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, p K 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 (GeO 2 ) was evidenced. The UTL zeolite crystallizes as tiny sheets ∼10 μm 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.