物理化学学报 >> 2023, Vol. 39 >> Issue (9): 2210038.doi: 10.3866/PKU.WHXB202210038

所属专题: 能源与环境催化

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雷淦昌1,2, 郑勇1,2, 曹彦宁1,2, 沈丽娟1,3,*(), 王世萍1,2, 梁诗景1,2, 詹瑛瑛1,2,*(), 江莉龙1,2,*()   

  1. 1 福州大学石油化工学院, 化肥催化剂国家工程研究中心, 福州 350002
    2 中国福建化学工程科学与技术创新实验室, 清源创新实验室, 福建 泉州 302801
    3 福建师范大学环境与资源学院、碳中和现代产业学院, 福建省污染控制与资源循环利用重点实验室, 福州 350007
  • 收稿日期:2022-10-27 录用日期:2022-11-11 发布日期:2022-11-16
  • 通讯作者: 沈丽娟,詹瑛瑛,江莉龙 E-mail:syhgslj@fzu.edu.cn;zhanyingying@fzu.edu.cn;jll@fzu.edu.cn

Deactivation Mechanism of COS Hydrolysis over Potassium Modified Alumina

Ganchang Lei1,2, Yong Zheng1,2, Yanning Cao1,2, Lijuan Shen1,3,*(), Shiping Wang1,2, Shijing Liang1,2, Yingying Zhan1,2,*(), Lilong Jiang1,2,*()   

  1. 1 National Engineering Research Center of Chemical Fertilizer Catalyst, School of Chemical Engineering, Fuzhou University, Fuzhou 350002, China
    2 China Fujian Innovation Laboratory of Chemical Engineering, Qingyuan Innovation Laboratory, Quanzhou 302801, Fujian Province, China
    3 College of Environmental Science and Engineering, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350007, China
  • Received:2022-10-27 Accepted:2022-11-11 Published:2022-11-16
  • Contact: Lijuan Shen, Yingying Zhan, Lilong Jiang E-mail:syhgslj@fzu.edu.cn;zhanyingying@fzu.edu.cn;jll@fzu.edu.cn


天然气、油田伴生气、高炉煤气等化工生产过程中伴生COS气体,不仅会腐蚀管道和毒害催化剂,还会严重污染环境并危害人类健康。COS催化水解反应可在温和条件下高效的将COS脱除,是最具应用前景的COS脱除技术之一。碱金属元素因其具有独特的电子供体性质、表面碱性和静电吸附等特性,常被用作助催化剂以提高Al2O3的COS催化水解性能。近年来,以钾为助剂改性的Al2O3催化剂(K2CO3/Al2O3)在COS催化水解反应中得到广泛的应用,但由于负载在Al2O3上的K物种的组成复杂,目前研究者对K2CO3/Al2O3催化剂上COS水解机理的理解仍存在一定的困惑和争议。本论文通过湿法浸渍法合成出一系列钾盐和钠盐改性的Al2O3催化剂,并利用各类先进的表征技术对这些催化剂进行分析。活性测试表明,以K2CO3、K2C2O4、NaHCO3、Na2CO3和NaC2O4改性Al2O3催化剂均有助于COS的水解。其中K2CO3/Al2O3拥有最佳的COS水解性能,连续运行20 h后其COS转化率仍高于~93%,远远优于未改性的Al2O3 (~58%)。我们利用原位红外光谱和X射线光电子能谱探明了反应过程中催化剂的化学结构特征,阐明了H2O分子在K2CO3/Al2O3上的水解作用机制。原位红外表明COS在K2CO3/Al2O3上的水解过程中形成了硫代碳酸氢盐中间产物。X射线光电子能谱表征证明催化剂的失活主要是因为催化剂表面积累了硫酸盐和单质硫。此外,我们还研究了水蒸气含量对COS水解性能的影响,研究发现,由于H2O和COS分子在催化剂表面存在竞争吸附,过量的H2O会引起催化活性的下降。上述研究表明,K2CO3/Al2O3催化剂上COS水解性能的提高主要是形成了HO-Al-O-K界面活性位。更为重要的是,所制备的催化剂都是在模拟工业工况条件下进行的,这为后续的工业应用提供了宝贵理论指导。本工作为理解助剂钾在Al2O3催化剂上COS水解活性的增强提供了新的见解,这为未来设计稳定高效的COS水解催化剂打开了新的发展方向。

关键词: 羰基硫, 催化水解, HO-Al-O-K界面活性位点, 失活机理, 工业工况条件


Carbonyl sulfide (COS) is commonly found in conventional fossil fuels, such as nature gas, oil-associated gas, and blast-furnace gas, and its untreated emission not only corrodes pipelines and poisons catalysts but will also inevitably pollute the environment and endanger human health. Catalytic hydrolysis is recognized as the most promising strategy to eliminate COS because it can be performed under mild reaction conditions with a high removal efficiency. Notably, alkali metals promote catalytic COS hydrolysis over Al2O3 owing to their electron donor properties, basicity, and electrostatic adsorption. However, despite the significant attraction of using potassium-promoted Al2O3 (K2CO3/Al2O3) as conventional catalysts for COS hydrolysis, the mechanism of COS hydrolysis over K2CO3/Al2O3 remains unclear and is controversial owing to the complex composition of the K species. In this study, commercial Al2O3 modified with potassium and sodium salts were synthesized using the wet impregnation method and characterized by various techniques. Based on the results of the activity measurements, the K2CO3-, K2C2O4-, NaHCO3-, Na2CO3-, and NaC2O4-modified catalysts had a positive effect on COS hydrolysis. Among them, the K2CO3/Al2O3 catalyst exhibited the highest COS conversion. Notably, the K2CO3/Al2O3 catalyst exhibited an excellent catalytic performance (~93%, 20 h), which is significantly better than that of pristine Al2O3 (~58%). Furthermore, this study provides strong evidence for the role of H2O during catalytic hydrolysis over K2CO3/Al2O3 using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray photoelectron spectroscopy (XPS). The in situ DRIFTS analysis revealed that hydrogen thiocarbonate formed as an intermediate during COS hydrolysis over K2CO3/Al2O3. Meanwhile, the XPS findings suggested that sulfates and elemental sulfur accumulated on the catalyst surface, which may have contributed to catalyst poisoning. Additionally, the effect of water vapor content in the reaction pathway of COS hydrolysis over K2CO3/Al2O3 was investigated. The presence of excess water resulted in a reduction in catalytic activity owing to competitive adsorption between H2O and COS molecules on the catalyst surface. The enhancement in the catalytic activity over K2CO3/Al2O3 may be attributed to the formation of HO-Al-O-K interfacial sites. More importantly, all the catalysts were used under industrially relevant conditions, which provides valuable theoretical guidance for practical applications in the future. Thus, this detailed mechanistic study reveals new insights into the roles of the interfacial K co-catalyst, which provides a new opportunity for the rational design of stable and efficient catalysts for COS hydrolysis.

Key words: Carbonyl sulfide, Catalytic hydrolysis, HO-Al-O-K interface site, Deactivation mechanism, Industrial-relevant condition