Efficient and selective nitration of xylenes over MoO3/SiO2 supported phosphoric acid

Silica supported molybdenum oxide modified with phosphoric acid (P/Mo/SiO2) is a very active solid acid catalyst in ortho-xylene nitration. At room temperature and with a small excess of fuming nitric acid, ortho-xylene conversion is 79 wt%. In nitration with 65% HNO3 at 80 °C and with fivefold molar excess of acid, almost complete ortho-xylene conversion is achieved. The P/Mo/SiO2 is also an excellent catalyst for nitration in the continuous process with using 65% HNO3 under solventless conditions. Hence, the process is eco-friendly, cheaper and leads to 60 wt% of selectivity to 4-nitro-ortho-xylene with ca. 90 wt% conversion for long time.