Synthesis Of Small Crystal ZSM-5 Zeolite With High Molar Ratio Of Silica To Alumina

ZSM-5 is more concerned for its unique pore system and good shape selectivity.Smallcrystals ZSM-5 zeolites have larger external surface, high surface energy and shorter channelsby comparing with the big zeolites.So,reducing the partical size is one of th ways to impovingthe catalysts. The synthesis of small crystal ZSM-5 zeolites with high molar ratio of silica toalumina have been synthesized successfully in this thesis, which were characterized by X-raydiffraction, transmission electron mocroscope, scan electron mocroscope, X-ray fluorescence.Results show that:(1)The partical size of the synthesized ZSM-5 are bigger obviously from the hignSiO₂/Al₂O₃ ratio gels, However, isopropanol addition to the high SiO₂/Al₂O₃ ratio gel wasproofed very helpful for the reduction of the crystal size of the product even in very smallamount.(2)The NaCl could affect the crystallinity and the partical size of the ZSM-5. The moreNaCl is used, the lower crystallinity is resulted, but the partical size become smaller at first,then grow bigger later. In the system to systhesize the ZSM-5 of 500～600nm, the suitableratio of NaCl to Al₂O₃ is 35.0.(3)Reducing the H₂O of the synthesizing system, the crystallinity of the ZSM-5 is down.Reducing the H₂O could make the partical size of the ZSM-5 smaller ,following the H₂O isreduced more and more ,it became bigger. The reason maybe is the reducing of the H₂O madethe gel so sticky that is benefit for big crystal ZSM-5.(4)The amount of the crystal seed to the system to synthesize the small crystal ZSM-5could not affect the crystallinity obviously. But ,when the amount is from 3% to 5%, thepartical size of the ZSM-5 became smaller obviously. So, the suitable amount of crystal is5%.(5) Increasing the alkalinity of the synthestic system could make the the partical size ofthe ZSM-5 smaller. But , the alkalinity of the synthetic system is too high to make thesoluility of the crystal nucleus, so that the partical size of the ZSM-5 would become bigger.(6) In the same system, using the n-butylamine as template to synthesize can get smallestcrystal ZSM-5 than using the ammonia water and the alcohol.