693 kg (6.728 kmol) of diethylenetriamine (DETA) was added to a 1 m3 stirred reactor equipped with a double jacket, a liquid feed device, a nitrogen inerting system, a reaction vessel, and a scrubber tower for recovery of ammonia and ammonia solution. The reaction system was warmed up to 130°C while nitrogen was introduced to remove oxygen from the DETA. When the temperature reached 130 °C, slow addition of a 40% aqueous urea solution totaling 671.4 kg (4.476 kmol) was initiated, resulting in a molar ratio of DETA to urea of 1.5:1. The addition of the urea solution continued for a period of 4 h in batches. The ammonia released immediately at the beginning of the reaction was recovered through a scrubbing tower, and the scrubbing solution and the aqueous ammonia solution were collected in a special container. After the addition was completed, the reaction mixture was kept at 130°C for 1.5 hours to ensure complete water removal. Subsequently, the reaction temperature was gradually increased: first to 140 °C in 45 min and held for 45 min, then to 150 °C and held for 45 min, and finally at 160 °C for 5 h. The reaction temperature was then increased to 140 °C in 45 min and held for 45 min. At the end of the reaction, the system was cooled to 125 °C and the excess DETA was removed by distillation under a reduced pressure of 10 to 1.5 mbar and a mild nitrogen stream, a process that did not take more than 5 hours. After restoring the system to atmospheric pressure, it was cooled to 60 °C and the product was removed from the reactor. The resulting product contained 95-96% of 1-(2-aminoethyl)-2-imidazolidinone (UDETA) and 1-2.5% of tetraethyleneurea (TETU).
