(582bu) One Preparation Method of High Aluminium-Content Sulfated Zirconia: The Influence of Aluminum Contents and Washing on the Structural Morphology, Acidity and Reactivity

One Preparation Method of High Aluminium-content
Sulfated Zirconia: the Influence of Aluminum Contents and Washing On the Structural
Morphology, Acidity and Reactivity

Zhiming Ma,
Li Shi^*

Institute of Petroleum Processing, East
China University
of Science and Technology, Shanghai 200237, People¡¯s Republic of China

A
high aluminum-content sulfated zirconia has been prepared by kneading method,
and washing process has been considered as a key factor. Catalysts were
characterized by XRD, BET, SEM, FT-IR, pyridine-IR, NH₃-TPD, H₂-TPR,
²⁷Al-NMR, and the reactivity was evaluated by n-hexane
isomerization. Compared with coprecipitation method, the high aluminum-content
sulfated zirconia by kneading method showed a better tetragonal zirconia
crystal shape and higher surface area. Besides, the aluminum content could
influence the crystal form, catalyst structure and acidity obviously, as well
as the anchoring effect on the labile sulfates. Actually, the more the aluminum
content was, the more sulfates would be left in the catalyst samples even after
washing. The O-H and S=O stretching vibration would be shifted in the existence
of aluminum or water. The high aluminum-content sulfated zirconia showed an excellent
reactivity in the n-hexane isomerization, even at a lower reaction temperature 423K,
the Conversion rate is up to 92%, and the selectivity of 2,2-DMB is 40%. What¡¯s
more, washing with water has an obviously effect on the reactivity. With the
support of aluminum coordination state, the hydrolysis model has been deduced
for different aluminum contents of the catalysts, and it can explain the
formation of more Brønsted acid sites and Al-O-S bands.

Keywords:
sulfated zirconia; aluminum promoter; hydrolysis
model