WO3/MO2 (M = Zr, Sn, Ti) heterogeneous acid catalysts: Synthesis, study, and use in cumene hydroperoxide decomposition

Thirty (5–40)% WO₃/MO₂ (M = Zr, Ti, Sn), heterogeneous acidic catalysts have been synthesized by two methods, specifically, via homogeneous acid solutions and from solutions brought to pH 9 with ammonia, both followed by calcination at 600–900°C. The catalysts have been characterized by IR spectroscopy and scanning electron microscopy, and their aqueous washings have been analyzed. Their acidity has been determined by the thermal analysis of samples containing adsorbed pyridine, and in terms of the proton affinity scale. Catalytic activities have been compared for cumene hydroperoxide (CHP) decomposition at 40°C in cumene and acetone. For all M, the catalysts are one type and contain W in strongly and weakly bound states, the latter being a polyoxometalate that can be washed off. Both tungstate phases are active in acid catalysis. Brønsted acid sites with a broad strength distribution have been found. The strongest of them are heteropolyacid protons. The catalysts 30% WO₃/SnO₂ and 20% WO₃/ZrO₂ (in acetone) and 10–20% WO₃/TiO₂ (in cumene) are the most active in CHP decomposition, and their activity is not related to their total acidity. Phases containing W⁶⁺ that form during the high-temperature synthesis are responsible for the high acidity, and additional protons that may appear owing to W⁶⁺ reduction can play only a minor role.     

Thiophene conversion in the BIMF process

Catalytic conversion of an oil distillate with the added extra amounts of thiophene over a zeolite catalyst was studied. The rate of the catalyst deactivation was found to increase with the increase in the thiophene concentration in the feed. A possible pathway of the thiophene conversion is discussed.     

Effect of mechanical activation on the catalytic, physical and chemical properties of copper oxide

Mechano-chemical activation of copper oxide powders leads to structural disordering of the near-surface layers of particles and, thus, to considerable variations in the catalytic properties of copper oxide.

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Adsorption of H3PW12O40 by porous carbon materials

Adsorption of H₃PW₁₂O₄₀ from water and organic oxygen-containing solvents (AcOH, Me₂CO, MeOH) by carbon mesoporous materials, viz., Sibunit and catalytic filamentous carbons (CFC), was studied. The amount of irreversibly sorbed heteropolyacid is 50—100 mg g^–1 of support and decreases in the series of solvents: H₂O > Me₂CO > AcOH > MeOH. The adsorption capacity of CFC depends on the specific surface, total pore volume, and microstructure of the CFC fiber.     

The Effect of Modification on the Structural,Acidic, and Catalytic Properties of a Layered Aluminosilicate

The effect of modification on the structural, acidic, and catalytic properties of a natural layered aluminosilicate containing 90% montmorillonite was studied. With the use of low-temperature nitrogen adsorption and XRD analysis, it was found that the addition of hydroxo complexes of aluminum prevents the silicate layers of the layered aluminosilicate from closing upon heating and results both in the formation of stable micropores and in a considerable increase in the specific surface area. The acidic properties of the H, Na, and Al forms of the layered aluminosilicate were studied by IR spectroscopy of adsorbed CO molecules and by the indicator method. After modification with hydroxo complexes of aluminum, the number of Lewis acid sites and the accessibility of acidic OH groups to CO adsorption increased. The total number and strength of acid sites increased as the calcination temperature of the layered aluminosilicate was increased. A correlation between catalytic activity in the reaction of acetone dimerization and the number of acid sites in different forms of the layered aluminosilicate was obtained.     

Influence of the texture and acid-base properties of the alumina-containing support on the formation of Co(Ni)-Mo catalysts for deep hydrodesulfurization of the diesel fraction

The influence of the texture of γ-Al₂O₃ on the formation of Co(Ni)-Mo catalysts for hydrodesulfurization of the diesel fraction is studied. As shown by low-temperature N₂ adsorption, X-ray diffraction, IR spectroscopy of adsorbed molecules, and high resolution electron microscopy (HREM), use of a support with a larger specific surface and a lower total concentration of terminal OH groups makes it possible to prepare more active catalysts. The electron density radial distribution method shows that the finely dispersed cobaltcontaining catalyst in its initial state contains CoMoO₄, Al₂(MoO₄)₃, and CoAl₂O₄, the last two phases being present in trace amounts. After the reaction, this catalyst contains cobalt-doped molybdenum sulfide. According to HREM data, the active phase of the cobalt-containing catalyst consists of layered sulfide association species Co_1.3Mo₂S_3.3, which differ in composition from the bulk phase CoMo₂S₄. It is assumed that, out of the 1.3 cobalt atoms in Co_1.3Mo₂S_3.3 0.3 Co occurs at the edges of the association species and 1.0 Co is intercalated into their interlayer space, and 0.7 S at the boundary between the association species and the Al₂O₃ phase is replaced by the corresponding amount of oxygen.     

Acid-base properties of single-phase aluminum oxides

It was found that the surface of single-phase aluminum oxides contains terminal, bridging, and hydrogen-bonded hydroxyl groups, which differ in both concentration and position of related absorption bands. A transition from -Al₂O₃ to -Al₂O₃ does not change the number of absorption bands, but the intensities of these bands decrease. The total concentration of Lewis acid sites in single-phase oxides increases from 2.5 to 5.34 µmol/m² for -Al₂O₃ and -Al₂O₃, respectively. As distinct from other species, -Al₂O₃ contains strong Lewis acid sites ((CO) = 2238 cm^–1). The total concentration of basic sites in aluminum oxides prepared by boehmite dehydration at 600, 800, and 1000°C decreases from 4.86 to 3.72 µmol/m².Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 141–146. Original Russian Text Copyright © 2005 by Kulko, Ivanova, Budneva, Paukshtis.