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Open AccessArticle

Hafnium-Doped Mesoporous Silica as Efficient Lewis Acidic Catalyst for Friedel–Crafts Alkylation Reactions

1,2,3,*, 2 and 1,*
1
Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, China
2
College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
3
Department of Chemical and Biomolecular Engineering, University of California-Berkeley, Berkeley, CA 94706, USA
*
Authors to whom correspondence should be addressed.
Nanomaterials 2019, 9(8), 1128; https://doi.org/10.3390/nano9081128
Received: 11 July 2019 / Revised: 28 July 2019 / Accepted: 30 July 2019 / Published: 5 August 2019
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Abstract

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. View Full-Text
Keywords: Friedel–Crafts alkylation; hafnium-doped mesoporous silica; benzyl alcohol; aromatics; Lewis acid Friedel–Crafts alkylation; hafnium-doped mesoporous silica; benzyl alcohol; aromatics; Lewis acid
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Huang, Y.-B.; Luo, Y.-J.; Wang, F. Hafnium-Doped Mesoporous Silica as Efficient Lewis Acidic Catalyst for Friedel–Crafts Alkylation Reactions. Nanomaterials 2019, 9, 1128.

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