物理化学学报 >> 2020, Vol. 36 >> Issue (8): 1905047.doi: 10.3866/PKU.WHXB201905047

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钾改性Mn/Ce0.65Zr0.35O2催化剂催化氧化甲苯

赖潇潇1, 冯洁2, 周晓英1, 侯忠燕1, 林涛1,*(), 陈耀强1,3,*()   

  1. 1 四川大学化学学院,成都 610064
    2 四川大学化学工程学院,成都 610064
    3 四川省环境催化材料工程技术中心,成都 610064
  • 收稿日期:2019-05-13 录用日期:2019-07-02 发布日期:2020-05-19
  • 通讯作者: 林涛,陈耀强 E-mail:lintaochem@scu.edu.cn;chenyaoqiang@scu.edu.cn
  • 基金资助:
    国家重点研发计划(2016YFC0204901)

Catalytic Oxidation of Toluene Over Potassium Modified Mn/Ce0.65Zr0.35O2 Catalyst

Xiaoxiao Lai1, Jie Feng2, Xiaoying Zhou1, Zhongyan Hou1, Tao Lin1,*(), Yaoqiang Chen1,3,*()   

  1. 1 College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
    2 College of Chemical Engineering, Sichuan University, Chengdu 610064, P. R. China
    3 Sichuan Provincial Environmental Catalytic Material Engineering Technology Center, Chengdu 610064, P. R. China
  • Received:2019-05-13 Accepted:2019-07-02 Published:2020-05-19
  • Contact: Tao Lin,Yaoqiang Chen E-mail:lintaochem@scu.edu.cn;chenyaoqiang@scu.edu.cn
  • Supported by:
    National Key Research and Development Program of China(2016YFC0204901)

摘要:

碱金属作为助剂,能够调变催化剂的电子和结构性能,从而改善催化剂的活性。本工作中,我们研究了碱金属K的添加对MnOx/Ce0.65Zr0.35O2催化剂氧化甲苯的性能影响。结果表明,掺杂碱金属K可以明显提高催化剂的催化活性;当K与Mn的摩尔比为0.2时,催化剂Mn/Ce0.65Zr0.35O2-K-0.2表现出最好的活性。在体积空速为12000 h−1时,其完全转化温度T90为242 ℃。同时采用X射线粉末衍射、紫外/可见拉曼、程序升温还原与吸脱附、光电子能谱及红外原位等表征技术研究K的添加对催化剂MnOx/Ce0.65Zr0.35O2性能影响。结果表明,适量K的添加可以提高催化剂的氧化还原性能,增加催化剂表面缺陷位并提高晶格氧的移动性,同时增加了催化剂表面活性氧物种浓度,从而提高催化剂催化氧化甲苯的能力。

关键词: 甲苯, 催化氧化, 钾, 铈锆固溶体, 锰氧化物

Abstract:

Volatile organic compounds (VOCs) are both harmful to human health and the environment; however, catalytic combustion offers a promising method for VOC purification because of its high efficiency without secondary pollution. Although manganese-based catalysts have been well studied for VOC catalytic oxidation, their catalytic activity at low temperature must be improved. Alkali metals as promoters have the potential to modulate the electronic and structural properties of the catalysts, improving their catalytic activity. Herein, a Ce0.65Zr0.35O2 support was prepared by co-precipitation and MnOx/Ce0.65Zr0.35O2 catalysts were obtained through the incipient-wetness impregnation method. The catalytic properties of K-modified MnOx/Ce0.65Zr0.35O2 for toluene oxidation with different molar ratios of K/Mn were investigated. In addition, the catalysts were characterized by XRD, UV/visible Raman, Hydrogen temperature program reduction (H2-TPR), Oxygen temperature programmed desorption (O2-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance FTIR spectroscopy (DRIFTS) experiments. The results showed that alkali metal doping with K significantly improved the catalytic activity. In particular, when the molar ratio of K/Mn was 0.2, the monolith catalyst Mn/Ce0.65Zr0.35O2-K-0.2 exhibited the best performance with the lowest complete conversion temperature T90 of 242 ℃ at a GHSV of 12000 h−1. The XRD results suggested that MnOx was uniformly distributed on the surface of the catalyst and that Mn4+ partially reduced to Mn3+ on the addition of K. The Raman spectrum demonstrated that with increasing K content, both the β- and α-MnO2 phases coexisted on the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst, increasing the number of surface defect sites. The H2-TPR experiment results confirmed that Mn/Ce0.65Zr0.35O2-K-0.2 exhibited the lowest reduction temperature and good reducibility. From the O2-TPD experiments, it was clear that Mn/Ce0.65Zr0.35O2-K-0.2 contained the most surface adsorbed oxygen species and excellent lattice oxygen mobility, which benefitted the toluene oxidation activity. In addition, the XPS results suggested that the content of surface adsorbed oxygen species of the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst was the highest among all the tested samples. In addition, toluene-TPSR in N2 as measured by in situ DRIFTs analysis demonstrated that available lattice oxygen was present in the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst. Therefore, the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst exhibited the best redox properties and oxygen mobility of the prepared samples and showed excellent activity toward toluene oxidation. Therefore, it was concluded that the addition of an appropriate amount of K improved the redox performance of the catalyst and increased the number of surface defect sites and mobility of the lattice oxygen of the catalyst as well as the concentration of the surface active oxygen species, thereby significantly improving catalytic ability.

Key words: Toluene, Catalytic oxidation, Potassium, Ce0.65Zr0.35O2, Manganese oxide

MSC2000: 

  • O643