Abstract: XRD, IR and chemical analysis were applied to the investigation of a decline in catalyst activity of an acrylonitrile unit. It was found that an exceeding reduction of the key element Fe3+ in acrylonitrile catalyst and the changes of catalyst structure during the process were the main causes of catalyst deactivation. Lab test results showed that the acrylonitrile yield could be increased significantly by applying ex-situ regeneration of the used catalyst, the acrylonitrile yield of catalyst prior and post to regeneration was 76.11% and 81.62%, respectively. In commercial unit, adopting partial substitution of used catalyst by regenerated catalyst, the acrylonitrile yield of catalyst prior and post to partial substitution was 75.01% and 78.82%, respectively, which indicated that a 3.81 percentages increase of yield was obtained.

Key words: acrylonitrile, ammoxidation, catalyst, reactivation, reduction rate