Effect of Additives on the Synthesis of Zeolite L
|Keywords||Zeolite L Hydrothermal Synthesis Complexing agent Fluoride route Morphology|
The unique structure of the zeolite L has decided that it can be used in industries such as catalysts and adsorbents. At present, most attention is the catalyst carrier as a reformer, aromatization and cyclization process. In recent years, an additive to the synthesis of zeolite L has been reported, there are reported in the literature to add alcohol amine and fluoride synthesis of zeolite L, but these references are not additive effects of a systematic study, did not give specific data. Therefore, on the basis of previous studies, the system to study the influence of additives on the synthesis of zeolite L. This thesis the cheap silica, aluminum hydroxide, potassium hydroxide, and deionized water as raw material, the use of hydrothermal crystallization synthesis of zeolite L. The initial ratio of 4.2K2O · Al2O3 · 14SiO2 · 189H20, the crystallization temperature of 150 ° C, crystallization time 24h. Select triethanolamine, potassium fluoride, sodium fluoride, ammonium fluoride, ammonium fluorosilicate examine its impact on the synthesis of zeolite L as additive. Fluoride is added: The results show that in the low alkali i.e. K2O/Al2O3 to 3.0, and the high silicon i.e. SiO2/Al2O3 is raised to 18, without using the additive synthesis sample is an amorphous substance; synthesized when adding a relatively large amount of a fluoride ion The sample has a diffraction peak of the zeolite L, but the intensity is weaker. The fluoride ion plays an important role in the mineralization of, which can expand the synthesis interval. The introduction of trace or excessive fluoride ion inhibits the formation of zeolite L, will also promote the formation of impurity crystals. This is a new phenomenon in synthetic zeolite L. Add triethanolamine results show that: when K2O/Al2O3 of 3.3, without additives can be preferably synthetic crystalline zeolite L, the degree of crystallization after the addition of triethanolamine decreased to continue to reduce the alkalinity ADD triethanolamine can not synthesize L zeolite. In this case, the synthesis interval triethanolamine added narrowing, this is due to the triethanolamine in the synthesis with the aluminum ion complexing inhibit crystal nucleation, but the amount of triethanolamine little impact on the synthesized. Morphology and grain size of the SEM to examine the samples. The results show that: triethanolamine is added to make more regular morphology, particle size uniform and large particles than no additives, more uniform particle size distribution; regular morphology of sample introduction of fluoride ions, the grain surface is smooth and clean, relatively evenly distributed but the grain size be increased. Synthetic samples skeleton characterized by infrared spectroscopy, the results prove that there is some connection between the vibrational peak and the crystallinity of the skeleton. Good degree of crystallinity of zeolite L has only the L zeolite infrared peaks, if will be more than a few non-zeolite L containing miscellaneous crystal absorption peak. This indicates that can be used to identify the infrared spectra of zeolite L.