Catalysis in Industry最新文献

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.

The effect of an oxygen-containing compound on the cracking of an aromatic hydrocarbon is studied using the example of a model phenol–tetralin mixture. An analysis of the temperature dependences of the cracking rate constant of tetralin and tetralin in a mixture with phenol indicates that tetralin cracking is ihhibited during its co-conversion with an oxygen-containing compound due to the greater adsorption capacity of phenol on the catalyst’s surface. It is found that phenol in the model mixture changes the composition of liquid products, especially at low cracking temperatures. The effect of water on the conversion of a phenol-tetralin mixture is studied. It is established that water in the model feedstock reduces the inhibition of the cracking reaction of an aromatic hydrocarbon by an oxygen-containing compound. Based on the results of catalytic reactions, it is determined that when water is added, the level of the overall conversion of the mixture and the conversion of tetralin increase regardless of temperature. No appreciable qualitative differences between the distributions of cracking products in model mixtures with and without water have been revealed.

A summary of experience in the development of a microspherical aluminum–chromium catalyst isobutane dehydrogenation to isobutylene using the Yarsintez technology is presented. The development dynamics of KDI industrial catalysts based on a new boehmite support is considered. The relationships between elemental and phase compositions of catalysts and their operational characteristics are found. A boehmite support was obtained according to a new two-stage scheme, including the hydrothermal treatment of a thermal decomposition product of gibbsite agglomerates with a required size. This technology makes it possible to control the phase composition of a support and the physicomechanical properties of catalysts and their catalytic properties, which made it possible to obtain KDI, KDI-M, and KDI-M1 catalysts. The most important stages of their introduction into commercial operation at Nizhnekamskneftekhim are described. The KDI-M industrial catalyst provides a stable yield of isobutylene of 33–37% during the isobutane dehydrogenation and a yield of methylbutenes of 30% during the isopentane dehydrogenation. The catalyst consumption is 2−3 kg per ton of isobutylene produced. The ways are proposed for the improvement of a catalyst and the optimization of reactor equipment on the basis of monitoring the catalyst operation results. The KDI-M1 industrial catalyst modified with a silicon-containing inorganic complex is better than earlier products of this series in its activity and selectivity according to laboratory tests and is ready for production.