Method of preparing sodium nitrilotriacetate

Claim 1

In a continuous method of making sodium nitrilotriacetate in crystalline form by hydrolyzing nitrilotriacetonitrile in the presence of sodium hydroxide, the improvement comprising a. suspending nitrilotriacetonitrile in recycled mother liquor, said mother liquor containing sodium nitrilotriacetate and sodium hydroxide, the amount of sodium hydroxide contained in said mother liquor being from about 20 to 30 percent of the stoichiometric amount required to effect hydrolysis of said nitrilotriacetonitrile, the temperature of said suspension being maintained at from about 20* to 60*C, b. adding to said suspension an aqueous solution of sodium hydroxide in an amount of 3 moles of NaOH per mole of nitrilotriacetonitrile whereby the total amount of NaOH in the reaction mixture is about 3.6 to 3.9 moles per mole of nitrilotriacetonitrile, c. partially hydrolyzing said nitrilotriacetonitrile at a temperature of from about 65* to 75*C to form a mixture comprising sodium nitrilotriacetate and sodium-N-(2-acetamido)-iminodiacetate, d. completing the hydrolysis at a temperature which is higher than the temperature in step (c) and which is from about 70* to 90*C to form sodium nitrilotriacetate, e. separating and recovering sodium nitrilotriacetate crystals from said mother liquor, and f. thereafter recycling said mother liquor.