PURPOSE: To prepare the titled compound useful as a synthetic intermediate of the raw material of pharmaceuticals, etc., in high yield and efficiency, using a low-cost chlorinating agent, by reacting a molten alkanolamine salt with hydrogen chloride as a chlorinating agent while removing water from the system.

CONSTITUTION: The objective compound is prepared by (1) reacting an alkanolamine with hydrochloric acid to obtain molten alkanolamine hydrochloride (DAAE.HCl) and (2) introducing hydrogen chloride into the molten DAAE.HCl at a rate of 0.05W0.5mol/Hr based on 1mol of DAAE.HCl at 140W150°C for 35W40hr while removing water from the reaction system. The unreacted hydrogen chloride is reused after dehydration or recovered as hydrochloric acid by dissolving in water.

EFFECT: The objective compound can be prepared easily with simplified apparatus and operations, and the unreacted hydrogen chloride can be reused as it is to the reaction.

USE: A starch modifier, etc.