| 摘要 |
<p>Toluene is prepared by the catalytic hydrogenation of phthalic acid or anhydride using a temperature of 300-450 DEG C., an excess of hydrogen under a pressure of at least 100 atmospheres and a catalyst comprising an oxide or sulphide of vanadium, tungsten or molybdenum. The amount of hydrogen may be up to five times that theoretically necessary. According to the example, phthalic anhydride mixed with a five-fold excess of hydrogen and preferably preheated is pumped under a pressure of 200 atmospheres through molybdic acid deposited on clay pellets maintained at a temperature of 375 DEG C. Toluene and water are removed from the products by cooling and the residual gas returned to the system. To reactivate the catalyst, it is heated to about 500 DEG C. to oxidise the carbonaceous deposits and the residue reduced in hydrogen at 400-450 DEG C. Specification 314,035, [Class 2 (iii)], is referred to.</p> |
