Combining Partial Hydrogenation of Soybean‐Derived Biodiesel and Methoxycarbonylation Using a Single Palladium Source

ABSTRACT Valorization of soybean‐derived biodiesel through an integrated tandem one‐pot approach was examined. Recent studies have indicated the necessity of pretreating unsaturated fatty acid methyl esters (FAMEs) to remove polyunsaturated FAME (PU‐FAME), due to their inhibitory effect on various homogeneous catalyzed reactions. The first step in the process under investigation involves the selective partial hydrogenation of PU‐FAME towards monounsaturated FAME (MU‐FAME), catalyzed by palladium nanoparticles in methanol. This is followed by the Pd/1,2‐bis[(di‐ tert ‐butylphosphino)methyl]benzene (1,2‐DTBPMB)‐catalyzed isomerizing methoxycarbonylation (iMC) of MU‐FAME, resulting in a linear C 19 ‐diester. Utilizing the protonated derivative of the 1,2‐DTBPMB ligand for the iMC, the Pd nanoparticles employed in the hydrogenation step function as a catalyst precursor. The combination of both reactions in a tandem one‐pot approach would eliminate the need for a work‐up, thereby streamlining the process. However, the process is hindered by several challenges arising from the contrary optimal operating conditions for both reactions, such as the selection of solvent, the amount of catalyst, and the presence of the accompanying gas in the reaction mixture. These aspects have been thoroughly examined in this study, leading to the development of an optimized reaction workflow. Utilizing this method, the partial hydrogenation of soybean FAME is achieved with conversions of 95%–98%, followed by the in situ formation of the homogeneous catalyst and the iMC, yielding a linear C 19 ‐diester with a selectivity of 98%. Practical Applications : This study proposes a novel integrated tandem one‐pot approach for the selective partial hydrogenation of vegetable FAME to MU‐FAME, followed by the homogeneously catalyzed iMC. The integration of Pd nanoparticles as both a catalyst for hydrogenation and as a precursor for the formation of a homogeneous catalyst utilized in iMC ensures the efficient utilization of the metal throughout the whole reaction sequence. The method integrates the necessary pretreatment with sequential functionalization under optimized conditions.