Zakaria Kaal | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Zakaria Kaal. This seminar is open to the general public to attend.

MSc with Dr. David Bressler.

Thesis Topic: Simultaneous Catalytic Isomerization and Hydrogenation of Alkenes by Al-MCM-41 for the
Production of Sustainable Aviation Fuel from a Lipid Pyrolysis Product

Abstract:

Demand for aviation has been projected to increase considerably in the near and long term future. As a
result of mandates, goals and targets for achieving net-zero emissions for the aviation sector by various
governments and organizations, the demand for a renewable and sustainable aviation fuel is expected to
increase exponentially. The use of hydrogen and noble metal loaded catalysts has been popular in the
synthesis and upgrading of renewable hydrocarbons including sustainable aviation fuel, to increase the
proportion of branched isomers to lower the freezing point of the fuel, and lower the amount of
undesirable alkenes, which can lower the oxidative stability of the fuel.

In this thesis, the use of Al-MCM-41 as a catalyst for isomerizing and hydrogenating model alkenes was
studied in the absence of hydrogen and a noble or transition metal. The conversion of the model
hydrocarbons was studied at various temperatures, and under various gas environments. To understand the
effect of the structure of the alkene on the conversion, experiments were conducted with a 1-alkene and an
internal alkene. A sequential analysis was performed to elucidate the reaction mechanism and
intermediaries. The reaction over the catalyst was then studied on a complex mixture of hydrocarbons, to
understand the conversion in the presence of different hydrocarbon groups, and to observe the effects of
the addition of water and free fatty acids on the reaction.

The upgrading of a lipid pyrolysis product was scaled up from batch microreactors to a continuous flow
through reactor, operating for 12 hours. The product collected was then distilled to yield a jet equivalent
cut, and tested against several specifications set out by the ASTM D1655 standards for aviation turbine
fuel.

The catalyst exhibited no effect on the alkane, but yielded a high conversion of the alkene (58 ± 6% wt.)
in the presence of hydrogen. 31 ± 4% wt. of the liquid product was branc0hed hydrocarbons, and 17 ± 3%
wt. of the liquid product was branched alkanes. The results when the hydrogen was replaced with nitrogen
were statistically the same, indicating that the hydrogenation and isomerization can occur using in situ
hydrogen, generated from the formation of aromatics. The use of a lipid pyrolysis off-gas that contained
some light hydrocarbons showed that some light alkenes can contribute to the reaction. It was observed
that the catalyst, when operating in a complex mix of hydrocarbons, can selectively target the alkenes,
transforming them into both branched and n-alkanes. Free fatty acids were shown to have a strong
inhibitory effect on the catalyst, and water presence in the feed presented a slight decrease in the
isomerization reaction (but not in the hydrogenation of alkenes). Scale up experiments on the lipid
pyrolysis products were successful, exhibiting a product with a similar composition as the batch
experiments. The freezing point of the distilled jet equivalent cut was -56.32 ± 0.04 °C and met all of the
specifications tested, except for the acidity. This was perhaps due to the lipidic nature of the hydrocarbon
source.