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Promotion effect of Mg on a post-synthesized Sn-Beta zeolite for the conversion of glucose to methyl lactate

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Abstract

Mg-Sn-Beta zeolites with different Mg/Sn molar ratios were prepared from the parent deAl-Beta by a coimpregnation method. The samples were characterized by powder X-ray diffraction (XRD), N2 physisorption, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy of the –OH region and probe molecule (pyridine, CD3CN and CHCl3) adsorption. The results indicate that Mg2+ and Sn4+ can react with silanol nests and incorporate into the framework of Beta zeolite. Moreover, it is relatively facile to incorporate Sn4+ into the framework. The framework metal sites generate Lewis (L) acid sites; however, the L acid strength of the framework Mg2+ is weaker than that of framework Sn4+. A small amount of Mg2+ interacts with isolated silanols to form extraframework species. Therefore, the introduction of Mg2+ results in a significant reduction in silanol defects and an increase in L acidity/basicity of Mg-Sn-Beta. Mg-Sn-Beta with Mg/Sn molar ratio of 1 has the least silanol defects. In the conversion of glucose to methyl lactate (MLA), Mg-Beta is less active than Sn-Beta due to its weaker L acidity. The TOF value for MLA formation increased in the order of Sn-Beta < 0.25Mg-Sn-Beta ≈ 4Mg-Sn-Beta < 1Mg-Sn-Beta, which is closely related to the amount of silanol defects in the catalysts. A kinetic study indicates that the apparent activation energy of the retro-aldol of fructose to MLA, which is the rate-determining step of glucose conversion to MLA, decreases over Mg-Sn-Beta compared to that over Sn-Beta and thus, the formation of MLA was promoted.

Graphical abstract: Promotion effect of Mg on a post-synthesized Sn-Beta zeolite for the conversion of glucose to methyl lactate

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Supplementary files

Article information


Submitted
24 Nov 2019
Accepted
19 Dec 2019
First published
19 Dec 2019

Catal. Sci. Technol., 2020, Advance Article
Article type
Paper

Promotion effect of Mg on a post-synthesized Sn-Beta zeolite for the conversion of glucose to methyl lactate

X. Yang, B. Lv, T. Lu, Y. Su and L. Zhou, Catal. Sci. Technol., 2020, Advance Article , DOI: 10.1039/C9CY02376C

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