Synthesis of nano-sized SAPO-34 with morpholine-treated micrometer-seeds and their catalytic performance in methanol-to-olefin reactions

摘要

Uniformly nano-sized SAPO-34 zeotypes were synthesized using morpholine (MOR)-treated micrometer-sized SAPO-34 (MS-SAPO-34) seeds and MOR as the template. The samples were prepared with different amounts of MOR-treated MS-SAPO-34 seeds and characterized by XRD, SEM, ICP-OES, N-2 adsorption-desorption, NH3-TPD, Si-29 NMR, TGA and GC-MS. Using MOR-treated MS-SAPO-34 seeds decreased the crystal size of the SAPO-34 to 200-500 nm. In addition, the samples prepared with MOR-treated MS-SAPO-34 seeds had larger external surface areas, lower Si contents, and lower concentration and weaker strength of the strong acid sites than conventional SAPO-34. The effects of MOR treatment time on the seed properties and on the subsequent SAPO-34 fabrication were also investigated. After MOR-treatment of the MS-SAPO-34 seeds for 30 h, micrometer-sized seeds were broken into nanoparticles, which was indispensable for successful synthesis of nano-sized SAPO-34. When studied as a catalyst for the methanol to olefin reaction, the nano-sized SAPO-34 exhibited excellent catalytic performance.