From a naturally occurring-clay mineral to the production of porous ceramic membranes

Abstract

A silicalite clay composite membrane was produced by hydrothermal deposition using tetraethyl orthosilicate (TEOS) as silica source, tetra-n-propylammonium bromide (TPABr) as template and KOH as mineralizing agent. Silicalite was deposited in the mesopores and on the surface of porous ceramic membrane supports made from a naturally available clay mineral abundantly found in the central region of Morocco (Meknès). Three flat-disc membrane supports were prepared by uniaxial pressure on pure clay powder (AS), mixture of clay and activated carbon (5%, w/w) (AC) and mixture of clay and starch (20% w/w) (AA). The porosity of membrane supports was studied as function of the final calcination temperature. It was found that the mesopores contribution to porosity was 25%, however their contribution to the specific surface area is more than 90%. The mesopores structure was investigated. XRD confirms the formation of crystalline silicalite layers inside the mesopores of the clay flat-disc supports. Typical MFI-type zeolite morphology was confirmed by SEM. The scope and limitations of the membranes in terms of selectivity between SF6 and N2, is discussed.