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