Synthesis of zeolitic mesoporous materials by dry gel conversion under controlled humidity

A new variation to the dry gel conversion method for the preparation of zeolite is introduced, where the conversion to zeolite was accomplished under water vapor below the saturation condition. The dry gel was made either by vacuum concentration or by surfactant flocculation from a silica precursor sol after the preliminary hydrothermal step. Depending of the humidity under which the conversion took place, mesoporous structures with varying MFI crystallinity, BET, and crystalline external surface areas were produced. The effects of precursor preparation and surfactant flocculation conditions on mesoporosity and crystallinity of the final product, as well as the steam stability of the product, were also investigated. The approach could find general application in the synthesis of other zeolites as well as metal oxides.