CHARACTERIZATION OF OFFRETITE MODIFIED BY SILANATION WITH TETRAMETHOXYSILANE AND OCTAMETHYLCYCLOTETRASILOXANE

Offretite has been modified (silanated) with octamethylcyclotetrasilox ane (OMCTS) and tetramethylsiloxane (TMS) using an improved CVD method . The parent and silanated offretites were characterized by scanning e lectron microscopy, X-ray diffraction, i.r. spectroscopy, microporous volume determination, and stepwise thermal desorption of ammonia. OMCT S and TMS agents transform the more accessible silanol groups into [GR APHICS] grafted groups, respectively. OMCTS was found to be a suitable agent for the selective silanation of external acidic sites, leading to unilayer grafting of the surface without reducing the internal site number and the intracrystalline zeolite voids.