商用SCR催化剂对单质汞（Hg0）的氧化作用研究

为开发对烟气NO_x和汞等多种污染物具有良好联合脱除效用的一体化新型催化剂，研究了目前商用SCR脱硝催化剂对单质汞（Hg⁰）的氧化作用及其影响因素，探求Hg⁰氧化反应机理。实验结果表明：SCR催化剂对烟气中的Hg⁰具有一定的氧化作用，但在催化剂最佳反应温度250~300 ℃时，其对Hg⁰的最大氧化效率仍低于50%。在低浓度NO和5%O₂同时存在的情况下，催化剂对Hg⁰有相对较高的氧化效率；SO₂存在时，Hg⁰的氧化明显被抑制，SO₂对催化剂的毒性基本不可逆转；NH₃与Hg⁰在吸附过程中存在竞争关系，因而NH₃的存在降低了催化剂对Hg⁰的氧化效率；H₂O对Hg⁰的氧化有十分明显的负面影响。

Study on the Oxidation Effects of Commercial SCR Catalyst on Elemental Mercury (Hg0)

In order to develop a novel integrated catalyst with better joint removal effects on various pollutants such as NO_x and mercury in the flue gas, the oxidation effects of commercial SCR denitration catalyst on elemental mercury (Hg⁰) and its influencing factors were studied in this paper. The oxidation reaction mechanism of Hg⁰ was also explored. The experimental results show that the SCR catalyst has some certain oxidation effects on Hg⁰ in flue gas. However, its maximum oxidation efficiency on Hg⁰ is still below 50% even at the optimum reaction temperature of 250~300 ℃. In the presence of low concentration of NO and 5% O₂, the catalyst has a relatively high oxidation efficiency for Hg⁰. While in the presence of SO₂, the oxidation of Hg⁰ was apparently inhibited, and the toxicity of SO₂ to the catalyst was basically irreversible. Moreover, there exists a competitive relationship between NH₃ and Hg⁰ in the adsorption process. So the presence of NH₃ reduces the oxidation efficiency of Hg⁰ by the catalyst. It also appears that the presence of H₂O has significant negative impact on the oxidation of Hg⁰.