Study On Selective Nitration Of Tuluene On Solid Acid And Acidic Ionic Liquid Catalysts

Using solid acids and ionic liquids as catalysts in organic synthesis was one of the important research fields in chemistry and chemical engineering.By adding suitable solid acids and ionic liquids as catalyst in reaction systems,the reaction yield and selectivity could be improved.Nitration of toluene was one of the most important fine organic synthesis reactions,Using solid acids and acidic ionic liquids for the nitration of aromatic compounds was one of the technologies for rising green chemical synthesis.The industrial nitration of toluene to synthesize p-mononitrotoluene(p-MNT) involving the concentrated mineral acids as the catalyst which is one of the most environmentally harmful processes.The process produces huge amounts of wastes along with a large amount of undesired o-MNT due to the nonselective nitration of toluene.Catalysis affect of solid acid and acidic ionic liquids on nitration of toluene were discussed.The main works and results were as follows:(1)The nitration of toluene catalyzed by Solid niobic acid catalyst and its modifiers was studied.Higher regioselectivy of toluene in mononitration in the Presence of all kinds of modified niobic acid than unmodified one,and the positive correlation of its acid strength and catalytic activity were discovered.(2)The regioselective nitration of toluene with ZrO₂-TiO₂/SO₄^2- solid acid catalysts was investigated.The effect of all kinds of factors,just like calcinations temperature,dosage of catalyst,atom ratio of Zr and Ti,nitrated reaction conditions and recovered of catalyst,etc.on the regioselectivities of toluene in mononitration were researched and the best nitration condition was established.(3)Effects of different kinds of catalysts with Keggin structure on nitration of toluene were studied.It was found that,in the same condition,catalytic activity of heteropolyacids accords with its acid strength,that is phosphotungstic acid＞silicotungstic acid＞phosphomolybdic acid.(4)Utilizing acidic solt catalysts-sodium bisulfate,sodium dihydrogen phosphate, and potassium dihydrogen phosphate as catalyst of nitration of toluene,the effect of dosage of catalyst,nitrated reaction time and temperature and recovered of catalyst, etc.on the regioselectivities of the nitration of toluene were researched,and the satisfactory result was acquired.(5)Using new acidic ionic liquids catalysts-HNIL·NO₃^-and HNIL·HSO₄^-for the nitration of aromatic compounds had a good effect.Especially catalytic activity of HNIL·HSO₄^-acidic ionic liquids heightened greatly,due to the still stronger acidity of it.(6)These catalysts were characterized by means of modern analyses.It was found that the selectivity and yield of toluene nitration were evidently enhanced,The ortho-para-isomer ratios,in product distribution of toluene mononitration and yield were varied in range from 0.88 to 1.20 and from 82.5%to 100%on above-mentioned solid acids and ionic liquids catalysts.(7)The mechanism of selective nitration of toluene on solid acids and acidic ionic liquids was researched.The total reaction could be explained by two steps.The first was a fast pre-equilibrium,activation nitrating reagent transferred to the catalyst. The second step was slow and rate-determining,activation nitrating reagent bonded on catalysis with reactant and the object product was gained.