Catalyst aluminum oxide

Oxathiane and -dithiane are formed from ethylene oxide and hydrogen sulfide at 200°C in the presence of an aluminum oxide catalyst (65). 

The reaction scheme is rather complex also in the case of the oxidation of o-xylene (41a, 87a), of the oxidative dehydrogenation of n-butenes over bismuth-molybdenum catalyst (87b), or of ethylbenzene on aluminum oxide catalysts (87c), in the hydrogenolysis of glucose (87d) over Ni-kieselguhr or of n-butane on a nickel on silica catalyst (87e), and in the hydrogenation of succinimide in isopropyl alcohol on Ni-Al2Oa catalyst (87f) or of acetophenone on Rh-Al203 catalyst (87g). Decomposition of n-and sec-butyl acetates on synthetic zeolites accompanied by the isomerization of the formed butenes has also been the subject of a kinetic study (87h). 

Finally, another type of defect one can study is a surface—e.g., the surface of an aluminum oxide catalyst containing iron in the surface layers. Figure 7 shows the Mdssbauer spectrum for " Fe in the surface layers of an aluminum oxide catalyst (6). One sees first of all a quadru-pole splitting which is unusually large for a ferric ion. This is caused by... 

The direct formation of the S—C bond to form thiophenes is better illustrated by the conversion of 2-alkylthiophenols (1) to benzothiophenes (2) (48JA1561). Passing (1 n =2) over a chromium-aluminum oxide catalyst at 475 °C gave (2 R = R = H) in about 20-25% yield, while similar treatment of (1 n - 3) gave (2 R = H, R = Me) in only 10-12% yield. 2-Mercaptostyrene also cyclized to (2) over this same catalyst, and a number of substituted derivatives of (1), where n =2 and R = 5-NH2, 3-NH2, 5-CN or 5-C02Me, were also converted to benzo[6]thiophene derivatives in low yield (56JOC265). 

Treatment of butadiene or 1,4-butanediol with hydrogen sulfide over an alumina catalyst, or an iron sulfide/alumina catalyst, leads to the formation of thiophene. This method has been more useful in the benzothiophene series. Styrene with four equivalents of hydrogen sulfide, when passed over an iron sulfide/aluminum oxide catalyst at 600 °C for 20 seconds, gave a 60% mole conversion to benzo[6]thiophene (47JA2008). Similar treatment of ethylbenzene over a chromium oxide-alumina catalyst gave an 18% yield of benzo[6]thiophene, accompanied by the evolution of hydrogen (48JA2495). 

The behavior of aluminum oxide as a catalyst is strongly dependent on its treatment. The solid tends to take up water to form sites where an oxide ion is converted to a hydroxide ion by accepting a proton. There are also sites that are Lewis acids where exposed aluminum ions reside (electron-deficient sites), and the oxide ions are Lewis bases. Because of these features, it is possible to some extent to prepare an aluminum oxide catalyst that has the necessary properties to match an intended use. 

For example, at 450° over aluminum oxide catalyst, furan is converted to pyrrole by ammonia and to thiophene by hydrogen sulfide. The yields are 30%. 

Dihydropyran (DHP), having an atmospheric boiling point of 86 °C and a very limited solubility in water (3 g in 100 g of water at 20 °C), can be produced from tetra-hydrofurfuryl alcohol by dehydration and ring expansion over an aluminum oxide catalyst at... 

Butadiene, a substance used industrially to make polymers, is prepared by thermal cracking of butane over a chromium oxide/aluminum oxide catalyst, but this procedure is of little use in the laboratory. 

The process gas from the combustion chamber is cooled in the waste heat boiler to the temperature required for the first reactor of ca. 300°C. In this reactor, filled with a cohalt-molybdenum catalyst (on an aluminum oxide support), the conversion of up to 80 to 85% of the hydrogen sulfide is carried out. After condensing out the sulfur formed at temperatures below 170°C, the temperature of the reaction gases is increased to the reaction temperature of the second reactor (ca. 220°C), which contains a highly active aluminum oxide catalyst with a large surface area (200 to 300 m /g) in which the residual hydrogen sulfide and sulfur dioxide react with one another. 

HIE) Liao, P. C., Wolf, E. E. Self-Sustained Oscillations During Carbon Monoxide Oxidation 1982 on a Platinum/y-Aluminum Oxide Catalyst. Chem. Eng. Commun. 13(4-6), 315-326... 

Alcohols can also be reduced to hydrocarbons by catalytic hydrogenation. 2,2,3-Trimethylbutan-l-ol is hydrogenated to trimethylbutane (triptane) in 56% yield in presence of a cobalt-aluminum oxide catalyst at 300° within 18 h this reduction cannot be effected with copper chromite.473 Further, aliphatic alcohols can be converted into hydrocarbons on a vanadium pentoxide-aluminum oxide catalyst.474 However, Raney nickel converts straight-chain primary alcohols into hydrocarbons containing one carbon atom less.475... 

A temperature of 330-340° and use of an aluminum oxide catalyst are necessary for conversion of tetrahydropyran into 1-phenylpiperidine by means of aniline 1105 tetrahydro-furan gives pyrrolidine under similar conditions.1106... 

Mono-, di-, and trimethylamines are obtained by the reaction of methanol with ammonia under a pressure of 50 atm at about 380-450 C, over an aluminum oxide catalyst. It is difficult and often uneconomical and im-... 

Acetate esters including ethyl acetate and isobutyl acetate are produced from acetaldehyde by Eastman Chemical using the Tishchenko route. In this process, an aluminum oxide catalyst is used to facilitate the conversion of ethanol via acetaldehyde to acetates. Acetates represent the largest use for acetaldehyde now that acetic acid is made primarily from methanol. 

The a-gel is completely free of electrolytes its surface is quite alkaline. The fresh gel is completely amorphous [19] it ages rapidly to bayerite via the intermediate stage of bohmite, the alkalinity of the surface decreasing considerably in the process [16, 17]. Aluminum oxides prepared from this gel are more active than the usual aluminum oxide catalysts [1]. 

Aluminum oxide catalysts are prepared by heating hydrargillite at 550-650 C (other aliuninum oxides give less active preparations) the content of water of crystallization is 1% or slightly less. 

Phenol is vaporized with recycled and make-up hydrogen and hydrogenated by excess hydrogen at temperatures of 120 to 200 °C and 20 bar on silica or aluminum oxide catalysts, which are modified with nickel. The cyclohexanol is separated by condensation. The yield of cyclohexanol is almost quantitative. 

Picolines and 5-ethyl-2-methylpyridine (X-S4) can also be converted to the corresponding acids in basic media containing lead dioxide or iron-aluminum oxide catalysts. Again elevated pressures and temperatures are required. 

Biobased ethylene can be produced from biobased ethanol. The ethanol can be fermented from sugars found in organic sources like corn, sugarcane, potatoes, etc. The two common sources of bioethanol are from corn in the United States or sugarcane in Brazil. Bioethanol is converted to ethene with an aluminum oxide catalyst. The ethene is polymerized to polyethylene. Figure 5.1 lists the molecular formula of ethanol, ethane, and polyethylene. 

Dumez and Froment [1976] studied the dehydrogenation of I-butene into butadiene on a chromium oxide/aluminum oxide catalyst in a differential reactor. This work is probably the first in which the experimental program was actually and uniquely based on a sequential discrimination procedure. The reader is also referred to a more detailed treatment of Dumez, Hosten, and Froment [1977]. The following mechanisms were considered to be plausible ... 

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