Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari, 09042 Monserrato, Italy.
Unit of Nanomaterial Chemistry, Department of Chemistry, University of Namur, 5000 Namur, Belgium.
Molecules. 2022 Dec 14;27(24):8883. doi: 10.3390/molecules27248883.
Functionalized aluminosilicate materials were studied as catalysts for the conversion of different cyclic carbonates to the corresponding epoxides by the addition of CO. Aluminum was incorporated in the mesostructured SBA-15 silica network. Thereafter, functionalization with imidazolium chloride or magnesium oxide was performed on the Al_SBA-15 supports. The isomorphic substitution of Si with Al and the resulting acidity of the supports were investigated via Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and NH adsorption microcalorimetry. The Al content and the amount of MgO were quantified via inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. The anchoring of the imidazolium salt was assessed by Si and C MAS NMR spectroscopy and quantified by combustion chemical analysis. Textural and structural properties of supports and catalysts were studied by N physisorption and X-ray diffraction (XRD). The functionalized systems were then tested as catalysts for the conversion of CO and epoxides to cyclic carbonates in a batch reactor at 100 or 125 °C, with an initial CO pressure (at room temperature) of 25 bar. Whereas the activity of the MgO/Al_SBA-15 systems was moderate for the conversion of glycidol to the corresponding cyclic carbonate, the Al_SBA-15-supported imidazolium chloride catalysts gave excellent results over different epoxides (conversion of glycidol, epichlorohydrin, and styrene oxide up to 89%, 78%, and 18%, respectively). Reusability tests were also performed. Even when some deactivation from one run to the other was observed, a comparison with the literature showed the Al-containing imidazolium systems to be promising catalysts. The fully heterogeneous nature of the present catalysts, where the inorganic support on which the imidazolium species are immobilized also contains the Lewis acid sites, gives them a further advantage with respect to most of the catalytic systems reported in the literature so far.
功能化的硅铝酸盐材料被研究作为催化剂，用于通过添加 CO 将不同的环状碳酸酯转化为相应的环氧化物。铝被掺入介孔 SBA-15 硅网络中。此后，在 Al_SBA-15 载体上进行了与氯化咪唑或氧化镁的功能化。通过 Al 魔角旋转（MAS）核磁共振（NMR）光谱和 NH 吸附微热量计研究了 Si 与 Al 的同晶取代和载体的酸度。Al 含量和 MgO 的量通过电感耦合等离子体发射光谱（ICP-OES）分析进行定量。通过 Si 和 C MAS NMR 光谱评估了咪唑盐的锚固，并通过燃烧化学分析进行了定量。载体和催化剂的结构和结构性质通过 N 物理吸附和 X 射线衍射（XRD）进行了研究。然后，在 100 或 125°C 的间歇反应器中，在初始 CO 压力（室温）为 25 巴的条件下，将功能化系统用作 CO 和环氧化物转化为环状碳酸酯的催化剂。虽然 MgO/Al_SBA-15 体系对于将缩水甘油转化为相应的环状碳酸酯的转化率适中，但 Al_SBA-15 负载的氯化咪唑催化剂在不同的环氧化物（缩水甘油、环氧氯丙烷和苯乙烯氧化物的转化率分别高达 89%、78%和 18%）中表现出优异的结果。还进行了可重复使用性测试。尽管从一次运行到另一次运行观察到一些失活，但与文献的比较表明，含 Al 的咪唑体系是有前途的催化剂。本催化剂的完全非均相性质，即在其上固定咪唑物种的无机载体也含有路易斯酸位，相对于迄今为止文献中报道的大多数催化体系具有进一步的优势。
