Abstract:The treatment of NO x from automotive gas exhaust has been widely studied, however the presence of low concentrations of NO x in confined areas is still under investigation. As an example, the concentration of NO 2 can approximate 0.15 ppmv inside vehicles when people are driving on highways. This interior pollution becomes an environmental problem and a health problem. In the present work, the abatement of NO 2 immission is studied at room temperature. Three activated carbons (ACs) prepared by physical (CO 2 or H 2 O) or chemical activation (H 3 PO 4 ) are tested as adsorbents. The novelty of this work consists in studying the adsorption of NO 2 at low concentrations that approach real life immission concentrations and is experimentally realizable. The ACs present different structural and textural properties as well as functional surface groups, which induce different affinities with NO 2 . The AC prepared using water vapor activation presents the best adsorption capacity, which may originate from a more basic surface. The presence of a mesoporosity may also influence the diffusion of NO 2 inside the carbon matrix. The high reduction activity of the AC prepared from H 3 PO 4 activation is explained by the important concentration of acidic groups on its surface.

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Cabin air filters consisting of activated carbon infiltrated with nanoscopic metal oxide particles as catalysts have been investigated for the reduction of nitrogen oxides within motor-car cabins. In that concept, nitrogen dioxide is adsorbed on the activated carbon during operation conditions of the car and then reduced by the catalysts within the pores. The conversion has to take place at ambient temperature during the relatively long standstill periods of motor-cars. In this article we are going to discuss the manufacturing of the adsorbents by "liquid phase infiltration" and their characterization by techniques, such as nitrogen sorption analysis, X-ray diffraction, thermogravimetry, energy dispersive X-ray spectroscopy, and electron microscopy. The new adsorbents were evaluated in repeated breakthrough tests using NO₂ (4 ppm(V) as feed concentration) in humid air as the adsorptive. In the intermittent rest periods of varying duration the volume flow through the fixed bed of adsorbent was stopped. The measured breakthrough curves indicate a catalytic conversion of the nitrogen dioxide in the filter beds

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