Gamma alumina oxide

The tendency for high surface area gamma-alumina to siater and lose that cmcial area duriag high temperature operatioa is retarded by the intimate additioa of several perceat of cerium oxide. The mechanism is stiU under debate but may iavolve a surface LN—aluminate species on the alumina. 

X-ray diffraction conducted on the codeposited powder revealed that the deposit obtained from a suspension of gamma alumina, which had been partially converted to the alpha phase, contained both phases of alumina. Whereas, the powder codeposited from a suspension having a 50 50 mixture of alpha to gamma alumina powder, consisted only of the alpha phase. Using a parallel plate electrode configuration, Chen et al. [31] concluded that only alpha alumina can be codeposited. Chen also observed a difference in codeposition with copper when using two different phases of the titanium oxide particle system rutile readily codeposited but anatase titania did not... 

These materials were made to contain 10 wt% oxides on gamma alumina. The percentage of SO2 removed after 50 minutes was measured, at 1250°F, for these additives at the 1 wt% level mixed with cracking catalysts. They were then ranked by the ratio of the % removed to that removed by cerium on alumina. 

Five types of commercial SOx catalysts were tested for comparative ranking. Three of these commercial-type additives were well defined materials high surface area gamma alumina 10% Ce, as cerium oxide, on gamma alumina and 100 ppm Ft on gamma alumina. 

Materials. The sodium n—decylsulfate (CioS0 ) from Kodak and the sodium n-dodecylsulfate (CiaSO ) from Fisher were purified by recrystallization from water and from methanol, followed by drying under a vacuum. The alumina used was Aluminum Oxide C (Degussa Inc.), a primarily gamma alumina, with a surface area of lOO m /g. The NaCl was Fisher reagent grade and the water was distilled and deionized. 

Coal and many coal-derived liquids contain polycyclic aromatic structures, whose molecular equivalents form radical cations at anodes and radical anions at cathodes. ESR-electrolysis experiments support this (14). Chemically, radical cations form by action of H2SO4 (15,19), acidic media containing oxidizing agents (15,20,21,22), Lewis acid media (18,23-35) halogens (36), iodine and AgC104 (37,38), and metal salts (39,40). They also form by photoionization (41,42,43) and on such solid catalytic surfaces as gamma-alumina (44), silica-alumina (45), and zeolites (46). Radical anions form in the presence of active metals (76). 

Ruitenbeek, M., Van Dillen, A.J., de Groot, E.M.F., Wachs, I.E., Geus, J.W. and Koningsberger, D.C. (2000) The structure of vanadium oxide spedes on. gamma-alumina an in situ X-ray absorption study during catalytic oxidation. Topics in Catalysis, 10 (3 ) 241-54. 

The dynamic membranes originally developed by Union Carbide are protected by three core patents U.S, 3977967, 4078112, and 4412921 (Trulson and Litz, 1976 Bibeau, 1978 and Leung and Cacciola, 1983) and their foreign equivalents. Those patents cover a broad range of metal oxides such as zirconia, gamma alumina, magnesia>alumina spinel, tantalum oxide and silica as the membrane materials and carbon, alumina, aluminosilicates, sintered metals, fiberglass or paper as the potential porous support materials. However, their marketed product, trade named Ucarscp membranes, focused on dynamic membranes of hydrous zirconium oxide on porous carbon support. 

H Schaper, h B M Doesburg, and L L v Reijen, The influence of lanthanum oxide on the thermal stability of gamma alumina catalyst supports. Appl Catal 7 211 (1983)... 

In general, a catalyst consists of a support (alumina, silica, silica-alumina), an active catalytic metal and, in some cases, a promoter (] ). The support is usually a high-surface-area (up to several hundred square meters per gram) porous solid. Gamma alumina, for example, has a surface area of 100-300 m /g. The support is not necessarily inert and may play a significant role in chemisorption and oxidation state control. The active metal, which may be deposited by several techniques, is highly dispersed on the support. The promoter is an additive that can Increase the activity of the metal and/or maintain the physical characteristics of the support. 

In all fractions, gamma-alumina was the only alumina phase detected. The fines contained significant amounts of a mixed-metal vanadate phase, denoted by the peaks labelled as "3." This mixed-metal phase may be composed of iron-vanadium-oxide or iron-vanadium-molybdenum-oxide, based on XRD patterns of available reference compounds. The extrudates, on the other hand, are dominated by peaks due to aluminum sulfate, "l," and vanadium pentoxide, "2," with little+ if ary, peaks due to the mixed-metal phase, 3, ... 

A similar result was reported by SCHAPER (ref. 15) for influence of lanthanum oxide on the stability of gamma alumina carriers. 

The active constituent of the catalyst is an oxide of tungsten prepared by partial reduction of WO - Unsupported WOj was found to have activity but better specific activity is obtained by depositing the oxide on a support. A number of grades of alumina and silica were tested. Gamma alumina was found to react with WOj at 400°C to a considerable extent to form aluminium tungstate. This was identified by XPS and tests on AljfWO ) showed it to be inactive as a catalyst for the isomerization reaction. 

One result of this work is the conclusion that in chromia-alumina, and in other supported oxides, there must be local concentration of the supported oxide. This conclusion is reached because the Weiss constant shows definite indication of exchange interaction at concentrations of the paramagnetic ion too low to cover the surface of the support with even a monolayer. Another conclusion is that the support is sometimes able to modify the relative stabilities of oxidation states in the supported oxide. For instance, manganese oxide supported on gamma-alumina tends to be stabilized in the tripositive state, while on high-area titania it reverts to the tetrapositive state. 

Voltz and Weller (13) studied a catalyst containing 20 % Cr203 supported on gamma-alumina. The x-ray patterns showed the presence of a-Cr203 and 7-AI2O3, but there was also a line corresponding to a spacing of 2.55 A which was more pronounced in the oxidized state and which may be due to... 

Volatilization and adsorption of lube oil by the catalysts is followed by catalytic oxidation to CO2 at higher temperatures as is shown in Figure 8. In the Pyran -GCMS experiments, CO2 is the only non-condensable oxidation product measured from the combustion of lube oil in the "lean" gas stream by either Catalyst "C" or the gamma-alumina. The onset of CO2 evolution with Catalyst "C" occurs at approximately 180°C, which is just above the temperature range for the lube oil volatilization curve which is also shown. Lube conversion to CO2 is virtually complete with Catalyst "C" as determined by CO2 mass balance (95-100%) and the absence of detectable condensable species. 

The typical activated aluminas used in water treatment are 28 X 48 mesh (0.6-0.3 mm diam) mixtures of amorphous and gamma aluminum oxide (y-AI2O3) prepared by low-temperature (300-600°C) dehydration of precipitated A1(0H)3. These highly porous materials have surface areas of 50-300 m /g. Using the model of hydroxylated alumina surface subject to protonation and deprotonation, the following ligand exchange reaction, Eq. (1), can be written for arsenate adsorption in acid solution (alumina exhaustion) in which =A1 represents the alumina surface and an overbar denotes the solid phase ... 

A rather effective catalyst proved to be the system of rhodium nanoclusters stabilized with pol5winylpirrolidone (PVP) and supported on finely dispersed oxides (gamma-alumina, silica, or titania) and modified with Cnd (Huang et al. ). With this system EtPy was hydrogenated at 25 C and 70 bar hydrogen in THE with a TOP of 58.6 min and an ee of 65.4%. 

Ordonez, S., Bello, L., Sastre, H., efaZ. (2002). Kinetics ofthe deep oxidation of benzene, toluene, n-hexane and their binary mixtures over a platinum on gamma-alumina catalyst, Appl. Catal. B ... 

Oxidation—In general, the metals-silver, vanadium, copper, molybdenum, platinum, palladium, cobalt, nickel, manganese, tin, and lead-in either oxide or metallic form, mounted on suitable supports, are used in the oxidation of hydrocarbons. For complete oxidation, active supports such as gamma aluminas have been used. For selective oxidation, alpha alumina or silicon carbide are employed. Sometimes bi-metals, tin-vanadium, iron-molybdenum, and vanadium-molybdenum are mounted on the carrier. 

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