Vol 92, No 8 (2019)

Absorption using aqueous solutions of alkanolamines is the most widely used procedure for removal of carbon dioxide from natural gas, flue gases from power-generating facilities, and other mixtures. Its main drawback is degradation/deactivation of alkanolamine under the process conditions (high temperatures, presence of oxygen and other impurities) with the formation of heat-stable salts consisting of alkanolammonium cation and anions of organic and inorganic acids. The main operation problems caused by heat-stable salts are considered in the review. Three main methods for removal of heat-stable salts from alkanolamine adsorbents are described in detail: distillation, ion exchange, and electrodialysis. The main characteristics of these methods and their advantages and drawbacks are described, and a comparative analysis is made. The history and state-of-the art of studies within the framework of each method are presented.

Carbonylation of ethylene on cobalt catalysts in the presence of promoters was studied. It was shown that aromatic nitrogenous bases improve the stability of the catalytic system based on cobalt dioctacarbonyl and enable the carbonylation of ethylene in propanol-1 under substantially milder conditions, compared with the absence of a promoter. The carbonylation of ethylene in propanol-1 yields propyl propionate and diethyl ketone as products. Phenanthroline and 4-N, N-dimethylaminopyridine were found to be the most effective among the promoters studied. The modification of cobalt dioctacarbonyl with phenanthroline and 4-N, N-dimethylaminopyridine favors an increase in the reaction selectivity with respect to diethyl ketone and propyl propionate, respectively.

Zirconium oxide samples synthesized and modified with Al, Si, W oxides were studied as dehydrating components of bifunctional catalysts for synthesis of dimethyl ether. ZrO₂ modified with Al and Si oxides is inactive in the dehydration of methanol, but its dehydrating activity becomes comparable with the activity of γ-Al₂O₃ upon introduction of WO₃. According to the data on methanol adsorption at 46°C, the adsorption capacity of ZrO₂ modified with SiO₂ is comparable with the capacity of γ-Al₂O₃, and that of ZrO₂ modified with WO₃ is four times lower. The difference in the catalytic and adsorption behavior of the samples is accounted for by the data of in situ high-temperature diffuse reflection IR spectroscopy. A high content of weak Brønsted acid centers is observed on the ZrO₂ surface, with the interaction of these with methanol resulting in the methoxylation of the catalyst surface. When W oxide is deposited onto zirconium oxide, the surface has strong Brønsted centers involved in the reaction of methanol dehydration. A coprecipitation from solution of nitrate salts of Cu, Zn, La with Na carbonate, followed by the procedures of filtration, washing, and thermal treatment, yielded a catalyst for synthesis of methanol, the activity of which is close to that of the industrial catalyst.

Dissolution of metallic rhodium in solutions of hydrochloric acid was studied under hydrothermal autoclave conditions. The influence exerted by various factors on the depth of rhodium(0) transfer to solution was examined. It was found that the quantitative dissolution of rhodium(0) is reached in a mixture of hydrochloric and hydrobromic acids in the presence of manganese dioxide at 20°C in autoclaves. The results obtained can be used both for an analytical determination of rhodium and for processing of rhodium-containing raw materials and synthesis of complex rhodium compounds.

Possibility of using the ion-exchange method for purification of aqueous lithium-containing solutions to remove soluble chemical impurities was studied. As sorbents served strongly acidic (Tokem-140, Tokem-308/545, KU-2-8), weakly acidic (Tokem-200), mixed phosphorus-containing (Purolite S597), and chelate cation exchangers (Amberlite IRC-748, Purolite S930) of imported and domestic manufacture in the H⁺ and NH₄⁺ forms. The physical properties of the sorbents were examined. Values of the distribution coefficients of lithium and impurity ions and the static exchange capacity were calculated. It was shown that it is possible to perform group extraction of impurities: ions of alkaline-earth (Ca, Mg) and transition metals (Al, Fe, Cu, Ni, Zn, Ti, Cr, Mn) with a Purolite S597 cation exchanger in the H⁺ form and Cu and Fe admixtures by chelate sorbents (Amberlite IRC-748 and Purolite S930).

Properties of polytetrafluoroethylene films modified with mono- and two-component titanium-phosphorus oxide systems by alternating treatment of the polymeric substrate in a prescribed order with vapors of reagents from the series TiCl₄, PCl₃, and H₂O were examined. It was found that the energy characteristics of the sample surface with two-component oxide systems P–Ti and Ti–P in comparison with polytetrafluoroethylene modified with only phosphorus or titanium oxide functional groups due to the increase in the polar component of the surface energy. Specific features of the effect of stabilization of the electret charge in modified polytetrafluoroethylene films. It was shown that the best electret properties are possessed by titanium-containing polytetrafluoroethylene films, including those with two-component titanium-phosphorus oxide additives. According to the results of a differential-thermal analysis, modified samples exhibit an increased thermo-oxidative stability manifested in that the onset temperature of the polymer decomposition increases by 40–50° and the loss of mass decreases by 17–23% as compared with an unmodified sample at 650°C.

Specific features of flocculation of aqueous-salt (KCl, NaCl) clay dispersions with polyacrylamide and anionic acrylamide copolymers, including the influence exerted by the procedure of polymer dissolution in water or salt solution on the sedimentation rate and density of floccules and on the hydrodynamic properties of the polymers, are described. The use of aqueous-salt solutions of flocculants enhances the flocculating effect. The most effective flocculant for aqueous-salt clay dispersions is polyacrylamide prepared in a salt solution, which is due to higher flexibility of the polymer chain. The results obtained are of practical interest in connection with the possibility of enhancing the efficiency of the flocculation of aqueous-salt clay dispersions in dressing of potassium ores.

A new method was suggested for preparing aromatic polyphenylquinazolones by thermal polyhet-erocyclization of polyamidines containing free carboxy groups. The structure of the polyphenylquinazolones obtained was confirmed by elemental analysis and IR spectroscopy. The polymers obtained are soluble in a wide range of organic solvents and resistant to thermal and thermal oxidative degradation; they exhibit high deformation and strength characteristics. Such properties make these polymers promising for processing into various items by traditional methods.

Representatives of a new generation of norbornene aminomethoxy derivatives were prepared by Mannich condensation of norbornenylmethanol, formaldehyde, and secondary amines. The structures of the compounds were confirmed by elemental analysis, mass spectrometry, and IR and ¹H, ¹³C NMR spectroscopy. The compounds were tested as antimicrobial and antifungal agents. They show higher antimicrobial performance than the presently used agents do. The minimum inhibitory and minimum bactericidal concentrations were determined.