Catalysts and Synthetic Reagents

Metallophosphorus compounds have particularly important applications as industrial catalysts, but these represent only a small fraction of phosphorus compounds known to have some degree of catalytic action [1]. Data for over 200 efficient P-containing catalysts was published in 2007 [2]. 

The synthetic reagent section below deals with the use of P compounds in the production of non-biological non-P-containing derivatives. Their role can be as catalysts, promoters, or as major reacting 

This acid which usually contains more P2O5 than superphosphoric acid is used industrially for its dehydrating and catalytic properties. For some applications, it has to be somewhat purer than the latter acid. Polyphosphoric acid has a high viscosity and is most easily handled in the form of pellets. These are obtainable by reacting with a porous material such as diatomaceous earth. 

Acylations and alkylations of phenols and phenol ethers are catalysed by polyphosphoric acid (12.256, 12.257). Phenyl esters are obtained from a carboxylic acid and a phenol (12.258) and certain aromatic acids are converted to the corresponding amine with polyphosphoric acid and hydrox-ylamine hydrochloride (12.259). 

Polyphosphoric acid functions as a catalyst in the formation of low-molecular-weight polymers up to C,2 (12.260), and it is also used to promote alkylation reactions such as (12.261) from which phenol and acetone can be derived. Some dehydrogenation reactions proceed at lower temperatures, and more efficiently, in the presence of polyphosphoric acid, than they do at the higher temperature and pressure otherwise used in cracking (12.262). 

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