Dastgheib Seyed A, Salih Hafiz, Ilangovan Tina, Mock Justin
Illinois State Geological Survey, Prairie Research Institute, University of Illinois, 615 E. Peabody Drive, Champaign, Illinois 61820, United States.
ACS Omega. 2020 Aug 16;5(33):21172-21180. doi: 10.1021/acsomega.0c02891. eCollection 2020 Aug 25.
Nitric oxide can be removed from flue gas by catalytic oxidation of NO to NO, followed by dissolution of NO in water. The work presented here includes catalytic NO oxidation by activated carbons (ACs) at atmospheric and elevated pressures under dry and wet conditions at ambient temperature. The AC samples had different physicochemical characteristics including surface areas of ∼400-1600 m/g and micropore volumes of ∼0.2-0.6 cm/g while having different surface chemistries. Dry tests indicated that introducing nitrogen functionalities or coating with pyrolytic carbon could enhance the catalytic activity of AC for NO oxidation. Nitric oxide concentration profiles from the oxidation experiments under dry conditions showed maximum values after 5-15.5 h of testing and a steady-state condition after ∼12-30 h and that a major release of NO began after reaching the maximum values in the NO concentration. Adsorption profiles showed a high rate of NO adsorption during the early hours of these experiments, and this rate decreased almost exponentially to a near-zero value. A near-complete catalytic conversion was achieved for NO oxidation at 120 psig under dry conditions, substantially higher than the 62% value of the noncatalytic NO oxidation at 217 psig. The wet trickle-bed experiments revealed that an inert packing material with a high external surface was a more suitable option than the ACs for NO oxidation in a wet trickle-bed system, even for ACs that exhibited high catalytic reactivity under dry conditions. Noncatalytic NO oxidation in the trickle-bed system was enhanced by the higher gas-liquid contact surface of the packing material for NO dissolution in water. Complete wetting of the hydrophilic AC or the presence of water vapor in the gas in contact with the surface of the superhydrophobic AC could eliminate or drastically reduce the catalytic activity of the AC for NO oxidation.
一氧化氮可通过将NO催化氧化为NO₂，随后将NO₂溶解于水中的方式从烟道气中去除。本文介绍的工作包括在环境温度下，在常压和高压条件下，于干燥和潮湿环境中通过活性炭（AC）对NO进行催化氧化。AC样品具有不同的物理化学特性，包括表面积约为400 - 1600 m²/g，微孔体积约为0.2 - 0.6 cm³/g，同时具有不同的表面化学性质。干燥试验表明，引入氮官能团或用热解碳包覆可提高AC对NO氧化的催化活性。干燥条件下氧化实验的一氧化氮浓度曲线显示，测试5 - 15.5小时后出现最大值，约12 - 30小时后达到稳态，且在NO浓度达到最大值后开始大量释放NO。吸附曲线表明，在这些实验的最初几个小时内NO的吸附速率很高，且该速率几乎呈指数下降至接近零值。在干燥条件下，120 psig时NO氧化实现了近乎完全的催化转化，大大高于217 psig时非催化NO氧化的62%的值。湿滴流床实验表明，在湿滴流床系统中，具有高外表面的惰性填充材料比AC更适合用于NO氧化，即使对于在干燥条件下表现出高催化活性的AC也是如此。滴流床系统中的非催化NO氧化因填充材料较高的气液接触表面有利于NO溶解于水中而得到增强。亲水性AC的完全润湿或与超疏水性AC表面接触的气体中存在水蒸气，可消除或大幅降低AC对NO氧化的催化活性。
