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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >High acidity unilamellar zeolite MCM-56 and its pillared and delaminated derivatives
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High acidity unilamellar zeolite MCM-56 and its pillared and delaminated derivatives

机译：高酸度单层沸石MCM-56及其柱状和分层衍生物

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摘要

The unilamellar form of zeolite MWW, MCM-56, which is obtained by direct hydrothermal synthesis has been studied with regard to acidity and porosity in its original and post-synthesis modified pillared and delaminated forms. The acidity measured by FTIR was found to be only slightly lower than the highly active 3-D MWW forms, MCM-22 and MCM-49. Pivalonitrile adsorption, which is a measure of spatial openness, showed 50% accessibility vs. <30% for MCM-22/49. It highlights the potential of MCM-56 as a layered material with increased access to acid sites because it does not entail laborious post-synthesis modification. Swelling, pillaring and delamination of MCM-56 are facile but result in a reduction in the number of Br?nsted acid sites (BAS) while increasing accessibility to pivalonitrile. The delamination procedure involving sonication and acidification of the highly basic mother liquor produces the most visible increase in surface area and access to all BAS. The accompanying doubling of the solid yield and the decrease in absolute number of BAS suggest significant precipitation of dissolved silica generated during swelling and sonication in high pH medium. The viability of separating surfactant covered layers upon sonication with the consequence of exposing hydrophobic hydrocarbon tails to aqueous environment is addressed.
机译：已经研究了通过直接水热合成获得的单层形式的MWW沸石MCM-56的酸度和孔隙率，其原始和合成后的修饰是柱状和分层形式。发现通过FTIR测量的酸度仅比高活性3-D MWW形式MCM-22和MCM-49略低。新戊腈吸附是一种测量空间开放性的方法，显示出可达性为50％，而MCM-22 / 49仅为<30％。它强调了MCM-56作为分层材料的潜力，因为它不需要进行费力的合成后修饰，因此可以增加进入酸性位置的可能性。 MCM-56的膨胀，起柱和分层都很容易，但导致布朗斯台德酸性位点（BAS）数量减少，同时增加了对新戊腈的可及性。涉及高碱性母液的超声处理和酸化的分层过程会产生最明显的表面积增加，并能进入所有BAS。随之而来的固体产率增加一倍和BAS绝对数量的减少表明在高pH介质中溶胀和超声处理过程中产生的溶解二氧化硅大量沉淀。解决了在超声处理下分离表面活性剂覆盖层的可行性，其结果是将疏水性烃尾巴暴露在水性环境中。

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