Graphene Encapsulated Ni Catalyzed Reductive Amination of VOC Aldehydes to High Value Chemicals by industrial continuous flow synthesis

Volatile organic compounds (VOCs) include many types of organic compounds, such as alkanes, olefins, aldehydes, etc. They have attracted widespread attention in various fields such as food and flavor analysis, environmental and atmospheric research, safety, or healthcare. Developing efficient, practical, and high-value industrial VOC utilization technologies is crucial for sustainable social and human development. Aldehydes are one of the main components of VOCs, with C=O functional groups. Therefore, various conversion pathways such as reduction and oxidation can be used to achieve the utilization of VOC aldehyde compounds. One of the technologies is the reductive amination of aldehydes into amines, which are widely used as raw materials, drugs, pharmaceuticals, pesticides, etc. The synthesis of benzylamine by reductive amination of benzaldehyde is difficult to produce benzylamine specifically with high selectivity due to the complex pathway, and the currently applied catalysts generally have disadvantages such as poor cyclability. Enantioselective hydrogenation reactions over heterogeneous catalysts are advantageous for implementation in flow reactor systems for industrial applications due to their inherent operational and economic advantages, such as easy separation, low cost and environmental friendliness of heterogeneous catalysts. This work reports a catalyst with Ni nanoparticles encapsulated in a thin graphene shell, which successfully achieved the efficient of benzaldehyde to benzylamine under mild conditions (60 °C, 1 MPa), with the conversion of 99.99% and the selectivity of 94.59%. The catalyst is simple and inexpensive to prepare, and the graphene shell reduces the loss of catalyst during the reaction while increasing the catalytic active sites, making the catalyst efficient and stable with excellent recyclability. The reaction system is carried out in a flow reactor, where H2 and NH3 are involved simultaneously, ensuring safety while improving the mass and heat transfer of the reaction, and the overall conversion is substantially improved compared to that of the batch reactor.