Abstract

Provided are a method for effectively removing triuret from aqueous urea, a method for producing high purity aqueous urea, and a method for recovering triuret from aqueous urea. To this end, the method for producing aqueous urea comprises a step of dissolving aqueous urea in water to form aqueous urea, a step of bringing the aqueous urea to a temperature in a range of 17°C or less to 5°C or more to make the aqueous urea cloudy, and a step of passing the clouded aqueous urea through an ion exchange resin. The present invention is also a method for removing and recovering triuret from aqueous urea, the method comprising a step of cooling aqueous urea that includes urea and triuret as an impurity to a temperature range of 17°C or less to 5°C or more to deposit triuret and make the aqueous urea cloudy, and a step of passing the aqueous urea through an ion exchange resin in said temperature range in a state where the aqueous urea is clouded, and allowing the ion exchange resin to capture the deposited triuret.

IPC Classes  ?

• C07C 273/14 - SeparationPurificationStabilisationUse of additives
• C07C 275/00 - Derivatives of urea, i.e. compounds containing any of the groups the nitrogen atoms not being part of nitro or nitroso groups

Abstract

Disclosed is an additive for trapping a halogen conveniently and at low cost in a conventional recycling apparatus without the need of attaching any specialized unit to the recycling apparatus. Specifically disclosed is a halogen trapping additive which comprises 100 parts by mass of a mixture composed of 49.5 to 75 parts by mass inclusive of urea, 20 to 49.5 parts by mass inclusive of a hydroxide of at least one member selected from calcium, magnesium and barium and 1 to 5 parts by mass inclusive of a stearic acid metal salt.  In the halogen trapping additive, the mixture preferably takes the form of powder having a particle size of 0.01 to 5 mm inclusive.

IPC Classes  ?

• C09K 3/00 - Materials not provided for elsewhere
• C08J 11/00 - Recovery or working-up of waste materials