Oxides of P, As, Sb, Bi

Ipatieff developed the solid phosphoric acid catalyst which has been employed for 

The catalyst can be deactivated by the modification of the acid components if it does not contain the proper amount of water.Excessive water causes the catalyst to get soft and the pellet to collapse, increasing the pressure drop in the bed. Too little water dehydrates the phosphoric acid to inactive polyphosphoric aeids therefore small quantities of water are added to the reaction mixture to maintain the optimum degree of hydration. 350 — 400 ppm H2O is the range for 473 — 593 K. The solid phosphoric acid catalysts are not easily regenerable. 

Solid phosphoric acid catalysts are also used for producing isopropylbenzene from a mixture of benzene and a refinery stream containing propene and propane. The carbonylation of alkenes and the hydration of olefins are also effected by supported phosphoric acid. 

The acid strength of H3P04/S102 was determined to be —5.6 to —8.2 in i/o-value by a titration method by Benesi.  

Hashimoto and Mitsutani found that phosphoric acid supported on silica, which were calcined at higher temperature (973—1473 K) had a high activity and selectivity for the preparation of isoprene by the decomposition of 4,4-dimethyl-meta-dioxane (MDO). 

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