N. V. Shikina

Supported honeycomb monolith catalysts for high-temperature ammonia decomposition and H2S removal

Abstract Catalysts that have potential in simultaneous removal of H 2 S and NH 3 decomposition were developed. The monolith supports of high surface area and acceptable mechanical strength based on titania and silica–alumina precursors were prepared and tested. Preparation routine and composition of Mn, Fe and Cu oxides supported honeycomb catalysts have been optimized. Impregnated and washcoated monolith catalysts were tested in ammonia high-temperature decomposition.

High-performance method for specific effect on nucleic acids in cells using TiO2~DNA nanocomposites

Nanoparticles are used to solve the current drug delivery problem. We present a high-performance method for efficient and selective action on nucleic acid target in cells using unique TiO2·PL-DNA nanocomposites (polylysine-containing DNA fragments noncovalently immobilized onto TiO2 nanoparticles capable of transferring DNA). These nanocomposites were used for inhibition of human influenza A (H3N2) virus replication in infected MDCK cells. They showed a low toxicity (TC50 ≈ 1800 μg/ml) and a high antiviral activity (>99.9% inhibition of the virus replication). The specificity factor (antisense effect) appeared to depend on the delivery system of DNA fragments. This factor for nanocomposites is ten-times higher than for DNA in the presence of lipofectamine. IC50 for nanocomposites was estimated to be 1.5 μg/ml (30 nM for DNA), so its selectivity index was calculated as ~1200. Thus, the proposed nanocomposites are prospective for therapeutic application.

Study of Catalysts for Catalytic Burners for Fuel Cell Power Plant Reformers

Catalytic burners for fuel cell power plant reformers are alternatives to conventional flame burners. Their application is expected to provide uniform temperatures in the reformer, efficient use of low-calorific gaseous by products and reduction of pollutant emissions. For testing in the burners, a series of spherical Pd/CeO2/Al2O3 catalysts were prepared. An optimum concentration of ceria providing the highest thermal stability of catalysts was determined. An effect of catalyst activation in the reaction mixture-1% methane in air was observed. A series of Mn containing oxide catalysts on spherical γ-Al2O3 or (γ+Χ)-Al2O3, both pure and doped with La, Ce and Mg oxides were prepared. The catalysts were characterized by chemical analysis, X-ray phase analysis, BET surface area and activity measurements in methane oxidation. A batch of Mn-Mg-La-Al-O catalyst was prepared for further long-term testing in a model reformer with a catalytic burner. A model reformer with a catalytic burner was designed and fabricated for testing in the composition of the bench-scale Fuel Cell Power Plant. Preliminary testing of this catalyst showed that it provided complete methane combustion at the specified operational temperatures over 900 °C.

Efficient inhibition of human influenza a virus by oligonucleotides electrostatically fixed on polylysine-containing TiO2 nanoparticles

Antiviral activity of the TiO2·PL·DNA nanobiocomposites was studied on the MDCK cell culture infected with influenza A virus (subtype H3N2). DNA fragments in the nanocomposites are electrostatically bound to titanium dioxide nanoparticles precovered with polylysine. It was shown that TiO2·PL·DNA(v3′) nanocomposite bearing the DNA(v3′) fragment targeted to the 3′-end of the noncoding region of segment 5 of viral RNA specifically inhibited the virus reproduction with the efficiency of 99.8% and 99.9% (i.e., by factors of ∼400 and 1000, respectively) at a low concentration of DNA(v3′) in nanocomposite (0.1 and 0.2 μM, respectively). The TiO2·PL·DNA(r) nanocomposite containing an oligonucleotide noncomplementary to viral RNA or oligonucleotide DNA(v3′) unbound to the nanoparticles show very low antiviral activity (inhibition by factors of ∼3.5 and 1.3, respectively).

Development and Testing of Granular Catalysts for Combustors of Regenerative Gas Turbine Plants

Two types of granular catalysts for effective methane combustion in combustors of gas turbine plants (GTPs) were developed: (1) catalysts based on noble metals with a low Pd content (1–2 wt %), characterized by a low methane ignition temperature, and (2) catalysts based on manganese oxides and hexaaluminates, which have an increased thermal stability. The methane oxidation kinetics was investigated, and combustion in the catalyst chamber of the GTP was simulated. For optimizing the combustion technology, the following two-step process using a combined catalytic package is suggested. The inlet zone of the combustor is filled with a highly active Pd catalyst, which initiates methane oxidation and ensures that the temperature at the exit of this zone is the initial temperature of methane combustion. This takes place in the next zone, which is filled with an oxide catalyst tolerant to high temperatures. The pilot testing of the catalysts was carried out in a model catalytic combustor. The results are in satisfactory agreement with calculated data. Long-term tests indicate the high stability of the catalysts. The Pd catalyst was demonstrated to retain its high activity and to provide an ignition temperature of 240°C. The initial activity of the hexaaluminate-based catalysts remains unchanged after tests at 930°C. The use of a combined charge of the palladium (7–15%) and manganese (85–93%) catalysts in the model GTP combustor allows a high natural gas combustion efficiency to be achieved at a low level of hazardous emissions (NOx, 0–1 ppm; CO, 1–3 ppm; hydrocarbons, 3–10 ppm).

Characterization of new catalysts based on uranium oxides

Catalysts based on uranium oxides were systematically studied for the first time. Catalysts containing various amounts of uranium oxides (5 and 15%) supported on alumina and mixed Ni-U/Al2O3 catalysts were synthesized. The uranium oxide catalysts were characterized using the thermal desorption of argon, the low-temperature adsorption of nitrogen, X-ray diffraction analysis, and temperature-programmed reduction with hydrogen and CO. The effects of composition, preparation conditions, and thermal treatment on physicochemical properties and catalytic activity in the reactions of methane and butane oxidation, the steam and carbon dioxide reforming of methane, and the partial oxidation of methane were studied. It was found that a catalyst containing 5% U on alumina calcined at 1000°C was most active in the reaction of high-temperature methane oxidation. For the Ni-U/Al2O3 catalysts containing various uranium amounts (from 0 to 30%), the introduction of uranium as a catalyst constituent considerably increased the catalytic activity in methane steam reforming and partial oxidation.

Design of TiO2~DNA nanocomposites for penetration into cells

Methods of noncovalent immobilization of DNA fragments on titanium dioxide nanoparticles (TiO2) were developed to design TiO2∼DNA nanocomposites, which were capable of penetrating through cell membranes. TiO2 nanoparticles of different forms (amorphous, anatase, brookite) with enhanced agglomeration stability were synthesized. The particles were characterized by X-ray diffraction, small-angle X-ray scattering, infrared spectroscopy and atomic force microscopy. Three approaches to the preparation of nanocomposites are described: 1) sorption of polylysine-containing oligonucleotides onto TiO2 nanoparticles, 2) the electrostatic binding of oligonucleotides to TiO2 nanoparticles bearing immobilized polylysine, and 3) sorption of oligonucleotides on TiO2 nanoparticles in the presence of cetyltrimethylammonium bromide (cetavlon). All three methods provide an efficient and stable immobilization of DNA fragments on nanoparticles that leads to nanocomposites with a capacity of up to 40 nmol/mg for an oligonucleotide. DNA fragments in nanocomposites were shown to retain their ability to form complementary complexes. It was demonstrated by confocal laser microscopy that the proposed nanocomposites penetrated into cells without transfection agents and other methods of exposure.

TiO 2 ~Deoxyribozyme Nanocomposites as Delivery System and Efficient Site-Specific Agents for Cleavage of RNA Targets

Synthetic DNA molecules of 10-23 deoxyribozymes (Dz) are known to be efficient and site-specific agents for the RNA cleavage in a catalytic manner. To provide the penetration of Dz into cells, we have proposed the new delivery system for deoxyribozymes in the form of TiO 2 •PL-Dz nanocomposite. These nanocomposites consist of catalytically ac- tive Dz molecules noncovalently immobilized through the polylysine linker to TiO 2 nanoparticles, which provide the penetration of Dz into cells. Deoxyribozymes in the prepared TiO 2 •PL-Dz nanocomposites were shown to retain their ability to cleave RNA targets albeit at a slower rate but with the same site-specificity and similar efficiency as free Dz. Unlike free Dz, the proposed TiO 2 •PL-Dz nanocomposites penetrate into cells without auxiliary actions.

Catalysts for processing light hydrocarbon raw stock: Combustion synthesis and characterization

Fiber glass supported nanosized Co and Co-Ni catalysts were prepared by solution-combustion synthesis and characterized for their structure and catalytic activity.

Development of Granular Catalysts and Natural Gas Combustion Technology for Small Gas Turbine Power Plants

Gas turbine power plants (GTPPs) of low power (tens of kW to 1.5-2 MW) are promising autonomous sources of energy and heat. The application of gas turbine technologies saves fuel, solves heat supply and water shortage problems. The nominal efficiency of GTTPs belonging to different generations varies from 24% to 38% (average weighted efficiency – 29%). This is 1.5 times higher than that of combined heat power plants. The main GTPP drawback is significant emission of toxic nitrogen oxides due to high temperature combustion of the gas fuel. The main approach used today to decrease the emission of nitrogen oxides from GTPPs is based on the use of the so-called homogeneous combustion chambers working with premixed lean fuel-air mixtures with two-fold excess of air. The decrease of NOx formation is principally the result of the low flame temperatures that are encountered under lean conditions (Correa 1992). This technology makes it possible to decrease significantly the temperature in the combustion zone relative to traditional GTPP combustion chambers with separate supply of fuel and air to the combustion zone. As a result, the concentration of nitrogen oxides in the flue gases decreases from 100 ppm to 1020 ppm. The downside of this approach is, however, that it results in low heat release rates, which, in turn, may negatively affect combustion stability. The most efficient way to decrease emissions of nitrogen oxides in GTPPs is to use catalytic combustion of fuel (Trimm, 1983; Pfefferle & Pfeferle., 1987; Ismagilov & Kerzhentsev 1990; Parmon et al., 1992; Ismagilov et al., 1995; Ismagilov & Kerzhentsev, 1999; Ismagilov et al., 2010). In the catalytic chamber, efficient combustion of homogeneous fuel-air mixture is achieved at larger excess of air and much lower temperatures in the zone of chemical reactions compared to modern homogeneous combustion chambers. In the last decade, the obvious advantages of the catalytic combustion chambers in GTPPs initiated intense scientific and applied studies in the USA (Catalytica) and Japan (Kawasaki Heavy Industries) which are aimed at development of such chambers for GTPPs for various applications (Dalla Betta et al., 1995; Dalla Betta & Tsurumi, 1995; Dalla Betta & RostrupNielsen, 1999; Dalla Betta & Velasco, 2002).