Nitrogen dioxide adsorption

Carbon Dioxide Adsorption on Dried Polymer. Other unexpected interactions of these hydrolytic polymers have been noted previously during the measurement of infrared spectra of dried Pu(IV) polymers (like those used for diffraction studies). Vibrational bands first attributed to nitrate ion were observed in samples exposed to room air however, these bands were not present in samples prepared under nitrogen atmospheres (see Fig. 4) (6). Chemical analyses established enough carbon in the exposed samples to confirm the assignment of the extraneous bands to the carbonate functional group... 

Nitrogen dioxide, N02, is a fairly small molecule with an unpaired electron and may be expected to be a selective molecule for electron-deficient or Lewis acid sites. Nevertheless, only very little spectroscopic information on the nature of surface species formed on adsorption of N02 is available. Naccache and Ben Taarit (242) have shown by infrared spectroscopy and ESR that N02 forms Cr+N02+ and Ni+N02+ complexes on chromium and nickel zeolites. Thus, N02 behaves as an electron donor and reducing agent in these zeolites. Boehm (243) has studied the adsorption of N02 on anatase and on tj-A1203, which were pretreated at very low temperatures of only 100°-150°C. At 1380 cm-1, a band which is to be attributed to a free nitrate ion, was observed. Boehm (243) has explained the formation of the nitrate ion by the disproportionation by basic OH ions ... 

Figure 1 shows CO2 adsorption isotherms and Table 1 contains the micropore volume calculated from both nitrogen and carbon dioxide adsorption isotherms. 

Specific surface areas of various carbonized materials were measured by nitrogen gas adsorption with BET methods using an automated surface area analyzer (micro-track type 4200, Nikkiso, Japan). For mesopores whose diameter were less than SO nm, the surface areas and pore volumes were measured by carbon dioxide adsorption. The carbon dioxide adsorption at 298 K was measured with Bellsorp 28 (BEL Japan). The pore volume was determined using Dubinin-Radushkevich equation [4], and the surface area was determined by Medek s method [S]. 

Surface areas determined by nitrogen gas adsorption (Sn2)> nd those determined by carbon dioxide (Sco2) for the various carbonized materials are summarized in Table 2. The carbonated materials showed much smaller Sn2 than the activated carbon Granular Shirasagi. The Sco2> on the other hand, of the carbonated materials were almost the same order of magnitude to that of the activated carbon. These results show that the carbonized materials have mesopores whose diameter is less than SO nm. 

The following equilibrium data have been obtained for the adsorption of nitrogen dioxide, N02> on silica gel at 25°C and 1 atm ... 

Surface properties of the samples were examined fi om nitrogen and carbon dioxide adsorption measurements. 

Chemical absorption in scrubbers, which employ any of water, nitric acid, alkaline solutions, or solutions of urea in water can reduce tail gas NOx concentrations to below 200 ppm [55]. Physical adsorption on molecular sieves is also a feasible control method. Activated carbon cannot be used because of oxidation hazards. Chemical and physical adsorption were improved if both nitric oxide and nitrogen dioxide were present in the tail gas rather than just nitric oxide, perhaps from the formation of dinitrogen trioxide (N2O3). An advantage of any absorption or adsorption system is that the NOx collected is recovered in some form. 

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