Huang Yao-Bing, Luo Yu-Jia, Wang Fei
Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, China.
College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China.
Nanomaterials (Basel). 2019 Aug 5;9(8):1128. doi: 10.3390/nano9081128.
The development of an efficient solid catalyst for Friedel-Crafts (FC) reactions is of great importance to organic synthetic chemistry. Herein, we reported the hafnium-doped mesoporous silica catalyst Hf/SBA-15 and its first use for Friedel-Crafts alkylation reactions. Catalysts with different Si/Hf ratios were prepared and characterized, among which Hf/SBA-15(20) (Si/Hf = 20:1) was the most active catalyst, offering up to 99.1% benzylated product under mild reaction conditions. The influences of reaction conditions on the product were systematically investigated and compared. Pyridine-IR characterization of the catalyst showed that Lewis acid formed the primary active sites for the Friedel-Crafts alkylation reaction. X-ray photoelectron spectroscopy (XPS) characterization revealed that the electron shift from the Hf center to the silica framework resulted in a more active Lewis metal center for FC reactions. Moreover, the catalyst was successfully applied to the alkylation reaction with different alcohols and aromatic compounds. Finally, the Hf/SBA-15(20) catalyst also showed good recyclability in the recycling runs, demonstrating its high potential of being used for large scale FC reactions in the industry.
开发一种用于傅克（FC）反应的高效固体催化剂对有机合成化学具有重要意义。在此，我们报道了铪掺杂的介孔二氧化硅催化剂Hf/SBA-15及其首次用于傅克烷基化反应。制备并表征了具有不同硅/铪比的催化剂，其中Hf/SBA-15(20)（硅/铪 = 20:1）是活性最高的催化剂，在温和反应条件下苄基化产物产率高达99.1%。系统研究并比较了反应条件对产物的影响。催化剂的吡啶红外光谱表征表明，路易斯酸形成了傅克烷基化反应的主要活性位点。X射线光电子能谱（XPS）表征显示，电子从铪中心转移到二氧化硅骨架导致形成了对傅克反应更具活性的路易斯金属中心。此外，该催化剂成功应用于与不同醇类和芳香化合物的烷基化反应。最后，Hf/SBA-15(20)催化剂在循环使用中也表现出良好的可回收性，表明其在工业大规模傅克反应中具有很高的应用潜力。
