Structural, morphological and catalytic investigations on hierarchical ZSM-5 zeolite hexagonal cubes by surfactant assisted hydrothermal method

• ZSM-5 zeolite hexagonal cubes have been synthesized by using nonionic surfactant.
• Surfactant controls the particle size and morphology without agglomeration.
• ZSM-5 shows excellent catalytic activities in the oxidation of benzyl alcohol.
• The catalyst can be reused without a significant loss in the conversion.

Nanosized ZSM-5 zeolite hexagonal cubic micro-blocks with different Si/Al ratios were successfully synthesized by using TPAOH in the presence of nonionic surfactant (Triton X-100) by a hydrothermal method. The samples prepared with the surfactant were characterized by XRD, XRF, FT-IR, N2 adsorption, HR-TEM, HR-SEM and NH3-TPD analysis to evaluate the particle structure, size and acid strength. Pure crystalline phase of ZSM-5 is confirmed by powder X-ray diffraction. FT-IR analysis further showed that nanosized zeolite has double five rings of the MFI-type of typical absorption at about 550 cm- 1. The SEM images clearly show that all ZSM-5 zeolite samples possess the similar hexagonal spheres morphology with particle size of about 320–360 nm. The influence of Triton X-100 in the structural, textural, morphological and catalytic properties of ZSM-5 is compared with conventional ZSM-5. The catalytic activity of ZSM-5 zeolites with different Si/Al ratios (ZSM-5-WS(x) and ZSM-5-WOS(x)) is evaluated in the selective oxidation of benzyl alcohol (BzOH) using tert-butyl hydroperoxide (TBHP) as an oxidant and water as a solvent. The Triton X-100-assisted preparation yielded a zeolite exhibiting a higher conversion than the one prepared in the absence of Triton X-100. Among the catalysts, ZSM-5-WS(28) (Si/Al = 28) catalyst exhibited significantly higher conversion at optimum conditions. This catalyst can be retrieved and reprocessed for five times without a significant loss in its activity and selectivity.

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