I.G. Danilova

La–Fe–O/CeO 2 Based Composites as the Catalysts for High Temperature N 2 O Decomposition and CH 4 Combustion

AbstractnSeveral composites were prepared by mechanochemical activation of the mixture of well-crystallized LaFeO3 and CeO2 (La:Cexa0=xa00.1, 0.8), including following calcination at 900xa0°C, and characterized by means of XRD, XPS, HRTEM, EDX and UV–Vis DRS. Their tests as catalysts for N2O decomposition and CH4 oxidation at 700–900xa0°C showed non-additively high activity of calcined composites in both reactions. 16O/18O exchange was performed at 800xa0°C in LaFeO3, CeO2 and two composites (both calcined and non-calcined, La:Cexa0=xa00.1) representing mainly unmodified CeO2 core covered by the finely dispersed LaFeO3, La and Fe oxides penetrating near surface layers of fluorite lattice. Namely calcined composite revealed the highest rate of oxygen transfer in the two-phase system “O2gas–surface–catalyst bulk” due to prominent increase of the rate of heteroexchange on the modified CeO2 surface at keeping unchanged the highest bulk oxygen mobility characterizing CeO2 that explained its activity in the reactions with oxygen participation.Graphical Abstract

Characteristics optimization of activated alumina desiccants based on product of a centrifugal thermal activation of gibbsite

Activated alumina desiccants modified with NaOH and KOH were synthesized from the product of a centrifugal thermal activation of gibbsite, with the subsequent hydration in an acid or alkaline medium, and their properties were studied. It was shown that the modification makes it possible to raise the dynamic capacity of desiccants produced from pseudoboehmite by up to a factor of 2 via formation of new super-strong basic centers the concentration of which grows with increasing content of an alkaline oxide. A correlation was found between the total concentration of basic centers on the surface of the desiccants and their dynamic capacity in drying of both dry and humid air. Use of the modified desiccants with high static and dynamic capacity will make it possible to improve the drying efficiency.

Study of acid-modified aluminum oxides produced by centrifugal thermal activation in dehydration of ethanol

Possibility of using products formed in centrifugal thermal activation of hydrargillite to obtain alumina catalysts washed to remove admixtures of alkali metals was considered. A comparison of the physicochemical and catalytic properties of the samples demonstrated that washing with water is more favorable than that with nitric acid; the catalytic activity and acid-base properties of the catalyst surface are determined not only by the content of Na, but also by the whole set of catalyst preparation conditions. The most active of the samples obtained in the study has acidity close to that of industrial aluminum oxide produced by the reprecipitation method, but surpasses it in activity: at 370°C, the total yield of ethylene and diethyl ether reaches a value of 88.8 mol %, which is 4% higher than that for the reference sample.

Silica-alumina based nickel-molybdenum catalysts for vacuum gas oil hydrocracking aimed at a higher diesel fraction yield

Nickel-molybdenum hydrocracking catalysts based on amorphous silica-aluminas (ASAs) with Si/Al = 0.3–1.5 have been prepared using chemicals and methods available for catalyst plants. The acidic properties of the ASA surface have been investigated by IR spectroscopy of adsorbed CO, and it has been demonstrated that the Si/Al ratio has an effect on the concentration and strength of Brønsted and Lewis acid sites in the ASA. The catalysts have been characterized by low-temperature nitrogen adsorption and transmission electron microscopy, and it was found that the Si/Al ratio in the ASA has a considerable effect on the textural properties of the catalysts and only a slight effect on the particle size of the sulfide active component. The catalysts have been tested in vacuum gas oil hydrocracking in a laboratory-scale high-pressure flow reactor under typical industrial hydrocracking conditions. The highest diesel fraction yield (>60 wt % at 400°C) has been obtained with the catalyst based on the Si/Al = 0.9 ASA, which has the strongest Brønsted acid sites. With the catalysts based on the Si/Al = 0.3 and 1.5 ASAs, the diesel fraction yield is much lower. This may be due to the lower concentration and strength of acid sites in these catalysts and their smaller specific surface area. The NiMo catalyst based on Si/Al ≈ 0.9 ASA is recommended for industrial use in refineries aimed at obtaining the maximum possible yield of low-sulfur, high-cetane, diesel fuels.

Enhancement of the Sorption Ability of Aluminum Oxide Desiccants by Alkaline Modification

The influence of impregnation of aluminum oxide desiccants prepared by centrifugal thermal activation of hydrargillite with alkali (KОН and NaOH) and carbonate (Na2CO3 and K2СО3) solutions on the physicochemical properties of the products was studied. Impregnation with alkali solutions increases the dynamic capacity of the desiccants by a factor of 2 and more, whereas impregnation with carbonate solutions decreases the sorption characteristics of the desiccants at similar texture characteristics. Introduction of alkaline modifiers leads to a considerable decrease in the concentration of Lewis acid sites on the surface and to an increase in the concentration of strong base sites. Linear correlation was revealed between the concentration of strong base sites on the surface of the desiccants and their dynamic capacity in drying of humid air. The desiccants modified by impregnation exhibit not only high static and dynamic capacity, allowing improvement of the drying efficiency, but also considerably enhanced mechanical strength.

Effect of boron on acid and catalytic properties of Pd-ZSM-23/Al2O3 catalysts in the reaction of diesel fuel hydroisomerization

Effect of the concentration and introduction method of boron on the acid characteristics and catalytic properties of Pd-ZSM-23/Al2O3 catalysts in hydroisomerization of diesel fuel was studied. It was found that raising the concentration of introduced boron in a support results in that the concentration of acid centers, specific surface area, and volume of micropores in the catalysts nonlinearly decrease. To obtain the optimal acidity it is primarily necessary to reduce the concentration of excessively strong Lewis acid centers in zeolites and also to reach a moderate concentration of Brønsted acid centers. The best catalytic properties are observed for the catalyst containing 0.5 wt % boron.

Vacuum gasoil hydrocracking over three-layered packages consisting of supported sulfide NiMo and NiW catalysts

A method for vacuum gas oil hydrocracking using a three-layered package of catalysts is proposed, in which the top layer is NiMo/Al2O3, the middle is NiM/AAS-Al2O3 and the bottom is NiM/Y-Al2O3, where M is molybdenum or tungsten, AAS-Al2O3 is a support with 70% amorphous aluminosilicate (AAS) and 30% aluminum oxide, and Y is an Al2O3 support with 30% zeolite Y and 70% alumina. The acidic properties of the catalysts are studied via the IR spectroscopy of adsorbed CO. The morphology of sulfide particles on a catalyst’s surface is studied by means of transmission electron microscopy. Textural characteristics of the supports and catalysts are studied via nitrogen porosimetry. Packages containing NiMo and NiW catalysts in different combinations are tested in the hydrocracking of vacuum gas oil. It is shown that replacing NiMo/AAS-Al2O3 with NiW/AAS-Al2O3 in a catalyst package containing only NiMo considerably raises the yield of the diesel fraction.