Preparation and characterization of hollow fibers of silicalite-1

Hollow fibers consisting solely of silicalite-1 were prepared by a navel method consisting of Sour basic steps. Carbon fibers were first surface modified to facilitate adsorption of colloidal seed crystals of silicalite-1, Such particles were then adsorbed as a monolayer on the fiber 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 silicalite-1. Hollow fibers were prepared in two experimental series employing different synthesis conditions resulting in two different modes of growth. The first experimental series was performed with a clear homogeneous TPAOH/silica solution crystallizing at 100 degrees C, and the second series with a NaOH-TPABr/silica gel crystallizing at 150 degrees C. Materials produced in the first series showed a smooth and homogeneous 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 the 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 appeared to take place both in an inward and outward direction starting from the seed crystals adsorbed on the carbon fiber. ?he hollow fibers prepared were characterized by SEM, XRD, FT i.r., and nitrogen adsorption measurements. (C) Elsevier Science Inc. 1996