Selective Product Separation by Inert Gassing Crystallization for Efficient Recycling of Homogeneous Catalysts

The development of new processes based on renewable resources plays an important role in the chemical industry. By means of homogeneous catalysis, oleo-chemicals from natural fats and oils can be efficiently transferred to polymer pre-stages. For the downstream separation of product and catalyst, the selective product crystallization represents a promising separation method - to maintain the usually expensive organometallic catalyst at the typically moderate operating conditions in an active state for an efficient recycling, and simultaneously obtain a pure product without further purification steps. Therefore, based on the example methoxycarbonylation reaction of methyl 10-undecenoate towards linear 1,12-dimethyl dodecanedioate (l-C12-DME), in this thesis the selective product crystallization with downstream filtration and washing was investigated and optimized for integrated catalyst recycling. First, a laboratory set-up for crystallization, filtration, and washing under inert atmosphere was developed for maintaining activity of the oxygen-sensitive catalyst. Starting from a simplified binary reference system l-C12-DME/methanol, inert gassing crystallization was established to gain control over the crystallization process, improving product quality regarding a narrow particle size distribution and reduced agglomeration level for an efficient separation in the subsequent filtration and washing steps. Next, this concept was transferred to crystallization from real reaction mixtures, focusing the impact of impurities in the reaction mixture on contamination in the crystalline product. Finally, in an integrated catalyst recycling study, a successful recycling of active catalyst and simultaneous isolation of pure l-C12-DME (> 99.9 %) was achieved.