Alloying effect enhanced bimetallic Ni-Fe/TiO₂ catalysts for selective hydrogenation of 1,3-butadiene in the presence of an excess of propylene

Nickel is a promising Pd alternative candidate for selective alkynes/alkadienes hydrogenation owing to its high catalytic activity and cheap price, however, with fatal restrictions of low alkenes selectivity and inferior stability caused by its strong olefin adsorption and the cleavage of carbon-carbon bond. Herein, controlled amounts of iron were introduced into nickel as catalytic assistant by deposition-precipitation with urea on TiO₂ support. Using 1,3-butadiene in an excess of propylene to simulate the industrial process, the additional Fe shows a significant enhancement to the catalytic performance of Ni, i.e., Ni-Fe/TiO₂ with Ni/Fe atomic ratio 1:0.33 shows >94% of 1,3-butadiene conversion and >95% of alkenes selectivity after above 200 h of time on stream, superior to that of commercial Pd/Al₂O₃ catalyst. Further in-situ analysis reveals that the alloying effect from the formation of Ni-rich Ni-Fe intermetallic compound (e.g., Ni₃Fe alloy) enlarges the distance between two Ni active sites and enriches the electronic density of Ni sites, resulting in a weak adsorption of butenes products for offering such excellent catalytic performance. To the best of our knowledge, this is the first in-depth exploration on supported Ni-Fe bimetallic catalyst for selective hydrogenation of light alkynes/alkadienes. It shows a high potential for replacing the commercial Pd-based catalysts.