Catalysis in Industry最新文献

Silica gels are porous materials that are commonly used both in industry and in everyday life. Russian manufacturers produce spherical and powdered silica gels; however, a number of fields of application of silica gels are entirely dependent on import. Therefore, it is necessary to develop silica gel production technologies, the introduction of which would make it possible to replace imported silica gels. Methods for improving the properties of spherical silica gels and new solutions for the production of SiO₂, in particular, silica gel powders and silica gels with an ordered pore structure, are described. It is proposed that they should be produced using cheap feedstocks, in particular, the aluminum industry waste Si-stoff and the cheap natural material diatomite. It is shown that control of the silica precipitation and structure formation parameters provides the formation of silica gels with a wide range of pore structure characteristics, which makes it possible to use them in various fields.

The isomerization of heptane and hexane and their mixtures in the presence of Pt/WO₃–ZrO₂ catalysts with a tungsten oxide content of 10–35 wt % has been studied. It has been shown that the best parameters of the isomerization of a mixture of C₆–C₇ alkanes are achieved in the presence of catalysts containing 15–20 wt % WO₃. According to temperature-programmed desorption of ammonia, this range of tungsten oxide content is characterized by an increase in the number of acid sites, which, according to IR spectroscopy of adsorbed CO molecules, occurs mostly due to an increase in the number of Brønsted acid sites.

Amorphous aluminosilicate‒alumina systems are investigated by a set of physicochemical means that includes studying the NMR ²⁷Al spectra of solid samples and the acidity of catalysts via ammonia temperature-programmed desorption, a structural X-ray diffraction study, and a thermogravimetric analysis of samples. Studying the catalytic properties of samples under the conditions of cracking on a model feedstock of n-dodecane in a mixture with 2-methylthiophene shows that the conversion of feedstock grows in the order 100% Al₂O₃ (AHO) > 70% Al‒Si + 30% Al₂O₃ (AHO) > 30% Al‒Si + 70% Al₂O₃ (AHO) > 100% Al‒Si (where AHO is the aluminum hydroxide of sulfate synthesis, and Al‒Si is an amorphous aluminosilicate). Raising the calcination temperature of samples from 500 to 700°C reduces the conversion of feedstock. Increasing the contribution from hydrogen transfer reactions leads to an increase improves the selectivity toward hydrogen sulfide and lowers the content of sulfur compounds in the liquid products.

The authors consider the main possibilities of using gas chromatography to study catalysts and catalytic processes. The development of sampling along with microcatalytic and pulsed means is shown in a historical context. Current promising areas of gas chromatographic studies and equipment for the effective separation of multicomponent mixtures of substances governed by the progress of complex catalytic reactions are reviewed.

Results from the prolonged tests of zeolite-containing cobalt catalysts for Fischer–Tropsch synthesis in reactor tubes comparable in size to those used in industrial reactors. During 3000 hours on stream catalyst activity was decreased by 13%. It is shown that the main reasons for zeolite-containing cobalt catalyst deactivation are agglomeration of cobalt clusters and carbon deposition on the catalyst surface. The authors propose one method of reducing the catalyst deactivation rate and two methods of regenerating it. It is shown that the oxidative regeneration treatment of zeolite-containing cobalt catalysts allows to recover 98% of the initial activity.

The iron-based catalysts were prepared via wet-impregnation method. The composition of the final iron catalysts, regarding to the weight ratio is as follow 14%Fe/γ-Al₂O₃, 14%Fe/3%Cu/γ-Al₂O₃, 14%Fe/3%Sn/γ-Al₂O₃ and 14%Fe/3%Cu/1%Sn/γ-Al₂O_3. The catalysts were characterized using XRD, ICP, BET, H₂-TPR, FE-SEM and EDX techniques. The catalytic activity was evaluated in a fixed bed reactor under 2.0 MPa of pressure, H₂ : CO = 1 : 1, GHSV = 2 L h^–1 ({text{g}}_{{{text{cat}}}}^{{-1}}), in the temperature range of 270–300°C. Then, the effect of temperature and promoters (Cu and Sn) on the catalyst performance was investigated. CO conversion and product selectivity were also calculated using the results of GC. The results showed that the Cu and Sn promoters increased the reduction rate of Fe₂O₃ by providing H₂ dissociation sites. Higher temperatures were also shown to change the CO conversion and product selectivity. The selectivity of both methane and C₂–C₄ hydrocarbons decreased while the selectivity of C₅₊ increased because of simultaneous use of Cu and Sn for promoting iron catalyst. Sn promoter increased FT and WGS activities.

The effect of adding clay with different contents of iron oxides to a catalytic cracking system on the distribution of feedstock sulfur in synthesized products and the amount of sulfur oxides formed during the regeneration of coked catalyst after the cracking of a model sulfur-containing feedstock with a sulfur content of 10 000 ppm, derived from 2-methylthiophene or benzothiophene has been studied. The fraction of the feedstock sulfur converted into liquid products and coke can be seen to grow when a sulfur-containing component with a higher molecular weight is used. Raising the content of iron oxide in the catalyst from 0.61 to 1.53 wt % increases the yield of liquid products during the cracking of a model feedstock, reduces the conversion of a model hydrocarbon. The yield of coke on the catalyst grows from 3.8 to 5.2 wt %, and the fraction of feedstock sulfur converted into SO₂ quadruples.

Results from calculating the thermochemical properties of molecules and the thermodynamic characteristics of vacuum distillate hydrotreatment reactions by quantum-chemical methods are presented. A mathematical hydrotreatment model is developed on the basis of a formalized scheme of reactions for hydrocarbons. The developed kinetic model is used in numerical studies to estimate the effect of the feedstock composition on the residual content of heteroatomic compounds in the vacuum gasoil hydrotreatment product, the effect of the temperature on the content of aromatic hydrocarbons, nitrogen, and sulfur in the hydrotreatment product, and flow rate of the hydrogen-containing gas on the content of sulfur and hydrogen sulfide in hydrotreated vacuum gasoil.

The fine crystal structure of hematite samples used for preparing potassium promoted iron oxide catalysts of dehydrogenation is studied via X-ray diffraction and scanning electron microscopy. α-Fe₂O₃ samples are synthesized under non-equilibrium conditions from several precursors in different regimes of thermolysis. The most important characteristic of hematite that causes the activity and selectivity of a hematite-based catalyst is its fine crystal structure (FCS). The fine crystal structure of hematite predetermines the phase composition of the catalyst. The fine crystal structure of hematite forms during its synthesis and is determined by the nature of the precursor, the temperature of synthesis, the temperature gradient, and the rate of the removal of gaseous thermolysis products. The highest activity is displayed by the catalyst prepared on the basis of hematite with mosaic blocks 70–90 nm in size and a minimum SF concentration caused by half and quaternary dislocations. Such hematite was synthesized via the thermolysis of iron sulfate at 950 K under fluidized bed and low temperature gradient conditions. Hematite from iron carbonate is not recommended for use in synthesizing a catalyst due to the high concentration of low-temperature SFs, which result in the formation of catalytically low-active potassium β-polyferrite.