Catalytic Cracking of n-Hexane in the Presence of Zeolite ZSM-5 Micro- and Nanocrystals

Resumo

Results of a study on the synthesis of two sets of zeolites of the MFI structural type with a crystal size of a few microns (1–5 μm) in the first set and 120–140 nm in the second set and different Si/Al molar ratios of 20–220 in each of the sets have been described. The crystal sizes have been determined by dynamic light scattering and electron microscopy; the phase, textural, and acid properties of the samples have been studied by XRD, nitrogen sorption by the BET method, and ammonia TPD, respectively. The synthesized samples have been tested in the model n-hexane catalytic cracking reaction; the catalytic properties of the samples with respect to n-hexane conversion and the protolytic cracking, dehydrogenation, and hydride transfer reactions have been compared. It has been shown that a key role in the catalyst activity is played by the combination of the strong acid site concentration and the pore hierarchy factor (HF); the maximum conversion is observed at a strong acid site concentration of 0.2 mmol/g and HF = 0.26.