthesis (FTS) declined because of the renewed view of an abundance of petroleum at a low price. The second period includes the activity that resulted from the oil shortage due to the Arab embargo in 1972 and covers from about 1960 to 1985 when the period of gloomy projections for rapidly increasing prices for crude had faded away. The third section covers the period from when the interest in FTS was no longer driven by the projected supply and/or price of petroleum but by the desire to monetize stranded natural gas and/or terminate flaring the gas associated with petroleum production and other environmental concerns (1985 to date). These sections are followed by a brief overview of the current status of the scientific and engineering understanding of slurry bubble column reactors.

A new method of bimodal support preparation and its application in Fischer–Tropsch synthesis

A simple preparation method of bimodal silica was developed by introducing SiO 2 sol into large pores of SiO 2 gel pellet directly. Cobalt supported on this kind of bimodal silica support, exhibited remarkably high activity in liquid-phase Fischer–Tropsch synthesis, which was attributed to its bimodal structure having not only a higher surface area but also a larger pore size. The support with a large surface area allowed highly dispersed cobalt particle and its large pore size improved the diffusion of reactants and products.

96/00201 Ultrafine particles of cobalt as the catalyst for liquid phase Fischer-Tropsch synthesis

96/00201 Ultrafine particles of cobalt as the catalyst for liquid phase Fischer-Tropsch synthesis

The formation of cobalt silicates on Co/SiO2 under hydrothermal conditions

A Co/SiO2 catalyst recovered after both gas and liquid phase Fischer-Tropsch synthesis exhibited significant decreases in the amount of reducible metal. Hydrothermal conditions similar to those occurring during Fischer-Tropsch synthesis were simulated in order to study compound formation in this Co/SiO2 catalyst. Hydrothermal treatment at 220°C led to a catalyst with lower reducibility, attributable to the formation of both reducible and nonreducible (<900°C) Co silicates. The formation of these compounds occurred only when metallic Co was present, was more pronounced in the presence of hydrogen, and was inhibited by air.

Effects of Cr Addition on the Catalytic Properties of Ultrafine Particles of Co for Liquid Phase Fischer-Tropsch Synthesis.

The activities of Co-based ultrafine particles (UFP) catalysts for slurry phase Fischer-Tropsch (FT) synthesis were investigated at 270°C and 30atm. Among the catalysts tested, Co-Cr UFP catalyst exhibited the highest activity. The activity and the selectivity of Co-Cr UFP catalyst for liquidhydrocarbon production increased with increasing content of Cr, and it attained a maximum at about 2wt%. Co-Cr supported on SiO2 exhibited similar catalytic performances as those of Co-Cr UFP. There was a good relationship between catalytic activity and chemisorptive uptake of CO. Reducibility of Co was improved in the presence of Cr. Thus, we deduce that there was a maximum number of active sites due to the promoting effects of Cr on reduction of Co and on sintering of Co. Product distribution was found to be affected only by the size of Co particles.

Liquid Phase Hydrogenation of Carbon Monoxide Using Ultrafine Particles of Cobalt as Catalyst.

Liquid phase Fischer-Tropsch synthesis was investigated with ultrafine particles (UFP) composed of Co. The catalytic activity of Co UFP was higher than that of precipitated Co catalyst. Apparent activation energies on Co UFP and the precipitated Co were found to be 16, and 10kcal/mol, respectively. Furthermore, Co UFP exhibited very low selectivity for methane formation compared with the precipitated catalyst. The activity and selectivity of Co catalyst supported on SiO2 for production of higher hydrocarbons increased, and the apparent activation energy increased with increasing pore diameter of SiO2 support. These results indicated that the reaction on the precipitated catalyst was affected by diffusion of the reactant into the pores. We conclude that nonporous structure of Co UFP provided high catalytic activity and selectivity for higher hydrocarbons.

Liquid phase Fischer-Tropsch synthesis on manganese-promoted ultrafine particles of iron used as a catalyst

The catalytic properties of manganese-promoted ultrafine particles (UFP) of iron for liquid phase Fischer-Tropsch (FT) synthesis have been investigated. Manganese-promoted iron UFP catalysts were prepared by physically mixing iron UFP and manganese oxide or by liquid phase deposition of manganese on iron UFP. These catalysts were highly selective for alkene production. In particular, the selectivity to lower alkenes over catalysts prepared by liquid phase manganese deposition was enhanced by the addition of extremely small amounts of manganese (several percent of iron). These catalysts gave very high yields of lower alkenes.

Liquid phase Fischer—Tropsch synthesis on ultrafine particles of iron: Effect of preoxidation treatment

The effect of the oxidative pretreatment of ultrafine particles (UFP) of iron on their catalytic properties in the liquid phase Fischer—Tropsch synthesis has been investigated. Although similar product distributions were obtained, whether preoxidized or not, the catalytic activities of the preoxidized catalysts, which were prepared by exposure of the iron UFP to an atmosphere of nitrogen containing the predetermined amounts of oxygen, were higher than that of the untreated iron UFP. The catalytic activity is discussed in relation to the sintering of the UFP catalyst under the reaction conditions used.