Carbon monoxide oxidation manganese dioxide catalyst

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

A catalyst that has been used effectively for oxidizing traces of acetylene in the air feed to low temperature separation plants and for providing hydrocarbon-free air for instruments and other special applications consists of a mixture of manganese dioxide and copper oxide, called Hopcalite. This catalyst also converts traces of carbon monoxide to carbon dioxide and u-aces of ozone to oxygen. The basic composition is about 60% manganese dioxide and 40% copper oxide however, relatively small additions of silver as a promoter have been found to make the catalyst particularly effective for most air streams (Rushton, 1954). Hie degree of conversion of several hydrocarbons over a commercial Hopcalite catalyst as a function of temperature is shown in Figure 13-10. 

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