B-ZSM-5 catalysts were prepared by various modifi cation methods with boric acid, including ion-exchange, impregnation and direct synthesis. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), NH 3 -Temperature Programmed Desorption (NH 3 -TPD), N 2 adsorption-desorption, Fourier Transform Infrared spectrometry (FT-IR), 27 Al and 11 B MAS NMR spectra. The results revealed that the weak acidity of catalysts was signifi cantly increased by modifi cation. The catalytic activity was measured in a fi xed bed at 460 o C for methanol to propylene (MTP) reaction. The results of MTP reaction showed a great increment of the propylene selectivity for the boron modifi ed samples, especially for the directly synthesized B-ZSM-5 which also displayed high activity and selectivity towards C 2 = -C 4 = olefi ns. It was found that the remarkable selectivity strongly depended on the intensity of weak acidity.
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