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Factors that Determine Zeolite Stability in Hot Liquid Water

机译:决定热水中沸石稳定性的因素

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摘要

The susceptibility of zeolites to hot liquid water may hamper their full utilization in aqueous phase processes, such as those involved in biomass conversion and upgrading reactions. Interactions of zeolites with water strongly depend on the presence of hydrophilic moieties including Bronsted acid sites (BAS), extraframework cations, and silanol defects, which facilitate wetting of the surface. However, it is not clear which of these moieties are responsible for the susceptibility of zeolites to liquid water. Previous studies have offered contradictory explanations because the role of each of these characteristics has not been investigated independently. In this work, a systematic comparison has been attempted by relating crystallinity losses to the variation of each of the five zeolite characteristics that may influence their stability in liquid water, including number of BAS, Si-O-Si bonds, framework type, silanol defects, and extraframework AI. In this study, we have systematically monitored the crystallinity changes of a series of HY, H-ZSM-5, and H-β zeolite samples with varying Si/Al ratio, density of BAS, zeolite structure, and density of silanol defects upon exposure to liquid water at 200 ℃. The results of this comparison unambiguously indicate that the density of silanol defects plays the most crucial role in determining susceptibility of zeolites to hot liquid water. By functionalizing the silanol defects with organosilanes, the hydrophobicity of defective zeolite is increased and the tolerance to hot liquid water is significantly enhanced.
机译:沸石对热水的敏感性可能会妨碍它们在水相过程中的充分利用,例如那些参与生物质转化和提质反应的过程。沸石与水的相互作用在很大程度上取决于亲水性部分的存在,包括布朗斯台德酸位点(BAS),骨架外阳离子和硅烷醇缺陷,它们有助于表面润湿。然而,尚不清楚这些部分中的哪一个引起沸石对液态水的敏感性。先前的研究提供了相互矛盾的解释,因为尚未独立研究每个特征的作用。在这项工作中,通过将结晶度损失与可能影响其在液态水中的稳定性的五种沸石特性(包括BAS的数量,Si-O-Si键数,骨架类型,硅烷醇缺陷)的变化相关联,尝试进行系统的比较。以及Extraframework AI。在这项研究中,我们已经系统地监测了一系列HY,H-ZSM-5和H-β沸石样品的结晶度变化,这些样品具有变化的Si / Al比,BAS密度,沸石结构以及暴露后的硅烷醇缺陷密度。到200℃的液态水。该比较结果明确表明,硅烷醇缺陷的密度在确定沸石对液态热水的敏感性中起着至关重要的作用。通过用有机硅烷对硅烷醇缺陷进行官能化,可提高缺陷沸石的疏水性,并显着提高对热水的耐受性。

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  • 来源
    《Journal of the American Chemical Society》 |2015年第36期|11810-11819|共10页
  • 作者单位

    School of Chemical, Biological and Materials Engineering, University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States,Center for Interfacial Reaction Engineering (CIRE), University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States;

    Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States,Center for Interfacial Reaction Engineering (CIRE), University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States;

    Department of Chemistry & Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306-4390, United States;

    Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States,Center for Interfacial Reaction Engineering (CIRE), University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States;

    School of Chemical, Biological and Materials Engineering, University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States,Center for Interfacial Reaction Engineering (CIRE), University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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