Improving effect of Fe additive on the catalytic stability of Mo/HZSM-5 in the methane dehydroaromatization

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• 作者：Yuebing Xu^a ; ^b ; Jide Wang^a ; Yoshizo Suzuki^b ; Zhan-Guo Zhang^b ; ^{z.zhang@aist.go.jp}
• 关键词：Methane dehydroaromatization ; Mo/HZSM-5 ; Metal additives ; Carbon nanotube
• 刊名：Catalysis Today
• 出版年：2012
• 出版时间：20 May, 2012
• 年：2012
• 卷：185
• 期：1
• 页码：41-46
• 全文大小：783 K

文摘

The promotional effects of eight kinds of transition metal additives (0.5 wt % ) on the activity and stability of 5 wt % Mo/HZSM-5 were screened at 1073 K and 10,000 mL/g/h in a continuous CH₄ feed mode. Only Fe was observed to improve the activity stability. Subsequently, confirmation tests were performed with other three Fe-modified catalysts containing 0.3, 1.0 and 2.0 wt % of Fe in the same continuous operation mode and also with the 0.5 wt % Fe-5 wt % Mo/HZSM-5 under periodic CH₄-H₂ switch operation for 1650 min. It was confirmed that Fe indeed enhanced the stability of Mo/HZSM-5 catalyst. Then, TPO, TG and BET measurements and SEM observations were performed for almost all spent samples to gain insight into the promotion mechanism of Fe additive. The results revealed that over short time frames in the continuous CH₄ feed mode the formation of Fe-induced carbon nanotubes is the origin of its promotional effect, while under the long-term periodic CH₄-H₂ switch operation the catalytic involvement of Fe in the surface coke removal during the H₂ flow periods is the main cause of Fe-modified catalyst being much more stable than the unmodified Mo/HZSM-5 catalyst