RCEES OpenIR  > 环境纳米技术与健康效应重点实验室
稀土基复合氧化物上H2S 选择 催化氧化反应过程的研究
Alternative TitleSelective catalytic oxidation of H 2 S over rare earth based oxide catalysts
张凤莲
Subtype博士
Thesis Advisor郝郑平
2019-12
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name工学博士
Degree Discipline环境工程
Keyword稀土催化剂 水滑石,钙钛矿, 硫化氢 选择氧化, 反应机理 rare Earth Catalysts , Layered Double HydrOxides Perovskite Oxides, h 2 s Selective Oxidation , Reaction Mechanism
Abstract

       近年来我国经济高速增长,综合国力日益增强,石油、天然气工业和煤化工行业得到高速发展,含硫原油加工量和酸性天然气处理量也相应增加。 特别是高硫原油进口的增多,以及大量含硫燃料油的深度加工及煤制气等工艺使得副产的含硫化氢( H 2 S )酸性气也越来越多。另一方面,为适应经济迅速发展的形势和国家发展战略的变化,我国对环境保护的要求也日趋严格,新颁布的 排放标准要求硫磺回收装置的总硫回收率要达到 9 9.97 %%~ 。然而,作为硫磺回收主流技术的克劳斯( Cl aus )工艺,受到反应温度下化学平衡限制,即使是采用活性良好的催 化剂和三级转化器,也只能达到 9 7 左右的硫回收率,尾气中尚有 1 %~ 的 H 2 S 未被转化,需作进一步处理以满足日益严格的环保要求。为此,尾气处理技术得到迅速发展,这其中选择催化氧化技术由于不受热力学限制而得到广泛关注与应用。研究和开发低成本、高活性、高选择性和稳定性的 H 2 S 选择氧化催化剂是目前选择催化氧化技术发展的关键和重要研究课题。

      本论 文针对 H 2 S 选择氧化反应的特点,引入稀土元素,设计并制备了高效稀土基复合氧化物催化剂体系,系统地研究了稀土基催化剂及稀土复合过渡金属催化剂上 H 2 S 选择氧化性能,以及添加稀土对其选择氧化性能的影响和规律。采用拉曼光谱( Raman )、氮气吸脱附、粉末 X 射线衍射( X RD )、电子顺磁共振( E PR )、 X 光电子能谱( X PS )、程序升温还原 T PR )、程序升温脱附 T PD等技术手段表征了催化剂的结构特征与物化性质,研究分析了催化剂与催化活性的构效关系,阐明了催化剂的反应过程及机理,得到的主要结果及结论如下:
      1、稀 土 Ce 基 Mg A l CeO x 水滑石衍生复合氧化物催化剂体系采用改进的一步合成法
       合成了一系列不同 Ce 含量的 MgAlCe O x 水滑石衍生复合氧化物。该 催化剂 材料表 面同时 存在 有利于氧活化的 化学吸附氧空位 和有利于氧物种移动的 Frenkel type 型 氧 缺陷 。 催化剂在较低温度表现出了较好的H 2 S 的选择氧化活性和超高的硫选择性( 100%100%)。反应机理为 Ce 4+4+/Ce 3+ 的氧化还原机理,催化剂失活的主要原因是 硫酸盐的生成,使 Ce 3 难以被氧化成 Ce 4 。此外, 水气 的加入会对催化剂的活性产生抑制作用 主要是因为水的存在会改变催化剂的表面性质,导致硫 的存在形式从具有弱催化活性的 S 8 转变成低催化活性的 S 3 ,从而 使 催化剂表面 S 8 以及活性位减少, 导致 催化剂活性 下降 。
      2. 稀土 Ce 取代 La 1 x Ce x FeO 3 钙钛矿复合氧化物催化剂体系采用柠檬酸络合的溶胶
       凝胶法合成了一系列稀土 Ce 取代的 La 1 x Ce x FeO 3钙钛矿 复合氧化物 催化剂 。 该催化剂在 H 2 S 的选择催化氧化中表现出了优异的催化性能 、 超高的稳定性 72 h )及超低的反应活化能 。 催化剂中 Ce 和 Fe 主要以 La CeFeO 3 钙钛矿型氧化物和 Ce Fe 固溶体的形式存在。适当的 Ce 取代可以 改善催化剂的表面碱性,促进催化剂表面 氧空位的形成,从而增强催化剂对H 2 S 的吸附性能和晶格氧移动性,同时 Ce Fe 的协同作用大大提高了催化剂的还原能力。反应遵循氧化还原的机理,催化剂的失活主要是由于硫酸盐的形成,此外,水气的加入会促使 Cl aus 逆反应的建立,致使催化剂的催化性能下降。
       3.稀土 La 2 FeMeO 6 Me =Mn 、 Co 、 V 、 Mo 双钙钛矿复合氧化物催化剂体系
       采用柠檬酸络合的溶胶 凝胶法合成了一系列 稀土 L a 2 FeMeO 6 M e=Mn 、C o 、 V 、 M o )双钙钛矿复合氧化物 。引入 Mn 、 Co 可分别形成单一 的 La 2 FeMnO 6 、La 2 FeCoO 6 双钙钛矿相,其中 Fe 、 Co 、 Mn 均以 3 价存在,而引入 V 、 Mo 则分别形成 L a VO 4 、 La 2 Mo 2 O 9 与 La FeO 3 钙钛矿相的混合相,其中 V 、 Mo 、 Fe分别以 V 5 、 Mo 6+ 、 Fe 3+ 的形式存在。 B 位第二金属的引入并没有改变 Fe 的价态,但 B 位金属的分布会影响 Fe 周围的化学环境。其中 La 2 FeMnO 6 催化剂由于形成晶型较好的立方双钙钛矿晶型, Mn Fe 交替排列,形成 Mn 3+ O F e 3+ 的有序排列, Mn Fe 的协同作用使得该催化剂在低温下表现出优异的低温活性。La 2 FeV O 6 催化剂由于 V 5 活性物种的存在,该催化剂也表现出优异的低温催化活性。此外,引入少量的水气,由于 H 2 O 与 H 2 S 竞争吸附并覆盖活性位致使H 2 S 转化率下降,而引入大量水气则导致 Cl aus 逆反应的建立,造成催化剂 H 2 S转化率及硫选择性均下降。

Other Abstract

       Recent years, the economy of China and its comprehensive national strength has been growing ra pidly Accordingly, o il and natural gas industry and coal chemical industry have been develop ed rapidly as well. Meanwhile, sour crude oil and sour natural gas processing capacity accordingly increased. In particular, the increase in imports of high sulfur crude oil, as well as the deep processing of a large amount of sulfur containing fuel oil and coal gasification processes have led to the increasing production of H 2 S containing acid gas. On the other han d, in order to adapt to the rapid development of ec onomic and the transition of national development strategy, the environmental regulations are increasingly stri ngent. The new emission standard require s the total sulfur recovery efficiency of the sulfur recovery units to reach 99.97%~99.99%. However, the C laus process, as the main technology of sulfur recovery, is limited by the thermodynamic limitation . Even if effective catalyst s and three stage catalytic conversion are adopted, the sulfur recovery efficiency is typically limited to 97%. There are still 1%~3% H 2 S in tail gas that have not been converted, and further treatment is needed to meet tighter pollution control Hence , tail gas treatment technology has been de veloped quikly ,among which catalytic oxidation technology is the most attractive solutio n as it can directly and completely convert H 2 S to elemental sulfur Research and development
of H 2 S selective oxidation catalysts with low cost, high activity, high s electivity and stability is a key and important research topic in the development of sele ctive catalytic oxidation technology.
        In view of the characteristics of H2 S selective oxidation reaction rare earth elements were introduced and efficient rare earth based oxide catalyst s were designed and prepared . T he selective oxidation performance of H 2 S on rare earth based oxide catalyst and the influence of the rare earth on the selective oxidation catalytic performance were systematically studied . The structure texture,physic chemical properties of the catalysts were characterized by the combinati on techniques of Raman spectroscopy (Ra man), N 2 adsorption desorption measurement ,powder X ray diffraction (XRD), electron paramagnetic resonance (EPR), X ray photoelectron spectroscopy (XPS), H 2 temperature programmed reduction ( H 2 TPR),temperature prog rammed desorption ( The structure activity relationship between catalyst s and catalytic activity were analyzed . Particularly, t he reaction process and mechanism were proposed. The main findings and conclusions are asfollows.
       (1)Rare earth Ce con tain ing MgAlCeO x oxide catalysts derived from layered double hydroxides
       A series of well mixed Ce containing MgAlCe O x rare earth catalysts derived from layered double hydroxides were synthesized using modified one step method . Particularly, both chemisorptio n O vacancies and F renke l type defect sites were present on catalyst surface , which would facilitate the oxygen activation and lattice oxygen mobility . Significantly, the catalysts exhibited excellent catalytic activity,reasonable durability, and outstand ing sulfur selectivity (100%) at relatively low temperatures. Furthermore, the catalyst followed a step wise mechanism, and the
catalyst deactivation was due mainly to the formation of sulfate species, result in tough oxidation of Ce 3+ to Ce 4+4+. Particularl y, the added water, a Lewis base, can compete with inefficient S 8 catalyst for the occupation of Lewis acid sites and active sites. Meanwhile, it can change the characteristics of catalyst surface, resulting in sulfur existing form transforming from ineffi cient S 8 catalyst to i nactive S 3 Thus,lead to a decrease of deposited inefficient S 8 catalyst content. Consequently, decrease the catalytic activity.
       (2)Rare earth Ce substituted La 1 x Ce x FeO 3 perovskite oxides catalyst 
       A series of La 1 x Ce x FeO 3 perovski te catalysts were synthesized using a citrate sol gel method. It was demonstrated that the catalysts exhibited prominent catalytic activity, outstanding sulfur selectivity (nearly 100%) and particularly low apparent activation energy. Remarkably, it can pr oceed consecutively for 70 h without notable deactivation. Moreover, Ce and Fe were mainly existed in the form of LaCeFeO 3 perovskite type oxides as well as Ce Fe solid solution. Significantly, catalysts reducibility was improved greatly due to the strongl y Ce Fe synergetic effect. More importantly, a proper substitution of Ce can enhance surface basic properties and facilitate the formation of oxygen vacancies on the catalyst surface, and hence improve H 2 S adsorbability and lattice oxygen mobility , respect ively. It cooperating with the improved reducibility jointly contributed to the excellent catalytic performance. Furthermore, the reaction obeyed a redox mechanism and the catalyst deactivation was due mainly to the formation of sulfate species. A dditional ly, the added water can lead to the establishment of the reverse Claus reaction, causing the decrease of catalytic performance.
      (3)Rare earth La 2 FeMeO 6 (M e =Mn, C o , V, Mo) double perovskite oxides catalyst
       A series of rare earth La 2 FeMeO 6 ( Mn, Co, V, M o ) double perovskite oxides catalysts were synthesized using a citrate sol gel method. Monophasic crystalline La 2 FeMnO 6 and La 2 FeCoO 6 double perovskite s were obtained by the incorporation of Mn and Co, wherein Fe, Co and Mn all exist ed in the f orm of posit ive trivalent . However, when introduction of V and Mo into the LaFeO 3 structure, a mixed crystal phase of LaFeO 3 perovskite phase and LaVO 4 , La 2 Mo 2 O 9 were observed, wherein Fe, Mo and V existed in the form of V 5+5+, Mo 6+ and Fe 3+ The incorporation of the se cond metal in B site does not change the valence of Fe while the nature of the metal and its distribution will influence chemical environment around iron. Moreover, La 2 FeMnO 6 formed a cubically ordered double perovskite
compoun d, in which Mn Fe is alterna tely arranged to form Mn 3+ O Fe 3+ ordered arrangement. D ue to the enhanced Mn Fe synergistic effect, La 2 FeMnO 6 exhibited excellent catalytic activity at low temperature . In addition, La 2 FeVO 6 catalyst showed excellent low temperature catalytic activity asc ribed to the presence of V 5+active species. In addition, the introduction of a small amount of water vapor would decrease the H 2 S conversion, which is resulted from the competitive adsorption of H 2 O with H 2 S and coverage of active sites by H 2 O. while, the introduction of large amount of water vapor lead ed to the establishment of Claus reverse reaction,resulting in the decrease of both H 2 S conversion and sulfur selectivity

Pages132
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42344
Collection环境纳米技术与健康效应重点实验室
Corresponding Author张凤莲
Recommended Citation
GB/T 7714
张凤莲. 稀土基复合氧化物上H2S 选择 催化氧化反应过程的研究[D]. 北京. 中国科学院生态环境研究中心,2019.
Files in This Item:
File Name/Size DocType Version Access License
张凤莲-稀土基复合氧化物上H2S选择催化(4476KB)学位论文 开放获取CC BY-NC-SAApplication Full Text
Related Services
Recommend this item
Bookmark
Usage statistics
Export to Endnote
Google Scholar
Similar articles in Google Scholar
[张凤莲]'s Articles
Baidu academic
Similar articles in Baidu academic
[张凤莲]'s Articles
Bing Scholar
Similar articles in Bing Scholar
[张凤莲]'s Articles
Terms of Use
No data!
Social Bookmark/Share
All comments (0)
No comment.
 

Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.