One-pot synthesis of sheet-like MFI as high-performance catalyst for toluene disproportionation

In this study, one-pot hydrothermal synthesis of sheet-like ZSM-5 as a high-performance catalyst for toluene disproportionation was carried out using binary surfactants. In the dual template, tetraethylammonium hydroxide was used to construct the microporous structure of ZSM-5, and cationic surfactant (e.g., octadecyltrimethylammonium chloride (C₁₈TMAC), hexadecyltrimethyl ammonium bromide (C₁₆TMAB), and tetradecyltrimethylammonium bromide, (C₁₄TMAB)) can change the growth habits of the ZSM-5 crystals by hindering the regular stacking of zeolite layers from their longer hydrophobic chain. From the XRD pattern of the as-synthesized samples which were hydrothermally treated for different time, it was found that a lamellar mesostructured intermediate gradually transformed into the sheet-like ZSM-5 during hydrothermal process. With a proper amount of cationic surfactant, the thickness of the sheet-like ZSM-5 could be controlled to less than 30 nm. Concerning the catalyst application, the toluene disproportionation performance over the sheet-like ZSM-5 is 1.5 times higher than that of the commercial ZSM-5. The higher conversion is ascribed to the faster diffusion amount due to the sheet-like ZSM-5.