Transformation of functional groups in the reduction of NO with NH3 over nitrogen-enriched activated carbons
Transformation of functional groups in the reduction of NO with NH3 over nitrogen-enriched activated carbons
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DOI：
10.1016/j.fuel.2018.01.092
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发表时间：
2018-07-01
期刊：
影响因子：
7.4
通讯作者：
Zhu, Tingyu
中科院分区：
文献类型：
--
作者：
Lin, Yuting;Li, Yuran;Zhu, Tingyu
近年来，活性炭技术已应用于各种工业烟气净化，具有较高的脱硫效率，但脱硝效率相对较低。为了增强活性炭的脱氮性能，进一步明确哪个理化因素对活性炭还原NO起主导作用，本研究采用四种富氮添加剂对活性炭进行改性，提高了活性炭的脱氮效率。孔隙率分析和拉曼光谱结果表明，改性降低了活性炭的比表面积和总孔体积，但促进了石墨微晶结构的无序化，为NO和NH3提供了吸附和反应活性中心。用x射线光电子能谱法对反应前后的含氧和含氮官能团进行了检测。结果表明，酚羟基氧转化为醌的羰基氧，吡啶、吡咯和季氮官能团转化为吡啶n -氧化物和胺。采用瞬态响应实验研究了稳态条件下突然切断NO或NH3的进气对脱硝反应中NO和NH3的吸附状态。结果表明，NH3在110℃时还原NO遵循Langmuir-Hinshelwood （L-H）机制，在150℃时还原NO遵循eley - rideal （E-R）机制和L-H机制。吡啶、吡咯和季胺基团可以气态吸附NO，酚羟基作为NH3的吸附位点生成醌和N-2，完成SCR反应。
In recent years, activated carbon technology has been applied in various industrial flue gas purifications, with a high desulfurization efficiency but a relatively low denitrification efficiency. To strengthen the denitrification performance and further clarify which physicochemical property factor dominates the reduction of NO over activated carbon, this study used four kinds of nitrogen-enriched additives to modify the activated carbon, and the denitrification efficiency increased. The results from porosity analysis and Raman spectra showed that modification reduced the specific surface area and total pore volume of the activated carbon but promoted the disorder of graphite microcrystalline structure providing the adsorption and reaction active center for NO and NH3. The oxygen-containing and nitrogen-containing functional groups were detected by X-ray photoelectron spectrometry before and after the reaction. The results revealed that the phenolic hydroxyl oxygen was transformed to carbonyl oxygen of quinone, and pyridine, pyrrole and quaternary nitrogen functional groups were converted to pyridine N-oxides and amines. The transient response experiment was employed to investigate the adsorption state of NO and NH3 in denitrification reaction by abruptly cutting off the intake of NO or NH3 under steady-state reaction. The results revealed that the reduction of NO with NH3 at 110 degrees C follows the Langmuir-Hinshelwood (L-H) mechanism, while at 150 degrees C with Elay-Rideal (E-R) mechanism and L-H mechanism. The pyridine, pyrrole and quaternary amine groups can adsorb NO in the gaseous state, and the phenolic hydroxyl group acts as the adsorption site of NH3 to produce quinones and N-2 and complete the SCR reaction.