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近年来,Ga-ZSM-5型分子筛的合成与催化性能已有报道,但对Ga是否位于ZSM-5型沸石晶格中这一重要问题则显得证据不足。由于以往的合成均在NaOH等碱性介质中进行,重复性和产品的结晶度不能令人满意。本文报道在弱酸性介质中,NH_4F存在下,Ga-ZSM-5型分子筛的合成。这种新的合成途径,克服了在碱性介质中合成的缺点。用多种手段研究了Ga-ZSM-5型分子筛结构与性能的关系,为Ga对ZSM-5沸石骨架的同晶取代提供了充分的证据。
In recent years, the synthesis and catalytic properties of Ga-ZSM-5 zeolites have been reported. However, the important issue of whether Ga is located in the lattice of ZSM-5 zeolites appears to be insufficient evidence. Since the previous synthesis was carried out in an alkaline medium such as NaOH, the reproducibility and the degree of crystallinity of the product were unsatisfactory. This paper reports the synthesis of Ga-ZSM-5 molecular sieves in the presence of NH_4F in weakly acidic media. This new synthetic route overcomes the disadvantages of synthesis in alkaline media. The relationship between the structure and properties of Ga-ZSM-5 molecular sieve was studied by various means, which provided sufficient evidence for the isomorphous substitution of Ga on the zeolite framework of ZSM-5.