Critical Literature Review on the Hydrothermal Conversion of Vegetable Oil to Jet Fuel Range Alkanes

Literature review 1
CRITICAL LITERATURE REVIEW ON THE HYDROTHERMAL CONVERSION OF
VEGETABLE OIL TO JET FUEL RANGE ALKANES
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Literature review 2
Hydrolysis
Hydrolysis has been significantly adopted in the attempt to obtain fatty acids from the
vegetable oil. To ensure the accessibility and availability of cellulose, the best performance
recommendation is carbonic acid and alkaline extraction. The carbon dioxide and sulphuric
acid is always added in order to limit the production of inhibitors as well as improvement of
the hemicellulose (Wang et al., 2015). This is contrary to the use of a steam explosion, as it
does not completely break down the lignin carbohydrate mixture. By extension, numerous
strategies have been investigated to aimed at detoxification of lignocellulose hydrolysates,
and the best approach with promising results is the hydrolysis of myco-LB. this assists in
total sugar recovery and also prevent the fermentation inhibitors. A number of methods,
operational conditions as well as catalysts have proved to offer the optimum grounds for the
process f extraction of free fatty acids from the vegetable oils. The batch mode proved to
offer the best yield results when hydrolysis is analysed. For instance, due to the constant
volume within the reactor, the reaction time was similar for all reactants. It indicated more
complete reactions with minimal degradation of the by-products. Lipase has been used as
biocatalysts (triacylglycerol hydrolase, EC 3.1.1.3.) (Choi et al., 2018). This enzyme not only
catalyses the hydrolysis process but as well the esterification process, as well as the creation
of the link between alcohol carboxyl and hydroxyl groups of the carbolic groups. This
property makes them have a wider application in the biotechnological field. The superiority
which they have over other catalysts is that they are readily available, and in terms of
handling, they require no complexity (Li et al., 2010). Additionally, they do not necessitate
for coenzymes, with a high level of tolerance to organic solvents and are as well stable. The
diagram below indicates the yield obtained by different researchers. The optimum conditions
for the hydrolysis process, according to the enzyme utilised is the temperature of 25.53
degrees Celsius, and ph. of 6.86 (Wang and Tao, 2016).

Literature review 3
Deoxygenation
Peng et al conducted numerous investigations on the deoxygenation of fatty acids for the
production of biofuel. The researchers utilised different catalyst, at a constant temperature of
300-degree Celcius. These catalysts include Ni, Rh, Pt, Ir, and Ru. Ni-Raney, PdPt/C, and
Os/C; and 1, 5, and 10% by weight Pd/C. Pd/C as a catalyst was found to be the most active
through the deoxygenation of stearic acid (Peng et al., 2012). On the other hand, Choi and
colleagues conduct an investigation to determine the possibilities of obtaining alkanes
without hydrogen addition. They utilised a catalyst based on W/Pt/TiO2 , which yielded 86%
of the catalytic deoxygenation reaction.
In terms of the mode in which the deoxygenation experiment is conducted, both the batch and
continuous modes can be applied. A continuous reactor system having unreacted acid cycle
can be used to improve the yield of the expected alkene through minimizing the time and
exposure of the alkene within the high-temperature reactor. In this way, the small
hydrocarbons and carbon dioxide can be recovered. The continuous mode proves to bet the
best for the deoxygenation process, as it can be optimised to regulate the reactions
temperatures as well as maximizing the product composition and yield (Li et al., 2015).
In similar research, the author acknowledges the high requirement for hydrogen on the
deoxygenation process and thus offers a suggestion to an experiment with least use of
hydrogen consumption-selective deoxygenation (Hollak et al., 2014). The authors note that
the most active catalyst for the process is the bi-functional catalysts which comprise of a
combination of active metal phase as well as oxophilicity. One significant advantage is that
with limited use of hydrogen in the process, the stability of the process and the entire process
activity is improved. Hence, a recommendation in the utilisation of internally available
hydrogen in the biofuel.

Literature review 4
In another study: catalytic Conversion of Palm Oil to Bio-Hydrogenated Diesel over Novel
N-Doped Activated Carbon, an advanced n-doped Pt-carbon catalyst is used in the
deoxygenation process. The optimal choice if the temperature is 300-degree Celsius with
high pressures (Santillan‐Jimenez and Crocker, 2012). The catalyst demonstrates superiority,
with relation to the Pt/AC material since it is not associated with deactivation signs nor
carbon deposition.
Cracking
Thermal cracking which was utilised earlier on proves Ineffective due to the high cooking
potential of the highly oxygenated bio-crudes which are currently generated. Hence, the need
for catalytic cracking, and specifically hydrocracking which entails the utilisation of
hydrogen in the cracking process (Wu et al., 2017). The various catalysts used for the process
include synthetic zeolites, amorphous silica-alumina and natural clay materials. In particular,
Adijaye and Bakshi, utilised a synthetic zeolite ZSM-5 at a temperature of 330-410 degrees
Celcius and atmospheric pressure. Notably, hydrogen was not utilised and from a comparison
of similar experiments using a different catalyst (silicalite, H-mordenite, HZSM-5 and silica-
alumina), the optimum yields were realised with H-Y and H- modernite at 370 degrees
Celsius. A comparison of catalytic and thermal cracking done by Gevert and Otterstedt
showed positive yield for thermal cracking at 500 degrees Celsius with high sensitivity
(Cheng et al., 2014).
In another study by Zhang et al., a hierarchical SBUY-MCM-41 catalyst was developed
through a hydrothermal technique (2016). Thereafter, an investigation of the cracking of the
hydrocarbon fuels from vegetable cooking oil was investigated over the catalyst. The catalyst
demonstrated a high acidity as well as thermal stability. When this catalyst was compared to
microporous USY zeolite and mesoporous Al-MCM-41, NiMo/SBUY-MCM-41 catalyst
improved the cracking of the jet-fuel range with 37.3 per cent, as well as highest selectivity

Literature review 5
for the c10-c14 hydrocarbon formations and 7.6% aromatics. This was then related to the acid
distribution and hierarchical structure of the NiMo/SBUY-MCM-41 catalyst. The whole
experiment was conducted in the batch mode (Rabaev et al., 2015).

Literature review 6
References
Cheng, J., Li, T., Huang, R., Zhou, J. and Cen, K., 2014. Optimizing catalysis conditions to
decrease aromatic hydrocarbons and increase alkanes for improving jet biofuel
quality. Bioresource technology, 158, pp.378-382.
Choi, I.H., Lee, J.S., Kim, C.U., Kim, T.W., Lee, K.Y. and Hwang, K.R., 2018. Production of
bio-jet fuel range alkanes from catalytic deoxygenation of Jatropha fatty acids on a
WOx/Pt/TiO2 catalyst. Fuel, 215, pp.675-685.
Hollak, S.A., Ariëns, M.A., de Jong, K.P. and van Es, D.S., 2014. Hydrothermal
deoxygenation of triglycerides over Pd/C aided by in situ hydrogen production from glycerol
reforming. ChemSusChem, 7(4), pp.1057-1062.
Li, L., Coppola, E., Rine, J., Miller, J.L. and Walker, D., 2010. Catalytic hydrothermal
conversion of triglycerides to non-ester biofuels. Energy & Fuels, 24(2), pp.1305-1315.
Li, T., Cheng, J., Huang, R., Zhou, J. and Cen, K., 2015. Conversion of waste cooking oil to
jet biofuel with nickel-based mesoporous zeolite Y catalyst. Bioresource technology, 197,
pp.289-294.
Peng, B., Yao, Y., Zhao, C. and Lercher, J.A., 2012. Towards quantitative conversion of
microalgae oil to diesel‐range alkanes with bifunctional catalysts. Angewandte Chemie
International Edition, 51(9), pp.2072-2075.
Rabaev, M., Landau, M.V., Vidruk-Nehemya, R., Koukouliev, V., Zarchin, R. and
Herskowitz, M., 2015. Conversion of vegetable oils on Pt/Al2O3/SAPO-11 to diesel and jet
fuels containing aromatics. Fuel, 161, pp.287-294.
Santillan‐Jimenez, E. and Crocker, M., 2012. Catalytic deoxygenation of fatty acids and their
derivatives to hydrocarbon fuels via decarboxylation/decarbonylation. Journal of Chemical
Technology & Biotechnology, 87(8), pp.1041-1050.

Literature review 7
Wang, J., Bi, P., Zhang, Y., Xue, H., Jiang, P., Wu, X., Liu, J., Wang, T. and Li, Q., 2015.
Preparation of jet fuel range hydrocarbons by catalytic transformation of bio-oil derived from
fast pyrolysis of straw stalk. Energy, 86, pp.488-499.
Wang, W.C. and Tao, L., 2016. Bio-jet fuel conversion technologies. Renewable and
Sustainable Energy Reviews, 53, pp.801-822.
Wu, X., Jiang, P., Jin, F., Liu, J., Zhang, Y., Zhu, L., Xia, T., Shao, K., Wang, T. and Li, Q.,
2017. Production of jet fuel range biofuels by catalytic transformation of triglycerides based
oils. Fuel, 188, pp.205-211.
Zhang, X., Lei, H., Zhu, L., Qian, M., Zhu, X., Wu, J. and Chen, S., 2016. Enhancement of
jet fuel range alkanes from co-feeding of lignocellulosic biomass with plastics via tandem
catalytic conversions. Applied Energy, 173, pp.418-430.