Cooperative activation of H2 with H2O or NH3 enables efficient furfural upgradation over Ni2P/REPO4 catalysts: a family feature of lanthanide rare-earth phosphates

Abstract

The innovation of effective catalysts capable of cooperatively activating multiple small molecules is of great importance for boosting the corresponding chemical upgradation. Here, the potential of lanthanide rare-earth phosphates (REPO₄) for activating H₂, H₂O and NH₃ was demonstrated by integrating nine rare-earth components (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, and Y) in Ni–RE–P catalysts for converting furfural into cyclopentanone (CPO) or furfurylamine (FFA). ICP-OES, XRD, XPS, SEM, and HRTEM characterizations revealed that these catalysts possessed a structure of Ni₂P supported on REPO₄ (Ni₂P/REPO₄), with an Ni mass loading of around 10%. Under mild pressures of 0.5–1.0 MPa, significant enhancements in catalytic performance were exhibited by the Ni₂P/REPO₄ catalysts versus Ni₂P/SiO₂, such as 75–90% vs. 4% in terms of CPO yield and 67–99% vs. 22% in terms of FFA yield. These results position Ni₂P/REPO₄ among the top-performing catalysts reported to date. Using isotope tracing, in situ IR spectroscopy, TPD-MS measurements and DFT calculations, the catalytic superiority of Ni₂P/REPO₄ could be attributed to its ability to cooperatively activate H₂ with H₂O or NH₃ using REPO₄. Specifically, RE and O sites on REPO₄ could function as acid–base pair sites with comparable distribution and strength, essential for facilitating the cooperative activation of these small molecules and facilitating the complicated mechanism for the three-molecule-involved furfural upgradation conversions. These results highlighted the family feature of REPO₄ as a versatile and efficient component for catalytic transformations involving multiple small molecules, providing a new reference for designing outstanding multi-functional catalytic systems with a simple composition to advance the corresponding chemical engineering applications.