Anatoli Lisovskii

Adsorption of sulfur dioxide by active carbon treated by nitric acid: I. Effect of the treatment on adsorption of SO2 and extractability of the acid formed

Abstract The process of adsorptive-catalytic cleaning of gas from sulfur dioxide using active carbon, treated by concentrated nitric acid, was studied. After oxidative treatment the acidity of the carbon increases and the basicity decreases. This results in an increase of the SO 2 adsorption and its oxidation to SO 3 , and in weaker retention of the sulfuric acid formed. This facilitates the removal of H 2 SO 4 by washing of the carbon and allows to obtain a more concentrated acid. The efficiency of the treated carbon is also higher in the process of SO 2 removal from a gas similar in composition to stack gases.

Carbonaceous deposits as catalysts for oxydehydrogenation of alkylbenzenes

Abstract The main industrial methods for the production of styrene and α-methylstyrene are the dehydrogenation of ethylbenzene and isopropylbenzene using mixed oxide catalysts: These reactions are endothermic and reversible, they take place at high temperatures (853–923 K), and their reversibility thermodynamically limits the yields of the products. Displacement of the equilibrium toward the formation of the vinylbenzenes is generally achieved by lowering the partial pressure of the reacting alkylbenzenes by diluting them in steam, heated to 973 K.

Adsorption of sulfur dioxide by active carbon treated by nitric acid: II. Effect of preheating on the adsorption properties

Abstract The adsorption and desorption of sulfur dioxide by active carbon, treated by nitric acid and followed by heating at 200–1000 °C, were studied. The HNO 3 treated carbon has a higher adsorption capacity for sulfur dioxide, than the untreated carbon, in spite of its lesser basicity. This may be the result of interaction of the SO 2 with the oxygenated surface groups of acidic character. Water promotes the adsorption of SO 2 . Heating results in a decrease of the carbon acidity because of decomposition of the surface oxygenated structures. It also leads to an increase of basicity resulting from the formation of basic sites. These changes of the carbon acid-base properties are particularly pronounced for the HNO 3 treated carbon due to higher concentration of the surface oxygenated groups. The increased basicity promotes adsorption of SO 2 and inhibits desorption by an acid-base mechanism different from the mechanism of adsorption on the carbon, which has not been preheated.

Polymerization of propylene by mixed Ziegler–Natta and metallocene catalysts

The polymerization of propylene using a mixture of racemic metallocenes and Ziegler–Natta catalysts was investigated. The polypropylene was obtained as a mixture of a fine powder and beads, with the powder being absorbed partially on the beads. The relative amount of the powder can be controlled by the concentration of the metallocene. The compatibility between the components of the mixed catalytic systems and the effect of the components on the rate of polymerization and on the properties of the new polymers were studied. The metallocene system dramatically affects the melt viscosity, isotacticity and molecular weight of the polymers. The two catalytic systems are able to act jointly, producing different polymers, for which separate melting and crystallization temperatures are obtained.

Polymerization of propylene by metallocene and Ziegler–Natta mixed catalytic systems. Study of polypropylene properties

Propylene was polymerized with metallocene and Ziegler-Natta mixed-catalytic systems to obtain reactor blends of metallocene and Ziegler-Natta-derived propylene homopolymers. The two catalytic systems are able to act jointly, providing individual polymers with different melting and crystallization temperatures. Compatibility between the components of the mixed-catalytic systems and the influence of the components on the polymerization process and on the properties of the reactor blends were studied. Thermal, mechanical, viscoelastic, rheological, and optical properties of the blends were tested and compared with those of conventional polypropylene grades.

Stereoerrors Formation in the Polymerization of Deuterated Propylene

Abstract The influence of the number of ancillary ligations and the corresponding structural features of three titanium benzamidinate complexes 1-3, in the polymerization of propylene, has been investigated. These complexes produce similar polymers indicating the formation of similar active species. The activation process was followed via 29Si-NMR spectroscopy.