GB1431314A - Process for preparing ortho and polyphosphated composition - Google Patents

Abstract

1431314 Preparation of ortho and polyphosphated compositions S A CROS 19 July 1973 [24 July 1872] 34515/73 Heading C1A A process for preparing polymerizable monopotassium phosphate compositions comprises reacting phosphonite at 60-90‹ C. for at least 1 hour with an excess of 98% sulphuric acid and potassium sulphate in proportions corresponding to the equation 2Ca 3 (PO 4 ) 2 +5H 2 SO 4 + K 2 SO 4 #2H 3 PO 4 +2KH 2 PO 4 +6CaSO 4 in the presence of recycled wash waterderived from washing of filter cakes of the separated precipitates from above reaction, the reaction being carried out so that the composition of the aqueous phase is maintained at 16-22% of solubilized total P 2 O 5 , about 50% of which is present as free H 2 PO 4 . In a preferred second stage all the P 2 O 5 extracted in the first stage is converted into monopotassium orthophosphate of high purity by means of treatment of the above mother liquors with lime or phosphorite and K 2 SO 4 in the proportions equivalent to the following equations: or and the fluidity necessary for obtaining good filtration being maintained. Alternatively the mother liquors from the first stage may be converted into P-K or N-P-K polymers by a method in which the liquors are concentrated into a suspension containing 40-50% of total P 2 O 5 and polymerized by thermal treatment with anhydrous NH 3 , urea or KCl in the stoichiometrically equivalent amount corresponding to the amount of free P 2 O 5 present so as to obtain P-K or N-P-K formulations free from chloride and with degrees of polymerization of less than 30% for N-P-K granules and of 30-50% and up to 100% for clear liquid preparation and preparations in suspension.