The structure and acidity of HZSM-5 zeolites were modified using different post treatment methods: alkaline treatment

steam treatment

and alkaline-steaming treatment. The catalytic performances of modified zeolites were tested in 1-butene catalytic cracking. Their physicochemical properties were characterized by N2 adsorption

scanning electron microscopy (SEM)

X-ray diffraction (XRD)

and infrared spectroscopy with pyridine adsorption (Py-IR). The acidities of zeolites increased after the alkaline treatment

and as a result

the activity of butene cracking increased and the selectivity of propylene decreased. However

the deactivation rate of alkaline-treated zeolites had no significant change. There was a pronounced development of mesopores (5—20 nm) with a broad pore-size distribution in alkaline-treated ZSM-5 zeolites. Mesopores (2—4 nm) with a narrow distribution is observed after steaming treatment

while the mesopore volume is low. Zeolites after alkaline-and steaming-treatment showed two kinds of mesopore distributions

2—4 nm (narrow) and 5—20 nm (broad). Due to the decrease of Brønsted acidic sites

the selectivity of propylene increased over ZSM-5 zeolites with any of the post treatments; a relatively stable propylene yield was obtained after the reaction of 2.5 h (except for zeolites treated with high concentration of alkaline followed by steaming treatment).