Home – Home – Jornals – Chemistry for Sustainable Development 2017 number 1

Catalytic heater model in the form of a tubular reactor, in the tube space of which heat is removed using a high-boiling coolant was elaborated. Kinetic parameters of methane oxidation rate constant on a manganese-alumina catalyst (pre-exponential factor and activation energy) that were used to calculate the observable reaction rates on grains of various shapes and sizes were determined. It was demonstrated that the maximum specific heat power of a catalytic heater is 19.25 kW/m³; it can be obtained by applying the catalyst in the form of rings with dimensions of 5 × 5 × 2 mm, under the following conditions: inlet methane concentration of 3 %, inlet temperature of 500 °C, coolant temperature of 400 °C, tube length of 1 m, tube diameter of 8 cm, linear rate of 0.05 m/s. With such parameters, the degree of methane conversion is greater than 98 %, and the maximum temperature does not exceed 770 °C, which meets accepted limitations.

The effect of the reduction period in hydrogen of Pd/Sibunit and Pd-M/Sibunit (M: Ga, Zn, Ag) catalyst, as well as the nature of palladium and zinc precursors on properties of samples in the of liquid-phase hydrogenation reaction of acetylene into ethylene was investigated. It was found that the introduction of the second metal (Ga, Zn, and Ag) into the Pd-catalyst prevented sintering of the active component during reductive thermal treatment resulting in the reduction period does not affect the activity and selectivity of the modified catalysts, unlike an unmodified Pd/Sibunit sample. For the Pd-Zn/Sibunit sample, it was demonstrated that modification with zinc led to a change in the nature of catalytic active sites and an increase in their number, regardless the nature of metal precursors; herewith, the Pd-Zn/Sibunit system synthesized from solutions of palladium nitrate and zinc nitrate is distinguished by a higher activity and selectivity.

A 0.25 % Pt/γ-Al₂O₃ catalyst was investigated. The sample was tested in modelling of joint conversion of butane and hexane, propane, and heptane with assessing kinetic parameters of the reactions under study. It was found that a decrease in the activation energy by 10.6 kJ/mol and an increase in the rate constant of aromatization by 1.3 times in comparison with hexane conversion was observed at joint conversion of butane and hexane, which leads to an increase in the yield of aromatic hydrocarbons. At the introduction of propane into the reaction medium to heptane, a reverse dependence was detected.

The present work is devoted to comparative analysis of the activity and stability of low-percentage palladium catalysts under conditions of three-route catalysis (CO and hydrocarbons oxidation, and nitrogen oxides reduction). Gamma alumina and delta alumina were used as carriers. Catalysts containing 0.12 % Pd and δ-Al₂O₃ on γ-Al₂O₃ and δ-Al₂O₃ were prepared by the wetness impregnation method. The resulting samples were studied by a set of physicochemical method. The forced thermal ageing method was used to assess the stability of catalysts to deactivation processes of the active component of Pd. Ethane hydrogenolysis allowed assessing the dispersion degree of the active component. The highly sensitive methods of electron spin resonance (ESR) and electron spectroscopy of diffuse reflectance (ESDR) were used to study the state of deposited palladium. Testing of the catalytic activity of samples under conditions of three-route catalysis was carried out. As a result, it was demonstrated that phase conversions of an alumina carrier did not exert significant effects on the thermal stability of samples during catalytic reactions.

An alternative method of joint disposal of acid tars (high-sulphur petrochemical waste) with wood-chemical industry and agriculture wastes, at which additional neutralization or trapping of sulphur acid decomposition products is not required, was investigated. At thermal treatment of a mixture of acid tar (a mixture of sulphuric acid and heavy oil fractions), template (high-ash biomass) and binder (furfurol, formaldehyde or resorcinol), sulphated carbon materials applicable as catalysts for a broad range of acid-catalyzed processes were obtained. The impact of synthetic methods for materials on acid and textural characteristics of materials was explored using BET, TGA, XPA, XPS methods and IR spectroscopy. Optimal conditions for the preparation of carbon materials with developed specific surface (up to 168 m²/g) and a high concentration of sulpho groups (up to 4.55 mass % SO₃H) were found. The addition of a template allows increasing calcination temperature (from 225 to 275 ^oC) that is required to achieve high specific surfaces, without a decrease in acidities (sulpho groups concentration) final samples. Testing of catalytic properties of the carbon materials obtained in modelling of a catalytic process for esterification of enanthic acid with methanol was performed.

The composition of sulphur compounds of oils in high-sulphur natural bitumen of the Ashalchi deposit (Russia), as well as its thermal cracking products was studied under various conditions. It was demonstrated that depending on thermal treatment conditions gas and coke formation, the composition of the liquid cracking products and sulphur content in them significantly changed. Cracking of bitumen in a reactor autoclave leads to an insignificant decrease in the content of benzothiophene homologs in the composition of oils, the products are enriched with of dibenzothiophene derivatives. Cracking of bitumen in a flow reactor allows decreasing the content of benzothiophene homologs by 37 %, and dibenzothiophene homologs - by 72 rel. % in liquid cracking products.

Analysis of the evolution of carbon black grades manufactured in Russia was given on the example of the Russia largest enterprise that is Omsk Carbon Group. Development trends innovative technologies of the enterprise in expanding varieties of carbon black grades were demonstrated. Innovative products including those manufactured under the brand OMCARB for various designations were presented in detail. Some results of scientific research carried out by the Scientific and Technological Center of Carbon Materials and Institute of Hydrocarbon Processing (IHP SB RAS) in the development trends of carbon black types were presented. Recommendations on rational choice and use of innovative varieties of black carbon were proposed in the first place to tire and industrial rubber goods, as well to as other polymer products manufacturers.

To improve biospecific properties of carbon enterosorbents for purposes of veterinary medicine methods of chemical modification of their surface were proposed. The first area is modification of carbon surfaces by the method of polycondensation of biologically active substances (arginine) and in situ formation of polymers (directly on the surface of carbon sorbents). Another method is impregnating into a porous matrix of carbon carrier nanodispersed betuline in a water soluble form. To study physicochemical characteristics of veterinary preparations synthesized the following methods were used: scanning electron microscopy (SEM) (relief and morphology); X-Ray phase analysis (phase composition); the method of low-temperature nitrogen adsorption-desorption (texture studies); X-Ray microanalysis and CHNOS Elemental Analysis (elemental composition): IR spectroscopic analysis, Kjeldahl method, H. P. Boehm's method and X-ray photoelectron spectroscopy (XPS) (surface functional composition of the synthesized samples). The article presents the study results of physicochemical properties of carbon sorbents before and after modification, which confirm the presence of polyarginine and betuline in the composition of the resulting samples.

To improve biospecific properties of carbon enterosorbents for veterinary purposes methods for chemical modification of their surface were proposed. Modified samples of carbon sorbent were synthesized: carbon sorbent containing polyarginine and the betuline preparation impregnated into a porous matrix. Adsorption properties of the tested samples in relation to substances modelling low and average molecular mass toxins (Vitamin В12, methylene blue) were studied. The assessment of adsorption properties in relation to proinflammatory cytokines at the example of a sorbent modified with polyarginine was carried out. It was found that adsorption properties of carbon sorbents were influenced by localized application of modifiers to carbon sorbent samples and elevated contents of oxygen- and nitrogen-containing groups on their surface.

Positive and negative effects of non–additivity of oxygen absorption rates at oxidation of Na₂S in the presence (Ni^II + Co^II)–containing catalysts were detected. It was determined that these effects were associated with peculiarities of the formation of nickel and cobalt sulphides particles. Positive effects of non–additivity were observed in the beginning of the reaction at the stage of forming metals sulphides embryos and referred to synergistic phenomena. Negative effects were detected at the growth stage of the sulphide phase particles. They are of nonsynergistic nature and associated with deposition of nickel sulphides on the surface of cobalt sulphide particles.

The effect of the catalytic addition of mesoporous aluminosilicate on the composition of the cracking products of natural bitumen on the Ashalchi deposit with a content of IBP-200 °C fractions of 4.6 mass % in the autoclave reactor was studied. It was demonstrated that the addition of 5 % catalyst increased destruction of resins and the yield of low-boiling fractions. It was determined that the catalyst modification with nanoscale nickel powder slowed down coke formation. At cracking of bitumen employing mesoporous aluminosilicate modified with nickel, the yield of IBP-360 °C fractions per 35.2 mass % was increased, and destruction of resins and asphaltenes was 48 % in comparison with the initial bitumen.

Homogeneous nitrogen doped (N-CNTs) bamboo-like carbon nanotubes with the carbon content up to 7.3 at % were obtained by catalytic decomposition of ordinary ethylene/ammonia mixture. Physicochemical properties of N-CNTs were studied by X-ray analysis, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy methods. The effect of the synthesis temperature, catalyst nature and reaction mixture composition per the amount of nitrogen, ratio of its forms, defectiveness and morphology of N-CNTs was determined.

The study of concentration hysteresis in methane oxidation over alumoplatinum catalysts was conducted. It was determined that catalysts activation was accompanied by partial platinum reduction, the boundaries of existence of concentration hysteresis and effect on them of the particle size of the active component were defined.

The effect of reduction temperature of a Pt/WO₃/ZrO₂ catalyst (200–500 °С) on indicators of n-heptane isomerisation was studied. It was found that the maximum yield of the desired reaction products that are high-octane di- and trimethyl-substituted (DTMS) n-heptane isomers was reached (27–31 mass %) in the region of the 250–300 °С. A rise in reduction temperature of the catalyst to 400–500 °С leads to an increase in the number of Lewis acid sites in 1.6–1.7 due to partial reduction of tungsten on the WO₃/ZrO₂ surface, which contributes to an increase in the catalyst activity; herewith, selectivity by the target products decreases due to enhancing side reactions of n-heptane cracking.

The study results of acidity in a series of borate-containing aluminium oxide with the B₂O₃ content from 2.0 to 31.4 mass % (butenes oligomerisation catalyst) and a nickel-containing ethane oligomerisation catalyst obtained on its base were presented using the ESR spin probe method. The correlations between catalytic properties and the amount of nickel adsorbed with the concentration of Brønsted acid sites (BAS) determined using the probe molecules perylene were found: an increase in the concentration of BAS determinable with perylene in systems leads to a rise in the butenes conversion degree, the yield of oligomerisation products, and also to an increase in the amount of nickel adsorbed.