641
vanadium oxide catalysts are used, the active sites are reduced by FUR and reoxidized by oxygen, and the reoxidation of the reduced catalyst has been identified as
the rate-determining step. In 2014, Lan et al. found that 54% yield of MAN and
7.5% yield of 5-acetoxyl-2(5H)-furanone were obtained at 98.7% conversion of
FUR over H 5 PV 2 Mo 10 O 40 and Cu(CF 3 SO 3 ) 2 as catalysts [95]. Furthermore, Li et al.
synthesized a vanadium phosphorous oxide (VPO HT )-based plate catalyst via a
hydrothermal method with glucose as a reducing agent for the gas-phase oxidation
of FUR to MAN [96]. They found that developed catalyst has predominantly 200
exposed crystal planes responsible for the remarkable activity, selectivity, and stability. VPO HT gave 90% MAN yield at 633 K in 21% O 2 /N 2 atm and demonstrated
stable activity up to 25 h time on stream (Table 5). Recently, Santander et al. investigated the gas-phase oxidation of FUR over vanadium supported on SiO 2 , γ-Al 2 O 3 ,
ZrO 2 , and TiO 2 , where they demonstrated that catalytic properties during the oxidation reaction depend both on the nature of the support and dispersion of vanadium
[97]. Among the different supported catalysts, V 2 O 5 /γ-Al 2 O 3 and V 2 O 5 /SiO 2 displayed higher activity with 49% and 36% MAN yield at 573 and 593 K.
MA is another important intermediate of C 4 compounds in the chemical industry.
Different methods have been reported for the green oxidation of FUR to MA either
in gas or liquid phase. Recently, Rezaei et al. developed a VZPK catalyst by stabilizing a mixture of vanadium and zirconium supported over KIT-6 to oxidize FUR to
MA in the presence of H 2 O 2 . A 29.2% MA yield at 81.2% FUR conversion was
obtained in the presence of VZPK1 (0.25 Zr/V ratio loading) at 343 K after 1 h with
3:1 (H 2 O 2 /FUR mole ratio) in acetonitrile as the solvent [98].
2.2.2 5-Hydroxymethyl Furfural (HMF)
Based on the position and degree of HMF oxidation, various high-value derivatives,
such as 5-hydroxymethylfuroic acid (HMFCA); 2,5-diformylfuran (DFF);
5- formyl-2-furancarboxylic acid (FFA) [99]; 2,5-furandicarboxylic acid (FDCA);
maleic anhydride (MA); and maleic acid (MAc), can be selectively produced.
The selective oxidation of HMF to DFF remains a great challenge that requires
the controlled oxidation of its primary hydroxyl group while leaving the aldehyde
group intact. Recently, to improve the selectivity of DFF, considerable efforts have
been devoted to the design of highly active and selective heterogeneous catalyst.
Among noble metals, γ-Al 2 O 3 -supported Ru catalyst was reported to convert 99%
of HMF with 97% DFF selectivity at 403 K after 4 h and 40 psi O 2 pressure in toluene as a solvent [101], whereas Nie et al. reported that Ru/C achieved 96% DFF
yield with complete HMF conversion under the conditions of 383 K and 2.0 MPa O 2
in toluene [102]. Other Ru-based catalysts have also gained excellent yield and
selectivity for DFF during the oxidation of HMF [103, 104, 115]. Non-noble metal
catalyst based on V, Co, Cu, and Mn and mixed oxides were also developed for the
oxidation of HMF to DFF [105–112]. Zhang et al. synthesized a vanadium oxide
supported Cu-MOR zeolites (10%V 2 O 5 @Cu-MOR(125)) for the oxidation HMF,
where 91.5% yield for DDF was achieved at 393 K for 7 h in DMSO with
Efficient Nanocomposite Catalysts for Sustainable Production of Biofuels and…
vanadium oxide catalysts are used, the active sites are reduced by FUR and reoxidized by oxygen, and the reoxidation of the reduced catalyst has been identified as
the rate-determining step. In 2014, Lan et al. found that 54% yield of MAN and
7.5% yield of 5-acetoxyl-2(5H)-furanone were obtained at 98.7% conversion of
FUR over H 5 PV 2 Mo 10 O 40 and Cu(CF 3 SO 3 ) 2 as catalysts [95]. Furthermore, Li et al.
synthesized a vanadium phosphorous oxide (VPO HT )-based plate catalyst via a
hydrothermal method with glucose as a reducing agent for the gas-phase oxidation
of FUR to MAN [96]. They found that developed catalyst has predominantly 200
exposed crystal planes responsible for the remarkable activity, selectivity, and stability. VPO HT gave 90% MAN yield at 633 K in 21% O 2 /N 2 atm and demonstrated
stable activity up to 25 h time on stream (Table 5). Recently, Santander et al. investigated the gas-phase oxidation of FUR over vanadium supported on SiO 2 , γ-Al 2 O 3 ,
ZrO 2 , and TiO 2 , where they demonstrated that catalytic properties during the oxidation reaction depend both on the nature of the support and dispersion of vanadium
[97]. Among the different supported catalysts, V 2 O 5 /γ-Al 2 O 3 and V 2 O 5 /SiO 2 displayed higher activity with 49% and 36% MAN yield at 573 and 593 K.
MA is another important intermediate of C 4 compounds in the chemical industry.
Different methods have been reported for the green oxidation of FUR to MA either
in gas or liquid phase. Recently, Rezaei et al. developed a VZPK catalyst by stabilizing a mixture of vanadium and zirconium supported over KIT-6 to oxidize FUR to
MA in the presence of H 2 O 2 . A 29.2% MA yield at 81.2% FUR conversion was
obtained in the presence of VZPK1 (0.25 Zr/V ratio loading) at 343 K after 1 h with
3:1 (H 2 O 2 /FUR mole ratio) in acetonitrile as the solvent [98].
2.2.2 5-Hydroxymethyl Furfural (HMF)
Based on the position and degree of HMF oxidation, various high-value derivatives,
such as 5-hydroxymethylfuroic acid (HMFCA); 2,5-diformylfuran (DFF);
5- formyl-2-furancarboxylic acid (FFA) [99]; 2,5-furandicarboxylic acid (FDCA);
maleic anhydride (MA); and maleic acid (MAc), can be selectively produced.
The selective oxidation of HMF to DFF remains a great challenge that requires
the controlled oxidation of its primary hydroxyl group while leaving the aldehyde
group intact. Recently, to improve the selectivity of DFF, considerable efforts have
been devoted to the design of highly active and selective heterogeneous catalyst.
Among noble metals, γ-Al 2 O 3 -supported Ru catalyst was reported to convert 99%
of HMF with 97% DFF selectivity at 403 K after 4 h and 40 psi O 2 pressure in toluene as a solvent [101], whereas Nie et al. reported that Ru/C achieved 96% DFF
yield with complete HMF conversion under the conditions of 383 K and 2.0 MPa O 2
in toluene [102]. Other Ru-based catalysts have also gained excellent yield and
selectivity for DFF during the oxidation of HMF [103, 104, 115]. Non-noble metal
catalyst based on V, Co, Cu, and Mn and mixed oxides were also developed for the
oxidation of HMF to DFF [105–112]. Zhang et al. synthesized a vanadium oxide
supported Cu-MOR zeolites (10%V 2 O 5 @Cu-MOR(125)) for the oxidation HMF,
where 91.5% yield for DDF was achieved at 393 K for 7 h in DMSO with
Efficient Nanocomposite Catalysts for Sustainable Production of Biofuels and…