Template Removal from Polycrystalline Silicalite-1 Self-Supporting Layer

The extent of thermal template (tetra-propyl-ammonium: TPA+) removal from a silicalite-1 layer by heating in air was investigated. While a temperature of 330 °C was sufficient to eliminate all N-containing template species from the surface region of the layer (i.e., within a depth of ≈10 nm), their complete elimination from the bulk even at 550 °C was not achieved. This was caused by a series of reactions proceeding at high temperatures, involving the products of TPA+ thermal degradation. A substantial amount of C-containing template species remained in the sample even after a thermal treatment at 550 °C. A role the SiO2 phase of low organization present in the silicalite-1 layer plays in the retention of the products of thermal degradation has been proposed. Additionally, the stability of TPA+ irradiated by microwaves was examined. Only minor morphological changes of the layer upon thermal template removal were revealed by atomic force microscopy.