Fabrication of a NiFe Alloy Oxide Catalyst via Surface Reconstruction for Selective Hydrodeoxygenation of Fatty Acid to Fatty Alcohol

Abstract

Traditional NiFe alloy catalyst (NiFe AC) possesses low alcohol selectivity for the hydrodeoxygenation (HDO) of fatty acid due to its excessive deoxygenation into alkane. Herein, we innovatively provide the NiFe alloy oxide catalyst (NiFe AOC) to suppress the adsorption of aldehyde, which is the crucial intermediate of objective product alcohol converting into a side product, via the steric hindrance of lattice oxygen to inhibit the further conversion of alcohol. NiFe AOC reaches 100% conversion of lauric acid with 90% selectivity to lauryl alcohol. Kinetic analysis indicated that the apparent activation energy of side reaction increases by 71.1 kJ/mol for NiFe AOC relative to NiFe AC, evidencing the inhibition for the conversion of objective product alcohol into alkane for NiFe AOC. Furthermore, DFT calculation also suggests that the activation energy of the side reaction increases by 0.33 eV on NiFe AOC compared to NiFe AC. In addition, used NiFe AOC can be totally regenerated via surface reconstruction during the reduction–reoxidation treatment. However, overoxidation inducing NiFe surface phase separation weakened the synergistic interaction of Ni–Fe bimetallic sites and further decreased the catalytic activity.

NiCu Anchored on a Specific TiO2 Face Tunes Electron Density for Selective Hydrogenation of Fatty Acids into Alkanes or Alcohols

“…18,20 For example, the NiFe alloy oxide catalyst can provide the steric hindrance of lattice oxygen to inhibit the further conversion of alcohol, which can reach 100% conversion and 90% selectivity for lauric acid converting to lauryl alcohol. 7 Inspired by these findings, we think that the Ni and Cu combination could be a good candidate for the alcohol production.…”

“…However, the Ni metal is more active in deoxygenation and C–C bond cracking, which can produce undesirable alkane products. Therefore, the over-hydrogenation reaction can be inhibited by modifying another metal (In or Fe) or appropriate metal oxide. , For example, the NiFe alloy oxide catalyst can provide the steric hindrance of lattice oxygen to inhibit the further conversion of alcohol, which can reach 100% conversion and 90% selectivity for lauric acid converting to lauryl alcohol . Inspired by these findings, we think that the Ni and Cu combination could be a good candidate for the alcohol production.…”

“…Especially, Nibased catalysts, due to the low-cost Ni metal, show remarkable hydrogen dissociation activity, which can perform excellent reaction activity in fatty acid conversion. 7 It is commonly known that hydrogenation conversion of fatty acids into alkanes is mainly carried out through three processes, hydrodeoxygenation, decarbonylation, and decarboxylation, which removed the O atom in the form of H 2 O, CO, and CO 2 , respectively. 8 Among these, it was found that fatty alcohols can be detected as an essential intermediate during the hydrodeoxygenation processes.…”

“…Hence, cost-efficient and sulfur-free catalysts have attracted extensive attention, using transition metals and alloys. Especially, Ni-based catalysts, due to the low-cost Ni metal, show remarkable hydrogen dissociation activity, which can perform excellent reaction activity in fatty acid conversion …”

Engineering a Ni1Fe1–ZnO Interface to Boost Selective Hydrogenation of Methyl Stearate to Octadecanol

“…Compared with Cu-based catalysts, Ni-based catalysts are substantially cheaper and display higher hydrogenation activity and anti-sintering properties, thus promising broad application prospect in hydrogenation. However, in addition to the hydrodeoxygenation reaction, Ni also has high activity for decarboxylation/decarbonylation and C–C single bond hydrogenolysis, resulting in the lower selectivity of Ni-based catalysts in fatty acid ester hydrogenation reactions. − To overcome problems mentioned above, one strategy is to modify the Ni-based catalysts with second metals (Re, , Sn, Fe, − and In) to form alloys or intermetallic compounds; this changes the adsorption conformation of the nickel metal surface from η 1 (C)-acyl conformation, which is predominantly decarbonated/decarboxylated, to the η 2 (C,O) conformation, which is easily converted to alcohols by hydrogenation, converting to suppress the occurrence of side reactions . Meanwhile, the second metal serves as a Lewis site to activate the ester group by adsorbing oxygen, which is further attacked by hydrogen activated on the metal/alloy surface to produce alcohol. , Furthermore, the intensity of the metal–oxygen bonds was a critical factor in the determination of the ability of the oxides to combine and activate acids for their reduction.…”