| 摘要 |
PROBLEM TO BE SOLVED: To produce high purity phosphoric acid which has an extremely low impurity metal content and is used as a raw material for a cleaning agent by distilling a trialkyl phosphate that contains alkyl groups each having a prescribed number of carbon atoms to refine the trialkyl phosphate, adding the refined trialkyl phosphate to pure water, heating the resulting trialkyl phosphate aqueous solution under pressure without using any catalyst to hydrolyze the trialkyl phosphate and thereafter concentrating the hydrolyzate. SOLUTION: This production process comprises: distilling a trialkyl phosphate containing 1-4C alkyl groups under a reduced pressure or the like, to refine the trialkyl phosphate; adding the refined impurity-metal-free trialkyl phosphate to pure water, to form a trialkyl phosphate aqueous solution having an about 10-60 wt.% concentration; receiving the aqueous solution in a closed vessel the inside of which is coated with a fluororesin; hydrolyzing the received aqueous solution preferably at 120-160 deg.C, under a 3-30 kg/cm2 pressure for about 3-60 hr to obtain a hydrolyzate; and then concentrating the hydrolyzate preferably at about 60-100 deg.C under an about 10-100 torr reduced pressure, wherein the concentration under such a reduced pressure is performed while removing water and alcohol. Thus, the objective high purity phosphoric acid having an about <=10 ppb impurity metal content and an about 75-95% phosphoric acid concentration, can be produced.
|
