Effects of regeneration of ZSM-5 based catalysts on light olefins production in n-pentane catalytic cracking

- The regenerated ZSM-5 catalysts promoted the selectivity to light olefins.
- Promotion on light olefins formation was enhanced by increasing the regeneration cycles.
- The energetic demanding for CC/CH bond breaking over B acid sites, oxidized sites, and Ag sites was different.
- Changes of the active sites significantly influenced light olefins formation.

In this paper, effects of regeneration of the parent and Ag-incorporated ZSM-5 based catalysts on light olefins production in n-pentane catalytic cracking were systematically investigated. Experiment results revealed that the regenerated catalysts significantly promoted the selectivity to light olefins, and this promotion can be further enhanced by increasing the regeneration cycles, and the highest selectivity to light olefins (69 wt%) was achieved over the regenerated Ag-ZSM-5 catalysts that was 25% higher compared to the parent ZSM-5 zeolites (55 wt%). Furthermore, it was found that B acid sites, redox sites, and Ag sites can trigger the scission of CC/CH bonds, and the energetic demanding over the active sites was in a descending order. The high-temperature regeneration treatment resulted in a decrease of B acid sites, a generation of redox sites, and a redistribution of existence states of silver sites. Perhaps, that is the reason why the high-temperature regeneration of ZSM-5 based catalysts significantly influenced the light olefins formation as well as the product distribution in n-pentane catalytic cracking.

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