Combined DFT and microkinetic modeling study of SO2 hydrodesulfurization reaction on Ni5

Direct deoxygenation reaction of oxygenated model compounds by biomass pyrolysis on the Ni5P4(001) surface: a computational study

“…The Ni 5 P 4 (001) surface was considered in this work because it is the most stable facet of the Ni 5 P 4 crystal. 33 This surface was represented with a supercell having the dimensions of 3 × 3 cells and vacuum space with a thickness of 20 Å. This cell is in agreement with He et al , 23,24 who considered 2 × 2 and 3 × 3 slab dimensions for Ni 2 P to study the HDO of phenol and guaiacol molecules, respectively.…”

“…Afterwards, the OH species transfer from the P-top site to the Ni 3 -hollow site to combine with atomic H, thereby resulting in the formation of H 2 O (R7) with an activation energy of 2.35 eV, which coincides with the value 2.37 eV reported in previous work. 33 This endothermic step requires a reaction energy of 0.94 eV. The overall deoxygenation reaction of phenol over the Ni 5 P 4 (001) substrate is an endothermic process with an activation energy of 0.18 eV, as depicted in Fig.…”

“…These adsorption geometries coincide well with a previous DFT study. 33 This reaction step is thermodynamically and kinetically favorable, surmounting a reaction energy and kinetic barrier of −0.76 and 0.12 eV, respectively. Concerning the phenol dissociation step (R2), as depicted in Fig.…”

“…Specically, the proportion of three-fold Ni positions, which strongly adsorb atomic hydrogen, are greatly reduced compared to Ni 2 P due to the abundance of phosphorus (P) atoms, which suppress the deactivation of the Ni 5 P 4 catalyst. 33,34 He et al 23 reported that a decrease in the Ni/P ratio in Ni x P y catalysts weakens the molecule/catalyst interaction, which is ascribed to the fact that metal-rich Ni (high Ni/P ratio) ceramics possess hybridized electronic structures, resulting in aggressive Ni-like surface reactivity. 23 This weakened interaction can suppress the unwanted ring-opening and ring-hydrogenation reactions.…”

Metal-Free Phosphated Mesoporous SiO2 as Catalyst for the Low-Temperature Conversion of SO2 to H2S in Hydrogen

“…Recently, our group reported on Ni 2 P and Ni 5 P 4 catalysts for the selective hydrogenation of SO 2 to S and H 2 S [16,17]. By fine control of the phase, size, and morphologies of nickel phosphide, the SO 2 hydrogenation process can take place in the temperature range of 200-300 • C. DFT studies of Ni 2 P and Ni 5 P 4 catalysts have investigated the stability of different surfaces of nickel phosphides, which provide a deeper understanding of the adsorption and desorption of SO 2 and H 2 on the surface of nickel phosphide catalysts [18][19][20].…”