Thoria dioxide

The vapor-phase esterification of ethanol has also been studied extensively (363,364), but it is not used commercially. The reaction can be catalyzed by siUca gel (365,366), thoria on siUca or alumina (367), zirconium dioxide (368), and by xerogels and aerogels (369). Above 300°C the dehydration of ethanol becomes appreciable. Ethyl acetate can also be produced from acetaldehyde by the Tischenko reaction (370—372) using an aluminum alkoxide catalyst and, with some difficulty, by the boron trifluoride-catalyzed direct esterification of ethylene with organic acids (373). 

Thomson-Bertheiot principle phys chem The assumption that the heat released in a chemical reaction is directly related to the chemical affinity, and that, in the absence of the application of external energy, that chemical reaction which releases the greatest heat is favored over others the principle is in general incorrect, but applies in certain special cases. tam san ber te lo, prin-s3-p3l thoria See thorium dioxide. thor e-3 )... 

SYNS THORIA THORIUiM DIOXIDE THOROTRAST THORTRAST UMBRATHOR... 

Special Refractories.— Under certain conditions refractories of special qualities may be employed such as zirconium oxide, zirconium silicate, chromite, fused silica, boron nitride, aluminum nitride, lime, beryllium oxide, cerium dioxide, thoria, asbestos and various synthetic combinations. 

Thoria (Thorium dioxide), Th02- Mol. wt. 264.05. Suppliers Alfa, Fisher. 

Dehydration Alumina (see also Dihydropyrane, preparation). Boric acid. Boron triSuoride. N-Bromoacetamide-Pyridine-SOj. Dicyclohexylcarbodiimide. Diketene. Dimethylform-amide-Thionyl chloride. Dimethyl sulfoxide. Ethylene chlorophosphite. Florisil. Girard s reagent. Hydrobromic acid. Iodine. Mesyl chloride-Sulfur dioxide. Methyl chlorosulfite. Methylketene diethylacetal. Naphthalene-d-sulfonic acid. Oxalic acid. Phenyl isocyanate. Phosgene. Phosphorus pentoxide. Phosphoryl chloride. Phthalic anhydride. Potassium bisulfate. Pyridine. Thionyi chloride. Thoria. p-Toluenesulfonic acid. p-Toluenesulfonyl chloride. Triphenylphosphine dibromide. 

The decomposition products identified following reaction are not necessarily the primary compounds which result directly from the rate limiting step. Particularly reactive entities may rapidly rearrange before leaving the reaction interface and secondary processes may occur on the surfaces of the residual material which often possesses catalytic properties. The volatile products identified [144] from the decomposition of nickel formate were changed when these were rapidly removed from the site of reaction. The primary products of decomposition of thorium formate were identified [17] as formaldehyde and carbon dioxide, but secondary processes occurring on the residual thoria yielded several additional compounds. The oxide product similarly catalysed interactions between the primary products of decomposition of zinc acetate [145]. During the decomposition of rare earth oxalates, carbon monoxide disproportionates extensively to carbon dioxide and carbon [81,82]. 

Relatively little work has been done with carbon dioxide reduction for the fonnation of methane, however, because of the waste (if hydrogen involved when the process is considered from an economic standpoint. Promoter action of thoria on nickel has been studied by Taylor and Russell," the interaction of hydrogen and carbon dioxide on the surfaces of platinum and tungsten by Prichard and Hinshelwood,10" and the formation of formaldehyde by the action of carbon dioxide, hydrogen and... 

EINECS 215-225-1 HSDB 6364 Thoria Thorianite Thorium anhydride Thorium dioxide Thorium oxide Thorium oxide (Th02) Thorotrast Thortrast Umbrathor. Used in ceramics, gas mantles, nuclear fuel, medicine and non-silica optical glass. White crystalline powder mp = 3390 d = 10.0 insoluble in H2O carcinogen. 

Data are given for the heat content for thorium dioxide (to 1787 K). Impure thoria was purified from rare earths metals by dissolution in concentrated HCl and iodate precipitation, to give samples of 99.4% and 99.1% purity. No correction was made for the impurities. The samples were contained in a Pt-Rh cylinder and dropped into a copper block, whose temperature was monitored. The enthalpy increments were fitted to a four term extended Kelley equation from which the heat capacity was derived. 

The solid dioxide evaporates congruently at all temperatures. Above 2800 K, the thoria in equilibrium with Th(l) showed a measurable but thermodynamically insignificant hypostoichiometiy to a composition of ThOi ggg. The "effective" pressure, (/.e. the pressure assuming the vapour is composed entirely of Th02) is given by the equation login Pe /l>3r = - 35500/r + 8.265. 

In recent years a wide variety of inorganic, non-metallic materials has been developed for the electrical, nuclear power, and engineering industries. In the shaping and processing of these products some form of heat treatment is involved, and they too are regarded as ceramic materials. Examples are rutile, a form of titanium dioxide used for making ferroelectric materials steatite or talc, for electrical insulators alumina, zirconia, thoria and beryllia as refractories and electrical insulators, uranium oxide as a nuclear-fuel element, and nitrides and carbides as abrasives or insulators. 

Thorium metal powder has recently been produced in the U.K. - on a scale of at least 6 kg per batch by an all-chloride electrolytic route, and information is available upon which a large-scale process could be based. Thorium tetrachloride is first produced in situ in an inert melt composed of sodium chloride and potassium chloride in eutectic proportions. Thorium dioxide and carbon are reacted with gaseous chlorine under the surface of the melt at a temperature of about 800°C in the presence of a ferric chloride catalyst. The catalyst is added as iron powder or pyrite (FeSg) in quantity equal to about 4 per cent of the weight of thoria. The ferric chloride, once formed, behaves as a chlorine carrier in the melt, by virtue of its ready reduction to ferrous chloride and subsequent rechlorination back to ferric chloride in contact with chlorine, i.e. 

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