Structures structure-directing agents

Quaternary ammonium compounds as structure directing agents in zeolite synthesis... 

The importance of quats as structure-directing agents in zeolite synthesis was recently underlined (ref. 5) by the synthesis of the new zeolites SSZ-26 and -33, which combine 10- and 12-ring pores. The templates applied are shown in Figure 3. 

Since then, organic amines, quaternary-ammonium bases, metal complexes, and other compounds have been extensively used in zeolite synthesis, acting as space fillers with low specificity, structure-directing agent, or true templates ... 

The same periodic structures can also be formed from alternating AIO4 and PO4 tetrahedra the resulting aluminophosphates are not called zeolites but AlPOs. Zeolites are made by hydrothermal synthesis under pressure in autoclaves, in the presence of template molecules such as tetramethylammonium, which act as structure directing agents. 

The Si-CHA samples were synthesized in fluoride medium and using /V.iV.iV-trimethyl adamantammonium (TMAda+) as structure-directing agent. The starting gel of molar composition 1 Si02 0.5 TMAdaOH 0.5 HF 3 H20 was introduced in a Teflon-lined stainless-steel autoclave and heated at 150°C during 90 h. After synthesis, the product was filtered, washed with distilled water and dried at 60°C overnight. The solid was... 

Al-containing ITQ-21 zeolite ((Si+Ge)/Al=25, Si/Ge=20) was synthesized using N(16)-methyl-sparteinium cation (MSPT+) as the organic structure-directing agent in combination with fluoride anions and germanium as described in [1], The composition of the final synthesis gel was ... 

Fig. 4 Proposed defect cluster model in as-made zeolites with quaternary ammonium cations as structure directing agents (SDAs) hydrogen bond distances of 1.68 A are determined experimentally from the H NMR chemical shift of 10.2 ppm X and Y are atoms not further specified in the SDA the interaction between the SDA and the SiO- group is assumed based on bond valence arguments (see text)...

Fig. 5 (a) Structure directing agent (SDA) in the synthesis of zeolite ITQ-3 N quaternary nitrogen A-I carbon atoms of SDA, l,3,3,6,6-pentamethyl-6-azonium-bicyclo[3.2.1]octane some 13C line assignments were not unequivocally possible, so these are left open the orientation of the dipole moment was calculated with a semiempirical AM-1 simulation with the origin at the center of gravity of the molecular cation (b) 13C H 27A1 REAPDOR experiment on synthetic zeolite ITQ-3. Adapted from [204]... 

Zeolite synthesis around a metal complex was introduced by Balkus [40]. The metal complex is added to the zeolite synthesis mixture and is incorporated into the zeolite structure during the zeolite synthesis. Of course, this procedure is only applicable when the metal complex is soluble in the synthesis mixture and can withstand the hydrothermal synthesis conditions. Another requirement is that the zeolite structure-directing agent added must be removable by a milder... 

Synthesis using TPABr as structure-directing agent and ammonia, water, hexanediamine, n-butylamine, diethylamine, ethylenediamine, or triethanolamine as base (seeds of TS-1 were added to get smaller crystallites and 100% crystallinity) Synthesis of fibrous titanosilicate... 

NMR OU PEO Ph PFD PO Q rpm RT SAPO SBA SBU SDA Nuclear magnetic resonance Osaka University Polyethylene oxide Phenyl Pulsed laser deposition Propylene oxide Quinuclidene Revolutions per minute Room temperature Silicoaluminum phosphate Santa Barbara Secondary building unit Structure directing agent... 

Liquid crystals as structure-directing agents have been used to produce mes-oporous Pt and PtRu materials. These unsupported materials (akin to metal blacks) have regular arrays of mesopores of 2.5 nm separated by 2.5 nm walls (see Figure 1.5). For Pt, high surface areas (60 m g ) have been produced these are significantly higher than those shown by commercial Pt blacks. 

The advent of the addition of a quaternary ammonium cation as template or structure directing agent (SDA) to the alkaline gel by Barter and coworkers, and Mobil Oil coworkers, led to the Si02 enriched zeolite A in the case of Barter and to the high silica zeolites. Beta and ZSM-5, by the Mobil group. The latter synthesis temperature typically is 100-200 °C, higher than Milton s original work. 

---