Shaped binderless ZSM-11 zeolite catalyst prepared via a dry-gel conversion method:Characterization and application for alkylation of benzene with dimethyl ether

摘要

Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30 SiO_2mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best structure directing agent for the synthesis of the binderless ZSM-11 catalyst, without adding other alkaline materials. The 70HZSM-11/30 SiO_2mix serials materials crystallized for different times were detected by X-ray diffraction(XRD), nuclear magnetic resonance(NMR), scanning electron microscopy(SEM), transmission electron microscopy(TEM), scanning transmission electron microscopy–energy dispersive spectroscopy(STEM–EDS) techniques, and so on. In order to investigate the possible crystallization mechanism, the textural and structural properties of 70HZSM-11/30 SiO_2mix serials samples were further characterized by N_2 adsorption–desorption. Acid properties were determined by temperature-programed desorption of NH_3(NH_3-TPD) and pyridine adsorption-infrared(Py-IR) measurements. In the alkylation of benzene with dimethyl ether, the serials catalysts exhibited different benzene conversions. 70HZSM-11/30 SiO_2mix showed the lowest benzene conversion while sample 70HZSM-11/30 SiO_2mix-6.5h synthesized only for 6.5h displayed a higher benzene conversion, even higher than the value over 70HZSM-11/30Al_2O_3mix. Extending the crystallization time, the obtained samples displayed the increased benzene conversion in general under the same reaction conditions. In the end, the relation of physicochemical properties with the reaction performance was investigated.