Selective hydrogenation of maleic anhydride to gamma-butyrolactone over Pd/Al2O3 catalyst using supercritical CO2 as solvent

A selective hydrogenation of maleic anhydride to either gamma-butyrolactone or succinic anhydride over simple Pd/Al2O3 catalyst under supercritical CO2 medium is described for the first time which has considerable promise for both lab-scale as well as industrial selective hydrogenations of low vapor pressure compounds without employing environmentally harmful organic solvents.     

Cyclization of diols with ammonia over CuO-ZnO-Al2O3 catalyst in the presence of H2

Cyclization of diols with ammonia in an H₂ atmosphere over an industrial CuO-ZnO-Al₂O₃ catalyst for the synthesis of methanol (SNM-1) gives nitrogen-containing five-, six-, or seven-membered heterocyclic compounds. The yields of cyclic amines in the 180–230 °C temperature range are 46 to 97 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2046–2048, October, 1995.     

Reaction of silanes in supercritical CO2 with TiO2 and Al2O3

Infrared spectroscopy was used to investigate the reaction of silanes with TiO2 and Al2O3 using supercritical CO2 (Sc-CO2) as a solvent. It was found that contact of Sc-CO2 with TiO2 leads to partial removal of the water layer and to the formation of carbonate, bicarbonate, and carboxylate species on the surface. Although these carbonate species are weakly bound to the TiO2 surface and can be removed by a N2 purge, they poison the surface, resulting in a lower level of reaction of silanes with TiO2. Specifically, the amount of hexamethyldisilazane adsorbed on TiO2 is about 10% of the value obtained when the reaction is performed from the gas phase. This is not unique to TiO2, as the formation of carbonate species also occurs upon contact of Al2O3 with Sc-CO2 and this leads to a lower level of reaction with hexamethyldisilazane. This is in contrast to reactions of silanes on SiO2 where Sc-CO2 has several advantages over conventional gaseous or nonaqueous methods. As a result, caution needs to be applied when using Sc-CO2 as a solvent for silanization reactions on oxides other than SiO2.     

Transesterification of rapeseed oil in supercritical methanol in a flow reactor

Transesterification reactions of rapeseed oil in supercritical methanol in a flow reactor over a wide range of variation of the methanol/oil ratio, pressure, and contact time are studied. Conditions ensuring selectivity and a high degree of rapeseed oil conversion are found. Experiments to study this reaction in the presence of zeolite heterogeneous catalyst are performed.     

Dehydrogenation of cyclohexane over Pt/Al2O3 in the presence of ZrNi as a hydrogen acceptor

Conclusions The use of the ZrNi-H system as a hydrogen acceptor in a dehydrogenation reaction permits a significant increase in the conversion of cyclohexane to benzene due to a shift in the thermodynamic equilibrium upon the removal of hydrogen from the reaction stream. This permits us to carry out the reaction at a temperature 100–200°C below those commonly used and accumulate hydrogen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2405–2407, October, 1988.     

正己烷存在下的氢选择性催化燃烧

以正己烷作为裂解原料烃类代表,Pt-Sn/Al₂O₃催化剂作为氢选择性燃烧催化剂,对直接内加热方式提供热量促使裂解原料达到可裂解温度的可行性进行了研究。结果表明,温度相同时,Pt-Sn/Al₂O₃ 催化剂存在时氢燃烧的选择性明显高于无催化剂存在时的非催化氢燃烧过程,Pt-Sn/Al₂O₃ 催化剂是优良的氢选择性燃烧催化剂。该催化剂在催化氢选择性燃烧过程中,存在一个临界温度点650℃。当物流入口温度低于650℃时,氢燃烧选择性达90%以上;高于650℃时,由于非催化氢燃烧所占总燃烧反应比例加大,造成氢燃烧选择性有所降低。同时,在一定温度下,要获得高的氢燃烧选择性及氧气转化率,须综合考虑氢烃比和氢氧比的影响。     

Preferential CO oxidation promoted by the presence of H2 over K-Pt/Al2O3

In preferential CO oxidation in H2-rich gas, K-Pt/Al2O3(K/Pt = 10) was very effective in decreasing CO concentration below 10 ppm in the 375-410 K range, and the turnover frequency of the K-Pt/Al2O3 was 20 times as high as that of Pt/Al2O3 at 353 K; furthermore, the activity of CO oxidation was promoted drastically by the presence of H2.     

Al6Ti2O13, a new phase in the Al2O3–TiO2 system

The compound Al₆Ti₂O₁₃ (hexa­aluminium dititanium trideca­oxide) has been synthesized using an arc‐imaging furnace, which allows fast cooling of melted oxides. The structure consists of infinite double chains of polyhedra running along the c axis. These chains are built up by four kinds of strongly distorted oxygen octa­hedra randomly occupied by either Ti or Al (point symmetry m or m2m), and by trigonal bipyramids exclusively occupied by Al (point symmetry m2m).     

流化床反应器中不同Ni/Al2O3催化剂上CH4-CO2重整反应性能的比较研究

采用浸渍法、溶胶 凝胶过程与普通干燥、超临界干燥过程相结合的方法制备了三种20%的NiO-Al2O3体系催化剂，利用BET、XRD、H2 TPR、H2-TPD等方法对各催化剂样品物化性质进行了表征，并考察了催化剂在流化床反应器中CH4-CO2重整反应的催化性能。研究结果表明，经923K焙烧后气凝胶催化剂中镍与载体间作用力最强，主要为固定NiO和尖晶石NiAl2O4结构，而浸渍型催化剂和干凝胶催化剂中镍与载体间作用力较弱。三种催化剂中，气凝胶催化剂具有比表面积较大、堆密度较低、Ni还原度及分散度较高的特点。它在流化床反应器中所形成的聚团流态化状态具有较高的床层膨胀率，大量多孔疏松状的纳米颗粒聚团在床内的循环运动有效地提高了传质效率，能使得生成的沉积炭快速得到气化，从而抑制了催化剂失活；对于浸渍型催化剂和干凝胶催化剂，流化床反应器中床层膨胀率较低、颗粒循环量较少、传质效率较低，易于造成催化剂表面积炭失活。经用TG和XRD等方法对反应后催化剂分析表征，证明催化剂表面石墨碳的沉积是导致浸渍型催化剂和干凝胶催化剂失活的主要原因。     

Reactions of 9,10-phenanthrenequinone and its nitro derivatives with acetone in the presence of Al2O3

The addition of acetone to 9,10-phenanthrenequinone and 2-nitro-, 2,7-dinitro-, and 2,4,7-trinitro-9,10-phenanthrenequinones in the presence of Al₂O₃ affords mono- and bisadducts. The crystal structures of 10-hydroxy-10-(2-oxopropyl)-2-nitro-9,10-dihydrophenanthren-9-one and 9,10:10,9-bishemiketal of 9,10-dihydroxy-2-nitro-9,10-bis(2-oxopropyl)-9,10-dihydrophenanthrene were determined.     

Studies on the system Al2O3-V2O5-MoO3

Studies on the three-component system Al₂O₃-V₂O₅-MoO₃ have shown the existence of a new compound with molecular formula AlVMoO₇. The synthesis conditions and X-ray characteristics of this compound and its melting temperature, 690±10°C, are reported.

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Zusammenfassung Einleitende Untersuchungen am Dreikomponentensystem Al₂O₃-V₂ O₅-MoO₃ zeigten die Existenz einer neuen, noch nicht publizierten Verbindung der Formel AlVMoO₇. Die Synthese der Verbindung sowie ihre röntgenographischen Eigenschaften wurden beschrieben. Ihr Schmelzpunkt beträgt 690±10°C.

     

Styrene polymerization in the presence of the CpTiCl3/Al2O3–SiO2/MAO catalytic system

Syndiotactic polymerization of styrene in the presence of heterogenized hemititanocene catalysts CpTiCl₃/Al₂O₃–SiO₂/MAO (Cp = cyclopentadienyl; MAO = methylaluminoxane) showed that the yield and selectivity of this reaction depend on the support composition, i.e. on the Al₂O₃ content in the support. The most active catalysts contained Al₂O₃ in a quantity of 50 to 70 wt%. Despite a relatively lower selectivity of 75–59%, the amount of syndiotactic polystyrene in the presence of those catalysts was the greatest. Copyright © 2002 John Wiley & Sons, Ltd.     

Laser-induced luminescence of model Fe/Al2O3 and Cr/Al2O3 catalysts

The laser-induced luminescence of Cr³⁺ impurity ions in model Fe/Al₂O₃ and Cr/Al₂O₃ catalysts with different calcination temperatures was studied. It was found that an additional luminescence band at 770 nm appeared in the luminescence spectra of low-temperature samples as a result of the interaction of octahedrally coordinated Cr³⁺ ions with Fe³⁺ impurity ions. In the θ-Al₂O₃ phase with a concentration of Cr³⁺ ions higher than 0.1 wt %, the interaction of the Cr³⁺-Cr³⁺ ion pairs in the immediate surroundings resulted in the appearance of N _θ lines due to the splitting of R _θ lines. The differences of these lines from the N _α lines of α-Al₂O₃ were related to the individuality of the crystal lattice of the θ phase and the coordination of Cr³⁺ impurity ions in the immediate surroundings, which is different from that in the α phase. Based on the laser-induced luminescence spectroscopic data, it was found that regions with a local Cr³⁺ concentration higher than the average Cr³⁺ concentration in the bulk of a catalyst by one order of magnitude were formed in the α-Al₂O₃-Fe₂O₃ system with the bulk Fe and Cr concentrations of 2.5 and 0.04 wt %, respectively, which was calcined at 1220°C, as a result of the diffusion of chromium and iron ions.     

Ablation of Al2O3f/Al2O3 composites under an oxyacetylene torch flame

Journal of Sol-Gel Science and Technology - Continuous alumina fibers reinforced alumina matrix composites (Al2O3f/Al2O3 composites) were successfully synthesized via sol–gel procedure...     

Hydrodechlorination of chlorobenzene in the presence of Ni/Al2O3 prepared by laser electrodispersion and from a colloidal dispersion

The low-percentage Ni/Al₂O₃ catalysts with active metal contents of 0.0002–0.1 wt % were prepared using the laser electrodispersion (LED) method and by means of supporting from a colloidal dispersion (CD). Their composition and physicochemical properties were determined by atomic absorption spectrometry, transmission electron microscopy (TEM), and XPS. With the use of TEM, it was found that average size of nickel particles in the LED catalysts was smaller than that in the CD catalysts. According to XPS data, the supporting of a metal onto a substrate by the LED method makes it possible to obtain samples containing Ni metal with a low active metal content (0.03 wt %). They exhibited a high initial activity in the hydrodechlorination reaction of chlorobenzene in a vapor phase, which was performed in a flow system at temperatures of 100–350°C. The CD catalysts were active in this reaction only at temperatures of 300–350°C. Reductive treatment led to the deactivation of LED catalysts and increased the activity and stability of samples prepared by supporting from a CD. The possible reasons for the observed changes are considered.