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@PHDTHESIS{Engel:659595,
author = {Engel, Rebecca Veronika},
othercontributors = {Palkovits, Regina and Bolm, Carsten},
title = {{H}eterogeneously catalysed amination and isomerisation of
isohexides},
school = {RWTH Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2016-04795},
pages = {1 Online-Ressource (VIII, 141 Seiten) : Illustrationen,
Diagramme},
year = {2016},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen, 2016},
abstract = {A renewable alternative to the depleting fossil resources
is biomass. An important part in the utilisation of biomass
is the conversion and functionalisation of platform
chemicals such as isohexides. Therefore, this work
concentrates on the catalytic valorisation of isohexides,
more precisely isosorbide and isomannide, comprising the
amination and isomerisation. The main products, isohexide
amines and isoidide, respectively, are promising monomers in
the production of biogenic polymers.The direct catalytic
amination of the isohexides using solid catalysts was
investigated, and ruthenium supported on activated carbon
was identified as a suitable catalyst for this
transformation. Despite the hydrothermal and highly basic
conditions, the catalyst showed no significant leaching.
Reversible catalyst deactivation through product adsorption
was detected. Furthermore, a significant variation in the
product distribution depending on the stereochemistry of the
substrates was observed, indicating a preferential amination
of endo-configured hydroxyl groups. Additionally, the role
of hydrogen was investigated in order to clarify, whether
the reaction follows a hydrogen autotransfer mechanism.
Using a heterogeneous ruthenium catalyst, molecular hydrogen
was required, although in low amounts. This hydrogen is most
likely needed for the activation of the catalyst under
reaction conditions and to saturate its surface. The
isohexide isomerisation was investigated in detail, to
obtain a deeper understanding of this reaction. The reaction
mechanism was studied by means of deuterium labelling
experiments with isomannide and dimethyl isosorbide as
substrates. An alternative to the in the literature
discussed dehydrogenation/re-hydrogenation mechanism was
observed: a direct C–H activation. However, it occurs only
at elevated temperatures. Further insights were gained
through kinetic investigations. In this context,
concentration-time profiles were collected at different
temperatures. Interestingly, in the beginning of the
reaction course, an unknown fourth compound was observed.
This substance was produced mainly during the heating phase
of the reaction. First statements about the potential
structure of this compound were made. Additionally, the
kinetic data was modelled. Besides the rate constants, also
the Arrhenius parameters were obtained. The applied solid
catalyst is easy to separate and recyclable. Furthermore,
the amination reaction is conducted at low hydrogen
pressures and in aqueous solution. Therefore, the reported
reaction is a benign route towards biogenic isohexide
amines. These new insights into the isohexide isomerisation
reaction provide a foundation for further process
development for the production of isoidide. Altogether,
first steps towards the production of these biomass-derived
alternative monomers were taken.},
cin = {155310 / 150000},
ddc = {540},
cid = {$I:(DE-82)155310_20140620$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-rwth-2016-047950},
url = {https://publications.rwth-aachen.de/record/659595},
}
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