Purification of wet process phosphoric acid using methyl-iso-butyl ketone

Claim 2

A SOLVENT EXTRACTRON PROCESS FOR PURIFYING IMPURE WET PROCESS PHOSPHORIC ACID OBTAINED BY ACTION OF SULPHURIC ACID ON PHOSPHATE ROCK COMPRISING THE FOLLOWING STEPS: A. CONTACTING SAID IMPURE WET PROCESS PHOSPHORIC ACID WITH METHYL ISOBUTYL KETONE TO FORM AN ORGANIC PHASE OF METHYL ISOBUTYL KETONE AND EXTRACTED PHOSPHORIC ACID, AND AN AQUEOUS PHASE RAFFINATE, SAID WET PROCESS PHOSPHORIC ACID BEING AN IMPURE AQUEOUS PHOSPHROTIC ACID HAVING AN ACID CONTENT IN THE RANGE OF 70-85 PERCENT, SAID ACID CONTENT BEING THE WEIGHT PERCENTAGE OF PHOSPHORIC AND SULPHURIC ACIDS CONTAINED THEREIN, THE WEIGHT RATIO OF METHYL ISOBUTYL KETONE TO SAID AQUEOUS IMPURE PHOSPHORIC ACID BEING FROM 0.5 : 1 TO 2.1, B. SEPARATING SAID ORGANIC PHASE FROM SAID AQUEOUS PHASE RAFFINATE, C. SCRUBBING SAID ORGANIC PHASE BY CONTACTING SAID ORGANIC PHASE WITH AN AQUEOUS PHOSPHORIC ACID SCRUB SOLUTION, SAID SCRUB SOLUTION CONTAINING PHOSPHORIC ACID IN AN AMOUNT OF AT LEAST 10 PERCENT OF THE AMOUNT OF PHOSPHORIC ACID IN SAID ORGANIC PHASE BEING SCRUBBED, D. RELEASING THE PHOSPHORIC ACID FROM SAID SCRUBBED ORGANIC PHASE BY CONTACTING THE SCRUBBED ORGANIC PHASE WITH RELEASE WATER IN AT LEAST TWO COUNTER CURRENT STAGES TO FORM AN AQUEOUS PHASE CONTAINING PURIFIED PHOSPHORIC ACID, AND AN ORGANIC METHYL ISOBUTYL KETONE PHASE, THE WEIGHT RATIO OF SAID RELEASE WATER TO SAID SCRUBBED ORGANIC PHASE BEING IN THE RANGE OF 0.1 : 1 TO 0.3 : 1 BASED ON THE WEIGHT OF SAID ORGANIC PHASE, E. SEPARATING SAID AQUEOUS PHASE FROM SAID METHYL ISOBUTYL KETONE, AND F. RECYCLING SAID METHYL IS ISOBUTYL KETONE TO STEP (A).

Claim 3

The process of claim 1 wherein said wet process phosphoric acid is contacted with said methyl isobutyl ketone at a temperature below 50*C, the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid being from 1 : 1 to 1.5 : 1, and wherein said scrub solution contains phosphoric acid in an amount between 30 and 50 percent of the amount of phosphoric acid in said organic phase being scrubbed.

Claim 4

The process of claim 2 wherein said impure wet process phosphoric acid is contacted with methyl isobutyl ketone in two counter current stages at a temperature between 25*C and 50*C.

Claim 5

The process of claim 3 wherein the phosphoric acid is released from the scrubbed organic phase at a temperature in the range 20*-40*C.

Claim 6

The process of claim 4 wherein said aqueous phosphoric acid scrub solution is formed by contacting water with said organic phase containing extracted phosphoric acid to re-extract phosphoric acid thereby forming said scrub solution.

Claim 7

The process of claim 4 wherein said aqueous phosphoric acid scrub solution is a portion of said aqueous phase containing purified phosphoric acid obtained in step (d).

Claim 8

The process of claim 3 wherein said release water is an aqueous solution of a base thereby neutralizing phosphoric acid in said aqueous phase.

Claim 9

The process of claim 5 wherein said release water is an aqueous solution of a base thereby neutralizing phosphoric acid in said aqueous phase.

Claim 10

The process of claim 1 wherein said release water is an aqueous solution of a base thereby neutralizing phosphoric acid in said aqueous phase.

Claim 11

The process of claim 9 wherein said wet process phosphoric acid is contacted with said methyl isobutyl ketone at a temperature below 50*C, the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid being from 1 : 1 to 1.5 : 1; and wherein said scrub solution contains phosphoric acid in an amount between 30 and 50 percent of the amount of phosphoric acid in said organic phase being scrubbed.

Claim 12

The process of claim 10 wherein said impure wet process phosphoric acid is contacted with methyl isobutyl ketone in two counter current stages at a temperature between 25* and 50*C.

Claim 13

The process of claim 1 wherein said wet process phosphoric acid is an impure aqueous phosphoric acid having an acid content in the range of 74- 79%, and wherein said impure wet process phosphoric acid is contacted with methyl isobutyl ketone at a temperature between 25* and 50*C.

Claim 14

The process of claim 12 wherein the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid is from 1 : 1 to 1.5 : 1; and wherein said scrub solution contains phosphoric acid in an amount between 30 and 50% of the amount of phosphoric acid in said organic phase being scrubbed.

Claim 15

The process of claim 13 wherein the phosphoric acid is released from said scrubbed organic phase at a temperature in the range 20* to 40*C, wherein said aqueous phosphoric acid scrub solution is formed by contacting water with said organic phase containing extracted phosphoric acid to re-extract phosphoric acid thereby forming said scrub solution, and wherein the weight ratio of release water to said scrubbed organic phase is in the range of 0.1 : 1 to 0.2.1.

Claim 16

The process of claim 13 wherein said release water is an aqueous solution of a base thereby neutralizing phosphoric acid in said aqueous phase.

Claim 17

The process of claim 1 comprising the following steps: a. contacting said impure wet process phosphoric acid with methyl isobutyl ketone in two counter current stages at a temperature between 25* and 50*C to form an organic phase of methyl isobutyl ketone and extracted phosphoric acid, and an aqueous phase raffinate, said wet process phosphoric acid being an impure aqueous phosphoric acid having an acid content in the range of 74-79 percent, said acid content being the weight percentage of phosphoric and sulphuric acids contained therein, the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid being from 1 : 1 to 1.5 : 1; b. separating said organic phase from said aqueous phase raffinate; c. scrubbing said organic phase by contacting said organic phase with an aqueous phosphoric acid scrub solution, said scrub solution containing phosphoric acid in an amount between 30 and 50 percent of the amount of phosphoric acid in said organic phase being scrubbed; d. releasing the phosphoric acid from said scrubbed organic phase by contacting the scrubbed organic phase with release water in two counter current stages to form an aqueous phase containing purified phosphoric acid, and an organic methyl isobutyl ketone phase, the weight ratio of said release water to said scrubbed organic phase being in the range of 0.1 : 1 to 0.2 : 1 based on the weight of said organic phase; e. separating said aqueous phase containing purified phosphoric acid from said methyl isobutyl ketone, said aqueous phase containing a total metallic contEnt less than 100 ppm relative to phosphoric acid; and f. recycling said methyl isobutyl ketone to step (a).

Claim 18

The process of claim 16 wherein the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid is from 1.3 : 1 to 1.5 : 1, wherein said phosphoric acid is released from said scrubbed organic phase at a temperature in the range of 20* to 40*C, and wherein said aqueous phosphoric acid scrub solution is formed by contacting water with said organic phase containing extracted phosphoric acid to re-extract phosphoric acid thereby forming said scrub solution.

Claim 19

The process of claim 16 wherein the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid is from 1.3 : 1 to 1.5 : 1, wherein said phosphoric acid is released from said scrubbed organic phase at a temperature in the range of 20* to 40*C, and wherein said aqueous phosphoric acid scrub solution is taken from a portion of said aqueous phase containing purified phosphoric acid obtained in step (d).

Claim 20

The process of claim 16 wherein said aqueous phosphoric acid scrub solution is formed by contacting water with said organic phase containing extracted phosphoric acid to re-extract phosphoric acid thereby forming said scrub solution, and wherein said release water is an aqueous solution of a base thereby neutralizing phosphoric acid in said aqueous phase.

Claim 21

The process of claim 19 wherein the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid is from 1.3 : 1 to 1.5 : 1.

Claim 22

The process of claim 1 comprising the following steps: a. contacting said impure wet process phosphoric acid with methyl isobutyl ketone in two counter current stages at a temperature between 25* and 50*C to form an organic phase of methyl isobutyl ketone and extracted phosphoric acid, and an aqueous phase raffinate, said wet process phosphoric acid being an impure aqueous phosphoric acid having an acid content in the range of 70-85 percent, said acid content being the weight percentage of phosphoric and sulphuric acids contained therein, the weight ratio of methyl isobutyl ketone to said aqueous impure phosphoric acid being from 1 : 1 to 1.5 : 1; b. separating said organic phase from said aqueous phase raffinate; c. scrubbing said organic phase by contacting said organic phase with an aqueous phosphoric acid scrub solution, said scrub solution containing phosphoric acid in an amount between 30 and 50 percent of the amount of phosphoric acid in said organic phase being scrubbed; d. releasing the phosphoric acid from said scrubbed organic phase by contacting the scrubbed organic phase with release water in two counter current stages to form an aqueous phase containing purified phosphoric acid, and an organic methyl isobutyl ketone phase, the weight ratio of said release water to said scrubbed organic phase being in the range of 0.1 : 1 to 0.2 : 1 based on the weight of said organic phase; e. separating said aqueous phase containing purified phosphoric acid from said methyl isobutyl ketone, said aqueous phase containing a total metallic content less than 100 ppm relative to phosphoric acid, and f. recycling said methyl isobutyl ketone to step (a).

Claim 23

The process of claim 16 wherein said aqueous phase containing purified phosphoric acid contains between about 50 and 70 percent of the amount of phosphoric acid in said impure wet process phosphoric acid which is contacted with methyl isobutyl ketone in step (a).