Synthesis, characterization and hydroisomerization activity of ZSM-22/23 intergrowth zeolite

ZSM-22/23 intergrowth zeolite was synthesized by hydrothermal method using N,N-dimethylformamide (DMF) and 1, 6-diaminohexane (DAH) as structure directing agents (SDAs). Interestingly, addition of ZSM-22 directing SDA in the range of 2.5–7.5 mol% in the gel of ZSM-23 has been found to have dominant templating effect and favored formation of intergrowth (ZSM-22/23) structure and is found to influence crystallization of intergrowth phase with 60% ZSM-22 (TON) character. The physicochemical properties of ZSM-22/23 intergrowth phase were characterized by X-ray diffraction (XRD), N2-physisorption, Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), NH3-Temperature Programmed Desorption (NH3-TPD), and Nuclear Magnetic Resonance Spectroscopy (CPMAS NMR), respectively. The characterization result suggests the formation of intergrowth zeolite having needle shaped morphology and Si/Al ratio in the range of 60–120 with moderate acidity in the range of 50–120 μmol/g, and desired textural properties (surface area ∼200 m2/g and pore volume ∼ 0.15 cc/g). The performance of intergrowth for hydroisomerization of n-hexadecane was evaluated by preparing catalysts in extrudate form by supporting ∼0.32% Platinum (Pt) on catalyst body containing zeolite and alumina (50:50 wt%). The platinum content in Pt-ZSM-22/23 was determined by Inductively Coupled Plasma (ICP), The catalyst based on intergrowth phase bulk Si/Al ratio of 60 showed maximum isomer selectivity of 89% with ∼80% yield at 90% conversion was observed at 303 °C.