Titanium species in deactivated HTS-1 zeolite from industrial cyclohexanone ammoxidation process

• The structure and framework Ti content of both HTS-1 zeolites are almost the same.
• There are more “patches” that could be observed on the deactivated zeolite particles.
• The core–shell structure of TiO2 was observed from deactivated HTS-1 zeolite.

The types of titanium species and contents in commercialized hollow titanium silicalite (HTS-1) zeolite are essentially related to their ammoxidation performance. XRD and combined TEM methods were used in this study to identify the titanium species in the deactivated HTS-1 zeolite discharged from cyclohexanone ammoxidation unit. Core–shell structure of crystalline–amorphous TiO2 was observed for the first time in the deactivated HTS-1 zeolite. The results of their catalytic activities in phenol hydroxylation are in line with the analysis. This study provided valuable information to understand the deactivation mechanism of HTS-1 zeolite in cyclohexanone ammoxidation.