The Electronic and ESR Spectra of Triphenylmethane Adsorbed on Solid Acid Catalysts

The electronic spectra of adsorbed triphenylmethane have been observed through a study of disk samples made by the compression method from ordinary powder catalysts. Three kinds of adsorbed species of triphenylmethane were obtained for silica-alumina. The band at 265 mμ was due to a physically adsorbed species (Ph3CH). A new band at 340 mμ was assigned to the triphenylmethyl radical (Ph3C·), formed in the absence of air, with a sharp spectrum (g=2.004) observed in the electron spin resonance. The species of the bands at 408 and 435mμ was identified as triphenylcarbonium ion (Ph3C+), the amount of which increased with the light and temperature exposure period. Types of acid present on silica-alumina, alumina, silica, and other catalysts were discussed.