Study Of Synthesis UV-absorbers Of Benzophenone And Their Separation And Purification

2,2'-dihydroxy-4,4'-dimethoxy-benzophenone, a kind of important UV-absorbers, has attracted great interest among researchers for its numerous applications. In synthesis of BP-6, we chose triphosgene as a substitute for phosgene out of the consideration of cost on raw materials and the latter's toxicity. How to promote the conversion of triphosgene and the yield of BP-6 is a key factor in industrial process. Therefore, the related research of separation and purification of products in the non-phosgene synthesis of BP-6 was made in this thesis.Various Lewis acid catalysts were used in this reaction and it is found that AlCl3 showed good catalytic activity and selectivity in synthesis of BP-6. Using AlCl3 as catalyst, the experimental conditions such as catalyst concentration, reactant ratio, the temperature before and after feeding gas were optimized. When the reaction was carried out under the following conditions ,30℃before charging gas and 80℃after, catalyst concentration 45%(wt), the yield of BP-6 reached up to 45.2%.The composition of raw products was firstly analyzed according to the physico- chemical properties to determine the following purification procedure. Most of impurities with low boiling point could be separated by distillation under reduced pressure, then pure BP-6 could be obtained by recrystallization from hot ethanol. Secondly, the selection of solvents in the recrystallization of BP-6 was studied. It was found that ethanol was the optimal solvent, the solubility of BP-6 in ethanol changed little when the recrystallization temperature was varied from 5.0℃to 15.0℃. The highest yield of BP-6 89.0% was obtained when the recrystallization temperature was 15.0℃. It was also found that less amount of mixed solvent which composed of ethyl acetate and ethanol was required to get the same amount of BP-6, compared with the one solvent.