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Metathesis Catalysts for Oleochemical Applications New Metathesis Catalysts with High Temperature Stability and Selectivity

Editor: Marion Henig

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. New catalysts can solve this difficult task.

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Metathesis catalysts must be robust and highly active to convert the raw material qualities, which are subject to frequent fluctuations and occasional contamination. (Picture: Evonik Industries)
Metathesis catalysts must be robust and highly active to convert the raw material qualities, which are subject to frequent fluctuations and occasional contamination. (Picture: Evonik Industries)

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. 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.

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Highly Prized Robustness and Stability at High Temperatures

Metathesis catalysts for oleochemistry applications must have special properties for operating economically. The Evonik portfolio features catalysts which meet these requirements (fig. 2 shows the accordant product family). These metathesis 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 thermal stability represents another advantage, which is especially important in equilibrium-limited cross-metathesis or homo-metathesis. The high thermal stability of the catalysts allows for combining the catalytic metathesis step with thermal separation and to return non-converted starting materials to the process.

The high thermal stability of the catalysts is evident in the homo metathesis of methyl oleate, in which octadec-9-ene and dimethyl-9-octadec-9-ene-1, 18-dioate are obtained in an equilibrium reaction (fig. 3). While saturated Ru-NHC complexes quickly degrade at temperatures just above 70 °C and therefore produce a wide range of by-products, the catalysts show unparalleled thermal stability and robustness, even at temperatures

above 100 °C.

As a result, reaction speed and productivity significantly increase at high temperature (fig. 4). Even at high reaction temperatures, a turnover number of > 200,000 with a selectivity of > 98 percent is achievable. With an integrated thermal separation of the products, the reaction equilibrium can be shifted toward higher volumes and yields without the risk of destroying the catalyst by thermal stress.

License Agreements Are Superfluous

In addition to these specs, Evonik offers further added value with a clear, independent IP position that is also reflected in the business model. Evonik uses a simple proven business model to market the catalysts that makes license agreements superfluous and allows for transparency. The total kilogram price for the catalysts includes all license fees for the use of intellectual property; customers have no further obligations. This business model is also reflected in the product name, since the acronym RF stands for Royalty Free (fig. 2). This allows customers to make use of the new catalysts without any restrictions.

* The Author deals with synthesis, up-scaling and production of homogeneous catalysts at the Catalysts Business Line of Evonik Industries.

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