Effects of Gel Parameters on the Synthesis and Characteristics of W-Type Zeolite Nanoparticles
The objectives of this study were to investigate the effects of chemical parameters on the characterizationof W-type zeolite crystals and their intergrowths with other types of zeolites. The crystal size and purity ofW-type zeolites are affected significantly by the gel composition with respect to the molar ratios of SiO2/Al2O3 (aluminosilicate module, α), H2O/K2O (alkainity, β), and water content (H2O/SiO2, γ). The effects of these gel parameters ont he synthesis and characterizationof W-type zeolite were investigated.
Crystalline W-type zeolite of high purity was synthesized using a gel with a molar ratio of Al2O3:6.4SiO2:5.6K2O:164.6H2O at T = 165°C for a period of 72 h. The effect of excess K2O/SiO2 ratio ina mono-cation (K)-SiO2-Al2O3 gel-composition system on the nanoparticle size and purity of the product was also investigated. Experiments were carried out using the following levels of alkalinity: 21.4, 29.4, and 51.9; aluminosilicate module: 5.0, 6.4, and 10.0; water content: 16.5, 25.7, and 32.9; and excess K2O/SiO2 ratio: from 0.65 to 3.33. The results showed that by increasing the aluminosilicate module at high K2O/SiO2 ratio, the crystallinity and crystal size of the zeolite synthesized increased, while at low alkalinity, the crystallinity and crystal size decreased. Decreasing alkalinity at low aluminosilicate module increased the crystallinity and decreased the crystal size, while at high aluminosilicate module, both decreased. Finally, by increasing the water content at all aluminosilicate module and alkalinity values, the crystallinity and crystal size of the W-type zeolite increased. Excess K2O/SiO2 ratio was the key factor that should be adjusted int he range 0.7–1.0 for synthesis of pure crystals of W-type zeolite.
Key WordsCrystallinity Gel Parameters Nanoparticle Size Optimum Gel Compositions W-type Zeolite
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- Baerlocher, Ch., Meier, W.M., and Olson, D.H. (2001) Atlas of Zeolite Framework Types. Elsevier, New York.Google Scholar
- Barrett, P.A., Valencia, S., and Camblor, M.A. (1998) Synthesis of a merlinoite-type zeolite with an enhanced Si/Al ratio via pore filling with tetraethylammonium cations. Journal of Material Chemistrys, 82, 263–2268.Google Scholar
- Cejka, J., Bekkum, H.V., Corma, A., and Schüth, F. (2007) Introduction to Zeolite Science and Practice. Elsevier, New York.Google Scholar
- Galli, E., Gottardi, G., and Pongiluppi, D. (1979) The crystal structure of the zeolite merlinoite. Neues Jahrbuch für Mineralogie, Monatshefte, 1–9.Google Scholar
- Milton, R.M. (1961) Crystallization zeolite. US Patent 3012853.Google Scholar
- Passaglia, E., Pongiluppi, D., and Rinaldi, R. (1977) Merlinoite, a new mineral of the zeolite group. Neues Jahrbuch für Mineralogie, Monatshefte, 355–364.Google Scholar
- Robson, H. (2001) Verified Syntheses of Zeolitic Materials. Elsevier, New York.Google Scholar
- Sand, L.B. (1978) Synthetic Zeolite. US Patent 4093699.Google Scholar
- Treacy, M.M.J. and Higgins, J.B. (2007) Collection of Simulated XRD Powder Patterns for Zeolites. Elsevier, New York.Google Scholar