Synthesis of least defect NaY membranes: Defining optimum heating and cooling rate of hydrothermal treatment (HT) and application of zeta potential measurement via different seeding methods

Abstract

Zeolite membrane is one type of microporous inorganic membrane which has gained so much interests among researchers as an alternative especially for gas separation. Among major challenges to produce high quality zeolite membranes with less defects are to have a good seeding and hydrothermal treatment (HT) method. On this matter, a study on the colloidal stability of the zeolite NaY seeds in the seeds solution in order to obtain homogenous seeds layer on top of the alumina support via several seeding methods and pHs of the seeds solutions were investigated. Then, the seeded samples were taken into HT process in order to form zeolite NaY membranes. During this stage, heating and cooling rates ( o C/hr) were varied in order to study their effects towards formation of zeolite membrane with least defects. Characterizations were performed by using X-Ray Diffraction (XRD) in order to identify degree of crystallization and amount of impurities while Scanning Electron Microscopy (SEM) was used in order to study surface morphology of the samples. From this study, it was found that densification effect from different seeding methods played important factor in forming zeolite membranes with least defects. Accordingly, suitable heating and cooling rates were required in order to optimize the growths of zeolite NaY seeds to form zeolite layer on top of the alumina support. In this case, due to thermal mismatch between the substrate and zeolite material, it could form some cracks on top of the alumina support. Thus, by implementing optimum heating/cooling rate, a zeolite NaY membrane with least amount of defects i.e. cracks and pinholes could be achieved with less degree of impurities i.e. zeolite NaP during HT process.