Synthesis from gels

ETS-10 synthesis from gels containing TiF4 and Ti02 (343)... 

The amount of boron substitution achieved using this post-synthetic method is approximately six times higher than the most heavily substituted mordenite prepared by direct synthesis from gels (vide supra). If this post-synthetic treatment... 

We prepared boron substituted mordenite by direct synthesis from gel precursors and by post- synthetic substitution into dealuminated mordenite. Direct substitution is favored in aluminum deficient gels, but exacting crystallization requirements for mordenite formation limit the amount of boron that can be incorporated into the framework structure. Higher substitution levels were achieved using a post-synthetic treatment. Boron substituted zeolite Y could not be prepared by a similar direct synthetic method, but post-synthetic methods were effective at providing low substitution levels. This demonstrates the more general utility of post-synthetic substitution methods. The hexane cracking activity of... 

Al/Si ratio—viz, 1/2. However, there have been no ion exchange investigations of the systems, Na-K, Na-Ca, or K-Ca in analcites of higher or lower than normal Al/Si ratios. Whereas earlier attempts to effect cation exchange of normal analcite by Li, Cs, Mg, Ca, and Ba were met with only limited success, indirect methods of exchange or direct synthesis from gels provided means whereby Li, K, Ca, Cs, and Pb2+ forms were said to have been obtained (1, 3, 4, 5). 

Within the crystallisation field of a given zeolite, increasing the alkalinity has a similar effect upon the kinetics of crystallisation as a rise in temperature. This is illustrated in Fig. 8 [69] for mordenite synthesis from gels at a series of increasing pH values. This figure is to be compared with Fig. 1 for the same zeolite at a series of increasing temperatures. Fig. 8 also shows that at pH 13.3 the mordenite first formed dissolves. Its succesor is analcime. 

The S-1 and TS-1 were synthesized from gels containing a mixture of TEOS, tetraisopropoxytitanium, and TPAOH. H2O2 was only added for the synthesis of TS-1 containing 3.4wt% Ti [9]. Hydrothermal crystallization, filtration and ctilcination at 540°C... 

Seeding technique. Al-free Ti-beta obtained by use of dealuminated zeolite-beta seeds Fluoride method. Al-free Ti-beta synthesis from a reaction mixture containing TEAOH and fluoride ions (HF) at near-neutral pH. Gel composition Ti02 60SiO2 32.9NEt4OH 32.9HF 20H2O 457.5 H20. Crystallization at 413 K with rotation of the autoclave (60 rpm)... 

Six ZSM-5 samples were synthesized from gels containing the whole series of alkali cations, added in form of chloride, as described in procedure B. Synthesis data, principal properties and analyses are summarized in Tables VI and VII. 

Adenosine triphosphate (ATP) is one of the most important cofactors involved in many of the synthetic reactions going on within the cell. Its recent large scale in vitro enzymatic synthesis from adenosine and acetylphosphate is of particular interest. Three enzymes immobilized in polyacrylamide gel were used adenosine kinase, adenylate kinase and acetate kinase (lip. ... 

An alternative hypothesis, developed from studies of the synthesis of Linde A zeolite carried out by Kerr (5) and Ciric (6), pointed to growth occurring from solution. The gel was believed to be at least partially dissolved in solution, forming active aluminosilicate species as well as silicate and aluminate ions. These species linked to form the basic building blocks of the zeolite structure and returned to the solid phase. Aiello et al. (7) followed the synthesis from a highly alkaline clear aluminosilicate solution by electron microscopy, electron diffraction, and x-ray diffraction. These authors observed the formation of thin plates (lamellae) of amorphous aluminosilicates prior to actual crystal formation. 

The high-pressure polyimide synthesis from salt monomers was extended to the development of a new approach for hybrid materials composed of aliphatic polyimides and silica, wherein this method was combined with the sol-gel process [63,64]. The preparation process is outlined in Scheme 2, where aliphatic polyimide P-9PM was used as the polyimide component. 

In the course of pentasil zeolite ZSM-5 synthesis, the gel mixture obtained from starting aqueous solution is a low density precipitate, which is different from the hydrogelatinous state in ZSM-34 synthesis it can be easily separated from the supernatant fluid by centrifuge. 

ECR-1 crystallizes in the presence of DHEDM and DHPDM from gels which would normally yield Y-faujasite in the absence of any organic template. The best products crystallized in the composition range with Si/Al between 3 and 6, at temperatures between 120°C and 160°C, using a seed nucleant solution (IS.). Synthesis of DHEDM ECR-1 was made from a gel stoichiometry of ... 

The entire spectrum of tools in synthetic inorganic chemistry, including high temperature methods, precipitation, solvothermal synthesis, sol-gel chemistry, chemical vapor deposition (CVD), and soft matter techniques adopted in part from organo-metallic chemistry, have been applied to synthesize the active mass of catalysts. Table 4.2.1 summarizes basic techniques. The preparation methods differ whether... 

The literature indicates that another catalysis-related mode of application has become prominent. It has been recognized that the synthesis of active phases can be understood and optimized on the basis of XRD measurements of catalyst synthesis mixtures and determination of phases and transformation kinetics. A prominent set of examples (Bazin et al., 2002 Chen et al., 2005, 2006 Davidson, 2002 Kleitz et al., 2002 Liu et al., 2005 Palancher et al., 2005 Valtchev and Bozhilov, 2004) is grouped around the formation of mesoporous solids from gels with templates. Such data allow an optimum choice of parameters for obtaining a desired phase. The ability of these methods to detect catalytically relevant phases in complex systems is illustrated in Figure 6. 

Fig. 9 Alginate technique for synthesis of gel beads ranging from 102 to 103 pm. An aqueous solution containing PVME and alginate is dropped into a calcium chloride solution to form gel beads. (Reproduced from [46], copyright Wiley-VCH, reproduced with permission)...

The effect of mechanical activation on mullite synthesis from the mixtures of aluminium hydroxide and silica gel was studied in [32,39]. They demonstrated that under heating of nonactivated mixtures, the components undergo phase transformations similar to those observed for individual compounds. Mullite is synthesized at 1400°C. 

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