Synthesis Of Zeolite T Using Water Glass As Silica Source

Zeolite T belongs to the small pore zeolite category. It has important applications ascatalyst in the reaction of light hydrocarbon and as sorbent in adsorption/separation processfor its unique acidity, good thermal stability. However, there are few reports about theresearch of zeolite T. Many problems in the synthetic process and application of zeolite T arestill unclear. Therefore, it's necessary to invetigate zeolite T systematicly. In this paper,zeolite T was firstly synthesized hydrothermally by using water glass and industrialaluminium sulfate as raw materials.Two systems that using or without using TMAOH template were systematically studied.Results indicate that, pure zeolite T with high crystallinity was synthesized in both systems.K⁺ plays a strong structure-directing role in the formation of zeolite T in the system withoutany organic template, while TMA⁺ replace K⁺ as main template in the system that addingTMAOH. Zeolite T with larger surface area, pore volume and higher Si/Al ratio was obtainedfrom the system that containing TMAOH. The pore structure and composition of zeolite Twas affected obviously by TMAOH.Effects of silica source, crystallization temperature, agitation and n(SiO₂)/n(Al₂O₃) ratioof gel on the synthesis of zeolite T were investigated in the system that free of organictemplate. Results show that pure zeolite T was synthesized as the crystallization temperaturewas in the range of 85～135℃. The agitated crystallization effectively, decreased the crystalsize of zeolite T, however, the difference was little as the stirring speed changed in the rangeof 200～800 r/min. Pure zeolite T with high crystallinity could be synthesized from the gelswith n(SiO₂)/n(Al₂O₃) ratio=16～32. The further increase of the n(SiO₂)/n(Al₂O₃) ratioresulted phillipsite impurity. The change of n(SiO₂)/n(Al₂O₃) ratio of gel had no influence onthe n(SiO₂)/n(Al₂O₃) ratio of zeolite T. In addition, it was observed that the induction periodof the crystallization was shortened by using water glass as silica source.Zeolite T synthesized in this paper shows good thermal stability, hydrothermal stability.It has the similar acidity with HZSM-5. Carbon-zeolite T composited membrane prepared byusing the herein synthesized T zeolite has good separation performance toward CO₂/CH₄mixtures, which indicates favorable application foreground.