PREPARATION AND CHARACTERIZATION OF HOLLOW FIBERS OF SILICALITE-1

Hollow fibers consisting solely of silicalite-1 were prepared by a nav el method consisting of Sour basic steps. Carbon fibers were first sur face modified to facilitate adsorption of colloidal seed crystals of s ilicalite-1, Such particles were then adsorbed as a monolayer on the f iber surface and induced to grow into a continuous film of intergrown crystals of silicalite-1. Finally, the carbon fiber used as a template was removed by calcination in air, yielding hollow fibers of silicali te-1. Hollow fibers were prepared in two experimental series employing different synthesis conditions resulting in two different modes of gr owth. The first experimental series was performed with a clear homogen eous TPAOH/silica solution crystallizing at 100 degrees C, and the sec ond series with a NaOH-TPABr/silica gel crystallizing at 150 degrees C . Materials produced in the first series showed a smooth and homogeneo us surface and a relatively uniform fiber wall with a final thickness of 1.1 mu m In these materials ?he film was formed by crystals growing outward from the surface of the carbon fiber. Materials produced in t he second series were less uniform with a final thickness of the fiber wall of about 3.2 mu m. The crystal growth in these materials appeare d to take place both in an inward and outward direction starting from the seed crystals adsorbed on the carbon fiber. ?he hollow fibers prep ared were characterized by SEM, XRD, FT i.r., and nitrogen adsorption measurements. (C) Elsevier Science Inc. 1996