Platinized asbestos catalyst

Some early observations on the catalytic oxidation of SO2 to SO3 on platinized asbestos catalysts led to the following observations (1) the rate was proportional to the SO2 pressure and was inversely proportional to the SO3 pressure (2) the apparent activation energy was 30 kcal/mol (3) the heats of adsorption for SO2, SO3, and O2 were 20, 25, and 30 kcal/mol, respectively. By using appropriate Langmuir equations, show that a possible explanation of the rate data is that there are two kinds of surfaces present, 5 and S2, and that the rate-determining step is... 

Electrolytic hydrogen is passed through traps cooled to —180°C and filled with activated charcoal, and thereafter it is freed of Og by contact with platinized asbestos catalyst. 

The old chamber process used oxides of nitrogen to oxidize SO2 to SO3. This process could not produce higher strengths of the product acid. It was replaced by the contact process where the SO2 was converted to SO3 by the platinized asbestos catalyst. The plants running on this process could produce sulfuric acid of 98.5% strength. 

The first major use of heterogeneous catalysis in a modern chemical process was the contact sulfuric acid process developed by Kneitsch and Rrauss at BASF around 1900. They used a platinized asbestos catalyst to convert sulfur dioxide to... 

Hoffmaim developed flameless combustion of methanol in 1867. He used a platinum coil as a caMyst that glowed red hot as the methanol dehydrogenated and produced some formaldehyde. A commercial plant was designed by Trillat in 1889 to convert a methanoFair mixture into formaldehyde nsing a platinized asbestos catalyst. Trillat subsequently showed that other catalysts could also be used, such as oxidized copper at 330°C, although platinum at 200°C was most effective. Yields of about 50% formaldehyde were produced and he claimed that the addition of 20% steam to the gases improved performance. 

Balthis and Bailar6 obtained tris (ethylenediamine) chromium-(III) complexes by the oxidation of chromium(II) solutions, using a procedure somewhat similar to that used for the synthesis of cobalt (III) com plexes. Mori7 described the preparation of hexaamminechromium(III) salts from the oxidation of chromium (II) salts in the presence of ammonia. The results obtained in both syntheses have been erratic.8,9 Berman noted that the foregoing syntheses are rendered dependable by the use of a catalyst of activated platinum on asbestos. Schaeffer,100 in a subsequent study, independently used colloidal platinum as a catalyst but reported some difficulty in separating it from the product.106 The procedures recommended and described here are based on the use of platinized asbestos as the catalyst. 

Hydrogen bromide gas may be produced by combustion of hydrogen in bromine vapor at 37.5°C using a catalyst such as platinized asbestos or platinized silica gel. Unreacted free bromine is removed from the product by passing the gaseous product mixture over hot activated charcoal. Hydrogen bromide formed may be absorbed in water to obtain the acid or may be cooled and liquefied for shipment in cylinders. 

Conversion of sulfur dioxide to trioxide requires a suitable catalyst. Vanadium pentoxide, V2O5, is probably the most effective catalyst for the contact process. Vanadium and potassium salts supported on diatomaceous earth, platinized asbestos, platinized magnesium sulfate, and ferric oxide also have proved to be efficient catalysts. 

Prepare platinized asbestos as follows put 5 g of purified asbestos into a bowl and pour a 1-2% cbloroplatinic acid solution over it. Transfer the fibres impregnated with the solution into a porcelain crucible and roast them first carefully, and then strongly on a blowtorch. Store the prepared catalyst in a jar with a ground-glass stopper. Roast the platinized asbestos -without fall before each experiment. 

A variety of diverse synthetic methods have been empioyed for the preparation of cyclopropane (1 j. Schlatter and Demjanov and Dojarenko pyrolyzed cyclopropyltrimethylammonium hydroxide at 320°C using platinized asbestos as the catalyst. About equal amounts of cyclopropene (1) and cyclopropyidimethylamine are formed, contaminated with some dimethyl ether and ethylene. Treatment with dilute hydrochloric acid removed the amine from the gas stream and 1 was separated from the other products by gas chromatography. Alder-Rickert cleavage of the Diels-Alder adduct formed from cycloheptatriene and dimethyl acetylenedicarboxylate resulted only in the formation of a polymer and trace amounts of 1. A simple approach by Closs and Krantz based on the synthesis of 1-methylcyclopropene involved the addition of allyl chioride to a suspension of sodium amide in mineral oil at 80°C. Under the conditions employed, 1 could readily escape from the reaction mixture. Though a number of variations were tried, the yield of 1 never exceeded 10%. 

If ortho-hydrogen remains after liquefaction, the heat of transformation described previously will be released slowly as the conversion proceeds. Long-term storage of hydrogen requires that the hydrogen be converted from its ortho form to its para form to minimize boil-off losses. This can be accomplished using a number of catalysts including activated carbon, platinized asbestos, ferric... 

The primary oxidation products were passed through several layers of platinized asbestos and platinum wire formed into a star pattern. A series of experiments on the combustion of diphenyl sulphoxide showed that at 850°C and in the presence of a platinum catalyst sulphur is quantitatively converted into sulphur dioxide with no sulphur trioxide being produced. The oxidation temperature can be increased to 1200°C if a vanadium catalyst is used. The water is absorbed in a tube containing calcium sulphate, which helps to prevent the formation of sulphurous acid. Carbon dioxide and sulphur dioxide were concentrated in a U-shaped trap cooled with liquid nitrogen, and were subsequently analysed by GC at 92°C using a 6-m column filled with dinonyl phthalate. The content of sulphur in the sample was derived from the sulphur dioxide peak area with due regard to the weight of the sample and the calibration coefficient. 

Zelinsky and Borisoff give the following directions for preparation of platinized or palladized asbestos catalysts 140... 

Such polymerization can be avoided by using a catalyst composed of a Group VIII metal or a derivative thereof, e.g., platinum (as platinum black or platinized asbestos or charcoal), hydrogen hexachloroplatinate, or ruthenium chloride then the 1 1 adducts can be obtained in good yield from olefins such as styrene, acrylonitrile, and methacrylic esters with, e.g., dichloro(methyl)-silane 347-349 nevertheless it is advantageous to exclude oxygen and add a polymerization inhibitor such as te/7-butylpyrocatechol or 2,6-di-terf-butyl-4-methylphenol. 

The experiments of Zelinsky and Borisov (21) appear to substantiate that piperidine is the intermediate. A high yield of it was obtained in a flow type hydrogenation of pyridine in the presence of palladized or platinized asbestos. A similar flow type reaction with the same catalysts (22) gave not only piperidine, but side products which the investigators suggest might be 1,2,3,4-tetrahydropyridine and 1,2,5,6-tetra-hydropyridine (2-piperideine). The observation, however, needs further confirmation. Reinvestigation of the products of reaction with modern... 

In this case also, charcoal was the only successful catalyst under the moderate conditions of temperature used. Negative results were obtained with platinized asbestos, palladized asbestos, nickel (supported on silica... 

Certain catalysts that have high initial costs rrray also have high salvage valrre, which may partially offset the cost of replacement, e.g. rrse of platinized asbestos compared to vanadium pentoxide for the manufactirre of sirlphtrric acid. However, the choice will depend on other factors also (as discussed above), besides impact on the cost of production by use of a particirlar catalyst. One should also cortsider the likely corrosion of eqiripment and wastage of raw materials due to incomplete conversion by use of cheap catalyst. 

BASF Platinized asbestos produced by impregnating asbestos with platinic chloride solution followed by reduction with formaldehyde. Operated up to 10-12 years in several 10 20 cm layers. Contained 8-10% platinum. Tubular reactors were still designed for vanadium catalysts until 1950s. Agreement with Grillo up to 1898. 

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