Direct synthesis of cyclohexylamine from cyclohexene and NH3 over ZSM-5 catalysts: Impact of mesoporosity and acidity

Abstract

Developing 100% atomically economic reaction of direct amination cyclohexene with NH3 is important but challenging for the synthesis of cyclohexylamine. This work describes a novel strategy of employing HZSM-5 zeolites with mesomicro-pore architecture as a solid acid catalyst for this reaction. The mesoporous HZSM-5 compared to the referenced microporous ZSM-5 delivers outstanding catalytic activity, providing cyclohexylamine selectivity of 95.6% and 4.9% conversion at 9 MPa and 300 oC. The relationship of zeolite structure and catalytic activity is established by using multiple techniques, such as XRD, SEM, TEM, N2 adsorption-desorption, Py-FTIR and NH3-TPD. The pore structure and Brønsted-acid sites of zeolites played crucial roles in cyclohexene amination reaction Based on in situ FT-IR spectroscopy and DFT simulations, the adsorption of reactants and desorption of products, and molecular diffusion on the mesoporous HZSM-5 suggested that the accessible Brønsted acid sites in the 10-MR microporous channels are the factors controlling the catalytic process.