抄録
In order to obtain basic information useful for developing modified activated carbons suitable to adsorb carbon monoxide and formaldehyde, ab initio molecular orbital (MO) calculations were carried out. Adsorptive interactions between the adsorbates and modified activated carbons impregnated with metal chlorides were studied. Fragments of metal chlorides MCln (M = metal atom, n = 1, 2, or 3) were adopted as molecular models of adsorption sites. Geometry optimization was done by Hartree-Fock (HF) level calculations to determine structures of adsorbates, adsorption sites, and adsorption geometries; interaction energies were evaluated by MP2 level calculations. As for CO adsorption, interaction energies were large for CuCl and PtCl2, and small for chlorides of typical metal atoms. Back donation through π-bonds for CuCl and PtCl2 should cause such difference. On the other hand, judging from the present calculated results, MgCl2 was suitable for HCHO adsorption. Relatively small interaction energies for HCHO adsorption on CuCl and PtCl2 should be partially because back-donation does not occur. In order to discuss the validity of the calculated results, several modified activated carbons impregnated with metal chlorides were prepared and adsoption experiments were carried out. Activated carbons impregnated with CuCl and PtCl2 were effective in CO adsorption, one with MgCl2 was effective in HCHO adsorption. The experimental results showed that the deduction based on calculated results is valid. The MO calculations seem to be applicable for the screening to select the candidate that will be effective in adsorption for a certain adsorbate.
