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A new type of host–guest composite catalyst, ZSM-5/Beta, with a hierarchical pore system were synthesized by incorporating Beta zeolite into the structure of ZSM-5 zeolite. The crystalline, structural, textural and acid properties of the composite zeolites, as well as the parent ZSM-5, were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), nitrogen adsorption/desorption analyses (BET) and temperature programmed desorption of ammonia (NH3-TPD) techniques. The solid product was employed as a catalyst for methanol to gasoline reaction. Results showed that the binary structure of these catalysts, not only integrates the pore characteristics of ZSM-5 and Beta zeolites but also changes the acid properties and creating new active sites that lead to higher activity. The highest activity, gasoline yield and longer lifetime were obtained over a sample with 30 wt% Beta zeolite due to improved textural and acid properties. Over the optimized sample, selectivity to alkylated aromatics as an octane number boosters increased about 15%, gasoline yield increased by an average of 9% and 65% increase in catalyst lifetime compared to reference ZSM-5 was obtained. In addition, the decline in unfavorable durene selectivity compared to the pristine ZSM-5, from 0.98% to 0.85%, verifies the improvement in gasoline quality. |
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