Examination of the structure and energetic properties of carbosils surface prepared by dichloromethane pyrolysis

A full, complex characterization of the adsorbents under consideration is of significant importance. It should include energetic properties of the surface as well as differentiated geometrical structure, morphology and topography of the carbon deposit. These parameters determine adsorption properties to a great extent. The objects of our studies are carbon-silica adsorbents (carbosils) prepared by pyrolysis of CH2Cl2 on the mesoporous silica gel surface. Carbon deposits obtained in such a reaction are characterized by hardness, metallic lustre and good adhesion to the surface (carbons of type A according to the Kinney's classification). Extensive studies of structure and energetic properties of the surface of the carbosils including from 0.8 to 35% carbon were undertaken. The adsorbents were studied using the following methods: nitrogen adsorption and desorption at 77 K, flow microcalorimetry, electron paramagnetic resonance and small angle X-ray scattering measurements. The studies indicate that deposition of carbon takes place in pores and as aggregates without formation of compact layer on the surface of initial silica matrix. The obtained carbon deposit has a graphite-like structure and the surface of the studied adsorbents is characterized by strong energetical heterogeneity. (C) 2002 Elsevier Science B.V. All rights reserved.