Molecular Modeling Study Of Complex Adsorption Of Carbon Monoxide On Activated Carbon Loaded With Cuprous Salt

With the development of C1-Chemistry, carbon monoxide is increasingly used to synthesize a lot of organic products. In another aspect, some exhaust gases from industries contain carbon monoxide, which is harmful to human beings. So the recovery and reuse of this gas has become a very important task. Compared with some common ways, for example, low-temperature separation process and chemical absorption process, adsorptive separation method 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 and so on. Many experimental studies on the process of this method have been made, while little study on the mechanism of the process was reported. This paper aims at the mechanism of adsorption of carbon monoxide on activated carbon loaded with cuprous chloride.The density functional theory and the cluster approach have been applied in this study. Calculations are performed at the B3LYP approach using LanL2DZ basis set for Cu and Cl atoms, whereas 6-31G(d) basis set is used for C, H, O, N atoms. Ci2H12. CnH9. CigH10. C2oH12. C23H13. C26H14. CaoH16 clusters are used to model activated carbon with different active sites.The results show that adsorption mechanism of carbon monoxide on activated carbon loaded with cuprous chloride is:(1) Cuprous chloride prefers to disperse at the top site and bridge site of activated carbon surface and forms cuprous salt monolayer. The interaction energy is 76.84-80.79 KJ/mol.(2) Adsorption of carbon monoxide on activated carbon loaded with cuprous chloride is due to the interaction of p-complexation between cuprous chloride and carbon monoxide. One cuprous chloride can adsorb one ortwo carbon monoxide molecule with adsorption energy that decreases with increase of adsorption quantity of carbon monoxide and the initial adsorption energy is 60.72-61.15 KJ/mol.(3) Physical adsorption energy of carbon monoxide at the hole site of activated carbon surface is 9.15 KJ/mol, and adsorption energy of nitrogen at the hole site of activated carbon surface is 11.33 KJ/mol - adsorption energies of the two gases on activated carbon are so close that they cannot be separated from each other by activated carbon.(4) Cuprous chloride loaded on activated carbon reacts with carbon monoxide, while it does not interact with nitrogen. On the contrary, monolayer dispersion of cuprous chloride on activated carbon surface prevents from the interaction between nitrogen and activated carbon. So carbon monoxide can be separated from nitrogen.By experimental measurement, isosteric heat of adsorption of carbon monoxide on activated carbon loaded with cuprous chloride is 52.6KJ/mol at the limit of zero coverage and declines when adsorption amount of carbon monoxide adds. FTIR spectroscopy probes that the species of carbon monoxide adsorption on activated carbon loaded with cuprous chloride is Cu+-CO at equilibrium pressure below 1 atm, and Cu (CO)2 appears when equilibrium pressure is above 1 atm. Such results are both in agreement with molecular modeling results. Molecular modeling is validated as a reliable approach to explain the adsorption of carbon monoxide on activated carbon loaded with cuprous salt, which supplies a theoretical basis for the further studies on activated carbon loaded with cuprous salt.