A. V. Smirnov

Zeolite membranes: Synthesis, properties, and application

The review represents a brief analysis of the known methods for the preparation of zeolite membranes with a continuous selective layer and zeolite crystals embedded in their matrix. The principles of separation on zeolite membranes and the fields of application of these materials are discussed. Some examples of the separation of substances and membrane catalysis on zeolite membranes are given to confirm their high efficiency. Along with the discussion of published data, the authors present their own results.

Selective benzene isopropylation over Fe-containing zeolite beta

Ferrisilicate analogs of zeolite beta have been investigated as catalysts for benzene isopropylation. Activity, selectivity, reaction kinetics and catalyst deactivation have been examined. Results have been compared with those obtained over Al-beta catalysts. Mixed Fe-Al-beta catalysts showed remarkably high activity and selectivity to cumene and diisopropylbenzene.

Nickel/carbon composite materials based on expanded graphite

Abstract Monolithic nickel/carbon (Ni/C) composites were prepared from coal tar pitch-impregnated compressed expanded graphite pre-decorated with NiO particles (EGNiO) by pyrolysis at 550 °C and subsequent steam activation at 800 °C. The microstructural arrangement of the Ni-comprising nanoparticles in the composites was investigated using transmission electron microscopy. The specific surface area and porosity of the composites were analyzed by nitrogen adsorption. The catalytic activity of the composites was compared with the material obtained by the conventional H2 treatment of EGNiO using hydrocracking of 2,2,3-trimethylpentane as a model reaction.

Benzene alkylation with propylene over Ga, B and Al pentasils

Summary Benzene alkylation with propylene using Ga-, B- and Al-containing pentasil zeolites as catalysts was studied. Ga-zeolites were found to be more selective towards cumene formation than Al-zeolites, the overall activities being similar. The activity of Ga-containing catalysts increases with gallium content for zeolites having the concentration up to 0.5 atom of Ga per unit cell; at higher Ga-concentration it remained almost constant. Framework boron appeared to have no effect on the activity of MFI-catalysts.

25-O-05-Benzene alkylation with alkanes over modified MFI catalysts

Publisher Summary This chapter discusses benzene alkylation with alkanes over modified MFI catalysts. It describes benzene alkylation with ethane, propane, and i-butane on acidic H-MFI zeolite with silicon dioxide/alumina (SiO 2 /A1 2 O 3 ) ratio of 104; mixed (H-MFI + Pt/CeO2) catalytic systems and Pt/H-MFI bifunctional catalysts with platinum content of 0.3%. In some of the experiments, hydride-forming metals (M) are added to the catalytic systems to ensure H 2 removal from the reaction zone. The conversion of alkanes and the selectivity to the products of direct addition is found to increase in the following order of catalytic systems: H-MFI 2 H 6 3 H 8 4 H 10 ; their alkylating ability is found to increase in the reverse order.

Spark plasma sintering of cutting plates

Numerical modeling of the spark plasma sintering of square plates from aluminum-oxide and tungsten-carbide powder is considered. The rounding radius of the plates is 0.8, 1.2, or 1.6 mm. The distribution of the temperature and mechanical stress within each sample and also within the mold is determined. The results are used for preliminary assessment of the possibility of spark plasma sintering of cutting plates.

Magnetocaloric and Magnetoelastic Properties of the Gd5Si2Ge2 with Small Indium Substitutions in p-Sublattice

The purpose of this work was the complex investigation of magnetic, magnetocaloric and magnetoelastic properties of compounds based on Gd5Si2Ge2 with small In substitutions in p-sublattice. The conducted measurements revealed that both the magnetocaloric effect and the volume magnetostriction upon cooling reach the higher values than upon heating. Indium substitution leads to the appearance of the second maximum on the temperature dependence of the magnetocaloric effect resulting in the increase of the refrigerant capacity.

Acetone Sensing by Modified SnO2 Nanocrystalline Sensor Materials

A complementary gas sensor and gas chromatography/mass spectrometry study was performed to investigate the chemical basis of acetone vapor sensing via semiconductor metal oxide gas sensors. The effect of additives to nanocrystalline SnO2-based sensor materials was analyzed. The main process that contributes to the electrical yield of this interaction and thus to the sensor response is a complete acetone oxidation to CO2and H2O. At the same time it is clearly shown that this sensor response is severely limited by the rate of desorption of the reaction products. The main contributors to this negative influence on the sensor response are heavy organic compounds with molar masses larger than that of acetone. It is also shown that their negative effect could be mitigated by the incorporation of catalytic clusters of gold on the surface of SnO2based sensor materials. This kind of catalyst acts either as a preventor of the formation of heavy and complex organic molecules on the sensor surface or as a combustion catalyst, which facilitates their decomposition.

Pre-concentration of organophosphorous compounds on porous silica materials

Abstract Porous silica-based monoliths obtained by spinodal phase decomposition of water-tetraethoxysilane mixtures in the presence of polyethylene oxide were tested for pre-concentration of dimethyl methylphosphonate (DMMP) to increase the sensitivity of its detection by semiconductor gas sensors. The best performance in terms of complete adsorption/fast thermodesorption was shown by the sample with a surface area of 280 m 2 /g. The monoliths with lower surface area were not so effective in DMMP adsorption. while for the samples with higher surface area. the decrease of the sensor signal was observed due to impeded DMMP desorption.

Spark plasma sintering of nanostructured powder materials

Spark plasma sintering is a method of consolidating nanostructured powder materials and also composites and gradient materials in the presence of an electromagnetic field, by means of low-voltage sources of powerful current. The main benefit of spark plasma sintering is that previously impossible structures, properties, and compositions may be produced. The finite-element method is used to analyze the consolidation of samples by spark plasma sintering and by a hybrid method in which spark plasma sintering is combined with hot pressing. Corresponding numerical models are tested.