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14 CAtALYsIs
elements35 Issue 2|2011
Robust and selective:
metathesis catalysts for
oleochemical applications
Metathesis plays a key role in oleochemistry to make renewable resources
usable for the chemical industry. The metathesis catalysts used for this
purpose must be robust and highly active to convert the raw material
qualities, which are subject to frequent fluctuations and occasional contamination.
The Evonik portfolio features two catalysts, catMETium® RF2
and catMETium® RF3, that can solve this difficult task.
[ text Dr. Renat Kadyrov ]
MetAtHesIs Is A chemical reaction in which four
atoms receive new bonding affiliates in a single step.
Depending on the sub strate combination, it is distinguished
between ring-closing metathesis (RCM),
cross-metathesis (CM) and ring-opening metathesis
polymerization (ROMP). The development of well
defined catalytic systems for metathesis reactions
won the Nobel Prize in Chemistry in 2005.
Today, metathesis is a highly significant method
of the chemical industry, for instance in the development
and production of modern plastics or of active
pharmaceutical ingedients (fig. 1). Ring-closing metathesis
is an elegant method for construction of macrocyclic
ring systems and therefore is an indispensable
reaction step in the synthesis of modern active pharmaceutical
ingredients for the treatment of hepatitis
C or cancer. Ring-opening metathesis polymerization
is an effective method to produce specialty polymers
for large, complex and corrosion-resistant components
for automotive applications or chemical containers.
In oleochemistry, metathesis reactions are
used for functionalizing unsaturated fatty acid derivatives.
Evonik markets metathesis catalysts under the
name of catMETium® RF (fig. 2). All catalysts are
based on unsaturated N-heterocyclic carbene Ru
complexes (Ru-NHC). The catalysts all share the
characteristics of high temperature stability, high
turn-over numbers (TON), and high selectivity.
The metathesis of olefins plays a particularly important
role in oleochemistry, since this technology
allows for direct access to renewable resources and
for their efficient use without creating any by-products.
For example, metathesis turns triglycerides and
unsaturated fatty acid derivatives (from palm, soy,
canola or sunflower oil) into fine chemicals, functionalized
monomers, polymers, biodegradable lubricants
and specialty chemicals such as cosmetics.
Cross metathesis of unsaturated fatty acids and
acid esters with functionalized olefins, allow for accessing
a diversity of double-functionalized olefins.
These represent interesting raw materials for creating
macrocyclical compounds, polyesters, polyamides,
lubricants or surfactants for example. On the
other hand, the non-functional olefins that are generated
in the same process can be further converted to
α-olefins, oil field chemicals, lubricant additives and
waxes.
Highly prized robustness and stability
at high temperatures
Metathesis catalysts for oleochemistry applications
must have special properties for operating economically.
catMETium® RF2 and catMETium® RF3 meet
these requirements. They stand out for high tolerance
for a variety of raw material qualities, fulfill ing an
essential prerequisite for the use of renewable resources
in oleochemistry.
The thermal stability of catMETium® RF catalysts
represents another advantage, which is especially important
in equilibrium-limited cross-metathesis
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