钒插层类水滑石衍生复合氧化物上H2S选择催化氧化过程的研究
文献类型：学位论文
| 作者 | 张鑫 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 郝郑平 |
| 关键词 | 煤化工 H2S 选择氧化 类水滑石 衍生复合氧化物 Coal chemical industry H2S selective catalytic oxidation Layered Double Hydroxides Derived composite oxides |
| 其他题名 | Selective Catalytic Oxidation of H2S overWell-mixed Oxides Derived fromVanadium Contained LDHs |
| 学位专业 | 环境工程 |
| 中文摘要 | 随着社会的发展煤化工行业正在起着越来越重要的作用，但是在煤化工的生产过程中会产生大量的含硫废气，由于Cluas 反应受到热力学平衡的限制，仍有2-3%的H2S 残留在Claus 尾气中，随着环境法规的日益严格和硫磺资源的短缺，多种技术被开发和应用到Claus 尾气脱硫中。在这其中H2S 选择氧化技术得到了最为广泛的应用，本论文利用一种简便的方法合成了含钒类水滑石前驱物，焙烧后得到了相应的衍生复合氧化物催化剂。采用XRD、TG-DTG、N2 吸脱附、XPS、TPR/TPD、FT-IR 等技术手段表征和考察了催化材料的结构特征和影响催化剂性能的主要因素，并研究了其催化性能，阐明了催化剂的催化机理，得到的主要结果和规律性认识如下： 1.钒插层层板间的Mg2AlxV1-xO催化剂体系 利用简便的一步法成功合成了钒插层层板的Mg2AlxV1-x-Cl-LDH 材料，在空气气氛下550 °C 焙烧得到了相应的衍生复合氧化物。催化剂材料中钒物种主要以[VO4]和Mg3V2O8 形式存在，同时存在少量的V4+物种。催化剂能够在180 °C，高空速的条件下表现出较好的催化活性和一定的稳定性，催化剂的催化机理为H2S 首先被吸附在催化剂表面的中度碱性位后，然后被V5+氧化成硫单质。催化剂的失活主要是由于在反应过程中生成了大量的VO2+和Mg3V2O8 物种，从而导致了催化剂表面碱性位的减少。同时形成的少量的低活性的VOSO4 物种也能导致催化剂的失活。 2.钒插层层板间的Mg2AlVO催化剂体系 利用两步离子交换法成功合成了钒插层阴离子层间的Mg2Al-V10O28-LDH 材料，在空气气氛下550 °C 焙烧得到了相应的衍生复合氧化物。催化剂材料中钒物种主要以[VO4]和a-Mg2V2O7 形式存在，同时存在大量的V4+物种。催化剂材料表面的碱性位没有发生明显的变化，但是在催化剂表面存在有大量的化学吸附氧空位。催化剂能够在160 °C，高空速的条件下表现出优异的催化活性和一定的稳定性。钒氧键的长度决定了催化剂的硫选择性；a-Mg2V2O7 物种的存在有利于氧化反应的进行。催化剂的失活主要是因为钒被H2S 还原的速率小于被氧气氧化的速率，大量形成的长键长的钒氧键导致了催化剂硫选择性的降低。同时单质硫物种的沉积以及低活性VOSO4 物种的形成也导致了催化剂的失活。 3.不同钒物种和碱性性质的影响 利用两步离子交换法合成钒交换量为8%的Mg2Al-V10O28-LDH 材料，在空气气氛、不同温度下焙烧得到了相应的衍生复合氧化物。随着焙烧温度的升高催化剂中钒物种的存在形式也逐渐发生变化。Mg2AlVO-50 催化剂在160 °C 表现出了最佳的催化活性。研究表明[VO4]和a-Mg2V2O7 物种的存在有利于H2S 的转化；而V4+和Mg3V2O8 物种的存在有利于催化剂硫选择性的增加。当水滑石前驱物中的层间阴离子不同时，钒交换后会对催化剂表面的酸碱性质和钒物种的存在形式有较大的影响，Mg2AlVO-SO4 催化剂的表面酸碱性位大量减少且孔结构坍塌。催化剂的活性随着表面碱性位的变化而变化，Mg2AlVO-NO3 催化剂因表面拥有最多的碱性位而表现出了最佳的催化活性和较差的硫选择性，Mg2AlVO-SO4催化剂因表面碱性位的大量减少而表现出了较差的催化活性和最好的硫选择性。 4.M2AlVO(M=Cu、Zn、Ni)催化剂体系 利用两步离子交换法成功合成了钒插层的不同二价金属的M2Al-V10O28-LDH（M=Zn、Cu、Ni）材料，在空气气氛下550 °C 焙烧得到了相应的衍生复合氧化物。催化剂材料中钒物种的存在形式因二价金属的不同而发生改变，Zn2AlVO 和Ni2AlVO 催化剂中Zn、Ni 和V 的协同作用使得钒物种在较低温度下便表现出了活性，从而在140 °C 便产生了催化活性，且其活性相为各种形式存在的V5+。Cu2AlVO 催化剂中由于Cu 的抑制作用，催化剂表现出了较差的催化活性。Zn2AlVO 催化剂在140 °C 时便获得了最佳的硫产率。 |
| 英文摘要 | Coal chemical industry is playing a more and more impotant role in society due to the energy shortage. However, sulfur contained waste gas can be released in the process, and almost 2-3% H2S is left after Claus process treatment. Various additional purification processes have been used to treat the Claus tail gas. Among them, the selective catalytic oxidation technique has been of great research interest in recent decades and this process strongly depended on the catalyst. In our thesis, vanadium contained LDHs were synthesized by using a facile method and the derived oxide catalysts can be obtained by calcination of precursors. The catalyst physicochemical properties were extensively characterized and elucidated by various techniques(XRD,TG-DTG, N2 adsorption/desorption, XPS, TRR/TPD, and FT-IR). Moreover, the catalytic performances were test and the catalytic mechanism was explored in detailed.The main research results are listed as follows: 1.Vanadium intercalated into brucite layer Mg2AlxV1-xO catalysts A series of vanadium intercalated into brucite layer Mg2AlxV1-x-LDH was synthesized by using a facile method, and the derived oxides were obtained by calcining the precursor in air at 550 °C. It was observed that vanadium species mainly existed in form of isolated V5+ in distorted [VO4]，Mg3V2O8 and VO2+. Significantly,the catalysts exhibited high catalytic activity and reasonable durability in high space velocity at 160 °C due to the well-dispersed vanadium species and excellent moderate basicity property. The catalytic reaction mechanism over these catalysts was proposed as follow: H2S was firstly adsorbed on the Mg-O-Mg band of MgO (moderate basic sites) forming S2- and H2O. Then, the S2- is oxidized to Sn by V5+. Additionally, the catalyst deactivation was mainly due to the decrease of moderate basic sites. Moreover, the formed less active VOSO4 also contributes to the catalyst deactivation. 2. Vanadium intercalated into anion layer Mg2AlVO catalysts A series of vanadium intercalated into anion layer Mg2Al-V10O28-LDH was synthesized by ion exchanged method and the derived oxides were obtained after calcined. It was observed that vanadium species mainly existed in form of isolated V5+ in distorted [VO4]，a-Mg2V2O7 and V4+. Besides, the content of moderate basic sites almlost kept consistent with the increase of vanadium content. However, the chemical adsorbed oxygen vacancies were enhanced significantly, which is beneficial to the oxidation reaction. The catalytic performances revealed that the catalysts exhibited high catalytic activity and excellent durability in high space velocity at 160 °C. And, the sulfur selectivity of the catalysts was mainly depended on the length of V=O. The the catalysts deactivation was mainly due to the slower oxidation rate of the V5+ by oxygen as compared to the reduction rate of V4+ by H2S, the large amount of V4+ caused the decrease of sulfur selectivity. Simultaneously, the formation of less active VOSO4 and elemental sulfur deposition also contributed to the catalyst deactivation. 3. Influences of different vanadium species and interlayer anions The influences of different vanadium species and interlayer anions were investgated indetailed. It was observed that the existence form of vanadium specises changes with the rise of calcined temperature. Mg2AlVO-550 catalyst exhibited the best catalytic performance. It indicated that [VO4] and a-Mg2V2O7 species were beneficial to the H2S conversion and the sulfur selectivity mainly depended on V4+and Mg3V2O8 species. On the other hand, the catalysts presented remarkably different properities when the LDHsmaterials with different interlayer anions. For Mg2AlVO-SO4 catalyst, the content of moderate basic sites decreased sharply and the pore structure cllapsed. Mg2AlVO-NO3 catalysts exhibited the best catalytic activity and poor surlfur electivty due to the large amount of mederate basic sites. Mg2AlVO-SO4 catalyst exhibited poor catalytic performance. 4. M2AlVO (M=Zn、Cu、Ni) catalysts Vanadium intercalated anion layer M2Al-V10O28-LDH (M=Zn 、Cu 、Ni) with different M2+ were synthesized by ion exchanged method and the derived oxides were obtained after calcined. It seemed that the existence form of vanadium species were different with each other because of the different M2+. The catalytic performances revealed that the Zn2AlVO and Ni2AlVO catalysts exhibited excellent catalytic activities in relatively lower temperature (140 °C) due to the synergistic effect of Zn and Ni with vanadium species.And the V5+ species existed in various form played key role in H2S conversion. Nevertheless, the Cu2AlVO catalyst presented catalytic activity in rather higher temperature due to the inhibiting effect of Cu species. Furthermore, Zn2AlVO catalyst presented the highest sulfur yield at 140 °C. |
| 公开日期 | 2015-06-15 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/13465]  |
| 专题 | 生态环境研究中心_环境纳米材料实验室 |
| 推荐引用方式 GB/T 7714 | 张鑫. 钒插层类水滑石衍生复合氧化物上H2S选择催化氧化过程的研究[D]. 北京. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：生态环境研究中心
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。