Sythesis of zeolite beta for composite membranes

Gür, Nadiye
In this work, zeolite Beta was synthesized experimentally in order to be used as filler in fuel cell membranes in order to assess the proton conductivity of composite membranes. Effects of the Si/Al ratio, and synthesis time on yield, relative crystallinity, crystal size, and proton conductivity were investigated. Zeolite Beta with Si/Al ratio between 10 and 30 was synthesized with a batch formulation of 2.2Na2O:1Al2O3:ySiO2:4.6(TEA)2O:tH2O (where TEA≡ tetraethylammonium) at 150°C for 5-15 days of synthesis time. Sodium aluminate, tetraethylammonium hydroxide (TEAOH) solution, sodium hydroxide pellets (NaOH), and deionized water were used for the preparation of the batch solution. Zeolite Na-Beta was calcined and treated with sulfuric acid solution at different concentrations in order to have zeolite H-Beta. Polyetherether ketone (PEEK) was sulfonated in order to have a proton conductive membrane and than zeolite H-Beta was incorporated resulting in a composite or nanocomposite membrane. X-ray diffraction (XRD) analysis helped to understand whether the synthesized material was zeolite Beta or not. The morphology and the crystal size of the crystals were observed as a result of the scanning electron microscopy (SEM) analysis. In order to see the effect of sulfuric acid treatment on the sodium (Na) content of the zeolite Beta, inductively coupled plasma (ICP) analysis was performed. Synthesis results indicate that as Si/Al ratio and synthesis time increased the yield of zeolite Beta increased. It was observed that Si/Al ratio from 10 to 30, and synthesis time between 5 to 15 days did not affect the crystal size significantly. For the sulfonation of PEEK, sulfuric acid was used. Sulfonated polyetherether ketone (SPEEK) was dissolved in a solvent that was dimethyl acetamide (DMAC), incorporated with zeolite Beta, and then solvent was removed in the vacuum oven. The proton conductivity was measured with a 2-probe impedance spectrometer. Initial results indicate that zeolite Beta at 10 and 20 wt % loadings did not affect the proton conductivity of the SPEEK membrane at 100 % relative humidity and room temperature.


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Citation Formats
N. Gür, “Sythesis of zeolite beta for composite membranes,” M.S. - Master of Science, Middle East Technical University, 2006.