Synthesis of 10 and 12 Ring Zeolites (MCM-22, TNU-9 and MCM-68) Modified with Zn and Its Potential Application in the Reaction of Methanol to Light Aromatics and Olefins

Abstract

The effect on the incorporation of zinc of three zeolites TNU-9, MCM-22, and MCM-68 was investigated. The physico-chemical properties of zeolites were studied by X‐ray diffraction, N2-adsorption, temperature‐programmed desorption of NH3 (TPD), nuclear magnetic resonance of 27Al and 29Si (MAS NMR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Then all the samples were characterized and evaluated in the reaction of methanol to aromatics (MTA). The correlation of zinc incorporation method and acidic properties of zeolites with catalytic performance was investigated. The form of zinc incorporation, the acidity, the type of zeolitic structure and the reaction temperature had a great influence on the catalytic activity. Regarding the type of structure, the total aromatics selectivity in this work increased in the followed order for zeolites modified with Zn: MCM-68 > TNU-15 > MCM-22. The medium pore zeolite T9-15 (TNU-9 zeolite and Si/Al 15 ratio) catalysts with the ratio ZnO/ZnO + Al2O3 equal to 0.34 (T9-15 0.5 Zn) showed better stability with conversion of methanol completes during 9 h of reaction and 17% to BTX selectivity and 32% to total aromatics compounds at 450 °C and WHSV of 4.24 h−1. In methanol conversion, the selectivity to aromatics over the T9-15 modified-Zn materials (TNU-9 zeolite and Si/Al 15 ratio) under study, increased in the followed order: T9-15 0.5 Zn > ZT9-15 > T9-15 > T9-15 0.2 Zn. The reaction temperature is an important variable in the MTA process. At 450 °C a better activation of acid sites is achieved in zeolite with Zn and therefore a high percentage of BTX selectivity is obtained for TNU-9 zeolite.