ZrO_2催化剂上吸附CH_3NO_2的分解

Decomposition of Nitromethane Adsorbed on ZrO2 Catalyst

用TPD和IR谱研究了CH_3NO_2在ZrO_2催化剂上的吸附活化和分解反应。结果表明,室温下CH_3NO_2在ZrO_2表面发生不可逆化学吸附,它们在TPD过程中可完全分解生成HCN、CO_2、CO、NH_3、H_2O和微量NO。其中H_2O和NO的脱附峰出现在383K附近。其它产物在543K附近出现极大值。IR结果表明,CH_3NO_2在ZrO_2上吸附形成诸如[CH_2NO_2],和/或吸附物种。这些吸附物种在升高温度时转化为表面态“HCN”。“HCN”或脱附,或进一步向表面“HCONH_2”和/或“HCOO^-”转化,后两种表面物种分解可产生CO_2、NH_3和CO。将这些结果与CH_3NO_2在SiO_2-Al_O_3和MgO催化剂上的结果进行了比较,讨论了酸-碱双功能性ZrO_2催化剂上CH_3NO_2活化分解的特点。

The adsorption and decomposition of CH3NO2 on ZrO2 were studied by means of temperature-programmed-desorption (TPD) and infrared spectroscopy (IR). It is shown that the surface species produced by CH3NO2 adsorbed at room temperature are all of irreversibly chemisorbed ones. They are decomposed, on raising the desorption temperature, to HCN, CO2, CO, NH3, H2O and trace of NO. The evolution H2O and NO products occurs at about 383 K, while evolution of the other products shows a maxima at about 543 K. The surface species observed in the IR spectra may be assigned to [CH2NO2]-, monodentate CH3-N-O-Zr and/or Zr-CH2-N-O-Zr (1600,1250cm-1).Transformation of these adspecies to surface 'HCN'(2320- 2350 cm-1) , formamide and/or formate (1620, 1560-1540, 1370, 1440 cm-1) species are observed at higher temperatures. On heating up to higher than 473 K, the formamide and/or formate species decompose to CO2, CO and NH3. These results are compared with those from CH3NO2/MgO and CH3NO2/SiO2-Al2O3, and discussed in relation to the acid-base properties of the catalyst.