Influence of synthesis and operating parameters on silicalite-1 membrane properties

The present study deals with the synthesis of nanostructured silicalite-1 membranes on porous α-Al2O3 supports by a hydrothermal method. Different parameters including the synthesis conditions (temperature and alkalinity) and operating conditions (temperature and pressure) were investigated. The membranes were characterized by X-ray diffraction and scanning electron microscopy techniques. The optimum synthesis temperature and alkalinity were determined to be 160 °C and pH = 11, respectively. The permeability of CO2 and CH4 through the optimized membrane was determined by the pressure drop method. The results revealed that the main effective separation mechanism was adsorption. The permeation of CO2 and CH4 declined with increasing temperature, whereas high feed pressures enhanced the single gas flux. The CO2 and CH4 permeability values at 30 °C and 2 bar were 1.62 × 10−7 and 2.07 × 10−7 mol m−2 s−1 Pa−1, respectively. Furthermore, the response surface methodology analysis confirmed the significance of all the variables and the proposed model. Excellent correlation between the experimental and predicted data (R2 = 0.99) was obtained, confirming that response surface methodology is a powerful tool for modeling nanostructured silicalite-1 membrane processes.