Sulfuric Acid → Phosphoric Acid

HRID 1764615Notes

Reaction equation

HRID 1764615 reaction equation
[S:1](=[O:5])(=[O:4])([OH:3])[OH:2].[O:6]=[P:7]12[O:18]P3(OP(OP(O3)([O:14]1)=O)(=O)[O:8]2)=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[F-].[Ca+2:36].[Ca+2].[Ca+2].[Ca+2].[Ca+2]>O>[P:7](=[O:6])([OH:18])([OH:14])[OH:8].[OH2:2].[S:1]([O-:5])([O-:4])(=[O:3])=[O:2].[Ca+2:36].[Ca+2:36].[S:1]([O-:5])([O-:4])(=[O:3])=[O:2]

Participants

6

Reactant 3

HCID 1118Sulfuric Acid4×HCID 14812Phosphorus oxide (P4O10)HCID 10207414Fluorapatite (Ca5F(PO4)3)

Product 2

HCID 1004Phosphoric AcidHCID 3033839Calcium Sulfate, Hemihydrate

Reagents, catalysts & solvents 1

HCID 962WaterSolvent

Conditions

Temperature
265 fahrenheit

Procedure

Concentrated sulfuric acid containing 93% by weight of H2SO4 was continuously pumped to a mixing tee. Also continuously added to the mixing tee was gypsum pond water containing about 0.9% by weight of P2O5, about 0.2% by weight of CaO (2,000 ppm), and about 0.4% H2SO4 and having a pH of about 2.3. Sufficient amounts of gypsum pond water were added to the concentrated acid to produce a diluted acid having about 72% by weight of H2SO4. The diluted acid at a temperature of about 265° F was then cooled in a shell-and-tube heat exchanger through which cooling water flowed on the shell side. The diluted acid, at an exit temperature of about 140° F, was fed directly to a digestion tank containing ground phosphate rock to produce wet phosphoric acid and by-product calcium sulfate hemihydrate. The process was operated for five days, during which the following data was obtained periodically:

Workup

  1. additionAlso continuously added to the mixing tee
  2. customto produce a diluted acid
  3. temperatureheat exchanger through which
  4. customat an exit temperature of about 140° F

Sources & evidence

ORD record
ord-f2b7c81ac7d4435db696b59fa5cff29d
Source dataset
uspto-grants-1978_09
Patent number
US04117091

Reaction notes

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