Chinese Journal of Catalysis ›› 2017, Vol. 38 ›› Issue (3): 518-528.DOI: 10.1016/S1872-2067(17)62767-0

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One-pot synthesis of ordered mesoporous Cu-KIT-6 and its improved catalytic behavior for the epoxidation of styrene: Effects of the pH value of the initial gel

Baitao Li, Xin Luo, Jing Huang, Xiujun Wang, Zhenxing Liang   

  1. Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, Guangdong, China
  • Received:2016-11-12 Revised:2016-12-20 Online:2017-03-18 Published:2017-03-22
  • Supported by:

    This work was supported by Guangdong Science and Technology Planning Project (2015A020216002), Guangdong Natural Science Foundation (2014A030313259), and the National Natural Science Foundation of China (21543014, 21173086, U1301245).

Abstract:

The heterogeneously copper-catalyzed oxidative cleavage of styrene was studied using copper-doped mesoporous KIT-6 (Cu-KIT-6x) prepared via pH adjustment (where x is the pH: 1.43, 2.27, 3.78, 3.97, 4.24 or 6.62). Variations in the catalyst structure and morphology with pH values were characterized by X-ray power diffraction, nitrogen adsorption-desorption analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. As the pH value applied during the initial synthesis, the resulting Cu-KIT-6x exhibited different structural, textural and surface characteristics, especially in terms of specific copper species and copper content. At a pH value of 3.78, approximately 4.6 wt% copper(II) was successfully incorporated into the framework of the initial KIT-6, in the form of -Cu-O-Si- groups. The catalytic performance of each catalyst was evaluated by following the epoxidation of styrene, employing tert-butyl hydroperoxide as the oxidant and CH3CN as the solvent. A significant styrene conversion of 43.5% with 86.6% selectivity for the desired styrene epoxide was obtained over the Cu-KIT-63.78. A higher Cu content, an ordered cubic Ia3d mesoporous architecture and various specific textural characteristics all combined to endow the Cu-KIT-63.78 with high catalytic activity and good stability.

Key words: Mesoporous material, KIT-6, Styrene epoxidation, pH-adjusting