2024/06/28 by Duch, Karsten, Kozachynskyi, Volodymyr, Porthun, Linus +2
#500 Naturwissenschaften und Mathematik::540 Chemie::540 Chemie und zugeordnete Wissenschaften #catalysts #lipids #mixtures #phase separation #surfactants
paper · doi:10.14279/depositonce-20601
The development of sustainable industrial processes according to the 12 principles of green chemistry poses challenges, such as the use of atom-efficient catalysis, the application of green solvents, the use of mild process conditions, and the retention of valuable catalysts in the process. One way to combine these desired but partially opposing aspects into a single reaction system is the use of homogeneous catalysis in microemulsions, where the catalyst is solubilized in water and brought into intensive contact with organic substrates through a surfactant. The valuable transition metal catalyst can then be recovered through a simple phase separation after the reaction. The key challenge addressed in this work is the implementation of reductive amination (RA) as an example of a complex synthesis route for fine chemicals in a continuous production process using a microemulsion system. The investigated reaction network includes equilibrium, subsequent, and side reactions, which make it challenging to implement in a stable mini-plant operation. A proof of concept for continuous operation in a mini-plant is achieved in a 200 h continuous operation by applying our previously developed structured workflow for the design and operation of reactive processes in liquid multiphase systems to the RA. At 25 bar and 110 °C with a residence time of 6 h, an undecanal conversion of (59.9 ± 3.4)% is achieved, which matches the performance from lab-scale investigations and thus proves a successful scale up by a factor of 68. Stable phase separation is maintained for 200 h, where only 0.12% of the rhodium catalyst entering the settler is leached into the product phase and 99.88% is recycled to the reactor in active form. These results are further proof that continuous and robust operation of homogeneous catalysis in microemulsions with excellent catalyst retention is possible and that previously developed workflows for the design and operation of mini-plants are applicable. Reactions in microemulsions have thus reached technology readiness level 5 and are ready for industrial-scale demonstration.