Synthesis of Quinolines by the Skraup Reaction: Hierarchical Zeolites vs Microporous Zeolites

The activity, selectivity, and stability of microporous highly dispersed zeolites (H‐Y, H‐ZSM‐5) and granulated hierarchical zeolites (H‐Y_h and H‐ZSM‐5_h) were studied in the synthesis of quinolines by the Skraup reaction. Texture, porous structure, morphology of crystals, acidic properties were characterized by XRD, XRF, N₂ adsorption‐desorption, SEM, NH₃‐TPD methods. It was found that quinoline, 2‐ and 4‐methylquinolines are the main products in the reaction of aniline with glycerol in the presence of the studied catalysts. H‐ZSM‐5_h and H‐Y_h catalysts are more efficient than catalysts H‐ZSM‐5 and HY and provide a yield of quinolines to 72.4 (H‐ZSM‐5_h) and 60.2 % (H‐Y_h) at 450 °C, 0.2 h⁻¹, the molar ratio of aniline:glycerol=1 : 3. The high activity and selectivity of hierarchical zeolites are due to the presence of meso‐ and macropores, as well as nanocrystals of 15–100 nm size. It was reported that hierarchical catalysts exhibit higher stability in the reaction compared with microporous zeolites.