Methanol-Promoted Oxidation of Nitrogen Oxide (NO) by Encapsulated Ionic Liquids

The removal of nitrogen oxides (NO) has been extensively studied due to their harmful effects to health and environment. In this work, encapsulated ionic liquids (ENILs) are used as catalysts for the NO oxidation at humid conditions and low temperatures. Hollow carbon capsules (C_Cap) were first synthesized to contain different amounts of 1-butyl-3-methylimidazolium nitrate IL ([bmim][NO₃]), responsible for the catalytic oxidation. Then, the materials were characterized using different techniques, by analyzing microstructure, porosity, elemental composition, and thermal stability. The catalytic performance of ENIL materials was tested for NO conversion at different conditions. Thus, NO concentration was fixed at 2000 ppm at dry and humid conditions. Then, the methanol promotion of the reaction was demonstrated, increasing the NO conversion values in all cases, and the alcohol/water ratio was optimized. The temperature effect was studied as well, using the optimal conditions based on the previous measurements. The results reflect that humid conditions do not have a negative effect in terms of NO conversion when using ENILs, opposite behavior as observed for C_Cap and traditional catalysts studied before. The low amount of IL inside the material (40% in mass) was found to be the optimum for the task, reaching conversions of almost 45% in near industrial conditions of temperature and O₂ and H₂O concentrations in the flue gas with a GHSV of 10,000 h^-1.