Process Design and Optimization for the Hydroformylation of Long-chain Alkenes

The substitution of current feedstock with renewable resources is a major challenge in today’s chemical process industries. To focus more specifically on this research area, the Collaborative Research Center SFB/TR63 – Integrated Chemical Processes in Liquid Multiphase Systems (InPROMPT) of the Deutsche Forschungsgemeinschaft (DFG) was conceived. The main emphasis of this collaboration is the development of process structures for homogeneously catalyzed reactions in liquid multiphase systems.

As part of this effort, we primarily focus on the development of optimal reactor concepts for liquid multiphase systems, in particular for the rhodium-catalyzed hydroformylation of long-chain olefins. The main challenge of this process is the quantitative recovery of the rhodium catalyst and equally important ligands. To this end, thermomorphic solvent systems (TMS) are used which allow for temperature induced phase splitting in the post-reaction mixture [1]. The catalyst rich phase is recycled to the reactor and the product rich phase is treated further downstream. Applying a multi-scale design approach, the molecular design of the solvent system directly influences all other process units. This leads to an overall process design task that combines both the solvent and reactor optimizations as part of an integrated process optimization problem.

This is no simple task and this presentation focuses on our recent achievements and methods used towards reaching this goal. As an expansion to the single-stage separation TMS, an extraction cascade was proposed to further reduce catalyst leaching and increase the domain of acceptable TMS solvents [2]. This prompted the development of several strategies for TMS solvent design [3] with an emphasis on not only process performance but also considering ecological characteristics [4]. Frequent liquid-liquid equilibrium (LLE) calculations during optimization are numerically challenging and in order to simplify the optimization of the resulting process flowsheets, several different surrogate models representing the LLE and catalyst partitioning were implemented [2,5]. On the reaction side, The use of the EPF methodology [6] allows us to identify reactor concepts, such as a cyclic semi-batch or helically coiled tubular reactor, that lead to better reaction performance than when using conventional arrangements [7,8]. The various tools and strategies being devised in this project will hopefully enable us to develop new processes based around complex homogeneously catalyzed multiphase reactions, such as for the hydroformylation of long-chain olefins, as part of a single, integrated design step.