Synthesis and characterization of zeolite coatings on monolith supports

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Ceramic monoliths with binderless zeolite coatings have great potential as catalysts for structured catalytic reactors. Advantages over packed beds are a low pressure drop, high selectivity and less mass and heat transport limitations. A novel synthesis method, called the seed film method, was used to coat cordierite monoliths with thin films of ZSM-5. Basically, the monoliths were coated in a three-step procedure. In the first step the monolith surface was coated with a polymer to be able to adsorb seed crystals in the second step. Finally, the seeded supports were hydrothermally treated in a synthesis solution to induce growth of seed crystals into a dense and continuous film. The films were characterized with scanning electron microscopy, X-ray diffraction, gas adsorption and thermal analysis. Films with thickness ranging from 270 to 800 nm were obtained. Several hydrothermal treatment steps and/or an elevated synthesis temperature were used to obtain the thicker films. Zeolite loading and film morphology could be varied with ultrasonic treatment. The use of ultrasound treatment improved the removal of surface-attached crystals in addition to rinsing with aqueous NH3. Th...