No 3 (2023)

The use of technologies based on combustion of carbon-containing fossil fuel leads to emission of large amounts of CO2, one of the main greenhouse gases, into the atmosphere. To reduce the CO2 level in the atmosphere, systems for CO2 sorption from various gas sources are being developed. The systems allowing the CO2 sorption and desorption at low temperatures (25–200°С) are of most interest. Most frequently, such systems are composite materials consisting of a porous support and a CO2 chemisorbent dispersed on it. Low-volatile amine-containing compounds are the most promising among organic chemisorbents. Classification of the amine-containing sorbents with respect to the preparation procedure is discussed. The procedures include impregnation, covalent grafting, and in situ polymerization on the support surface. The impregnation procedure is simple and cheap in implementation. The sorption characteristics of materials prepared by impregnation depend on the efficiency of the dispersion of the active component, which is determined by the characteristics of the support pore structure, in particular, by the ability of the pore surface for chemical or electrostatic interaction with the supported amine-containing compound. The covalent grafting is based on immobilization of alkoxyaminosilanes on the surface of porous silica materials. The supports for implementing this approach should contain a large amount of silanol groups on the surface and should have the pore size sufficient for the efficient transport of CO2 molecules to amino groups. The main drawback of the grafting method is low thickness of the amine-containing component layers obtained. In situ polymerization is used for preparing materials with high content of grafted functional groups. Provided that the blocking of support pores is excluded in the course of in situ polymerization, materials of this type exhibit the highest sorption capacity for CO2.

Powder lignocellulose modifiers for vulcanized rubbers were prepared from secondary paper resources (recycled cardboard) treated with TiCl4 in hexane. The diffraction patterns, IR spectra, and morphological characteristics of the materials obtained, including the geometric characteristics and length distribution of fibers, were analyzed. The content of titanium, lignin, and carbonyl and carboxyl groups and the bulk density of the material were determined. The presence of up to 5 wt parts of powder modifiers per 100 wt parts of rubber in the rubber stock favors preservation of physicomechanical properties of vulcanized rubbers both before and after accelerated thermal oxidative aging at 100°C for 72 h, enhancing the resin–metal cord adhesion and thus prolonging the operation life of the vulcanized rubbers.

Calcium aluminate phases were synthesized in the range 950–1450°C from available raw materials: carbonate rock and metallurgical alumina, predominantly in the γ form with different grain sizes. The calculations of the amount of raw materials were based on the requirement to ensure the chemical composition of the product: Al2O3 71–72 and CaO 27–28 wt %. The designed phase composition of the samples is 65 wt % CaAl2O4 and 35 wt % CaAl4O7. When alumina with a grain size of 90 μm and a spherulitic microstructure is introduced into the reaction, the formation of the CaAl2O4 and CaAl4O7 phases mainly occurs in the range of 1250–1350°C, and phase equilibrium is established at 1450°C. Reducing the size of γ-alumina grains to 10 μm and destroying their spherulitic microstructure shifts the formation of calcium aluminates to the temperature range below 1250°C, and also significantly increases the rate of synthesis of target products.

SiO2 nanoparticles were modified with polyethylene glycol with a molecular weight of 2000, 6000, and 10000 g mol–1. For modification, the method based on the sequential interaction of polyethylene glycol with 3-(triethoxysilyl)propyl isocyanate with further treatment of the reaction product with nanodispersed SiO2 was used. The resulting product was characterized by IR spectroscopy, thermal analysis, and scanning electron microscopy. Modified nanodispersed SiO2 was introduced into epoxy resin in order to obtain coatings characterized by increased hydrophilicity. To improve the physical and mechanical characteristics, fillers were introduced into the composition of the coating with 30 wt % modified SiO2 nanoparticles: mica-muscovite and TiO2. It was shown that the process of biological fouling of epoxy coatings in the South China Sea proceeds more slowly in the case of a composition containing SiO2 nanoparticles modified with polyethylene glycol 6000.

Benzene proved to be a more effective eluent compared to chlorinated organic solvents traditionally used for chromatographic recovery of vanadyl petroporphyrins from the dimethylformamide (DMF) extract of asphaltenes on a column packed with mesoporous silica gel. Low eluting power of benzene can be compensated by moistening of the silica gel adsorbent. An increase in the silica gel moisture content from 0 to 7.7% does not lead to a decrease in the efficiency of the separation of vanadyl porphyrins from nonporphyrin components but leads to a tenfold decrease in the eluent consumption. A decrease in the eluent flow rate from 0.8 to 0.12 mL min–1 (per gram of the adsorbent) leads to a 1.5-fold increase in the yield of vanadyl porphyrins of required purity. An increase in the adsorbate : adsorbent weight ratio from 1 : 833 to 1 : 83 does not lead to a decrease in the efficiency of the vanadyl porphyrin recovery. Elution with benzene under optimum conditions (adsorbent moisture content, eluent flow rate, adsorbate : adsorbent ratio) allows the recovery of 3 times larger amount of petroleum vanadyl porphyrins from the DMF extract of asphaltenes than when using chloroform and dried silica gel under equal other conditions.