Research On Copper-based Catalysts Derived From MOFs And Their Hydrogenation Performance

The 2,5-dimethylfuran?DMF?obtained from the selective hydrogenation of biomass platform compound 5-hydroxymethylfurfural?HMF?is a potential high-quality liquid fuel,and the development of a low-cost catalyst or catalytic system that can efficiently convert HMF into DMF under mild conditions is the key to this research.In this paper,the precursor of Cu₃?BTC?₂?HKUST-1?metal-organic framework material was synthesized by hydrothermal method,followed by heat treatment to prepare a series of MOFs-derived monometallic copper catalysts.It was found that the catalyst prepared by the two-step method of pyrolysis in N₂ atmosphere at 450 ^oC and then heat treatment in 1%O₂-N₂ atmosphere at250 ^oC had the highest activity.At the reaction temperature of 180 ^oC and a hydrogen pressure of 3 MPa,after 4 hours of reaction,the catalyst achieved 100%of HMF conversion and 92%of DMF selectivity,higher than the copper catalyst reported in other literature.Through X-ray diffraction,nitrogen de-adsorption X-ray photoelectron spectroscopy,Raman spectroscopy and electron microscopy and other characterization methods,it is found that the catalyst has a Cu₂O/Cu composite structure and the synergistic effect of Cu⁺and Cu⁰ is the key to the high catalytic activity.After 4 cycles of the catalyst,the activity has a greater degree decline for the reason that the HMF thermal polymerization formed the carbon polymer can cover the active sites of the catalyst surface and the instability of the Cu⁺active species,under reaction conditions.In order to improve the activity at low temperature and the stability of the catalyst,the preparation method was optimized and introduced the second metal component to the catalyst.The research found that the catalyst obtained from PVP-assisted static precipitation method and through one-step pyrolysis in a nitrogen atmosphere of 750 ^oC showed higher activity.At the reaction temperature of 150 ^oC and a hydrogen pressure of 2.5 MPa,after 3hours of reaction,the activity result is higher than the above catalyst prepared by the two-step pyrolysis.Through introduced the cobalt to the catalyst,the catalyst activity is significantly improved.When the Co doping amount is 20%,at a reaction temperature of 150 ^oC and a hydrogen pressure of 2.5 MPa,after 3 hours of reaction,the catalyst achieved 100%of HMF conversion and 85%of DMF selectivity.Moreover,the stability of the catalyst has been further improved,after five cycles of reaction,the activity of catalyst has not significantly decreased.X-ray diffraction,nitrogen de-adsorption,X-ray photoelectron spectroscopy,Inductive coupled plasma optical emission spectrometer and other characterization methods were used to analyze the structure of the catalyst.The result shown that the cobalt component in the catalyst mainly exists in the form of oxides,and the cobalt oxide enhances the hydrogenation activity of the catalyst for the C-O bonds and reduces the temperature required for the reaction.The high stability of cobalt oxide keeps the catalyst stable in the cycle test,effectively improving the stability of the catalyst.