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

Abstract

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 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 cm3/g, with a micropore diameter of 1.05 nm, based on density functional theory (DFT), and Saito−Foley analyses of adsorption isotherms.

Atomic Force Microscopy of Novel Zeolitic Materials Prepared by Top‐Down Synthesis and ADOR Mechanism

“…[25] The reaction gel was prepared as followed: template (6R,10S)-6,10-dimethyl-5-azoniaspiro [4.5]decane (67.83 g) was dissolved in water (500 g) and the template was ion-exchanged into HO À form using AG 1-X8 resin (Bio-Rad). Then, GeO 2 (38.76 g) was dissolved in the solution of template and SiO 2 (Cab-O-Sil M5, 44.5 g) was added.…”

Germanosilicate UTL and its rich chemistry of solid-state transformations towards IPC-2 (OKO) zeolite

“…The molar composition of the reaction gel for all UTL was Si/Ge = 2 [33,34], for Al-UTL Si/Ge = 2, (Si + Ge)/Al = 96 [35], for B-UTL in 3b Si/Ge = 1.7, (Si + Ge)/B = 9, in 4a Si/Ge = 1.2 and (Si + Ge)/B = 6.7, and in 4b Si/Ge = 1.9 and (Si + Ge)/B = 32) [35,36].…”

Effect of pyrazolium-derived compounds as templates in zeolite synthesis

“…[16][17][18][19] Recently, much progress has been made to design distinctive organic templates, among which diquaternary ammonium is a kind of important templates with good exibility and feasibility. [20][21][22][23][24][25][26] Its end groups and chain length can be selectively altered to facilitate the formation of diverse microporous topology, and even sometimes to tailor the crystal morphology or mesoporosity. Thereinto, Moini et al investigated the directing role of (CH 3 ) 3 N + (CH 2 ) n N + (CH 3 ) 3 by regulating (CH 2 ) n length, in which they found that EUO zeolite can be produced with n ¼ 5, 6, NEI zeolite with n ¼ 10, MTT zeolite with n ¼ 7, 8, 9, 11, 12, and MTW with n ¼ 9, 14.…”