不同碱土金属氧化物掺杂对纳米二氧化铈催化性能的影响

Effect of the doped alkaline-earth metals on the catalytic performance of CeO_2

通过水热法制备了平均粒径约为20nm的CeO_2,并在纳米CeO_2上引入不同浓度的3种碱土金属氧化物(MgO、CaO和BaO)。催化结果显示在用于催化二氧化碳和甲醇直接合成碳酸二甲酯(DMC)的反应中,此3种碱土金属氧化物均未对纳米CeO_2的催化活性起到促进作用。此外通过透射电镜(TEM)、X射线衍射(XRD)、比表面积及孔分布测试(BET)、X射线光电子能谱(XPS)和程序升温吸附(TPD)对所制备的催化剂进行了表征。研究结果表明,少量的碱土金属氧化物的掺杂不会导致CeO_2晶格变形,而是以无序的形式存在;且碱土金属氧化物的掺杂对纳米CeO_2的形貌、尺寸和织构性质影响不大,对其表面的Ce(Ⅳ)/Ce(Ⅲ)和酸碱性位的数量以及强度有较大影响。此外,较高的Ce(Ⅳ)/Ce(Ⅲ)和较多的酸性位是影响纳米CeO_2催化性能的重要因素。

Nano-CeO2（20nm）was prepared by hydrothermal method,and then alkaline-earth metal oxides（MgO、CaO and BaO）of different concentrations were introduced into the nano-CeO2. The catalytic results showed that the doping of these three alkaline-earth metal oxides all had negative effects on the catalytic performance of nano-CeO2. In addition, the prepared nano-CeO2 were characterized with TEM,XRD,BET,XPS and TPD. The results show that a small amount of doped alkaline-earth metal oxideswere in the form of disorder and they couldn＇t lead to the lattice deformation and showed little effects on the morphology,particle size and textural properties,but they had great effect on the ratio of Ce（Ⅳ）/Ce（Ⅲ） as well as the amount of the acid and base sites. In addition,high ratio of Ce（Ⅳ）/Ce（Ⅲ） and a large amount of acid and base sites are essential for the catalytic performance of nano-CeO2.