Tungstated zirconia was supported on mesoporous SBA‐15 by impregnation in supercritical ethanol. The resultant catalyst promoted with 1 wt% of Pt shows 100% selectivity of iso‐pentane and two times higher conversion in n‐pentane isomerization than the one prepared by conventional impregnation. Supercritical impregnation exerts no destruction of the porous silica and offers better dispersion of tungstated zirconia than conventional impregnation. Optimized loading of WO₃/ZrO₂/SBA‐15 is 20/40/40 wt%, which infers to 2.4 W‐atoms/nm² and 8.9 Zr‐atoms/nm² dispersed on the SBA‐15 support. Moreover, introducing a proper mole fraction of hydrogen in the reactants markedly improves the catalytic activity in n‐pentane isomerization. The role of hydrogen was not only served as the reactants, it also acted to regenerate Brønsted acid sites during n‐pentane isomerization. However, overdose of hydrogen leaded to a leveling‐off in the rate of isomerization and enhanced hydrogenolysis reaction. The in situ IR spectroscopic studies suggested that Brønsted acid sites were the active centers for the isomerization. A reaction mechanism was, therefore, proposed that heterolytic fission of hydrogen and dehydrogenation of n‐pentane took place over Pt. The secondary carbocation formed over Brønsted acid sites was rearranged to a tertiary carbocation by methyl migration, followed by reacting with a hydride to generate iso‐pentane.

中文翻译：

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超临界浸渍法制备的介孔SBA-15负载的正戊烷在铂促进的钨基氧化锆上的异构化

通过在超临界乙醇中浸渍，将钨态氧化锆负载在中孔SBA-15上。用1 wt％的Pt促进的所得催化剂显示出100％的异戊烷选择性，正戊烷异构化转化率是传统浸渍法制备的催化剂的两倍。与常规浸渍相比，超临界浸渍不会破坏多孔二氧化硅，并提供钨态氧化锆更好的分散性。WO ₃ / ZrO ₂ / SBA-15的最佳负载量为20/40/40 wt％，可推断为2.4 W-atoms / nm ²和8.9 Zr-atoms / nm ²分散在SBA-15支持上。此外，在反应物中引入适当的氢摩尔分数可显着提高正戊烷异构化反应的催化活性。氢的作用不仅充当反应物，而且在正戊烷异构化过程中还起到了再生布朗斯台德酸位的作用。然而，过量的氢气导致异构化速率趋于平稳并增强了氢解反应。原位红外光谱研究表明，布朗斯台德酸位点是异构化的活性中心。因此，提出了一种反应机理，即氢的异质裂变和n的脱氢。戊烷在铂上发生。布朗斯台德酸位上形成的次级碳正离子通过甲基迁移而重排为叔碳正离子，然后与氢化物反应生成异戊烷。