GENERAL PROBLEMS OF CATALYSIS
A new approach to the synthesis of crystalline boehmite by microwave exposure at gibbsite is proposed at the work. The kinetics of solidphase transformations of gibbsite when microwave activation was investigated and the dielectric characteristics of the baseline and microwave activated samples of gibbsite were measured. It is shown that increasing the microwave activation time on gibbsite leads to increased tgδ values, that indicating better ability of microwave activated samples gibbsite to dissipate microwave energy through the formation of the amorphous component containing a different number of weakly bound molecular water. The chemical formula for the amorphous component can be represented in general form as Al2O3·xH2O (0,5 < x < 3,0). Presented results can serve as a basis for the development of new lowwaste, resource and energy saving methods for the synthesis of crystalline boehmite and getting from it, respectively γ-Al2O3 with unusual, compared to the known low-temperature modification of Al3+ oxides, acid-base and textural characteristics.
There were works to develop the advanced catalyst systems (PtCoCr/C) with a core-shell structure, where the core – a metal alloy, and the shell is rich in platinum. The works were made in Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences. Reduction of surface coverage of Pt in the shell by firmly chemisorbed oxygen is a novel feature of the catalyst providing corrosion resistance, activity, selectivity with O2 recovery to water. Architecture of cathode OIE was developed using PtCoCr/C, its tests were conducted (resource and accelerated stress testing) in TE with proton-conducting polymer electrolyte. It has been shown that achieved characteristics are not inferior to those characteristics on Pt/C catalyst, using PtCoCr/C (30 wt.% Pt) and
Pt reduction at the cathode twice. Furthermore, in the test conditions, the efficiency of use Pt in PtCoCr/C system was considerably higher than in Pt/C. These results open the possibility of transition to the next phase – the organization of production of modern low-temperature fuel cells with characteristics corresponding to the world standards, using local materials.
CATALYSIS IN CHEMICAL AND PETROCHEMICAL INDUSTRY
In vitro the comparative studies of propylene polymerization in liquid monomer on the titanium-magnesium catalyst IK-8-21, developed at the Boreskov Institute of Catalysis and on imported industrial catalysts (codename – ТМК-1, -2, -3) were carried out. The activity and stereo-specificity of the catalyst were estimated, also the properties of the resulting polypropylene: granulometric composition, physical and mechanical characteristics. It is shown that the catalytic properties of IK-8-21 catalyst are not inferior to foreign analogues in the synthesis of the polypropylene. Polypropylene powder produced on IK-8-21 is homogeneous and has a good morphology. Physical and mechanical properties of polypropylene synthesized in the domestic catalyst IK-8-21 close to those for polypropylene produced using imported catalyst TMK-1.
The results of studies of the reaction methylcyclohexane (MCH) dehydro- methylation (DHM) and the joint conversion fractions of naphtha and methanol on modified forms of mordenite and pentasil in the presence of various hydrogen acceptors (O2, CO2) are given in this article. The high selectivity of xylene isomers are observed on polycationic modifications HNa-CVM. In these catalytic systems DHM degree and dehydrodispropvitionation (DHD) of MCH with increasing ratio of О2 : СО2 in the range of 0,05 : 1÷1,5 grows, and dehydration degree of MCH to toluene remains practically unchanged. High yields of di-and trimethylbenzenes achieved by reacting methanol with gasoline fraction 100–140 °C, consisting essentially from С7–С8 hydrocarbon. The results can be used in the reforming of naphtha to increase the С8–С9 aromatics yield.
СATALYSIS IN PETROLEUM REFINING INDUSTRY
Effect of content and nature of nitrogenous compounds on the distribution of desired products in model hydrocarbons transformation is studied in cracking conditions on equilibrium zeolite catalyst. Cracking of n-undecane showed a decreasing almost in 2 times of conversion, yield of propane-propylene (PPF) and butane-butylene fraction (BBF) with increasing content of pyrrole in the feed up to 3000 ppm of nitrogen. Increasing the nitrogen content in the feedstock results to a nonlinear reduction of the cracking rate constants for the n-undecane reaction. It is established, the dependence of the yield of PPF, BBF, isobutane in BBF in n-undecane cracking in the presence of various nitrogenous compounds from the conversion stay constant, probably the poisoning occurs only as a result of blocking the acidic sites of the catalyst. It is established, that pyrrole, indole in the cracking of hydrocarbons n-undecane and decalin have the greater toxic effect, whey are strong hydrogen donors, which is accompanied by the formation of ammonia. Quinoline shows great poisoning ability in the catalytic cracking of cumene with low [H]-donor activity. In the catalytic cracking of not hydrotreated vacuum gasoil with a high content of aromatic structures the quinolin poisons catalyst greater than indole. During the processing of the heavy residue hydrocracking hydrocarbon-rich of paraffin-naphthene range, indole manifests the most poisonous ability.
«Angarsk plant catalysts and organic synthesis» offers modern catalysts for hydrotreating and dewaxing, which represent a single integrated catalyst system for diesel fuel productions. Optimization of technology for CVM zeolite synthesis conducted to improve the efficiency c dewaxing catalyst. Stage of hydrothermal treatment of silica is introduced, resulting in an increase of reactivity of silica, a reduce the duration of crystallization, and zeolite crystallite sizes decrease. Comparative testing of dewaxing catalysts – own developed (DEP) and industrial (SGK-1) was conducted. It has been established that the zeolite promotion (Zn2+ or La3+) leed to increasing the activity of the dewaxing catalyst and allows to obtain high yields of diesel fraction at a lower temperature than when using an industrial SGK-1. The results of the pilot tests on real feed have shown that the usege of an integrated system of catalysts AGKD-400/DEP provides diesel fuel filterability limit temperature minus 38 °C and 35 ppm sulfur content for at least 720 hours. The proposed catalytic system can be implemented in many refineries to produce EURO diesel.
Catalysts Pt/MOR/Al2O3 mordenite zeolite with a content of 10 to 50 wt.% are cooked. Solutions H2PtCl6 and [Pt(NH3)4]Cl2 was used comas the Pt precursor. Localization of platinum in MOR/Al2O3 mixtures support depends on the nature of the metal precursor, what is shown by transmission electron microscopy. The catalysts were tested in an isomerization reaction of n-heptane. It is shown that the best catalysts provide yield of desired products – di- and three methylsubstituted isomers of heptane at 21 wt.%, at a temperature 280 °C and at stable output of catalysate С5+ 79–82 wt.%. Catalysts may be used to improve the environmental performance of gasoline by their application in the isomerization of 70–105 °C naphtha fraction.
DOMESTIC CATALYST
The results of research into the development and optimization of the preparation method of the catalyst to be processed a hydrocarbons to carbon materials are presented in this article. The mechanochemical activation of metal oxides mixture in a planetary mill was chosen as the method of preparing the catalyst. This method allows to obtain in a single stage high-proof (the active component, 90–95 wt.%) oxide catalyst without the formation of harmful waste gases during calcination. For stabilization of such catalysts they are used a textural promoter which prevents caking of dispersed metal particles at high temperature of carbon materials synthesis. The paper contains a texture promoter selection and optimization of the preparation conditions of the oxide precursor nickel-copper catalyst.
BIOCATALYSIS
The first time Ru-containing catalysts based on hypercrosslinked polystyrene (MN 270) and its functionalized analogues (MN 100 and MN 500) were used in hydrogenation hydrolytic cellulose. Textural characteristics of polymeric supports and catalysts were determined by low temperature nitrogen adsorption. Experiments of the cellulose conversion to polyols in subcritical water were conducted in a steel reactor with a capacity of 50 cm3 at 245 °С, a hydrogen partial pressure 6 MPa and stirrer speed of 600 rpm. The dependence between the morphological parameters of the support and activity of the catalysts based on them is defined. It is shown that the catalyst 1,0 % Ru/SPS MN 270 shows the greatest activity. The total yield of sorbitol and mannitol is averaged 50 % with 85 % conversion of the cellulose, which is comparable to more complex and expensive catalysts. Development of highly efficient method for cellulosic biomass processing to feedstock for chemical synthesis and production of second-generation biofuels is possible while further optimizing the parameters of the cellulose conversion and improve the proposed catalysts.
Thermal destruction of palladium acetate at temperatures ranging from 200 to 325 °C in an industrial hypercrosslinked polystyrene MN-270 was investigated by TGA and XPS and described in this article. The studies have shown that the palladium acetate distributed into hypercrosslinked polystyrene collapses with forming of metal palladium at lower temperatures than the pure salt powder. The formation and stabilization of palladium clusters Pd7–Pd10 and their partial aggregation with the formation of palladium nanoparticles happens during the of destruction. The catalytic testing of obtained systems in the selective hydrogenation of the triple bond dimethyl-ethynyl carbinol in toluene at 90 °C showed their considerable superiority in activity and selectivity in comparison with a commercial Lindlyar catalyst: TOF increase more than doubled when the selectivity 97,8 %.
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ISSN 2413-6476 (Online)