Octahedral MnO₂ Molecular Sieve-Decorated Meso-ZSM-5 Catalyst for Eco-Friendly Synthesis of Pyrazoles and Carbamates

Abstract

Octahedral MnO2 molecular sieve (hereafter designated as OMS) was prepared in the presence of urea, and mesoporous ZSM-5 (designated as Meso-ZSM-5) was prepared using propyltriethoxysilane as additive under hydrothermal synthesis condition. OMS-decorated Meso-ZSM-5 was prepared by heating a grounded mixture of OMS and Meso-ZSM-5. Powder X-ray diffraction, N2-sorption, SEM, TEM, thermogravimetric analysis, FT-IR, diffuse reflectance UV–vis spectroscopy, and NH3 and CO2 temperature-programmed desorption techniques were used to characterize the material. The catalyst was demonstrated in a one-pot, one-step synthesis of pyrazoles via cyclization followed by dehydrogenation as the key reaction steps. Synthesis of carbamates by the reaction of cyclic and acyclic carbonates/di-tert-butyl dicarbonate with amines was another important application of this catalyst. Catalyst exhibited efficient recyclability. No leaching of active species took place even after five recycles. A strong interface between OMS and Meso-ZSM-5 imparts strong acidity and distinguished activity in the synthesis of pyrazole heterocycles and organic carbamates.

Preparation, Structure‐Performance Relationship, and Reaction Network of ZnZSM‐5 for Oxidative Dehydrogenation of Ethane with CO2

“…450, 550, 800, 1100 and 1230 cm −1 . These can be attributed to the bending vibrations of T−O−T bonds (T=Si or Al), vibration of MFI pentasil units, symmetric stretching vibrations of Si−O−Si, asymmetric stretching vibrations of Si−O−Si, and stretching vibrations T−O, respectively [22–24] . Therefore, the HZSM‐5 skeleton remained integrate after the introduction of Zn.…”

“…These can be attributed to the bending vibrations of TÀ OÀ T bonds (T=Si or Al), vibration of MFI pentasil units, symmetric stretching vibrations of SiÀ OÀ Si, asymmetric stretching vibrations of SiÀ OÀ Si, and stretching vibrations TÀ O, respectively. [22][23][24] Therefore, the HZSM-5 skeleton remained integrate after the introduction of Zn. However, detailed inspection suggests that with the gradual increase of Zn loading, the intensity of the absorption peak at 550 cm À 1 was slightly weakened, and the intensity ratio of the bands at 550 and 450 cm À 1 (I 550 /I 450 ) increased from 0.70 to 1.01 (Figure S5).…”