Research On The Preparation Of 2,5-xylenol By Sulfonation And Alkali Fusion

2,5-Xylenol is the main raw material of synthetic gemfibrozil and2,3,6-trimethylphenol which is an important intermediate of vitamin E.In this paper,2,5-xylenol was synthesized by sulfonation and alkali fusion using p-xylene as the starting material.Some factors influencing the yield and purity of the product in the sulfonation and alkali fusion were systematically studied,and some refined methods of crude product were also studied.The large amounts of waste acid can be disposed by recycling and reusing the acidic filtrate in sulfonation,which can also cut down the utilization amount of NaOH and H₂SO₄,avoiding environmental pollution.In addition,it is cost-saving and benefit-increasing.The optimal sulfonation conditions:At room temperature,97%sulfuric acid was added to p-xylene slowly within 20min,the molar ratio of sulfuric acid and p-xylene 1.6:1,reaction temperature 125?,reaction time 2.0h,the pH of neutralization 7⁹.The molar yield of sodium 2,5-xylenesulfonate is 96.87%,and the purity is 99.30%.Wet sodium salt were used in the alkali fusion.By addition of sodium stearate and antioxidant,water vapor was input to the reactor,which reduced the overoxidation,and it was found that the flow of materials,the yield and purity of alkali fusion product were improved significantly.The optimal alkali fusion conditions:NaOH,KOH,wet sodium salt,antioxidant 1035 and sodium stearate were mixed into a reaction vessel of alkali fusion,the mass ratio of mixed alkali and sodium 2,5-xylenesulfonate 0.8:1,the mass ratio of NaOH and KOH 3:2,antioxidant1035 4g,sodium stearate 9g.The reaction temperature was raised to 330³40?after the feeding,reaction time 2.0h.Water vapor was input to the vessel during the reaction,the pH of acidification by using dilute sulphuric acid 5⁶.The molar yield of2,5-xylenol in the alkali fusion is 92.70%,and the purity is 91.33%.The refined methods of crude 2,5-xylenol include steam distillation,distillation under vacuum and recrystallization.The optimal refined method:Use mixed solvent of ethanol-water to refine crude.When the ratio of crude,ethanol and water?g:mL:mL?is 1:1:1.25,the refined yield is 70.17%,and the purity is 98.47%.