镧助剂对模拟生物沼气重整制备合成气中Ni/SBA-15催化剂结构和性能的影响

以介孔分子筛SBA-15为载体, 采用浸渍法制备了镍质量分数(w)为12.5%, 并且分别添加质量分数(w)为2.5%的镧、铈、镁、钙、锶等助剂的系列Ni基催化剂. 以CH4/CO2体积比为2:1的模拟生物沼气和适量氧气作为原料气, 在常压固定床反应器上评价了催化剂对模拟生物沼气重整制合成气的反应性能. 采用X射线粉末衍射(XRD)、N2吸附/脱附、透射电子显微镜(TEM)、X射线光电子能谱(XPS)及H2程序升温还原(H2-TPR)等对催化剂的结构进行了表征. 催化活性评价显示, 添加镧助剂的2.5%La/12.5%Ni/SBA-15催化剂比添加铈、镁、钙、锶等助剂的催化剂具有更高的催化活性, 并且具有很好的稳定性. 因此, 文中着重研究了镧助剂对催化剂结构和模拟生物沼气重整制合成气的反应性能的影响. 结果表明, 镧能明显提高Ni/SBA-15催化剂的表面镍含量, 同时还具有很好的抗积炭作用, 在850 ℃的温度下反应820 h没有发现积炭生成, 这些可能是提高催化剂性能和稳定性的重要因素.

Effect of La Promoter on the Structure and Performance of Ni/SBA-15 Catalyst in the Reforming of Simulated Biogas to Syngas

A series of 12.5%Ni/SBA-15 catalysts, in which 2.5% (mass fraction, w) lanthanum, cerium, magnesium, calcium or strontium was added as a promoter, were prepared by an impregnation method using SBA-15 support. Catalytic performances of the catalysts for the simulated biogas, which consisted of CH4/CO2 with a volume ratio of 2:1, and an appropriate amount of oxygen as a gas feedstock in reforming to syngas, were investigated in a continuous flow reactor under atmospheric pressure. The structures of the catalysts were characterized by X-ray diffraction (XRD), N2-adsorption/desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR) techniques. Results of the activity evaluation indicated that the 2.5% La/12.5%Ni/SBA-15 sample had the highest catalytic activity and stability among the catalysts. Therefore, in this study emphasis was placed on the influence of the La promoter on the structure and performance of the Ni/SBA-15 catalyst in reforming of the simulated biogas to syngas. It was found that lanthanum could significantly increase the surface nickel content in Ni/SBA-15 catalysts and could improve the resistance to carbon deposition. At 850 ℃, after reacting for 820 h, no carbon was observed on the catalyst, which might be an important factor for the improvement of catalytic activity and stability.