The adsorption of C4 unsaturated hydrocarbons on highly dehydrated silica. An IR-spectroscopic and thermodynamic study

The adsorptive interaction of 1-butyne and 1-butene with a highly dehydrated pyrogenic silica system has been studied to understand the thermodynamic behavior of the adsorption process by the application of the Langmuir model and of the Van’t Hoff equation. In situFTIRspectroscopy allowed the characterization of the adsorption phenomenon in terms of involved surface sites, gas-volumetric determinations yielded quantitative information relative to the adsorption process, and microcalorimetric results allowed the comparison between calculated and experimental data. Keq and DadsG° were obtained from Langmuir’s model application; DadsH data were obtained from the Van’t Hoff equation and by the isosteric heats method and were compared with experimental values. The virtual constancy of DadsH with equilibrium pressure and surface coverage (Langmuir model) allowed us to obtain the DadsH° values and, consequently, the DadsS° values for the systems of interest.