Nanocatalysts Derived from Copper Phyllosilicate for Selective Hydrogenation of Quinoline

1,2,3,4-Tetrahydroquinoline (py-THQ) is a vital intermediate that is used in the production of medicines, agricultural chemicals, and other fine chemicals and is synthesized through the selective hydrogenation of quinoline. In this work, copper phyllosilicate catalysts were prepared by four different synthesis methods: deposition precipitation, ammonia evaporation, a urea-assisted gel method, and hydrothermal treatment. It was found that the different synthesis strategies led to different actual loadings of copper in the precursors. The optimal catalyst showed a py-THQ selectivity of 99.9% at a full conversion of quinoline in ethanol at 100 °C and 3.0 MPa H2 for 2 h. The remarkable enhancement of the performance may be attributed to the small particle size, the coexistence of Cu0 and Cu+, and the strong interaction of copper phyllosilicate by the deposition precipitation preparation method. The characterization results showed that Cu0 and Cu+ were generated during the restoration process and were derived from CuO and layered copper phyllosilicates, respectively. Additionally, the ratio of Cu+/(Cu+ + Cu0) changed with the reduction temperature. The strategy of the catalyst design and synthesis developed in this work has potential applications in other nitrogen heterocyclic hydrogenation reactions.