Polymer-derived ceramic foams with a zeolitic surface by supported crystallization

Open cell polymer derived ceramic foams were prepared by a self-foaming process of filler-loaded polysiloxanes and subsequent pyrolysis at 1000 degreesC-1400 degreesC in argon atmosphere. SiO2 was used as particulate filler. The open cell ceramic foams with an average cell diameter from 0.5 to 1.5 mm, a compressive strength up to 3 MPa and a porosity of up to 90% were used as support for direct zeolite crystallization under partial dissolution/recrystallization of the ceramic foam. The partial transformation of the Si-O-C based foam material by hydrothermal crystallization at 150 degreesC for 12 h-96 h resulted in a dense zeolite coating with excellent adhesion on the foam surface. The morphology of the zeolite crystals was controlled by the synthesis parameters: reaction solution-to-foam ratio, pH-value, ceramic foam composition and crystallization time. The zeolite/foam composites are supposed for the use in gas separation and heterogeneous catalysis.