Study On Some Problems About The Improving Of Carbon Monoxide Adsorbents

With the development of C1-Chemistry, carbon monoxide is increasingly used to synthesize a lot of organic products. Some exhaust gases from industries contain carbon monoxide, which is harmful to human beings. So the recovery and the reuse of such waste gases have become a very important task. Compared with some classical ways, for example, the low-temperature separation process, pressure swing adsorption process is a better one for its easier operation and lower energy demand. Nowadays, the study on this method is concentrating on cuprous salt as an active component loaded on a carrier, such as zeolite, activated carbon. The silver ion is similar to cuprous ion, while little experimental study on silver salt loaded on a carrier is reported. This paper studies adsorption of carbon monoxide on activated carbon loaded with silver chloride, comparing with cuprous chloride. Then we study and screen the improving of CO adsorbents. The useful adsorbent for pressure swing adsorption is found. The density functional theory and the cluster model approach have been applied in this paper. Calculations are performed with the B3LYP approach using LanL2DZ basis set for Cl and Ag atoms, whereas 6-31G(d) basis set is used for C, H, O atoms. C₁₂H₁₂, C₁₃H₉, C₁₆H₁₀ clusters are used to model activated carbon with different active sites. Silver chloride prefers to disperse at the top site and bridge site of activated carbon surface and the interaction energy is between 46.26 and 47.64 kJ/mol. Different clusters are used to model the monolayer dispersion of AgCl on activated carbon. The mechanism of reaction of carbon monoxide with silver chloride is studied. Adsorption of carbon monoxide on activated carbon loaded with silver chloride is due to the interaction of p-complexation between silver chloride and carbon monoxide, with adsorption energy about 45kJ/mol. Both simulated and experimental results show that the CO adsorption capacity of silver chloride loaded on activated carbon is smaller than that of cuprous chloride. We study the carbon monoxide adsorbents, cuprous chloride loaded on AC, AC treated by H2O2 (AC(H2O2)) and NH4Y. The monolayer dispersion thresholds of cuprous chloride on carriers measured by XRD method are 0.467gCuCl/gAC, 0.784gCuCl/gAC(H2O2) and 0.763gCuCl/gNH4Y. Zero length column technique (ZLC) method is a useful technique for equilibrium measurement. The ZLC measurement consisits with volumetric isotherm and can be used for screening adsorbents quickly. With ZLC method, we find the adsorption capacities of 0.4gCuCl/gAC, 0.7gCuCl/gAC(H2O2) and 0.8gCuCl/gNH4Y are larger than the others in their respective systems. 0.8gCuCl/gNH4Y has the largest adsorption capacity, but the isotherm of it doesn't benifit for adsorbent reuse in pressure swing adsorption. The adsorbent, 0.8gCuCl/gNH4Y and 0.7gCuCl/gAC(H2O2) mixed in the proportion of 1:4, is a better one in pressure swing adsorption process for carbon monoxide.