Platinized asbestos

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. 

Asbestos, platinized, 1 160 3 129 Atomic weight, determination of average, of rare earth elements in a mixture, 2 58 Azides, alkali and alkaline earth, 1 79 2 136, 139... 

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... 

Phenylcyclopropene (5). 3 (118 g 0 8 mol), powdered KOH (30 g, 0 S3 mol) and platinize asbestos (2 5 g) were heated slowly and the heat was shut off at the rirsi sign of reaction Afler the exolhemiic reaction the temperature was again raised and the product was distilled Both the distillate end the residue were steam distiled, the distitlate was extracted with Et20... 

Catalytic hydrogenation. Aqueous solution of FMN (50 pM) containing a small amount of platinized asbestos is babbled with hydrogen gas for 10-20 minutes, until the yellow color and green fluorescence of FMN completely disappear. A suitable setup for this purpose can easily be constructed using a small flask, a rubber septum and two syringe needles (used as the inlet and outlet of H2 gas). 

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. 

The platinized asbestos is filtered, washed once with 10% sulfuric acid, once with hot water, once with hot 5% hydrochloric acid, and finally with hot water until no test for chloride or sulfate is found. The product is dried at 110° and stored until needed in a covered container. Each gram of asbestos contains about 0.5 g. of platinum. 

The first explicit information appeared in 1953 in two U.S. patents (9) which showed that platinum black as well as platinized asbestos or silica were effective for addition of trichlorosilane to olefins. Platinum on charcoal was unusually active with trichlorosilane and acetylene, ethylene, butadiene, vinyl chloride, or vinylidene fluoride. Temperatures as low as 130°C were sometimes employed. 

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. 

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. 

Preparation of Nitric Acid by Oxidizing Ammonia. Assemble an apparatus as shown in Fig. 90. Pour a 2% ammonia solution into flask 1. Put a loose layer of freshly roasted platinized asbestos into the middle of tube 2 over a length of 4-5 cm. Pour a neutral litmus solution or several drops of methyl red into flask 3 and connect the short tube of this flask to water-jet pump 4. Heat the platinized asbestos slightly with the flame of a gas burner and pass through it... 

Palladized or platinized asbestos (or Deoxo unit) Removes traces of 02 from H2 at room temperature, removes 02 from inert gases at... 

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