Continuous-flow nitration of aromatic compounds catalyzed
by a
well-optimized solid acid catalyst with aqueous nitric acid under
liquid phase was investigated. Using a suitable packed bed reactor
system furnishing precolumn, the desired flow reaction proceeded to
afford a nitroarene in a good yield by adopting Mo(VI)-supported TiO2–ZrO2 mixed-metal oxide. Further investigations
toward enhancement on catalytic performance at higher weight hourly
space velocity (WHSV) indicated that the mixed-metal oxide prepared
by sol–gel method with calcination at 700 °C presented
higher performances at 4.0 h–1 WHSV, and more than
90% yield was achieved. The turnover of the catalyst in long-term
operation studies revealed that 87% yield was maintained when ca.
43-fold amount of toluene was delivered to the catalyst (g/g). A wide
variety of aromatic compounds including both liquid and solid substances
were enabled to convert into the corresponding nitroarene compounds
by utilizing the developed system.
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