The Role of Template Structure and Synergism between Inorganic and Organic Structure Directing Agents in the Synthesis of UTL Zeolite

The extra-large-pore germanosilicates with UTL topology have been synthesized using a large variety of spiroazocompounds as structure-directing agents. Synthesis conditions were optimized and zeolites with a high crystallinity degree were obtained with 13 different organic structure-directing agents. The influence of the composition of the reaction mixture and template nature (structure, hydrophilicity/hydrophobicity balance, rigidity, pK(a)) on the phase selectivity, crystallinity degree, and adsorption properties of zeolites with UTL structure was investigated. Selection criteria of organic molecules as potential structure-directing agents (SDAs) in the synthesis of large-pore and extra-large-pore zeolites from silicate and germanosilicate media are proposed. The optimum synthesis time was determined to be 4-9 days for different SDA and (Si + Ge)/SDA molar ratios. Clear synergism between the optimum structure of organic template and the presence of critical amount of inorganic component (GeO2) was evidenced. The UTL zeolite crystallizes as tiny sheets 10 pm thick. The effect of the organic template on the size and shape of the crystals was found. The micropore volume of the best crystals is 0.22-0.24 cm(3)/g, with a micropore diameter of 1.05 nm, based on density functional theory (DFT), and Saito-Foley analyses of adsorption isotherms.