Abstract

A series of β zeolite catalysts with different acidic properties were prepared. The acidity of these catalysts was characterized by solid-state nuclear magnetic resonance（NMR） probe molecule technique. These catalysts were tested for the conversion of glucose to methyl levulinate. 31P NMR of trimethyl phosphine adsorbed on Sn-Al-β zeolite showed that the introduction of framework Sn and Al atoms resulted in both Br?nsted and Lewis acidity. Three Br?nsted acid sites with different acidic strength were distinguished by 13C NMR of 2-13C-acetone probe molecule， with one being close to “super acid”， which is most likely generated by the synergistic effect between the spatially adjacent Br?nsted and Lewis acid sites. The catalytic reaction of glucose to methyl levulinate showed that Sn-Al-β was superior in catalytic activity and selectivity to methyl levulinate as compared to Sn-β containing only Lewis acid sites， Al-β containing only Br?nsted acid sites and the mixed sample of Sn-β and Al-β. This can be accounted by the synergy of Br?nsted and Lewis acid sites and stronger Br?nsted acidity of Sn-Al-β.

链接：http://www.cjcu.jlu.edu.cn/CN/10.7503/cjcu20220138