Abstract: In this study, nano-scaled SAPO-34 molecualr sieves with size in the range of 200~300 nm were synthesized by the two-step crystallization and H2O2 oxidation process, with pseudoboehmite, colloidal silica and H3PO4 as sources of aluminum, silicon and phosphorous and TEAOH as templates. The prepared SAPO-34 was characterized by XRD, SEM, NH3-TPD, BET and so on. The catalytic performance of the SAPO-34 on the methanol-to-olefins reactions (MTO) was carried out on a fixed bed. The results showed that the particle size of the SAPO-34 could be effectively modulated by the crystallization temperature of the two-step crystallization process. In particular, when the first and second crystallization were conducted at 130℃ and 180℃, cubic SAPO-34 with 200~300 nm size could be successfully synthesized. Compared with the micro-scaled SAPO-34 prepared by the traditional hydrothermal process, the nano-scaled SAPO-34 crystals synthesized here showed better performance in the MTO reaction and the selectivity of C2~C4 and the lifetime for one-turn could attained about 92% and 10 hours, respectively.

Key words: nano-scaled SAPO-34, two-step crystallization, H2O2 oxidizing treatment, MTO