Study On Adsorption Of No_x From Industrial Waste Gas By Na-ZSM-5Zeolites With High Silica

Adsorption process for NOx removal was proposed according to the feature of low oxidation degree, high content of vapor and oxygen of NOx, this process was simple and can recover NOx. Higher adsorption capacity will be obtained only if NO in the NOx waste gas is partially oxidized into NO2by O2because NO is difficult to adsorb, so it is the key point to find out one type of material with high hydrophobicity and adsorption capacity, which can catalyze NO oxidation into NO2. The adsorption of NOx onto the different adsorbents in a fixed bed reactor have been investigated in this study. Na-ZSM-5zeolite was both adsorbent and catalyst, and some major results were made as following:The tests’ results of the adsorbent’s adsorption property showed that AC, H-ZSM-5and Na-ZSM-5zeolites could adsorbe NOx, but water-resistant ability of AC was comparative weak. The adsorption capacity of Na-ZSM-5zeolites was higher than that of H-ZSM-5, so Na-ZSM-5zeolite of high silica was choosed as the adsorbent to remove NOx from the industrial plants.The effects of the reaction conditions on adsorbent’s adsorption property showed that breakthrough adsorption capacity of NO was merely 0.0034×10-3mol·g-1under free oxygen condition; however, breakthrough adsorption capacity of NOx growed to0.34×10-3mol·g-1when NO in the NOx waste gas was partially oxidized into NO2by O2over Na-ZSM-5zeolite. The adsorption of NOx was promoted by water vapor. Na-ZSM-5zeolite can easily be regenerated by thermal desorption of NOx, which was great utilization of industrial prospect. Adsorption capacity of NOx increases gradually with the increase of NOx oxidation degree, space time, NO inlet concentration and relative humidity, it decreases gradually with the increase of SiO2/Al2O3ratio and operation temperature. The breakthrough time of NO2increased gradually with the decrease of NOx oxidation degree, NO inlet concentration, SiO2/Al2O3ratio and space velocity, It first decreased and then increased with the increase of adsorption temperature from0℃to80℃.The adsorption mechanism was obtained by means of In-situ DRIFTS. A possible mechanism was proposed for NOx adsorption which can explained the course of NOx adsorption over Na-ZSM-5zeolite well:...