Abstract
ABSTRACTIn this study ZSM-5 Nano particles with high crystallinity were synthesized using a dry gel conversion technique. An L9 orthogonal array of the Taguchi method was applied to investigate the effect of synthesis parameters, such as crystallization time, gel drying temperature, molar composition of template (TPAOH) and water content in the crystallization stage on crystallinity and particle size of the ZSM-5 catalyst. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Beside short crystallization time, the particle sizes were considerably smaller in comparison with those prepared using the hydrothermal method. The results showed that the particle size and crystallinity increased with increasing water content and crystallization time. The effects of gel drying temperature and molar composition of template were found to be more complex, however. Comparing to hydrothermal method, ZSM-5 samples synthesized with the dry gel conversion exhibited higher selectivity to gasoline than other hydrocarbons.
Highlights
Gasoline, an important derivative of oil, is widely used as a transportation fuel in all over the world [1]
The crystallinity of samples were calculated with the aid of PANalytical X'Pert software based on the Rietveld method and it was observed that it dry gel conversion technique (DGC)-ZSM-5 is more crystalline compare to HT-ZSM-5 (100% compare to 79% relative crystallinity)
In this study, nanosized-ZSM-5 catalysts were successfully synthesized by dry gel conversion technique using an L9 orthogonal array of the Taguchi method
Summary
Three approaches have been reported for the synthesis of nano-sized ZSM-5 which are hydrothermal, confined-space and two-step seeded growth synthesis [8,9,10,11]. The dry gel conversion technique (DGC), as a new synthesis route has been applied to the synthesis of nanosized-ZSM-5 zeolites [12]. In this regard, Tao et al [13] prepared ZSM-5 zeolites of uniform and small particles with a size of 100– 200 nm. The major advantages of the DGC method over conventional hydrothermal routes are as follow [14]: Higher zeolite yield Less waste generation and less reactor volume requirement Rapid crystallization Reduction of the consumptions of expensive templates No need for wastewater treatment Possible continuous production process Cost effective and eco-friendly route. The catalytic performance of the nominated ZSM-5 sample in the MTG process is studied to investigate its reactivity
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