Abstract

The behavior of two hybrid catalysts: inorganic/organic (KI/chitin) and inorganic/inorganic (KI/amorphous silica-alumina) on the CO₂ cycloaddition to Propylene oxide has been compared. Conversions of KI/chitin and KI/Si-Al were 99 and 97% respectively. KI/Si-Al shows a type IV N₂ adsorption isotherm at P₀/P of 0.6-0.9 of mesoporous nature with a significant concentration of Lewis acid sites, its FT-IR analysis shows that CO₂ can be adsorbed as organic “bridging” carbonate onto the support’s surface, which has an important role in the reaction mechanism. Kinetic analysis shows that the organic co-catalyst is up to 1.5 times faster for the CO₂ cycloaddition than the inorganic co-catalyst at 160 °C bu both show very similar rate at 120 °C. Both supported catalysts show a significantly lower E_a than that calculated for free KI, although both show comparable activation energies. This insight gives interesting findings on how hybrid catalyst systems behave in an utmost crucial CO₂ fixation reaction, being the foundations of future investigation on scale-up applications.

摘要

比较了两种混合催化剂：无机/有机（KI/几丁质）和无机/无机（KI/无定形二氧化硅-氧化铝）对环氧丙烷的 CO ₂环加成反应。KI/几丁质和 KI/Si-Al 的转化率分别为 99% 和 97%。_{KI/Si-Al 在 P 0} /P 为 0.6-0.9 的介孔性质下显示出 IV 型 N ₂吸附等温线，具有显着浓度的路易斯酸位点，其 FT-IR 分析表明 CO ₂可以作为有机“桥接”吸附”碳酸盐附着在载体表面，在反应机理中起重要作用。_{动力学分析表明，有机助催化剂对 CO 2}的反应速度提高了 1.5 倍与无机助催化剂相比，在 160 °C 下的环加成反应在 120 °C 下都表现出非常相似的速率。两种负载型催化剂的E _a都显着低于游离 KI 的计算值，尽管两者都显示出相当的活化能。这一见解提供了关于混合催化剂系统如何在最关键的 CO ₂固定反应中表现的有趣发现，成为未来放大应用研究的基础。