The Catalyst Review July 2024 - 14

Experimental Abstracts
Production of Biofuels from Hydrodeoxygenation and Hydroisomerization of
Triglycerides with Metal-Supported SAPO-11 Molecular Sieves
Biofuels are currently considered to be viable alternatives to petroleum-based fuels. They are readily produced by the hydroprocessing
of fats and oils-a process which involves a complex sequence of reactors and unit operations. Herein, the authors describe a onestep
conversion of triglycerides to isomerized renewable hydrocarbons using non-sulfided metal-loaded silico-aluminophosphates-11
(SAPO-11) molecular sieves. The effect of different metals on catalytic performance was evaluated in terms of conversion of triglycerides,
yield to hydrocarbons (naphtha, kerosene, diesel, and heavy fractions), and isomerization activity. The highest yield of liquid hydrocarbons
(73.1%) was obtained using a nickel-based SAPO-11 with an 8% metal loading.
Using the wetness impregnation method, these workers used
nanosized SAPO-11 as a support, which was then loaded with
different noble (Pd, Pt) and transition metals (Ni, Cu). Numerous
techniques, including ICP-OES, X-ray fluorescence spectroscopy,
SEM, and TEM characterized the resulting bifunctional catalysts.
These studies showed no pore size distribution alteration was
found after impregnation. However, using metal nitrate precursors
seems to slightly improve mesoporosity compared to acidic metal
chlorides. Likewise, different metal-support interactions and,
consequently, different metal particle sizes affect the pore size due
to the blocking of micro- and mesochannels and pore filling, thus
decreasing the specific surface area and pore volume.
Studies were then carried out to measure the effect of the different
metals on the catalytic performance for the conversion of a
triglyceride (palm oil) to hydrocarbons (naphtha, kerosene, diesel
and heavy fractions) as well as isomerization activity (Scheme 1).
The reactions were carried out in an isothermal stirred tank reactor,
which resulted in the complete removal of oxygen for each of
Scheme 1. Reaction Pathways of Triglycerides by the Hydrotreatment Process
the catalysts tested. However, long reaction times were required to
achieve total deoxygenation (Scheme 2). Middle distillates (jet fuel
and diesel fractions) were targeted as desired reaction products.
The yield to kero and diesel fractions varied between 30 and 40%,
with the 8% Ni/SAPO-11 being the most effective catalyst in terms
of cracking ability. Furthermore, 5% Ni/SAPO-11 and 8% Ni/SAPO11
exhibited the maximum selectivity to isoalkanes (ratio of iso-tonormal
alkanes equal to 0.82 and 0.92, respectively). A relatively high
content of a 365°C + fraction was detected in all cases, suggesting
that the high residence time required to reach full deoxygenation and
the high temperature favored the thermal oligomerization pathways
at the expense of the desired HDO/hydroisomerization reactions.
Differences among catalysts were found in terms of coke formation.
Elemental carbon analysis revealed that the highest coke deposition
was found using 8% Ni/SAPO-11 and 8% Cu/SAPO-11 catalysts.
Torres-Bujalance V, Prieto CA, Rodriguez Espinoza KE, et al. (2024).
Energy Fuels, https://doi.org/10.1021/acs.energyfuels.3c04992
Scheme 2. Condensation and Thermocatalytic Cracking of Triglycerides
14
The Catalyst Review
July 2024

https://www.doi.org/10.1021/acs.energyfuels.3c04992

The Catalyst Review July 2024

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