Abstract
HZSM-5 (HZ) zeolite co-modified with Zn and second promoters (Zr, Ce, Mo and Cr) was synthesized and the aromatization of methanol over the modified HZ in a fixed-bed reactor was investigated. The results of catalytic tests revealed that the methanol conversion and yield of benzene, toluene, and xylene (BTX) over the Cr, Zn comodification HZ (CrZn/HZ) were higher than that over ZrZn/HZ, CeZn/HZ, and MoZn/HZ. The catalysts were characterized by XRD, SEM, TEM, XPS, N2 isothermal adsorption-desorption and NH3-TPD. The results suggest that Zn species exist in two forms in the HZ zeolite. One is ZnO particle, the other one is ZnOH+, which significantly improveds the yield of BTX. Furthermore, the Cr species on the external surface promoted the dispersion of ZnO, increased the amount of ZnOH+, which further improved the yield of BTX. In addition, the optimal Cr2Zn1/HZ catalyst exhibited better catalytic performance and prolonged lifetime of reaction.
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