Research On Catalytic Properties Of SAPO-34 Molecular Sieve Synthetized With Coal Kaolin Asraw Material

This paper summarizes the development of industrial catalysis, coal series kaolin, research status, synthesis method of zeolite molecular sieve and the modified of SAPO-34 and its mechanism for the methanol to olefins(MTO) reaction. On the basis of check the large number relevant literature on the synthesis, mechanism, modification, application of SAPO-34, the SAPO-34 was synthesized use coal series kaolin as raw materials by hydrothermal synthesis method, and the process conditions on preparation of SAPO-34 by metakaolin be sure. The synthesis process was studied by application the modern analysis and testing technology such as XRD, XRF, IR, TGA, SEM, NH3-TPD, spectrophotometer, p H meter and so on. Finally, SAPO-34 molecular sieve sample was modified by the metal ion, fluoride ion and surface active agent. Modified molecular sieve were tested by MTO experiments. The main contents are as follows:By pre-treated Wanbei Coal Series Kaolin this cheap mineral material like calcination and activation and so on, make it become the suitable raw material for preparation of SAPO-34 molecular sieve by hydrothermal method. SAPO-34 molecular sieve sample was prepared by hydrothermal method in high temperature crystallization, used metakaolin as the raw material. On the basis of the large number experiment, we are in-depth studied of the influence on synthesis of SAPO-34 molecules at the reaction mixture composition and the water and heat conditions, and determined the suitable technological parameters of SAPO-34 molecular sieve preparation by hydrothermal method: The ratio of raw materials is(Metakaolin+ Pseudoboehmite):P2O5:3TEA:60H2O, crystallization time is 48 h at the temperature of 180 oC. The cube shaped SAPO-34 molecular sieve are synthesized with regular appearance and its average particle size is 10mm. which for the large-scale industrial production of SAPO-34 molecular sieve opens up a new route. The synthesis process was studied: process that metakaolin water heat synthesis of SAPO-34 molecular sieve can be divided into four stages: Colloidal particle reunion、the formation of crystal nucleus、silicon into nucleus and crystal transformation of the SAPO-5. The formation mechanism of SAPO-34 molecular sieve is a solid solution, liquid phase reaction mechanism.By in situ metal, fluoride ion and surface active agent CTAB modification on SAPO-34 molecular sieve, we get the pure modified molecular sieve, and we use it for MTO reaction, the ethylene and propylene as the target product. Experiments show that, Except for Zn metal, whether in situ metal modified or HF, CTAB modified can greatly improve the one-way service life and olefin selectivity of the catalyst. ethylene selectivity of Fe APSO-34 is up to 61.6%, its total selectivity is up to 90.27%, which is higher than the other modified molecular sieve. The CTAB-SAPO-34 molecular sieve catalytic performance is good, the one-way service life is 450 min, which is higher than other modified molecular sieve, and its ethylene selectivity is 56.88%. The above results for the MTO catalyst modified provides reference.