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对磷铁改性的ZSM-5分子筛粉末进行X射线扫描,获得了较高分辨率的衍射数据,并由X射线荧光分析数据得到分子筛的化学组成。采用分子模拟软件中的建模及结构优化工具,构建了硅铝比为23.77的ZSM-5分子筛的三维空间构型,用分子力学方法计算二价铁离子在分子筛孔道中的位置并用Rietveld精修的方法验证铁离子在ZSM-5分子筛孔道中的位置。结果表明,金属改性的ZSM-5分子筛中二价铁离子主要存在于十元环S形孔道和直孔道交叉处,少量存在于直孔道中。计算了Fe~(2+)离子在孔道内的配位间距,对改性的ZSM-5分子筛进行了结构参数分析,最终确定了两种Fe~(2+)在孔道内的确切坐标分数。
The phosphorus-iron modified ZSM-5 molecular sieve powder was subjected to X-ray scanning to obtain higher-resolution diffraction data, and the chemical composition of the molecular sieve was obtained from X-ray fluorescence analysis data. The three-dimensional configuration of ZSM-5 molecular sieve with a Si / Al ratio of 23.77 was constructed by using the modeling and structural optimization tools in the molecular simulation software. The molecular dynamics method was used to calculate the position of ferrous ions in the molecular sieve pores and refined with Rietveld Method to verify the location of iron ions in the pores of ZSM-5 zeolite. The results show that the ferrous ions in the metal-modified ZSM-5 zeolite mainly exist at the intersections of the S-shaped channels and the straight channels in the ten-membered ring, and exist in the straight channels in a small amount. The coordination spacing of Fe 2+ ions in the pores was calculated. The structural parameters of the modified ZSM-5 zeolite were analyzed and the exact coordinate fractions of the two Fe 2+ ions in the pores were finally determined.