Searching for new high silica zeolites through a synergy of organic templates and novel inorganic conditions

Zones, Stacey I.; Nakagawa, Y.; Lee, G.S.; Chen, C.Y.; Yuen, L.T.

doi:10.1016/s1387-1811(98)00011-0

Cited by 93 publications

(55 citation statements)

References 21 publications

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“…Therefore, we can state that on the atomic and colloidal scale diatomaceous silica is amorphous. Consequently, in mimicking diatomaceous silica, we do not have to face difficulties of the formation of crystals, which is essential in zeolite synthesis van Bekkum et al 1991;Zones et al 1998). …”

Section: X-ray Diffraction and Wide-angle X-ray Scatteringmentioning

confidence: 99%

Silicon Biomineralisation: Towards Mimicking Biogenic Silica Formation in Diatoms

Vrieling¹,

Hazelaar²,

Gieskes

et al. 2003

Silicon Biomineralization

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IntroductionSilica is by far the most abundant compound in the earth's crust. It serves various functions in nature: organisms ranging from lower eukaryotes to plants use it as one of the biominerals that provide support, protection, strength, or tools in various functions. Biogenic silica is the least studied of the biominerals. The best-studied ones (Hunter 1996) are composed of calcium (apatite, enamel, calcite); these are present in the bone tissue and teeth of mammals and in the shells of shellfish. In contrast to calcium minerals, relatively little is known about the formation of biogenic silica. The most likely function of biogenic silica in unicellular organisms seems to be giving strength to the living cell; good examples from the aquatic environment are siliceous (exo)skeletons or cell casings of the microalgal groups of diatoms ( Fig. 1) and silicoflagellates, and of Radiolaria (Simpson and Volcani 1981; Pickett-Heaps et al. 1990;Round et al. 1990).Silica and silica-based materials (e.g. zeolites and MCM-type materials) are also widely used in a variety of industrial and technological applications. A limited number of micro-and mesoporous silicas serve as fillers in rubber materials (e.g. in tyres), as catalyst supports, as drying agents, as abrasives (e.g. toothpastes), or as filters in separation technologies (Iler 1979;Brinker and Scherer 1990;Bergna 1994). A prerequisite for each application is that a silica with specific properties of mechanical strength, pore volume, pore-size distribution, or specific surface area is required. The current demand for "the best" silicas in these respects is increasing and a search for new, improved or alternative artificial silica materials has been going on for a few years. Biogenic silica sources also have received more attention lately (Morse 1999;Vrieling et al. 1999b). It is expected that if nature can be mimicked, a wide range of innovative and new tailor-made silicas can be produced approaching the variety in architecture seen in nature, e.g. in the algal class of diatoms (Vrieling et al.

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Section: X-ray Diffraction and Wide-angle X-ray Scatteringmentioning

confidence: 99%

Silicon Biomineralisation: Towards Mimicking Biogenic Silica Formation in Diatoms

Vrieling¹,

Hazelaar²,

Gieskes

et al. 2003

Silicon Biomineralization

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“…[6][7][8] The inclusion of the organic molecules is usually required to direct the crystallisation of a certain microporous structure, and so they are called structure-directing agents (SDAs).…”

Section: Introductionmentioning

confidence: 99%

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Gómez‐Hortigüela

Pérez‐Pariente

Corà

2009

Chemistry A European J

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A combination of experimental characterisation techniques and computational modelling has allowed us to gain insight into the molecular features governing structure direction in the synthesis of microporous aluminophosphates. The occlusion of three different structure-directing agents (SDAs), triethylamine (TEA), benzylpyrrolidine (BP) and (S)-(-)-N-benzylpyrrolidine-2-methanol (BPM), within the AFI structure during its crystallisation, together with the simultaneous incorporation of water, has been experimentally measured. We found a higher incorporation of organic molecules in the structure obtained with BPM, while a higher water (and lower organic) content is found for the ones obtained with TEA and BP as SDAs. The computational study provides a thermodynamic explanation for the observed behaviour in terms of the relative stabilisation energy of the SDAs and water molecules within the AFI framework compared with when they are in aqueous solution, and demonstrates that a competition for preferential occupation exists between water and organic SDAs, which is a function of the interaction with the inorganic framework. The lower interaction of TEA and BP molecules with the AFI structure promotes the simultaneous incorporation of water molecules in the 12-membered-ring (MR) channel, to increase the host-guest interaction energy and thus the thermodynamic stability. The presence of strongly interacting methanol groups in the BPM molecules leads to the incorporation of only organic molecules within the 12-MR channels. Our results demonstrate the essential role that water molecules play in the stabilisation of hydrophilic microporous aluminophosphates; a minimum amount of organic SDA is, however, essential for a templating role of the microporous architecture.

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“…There is great interest not only in the zeolites synthesis with new crystalline structures (Shantz et al, 1999;Zones et al, 1998;Yoshikawa et al, 1998) but also in the development of synthesis techniques to adjust the catalytic and adsorption properties of existing materials (Zhang et al, 2000;Armor, 1998;Smirniotis and Zhang, 1996). Basically there are two guest ways of altering the physicochemical properties of a zeolite:…”

Section: Introductionmentioning

confidence: 99%

Crystallization of ZSM-12 Zeolite with Different Si/Al Ratio

et al. 2005

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In this work the acid properties of a series of HZSM-12 zeolites with different Si/Al ratio were studied. The ZSM-12 crystals were synthesized by the hydrothermal method starting from a gel with the following molar composition: 20MTEA:10Na 2 O:x Al 2 O 3 :100SiO 2 :2000H 2 O, with x = 0.50, 0.67, 1, 1.25 and 2, respectively. The gels were crystallized at 140 • C for 6 days, then washed, dried and calcined to remove the MTEA template. The samples were ion-exchanged with an ammonium chloride solution and calcined again to obtain the zeolites in the acid form. The materials thus obtained were characterized by XRD, SEM, BET, TG and n-butylamine adsorption. The Si/Al ratio in the reaction mixture affects the amount of zeolite produced and the size of the particles. The XRD analysis indicated that the ZSM-12 zeolite crystallizes in a pure form only with Si/Al ratio above 33. The SEM analysis showed the presence of crystallites with very well defined prismatic shapes. The removal of the MTEA of the pores of the ZSM-12 by TG indicated that there are two kinds of internal sites occupied by MTEA inside the structure. The BET area of the ZSM-12 decreases proportionally with the crystallinity of materials. The desorption of n-butylamine showed that the acid site density is proportional to aluminum content, but the Si/Al ratio shows little influence on the relative strengths of these sites.

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Searching for new high silica zeolites through a synergy of organic templates and novel inorganic conditions

Cited by 93 publications

References 21 publications

Silicon Biomineralisation: Towards Mimicking Biogenic Silica Formation in Diatoms

Silicon Biomineralisation: Towards Mimicking Biogenic Silica Formation in Diatoms

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

Crystallization of ZSM-12 Zeolite with Different Si/Al Ratio

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