Preparation and characterization of Ni/mZSM-5 zeolite with a hierarchical pore structure by using KIT-6 as silica template: an efficient bi-functional catalyst for the reduction of nitro aromatic compounds

Abstract

Ni/mZSM-5 and Ni/H-mZSM-5 were synthesized as hierarchical (micro/meso porous) ZSM-5 zeolites by an indirect template method for the first time. The resulting zeolite materials exhibited significantly enhanced diffusional properties in comparison to purely microporous zeolite materials. The structural and morphological characterization of the prepared catalysts was investigated using XRD, BET, atomic absorption spectroscopy, FT-IR, ²⁷Al-MAS NMR, SEM, TEM, XPS and DRS-UV techniques. These hierarchical zeolites were used as acid–metal bi-functional heterogeneous catalysts for hydride transfer in the reduction of nitro aromatic compounds. In these reactions, NaBH₄ was used as a reducing agent. Excellent yields at room temperature and very short reaction times in aqueous media conditions were obtained. Reusability experiments showed the excellent stability of Ni/mZSM-5 and Ni/H-mMZSM-5 and the catalysts could be reused 7 times without much loss of activity in reduction of nitro aromatic compounds. Surprisingly, the acid form of Ni/H-mZSM-5 showed much higher activity than that of Ni/mZSM-5. High yield, short reaction time, green solvent (water), room temperature, no by-product, the easy reusability of catalysts and the low amounts of catalyst required are some of the advantages of these catalysts.