Effect of copper on textural and acidic properties of hierarchical nanocrystalline ZSM‐5

摘要

Abstract In this work, hierarchically porous nanocrystalline ZSM‐5 was synthesized hydrothermally. Different concentrations of copper were incorporated into the matrix by ion exchange method. The synthesized samples were characterized by means of X‐ray diffraction (XRD), Fourier‐transform infrared (FTIR), energy‐dispersive X‐ray spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy (XPS), ultraviolet (UV), 27Al magic angle spinning nuclear magnetic resonance spectroscopy, and nitrogen sorption analysis. The acid sites on the surface of Cu‐ZSM‐5 have been systematically investigated using temperature‐programmed desorption of ammonia (NH3‐TPD) and pyridine sorption followed by FTIR. The diffraction pattern obtained from XRD studies confirmed the typical Mobil Five. NH3‐TPD reveals the enhancement of acidity achieved by copper. The FTIR spectra of pyridine desorbed samples show that the intensity of bands corresponding to Lewis acidity increases by modification. The ZSM‐5 zeolite samples exhibit spherical‐shaped MFI crystal structure. The UV spectrum indicates that copper has been doped in the form of cations or in the form of oxides. XPS analysis confirms that the copper exists as Cu(I) and Cu(II). The nitrogen sorption isotherms reveal that the modified samples are mesoporous in nature. The pore volume and diameter were found to be enhanced by the modification. The better textural properties and acidic properties of the Cu‐ZSM‐5 can make it suitable for catalyzing organic reactions.