First iridium-catalyzed hydroformylation in a continuously operated miniplant

As demand for the scarce element rhodium continues to grow, the need to apply alternative metals in homogeneous catalyzed hydroformylation is becoming even more essential. Initial results at laboratory scale emphasized the high potential of, e.g., iridium -based catalysts for further investigations. However, the real suitability of iridium catalysts can only be determined by conducting long-term experiments in continuous operation. As such, a highly flexible, continuously operated miniplant in which a variety of alternative transition metals can be applied was designed. Following the initial miniplant start-up and optimization, the first scale-up of the iridium/phosphine-catalyzed hydroformylation of 1-octene into continuous plant operation succeeded. An efficient catalyst recycling concept via extraction was implemented, resulting in a very low catalyst leaching for both iridium and phosphorus (0.1%/h) and a steady state plant operation over 90 h. These results showed favorable long-term iridium catalyst activity and stability, which led to conversion and aldehyde chemoselectivity rates of approximately 85%. In further experiments, key parameters such as CO/H-2 ratio or reaction temperature were investigated to further optimize the catalytic performance. In addition to 1-octene, other substrates, such as 1-pentene, where applied successfully, too, which demonstrated the high flexibility and performance of iridium catalysts at a continuous scale and underscored the high potential or further use in industrial applications. (C) 2016 Elsevier Ltd. All rights reserved.