Study On Synthesis And Purification Of Developer Dihydroxydiphenylsulfone

The synthesis and purification of dihydroxydiphenylsulfone, which is a color developer for thermal printing sheet, were studied in this paper. 2,4′-Dihydroxy -diphenylsulfone and 4,4′-dihydroxydiphenylsulfone are the primary products synthesized. 2,4′-Dihydroxydiphenylsulfone was prepared from phenol and H2SO4. The synthesis of 2,4′-dihydroxydiphenylsulfone with phosphoric acid, phosphorous acid, hypophosphorous, phosphoric anhydride, 1,3-benzenedisulfonic acid, p-toluene -sulfonic acid as catalysts using mesitylene and o-dichlorobenzene as solvent was studied in detailed. The effects of catalyst type, catalyst amount, mole ratio of phenol to sulfuric acid, reflux reaction time, solvent amount, and addition method of H2SO4 on the preparation of 2,4′-dihydroxydiphenylsulfone were investigated. The optimum conditions were obtained. Moreover, the synthesis of 2,4′-dihydroxydiphenylsulfone using pseudocumene and toluene dichloride as solvent was also undergone, which reduced the production cost and improved economy profit. Toluene dichloride was determined as solvent and the optimum reaction conditions. The main results were as follows:mole ratio of n (phenol):n (H2SO4 ) = 2.62:1; toluene dichloride 200g; addition time of H2SO4 2h at temperature 130℃; reflux time 3h. The content of 2, 4′-dihydroxydiphenylsulfone was 32.73% in the mixed product synthesized and the total yield was 88.7% (based on H2SO4). Purification process of 2,4′-dihydroxydiphenylsulfone in solvents was also investigated. The solvents used in this paper were: (1) methanol-o-dichlorobenzene mixed solvent and alkaline aqueous; (2) methanol-o-dichlorobenzene mixed solvent and methanol-water; (3) methanol-o-dichlorobenzene mixed solvent and methanol -acetone-water. The better purification conditions were as follows:2.5%(wt) methanol-o-dichlorobenzene,methanol:acetone:water = 25%:5%:70% (wt). the total yield was 23.5% and the content of 2,4′-dihydroxydiphenylsulfone was higher than 95.0%. It can reach the need for color developer for thermal printing sheet. 4,4′-Dihydroxydiphenylsulfone was refined by alkaline aqueous of 1.5% NaOH. The purity up to 99.15% and total yield of 72.7% were obtained. The process mentioned above has good prospects in industrialization.