Patent ID: 9656983
Date: 2017-05-23
CPC Classifications: C07C,C07D

Claim:
1. A process for preparing carboxylic acids and/or carboxylic anhydrides by gas phase oxidation of aromatic hydrocarbons selected from the group consisting of benzene, xylenes, naphthalene, toluene, durene, and combinations thereof, the process comprising: passing a gas stream comprising at least one aromatic hydrocarbon selected from the group consisting of benzene, xylenes, naphthalene, toluene, and durene, and molecular oxygen continuously over a catalyst thermostatted by a heat carrier medium in a reactor, during startup of the reactor, lowering the temperature of the heat carrier medium from a temperature in the range from 380 to 410° C. to a temperature in the range of 340 to 365° C., maintaining the temperature of the heat carrier medium constant by pausing the lowering of the temperature for at least 24 hours during the startup of the reactor, during which neither the loading of the gas stream with hydrocarbons nor the gas stream volume is increased by more than 3%.