The Synthesis And Crystal Morphology Controlling Of Zeolite-l

Zeolite L is a particular molecular sieve from the zeolite family. It possesses one-dimensional pore of about 0.71nm aperture. And zeolite L can be used as a host-nanogueset composite materials, and catalyst in the process of catalytic cracking, hydro-cracking and isomerization, which attracted much interest in the field of catalyst materials. Studies show that the properties of zeolites and related crystalline porous materials are strongly affected by the size and morphology of the crystals. Therefore, it is necessary to develop the synthetic strategies for the control of crystals size and morphology of the inorganic materials and zeolites.In this study, different Si and Al sources were used as starting materials to prepare L-type zeolite. Synthesis and the effects of different raw materials on morphology of zeolite L were also investigated. It was found that the phrase structure, crystal morphology of zeolite L were various for synthesizing by different sources. The economical and reasonable combination mode was found when we use powdered silicon dioxide as Si source and potassium aluminate as Al source upon heating at 150°C for 24h and its starting molar gel composition was 4.2K₂O·Al₂O₃·14SiO₂·189H₂O. But the particle size of produced L type zeolite under such conditions was small and its relative crystallinity was low, and with mixed crystal and filtration problem. In addition, zeolite L with high relative crystallinity and sprcial crystal shape was synthesized with sodium silicate and silicon dioxide as compound Si source which was firstly investigated.Alcohol compounds, cationic surfactant CTAB, anionic surfactant SDS, compound additive CTAB/glycerol were added into the gel system for investigating the effect of additives on morphology and relative crystallinity of zeolite L. The use of little additive led to the formation of crystals whose morphology have been changed obviously. Most of the crystals which were produced with the addition of alcohol compounds can be describe as a typical clam-shaped crystal of domed basal plane. Cationic surfactant CTAB led to cylindrical shape crystal with salient basal plane, whereas anionic surfactant SDS can not lead to produce L type zeolite. With the exception of SDS, all additives led to higher relative crystallinity and faster filtration rate.Most of industrial applications require zeolites with a low cost and friendly to the environment. Ethanol is one of excellent additive in the synthesis of zeolite L because of its low boiling point, low price and the properties of poisonless and harmless.The effect of ethanol addition amount on the morphology and crystallinity of zeolite L was investigated. The test of SEM and X-Ray showed that regular crystals were obtained with the addition of 2% ethanol of volume fraction,and its relative crystallinity reached 92%.Based on this study, the effect of molar composition in the starting gel, reaction temperature, time on the synthesis of zeolite L were also studied in this paper. A large scale synthesis was carried out in a 2-litre reactor under the optimized conditions. The pilot synthesis of zeolite L was successful for its good experimental repetition and these will increase their prospect of industry.