In situ construction of an immobilized b-oriented titanium silicalite spherical molecular sieve membrane

Abstract

Oriented molecular sieve membranes prepared on the surface of a specifically shaped substrate have been applied in the separation and catalysis process, but there is no report on the directional growth of molecular sieve membranes on the surface of spherical substrates. Here, a simple in situ crystallization method was employed to successfully prepare a single layer of b-oriented continuous titanium silicalite-1 (TS-1) molecular sieve membrane on the surface of 2-mm alumina beads. First, a titania intermediate layer was loaded on the surface of beads by the dipping method, and the surface was then modified with the TBOT modification solution. The ratio of the precursor solution was n(TEOS):n(TBOT):n(TPAOH):n(H2O) = 1:0.010:0.15:40 and was crystallized at 180 °C for 72 h to prepare the membrane. The content of the templating agent and water affected the size of TS-1 crystal grains and membrane crosslinking—both in turn influenced the continuity and orientation of the molecular sieve membrane. Spherical membrane catalyst was applied to catalyze the epoxidation of chloropropene in a fixed bed reactor, and the conversion of hydrogen peroxide and selectivity of epichlorohydrin attained 87.4% and 93.2%, respectively. This work provides a foundation for the design of novel TS-1 immobilized catalyst.