Comparative study of n-pentane isomerization over solid acid catalysts, heteropolyacid, sulfated zirconia, and mordenite:: dependence on hydrogen and platinum addition
Comparative study of n-pentane isomerization over solid acid catalysts, heteropolyacid, sulfated zirconia, and mordenite:: dependence on hydrogen and platinum addition
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DOI：
10.1016/s0021-9517(03)00162-3
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发表时间：
2003-10-01
影响因子：
7.3
通讯作者：
Naccache, C
中科院分区：
文献类型：
--
作者：
Essayem, N;Ben Taârit, Y;Naccache, C
研究了固体酸催化剂(NH4)(2.5)H0.5PW12O40、硫酸氧化锆盐和氢型丝光沸石对戊烷骨架异构化反应的影响。通过研磨等重量的铂/二氧化硅和上述每一种固体酸得到的复合双功能催化剂也用于该反应。讨论了正戊烷在单官能团催化剂和双官能团催化剂上异构化的各种反应机理。423和473K下产物分布的分析表明，在单官能团杂多酸和硫酸化氧化锆催化剂上，主要的反应路径是双分子路径，包括连接聚合和裂化。在这些操作条件下，异戊烷的选择性较低。单官能团H-丝光沸石只有在498K HPA和ZrO2-SO4条件下才表现出明显的活性。尽管比氢型丝光沸石表现出更强的酸性，但不要通过单分子途径激活正戊烷，因为“超强酸型催化剂”应该这样做。当反应温度为473K及以上时，戊烯的平衡浓度才显着，因此在反应温度为473K及以上时，戊烷发生双官能团异构化反应。单分子双功能机理是获得高异构化选择性的首选途径。(C)2003 Elsevier Inc.保留所有权利。
Skeletal isomerization of pentane over solid acid catalysts (NH4)(2.5)H0.5PW12O40, sulfated zirconia, and H-mordenite has been studied. Hybrid bifunctional catalysts obtained by grinding equal weights of Pt/SiO2 and each of the above solid acids were also used for the reaction. Various mechanistic aspects for n-pentane isomerization over monofunctional and bifunctional catalysts, in the presence or absence of hydrogen in the feed, are discussed. Analysis of product distributions at 423 and 473 K indicated that over monofunctional heteropolyacids and sulfated zirconia catalysts, the main reaction path is the bimolecular one, involving conjunct polymerization and cracking. Under these operating conditions the selectivity to isopentane is low. Monofunctional H-mordenite shows a significant activity only at 498 K. HPA and ZrO2-SO4. although showing stronger acidity than H-mordenite, do not activate n-pentane through a monomolecular path as "superacid-type catalysts" are expected to. Bifunctional isomerization of pentane appears at a reaction temperature of 473 K and up since the equilibrium concentration of pentene is significant only when the reaction temperature is 473 K and up. A monomolecular bifunctional mechanism is the preferred route for reaching high isomerization selectivity. (C) 2003 Elsevier Inc. All rights reserved.