Method for refining piperazine

The invention discloses a method for refining piperazine, which comprises the following steps of: adding piperazine reaction liquid in a tower of a rectifying column for heating separation; heating the reaction liquid in the tower to 130 DEG C-140 DEG C, controlling the reflux ratio to be 0.2-1:1, collecting 100 DEG C fractional water; continuing to heat to 140 DEG C -150 DEG C, controlling reflux ratio to be 2-5:1, collecting 119 DEG C fractional ethylene diamine; continuing to heat to 160 DEG C -170 DEG C, pumping an extraction agent into the rectifying column from an extraction agent inlet at the upper part of the rectifying column by using a microinfusion pump when the scale of a thermometer shows 140 DEG C, wherein the extraction agent is one of dihydric alcohol or triatomic alcohol of C2-C5; and controlling the reflux ratio to be 3-5:1, controlling the ratio of addition mass of the extraction agent per minute to extraction mass of piperazine per minute to be 0.05-0.2:1, and collecting 148 DEG C fractional piperazine which is pure piperazine. The method can improve the purity of the product and the separation efficiency and also can greatly reduce production cost since the extraction agent can be reused after being separated simply.