长期高温水热处理对ZSM-5分子筛催化剂性能的影响

Effect of Long-Term Hydrothermal Treatment on Performances of ZSM-5 Based Catalyst

制备了ZSM-5分子筛催化剂,将初始催化剂(Cat-0)先在700℃下水热处理4 h获得催化剂Cat-4,再于600℃下继续进行不同时间的水热处理,处理300 h获得的催化剂为Cat-300;采用NH3-TPD和27Al MAS NMR方法对经不同时间水热处理的催化剂进行表征,考察了Cat-4和Cat-300裂解石脑油的性能,以考察长期处于高温水热条件下ZSM-5分子筛催化剂性能的变化。实验结果表明,Cat-4的NH3-TPD酸量比Cat-0降低约70%,骨架铝含量从16.9%降至11.7%,非骨架铝含量从0.4%增至5.5%;Cat-300的酸量与Cat-4相比变化不明显,Cat-300的骨架铝含量比Cat-0降低62%,但骨架铝和非骨架铝含量之和基本不变;Cat-4和Cat-300裂解石脑油时,二者的裂解能力接近。长期处于高温水热条件下,ZSM-5分子筛的骨架结构虽然有所变化,但对其裂解石脑油能力的影响不大。

A series of ZSM-5 based catalysts were prepared through hydrothermal treatment and were characterized by means of NH3-TPD and 27 Al MAS NMR,in which Cat-4 was prepared from an original catalyst Cat-0 by the hydrothermal treatment with vapor at 700 ℃ for 4 h and Cat-300 was prepared from Cat-4 by the hydrothermal treatment with vapor at 600 ℃ for 300 h. Cat-4 and Cat-300 were used in the catalytic cracking of naphtha,separately. It was found that,compared with Cat-0,the NH3-TPD acid amount of Cat-4 lost about 70%,the framework Al content decreased from 16.9%to 11.7% and non-framework Al content increased from 0.4% to 5.5%. Compared with Cat-4,the acid amount of Cat-300 changed a little,the framework Al content deceased by 62%,but the total content of framework Al and non-framework Al was almost unchanged. The activity of Cat-4 in the catalytic cracking of naphtha was nearly the same as that of Cat-300. The investigation results showed that the catalyst activity changed little when the framework of the ZSM-5 zeolite in the catalysts was changed by the long-term hydrothermal treatment.