Surface properties of silica gel and silica gel-supported ion-exchanged copper in transformations of various molecular probes: an infrared study

Abstract

An IR study on some surface properties of silica gel and an ion-exchanged silica gel-supported Cu catalyst (Cu/S-X) using D 2, D 2O and 1,1-dimethylcyclopropane (DMCP) as molecular probes is reported. The interactions of DMCP “alone” or a mixture of DMCP and D 2 were studied over predeuterated surfaces. As far as the preparation of deuterated surfaces is concerned, it was found that the broad OH band on silica gel could be gradually transformed to a relatively sharp OD band by increasing the temperature of D 2 treatment. Using D 2O resulted in complete OHOD exchange even at room temperature. When copper was deposited on the support, the OHOD exchange with D 2 became faster and went to completion at 673 K. The shape of the OD bands resulting from this surface reaction and that of D 2O was nearly identical. Experiments carried out with DMCP or DMCP + D 2 over predeuterated catalysts provided direct information about the mode of adsorption of the cyclopropane.