A core–shell catalyst mZSM-5@SO 4 2- /mSiO 2 composed of mZSM-5 core and SO 4 2- /mSiO 2 shell was prepared by the soft template method. Core-shell structure could promote the building of Brønsted -Lewis (B-L) acids interface and significantly improve the synergistic effect of B-L. In this paper, the Brønsted/Lewis (B/L) of mZSM-5@SO 4 2- /mSiO 2 was targeted regulating by innovatively introducing Brønsted acid (BA) sites into the shell. The optimal mZSM-5@SO 4 2- /mSiO 2 catalyst (B/L = 0.142) could achieve 72.1 % furfural yield at 140 ℃ for 1 h. In addition, 70.2 % furfural yield could be obtained after the catalyst was recycled and regenerated for 5 times. Combining In-situ IR and 13 C NMR, the reaction path was revealed in detail: xylose was first isomerized to xylulose and then dehydrated to furfural. This paper provides a research idea for the directional regulation of dual active sites of cascade reaction catalysts.
A core-shell carbon-based catalyst mZSM-5@SO 4 2- /mC-1.5N with mZSM-5 as core and SO 4 2- /mC-1.5 N as shell was prepared using phenolic resin as carbon source. The conversion of xylose was 97.4% and the furfural yield was 75.4% at 140 ℃ for 1 h when the catalyst was used to the reaction of xylose to furfural. The high activity of mZSM-5@SO 4 2- /mC-1.5 N was attributed to the core-shell structure could construct a high activity Brønsted acid-Lewis acid (BA-LA) interface, which promoted the synergistic effect of LA and BA and was conducive to the xylose-furfural cascade reaction. In additon, the combination of HNO 3 activation and H 2 SO 4 grafting method adjusted the density of -OH, -COOH and -SO 3 H on the mC surface, improved the Brønsted/Lewis (B/L) and hydrophilicity of the catalyst, and promoted the adsorption, fixation and transformation of xylose. Then, the effect -OH, -COOH and -SO 3 H in the reaction of xylose-furfural was studied by characterization analysis. Finally, the experimental results showed that mZSM-5@SO 4 2- /mC-1.5 N could reduce the activation energy of the xylose-furfural reaction, and the catalyst could maintain good stability after recycling and regeneration.
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