651
for aldol condensation of FUR and acetone was reported by Li et al. [135]. The
physicochemical properties of cerous phosphate were greatly influenced by the different crystal structures, which are played an important role on catalyst performance. The distribution of different crystal structures can be varied by tuning the
synthesis condition (hydrothermal synthesis temperature) and pretreatment conditions (calcination temperature). The increase in calcination temperature to 900 °C
of cerous phosphate catalyst with monoclinic crystal structure increases the catalytic performance for condensation reaction due to the presence of the higher
amount of acid sites and relatively stable textural properties. However, opposite
trend was observed for cerous phosphate catalyst with hexagonal crystal structure.
The FUR conversion and aldol product yield increased to 96% and 68.4% (C 8 :54.3,
C 13 :14.1), respectively, for cerous phosphate with the monoclinic structure after calcination at 900 °C.
Yang et al. reported the solvent-free synthesis of diesel and jet fuel range alkanes
by aldol condensation of 2-pentanone and 2-heptanone followed by HDO of condensation product [136]. Various solid base catalysts were employed for the condensation reaction, and the activity sequence of these catalysts is
CaO > MgAl-HT > KF/Al 2 O 3 > CoAl-HT > MgO–ZrO 2 > MgO. The higher activity
of CaO (98.3% conversion, 86.7% yield) was due to the stronger basicity of the
material. Ao et al. performed aldol condensation reaction of FUR and cyclopentanone to produce C 15 (2,5-bis(furan-2-ylmethylidene)cyclopentan-1-one) fuel precursor with high yield [137]. Various HT-based mixed oxide catalysts (Mg-Zr,
Mg-Al, and Co-Al) and KF/Al 2 O 3 were studied for the condensation reaction. It was
demonstrated that KF/Al 2 O 3 exhibits superior performance compared to HT-based
catalysts because of the presence of strong basic sites, which were generated by
strong interaction of KF salt with the support. The authors have studied the condensation reaction using various solvents and demonstrated their effect on the targeted
product solubility and yield. It was reported that the targeted product was highly
soluble in THF, and product yield was about 98%. However, cost of solvent and
environmental aspect (green process) should be considered as other important
parameters while choosing the appropriate solvent. Chen et al. demonstrated the
two-step synthesis process of C 9 –C 10 branched alkanes by aldol condensation of
FUR and 3-pentanone and 5-nonanone and followed by hydrodeoxygenation of
condensation product [138]. 5-Nonanone is less reactive than the 3-pentanone
because of the greater steric effect of alkyl group of 5-nonanone. Different types of
solid base catalysts such as MgO, CaO, MgO-ZrO 2 , MgO-La 2 O 3 , MgAl hydrotalcite, LiAl hydrotalcite, and KF/Al 2 O 3 were employed for the condensation reaction. Among these catalysts, CaO and KF/Al 2 O 3 catalysts showed higher activity in
aldol condensation of FUR and 3-pentanone. The authors have used different SiO 2 -
supported monometallic and bimetallic catalysts for HDO of aldol condensation
products to produce jet fuel range branched alkanes (Fig. 11). Ni-Cu/SiO 2 catalyst
showed superior HDO activity compared to other catalysts.
Recently pure and modified zeolites and metal organic frameworks (MOFs) have
been studied for aldol condensation of FUR. Zeolites are reusable heterogeneous
catalysts of high stability, surface area, and activity. Pure zeolites of different
Efficient Nanocomposite Catalysts for Sustainable Production of Biofuels and…
for aldol condensation of FUR and acetone was reported by Li et al. [135]. The
physicochemical properties of cerous phosphate were greatly influenced by the different crystal structures, which are played an important role on catalyst performance. The distribution of different crystal structures can be varied by tuning the
synthesis condition (hydrothermal synthesis temperature) and pretreatment conditions (calcination temperature). The increase in calcination temperature to 900 °C
of cerous phosphate catalyst with monoclinic crystal structure increases the catalytic performance for condensation reaction due to the presence of the higher
amount of acid sites and relatively stable textural properties. However, opposite
trend was observed for cerous phosphate catalyst with hexagonal crystal structure.
The FUR conversion and aldol product yield increased to 96% and 68.4% (C 8 :54.3,
C 13 :14.1), respectively, for cerous phosphate with the monoclinic structure after calcination at 900 °C.
Yang et al. reported the solvent-free synthesis of diesel and jet fuel range alkanes
by aldol condensation of 2-pentanone and 2-heptanone followed by HDO of condensation product [136]. Various solid base catalysts were employed for the condensation reaction, and the activity sequence of these catalysts is
CaO > MgAl-HT > KF/Al 2 O 3 > CoAl-HT > MgO–ZrO 2 > MgO. The higher activity
of CaO (98.3% conversion, 86.7% yield) was due to the stronger basicity of the
material. Ao et al. performed aldol condensation reaction of FUR and cyclopentanone to produce C 15 (2,5-bis(furan-2-ylmethylidene)cyclopentan-1-one) fuel precursor with high yield [137]. Various HT-based mixed oxide catalysts (Mg-Zr,
Mg-Al, and Co-Al) and KF/Al 2 O 3 were studied for the condensation reaction. It was
demonstrated that KF/Al 2 O 3 exhibits superior performance compared to HT-based
catalysts because of the presence of strong basic sites, which were generated by
strong interaction of KF salt with the support. The authors have studied the condensation reaction using various solvents and demonstrated their effect on the targeted
product solubility and yield. It was reported that the targeted product was highly
soluble in THF, and product yield was about 98%. However, cost of solvent and
environmental aspect (green process) should be considered as other important
parameters while choosing the appropriate solvent. Chen et al. demonstrated the
two-step synthesis process of C 9 –C 10 branched alkanes by aldol condensation of
FUR and 3-pentanone and 5-nonanone and followed by hydrodeoxygenation of
condensation product [138]. 5-Nonanone is less reactive than the 3-pentanone
because of the greater steric effect of alkyl group of 5-nonanone. Different types of
solid base catalysts such as MgO, CaO, MgO-ZrO 2 , MgO-La 2 O 3 , MgAl hydrotalcite, LiAl hydrotalcite, and KF/Al 2 O 3 were employed for the condensation reaction. Among these catalysts, CaO and KF/Al 2 O 3 catalysts showed higher activity in
aldol condensation of FUR and 3-pentanone. The authors have used different SiO 2 -
supported monometallic and bimetallic catalysts for HDO of aldol condensation
products to produce jet fuel range branched alkanes (Fig. 11). Ni-Cu/SiO 2 catalyst
showed superior HDO activity compared to other catalysts.
Recently pure and modified zeolites and metal organic frameworks (MOFs) have
been studied for aldol condensation of FUR. Zeolites are reusable heterogeneous
catalysts of high stability, surface area, and activity. Pure zeolites of different
Efficient Nanocomposite Catalysts for Sustainable Production of Biofuels and…