Study On The Synthesis Of 4-Chlorophthalic Anhydride Using The Method Of D-A Cyclization And Aromatization

4-chlorophthalic anhydride can be used as raw material of polyimide engineering plastic, intermediate in the production of medicine, pesticide and dye, and also can be used as raw material for the production of the plant growth modifier and high-powered plasticizer. 4-chlorophthalic anhydride has a simple structure, however, there are big difficulties in the production, either costly raw material source or the refine of the products hindering the development of the product.To search for an efficient synthesis route of 4-Chlorophthalic Anhydride, study was carried out to investigate the synthesis of 4-chlorotetrahydrophthalic anhydride(acid) and it's aromatic process on the basis of Diels-Alde Cyclization and aromatic process of haltetrahydrophthalic anhydride, so that we can get the product with more yield and purity.First, two routes of D-A Cyclization for the synthesis of 4-chlorotetrahydrophthalic anhydride(acid) was studied. One of the routes was using acetylene as raw material. First, we got vinyl acetylene, and then added HCl, so we got chloroprene. Finally, chloroprene and maleic anhydride cyclized to 4-chlorotetrahydrophthalic anhydride, the yield was 95% and the purity was more than 98%; the other routes was using the maleic anhydride and 1,3-butadiene as raw material to synthesize the tetrahydrophthalic anhydride, and then tetrahydrophthalic anhydride was chloridized to get 4-chlorotetrahydrophthalic acid(anhydride). The yield of tetrahydrophthalic anhydride was 96%,and the purity was more than 98%.In the process of the chlorination, the yield of 4-chlorotetrahydrophthalic acid was 28%, purity was more than 98%.Then, two routes of aromatize 4-chlorotetrahydrophthalic anhydride(acid) was compared and optimized. The first route was using the liquid bromine to aromatize the 4-chlorotetrahydrophthalic anhydride to 4-chlorophthalic anhydride, The yield was 89%,and the purity was more than 99%. The second routes was using the oxygen and activated carbon to aromatize the 4-chlorotetrahydrophthalic acid to 4-chlorophthalic acid, and to 4-chlorophthalic anhydride from dehydration.The reaction yield increased to 70%, purity 100%.