Performance of HZSM-5 prepared by different methods for methanol to aromatics.

Nanoscale polymer spherical and hollow structure HZSM-5 zeolites are prepared by hydrothermal and desilication–recrystallization methods. In addition, the crystallite size of two types of HZSM-5 can be easily controlled by changing H₂O/Si mole ratio. The hollow structure HZSM-5 zeolite is formed, it is due to the 010 crystal plane is the most energetically favorable orientation in silicalite-1 and the Si species is first removed on this crystal plane. The properties of different morphology zeolites were characterized by means of XRD, SEM, TEM, NH₃-TPD, N₂ isothermal adsorption–desorption and TG, and the catalytic performance of these two types of HZSM-5 in MTA reaction was investigated in a fixed-bed differential reactor. The results showed that the multilevel pore structure and suitable acid strength and more acid density were obtained in the hollow structure HZSM-5 zeolite. Therefore, the hollow HZSM-5 zeolite exhibited that higher catalytic lifetime and selectivity of aromatics than nanoscale polymer spherical HZSM-5 zeolite in MTA reaction. Furthermore, the Al distribution on the 010 crystal plane may change slightly during the process of fabricating hollow mesoporous, which leads to higher selectivity of p-xylene over hollow HZSM-5 than nanoscale polymer spherical HZSM-5 zeolite. [ABSTRACT FROM AUTHOR]