638
H-donor solvent and 10Cu-1Pd/RGO as a catalyst, afforded an excellent DMF yield
of 95% with 96% HMF conversion at 453 K under 15 bar H 2 pressure and a flowrate
of 0.2 mL min
−1
[86]. The presence of Pd-Cu alloy was found to be associated with
the higher activity and stability of the catalyst. Yang et al. developed carbonsupported Ni-Co bimetallic catalyst (2%Ni-20%Co/C) for the CTH of HMF to
DMF with a yield of 90% at 483 K after 24 h in the presence of formic acid as the
H 2 source [89]. The high catalytic activity was attributed to the specific structural
properties in the form of hybrid nanomorph exhibiting oxophilic nature and Lewis
acidity of Fe, whereas the high selectivity toward DMF was due to the Brønsted
acidity of CuO and its affinity for the C–O bond.
A reaction mechanism was also proposed for the hydrogenation of HMF to DMF
over metal-metal nano-hybrid catalyst (i.e., Cu-Fe catalyst) (Fig. 5). The initial activation of 5-HMF occurs through the –C=O group by the Lewis acidity and oxophilic nature of Fe by attacking its electron-rich oxygen. As a result, the H 2 molecule
which dissociates on the metallic Cu of the Cu-Cu-Fe 2 O 4 nanomorph attacks the
electrophilic carbon of the –C=O group giving BHMF as an initial reaction intermediate. This enhances the rapid dehydration of BHMF into DMF via
MFAL. Furthermore, Han et al. recently developed ordered mesoporous alumina
supported Ni-Mo sulfide catalyst (Ni-MoS 2 /mAl 2 O 3 ) by evaporation-induced selfassembly method for catalyzing the selective hydrogenolysis of HMF to DMF [90].
The yield of DMF could reach to 95% DMF over 5Ni-7MoS 2 /mAl 2 O 3 under the
mild reaction conditions of 403 K for 6 h at a H 2 pressure of 1 MPa using isopropanol as the H-donating solvent. The characterization results and DFT calculation
suggests that the active site was a coordinated unsaturated site located at S-edge and
the intrinsic activity of coordinated unsaturated site was directly related to the proportion of Mo replaced by Ni.
2.2 Oxidation of Furanics
2.2.1 Furfural
The selective oxidation of FUR can produce various C4-oxygenated products, such
as acid anhydrides (malic anhydride (MAN)), dicarboxylic acids (succinic (SA),
malic (MA), and fumaric acids (FAc)), and furanone (FU) (Fig. 6). Among them,
MAN is an attractive value-added chemical used in the manufacture of lubricant,
unsaturated polyester resins, surface coatings, plasticizers, co-polymers, coatings,
and pharmaceuticals. Several renewable routes for the catalytic oxidation of FUR to
MAN have been reported. Supported vanadium oxide catalysts have been studied
for decades for the gas-phase oxidation of FUR to MAN in the presence of air or
oxygen, where MAN yields in the range of 15–90% have been described. AlonsoFagúndez et al. reported a considerably high yield of 73% for MAN at 100% FUR
conversion during the vapor-phase oxidation of FUR in the presence of VO x /Al 2 O 3
as a solid catalyst for under the conditions of 593 K and 5.7 kPa O 2 [5]. When
M. Baithy et al.
H-donor solvent and 10Cu-1Pd/RGO as a catalyst, afforded an excellent DMF yield
of 95% with 96% HMF conversion at 453 K under 15 bar H 2 pressure and a flowrate
of 0.2 mL min
−1
[86]. The presence of Pd-Cu alloy was found to be associated with
the higher activity and stability of the catalyst. Yang et al. developed carbonsupported Ni-Co bimetallic catalyst (2%Ni-20%Co/C) for the CTH of HMF to
DMF with a yield of 90% at 483 K after 24 h in the presence of formic acid as the
H 2 source [89]. The high catalytic activity was attributed to the specific structural
properties in the form of hybrid nanomorph exhibiting oxophilic nature and Lewis
acidity of Fe, whereas the high selectivity toward DMF was due to the Brønsted
acidity of CuO and its affinity for the C–O bond.
A reaction mechanism was also proposed for the hydrogenation of HMF to DMF
over metal-metal nano-hybrid catalyst (i.e., Cu-Fe catalyst) (Fig. 5). The initial activation of 5-HMF occurs through the –C=O group by the Lewis acidity and oxophilic nature of Fe by attacking its electron-rich oxygen. As a result, the H 2 molecule
which dissociates on the metallic Cu of the Cu-Cu-Fe 2 O 4 nanomorph attacks the
electrophilic carbon of the –C=O group giving BHMF as an initial reaction intermediate. This enhances the rapid dehydration of BHMF into DMF via
MFAL. Furthermore, Han et al. recently developed ordered mesoporous alumina
supported Ni-Mo sulfide catalyst (Ni-MoS 2 /mAl 2 O 3 ) by evaporation-induced selfassembly method for catalyzing the selective hydrogenolysis of HMF to DMF [90].
The yield of DMF could reach to 95% DMF over 5Ni-7MoS 2 /mAl 2 O 3 under the
mild reaction conditions of 403 K for 6 h at a H 2 pressure of 1 MPa using isopropanol as the H-donating solvent. The characterization results and DFT calculation
suggests that the active site was a coordinated unsaturated site located at S-edge and
the intrinsic activity of coordinated unsaturated site was directly related to the proportion of Mo replaced by Ni.
2.2 Oxidation of Furanics
2.2.1 Furfural
The selective oxidation of FUR can produce various C4-oxygenated products, such
as acid anhydrides (malic anhydride (MAN)), dicarboxylic acids (succinic (SA),
malic (MA), and fumaric acids (FAc)), and furanone (FU) (Fig. 6). Among them,
MAN is an attractive value-added chemical used in the manufacture of lubricant,
unsaturated polyester resins, surface coatings, plasticizers, co-polymers, coatings,
and pharmaceuticals. Several renewable routes for the catalytic oxidation of FUR to
MAN have been reported. Supported vanadium oxide catalysts have been studied
for decades for the gas-phase oxidation of FUR to MAN in the presence of air or
oxygen, where MAN yields in the range of 15–90% have been described. AlonsoFagúndez et al. reported a considerably high yield of 73% for MAN at 100% FUR
conversion during the vapor-phase oxidation of FUR in the presence of VO x /Al 2 O 3
as a solid catalyst for under the conditions of 593 K and 5.7 kPa O 2 [5]. When
M. Baithy et al.