Home – Home – Jornals – Chemistry for Sustainable Development 2011 number 1

The method of self-propagating high temperature synthesis was used for preparing highly efficient catalysts from Ni-Al alloys corresponding to the basic composition of Ni₃Al intended for the process of carbon dioxide methane conversion. A low-dose modifying of platinum was carried out using ion implantation. Catalysts were tested in the course of carbon dioxide methane conversion at an atmospheric pressure and within the temperature range of 600-900 °С. It is demonstrated that the microstructure of the samples exerts a significant effect on the catalytic activity and stability of their functioning. A maximum activity is inherent in nanostructured catalysts those represent Pt clusters with size ranging from 0.3-0.5 to 3-5 nm, stabilized within the structure of intermetallic compound Ni₃Al and Al₂O₃. Using the methods of XRD, SEM, EDS, HRTEM, XPS, DSC-TG it was demonstrated that unmodified catalysts undergo a partial coking in the course of methane conversion into synthesis gas, whereas samples modified with platinum are stable and almost non-affected by deactivation due to carbonization.

A process of modifying the pore structure of mesoporous carbon carrier Sibunit obtained on the basis of technical carbon (soot) via introducing furfuryl alcohol into carbon at the stage of granulation was studied. An effect of modification conditions on the textural characteristics of the modified Sibunit was estimated. It was demonstrated that the introduction of furfuryl alcohol into technical carbon at the stage of granulation allows additional developing the Sibunit micropore volume up to 0.17-0.26 cm³/g. It was found that the percentage of micropores depends strongly on the degree of carbonization, i. e., on the amount of pyrocarbon deposited. When the carbonization level is higher than 60 %, the effect of the modification becomes negligible, which does not allow generating micropores in a great amount within the material. Basing on these results, a model was developed concerning the structure of modified Sibunit.

The procedure of the synthesis of aerogels Al₂O₃ and VO_x/MgO with the particle size of several nanometres was developed. The specific surface of materials obtained after drying under supercritical conditions exceeded 1000 m²/g. The possibility to govern the properties of aerogels through modification with acids and β-diketones of the solutions of alkoxides used as initial substances was revealed. The high activity of modified aerogel of Al₂O₃ in the processes of destructive sorption and catalytic dehydrohalogenation was demonstrated. It was shown that the aerogel VO_x/MgO exhibits high activity in the reaction of decomposition of Freon CF₂Cl₂.

By the example of the formation of Pt/Al₂O₃ catalytic system an influence was demonstrated exerted by the sequence of metal complex precursor transformations at the initial stages of catalyst preparation upon the state of platinum on the active surface of the finished catalyst. Views are expounded concerning the nature of the chemical bond between the metal complex and the carrier. Approaches are considered with respect to the quantitative differentiation of ion-exchange (outer-sphere), and coordinationally bonded (inner-sphere) adsorbed metal complex species, with respect to determining their chemical composition, as well as with respect to obtaining catalysts from a deposited precursor homogeneous in the type of interaction with the carrier.

Using the methods of Auger electron spectroscopy and the transmission electron microscopy, the process of aluminium activation by liquid metal alloy Ga-In was investigated. It was demonstrated that the components of the Ga-In alloy penetrate across the "biographical" aluminium oxide film to spread over the surface of aluminium metal. The activated aluminium interaction with tert-butyl chloride in liquid isobutene was investigated. It was revealed that the interaction takes place in three stages: the formation of aluminium chloride ionic complexes and aluminium chloride, the decomposition of tert-butyl chloride in situ obtained aluminium chloride systems, the formation of stable molecular aluminium chloride complexes with tert-butyl chloride, which complexes block the further interaction between chloroalkanes and activated aluminium. The aluminium chloride complexes obtained were studied for the case of isobutane alkylation by butenes.

A new approach is proposed to the preparation of highly active bifunctional catalysts for hydrogenation processes providing an increase in the conversion level of oil refining to produce motor fuels in accordance with contemporary international standards. This approach is based on the preparation of a carrier containing acidic components, as well as on targeted selective synthesizing an active component for the hydrogenolysis and hydrogenation reactions such as Co(Ni)-Mo(W)-S phase. The latter is localized in the structure of the catalyst so that it is available for all the raw material components liable to catalytic transformations. The method of preparation is based on an in-solution synthesis of bimetallic compounds, the precursors of the active component. Within the framework of the approach proposed, highly active catalysts can be prepared, designed for hydrocracking and hydrorefining of various petroleum distillates.

Basic principles are considered concerning the action of photocatalysts in deep oxidation of organic compounds containing in air. Within the framework of the Langmuir-Hinshelwood model, kinetic parameters were calculated concerning the photo-oxidation process for a number of substances (the rate constant and adsorption constants) were then used for designing reactors for air purification. It is demonstrated that for increasing the rate of photocatalytic oxidation it is necessary to optimize the geometry of a photocatalytic filter, as well as to use inorganic air-penetrable materials (glass fibre cloth and foamed ceramics) as carriers for a photocatalyst. In addition, the efficiency of air purification could be enhanced through the use of multi-stage reactor wherein air under purifying passes successively the stages of electrostatic filtration, adsorption and photocatalytic treatment. An example of the proposed concept of multi-stage air purification was demonstrates at the Luch Co. (Novosibirsk).

Urgent directions in mastering the methods of chemical processing of plant biomass and in the development of new methods of integrated utilization of its major components - polysaccharides, lignin, and extractive substances are considered for research work carried out at the Institute of Chemistry and Chemical Technology, SB RAS (Krasnoyarsk, Russia)) as example. Some processes are described that have been developed for utilization of wood waste material resulting in obtaining valuable chemical compounds (levulinic acid, glucose, xylose, aromatic aldehydes, biologically active compounds), important material (cellulose, biodegradable polymers, sorbents) and liquid fuel.

Results are presented concerning the studies on the formation of borate-containing aluminium oxide as a solid acidic catalyst system for the catalytic oligomerization of butenes. The possibilities of designing bi- and polyfunctional catalysts via modifying borate-containing aluminium oxide metals by metals and metal oxides from groups VI-VIII for the processes of oligomerizing ethylene, propylene, for single-stage production of ethylene, as well as for the processing of vegetable oil into diesel fuel components.

The basic aspects of environmental protection from hazardous gaseous impurities present in the exhaust gases of diesel engines are considered. Approaches used for the development of fundamental investigation of adsorbents and catalysts for afterburning СО and hydrocarbons are outlined. Results of the investigation of adsorption capacity of zeolites BEA and Y types with respect to heavy hydrocarbons (decane and toluene) obtained with the help of the gravimetric microanalyzer TEOM are presented. It is shown that both zeolites possess comparable capacities with respect to toluene, while the presence of mesopores in BEA zeolite determines its substantially larger adsorption capacity with respect to decane. For Pd/Al₂O₃ catalysts as example, the effect of the nature of precursor of active component and treatment conditions on the activity of the catalysts in the oxidation of CO is considered. It is demonstrated that in the case of the mass fraction of deposited chloride components up to 0.25-0.5 % atomically dispersed forms of palladium are formed; they are responsible for the high activity of palladium catalysts.

Prospective cyclic hydrocarbon combustion processes those differ by the type of chemisorbent are considered. In the carbonate cycle for СО₂ isolation from flue gases a high-temperature solid regenerable СО₂ chemisorbent is used. In the oxygen cycle, solid oxygen chemisorbent is used that is restored via contacting with fuel and oxidized when exposed to air. A common feature of such processes consists in solid-state reactions of binding and releasing the products or reactants at different stages of the process. Requirements for chemisorbents are determined concerning cyclic processes. Various factors affecting the efficiency of their use are considered, literature data concerning the efficiency of proposed СО₂ concentration cycles are presented.

Hemosorption (purifying the blood outside an organism) and enterosorption (detoxification of an organism through the gastrointestinal tract) are the most promising methods of the sorptional medicine. As far as the adsorption of toxic substances with different molecular mass and nature is concerned, carbon sorbents are of interest to meet the requirements of medicine. Sorbents of different nature and structure are described. Methods for controlling the adsorption activity of the sorbent are indicated. A particular attention is paid to the development of selective sorbents for using in sorptional medicine and proteomics.