AlPO
4 which was prepared by neutralization of an aqueous solution of Al nitrate was amorphous and has a large specific surface area as much as 130 m
2/g after calcination at 1000°C. After the calcination at 1100°C, AlPO
4 was slightly crystallized and the crystallite size of AlPO
4 was about 16 nm and the catalytic activity was higher than that calcined at 1000°C. But AlPO
4 calcined at 1200°C was more crystallized and the activity was decreased. On one hand, AlPO
4 promoted by 10 mol% of Ce which was calcined at 1000°C showed a maximum catalytic activity and crystallinity was the same as that of pure AlPO
4 calcined at 1100°C. Ce promoted AlPO
4 after calcination at 1100°C was well crystallized, and the catalytic activity was decreased.
Therefore, it was concluded that Ce as a promoter, creates small AlPO
4 particles which was conveniently crystallized to CCl
2F
2 decomposition by the calcination at 1000°C which is 100°C lower than that in case of pure AlPO
4.
By treatment with concentrated CCl
2F
2 at high temperatures such as 800 or 900°C for 8 h, both AlPO
4 and Ce promoted catalysts were much crystallized and SSA and the catalytic activity of the catalysts were decreased. The catalytic activity when it will be ultimately inactivated state was estimated using
T50% approached at zero SSA, and 550°C will be required to obtain 100% CCl
2F
2 conversion for Ce promoted AlPO
4 catalyst.
AlPO
4 was crystallized by a steam treatment at 900°C to the same level of that calcined at 1100°C in air and increased the catalytic activity. In case of Ce promoted AlPO
4, steam treatment at 1000°C promoted the crystallization of CePO
4 but AlPO
4 and increased the catalytic activity.
The effects of CCl
4, CF
4, and CCl
2F
2 treatment were studied and found that AlPO
4 was the most crystallized by the treatment by CCl
2F
2. This may be explained by the formation of chloridefluorides such as AlCl
3–nF
n and PCl
5-mF
m which can be sublimated only in the decomposition of CCl
2F
2.
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