Comparing Separation vs. Fresh Start to Assess Reusability of Pd/C Catalyst in Liquid‐Phase Hydrogenation

The reusability of metal catalysts is a key issue for the potential application of new catalysts in research and industrial practice. The most common procedure for testing catalyst reusability in liquid‐phase heterogeneous reactions is based on separating a catalyst from a reaction mixture followed by the next run. An alternative procedure called “fresh start” consists of the addition of a new portion of reagents to the reaction mixture without any isolation operation. In this work, we compare both procedures in a model Pd/C‐catalyzed hydrogenation with different heteroatoms, e. g., O‐, S‐, and N‐vinyl derivatives. It was shown that regardless of whether the catalyst is stable or potentially poisoned during the reaction, both procedures lead to comparable results. It appears that a much easier implementation of a fresh start procedure may be an option of choice. The possibilities of using both procedures to rationalize the experimental protocol for assessing Pd/C catalyst reusability in liquid‐phase hydrogenations are discussed. A fresh start! Catalyst reusability in liquid‐phase reactions is usually tested by catalyst separation from a reaction mixture followed by the next run. Another procedure called “fresh start” consists of adding a new portion of reagents to the reaction mixture without catalyst separation. In the present work, these procedures were compared in testing the reusability of Pd/C catalysts in liquid‐phase hydrogenations of O‐, S‐, and N‐vinyl derivatives.