卷 9, 编号 4 (2017)

Thermostable oxide catalysts (Al₂O₃, ZrO₂, MgO, and CaO) deposited onto a resistive support (carborundum) are investigated for oxygen-free methane pyrolysis. Adding MgO, ZrO₂, and Al₂O₃ to pure carborundum considerably improves methane conversion and selectivity toward acetylene. In contrast, the deposition of СаO reduces the total activity of deposited catalysts. The maximum selectivity toward acetylene (23.6%) is achieved on MgO/SiC catalyst with methane conversion of 68% at T = 1290°C. Examination of the MgO/SiC sample shows that the catalyst retains its catalytic characteristics without decomposition (methane conversion, ≈69%; selectivity toward acetylene, ≈22%) for more than 4 h of operating in methane pyrolysis (15% СН₄ in nitrogen) at a temperature of 1300°С as a result of there being no carbon corrosion of the carborundum resistive support, in comparison to the metal catalysts.

The literature data on the direct catalytic conversion of methane into useful chemical products (Н₂, С₂₊ hydrocarbons, methanol, formaldehyde, and higher oxygenates) were analyzed. Processes based on these reactions have not yet been commercialized. For each reaction, the catalytic systems were revealed on which the characteristics (primarily, the yield of the desired product) are maximum, and the degree of their approximation to the level at which commercialization is possible was determined. Currently, the most suitable processes for pilot and industrial production may be the syntheses of С₂₊ and alkylaromatic hydrocarbons by oxidative condensation (dimerization) of methane and by the reaction of methane with С₃–С₆ alkanes, respectively. The problem of fast deactivation of catalysts in the synthesis of hydrocarbons of the gasoline fraction by methylation of olefins can be solved due to significant progress in the development of new modifications of zeolites and aluminosilicates. The main limitations on the implementation of methane pyrolysis into carbon and H₂ are the insufficient demand for the types of carbon materials produced and low strength characteristics of the available catalysts in the case of the process performed in the moving bed. For some products (methanol, formaldehyde), the yields are too low for commercialization, while for others (higher oxygenates) only the possibility of their production was shown.

A brief analysis is performed for the current state of processes for the production of motor fuels based on the consecutive oligomerization and hydrogenation reactions of unsaturated hydrocarbons. Some new butene hydrooligomerization catalysts based on the bifunctional NiO/В₂O₃–Al₂O₃, PdO/В₂O₃–Al₂O₃, and MoO₃/В₂O₃–Al₂O₃ systems are considered. It is shown that the best process performance parameters (a 67 wt % yield of liquid С₅₊ products at a butene conversion of more than 90%) are achieved with PdO/В₂O₃–Al₂O₃ catalyst prereduced in a hydrogen medium. The possibility of acetylene hydrooligomerization on NiO/B₂O₃–Al₂O₃ catalyst is demonstrated in principle. It is established that the presence of nickel(II) cations chemically bonded to the surface of a support is of fundamental importance for both acetylene hydrooligomerization and ethylene oligomerization.

Hydroisomerization catalysts based on nanosized molybdenum carbides are developed. Such catalysts are resistant to sulfur compounds and can be used for the synthesis of waxy diesel fuels with the same characteristics as on platinum-containing catalysts. In the first part of this work, acidic supports with different types of porous structure and concentrations and strengths of Brønsted acidic sites (e.g., silicoaluminophosphate SAPO-31, zeolite ZSM-12, modified zeolite Beta, and desiliconized zeolite ZSM-5) are synthesized for a new type of catalysts. Their physicochemical properties are studied by means of adsorption, temperature- programmed desorption of ammonia (TPD-NH₃), nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM).

The possibility of biodegrading dehydroabietic acid (С₂₀Н₂₈О₂, САS: 1740-19-8, abieta-8,11,13- trien-18-oic acid) (DAA), a toxic tricyclic diterpenoid, accumulated in the waste waters of the pulp and paper industry is studied using actinobacterial strain Dietzia maris IEGM 55^Т. Cells of the strain Dietzia maris IEGM 55^Т are shown to be resistant to DAA (MIC, 390 mg/L). The strain is not able to use DAA as its sole source of carbon and energy. DAA (500 mg/L) decays almost completely in 7 days when the bacteria are preliminarily grown with n-hexadecane. The DAA effect on the viability and respiratory activity of the bacteria is studied. Analysis of the antimicrobial activity shows that extracts of the obtained metabolites are not toxic, in contrast to the initial substrate. The resulting data expands our views on the catalytic activity of actinobacteria and their impact in decontaminating natural ecosystems that contain ecotoxicants.

Results are presented from studies and a comparative analysis of highly concentrated populations of free and immobilized Aureobasidium pullulans Y-4137 cells in the biocatalytic processes of pullulan production in glucose-containing media. The possibility of effectively using the developed biocatalyst in the form of immobilized cells is demonstrated. The process characteristics are determined for pullulan production from hydrolysates of various sources of renewable feedstocks (Jerusalem artichoke tubers, aspen wood, Chlorella vulgaris microalgal biomass, and potato pulp) under the action of the catalyst. It is established that A. pullulans cells immobilized in a polyvinyl alcohol (PVA) cryogel consume glucose 1.5 times faster and accumulate a 1.7 times higher concentration of the target polysaccharide in the medium than free cells. The immobilized cells can function for at least 15 operating cycles with a slight (no more than 10%) reduction in their metabolic activity. Analysis of the obtained data confirms that cell immobilization in a PVA gel for the production of pullulan allows us to shorten the duration of operating cycles in similar processes by a factor of 1.4 while reaching a comparable yield of the target product.