同步辐射表征技术用于中温煤气干法脱汞机理的研究

Coal gasification is one of the most efficient clean coal technologies and will be widely used in the next twenty years. However, pollutants, such as mercury, hydrogen sulfide, hydrogen chloride, etc., must be removed from the coal-based gases before further utilization. In this project, synchrotron-based X-ray absorption spectrum (XAS) and high-resolution photoemission spectroscopy (XPS) will be used as the key characterization methods to reveal how H2S affects the capture mercury over Pd-based sorbents. On this base, Pd-based sorbent will be modified and designed to get the high-efficient adsorption catalytic system with anti-H2S poison or highly efficient capturing H2S at the medium-temperature range 200-300 C, which can maintain the high thermal efficiency of the systems. Understanding the mechanism of the removal mercury and the development of the technology for capturing mercury at the medium-temperature range are our main aims. Transition metal Me (Me=Fe, Mo, Cu or Zn, which has good H2S adsorption ability) is selected and added into Pd-based sorbent using the impregnation or precipitation methods to produce the bi-metal or the alloy sorbents. Combination with preliminary characterization and analysis results, the nature of the interaction between the metals, the metal with S and Hg can be determined by XAS (as an energy shift of the absorption edge) and XPS (as an energy shift of the electronic bands); the reaction network between H2S-Hg-Pd-Me can be established and the effect of H2S on the activity for removal Hg over Me-Pd-based sorbents can be deduced. The path for the removal Hg over Me-Pd-based sorbents also can be clarified. Based on this result, we plan to solve the divergence of views of the removal Hg from coal-based gas between different research groups. Our work will provide strong experimental and theoretical basis for the subsequent industrial development of this coal-based gas purification technology.

煤气化作为目前煤转化效率最高的洁净煤技术之一，将在未来的二十年被大力推广。但是煤气中的污染物（Hg、H2S、HCl等），在利用前必须脱除。课题以同步辐射X射线吸收谱( XAS)和超高分辨光电子能谱(XPS)为主要表征手段，重点揭示H2S等气氛对Pd基吸附剂脱汞的影响，有针对性的对Pd基吸附剂进行改性，设计和构建抗硫或同时脱硫的煤气中温脱汞吸附催化体系，明晰脱汞机理，发展煤气脱汞技术。工作结合课题组近期研究结果和文献资料，通过浸渍或共沉淀等方法将具有较好的吸附H2S能力的过渡金属Me（Me=Fe，Mo，Cu或Zn等）分散到Pd基吸附剂上形成双金属或合金吸附剂。通过对脱汞前后吸附剂的XAS和XPS表征分析，结合其它表征结果，建立H2S-Hg和Pd-Me的反应网络，阐明汞的脱除路径。通过本课题研究，希望解决煤气脱汞在理论研究上的一些分歧，为中温煤气净化技术的后续工业开发提供有力的理论依据。

气化是煤清洁转化的源头技术，热解是其中的必经步骤，该过程中释放的单质汞的量因气相产物处于还原性氛围而高于煤燃烧过程。课题以同步辐射X射线吸收谱和超高分辨光电子能谱为主要表征手段，重点揭示H2S等气氛对Pd基吸附剂脱汞的影响，再此基础上对Pd基吸附剂进行改性，设计和构建抗硫或同时脱硫的煤气中温脱汞吸附催化体系。工作通过浸渍或共沉淀等方法将具有较好的吸附H2S能力的过渡金属Me（Me=Fe，Mn，Cu，Zn和Ce等）分散到Pd基吸附剂上形成双金属吸附剂,第二金属的添加可以改善Pd/CAC吸附剂的脱汞活性，尤其是Fe，其次为Mn。考虑到Fe价格低廉，被认为是第二金属的最佳选择。第二金属对Pd基吸附剂脱汞作用的改善受吸附剂载体的影响。PdO与煤气中的H2反应生成Pd2O，Pd2O进一步被还原为Pd0；PdO与煤气中的CO反应生成Pd0，单质钯和单质汞反应生成钯汞齐。脱汞活性降低的原因主要为：煤气中的H2S与PdO反应生成PdS的毒化作用；吸附剂中的Fe2O3和H2S反应生成FeSx 和 Sad，Sad和新生成的Pd0反应生成PdS的毒化作用。通过对脱汞前后吸附剂的XAS和XPS表征分析，结合其它表征结果，阐明汞的脱除路径。本课题研究，为中温煤气净化技术的后续工业开发提供有力的理论依据。