核壳结构Ni@SiO_(2)催化剂的制备及其在甲烷二氧化碳重整反应中的应用

The Preparation of Core-Shell Ni@SiO_(2) Catalysts and Their Catalytic Performance in Dry Reforming of Methane

采用反相胶束法制备了具有核壳结构的Ni@SiO_(2),经正丁胺碱蒸汽处理及高温焙烧得到壳层重构的Ni@SiO_(2)-B。结构表征表明,氧化镍经碱蒸汽处理转变成硅酸镍,Ni@SiO_(2)-B的壳层限域效应及强的金属-载体相互作用,使得还原后的催化剂具有较小的Ni纳米颗粒尺寸并在长时间反应中予以保持,在700℃和650℃下进行200 h的甲烷二氧化碳重整反应后,Ni@SiO_(2)-B催化剂的甲烷和二氧化碳的转化率以及H_(2)/CO比值保持不变,并且反应后的催化剂几乎无积碳生成,相比Ni@SiO_(2),Ni@SiO_(2)-B催化剂表现出优异的催化性能、抗金属烧结和抗积碳性能。

The core-shell Ni@SiO_(2)catalyst was synthesized via a one-pot reverse phase micro-emulsion method, then treated in 20% n-butylamine steam and calcined at high temperature to obtain reconstructed Ni@SiO_(2)-B catalyst. The catalysts were used in methane dry reforming reaction. The promotion effect of alkali steam treatment on the physicochemical properties of the catalyst was systematically characterized by TEM, XRD, N2adsorption-desorption, ICP-AES, FT-IR, and H_(2)-TPD/TPR techniques. The results show that the precursor of metal active species transform from NiO to nickel silicate after alkali steam treatment. Compared to Ni@SiO_(2), the Ni@SiO_(2)-B catalyst exists smaller Ni particle sizes(3.9 nm) after reduction due to the confinement effect of the core-shell structure and the strong metal-support interaction, leading to better catalytic activity and stability. In the 200 h stability tests at 650 ℃ and 700 ℃, the conversion of methane and carbon dioxide as well as the H_(2)/CO ratio of the Ni@SiO_(2)-B catalyst remain unchanged. Also, Ni@SiO_(2)-B exhibits negligible coke deposition and small growth of Ni nanoparticles, showing excellent resistance to metal sintering and carbon deposition in methane dry reforming reaction.