Catalysis in Industry最新文献

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.

A comparative analysis is performed for the properties of two Fenton-type catalysts in the oxidation of sulfur-containing compounds with hydrogen peroxide and the desulfurization of crude oil. The catalysts are based on Cu(I) and Fe(III), and Mo(VI) and W(VI) polyoxometalates. Heterogeneous samples are imidazolium salts chemically immobilized on surfaces of silochrome and contain the iron and copper chloride complexes or phosphomolybdic and phosphotungstic acid anions. Thiophene (T), dibenzothiophene (DBT), methylphenyl sulfide (MPS), and a diesel fraction with an initial amount of sulfur of 1080 ppm are used as model substrates. It is found that the order of reactivity of thiophene substrates depends on the nature of metal-containing anions: thiophene > DBT on the Cu and Fe catalysts and DBT > thiophene on the polyoxometalate catalysts. This effect is explained using literature data. The catalyst based on phosphotungstic acid allows desulfurization of the diesel fraction of oil to amounts of sulfur of < 10 ppm, which meets today’s environmental standards.

Bifunctional catalysts based on NiMo(W) sulfides and ZSM-23-Al₂O₃ composite supports were synthesized, and their properties in the conversion of diesel fractions with different contents of nitrogen (<1; 10 and 20 ppm) were studied. The possibility of using the synthesized catalysts to obtain hydrogenates with a cold filter plugging point of ≤ −38°C that meets the requirements of GOST R 55475-2013 in terms of the content of the gasoline fraction, aromatic compounds, and the derived cetane number is shown. The properties of the developed catalysts based on NiMo and NiW sulfides and the characteristics of hydrogenates obtained are compared. In addition, the properties of the developed samples are compared to those of a commercial imported isodewaxing platinum based catalyst. The developed catalysts were found to be less selective than the reference sample, but have better resistance to N-containing compounds in the feedstock.

Systems for the production, storage, and accumulation of hydrogen are an important line in the development of fundamental and applied aspects of alternative energy. Liquid organic hydrogen carriers (LOHCs), polycyclic forms of the corresponding aromatic compounds, are an effective way of hydrogen storage and release with contents of up to 7.3% by mass. The authors compare LOHCs as potential substrates for hydrogen storage and release systems based on catalytic hydrogenation and dehydrogenation reactions, inclusively, with cyclohexane, methylcyclohexane, decalin, perhydroterphenyl, bicyclohexyl, perhydrodibenzyltoluene, and perhydroethylcarbazole. Some data on the activity and selectivity of Pt-containing dehydrogenation catalysts are presented for each of the perhydrogenated substrates.

An investigation was carried out to study the feasibility of using synthesized acid-bearing carbonaceous catalyst (SO₃H–C and PO₄H₂–C) derived from cassava peel for biodiesel production from waste cooking oil (WCO). The catalyst activity was tested using an autoclave type reactor and three different oil to alcohol ratios (1 : 3, 1 : 5 and 1 : 7) at four different temperatures (50–80°C) for 4 h. Two types of alcohol (i.e. methanol (CH₃OH) and ethanol (C₂H₅OH) were used to understand the efficiency of using alcohol in the process. The study indicates that reaction using high ratio of alcohol (1 : 7) generally produced high yield of the biodiesel compared to other ratios. The yield of the biodiesel also increased with increasing temperature over all the reaction systems. The carbon modified with sulphuric acid catalyst showed the highest yield of ~ 90%, which was obtained at 80°C using a 1 : 7 ratio of WCO : alcohol. It was also observed that reaction with methanol produced better yields compared to ethanol reactions where significant differences were observed across both temperature and ratio. The catalysts were characterized using Fourier transform infrared spectroscopy, X-ray powder diffraction, surface area and pore volume analyses. The catalyst is of interest because it is green, non-toxic and synthesized using cassava peel waste.

The trend of modelling native enzymes is increasing day by day with the motive of mechanistic elucidation of enzyme-catalyzed reactions and the efficiency of catalysts. Most of the metalloenzymes are capable to activate molecular oxygen due to the presence of metal ions. Among these, copper-based metalloenzyme catechol oxidase has an attractive feature of its oxidizing ability to generate ortho-quinones from catechol. Moreover, the conversion of catechol to ortho-quinones is an important tool for the determination of hormonally active catecholamines such as adrenaline, noradrenaline, and dopa. Nevertheless, the use of native enzymes is highly expensive and the employment of biomimetic models can be the best alternative. This review summarizes some of the widely used modelling methods and their successful applications. Additionally, we also briefly elucidated the structure–activity relationship, kinetic studies of the catalytic oxidation of the substrate, and different external factors influencing the catalytic cycle such as pH, temperature, etc.

A review of modern approaches to the development of cobalt catalyst technology used in most known ways of synthesizing hydrocarbons from CO and H₂ using the Fischer–Tropsch is presented. The development of efficient catalysts solves the problem of replacing fossil fuels with ultra-clean alternative fuels and reduces their negative impact on the environment. An analysis of results from scientific and technological research, including ones obtained recently by the authors, shows current lines in developing the technology of high-performance catalysts for the Fischer–Tropsch synthesis of hydrocarbons using classical and integrated GTL technology, including the creation of new types of polyfunctional systems. The review mainly describes the catalytic characteristics of supported cobalt catalysts synthesized via impregnation and polyfunctional hybrid catalysts obtained on their basis for the selective synthesis of fuel fraction hydrocarbons. Problems of controlling selectivity, productivity, and changes in the activity and physicochemical properties of catalysts during long-term operation are considered.

One of a widely used broad-spectrum industrial bactericidal and mildew prevention agents is 1,2-benzoisothiazolin-3-one (BIT). In present study, it was demonstrated that aerobic oxidative cyclization of 2‑mercaptobenzamide (MBA) and 2,2'-disulfanediyldibenzamide (DSBA) in the presence of Mn(OAc)₂ as catalyst allowed to obtain BIT. The mechanism reaction was suggested. It was found that DSBA and MBA can be converted to the BITwith 99% yield at 1.0 mol % Mn(OAc)₂ under 0.3 MPa of oxygen and 100°C for 8 h. Experimental data point that this protocol is both economical and environmentally friendly.