Thermomorphic Multiphase Systems: Switchable Solvent Mixtures for the Recovery of Homogeneous Catalysts in Batch and Flow Processes

Abstract

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.

Facile catalyst recycling by thermomorphic behaviour avoiding organic solvents: a reactive ionic liquid in the homogeneous Pd-catalysed telomerisation of the renewable β-myrcene

“…In combination with β-farnesene, it was assumed by Vorholt et al that dimcarb follows the principles of a thermomorphic multiphase system (TMS) with alkenes. 32 This system is defined by the fact that two liquid phases form a monophasic system at a specific critical temperature. If this mixture falls below or exceeds the critical temperature again, spontaneous phase separation occurs.…”

Improvement of Productivity for Aqueous Biphasic Hydroformylation of Methyl 10‐Undecenoate: A Detailed Phase Investigation

“…For these experiments, the TOF after different reaction times (15,20, and 30 min) and the STY after 1 hour of reaction time were calculated with respect to the initial substrate concentration in order to assess the productivity of the process (Figure 7).…”

“…The TOF was calculated for full conversion. Aim was to create a water-based thermomorphic multiphase system (TMS) [15] in which a homogeneous reaction system occurs at reaction temperature and the catalyst separation follows after cooling down the reaction system. The used mixture with 1-butanol (46 wt%), water (46 wt%), and M10U (8 wt%) did not form a monophasic system at reaction temperature.…”

Continuous hydroformylation of 1-decene in an aqueous biphasic system enabled by methylated cyclodextrins

“…4 Other approaches have been developed in both industry and academia to tackle the main issue of catalyst separation from the product by using rhodium catalysts. Examples of these are the use of supercritical CO 2 (scCO 2 ), 5 CO 2 -expanded liquid (CXL), 6,7 supported ionic liquid phase (SILP), 7 organic solvent nanofiltration (OSN), 8 thermomorphic multiphase systems (TMS), 9 microemulsions, 10 or biphasic systems. 11 Some of them use abundant resources (such as carbon dioxide and the environmentally friendly solvent, water), but others do not.…”