Tandem catalysts for the conversion of methanol to aromatics with excellent selectivity and stability

Abstract

The highly stable and selective conversion of methanol to aromatics is an attractive but challenging target. Herein, a feasible methanol aromatization reaction pathway was proposed over a tandem catalyst, through which methanol to olefins and olefin aromatization reactions were efficiently coupled. The properties of the catalysts used were characterized by transmission electron microscopy (TEM), N₂ adsorption–desorption isotherm, NH₃ temperature programmed desorption (NH₃-TPD), and pyridine adsorption (Py-IR), and the results indicated that the physicochemical properties of the upper bed HZSM-5 catalyst display an important influence on the product distribution and active life of the tandem catalyst. Compared with the single-bed low-silicon HZSM-5 catalyst, the introduction of a high silicon HZSM-5 zeolite not only greatly improves the selectivity of light aromatics, but also increases the active life of the catalyst by about four times. Moreover, by introducing a synthetic high silica zeolite with a nano–mesoporous structure, the active life of tandem catalysts is doubled again. In addition, it is also inferred that oxygenic coke may be the main reason for the rapid deactivation of the catalyst in the reaction.