Molecular sieve macrostructures prepared by resin templating

Abstract: A novel template-based method for the preparation of molecular sieve macrostructures was developed. Silicalite-1, ZSM-5 and zeolite beta spheres were prepared by the method. The procedure was also used to produce amorphous silica macrostructures. Anion exchange resin beads were employed as macrotemplates to host the guest silica materials. Generally, the method consists of three steps: (i) introduction of silicate (aluminosilicate) material into the resin beads by ion exchange; (ii) secondary treatment to convert the inorganic material into a desired form; and (iii) removal of the ion exchanger by calcination. The first two steps may be performed simultaneously by hydrothermally treating a mixture of resin beads and e.g., zeolite synthesis solutions. In the course of the treatment, the inorganic material, initially exchanged within the resin beads, is transformed into a zeolite in the presence of the zeolite structure-directing agents. The steps may also be separated by first treating the ion exchanger with asilica solution, e.g., sodium silicate solution, and then converting the silica into a molecular sieve by secondary treatment with a zeolite structure- directing agent. Upon calcination, the ion exchange resin and the structure- directing agents are removed leaving highly porous macrostructures with a shape determined by the shape of the resin templates. The influence of different parameters on the properties of the final products was studied by various techniques such as X-ray diffraction, scanning electron microscopy, Raman spectroscopy and nitrogen adsorption measurements. Experiments were performed using different types of anion exchange resins (macroporous, gel, strongly basic, weakly basic) and different synthesis conditions (different synthesis solutions, temperatures, treatment times, solution to resin weight ratios, etc.). The materials prepared are of interest for application as catalysts and catalyst supports, selective adsorbents, packing materials in column liquid chromatography, etc.