Crystallization and porosity of ZSM-23

The synthesis conditions for zeolite ZSM-23 with Si/Al ratios of 50 and 100 were studied with the two different neutral amines pyrrolidine and isopropylamine acting as structure-directing agents (SDA). Special attention was directed towards the development of crystal growth, the occurrence of impurity phases, and the resulting physical properties such as porosity. This was accomplished through comprehensive characterization with methods such as XRD, SEM, HRTEM, electron-diffraction and Raman spectroscopy, as well as nitrogen sorption. We demonstrate that highly crystalline ZSM-23 phases consist of micron-sized bundled needles with very high aspect ratios. The zeolite architecture results in one-dimensional channels running parallel to the growth direction of the needles. This specific pore structure and morphology, combined with possible competitive growth of denser phases can strongly impact the adsorption capacity of this unique pore structure.

The impact of synthesis conditions and small amine structure-directing agents on the phase purity, morphology and sorption characteristics of ZSM-23 are reported.Figure optionsDownload as PowerPoint slideResearch highlights
► Zeolite ZSM-23 with Si/Al ratios of 50 and 100 was synthesized with pyrrolidine and isopropylamine as structure-directing agents (SDA).
► Highly crystalline ZSM-23 phases consist of micron-sized bundled needles with very high aspect ratios.
► The one-dimensional channels run parallel to the growth direction of the needles.
► The specific pore structure and morphology and possible impurity phases can strongly impact the adsorption capacity.