The invention discloses a method for preparing 11-bromo-undecanoic acid by direct freezing
crystallization and a device for preparing 11-bromo-undecanoic acid, and relates to a method for preparing the 11-bromo-undecanoic acid. The preparation device comprises a burdening kettle, an addition
tower, a
crystallization kettle and a
filter press, wherein the burdening kettle is connected with the addition
tower; the addition
tower is connected with the
crystallization kettle; the crystallization kettle is connected with the
filter press; and the
filter press is connected with the top part of the burdening kettle. During work, the preparation method comprises the steps of: mixing
undecylenic acid and
toluene in a
mass ratio of 1:(3-4) at a temperature of -5-0 DEG C in the burdening kettle; allowing the mixed liquid with
hydrogen bromide in a
mole ratio of 1:1.05 at a temperature of 0-30 DEGC in the addition tower to react so as to generate an addition liquid; putting the addition liquid in the crystallization kettle, carrying out freezing crystallization at a temperature of -4 DEG C to -16 DEG C, a revolving speed of 8 round / min and a vacuum degree of -0.02MPa to -0.03MPa; and filtering
crystal in the filter press. The device disclosed by the invention has the advantages of a simple structure, strong continuity and
operability and is suitable for industrial production. The preparation method has the advantages of a short process flow, constant reaction, high product purity and good
economic benefits.