Sintering-resistant and active-species-adjustable Ni catalysts supported on P-doped biochar via nanopore-confined activation for efficient levulinic acid hydrogenation

Abstract

The nanopore-confining strategy is an effective way to inhibit catalyst sintering and improve catalytic performance. However, the expensive material precursors and complex preparation process greatly limit the scalable application of this particularly structured catalyst. Herein, nanopore-confined catalysts (Ni@PAC) with adjustable active species were successfully prepared by a very simple method exploiting the characteristics of phosphoric acid-activated biochar (PAC). The abundant phosphorus functional groups in PAC confined Ni well in the pores and significantly inhibited sintering through the spatial confinement effect of nanopores. Moreover, the evolution and migration of P functional groups can be regulated by changing the reduction temperature, and the modulation of active species of Ni metal or nickel phosphide can be achieved. Using biomass-based levulinic acid hydrogenation as the probe reaction, it was found that the catalytic activity of 20Ni@PAC-600 was one order of magnitude higher than that of the non-phosphated 20Ni/ZAC-600 catalyst, and γ-valerolactone could be selectively prepared at near atmospheric pressure (1 bar). The formation of Ni₂P and the spatial confinement effect of nanopores could be the main reasons for the high catalytic activity.