The Synthesis Process Of Naphthol AS-BI

Naphthol AS-BI is an important pigment intermediate, which is used to synthesize a new kind of high quality azo dyes.Naphthol AS-BI was obtained by reacting 2-hydroxy-3-naphthoic acid with 5-aminobenzimidazolone in the presence of dehydration agent. Three processes were studied in this thesis. In the first process using PCl3 as dehydration agent, the influence of reaction temperature and solvent on yield and purity were discussed. In the second process using triphenyl phosphate and pyridine as dehydration agent, the influence of reaction temperature and volume ratio of methanol/NMP on yield and purity were discussed. By the method of acyl chlorine, the influence of reactant molar ratio, the feeding time, reaction time, reaction temperature, reagent, catalyst and acid-binding agent were also studied. At the same time, the treatment of thionyl chloride tail gas, the solvent recovery and product purification were considered.The third method gives the best result. The optimum conditions of the synthesis of 2-hydroxy-3-naphthoyl chloride using chlorobenzene as solvent are as follows: molar ratio of thionyl chloride to 2-hydroxy-3-naphthoic acid is 1.1:1, the amount of DMF is 0.08ml, and reaction temperature is 45℃~50℃. The yield of 2-hydroxy-3-naphthoyl chloride is 97.3%; The optimum conditions of the section of synthesizing naphthol AS-BI using NMP as solvent are as follows: molar ratio of 2-hydroxy-3-naphthoyl chloride to 5-aminobenzimidazolone is 1.25:1, the feeding time is 1.5h, the reaction time is 4h , the reaction temperature is 20℃, and DMAP and Na2CO3 are selected as catalyst and acid-binding agent respectively. The yield of naphthol AS-BI is 91.0%, and HPLC purity is 99.3%. As the small-scale reaction succeeds, the technology will be put into production in Shandong Province.