Low-Temperature Adsorption Of Nitrogen Oxides On Modified Activated Carbon And Carbon Aerogels

Nitrogen oxides （NO_x）, which is extremely harmful to our health andenvironment, is one of the main air pollutants. The reduction of NO_x is importantfor purifying our atmospheric environment. Two kinds of porous carbon materials arestudied on their performances and properties of adsorption of NO_x. One ismetal-impregnated activated carbon which has specific characteristics on the surface,and the other is carbon aerogels synthesized by drying at ambient pressure.Metal oxides are loaded on the activated carbon by impregnation and theirperformances of adsorption of NO_x are tested. Results show that: the Ce, Mn, Co,KOH-impregnated activated carbon presents better than activated carbon（AC0）, andthe adsorption of NO_x in3h may increase about10%. The NO_x saturationadsorption capacity of the activated carbon loaded with MnCoOx fixed oxides, withthe condition: Co/（Mn+Co）=0.16, calcining under400℃⁵00℃and2.78%by massof Mn and Co loaded, is as high as186.5mg/g at35℃. Also by heating it to200℃, itcan release the adsorbed NO_x completely.The adsorption of NO_x on MnCo/AC is also studied in a fixed adsorbent bed. Itis found that the presence of O₂increases the adsorption of NO_x on MnCo/AC, andthe best concentration of O₂is3%. The adsorption performances change accordinglywhen the flow rate of all inlet gases, concentration of NO_x, concentration of O₂, themass amout of sorbents and adsorption temperature were changed. The water vaporaffects the NO_x adsorption over MnCo/AC when O₂is present, but it has almost noeffect without O₂.Synthesis condition as reaction time in every phase and mass ratios of materials,and pyrolysis condition as atmosphere and temperature greatly affect thecharacteristics of carbon aerogels by drying at ambient pressure, the carbon aerogelsdensity varies from0.126g/cm³to0.778g/cm³, volume shrinkage varies from6.7%to87.8%, the carbon product yield from23.9%to49.9%, and the surface area from201m²/g to1994m²/g. The adsorption of NO_x over carbon aerogels indicates that theNO_x adsorption capability of carbon aerogels is much higher than activated carbon. Its NO_x adsorption capacities of saturation is267mg NO_x/g sorbent at35℃andthe adsorbed NO_x can be relaeased completely by heating at500℃. Moreover,supporting MnCoOx onto carbon aerogels could increase the initial adsorption rate.