Study On Preparation Of MFI Membrane And Its Characteristics Of Catalytic Pyrolysis

Supported silicalite-1 and ZSM-5 membranes were synthesized on nonporous stainless steel plates by the in situ hydrothermal crystallization method in this paper. The influence of the thermal treatment temperature, the crystallization time and the synthesis solution compositions on the synthesis of MFI membranes was investigated. The effects of these synthesis parameters were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared sepectrometry (FT-IR) studies. The optimized thermal treatment temperature and crystallization time for MFI zeolite membrane synthesis were 165℃~185℃ and 24 hours respectively. The optimized reaction solution composition was 1TPAOH:6TEOS:571H2O for silicalite-1 membrane preparation, while 1TPAOH:6TEOS:571H2O:(0.005~0.02)Al2-O3 for ZSM-5 membrane preparation.With the observation results of SEM, the crystal growth model—a successive accumulation model of zeolite crystals was indicated for silicalite-1 film. Zeolite Silicalite-1 crystallization on the stainless steel substrate was subjected to a detailed kinetic analysis and it was been shown that both the nucleation rate and the crystallization rate increased as the temperature increasing. The apparent activation energy for nucleation and crystal growth were 33.13 kJ/mol and 17.37 kJ/mol, respectively.Finally, the continuous ZSM-5 crystal films were formed on tubular stainless steel substrates (φ3×5mm) using a synthesis mixture of 6TEOS:1TPAOH:571H2O:-0.01Al2O3 at 175℃. Under well-defined conditions, the membrane catalyst coated with ZSM-5 membrane was used to evaluate the effects of catalytic pyrolysis n-decane. The ZSM-5 film catalysts showed high activity for the pyrolysis reaction of n-decane and suppressed the coking in the reactor. The reaction conversion of n-decane catalytic pyrolysis was up to 50.42% at 650℃ under atmospheric pressure.