Several new caprolactam-based Bronsted acidic ionic liquids [Caprolactam]X (X- = pTSO-, BSO-, BF4-, NO3-) with relatively lower cost and lower toxicity were synthesized and for the first time used in catalyzing organic reaction. They showed good catalytic activity in the nitration of toluene and chlorobenzene with HNO3/Ac2O under mild conditions. Among them, [Caprolactam]pTSO was the best one probably because of its better affinity to aromatics than the others. [Caprolactam]pTSO catalyzed the nitration of toluene with achieving a high yield (99.7%, calculated by quantitative GC) and better para-selectivity (ortho/para=1.03) than the traditional mixed acid methodology. And the catalyst can be recycled for four times.
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The solid catalysts of SO4 2-/TiO2, SO4 2-/TiO2-ZrO2, SO4 2-/WO3-ZrO2, and SO4 2-/MoO3-ZrO2 have been prepared and regioselectiveties of chlorobenzene minonitration on these catalysts were investigated. When the reaction was carried out at 30 C for 30 min, SO4 2-/TiO2-ZrO2(1:1) by a calcination step for 3 h at 550 C enhanced the para-selectivity of chlorobenzene nitration by using nitric acid as nitrating agent, up to an ortho-para isomer ratio 0.17 in product distribution of chlorobenzene mono- nitration, and the yield of chlorobenzene mononitration was 55%. The catalysts could be reutilized for four times with a little decrease in activity.
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