Hierarchical nano-ZSM-5 zeolites (Z5-X) with different grain sizes were synthesized by varying amounts of 3-glycidoxypropyltrimethoxysilane (KH-560) in the hydrothermal synthesis strategy. Moreover, the conventional ZSM-5zeolite(Z5), which was prepared without KH-560, was used as the reference sample. The crystalline phases, morphologies, porous characteristics, Si/Al molar ratios and acidic properties of all fresh catalysts were characterized using the X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), N₂ adsorption–desorption, inductively coupled plasma atomic emission spectroscopy (ICP) and temperature programmed desorption of ammonia (NH₃-TPD) techniques. Results show that the grain size and strong acid amount of zeolite decreased with the increasing amount of KH-560. The micropore surface areas and the corresponding volume of Z5-X changed less compared with Z5. Consequently, the high shape-selectivity of zeolite was preserved well under the addition of KH-560. However, the mesopore surface areas and the corresponding volume increased significantly with the increasing amount of KH-560. Benefiting from the abundant hierarchical structure, the Z5-X catalysts exhibited a larger coke capacity than the Z5 catalyst. The coke depositions of all the deactivated catalysts were characterized by the thermogravimetric technique (TG), and the results are indicative of the decreased average rate of coke deposition with an increasing amount of KH-560, which could result from the gradually reduced strong acid amount and the nano-sized crystallites. The catalytic performance of methanol-to-aromatics (MTA) indicates that the Z5-0.12 catalyst exhibited higher catalytic activity and selectivity of BTX as the reaction was prolonged, which could result from the synergistic effect among the proper strong acid amount, the smaller zeolite grain size, and the abundant hierarchical structure.

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.