170
8 Biocrude Oil Valorization
The production of high-quality fuel containing specific types of hydrocarbons relies
on the valorization or upgrading of the biocrude oil obtained from the HTL of algae
biomass. As mentioned in the previous section, the upgrade of biocrude oil uses
heterogeneous catalysts. Most of the time, HTL of the algae biomass is carried out
uncatalyzed followed by catalyzed upgrading of the biocrude oil. Upgrading ensures
the conversion of oxygenates into hydrocarbons [45]. Zeolite is the most widely
used heterogeneous catalyst for upgrading biocrude oil because of its unique structure and acidity [117, 132, 133]. The body of research on zeolite has been considerably applied to pyrolysis [134–136]. The valorization process removes O in the
intermediate products through a combination of processes such as cracking, decarboxylation, and decarbonylation. Typical temperatures range between 300 and
500 °C [107, 131, 137]. The suitable choice of zeolite is critical for the following
reasons. First, it affects the composition of the gaseous phase (e.g., alkanes, CO 2 ,
Table 2 Summary of catalyst, microalgae species, experimental conditions, and biocrude oil yield
for catalytic hydrothermal liquefaction (HTL) of microalgae
Catalyst
Microalgae
Temp (°C), time
(min)
Yield
(wt%)
Ref
Ru/C
Nannochloropsis sp.
350, 60
+43
Duan and Savage
[41]
Pd/Al 2 O 3
Pd/C
Pd/C
Chlorella pyrenoidosa
Chlorella pyrenoidosa
Nannochloropsis sp.
280, 30
280, 30
350, 60
+8
+4
+63
Yu et al. [99]
Yu et al. [99]
Duan and Savage
[41]
Pt/Al 2 O 3
Pt/C
Pt/Al 2 O 3
Pt/C
Nannochloropsis oc.
Nannochloropsis sp.
Chlorella pyrenoidosa
Chlorella pyrenoidosa
350, 60
350, 60
280, 30
280, 30
−12
+34
+7
+6
Biller et al. [31]
Duan and Savage
[41]
Yu et al. [99]
Yu et al. [99]
NiO
Spirulina platensis
350, 60
−23
Jena and Das [73]
Ni/Al 2 O 3
Nannochloropsis oc.
350, 60
−47
Biller et al. [31]
Ni/SiO 2 -Al 2 O 3 Nannochloropsis sp.
350, 60
+44
Duan and Savage
[41]
Raney-Ni
Chlorella pyrenoidosa 280, 30
+12
Yu et al. [99]
Ni-Mo/Al 2 O 3 Nannochloropsis
Salina
340, 30
+41
Li et al. [86]
Co-Mo/Al 2 O 3 Nannochloropsis oc.
350, 60
−26
Biller et al. [31]
Co-Mo/γ- -
Al 2 O 3
Nannochloropsis sp.
350, 60
+54
Duan and Savage
[41]
Zeolite
Nannochloropsis sp.
350, 60
+29
Duan and Savage
[41]
HZSM-5
Chlorella pyrenoidosa 300, 20
+3
Xu et al. [126]
Ce/HZSM-5
Chlorella pyrenoidosa 300, 20
+47
Xu et al. [126]
Ca 3 (PO 4 ) 2
Spirulina platensis
350, 60
−12
Jena and Das [73]
E. P. Resurreccion and S. Kumar
8 Biocrude Oil Valorization
The production of high-quality fuel containing specific types of hydrocarbons relies
on the valorization or upgrading of the biocrude oil obtained from the HTL of algae
biomass. As mentioned in the previous section, the upgrade of biocrude oil uses
heterogeneous catalysts. Most of the time, HTL of the algae biomass is carried out
uncatalyzed followed by catalyzed upgrading of the biocrude oil. Upgrading ensures
the conversion of oxygenates into hydrocarbons [45]. Zeolite is the most widely
used heterogeneous catalyst for upgrading biocrude oil because of its unique structure and acidity [117, 132, 133]. The body of research on zeolite has been considerably applied to pyrolysis [134–136]. The valorization process removes O in the
intermediate products through a combination of processes such as cracking, decarboxylation, and decarbonylation. Typical temperatures range between 300 and
500 °C [107, 131, 137]. The suitable choice of zeolite is critical for the following
reasons. First, it affects the composition of the gaseous phase (e.g., alkanes, CO 2 ,
Table 2 Summary of catalyst, microalgae species, experimental conditions, and biocrude oil yield
for catalytic hydrothermal liquefaction (HTL) of microalgae
Catalyst
Microalgae
Temp (°C), time
(min)
Yield
(wt%)
Ref
Ru/C
Nannochloropsis sp.
350, 60
+43
Duan and Savage
[41]
Pd/Al 2 O 3
Pd/C
Pd/C
Chlorella pyrenoidosa
Chlorella pyrenoidosa
Nannochloropsis sp.
280, 30
280, 30
350, 60
+8
+4
+63
Yu et al. [99]
Yu et al. [99]
Duan and Savage
[41]
Pt/Al 2 O 3
Pt/C
Pt/Al 2 O 3
Pt/C
Nannochloropsis oc.
Nannochloropsis sp.
Chlorella pyrenoidosa
Chlorella pyrenoidosa
350, 60
350, 60
280, 30
280, 30
−12
+34
+7
+6
Biller et al. [31]
Duan and Savage
[41]
Yu et al. [99]
Yu et al. [99]
NiO
Spirulina platensis
350, 60
−23
Jena and Das [73]
Ni/Al 2 O 3
Nannochloropsis oc.
350, 60
−47
Biller et al. [31]
Ni/SiO 2 -Al 2 O 3 Nannochloropsis sp.
350, 60
+44
Duan and Savage
[41]
Raney-Ni
Chlorella pyrenoidosa 280, 30
+12
Yu et al. [99]
Ni-Mo/Al 2 O 3 Nannochloropsis
Salina
340, 30
+41
Li et al. [86]
Co-Mo/Al 2 O 3 Nannochloropsis oc.
350, 60
−26
Biller et al. [31]
Co-Mo/γ- -
Al 2 O 3
Nannochloropsis sp.
350, 60
+54
Duan and Savage
[41]
Zeolite
Nannochloropsis sp.
350, 60
+29
Duan and Savage
[41]
HZSM-5
Chlorella pyrenoidosa 300, 20
+3
Xu et al. [126]
Ce/HZSM-5
Chlorella pyrenoidosa 300, 20
+47
Xu et al. [126]
Ca 3 (PO 4 ) 2
Spirulina platensis
350, 60
−12
Jena and Das [73]
E. P. Resurreccion and S. Kumar