A high-efficiency and low-cost solid-state synthesis strategy for fabricating (Mg)AlPO-11 zeotypes with excellent n-hexadecane hydroisomerization performance

Facile and efficient preparation of zeolitic materials with enhanced performance is highly desired due to their wide industrial applications in catalytic reactions. Herein, we demonstrate a rational and low-cost solid-state strategy to synthesize AEL-type zeotypes, i.e., AlPO4-11 and MgAlPO-11 (S-MgAlPO-11), by directly calcining amorphous precursors in open vessels at 300oC for 30min. The precursors were prepared via a conventional metal alkoxide mediated sol-gel method using ammonium dihydrogen phosphate (NH4H2PO4) and 1-ethyl-3-methylimidazolium bromide ([EMIm]Br) ionic liquid as the phosphorous source and organic template, respectively. The influence of synthesis parameters and distinct crystallization mechanisms are studied comprehensively using multiple characterization techniques, including XRD, SEM, FTIR, Raman, and Ar adsorption-desorption. Furthermore, hierarchically porous MgAlPO-11 (H-MgAlPO-11) can also be fabricated by adding an organosilane in the amorphous precursor. In hydroisomerization of n-hexadecane, the bifunctional Pt/S-MgAlPO-11 catalyst exhibits superior catalytic performance with a maximum isomer yield of 87.7%. This value can be further increased to 88.7% for the Pt/H-MgAlPO-11 catalyst, attributing to the improved diffusion properties to suppress side cracking reactions.