H-Spillover and SMSI Effects in Paraffin Hydroisomerization over Pt/WOx/ZrO2Bifunctional Catalysts
H-Spillover and SMSI Effects in Paraffin Hydroisomerization over Pt/WOx/ZrO2Bifunctional Catalysts
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DOI：
10.1006/jcat.1999.2435
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发表时间：
1999-04
影响因子：
7.3
通讯作者：
J. Santiesteban;D. Calabro;W. Borghard;C. Chang;J. Vartuli;Y. Tsao;M. Natal-Santiago;R. Bastian-R.-Bastia
中科院分区：
文献类型：
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作者：
J. Santiesteban;D. Calabro;W. Borghard;C. Chang;J. Vartuli;Y. Tsao;M. Natal-Santiago;R. Bastian-R.-Bastia
人们发现 Pt 改性的 WOx/ZrO2 催化剂体系在氢气存在下会发生各种转变。这些转变包括在室温下产生溢出氢、在高温下产生强烈的 Pt-W 相互作用以及钨的还原。我们使用氢化学吸附和程序升温还原技术表征了这些效应。我们还采用戊烷异构化作为测试反应，将这些变化与这些材料的酸催化联系起来。我们的研究结果表明，所有上述转变都对钨负载敏感。在钨含量为 15.9 wt% 时观察到室温氢气溢出，但在钨负载量≤8.4 wt% 时则不存在。较高钨负载量的催化剂在 >200°C 的氢气中表现出 Pt-W SMSI 效应；在较低的钨负载量下，需要更高的温度来引发这种效应。该结果与较高负载下钨氧种的还原性增加相一致。铂极大地促进了钨的还原，参与可逆的 Pt-W 强金属相互作用，并且可能增强戊烷异构化过程中的氢溢出。通过促进钨还原，Pt 会对这些 WOx/ZrO2 催化剂的高酸活性产生有害影响。
The Pt-modified WOx/ZrO2catalyst system is found to undergo various transformations in the presence of hydrogen. These transformations include the generation of spillover hydrogen at room temperature, the development of a strong Pt–W interaction at elevated temperatures, and tungsten reduction. We have characterized these effects using hydrogen chemisorption and temperature-programmed reduction techniques. We have also employed pentane isomerization as a test reaction to relate these changes to the acid catalysis of these materials. Our findings indicate that all of the above transformations are sensitive to tungsten loading. Room temperature hydrogen spillover is observed at 15.9 wt% tungsten, but is absent at tungsten loadings of ≤8.4 wt%. The higher tungsten loading catalyst exhibits a Pt–W SMSI effect in hydrogen at >200°C; at lower tungsten loadings much higher temperatures are required to induce this effect. This result agrees with the increasing reducibility of tungsten oxospecies at higher loadings. Platinum greatly facilitates the tungsten reduction, is involved in a reversible Pt–W strong metal interaction, and likely enhances hydrogen spillover during pentane isomerization. By facilitating tungsten reduction, Pt can have a deleterious effect on the high acid activity of these WOx/ZrO2catalysts.