Template-free Synthesis Of Zeolites And Zeolite Membranes

BEA and MFI-type zeolites have reached industrial use. Organic templatesdominate the synthesis of zeolites and zeolite membranes with some disadvantages,such as high cost, the defects caused by the removal of templates, high energyconsumption and environmental pollution. The organic template-free method avertsthe use of expensive organic templates and the formation of defects in the followingtemplate-removal step, which is more easily to gain commercial applicationsworldwide.In this dissertation, the zeolite beta prepared by laboratory was used as seeds toinduce the synthesis of zeolite beta-OTF (beta-organic template free) in the organictemplate-free suspension under the traditional hydrothermal conditions. Themicrowave-assisted, template-free and seed-directed synthesis of zeolite beta-OTFwas developed for the first time, which showed good truncated octahedralmorphology, and more uniform size. The crystallization time was only3h. Thetemplate-free method reduced the cost and environmental pollution significantly.We firstly reported an organic template-free synthesis strategy to prepare apreferentially (h0l)-oriented beta zeolite membrane on the porous α-Al2O3supportsurface by secondary growth method. Under appropriate molar ratios of the precursorsuspension and hydrothermal conditions, the calcination of the seed layer and theplacement of the support influenced the synthesis of beta zeolite membranes greatlywithout organic templates. Most importantly of all, the beta seed layer isindispensable for the template-free route. The most selective membrane exhibited aseparation factor ethanol/TIPB of321for a mixture containing10wt%TIPB dilutedin ethanol. It suggested that beta-OTF zeolite membranes are better than the onessynthesized by template-method. It is noteworthy that the template-free route couldavoid the consumption of organic templates, the formation of calcination defects andthe pollution to the environment, which would be very helpful for green and cheapsynthesis of beta zeolite membranes, as well as more possible to realize widecommercial applications.The MFI-type zeolite membranes were prepared on porous α-Al2O3substratesusing the template-free secondary growth method using three different sizes of silicalite-1seeds. The obtained zeolite membranes were tested by CO2/N2binary gasseparation and ethanol/water pervaporation with a certain separation effect.