Seed-assisted OSDA-free synthesis of ZSM-5 zeolite and its application in dehydrogenation of propane

• Seed-assisted OSDA free synthesis method using TPABr-silicalite-1 is proposed.
• Efficient and cost-effective strategy for the high-yield production of ZSM-5.
• High activity level of about 31% propane conversion after 7 h of reaction.
• Reliable stable selectivity toward light olefins.
• Prominent selectivity toward propylene and high stability parameter.

ZSM-5 is one of the most well-known members of zeolite family owing to its huge number of industrial applications due to its instinct acidity and well-defined micropore structure. It can be synthesized in a one or multi-step hydrothermal procedure employing versatile synthesis parameters. Here, seed-assisted OSDA (organic structure directing agent)-free synthesis method based on using TPABr-silicalite-1 as structure directing agent is proposed as an economical route considering reproducibility and short synthesis time benefits as well. This two-step synthesis technique exploits an enriched aluminum template-free precursor gel containing zeolite nuclei that attach and grow around high siliceous zeolite cores named as silicalite-1. The prepared ZSM-5 product was characterized using XRD, SEM, FT-IR, EDX, elemental mapping, ICP and N2 adsorption–desorption techniques. Results confirmed the fully crystalline pure MFI structure of the obtained product. The catalytic behavior of the fabricated material as support was evaluated in the propane dehydrogenation reaction (PDH). The PtSn-based ZSM-5 catalyst maintained its activity to a certain level of about 31% propane conversion after 7 h time on stream with more than 89% total olefins selectivity. It seems that seeding along with using a cheap template like TPABr in the synthesis of seeds is an efficient method which has the potential to be emerged as a promising method for the ZSM-5 large-scale production.

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