Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (03): 597-604.doi: 10.3866/PKU.WHXB201301041

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Preparation of Morphology-Tuned γ-MnO2 and Catalytic Performance for the Liquid-Phase Oxidation of Toluene

LIN Jian, CAI Fan, ZHANG Guo-Yu, YANG Le-Fu, YANG Jin-Yu, FANG Wei-Ping   

  1. College of Chemistry and Chemical Engineering, National Engineering Laboratory for Green Chemical Productions of Alcohols, Ether, Esters, Xiamen University, Xiamen 361005, P. R. China
  • Received:2012-09-20 Revised:2013-01-02 Published:2013-02-25
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2010CB226903).

Abstract:

Introducing surfactants including hexadecyltrimethylammonium bromide (CTAB), macrogol 6000 (PEG6000), and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) triblock copolymer (P123) into the refluxing aqueous crystal nucleus slurry yielded morphology-tuned microcrystalline γ-MnO2. γ-MnO2 and the influence of surfactant modification were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption (BET), thermogravimetry analysis (TGA), O2 temperature programmed desorption (O2-TPD), and temperature programmed H2 reduction (H2-TPR). Surfactants led to differences in γ-MnO2 morphology, surface area, oxygen desorption behavior and reducibility. The effect of reflux time on catalyst morphology is discussed. The catalytic performance of γ-MnO2 during the solvent-free atmospheric oxidation of toluene was evaluated. PEG6000 modified γ-MnO2 exhibited the highest catalytic activity judging by surface area because of a greater mixed valency and more anion vacancies. The greatest mass specific activity was obtained for P123 modified γ-MnO2 with the largest surface area. Optimized reaction conditions yielded an 18.1% toluene conversion, and 87.4 and 73.2% total selectivity and selectivity for benzoic acid, respectively.

Key words: γ-MnO2, Selective oxidation of toluene, Morphology tuning, Oxygen species, Surfactant

MSC2000: 

  • O643