Vol 8, No 4 (2016)

A method for the nontemplate sol–gel synthesis of micro-mesoporous and mesoporous titanosilicates is developed using commercially available raw materials (a mixture of oligomer esters of orthosilicic acid (Ethylsilicate-40) and a water–alcohol solution of titanium(IV) ethoxide). The effect of the pH values of the reaction mixture on sol–gel synthesis is studied using the characteristics of the porous structure of titanosilicates. Samples of amorphous structure with different textural characteristics are obtained by varying the pH in the range of 3–10: specific surface area, 320–740 m²/g; micropore volume, 0.04–0.15 cm³/g; and mesopore volume, 0–0.92 cm³/g. It is shown that a sample of mesoporous titanosilicate obtained with alternating pH values has maximum catalytic activity in the oxidation reaction of 4-tert-butylphenol (TBP) in aqueous solutions of hydrogen peroxide. (Conversion of 4-tert-butylphenol, 45 wt %; selectivity of the formation of 4-tert-butylcatechol, 66 wt %. Conditions: 10 wt % of titanosilicate; TBP/H₂O₂ = 1/2; 75°C; 1 h).

A comparative study of copper-containing catalysts with different chemical and phase compositions is performed to determine conditions for the implementation of the vapor phase and highly selective dehydrogenation of methanol to methyl formate or syngas. A thermodynamic analysis of the reaction is also performed. It is shown that Cu⁰ nanoparticles formed in the course of reductive activation reveal different selectivities with respect to the formation of methyl formate from methanol or its dehydrogenation with formation of syngas. By correctly selecting the catalyst composition and process conditions, high (90–100%) selectivity with respect to either methyl formate or syngas can be attained. Catalysts based on Cu–Zn hydrosilicate of the zincsilite type and on CuAlZn aurichalcite are highly selective in the process of methyl formate formation. An estimation based on experimental data shows that the productivity of Cu/SiO₂ catalyst, the one most effective in dehydrogenation to syngas, is as high as 20 m³/h of syngas at a methanol vapor pressure of 1 atm, a temperature of 200°C, and a contact time of 0.5 s.

The possibilities of developing catalytic processes for the synthesis of 2-methylanthraquinone from 1,4-naphthaquinone (NQ) and isoprene, and synthesizing 2,3-dimethylanthraquinone from NQ and 2,3-dimethylbutadiene in the presence of aqueous solutions of high-vanadium heteropoly acid (HPA) as a bifunctional catalyst are examined. Two methods for catalyst regeneration are discussed: oxidation with oxygen at \({P_{o{}_2}}\) = 0.3–0.4 MPa and with concentrated nitric acid at atmosphere pressure. It is shown that regeneration with nitric acid ensures deeper oxidation of the reduced catalyst. Complete restoration of the properties of the catalyst following regeneration offers the possibility of its repeated use in the processes discussed in this work.

Existing industrial technologies for the production of motor fuel compounds by the heterogeneous oligomerization of light С₂–С₄ alkenes are considered, along with ones promising for the practical use. Such basic types of systems used as heterogeneous catalysts in these processes as solid phosphoric acid, amorphous alumosilicates, zeolites, ion-exchange resins, anion-modified metal oxides, and nickel-containing catalysts, are described. Special attention is given to the dimerization of iso-butylene with the formation of iso-octene and its subsequent hydrogenation to iso-octane.

The effects on the stability of catalysts for the oxidative chlorination of methane due to evaporation of the active component (copper chloride) of the catalyst are studied. The volatility of copper chloride is shown to depend mainly on the catalyst composition and temperature. At a moderate 350°C in the reactor, the evaporation of copper chlorides after 5 h is 0.45% on a catalyst containing copper and potassium chloride and 0.72% on a catalyst containing lanthanum chloride. The stability of catalyst operation can be effectively maintained not only by decreasing the volatility of copper chloride, but also by feeding hydrochloric acid with dissolved copper chloride isolated from the reaction gas of methane oxychlorination at the outlet of the reactor (for the removal of reaction heat and the recycling of unconverted hydrogen chloride) back into the reactor.

The propensity of carbon support for methanation in a hydrogen-containing medium is a problem for active ruthenium ammonia synthesis catalysts, since this leads to the degradation of the support and the sintering of the active component. This review analyses some key works on approaches to methanation inhibition and their results to show that, on the whole, an algorithm for solving the methanation problem has been found, i.e., the graphitization of carbon supports at high temperatures (up to 2000°C) and the introduction of ruthenium promoters, specifically alkali (Cs, K) and alkali-earth (Ba) oxides, whose role is to modify the electron state of ruthenium and block the surface of a carbon support to prevent it from interacting with active hydrogen. The most efficient catalyst not liable to methanation up to 700°C and a hydrogen pressure of 100 atm has been found. The resulting analysis can be useful in selecting and preparing Me/C catalysts in which Me represents metals of the VIII Group and others.

Experimental data obtained in studying processes that occur during the mechanoenzymatic hydrolysis of cell wall polymers of Saccharomyces cerevisiae yeast are presented. Special emphasis is placed on studying the reactivity of polymers contained in the supramolecular structure of cell walls, and on scaling the technology using pilot and industrial equipment. It is shown that mechanical treatment of yeast biomass allows us to alter the supramolecular structure of cell wall polymers and increase their reactivity in the enzymatic hydrolysis. Mechanical treatment disintegrates yeast cells and changes the supramolecular structure of polymers in their cell walls; the structural layers of a cell wall become disordered and diffused. A phenomenological model of mechanically activated enzymatic hydrolysis is proposed; the model is based on an autolocalization mechanism of the process. The domestic commercially available enzyme preparation CelloLux 2000 (OOO PA Sibbiopharm, Berdsk, Novosibirsk oblast) is used in this work. It is shown that changes in the supramolecular structure of yeast cell wall polymers occur during mechanically activated enzymatic hydrolysis. The yields of mannanoligosaccharides (1.1%) and mannanoproteins (2.7%) in the main extract are determined. Using pilot and industrial equipment at OOO PA Sibbiopharm, the technology is scaled and the production of a new mannanoligosaccharide product for animal husbandry is established. The pilot batch of the final product is effective against salmonellosis and is shown to increase the weight gain of experimental animals.