Abstract A series of HZSM��5 membranes on the inner surface of stainless steel tubes with different Si/Al ratio were synthesized by secondary growth technique and used for catalytic cracking of supercritical ��n-dodecane. The surface properties of membranes were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (in-situ�� FT-IR). With the increase of Si/Al ratio, the HZSM-5 crystals were gradually cross��linked and the amount of Br�insted sites decreased. The sample with low Si/Al ratio gave a rapid decrease in the conversion of n-dodecane at the beginning of the reaction because of the high density of acid sites. An increase in the Si/Al ratio can delay the deactivation of the membranes, resulting in the significant improvement of the catalytic activity. But, the excess increase in the Si/Al ratio caused the decrease in the amount of acid sites and the increase in the density of the zeolite layer on the supports, which is unfavorable for the activity of membranes. The sample with Si/Al ratio of 125 gave the highest catalytic activity and initial stability.����
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Cite this article:
WANG Ying, LIU Guo-Zhu, CHEN Chen, WANG Li.Influence of Si/Al Ratio on Catalytic Cracking of n-Dodecane over HZSM-5 Membranes[J] Chemcial Industry and Engineering, 2012,V29(5): 1-5
2012, Vol. 29 
