The Preparation Of CePO₄/Co₂P Catalyst And Its Hydrogenation Performance In Liquid Phase

Liquid phase catalytic hydrogenation reaction is a key process in chemical production,currently,it mainly relies on precious metal catalysts such as platinum and palladiumand.In view of the inherent limitations of these kinds of catalysts,such as easy sintering,easy passivation or poisoning,easy corrosion（under acidic conditions）and high cost,developing non-metallic catalysts with low cost,good catalytic activity,high selectivity and recyclability have been receiving much attention.Therefore,in view of this situation,this paper attempts the following research:（1）Using Co（NO₃）₂·6H₂O,Ce（NO₃）₃·6H₂O,（NH₄）₂HPO₄ as raw material,A series of Co-P-Ce catalysts with different Ce:Co molar ratios were prepared by thermal reduction of composites obtained by solvothermal one-pot method.According to the characterization results of ICP-OES,XRD,XPS,SEM,HRTEM and EDS-Mapping showed that the obtained Co-P-Ce catalyst is a composite structural material which is tightly bound by CePO₄ and Co₂P.The catalyst can be denoted as（CePO₄）_m/Co₂P,the molar ratio（m）of CePO₄:Co₂P was controlled within the range of 0.04-0.34.（2）Taking CePO₄ and Co₂P as the comparison samples,the（CePO₄）_m/Co₂P composite catalyst has excellent selective catalytic hydrogenation performance:For the hydrogenation of citral,the（CePO₄）_m/Co₂P（0.04≤m≤0.34）catalyst could achieve the conversion of 85-100%at 3 MPa and 145℃,and the selectivity to citronellol could be as high as 80%;For the hydrogenation of levulinic acid,when water is used as solvent,the（CePO₄）_0.16/Co₂P sample could achieve a high yield ofγ-valerolactone of98%under the reaction conditions of 4 MPa,90℃,90 min,at the same time,it exhibited excellent acid corrosion resistance and recyclability.（3）In view of the excellent performance of（CePO₄）_m/Co₂P catalyst for the hydrogenation of levulinic acid,the kinetics and reaction mechanism were also explored.The comparison of H₂-TPD,NH₃-TPD and pyridine adsorption infrared spectroscopy showed that the hydrogenation reaction of levulinic acid on the catalyst followed the L-H mechanism,that is,the hydrogen species activated at the CePO₄ site were surface-reacted with the levulinic acid or related intermediate species activated at the Co₂P site,then selectively formedγ-valerolactone by isomerization dehydration.Based on the synergistic catalysis of the two components,the reaction activation energy was significantly reduced,and the conversion frequency（TOF）of the reaction can reach 0.27-0.61 s^-1.This result is comparable to the TOF value of the classical precious metal catalysts reported today for the hydrogenation of levulinic acid.To sum up,a novel（CePO₄）_m/Co₂P non-noble metal catalytic hydrogenation catalyst was successfully synthesized in this paper.This kind of catalyst for some reactions,especially the hydrogenation of levulinic acid,which plays an important role in biomass conversion,showed no less excellent activity than noble metal catalyst.At the same time,compared with metal catalysts,the characteristics of structural stability,poisoning resistance and acid corrosion resistance also give the potential of such a structural catalyst to replace the metal catalyst to be applied in more hydrogen-involved catalytic conversion reactions which require strict reaction conditions,so it is worthy of attention and research.