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This work shows the versatility of Raney Ni under different conditions and systems, many
answers about the behavior of Raney Ni are given here, making this work a significant base for
studies or applications of Raney Ni in chemical processes.
The reactions using the model compounds from lignin show how each group is converted
differently by Raney Ni helping to understand the catalytic upgrading process. Some functional
groups are converted easily, e.g. ether bonds, simple phenols, ketones and allylic bonds. For
guaiacol and aldehyde groups, longer reaction times and higher active Raney Ni
is required
for
significant conversion. These differences between singles model compounds illustrate the
heterogeneity of natural lignin, clarifying the challenge to upgrade natural feedstock.
The system Raney Ni and 2-propanol
present
outstanding results applied to the biorefining
process through several runs. The partial deactivation of Raney Ni after catalyzing the biorefining
process, which is detected using the model compounds from lignin as probe molecules, is not
strong being easily
reversed
under a new and uncomplicated regeneration process developed here.
A simple heating process in 2-propanol
is able to
regenerate Raney
Ni, this
new catalyst presents
the best results regarding the quality of model compounds upgrade. The Raney Ni properties also
Raney Ni stability and characterization upon different systems and solvents change during these
processes, the changes are shown by the characterizations. The increase in
the particle size and oxidation of the surface species are the strongest changes observed.
The new approach using a sustainable and renewable feedstock, limonene, is presented for
the production of
p-cymene. The new process has high conversion and selectivity towards the
p-cymene
production. These results are superior to the traditional method used nowadays in industry.
Raney Ni employed in this process in the presence of acetone/2-propanol retains the activity and
the product distribution for several runs, proving to be
a competitive process. Also the characterizations showed
how the acetone interacts and affects Raney Ni, leaching aluminum,
removing the hydrogen, breaking the domain particles and reducing the magnetic properties.
During the biorefining and
the model compound
reactions, the characterizations have
shown
the influence of the biorefining process on the material. An organic film is deposited on the
surface and subsequently removed after the regeneration process. However, the most interesting
are
the comparison of the processes using 2-propanol and acetone. Although both solvents have
shown
high quality
results in each process, 2-propanol has a protective and regenerative nature
instead of a degenerative character like acetone.
In addition,
monitoring reactions
to investigate the impact of the different
solvents used to
store of Raney Ni as
a function
of time and hydrogen storage show how different functionalities
develop different characteristics in the Raney Ni. Keto groups lead to a quick removal of the
hydrogen content. Water remains the H-storage even after prolonged storage periods but favors the
oxidation of the catalyst. Still, alcohols are the most appropriate solvents to store Raney Ni and
Raney Ni stability and characterization upon different systems and solvents
keep the H-content, presenting a promotion in the activity in the first hours and as the carbon chain
grows.
