Catalytic Cracking of n-Dodecane to Chemicals: Effect of Variable-Morphological ZSM-5 Zeolites Synthesized Using Various Silica Sources

This study emphasizes tuning the synthesis conditions of MFI zeolites to achieve better catalytic properties by optimizing the mesoporosity, the balance between Bronsted and Lewis sites, and the zeolite particle sizes. The MFI zeolites were hydrothermally synthesized at various temperatures employing different silica sources. The synthesis temperature was varied between 110 to 180 degrees C at constant synthesis time (15 h). Different silicon sources led to variations in structure, morphology, and size of the MFI zeolite along with tuned Lewis and Bronsted acid sites in parallel correlation with shape selectivity of the reaction. The catalytic activities of synthesized zeolites were investigated in the catalytic cracking of n-dodecane to produce value-added chemicals. The zeolite synthesized at 180 degrees C using fumed silica presented the highest catalytic conversion (96.6%), while maximum light olefin gaseous products (73.1%) were obtained for the sample synthesized at 140 degrees C using tetraethyl orthosilicate as the silica source. The MFI zeolite synthesized at 180 degrees C employing tetraethyl orthosilicate as a silica source facilitated the formation of both naphthenes and aromatics (71.3%) as major liquid products.

Automated summary

This study focuses on tuning the synthesis conditions of MFI zeolites to improve catalytic properties by optimizing mesoporosity, the balance between Bronsted and Lewis sites, and zeolite particle sizes. Different silicon sources and synthesis temperatures have significant effects on the structure and functionality of MFI zeolites, which in turn impact the shape selectivity of catalytic cracking reactions.