Selective Product Crystallization for Concurrent Product Separation and Catalyst Recycling in the Isomerizing Methoxycarbonylation of Methyl Oleate

• Published in: ACS sustainable chemistry & engineering 2020-07, Vol.8 (29), p.10633-10638, Article acssuschemeng.0c03432
• Main Authors: Herrmann, Norman, Köhnke, Katrin, Seidensticker, Thomas
• Format: Article
• Language: English
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.0c03432

Selective product crystallization proved to be a very attractive recycling strategy for homogeneous catalysts. This approach was demonstrated for the Pd-catalyzed isomerizing methoxycarbonylation of the renewable oleochemical methyl oleate using technical-grade starting material. The corresponding product, dimethyl-1,19-nonadecanedioate, is a valuable linear platform chemical for biobased polycondensates. A pure product phase (>96%) was produced by selectively controlled cooling crystallization following the reaction, whereas at the same time, the superior chemo- and regioselectivity of the known catalyst system was not compromised. The use of auxiliaries was avoided entirely; only the deliberate exploitation of the solubility behavior of the desired product led to success. The homogeneous Pd catalyst remained in the used methanol and was successfully recycled in up to eight repetitive batch runs. More than 39 g of linear C19 diester were isolated with an average selectivity in the methoxycarbonylation of 88%. The literature-known productivity of the Pd catalyst, expressed as its turnover number, was thus more than 6-fold increased from typically 400 to >2800. For compounds having suitable solubility behavior, selective product crystallization, therefore, complements the toolbox of available recycling techniques for homogeneous catalysts. The complete elimination of auxiliaries, the production of a pure product phase, and the possible use of commercial catalyst systems are some of the particularly sustainable features of this approach.