Over the past 20 years, thermomorphic multiphase systems (TMS) have been used as a versatile and elegant strategy for the recovery and recycling of homogeneous transition‐metal catalysts, in both batch‐scale experiments and continuously operated processes. TMS ensure a homogeneous reaction in a monophasic reaction mixture at reaction temperature and the recovery of the homogeneous transition‐metal catalyst through liquid–liquid separation at a lower separation temperature. This is achieved by using at least two solvents, which have a highly temperature‐sensitive miscibility gap. The suitability of commercially available solvents makes this approach highly interesting from an industrial point of view. For the first time, herein, all studies in the area of TMS are reviewed, with the aim of providing a concise and integral representation of this approach for homogeneous catalyst recovery. In addition to the discussion of examples from the literature, the thermodynamic fundamentals of the temperature‐dependent miscibility of solvents are also presented. This review also gives key indicators to compare different TMS approaches, for instance. In this way, new solvent combinations and in‐depth research, as well as improvements to existing approaches, can be addressed and promoted.
Long-term applications of cyclodextrins in the aqueous biphasic hydroformylation of higher olefins with high selectivities and simultaneous catalyst recycling.
We present the development of catalytic autotandem reactions into continuous-flow processes on the example of homogeneously catalyzed hydroaminomethylation (consisting of hydroformylation and subsequent reductive amination) as a case study. The synthesis of higher aliphatic amines was successfully operated in a continuous-flow miniplant. Key to success was the development of an integrated catalyst recycling for the homogeneous Rhodium/SulfoXantphos catalyst. With 1-decene and diethylamine as substrates, an average yield of the linear amine of 61% over 60 h of stable process operation was achieved. The catalyst recycling has been accomplished by using a thermomorphic multiphase system (TMS) consisting of methanol and ndodecane, which was rationally established in batch experiments with a methodical approach. This TMS ensured high catalytic activities and facilitated an efficient catalyst separation and recycling. Before application in a continuous process, catalyst recyclability was proven, showing high catalyst activity over six runs with turnover frequencies up to 2400 h −1 .
For the first time, the successful application of the
homogeneously
catalyzed reductive amination in a thermomorphic multiphase system
(TMS) and the first reported scale-up of this reaction into a continuous
process, which recovers and recycles the homogeneous catalyst in flow,
is presented. Herein, the model substrate 1-decanal reacts with the
secondary amine diethylamine to form the corresponding product N,N-diethyldecylamine. A thermomorphic multiphase system
(TMS) is established as a recycling strategy to recover and reuse
the catalyst for the continuous process. After screening different
solvents for the TMS and optimizing the reaction conditions in batch
mode, the recycling of the rhodium catalyst was realized in a fully
automated miniplant. Parameters influencing the stability of the process
were identified and optimized to develop the continuous process. The
process was operated in a steady state over 90 h with yields >90%
of the desired product and low catalyst leaching <1%/h.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.