High-capacity NO₂ denuder systems operated at various temperatures (298-473 K)

In this study, we investigated several coatings for high-temperature, high-capacity, and high-efficiency denuder-based NO₂ removal, with the scope to face the harsh conditions and requirements of automotive exhaust gas sampling. As first coating, we propose a potassium iodide (KI)/polyethylene glycol coating with a high removal efficiency (ε>98 %) for about 2 h and 50 ppm NO₂ at room temperature (298 K). At elevated temperatures (423 K), the initial capacity (100 ppmh) is decreased to 15 ppmh. Furthermore, this is the first proposal of the ionic liquid methylbutyl- imidazolium iodide ([BMIm⁺][I^-]) as denuder coating material. At room temperature, this ionic liquid exhibits far greater capacity (300 ppmh) and NO₂ removal efficiency (ε>99.9 %) than KI. Nevertheless, KI exhibits a slightly (~10 %) higher capacity at elevated temperatures than [BMIm⁺][I^-]. Both coatings presented are suitable for applications requiring selective denuding of NO₂ at temperatures up to 423 K.