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首页> 外文期刊>New Journal of Chemistry >Synthesis of polyoxymethylene dimethyl ethers over different microporous and mesoporous zeolites: the effects of acidity and pore size
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Synthesis of polyoxymethylene dimethyl ethers over different microporous and mesoporous zeolites: the effects of acidity and pore size

机译：不同微孔和中孔沸石中聚甲醛二甲基醚的合成：酸度和孔径的影响

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摘要

Polymethoxydimethyl ether (PODEn) is an ideal blending component of diesel oil. As a typical acid catalyzed reaction, studies on the structure-activity relationship of catalysts, especially the influence of acidity and pore size on PODEn synthesis, are of vital importance. Herein, three kinds of catalysts with different pore sizes, ZSM-5, Al-MCM-41 and Al-SBA-15 with variable Si/Al ratios, were chosen to investigate the effects of acidity and pore sizes on the yield, selectivity and product distribution of PODEn. X-ray diffraction, N-2 adsorption-desorption, transmission electron microscopy, X-ray fluorescence and ammonia temperature-programmed desorption were executed to characterize the structures and acid properties of obtained catalysts. By comparing the effect of varying acidity on the reaction under the conditions of constant pore size, it was found that ZSM-5, Al-SBA-15 and Al-MCM-41 all showed the same changing trend, and the synthesis process of PODEn required a suitable amount of acid, and insufficient or excessive acid would lead to a low yield of the product. By checking the catalytic activity of catalysts with different pore sizes under the same acidity conditions, it was demonstrated that when the acidity of the catalyst was too high, a relatively large pore size would be more conducive to the diffusion of formaldehyde monomers, thus reducing the formation rate of the by-product methyl formate and obtaining a larger yield and selectivity of the product. However, when the acidity was moderate or too low, the yield and selectivity of the product and the conversion of feedstock catalyzed by three kinds of porous catalysts reached basically the same value, illustrating that the pore size had no effect on the adsorption and diffusion process of products with relatively low local density of formaldehyde monomer. In addition, the pore size of the catalyst had no effect on the product distribution and chain length under suitable acidic conditions.
机译：聚甲氧基二甲基醚（PODEN）是柴油的理想混合组分。作为典型的酸催化反应，对催化剂的结构 - 活性关系的研究，尤其是酸度和孔径对Poden合成的影响，具有至关重要的重要性。本文三种不同孔径的催化剂，ZSM-5，AL-MCM-41和Al-SBA-15具有可变的Si / Al比，被选择来调查酸性和孔大小的对产率，选择性的影响，并Poden的产品分布。执行X射线衍射，N-2吸附 - 解吸，透射电子显微镜，X射线荧光和氨温度编程的解吸，表征所得催化剂的结构和酸性。通过比较不同酸度对恒定孔径条件下反应的影响，发现ZSM-5，Al-SBA-15和Al-MCM-41都显示出相同的变化趋势，以及Poden的合成过程所需量合适的酸，不足或过量的酸会导致产物的低产量。通过在相同的酸度条件下检查不同孔径的催化剂的催化活性，证明当催化剂的酸度太高时，相对大的孔径将更有利于甲醛单体的扩散，从而减少了甲醛单体的扩散，从而减少了副产物甲酯的形成率并获得产品的较大产率和选择性。然而，当酸度适中或过低时，产品的产率和选择性和三种多孔催化剂催化的原料转化基本相同的值，说明孔径对吸附和扩散过程没有影响甲醛单体局部密度相对较低的产品。此外，催化剂的孔径对合适的酸性条件下的产物分布和链长没有影响。

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  • 来源
    《New Journal of Chemistry》 |2020年第7期|共9页
  • 作者

    Xue Zhenzhen; Lu Changbo; Shang Hongyan; An Gaojun; Zhang Jun; Zhao Shidong; Liu Yu;

  • 作者单位

    Beijing Inst New Energy Technol Beijing 102300 Peoples R China;

    Beijing Inst New Energy Technol Beijing 102300 Peoples R China;

    China Univ Petr Coll Sci Qingdao 266580 Shandong Peoples R China;

    Beijing Inst New Energy Technol Beijing 102300 Peoples R China;

    China Univ Petr Coll Mat Sci &

    Engn Qingdao 266580 Shandong Peoples R China;

    China Univ Petr Coll Sci Qingdao 266580 Shandong Peoples R China;

    Beijing Inst New Energy Technol Beijing 102300 Peoples R China;

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  • 正文语种 eng
  • 中图分类 化学;
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