Formaldehyde → Ethylenediaminetetraacetic Acid

Participants

Reaction Conditions

Reaction Steps

1-mol of ethylenediamine (60.0-g) is mixed with 0.16-mol sodium hydroxide (12.8-g of 50% NaOH) and raised to 70° C. 1.95-mol of sodium cyanide (318.4-g of 30% aq sln) and 1.99-mol of formaldehyde (119.2-g of 50% aq sln) are added at a constant rate over 2-hrs, quickly allowing the mixture to heat to boiling temperatures. At the start of the addition and throughout the reaction, steam is used to distill off the ammonia. Another 1.95-mol of sodium cyanide (318.4-g of 30% aq sln) and 1.99-mol of formaldehyde (119.2-g of 50% aq sln) are added at a constant rate over 4-hrs to complete the reaction. Upon completion of the addition, the reaction is boiled for 2-hrs to remove any excess ammonia. 222.2-mol of water (151.3-g) are added back to the reaction and the reaction is cooled to room temperature. The resulting product contains 39.24-wt % Na4EDTA and 0.4-wt % Na3NTA, as determined by HPLC analysis.

Provenance & Evidence