不同分子筛前驱体对γ-氧化铝改性的影响

Effect of different zeolite precursors on modification of γ-Al_2O_3

用炭黑扩孔的方法制备出孔径较大的γ-Al2O3载体,然后用不同的ZSM-5分子筛前驱体对其进行表面改性。考察晶化时间、硅硼比等对ZSM-5分子筛前驱体的影响;采用XRD、IR、Py-IR和BET等手段对改性前后载体的酸性、孔结构等表面性质进行表征。结果表明:经过扩孔和ZSM-5分子筛前驱体改性后的γ-Al2O3载体的平均孔径由扩孔前的6.9 nm增加到9.0 nm左右,孔径分布中大于10 nm的孔有所增加;ZSM-5前驱体改性后不会导致γ-Al2O3载体的堵孔;载体的酸性增强并出现一定的B酸位。

The γ-Al2O3 carrier with larger pore diameter was prepared by using carbon black method, and the surface was modified with different ZSM-5 zeolite precursors. The influences of crystallization time, the ratio of Si and B on ZSM-5 zeolite precursors were also examined. The samples were characterized by XRD, IR, Py-IR and BET analytical techniques to exam- ine the surface property such as the acidity, pore structure. The results show that the γ-Al2O3 supports after pore enlargement and modification with ZSM-5 zeolite precursors have an average pore diameter of 9. 0 nm compared with 6. 9 nm before pore enlargement. There are more pores being larger than 10 nm in pore size distribution. The zeolite precursors would not block up the pores of γ-Al2O3 carrier. The acidity of carrier modified by ZSM-5 zeolite precursors is significantly enhanced and cer- tain Broensted acid sites emerge.