低Ni含量和低比表面积六铝酸盐LaNiAl_(11)O_(19-δ)催化剂上CH_4-CO_2重整反应的积炭

Carbon Deposition on Hexaaluminate LaNiAl_(11)O_(19-δ) Catalyst with Low Nickel Content and Low Specific Surface Area

利用X射线粉末衍射、氢程序升温还原、X射线光电子能谱和透射电镜技术研究了在低Ni含量和低比表面积六铝酸盐催化剂LaNiAl11O19-δ上CH4-CO2重整反应的积炭行为,考察了该催化剂表面积炭的形貌、来源、积炭物种及其反应性能.结果表明,LaNiAl11O19-δ催化剂表面积炭主要由甲烷裂解产生,并以Ni的碳化物形式存在于活性中心Ni的周围.根据积炭物种活化程度的难易可分为Cα,Cβ和Cγ三种类型,其中Cα为容易被CO2消除的化合碳,而Cβ和Cγ则是不易被CO2消除的石墨碳.透射电镜结果表明,Cα以碳纳米管形式分布于催化剂颗粒周围,但金属Ni活性中心仍能暴露于气相中,因而不影响催化剂的活性.

Carbonaceous deposits formed during the reaction of CO2 reforming of methane over hexaaluminate LaNiAl11O19-δ catalyst and their reactivity were studied by X-ray diffraction, H2-temperature-programmed reduction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The deposited carbon was mainly originated from CH4 decomposition, and it could be classified as three kinds of surface carbon species, i.e. Cα, Cβ, and Cγ species on LaNiAl11O19-δ. The carbide carbon, Cα, was very active and could be eliminated by CO2 easily. However, both Cβ and Cγ were the graphitic carbon and were difficult to be eliminated by CO2. It was suggested that Cα was a kind of nanotube-like carbon, which did not affect the catalytic activity of hexaaluminate LaNiAl11O19-δ catalyst.