非法拉第过程促进纳米钯低温催化氧化低浓度甲烷的基础研究

Catalytic oxidation of methane (CH4) is the primary method for controlling the low-concentration CH4 emission from the ventilation-air-methane of coal mines and the exhaust of engines. So far, promoting low-temperature catalytic oxidation of low-concentration methane is still one of the challenges in catalytic combustion. Here we put forward a new idea for low-temperature catalytic oxidation of low-concentration CH4, that is using the Non-Faradaic process induced by electric field to enhance the catalytic oxidation of CH4 over nanosized palladium at low temperature. In this proposal , the scientific issues in Non-Faradaic process promoting catalytic oxidation of CH4 over nanosized palladium catalysts will be stated by carrying out the following tasks: (1) to explore the mechanisms of Non-Faradaic process caused by applying electric field to Pd-based catalysts, and (2) to explore the mechanisms of Non-Faradaic process affecting the low-temperature catalytic oxidation of CH4 over Pd-based catalysts, and （3）to study the mechanisms of catalyst structure affecting the low-temperature catalytic oxidation of CH4 over Pd-based catalysts with Non-Faradaic process, and to establish the design principles of Pd-based catalysts used for low-temperature catalytic oxidation of low-concentration CH4 enhanced by Non-Faradaic process. The scientific merit of the research works proposed in this proposal is to provide fundamental basis for developing high-performance catalysts for low-temperature catalytic oxidation of low-concentration methane.

甲烷（CH4）催化氧化是控制煤矿通风瓦斯和发动机尾气中低浓度CH4排放的主要方法，提高CH4氧化催化剂的低温活性是催化燃烧领域需要攻克的难题。本项目采用电场诱发的非法拉第过程增强纳米钯（Pd）基催化剂低温催化氧化CH4的活性，提出了解决低浓度CH4低温氧化这一难题的新思路，并围绕相关科学问题开展研究，主要研究内容包括：（1）探究施加电场条件下Pd基催化剂中非法拉第过程的产生机制；（2）探究非法拉第过程影响Pd基催化剂低温催化氧化CH4的机制；（3）探索非法拉第过程作用下Pd基催化剂结构对CH4低温催化氧化的影响规律，建立非法拉第过程驱动条件下低浓度CH4低温氧化催化剂的设计原则。本项目研究将为开发高效的低浓度CH4低温催化氧化技术提供理论基础。

本项目将电场引发非法拉第过程与传统催化氧化技术相结合，利用施加在催化剂表面的电场产生电流，提高催化剂的低温甲烷转化率。搭建了电场协同低温催化氧化甲烷的催化剂性能评价系统，合成了不同载体组分和配比的纳米钯（Pd）基催化剂，对施加电场前后催化剂的甲烷转化效率和抗水性能进行了综合评价。采用X射线衍射（XRD），比表面积分析（BET），H2-程序升温还原（H2-TPR），透射电子显微镜（TEM），X射线光电子能谱（XPS）等表征技术明确了电场中催化剂低温性能优异的关键因素；采用原位漫反射红外分析（in-situ DRIFT），对比研究了施加电场前后催化剂表面产生的中间产物及反应路径的变化，揭示了电场引发催化剂表面非法拉第过程协同低温催化氧化低浓度CH4的机制，以此为准则优选出性能与Pd 基催化剂相媲美的非贵金属（Mn、Co）催化剂。该技术应用于低浓度（0.2%）CH4的催化氧化过程有效降低其起燃温度至300摄氏度以下；相同工况条件下，可减少约50%的贵金属Pd用量，为低成本解决天然气发动机低温冷启动阶段的甲烷逃逸问题，实现温室气体排放的有效控制提供了新方案。此外，该技术也为解决其他挥发性有机物（VOCs）的低温催化氧化问题提供了新的研究思路。