LAUSR

Abstract This study provides an in-situ seeding method to prepare ZSM-11(5) aggregates with both good porosity and catalytic performance in methanol conversion reaction. Compared with the conventional two-stage varying-temperature synthesis method, this method, which involves the preheating Al-free gel to generate pentasil silicate seed before the addition of Al source, dramatically accelerates the crystallization rate at high temperature (170 °C). The Al species can be well incorporated into the framework as confirmed by both FT-IR and 27 Al MAS NMR analysis. The results suggest that the existence of Al species plays a crucial role in inducing the formation of nanorods stacking morphology. The SEM images indicate that the samples prepared by the method combined the in-situ feeding with recrystallization process possess an evidently smaller crystal size due to the fast nucleation rate in the initial Al-free gel at low temperature (90 °C). Both Sam-Al-1 and Sam-Al-2 exhibit better catalytic performance in the methanol conversion than Sam-Al, which can be attribute to the higher concentration of Al at the crystal surface benefited by this in-situ feeding procedure. Particularly, the sample Sam-Al-2 obtained by recrystallizing the Al + Sam-Si mixture exhibits a loose-oriented stacking morphology by nanorods, which is thought to be beneficial to the accessibility of reactants to the active sites and the fast leaving of products and consequently contributes to its improved catalytic performance.