Within the realm of heterogeneous catalysts, nanocatalysts are preferred due to the elevated activity and efficient utilization of materials. The later becomes very important in case of low reservoir abundance of noble metals in the earth. Since using precious metals is indispensable due to their high reactivity under mild conditions, it is necessary to minimize their use and improve their sustainability by emphasizing recovery and reuse. However, there are major practical challenges in using nanocatalysts because of their easy agglomeration during the catalytic process and the difficulty in separation from products. A strategy to avoid their mobility and improve their separability is anchoring them on a support. While metal foams have been used extensively in electrochemical and electrocatalytic applications, their utility in catalysis is comparatively underexplored. Foams have the potential for direct application in flow processes. Ni foam has the characteristics of easy handling and manipulation, high stability, inherently contiguous macroporous structure, low cost, commercial availability, and environment friendliness. Herein, we report the synthesis of a highly reactive and incredibly robust hierarchical monolith-based catalyst. Pt/Ni@Al2O3 was created through a facile hydrothermal process, followed by encapsulation with a thin layer of ALD Al2O3.The materials possesses a highly disperse Pt sites with ultra-low loading of precious metal (in the ppb range). The catalytic performance of the material was evaluated by hydrogenation of styrene with H2 gas under mild conditions (50 °C, 3 bar H2). Encouragingly, Pt/Ni@Al2O3 presents high TON (~ 160 × 106 for Pt as the active component) for the hydrogenation of styrene. Recyclability trials show negligible loss of reactivity over ten trials as tested. Various structure-reactivity relationships, including choice of Pt precursor and protective overlayer of Al2O3 are tested and discussed, and catalytic substrate scope broadly expanded. Overall, the catalyst system appears robust, facile to handle, and promising as a means of dramatically enhancing Pt catalyst sustainability by enhancing reuse and recovery.

Highly reactive and robust monolith-supported Pt catalysts for olefin hydrogenation

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