CAREER: Heterogeneous Catalytic Oxidation and Adsorption of Mercury Vapor: Integrated Research and Education in Air Pollution Control

汞是一种有毒的持久性污染物，可在食物链中生物积累。人类接触汞主要是通过食用受污染的鱼类。环境中的汞转化为毒性更大的甲基汞；甲基汞的摄入可能引起神经毒性作用。儿童，特别是发育中的胎儿特别容易受到甲基汞的影响。美国环保署提出的汞和空气有毒物质标准要求，从2016年起，燃煤和燃油发电厂使用最大限度的可用控制技术来减少汞和其他有害空气污染物的排放。在烟气中存在的元素汞、氧化汞和颗粒汞中，元素汞（Hg(0)）最难控制，因为其浓度低，通过均匀氧化与其他烟气组分的反应性低，在水中的溶解度低。这项CAREER研究计划将极大地促进对汞(0)蒸汽和过渡金属氯化物之间反应的非均相催化氧化和吸附的认识和基本机理的理解。本文将对过渡金属氯化物对Hg(0)氧化的环Deacon反应进行详细的机理研究。过渡金属氯化物被认为在Hg(0)氧化中比金属氧化物更有效，因为它们可以很容易地消除限制速率的竞争性HCl吸附步骤。Hg(0)与过渡金属氯化物的反应是一种催化反应，使得氯化物被消耗，形成易溶解和可吸附的HgCl2。金属降低了氧化反应的活化能垒。这将导致进一步发展金属氯基改性选择性催化还原材料，同时还原NOx和氧化Hg(0)，特定的Hg(0)催化剂和吸附剂。本研究将基于对物理和化学原理的基本理解，提高预测Hg(0)去除的能力。它最终将导致提出的汞排放控制条例所需的先进科学知识和加强汞控制备选办法。它还将导致各种基于多相催化、吸附和吸收的环境修复和分离技术。该教育计划将为化学和环境工程学院、学生以及环境催化、分离和空气质量/空气污染控制领域的专业人员提供共同利益。所有这些努力最终将提高人们对汞作为一种全球性污染物以及在烟气排放中控制汞的最佳管理做法的认识。

1151017 - LeeMercury is a toxic and persistent pollutant that bio-accumulates in the food chain. Human exposure to mercury occurs primarily by consumption of contaminated fish. Mercury in the environment is transformed into more toxic methylmercury; consumption of methylmercury may cause neurotoxic effects. Children and particularly developing fetuses are especially susceptible to methylmercury effects. A USEPA proposed rule, Mercury and Air Toxics Standards, requires coal- and oil-fired power plants to use maximum available control technology to reduce the emissions of mercury and other hazardous air pollutants as of 2016. Among elemental, oxidized, and particulate-bound mercury species present in flue gas, elemental mercury (Hg(0)) is most difficult to control because of its low concentrations, low reactivity with other flue gas components via homogenous oxidation, and low solubility in water. This CAREER research plan will significantly advance the knowledge and fundamental mechanistic understanding of heterogeneous catalytic oxidation and adsorption using the reactions between Hg(0) vapor and transition metal chlorides. A detailed mechanistic study will be conducted to investigate the cyclic Deacon reaction involving transition metal chlorides for Hg(0) oxidation. Transition metal chlorides are proposed to be more effective in Hg(0) oxidation than metal oxides since they can readily eliminate the rate-limiting competitive HCl adsorption step. The reaction of Hg(0) with transition metal chlorides is a catalytic reaction such that chloride is consumed to form readily soluble and adsorbable HgCl2. The metal lowers the activation energy barrier for the oxidation reaction. This will lead to the further development of metal chloride-based modified selective catalytic reduction materials for simultaneous NOx reduction and Hg(0) oxidation, Hg(0)-specific catalysts, and sorbents. This proposed research will enhance the capability to predict Hg(0) removal based on a fundamental understanding of physical and chemical principles. It will ultimately lead to advanced scientific knowledge and enhanced mercury control options needed for proposed mercury emission control regulations. It will also lead to various environmental remediation and separation technologies based on heterogeneous catalysis, adsorption, and absorption. The educational plan will provide co-benefits for chemical and environmental engineering faculty, students, and professionals in the areas of environmental catalysis, separation, and air quality/air pollution control. All of these efforts will ultimately increase awareness of mercury as a global pollutant and of best management practices for its control in flue gas emissions.