Confinement Effects in Lewis Acid-Catalyzed Sugar Conversion: Steering Toward Functional Polyester Building Blocks

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• 作者：Rik De Clercq ; Michiel Dusselier ; Charles Christiaens ; Jan Dijkmans ; Remus Ion Iacobescu ; Yiannis Pontikes ; Bert F. Sels
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：October 2, 2015
• 年：2015
• 卷：5
• 期：10
• 页码：5803-5811
• 全文大小：525K
• ISSN：2155-5435

文摘

We report the use of solid Lewis acid catalysts for the conversion of tetrose sugars to four-carbon 伪-hydroxy acid esters (C₄-AHA), which are useful as functional polyester building blocks. Sn-尾 was by far the most active and selective catalyst, yielding up to 80% methyl vinyl glycolate (MVG), methyl-4-methoxy-2-hydroxybutanoate (MMHB), and 伪-hydroxy-纬-butyrolactone (HBL) combined at 95% conversion. A very high turnover frequency (TOF) of 330 mol_C4-AHA mol_Sn h^鈥? was attained using Sn-尾, a more than 6-fold increase compared with homogeneous SnCl₄路5H₂O. It is shown that, using different Sn-based catalysts with various pore sizes, the product distribution is strongly dependent on the size of the catalyst pores. Catalysts containing mainly mesopores, such as Sn-MCM-41 or Sn-SBA-15, prefer the production of the more bulky MMHB, whereas microporous catalysts such as Sn-尾 or Sn-MFI favor the production of MVG. This effect can be further enhanced by increasing the reaction temperature. At 363 K, only 20% MVG is attained using Sn-尾, but at 433 K, this increases to 50%. Using a kinetic analysis, it was found that, in microporous catalysts, steric hindrance near the Sn active site in the catalyst pores plays a dominant role in favoring the reaction pathway toward MVG. Moreover, the selectivity toward both products is kinetically controlled.