Decomposition of hydrogen peroxide in the presence of mixed oxide catalysts

The decompn. of H2O2 in the presence of TiO2-​ZrO2, SiO2-​ZrO2, Al2O3-​ThO2, SiO2-​ThO2, Al2O3-​MoO3, SiO2-​MoO3, Al2O3-​WO3, and SiO2-​WO3 catalysts, ignited 6 hr at 120-​1000°, was studied chem. anal. and kinetically. Due to the bifunctional nature of these catalyst the effect of the acidic and basic sites on the decompn. was studied by poisoning the sites with Neutral Red and HCl, resp. Both the acidic and basic sites catalyze the decompn. The activation energy for the sites is inversely proportional to the acidity and basicity as calcd. from the initial slopes of the rate curves. The decompn. mechanism in the presence of acidic and basic sites is of similar character. Only acid sites of pKa -​3.0 and basic sites of pKa 10 catalyze the decompn

Cleavage of anisole by hydrogen chloride in nonaqueous media in the presence of inorganic catalysts

Anisole is cleaved and rearranged with HCl and Al2O3 or Cr2O3 catalysts, but is rearranged without cleavage by HCl-​SiO2 or by catalysts alone. A mechanism is proposed

Depolymerization of paraldehyde catalyzed by some silica- and alumina-​based binary oxide catalysts

Depolymerization of paraldehyde in C6H6 solns. is catalyzed by oxides supported on Al2O3 and SiO2. The acidity with pKa ≤-​3.0 is linearly related with catalytic activity (1st order rate const. k) for depolymerization of paraldehyde. Supported MoO3, WO3, and V2O5 have acid sites at pKa ≤-​3.0 and are catalytically active. Supported MgO, BeO, and ThO2 have very little acid strength at pKa ≤-​3.0 but have of weak acid sites at pKa ≤+3.3; these relatively weak acid sites are catalytically inactive. The obsd. rate consts. of SiO2-​supported catalysts are greater than those of the Al2O3 supported catalysts. The activation energies are inversely proportional to the acidity of the catalysts

Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes

[EN] The increasing environmental concern and promotion of “green processes” are forcing the substitution of traditional acid and base homogeneous catalysts by solid ones. Among these heterogeneous catalysts, zeolites and zeotypes can be considered as real “green” catalysts, due to their benign nature from an environmental point of view. The importance of these inorganic molecular sieves within the field of heterogeneous catalysis relies not only on their microporous structure and the related shape selectivity, but also on the flexibility of their chemical composition. Modification of the zeolite framework composition results in materials with acidic, basic or redox properties, whereas multifunctional catalysts can be obtained by introducing metals by ion exchange or impregnation procedures, that can catalyze hydrogenation–dehydrogenation reactions, and the number of commercial applications of zeolite based catalysts is continuously expanding. In this review we discuss determinant issues for the development of zeolite based catalysts, going from zeolite catalyst preparation up to their industrial application. Concerning the synthesis of microporous materials we present some of the new trends moving into larger pore structures or into organic free synthesis media procedures, thanks to the incorporation of novel organic templates or alternative framework elements, and to the use of high-throughput synthesis methods. Post-synthesis zeolite modification and final catalyst conformation for industrial use are briefly discussed. In a last section we give a thorough overview on the application of zeolites in industrial processes. Some of them are well established mature technologies, such as fluid catalytic cracking, hydrocracking or aromatics alkylation. Although the number of zeolite structures commercially used as heterogeneous catalysts in these fields is limited, the development of new catalysts is a continuous challenge due to the need for processing heavier feeds or for increasing the quality of the products. The application of zeolite based catalysts in the production of chemicals and fine chemicals is an emerging field, and will greatly depend on the discovery of new or known structures by alternative, lower cost, synthesis routes, and the fine tuning of their textural properties. Finally, biomass conversion and selective catalytic reduction for conversion of NOx are two active research fields, highlighting the interest in these potential industrial applications.The authors acknowledge financial support from Ministerio de Ciencia e Innovacion (project Consolider-Ingenio 2010 MULTICAT).Martínez Sánchez, MC.; Corma Canós, A. (2011). Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes. Coordination Chemistry Reviews. 255(13-14):1558-1580. doi:10.1016/j.ccr.2011.03.014S1558158025513-1

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

THE MECHANISM OF DEPOLYMERIZATION OF PARALDEHYDE CATALYZED BY SOME MIXED OXIDE CATALYSTS

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Mechanism of depolymerization of paraldehyde catalyzed by some mixed oxide catalysts

The kinetics of paraldehyde depolymn. over SiO2-​ZrO2, ZrO2-​TiO2, Al2O3-​ZrO2, Al2O3-​TiO2, MoO3, WO3, and V2O5 on SiO2 or Al2O3 fit the Michaelis-​Menten equation. The analogy between the depolymn. mechanism and enzymic activity was discussed