DESIGN OF ETHYLENE ADSORBENT BASED ON ANALYSIS OF ADSORPTION GEOMETRY USING MOLECULAR ORBITAL CALCULATION

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The surface of silica gel or alumina impregnated with metal cation was modeled and the structure was optimized by ab intio molecular obital (MO) calculation. The interaction energy △E between the model surface and adsorbate (ethylene or ethane) was determined by △E=E1+E2-E3, where E3 is the total energy for the adsorption structure. The isolated energies of adsorbate and adsorption site are E1 and E2. Metal cations are selected to give the maximum values of the interaction energy. AgNOィイD23ィエD2-silica gel, CuCl-silica gel, AgNOィイD23ィエD2-alumina, and CuCl-alumina were prepared by the impregnation method and the chemical vapor deposition (CVD) method. The adsorption selectivity of ethylene was experimentally studied. The adsorption geometry and energy were estimated by the MO calculations. The following conclusions were obtained.1) The MO calculations show that AgNOィイD23ィエD2 and CuCl are useful as impregnants to separate ethylene from ethane.2) AgNOィイD23ィエD2-silica gel and CuCl-alumina can be prepared by CVD method.3) X-ray photoelectron spectroscopy (XPS) measurement and Fourier transform infrared (FT-IR) measurement suggest that the adsorption sites of the adsorbents prepared are AgィイD1+ィエD1, AgNOィイD23ィエD2, CuィイD1+ィエD1,and CuCl.4) The MO calculation and adsorption experiments show that the adsorbents prepared show high ethylene selectivity.