Effect Of Additives On The Synthesis Of Zeolite L

The unique framework of zeolite L decides it can be used for catalysts, adsorbents and other industries. Currently, the most noticeable application is used in reforming, aromatization and dehydroge nation cyclization process as a catalyst. In recent years, the synthesis of zeolite L though adding additives have been reported, such as adding fluoride and alkanolamine, but these literature neither systematically studied the effect of additives nor gave specific data. Therefore, on the basis of previous research, this article systematically investigates the effect of additives on the synthesis of zeolite L.In this thesis, zeolite L was synthetized from the raw materials such as powdered silicon dioxide, aluminum hydroxide, potassium hydroxide and deionized water using hydrothermal method. In this condition, the initial ratio was 4.2K2O·Al2O3·14SiO2·189H2O, crystallization temperature 150℃and crystallization time 24h. We selected triethanolamine, potassium fluoride, sodium fluoride, ammonium fluoride and ammonium fluosilicate as additives and studied their impact on the synthesis of zeolite L. The results of adding fluoride showed that a low alkali that K2O/Al2O3 reduced to 3.0 and a high silicon that SiO2/Al2O3 increased to 18,the synthetic samples was amorphous without additives. The synthetic samples had characteristic diffraction peaks of zeolite L with relatively large of fluoride added, but the strength was weaker. In this process, fluorinion played an important role in mineralization, which can expand the synthetic range. The introduction of trace or excess fluorinion can inhibit the formation of zeolite L, at the same time, it also can promote the formation of miscellaneous crystal. This was a new phenomenon in the synthesis of zeolite L. The results of adding triethanolamine showed that when K2O/Al2O3 reduced to 3.3, we synthetized zeolite L with better crysta llinity without additives.While with triethanolamine added, the crystallinity decreased, and zeolite L could not be synthesized with the alkalinity reduced continuously. At this moment, synthesis interval was narrowed, for the triethanola mine complexed with aluminum ion, and inhibited crystal nuclcation. But the amount of triethanolamine had no notable effect on the synthesis of zeolite L.Morphology and grain size of the sanples were investigated by SEM. The results showed that adding triethanolamine made morphology more regularly, particles larger and particle size distribution more uniform compared with no triethanolamine. The introduction of fluoride made the samples morphology regular, the grain surface smooth and clean, the distribution relatively uniform,and the grain larger.The frame of synthesized samples was characterized by IR spectra. The results prove that the vibration peak of the sample skeleton had some connection with crystallinity. Zeolite L with well crystallinity had only infrared characteristic peaks of zeolite L, if the sample contained miscellaneous crystal, there were several absorption peaks of non-L zeolite. This showed that zeolite L could be identified by infrared spectroscopy.