Synthesis of multiple-template zeolites with various compositions and investigation of their catalytic properties

Hierarchical zeolite catalysts with a combination of microporous and mesoporous properties have a significant effect on improving catalytic processes. We herein report the synthesis of hierarchical ZSM-5 catalysts using the hydrothermal method with various combinations of multiple templates, including TPABr, CTAB, and F127. By applying response surface methodology for design and optimization of template composition in methanol-to-propylene process, we obtained a quadratic model with statistically significant accuracy. Using this model, we could also predict the propylene selectivity of the synthesized zeolites by altering the template composition. Further characterization of the synthesized zeolites by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, NH 3 -TPD, and N 2 physisorption analysis confirmed that the template composition is a critical parameter with huge effect on crystal structure and morphology, strong and weak acid sites, surface area, and volume of mesopores. Different compositions affected orientation of zeolite crystals and diffraction peaks in the XRD patterns. The simultaneous presence of both mesoporogens in the catalyst structure was necessary to achieve the highest efficiency. Comparing experimental data and modeling results, we found that the combination of templates near the central point had a better performance in MTP process. The highest selectivity to propylene (58.8) was obtained from the optimal catalyst and the highest stability was acquired from the catalyst with central point composition. Improved catalytic performance can be attributed to the hierarchical structure, high mesopore volume, and appropriate acidity. Graphic Abstract