Effects of ammonium exchange and Si/Al ratio on the conversion of methanol to propylene over a novel and large partical size ZSM-5

One type of ZSM-5 zeolite with large partical size was prepared and characterized by XRD, SEM, N(2) adsorption-desorption, XRF, Py-IR and NH(3)-TPD techniques. Effects of ammonium exchange and SiO(2)/Al(2)O(3) molar ratios on the reaction of methanol to propylene (MTP) over Na-ZSM-5 and H-ZSM-5 zeolites have been studied in a fixed-bed flow reactor under the operating conditions of T = 500 degrees C, P = 1 atm, and WHSV = 6 h(-1). Ammonium exchange led to a rapid decrease in Na content for Na-ZSM-5 zeolite. The reaction results indicated that Na-ZSM-5 and H-ZSM-5 with different SiO(2)/Al(2)O(3) molar ratios all exhibited high activity for methanol conversion. Ammonium exchange and the decreased SiO(2)/Al(2)O(3) molar ratio of ZSM-5 zeolite led to an increase both in strong acid sites and weak acid sites. Na-ZSM-5 with high SiO(2)/Al(2)O(3) molar ratio was favorable for the formation of propylene. The highest propylene selectivity (45.9%) was obtained over Na-ZSM-5 zeolite catalyst with SiO(2)/Al(2)O(3) molar ratio of 220.