The application of Ni and Zr modified ZSM-5 nanosheet in upgrading of lignite pyrolysis volatiles coupling with methanol to light aromatics

Ni and Zr modified nanosheet ZSM-5 zeolites as tandem catalysts were designed using co-impregnation method (Zr-Ni/S-Z5) or combining in-situ hydrothermal synthesis of Ni@S-Z5 and sequential impregnation of Zr (Zr/Ni@ S-Z5). Their applications in upgrading of lignite pyrolysis volatiles coupling with methanol to light aromatics were investigated. The results demonstrated that nanosheet zeolites with larger surface areas and shorter b-axis length benefited the production of light aromatics due to exposing more active sites and improved diffusion limitation compared with conventional ZSM-5 zeolites. Adding Ni and Zr into tandem catalysts further enhanced BTEXN yields, which was attributed to the induction of oxyphilic ZrO2 for activating CAr-O bonds combining the promotion of Ni for hydrogenation. Comparing to Zr-Ni/S-Z5 catalyst, lower BTEXN yield was observed due to the decrease in exposing active sites over Zr/Ni@ S-Z5 catalyst. Moreover, enhancing diffusion behaviors in shorter b-axis length and the presence of more fractions of external coke indicated less effective in blocking pore channels, thus nanosheet zeolite series showed lower deactivation rates.