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球形整体式ZSM-5分子筛催化剂的制备及其MTO催化性能

发布时间:2018-03-05 01:10

  本文选题:球形整体式分子筛 切入点:元素改性 出处:《宁夏大学》2017年硕士论文 论文类型:学位论文


【摘要】:本论文报道了一种一步制备球形整体式ZSM-5分子筛的新方法。针对球形整体式ZSM-5分子筛在甲醇制取低碳烯烃反应的过程中选择性相对较低的问题,文章选择在球形整体式分子筛的基础上,利用金属元素Fe和非金属元素P的掺杂对其改性,以提高其在MTO反应过程中低碳烯烃的选择性。并且基于实验室前期的工作,我们又对球形整体式ZSM-5分子筛用AlPO4-5分子筛进行包覆,成功制备了一种复合分子筛,进一步达到了提高低碳烯烃选择性的目的,具体方法如下:首先,利用一步法制备球形整体式ZSM-5分子筛的新方法,制备出球形整体式ZSM-5分子筛。对其制备路径进行了研究,得出以下结论:制备的小球基本没有催化活性,对其焙烧后仍然表现出极差的MTO催化活性。但是用硝酸铵溶液处理过的球形整体式分子筛表现出良好的催化活性。在此基础上我们进一步研究了焙烧温度对其催化效果的影响,结果表明:550℃的焙烧条件下,其MTO催化性能最佳。最后考察了工业ZSM-5不同添加量的影响,结果表明:制备的工业ZSM-5含量为18%的球形整体式分子筛表现出了较好的催化活性,且满足整体式分子筛在固定床反应器的装管要求。其低碳烯烃的选择性达到69.1%,乙烯选择性达到25.9%,丙烯的选择性达到33%。其次,在满足制备球形整体式ZSM-5分子筛最优制备路径的基础上,用不同含量的金属Fe元素对其进行改性。结果表明:3%Fe元素改性的球形整体式分子筛低碳烯烃的选择性达到了 75.2%,而乙烯和丙烯的选择性分别达到了 38.2%,29.4%。为了进一步提高丙烯和低碳烯烃的选择性,采用不同含量非金属P对其进行改性。结果表明:1%P改性的球形整体式分子筛最好,低碳烯烃的选择性达到了 76.7%,乙烯的选择性达到了 25.2%,丙烯的选择性达到了 38.9%。最后,采用不同的合成方法制备出了 ZSM-5/AlPO4-5复合分子筛,并将其运用到MTO反应中。得出结论:在150℃,转速2r/min晶化3h的均相反应里,我们以SAPO-5分子筛为晶种制备出了具有良好催化性能ZSM-5/AlPO4-5复合分子筛,其低碳烯烃选择性达到74.7%,丙烯选择性达到34.9%,乙烯的选择性达到28.2%。
[Abstract]:In this paper, a new one-step method for the preparation of spherical monolithic ZSM-5 molecular sieve is reported. The selectivity of spherical monolithic ZSM-5 molecular sieve is relatively low in the process of methanol production of low olefins. In order to improve the selectivity of low olefins in the MTO reaction process, the spherical monolithic molecular sieve was modified by doping the metal element Fe and the nonmetallic element P in order to improve the selectivity of low olefins in the process of MTO reaction. We also coated the spherical monolithic ZSM-5 molecular sieve with AlPO4-5 molecular sieve, and successfully prepared a composite molecular sieve, which further achieved the purpose of improving the selectivity of low olefins. The specific methods are as follows: first, The spherical monolithic ZSM-5 molecular sieve was prepared by a new one-step method. The preparation path of the spherical monolithic ZSM-5 molecular sieve was studied, and the following conclusions were obtained: the prepared pellets had little catalytic activity. However, the spherical molecular sieve treated with ammonium nitrate solution showed good catalytic activity. On this basis, the effect of calcination temperature on the catalytic activity was further studied. The results showed that the catalytic activity of MTO was the best at the calcination temperature of 5: 550 鈩,

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