【作者】 叶季蕾；

【导师】 刘源；

【作者基本信息】 天津大学 ， 工业催化， 2008， 博士

【摘要】 乙醇水蒸气重整制氢的技术核心是催化剂。目前报道的催化剂需要克服的主要问题是提高乙醇水蒸气重整反应（SRE）的低温活性以及催化剂的稳定性。镍系催化剂由于活性高、成本低的特点而备受关注,但抗烧结和抗积碳能力有待进一步提高。铈基氧化物具有储-释氧能力并可与活性组分产生相互作用,调节活性组分的化学状态和有利于积炭的氧化消除,从而提高催化剂的稳定性。本文探索并研究了一系列Ce-M-O负载的镍催化剂用于乙醇水蒸气重整反应中,表现了高活性、高选择性以及较高的稳定性。分析了不同的载体上镍活性组分的状态、与载体的相互作用及其和乙醇水蒸气重整反应催化性能的关系。采用了柠檬酸络合法制备Ni/Ce_0.5Zr_0.5O₂催化剂用于SRE反应,考察了制备条件（制备方法、焙烧温度、镍含量）和反应条件（反应空速）对催化性能的影响。Ni/Ce_0.5Zr_0.5O₂催化剂中与载体有强相互作用的NiO还原出来的NiO是乙醇重整反应的关键活性组分,这部分镍物种晶粒小,且与载体相互作用强,改善了催化剂的低温活性、选择性和抗烧结性能。铈锆固溶体的形成,大大提高了体相氧的活动能力,提高了催化剂的抗积碳性能。TG-DTA和XRD结果也表明催化剂具有很好的抗烧结和抗积碳性能,是一种很有应用前景的催化剂。浸渍法制备的Ni/CeO₂-TiO₂催化剂在SRE中呈现出良好的催化性能。制备条件中NiO含量、铈钛比、焙烧温度影响催化剂的物相组成、活性组分与载体间的相互作用。10%Ni/Ce_0.5Ti_0.5O₂-700催化剂在SRE中表现了最佳的催化性能。该催化剂中NiTiO3还原出来的Ni0是SRE反应的关键活性组分,NiTiO₃还原出来的Ni0晶粒小,高分散且不易聚集;固溶体Ce-O-Ti的形成大大提高了载体的氧活动能力,这两个因素使得10%Ni/Ce_0.5Ti_0.5O₂-700催化剂在SRE反应中呈现出高活性和高稳定性。采用了不同方法制备了新型Ni/La-Ce-O催化剂,结果表明不同方法制备的Ni/La-Ce-O催化剂各组分之间的相互作用不同,对催化剂的性能有很大影响。柠檬酸法制备的催化剂中形成更多的镧铈固溶体,同时镍与La-Ce-O载体相互作用较强,在SRE反应中表现了更高的抗积碳能力。初步分析了该催化剂上可能进行的SRE反应途径。比较了Ni/Ce-M-O催化剂的结构和性能,结果表明Zr、Ti或La的添加均有效地提高了NiO的分散度、与载体的相互作用以及载体的氧化还原能力,但作用机理不尽相同。更多还原

【Abstract】 The crucial issue for hydrogen production by steam reforming of ethanol （SRE） is to develop efficient catalysts. The critical challenge for SRE catalysts is to improve stability and low temperature activity. CeO₂-based oxides are characterized with good oxygen-storage capacity and tend to interact with active component, which is beneficial for eliminating carbon and adjusting chemical nature of active component. In this work, a series of Ni/Ce-M-O （M=Zr, Ti or La） catalysts for SRE were studied, which exhibited high low temperature activity and good stability for SRE. The relation between catalyst structure and catalyst performance was also investigated.The Ni/Ce_0.5Zr_0.5O₂ catalysts were prepared by citric complexing method. The effects of preparation conditions and reaction conditions on catalytic performance were investigated. The results indicated that 20%Ni/Ce_0.5Zr_0.5O₂-700 catalyst was very active and selective at low reaction temperature under the space velocity of 160,000ml·h^-1·gcat^-1 and the metal nickel reduced from NiO in strong interaction with support is the key active species. TG-DTA and XRD results show that 20%Ni/Ce_0.5Zr_0.5O₂-700 catalyst exhibits high anti-sintering and good carbon-resistance quality.Ni/CeO₂-TiO₂ catalysts prepared with impregnation method showed good catalytic performance for SRE. Experimental results indicate that the content of nickel, the molar ratio of Ce/Ti and calcination temperature have influence on catalysts phase structure and the interaction between Ni species and support, and thus affect catalytic performance obviously. The high activity of Ni/CeO₂-TiO₂ catalysts is ascribed to the metal nickel reduced from NiTiO3, which is highly dispersed with good anti-sintering ability. The good stability for carbon deposition resistance of this catalyst is mainly attributed to the formation of Ce-O-Ti solution which can improve oxygen mobility in the support. Among the catalysts tested in this series, 10%Ni/Ce_0.5Ti_0.5O₂-700 exhibits the best catalytic performance.The 10%Ni/La-Ce-O catalyst prepared by citric acid method shows comparatively good carbon-resistance ability at 450℃due to its high redox capability, which was originated from the formation of La-Ce-O solid solution and the interaction between nickel species and carrier. The possible reaction pathways over 10%Ni/La-Ce-O are proposed. By comparison, the addition of Zr, Ti or La has effectively improved the dispersion of NiO, the interaction between active species and support and the redox capability of CeO₂, which results in the improvement of catalytic performance of Ni/CeO₂ catalyst for SRE. The forms of nickel species in Ni/Ce_0.5Zr_0.5O₂ and Ni/Ce_0.55La_0.45O_x catalysts are similar, but the different proportion of various nickel species in two catalysts leads to a big change of products selectivity in SRE. The high activity for SRE of Ni/Ce_0.5Ti_0.5O₂ catalyst originated from metal nickel reduced from small particle NiTiO3. In addition, experimental results indicate that Ni/Ce_0.5Zr_0.5O₂ and Ni/Ce_0.5Ti_0.5O₂ catalysts are fit for high temperature reaction and that Ni/Ce_0.55La_0.45O_x catalyst prefers to be applied in low temperature.更多还原