Vapor-phase nitration of benzene over solid acid catalysts (1): Nitration with nitric oxide (NO2) Original Research Article

Vapor-phase nitration of benzene over acidic catalysts is expected to be a clean process with no sulfuric acid waste. We investigated this process over acidic catalysts utilizing nitric oxide (NO2) as a nitrating agent, and found that several mixed metal oxides, such as silica–alumina, zinc-oxide–titania, and tungsten-oxides–molybdenum-oxide, exhibited a fairly good activity. Among them, WO3–MoO3 is the most active, but this catalyst alone deviated from the linear relationship between the activity and acidity. In order to explain this discrepancy several factors, such as acid amount, acid strength, and BET surface area, are examined in detail.