碳酸二甲酯在锌铝复合氧化物上分解行为的红外研究

In-situ IR study of thermal decomposition of dimethyl carbonate over Zn /Al mixed oxide catalysts

采用尿素热分解法制备锌铝水滑石,1 073 K下煅烧得到相应的锌铝复合氧化物催化剂。通过XRD谱图确定锌铝复合氧化物ZAO-3(1 073 K)催化剂的组分为ZnO相和ZnAl2O4尖晶石相。NH3(CO2)-TPD结果表明,当向ZnO中引入Al后,催化剂的酸碱性位和酸碱性强度都发生改变。采用原位红外(in-situ FT-IR)手段,研究了碳酸二甲酯(DMC)分别在ZAO-3(1 073 K)、ZnAl2O4、ZnO上随着温度变化的分解行为。结果表明,ZAO-3(1 073 K)催化剂上大量的弱酸碱性位协同稳定DMC,抑制DMC的分解。

ZnO, ZnAl2O4 and Zn/Al mixed oxide catalysts were prepared by thermal decomposition of hydrotalcite-like layered precursors derived from urea precipitation at 1 073 K. Both ZrtAl2 04 and ZnO phases were observed in ZAO-3 catalyst at 1 073 K from XRD patterns. The NHa-TPD and CO2-TPD results revealed that the acidity and basicity of Zn/Al mixed oxide catalysts changed with the introduction of Al. Combined with the in-situ PT-IR results of dimethyl carbonate （DMC） decomposition over ZAO-3 （ 1 073 K）, ZnAl204, ZnO at various temperatures, it was found that the synergistic effect between acidic and basic sites over ZAO-3 （ 1 073 K） could stabilize DMC molecules and inhibit the decomposition of DMC.