Solid Acid-catalyzed Regioselective Nitration Of Toluene

Reaction yield and selectivity can be improved by using solid acid for the nitration ofaromatic compounds, which is arising green chemical technology. The solid super strong acidcatalyst of ZrO₂-TiO₂/SO₄^2- and phosphotungstic acid catalyst are prepared. Niobic acid isused as a new catalyst in toluene nitration. The effect of all kinds of factors just like differentatom ratios of catalyst, calcinations temperature, nitrated reaction time, temperature andrecovered catalyst, etc. on the regioselectivities of toluene in mononitration with thesecatalysts are researched. The results show that ZrO₂-TiO₂/SO₄^2-solid super strongacidindicates high regioselectivity, up to ortho-paro ratio (O/P) of 0.89 in product distribution oftoluene nitration, and gives a yield of 93.9％. While the yield is as high as 99.3％and o/p is1.26 with niobic acid catalyst. The O/P of the treated niobic acid is yet only 1.04, much lowerthan that of pure niobic acid. Phosphotungstic acid catalyst lists a yield of 93.9％with the O/Pof 1.11. The catalysts, which are easy to be prepared, can be reutilized up to five times withlittle decrease in activity and are convenient to be recovered to circulatory re-utilized. So theyare all new clean-nitrated reaction catalysts and will have vast prospects, especially the niobicacid.