NOVELTY - Synthesis and purification of 4-chlorobutyryl chloride includes adding gamma -butyrolactone and mixed catalyst into reactor, adding thionyl chloride, heating, and incubating to carry out acylation reaction; vacuum-distilling, cooling, and collecting supernatant; pumping into crude distillation kettle, vacuum-distilling to obtain thionyl chloride and 4-chlorobutyryl chloride; pumping crude 4-chlorobutyryl chloride into distillation kettle, vacuum-distilling to obtain 4-chlorobutyryl chloride; and testing 4-chlorobutyryl chloride purity, single impurity and yield.    USE - Method for synthesis and purification of 4-chlorobutyryl chloride (claimed).    ADVANTAGE - The method is simple and environmental-friendly, and it has convenient operation, high product yield and purity, and nearly no wastes are discharge.    DETAILED DESCRIPTION - Synthesis and purification of 4-chlorobutyryl chloride comprises:    (A) adding gamma -butyrolactone and mixed catalyst into reactor, stirring, water cooling reactor, slowly adding thionyl chloride, slowly heating to 50-80 degrees C, and incubating for 5-7 hours to carry out acylation reaction; and vacuum-distilling to remove excess thionyl chloride, cooling to room temperature for 8-10 hours to precipitate, collecting supernatant and recycling catalyst lower layer;    (B) pumping supernatant into crude distillation kettle, vacuum-distilling at - 0.095 MPa to - 0.1 MPa to obtain thionyl chloride and 4-chlorobutyryl chloride 50 degrees C fraction, crude 4-chlorobutyryl chloride 50-110 degrees C fraction and 4-chloroprene chloride and organic waste remaining tailings;    (C) pumping crude 4-chlorobutyryl chloride into distillation kettle, vacuum-distilling to - 0.1 MPa while controlling reflux ratio to 1:2 to obtain 4-chlorobutyryl chloride 78-82 degrees C distillate and 4-chlorobutyryl chloride and organic waste remaining tailings; and testing 4-chlorobutyryl chloride purity to greater than or equal to 99%, single impurity to less than 0.30% and yield to greater than or equal to 90%; and    (D) adding generated 4-chloroprene chloride with sulfur dioxide, reacting, adding lye to carry out absorption of sodium sulfate, distilling to obtain tailings, reacting with anhydrous methanol to obtain methyl-4-chlorobutyrate, and absorbing gas with 30 wt.% hydrochloric acid.    The ratio of gamma -butyrolactone, mixed catalyst and thionyl chloride is 1:0.03-0.07:1.5-2.5. The mixed catalyst comprises copper oxide and zinc oxide at molar ratio of 1:3-5, and 98% concentrated sulfuric acid. The molar ratio of concentrated sulfuric acid and copper oxide and zinc oxide mixture is 1.2-1.6:1. The mass ratio of tailings and anhydrous methanol is 1:0.18-0.4.