Effective Inhibition of Ethane Generation on Fe5C2 Nanoparticles Doped with ppm Level of Pd for Selective Hydrogenation of Acetylene

Overhydrogenation to ethane is most undesired in selective hydrogenation of acetylene. Monometallic Pd supported on common oxide supports such as alumina and silica suffers from susceptibility of ethane formation, and the ethylene selectivity is usually unsatisfactory. Herein, Fe5C2 was carefully synthesized and employed as a new kind support doped with a (5–600) ppm level of Pd for selective hydrogenation of acetylene. The catalyst with appropriate Pd loadings exhibited more efficient ethane suppression and much higher ethylene selectivity than the traditional α-Al2O3 supported Pd catalyst, with full acetylene conversion under 240 °C, and maintained good stability after a 200 h tolerance test. Characterization and DFT calculation results reveal that the excellent ethylene selectivity is mainly derived from the special interaction between Pd atoms and the Fe5C2 support. Hydrogenation of ethylene to ethane needs to cross extremely high activation energy barriers on the catalyst surface, and ethylene desorption more easily occurs on it. Doping the appropriate amount of Pd atoms on the Fe5C2 surface can increase the obstacle for polymerization and will cause the unsaturated C2 species to be more inclined to be hydrogenated into C2H4. This synergy effect also acts as a guide in alkane suppression for selective hydrogenation of other alkynes.