Study On Solid Superacid For Nitration In Preparation Of M-Trifluoromethylphenol

Using solid superacids as catalysts in organic synthesis was one of theimportant research fields in chemistry and chemical engineering. By addingright solid acid as catalyst in reaction systems the reaction yield andselectivity could be improved. Nitration of aromatic compounds was one ofthe most important reactions and widely studied in fine organic synthesisreactions and industry still relies upon early technology involving mixturesof nitric acid and sulfuric acid. Howerer, there were many disadvantages:corrosive, hard to separate, causing pollution and so on. Nitration ofbenzotrifluoride with solid superacids was an important trend in thedevelopment of nitration.In this paper, nitration of benzotrifluoride with solid superacids wasstudied and many factors that affect nitration of benzotrifluorede wereinvestigated, the catalyst was characterized by NH₃-TPD. The results showthat SO₄^2-/ZRO₂ had better catalytic activities. The optimal preparationcondions of catalyst was: The concentration of sulfuric acid is lmol/L, theimpregnation time is 0.5h, the advance calcined temperature is 350℃, thecalcined temperature is 650℃, the calcined time is 3h, the size of catalyst is ＞120. The technological conditions of nitration are that reactiontemperature 65℃, the dosage of benzotrifluoride is 14.6g, the mol ratiobetween fuming nitric acid and benzotrifluoride is 1.5:1, choosing 50mlCCl₄ as solvent and 7ml acetic anhydride asdesiccant, m(SO₄^2-/ZrO₂): m(benzotrifluoride)=1:5, the reaction time is5h, the yield of m-nitrotrifluorobenzene is 56.4ï¼…. The preparation ofm-trifluoromethylphenol with m-nitrotrifluorobenzene throughhydrogenation,diazotization and hydrolyzation was mentioned. Thepreferable conditions are that hydrogenation temperature 45℃, the pressureis 1.5 MPa, 50ml methanol, m(Pd-C): m(m-nitrotrifluorobenzene)=1: 70, thespeed of reaction and the yield of m-trifluoromethylaniline is no morechange when the catalyst is used 5 times. In the diazotization and thehydrolyzation, the concentration of sulfated acid is 60ï¼…, the diazotizationtemperature is 15℃.