Unlocking the potential of supported liquid phase catalysts with supercritical fluids: low temperature continuous flow catalysis with integrated product separation

Abstract

Solution-phase catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of homogeneous catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow homogeneous catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.

Ionic‐Liquid‐Functionalized UiO‐66 Framework: An Experimental and Theoretical Study on the Cycloaddition of CO2 and Epoxides

“…Moreover, cyclic carbonates have received extensive attention as solvents in Li-ion batteries, as monomers forp olymer synthesis, and their utility in the productiono fp olyurethanes, chemical products, and fuel additives. [28][29][30][31][32][33][34][35][36][37] In the liquid-phase reactions, leaching of the IL reduces the reactivity and stability of the material. [26,27] Over the past decades, many supported IL-phase( SILP) heterogeneousc atalysts with silicag els, SiO 2 / Al 2 O 3 ,a ctivated carbon,T iO 2 ,a nd mesoporous silica as porous support materials have been reported for various catalytic reactions.…”

“…[26,27] Over the past decades, many supported IL-phase( SILP) heterogeneousc atalysts with silicag els, SiO 2 / Al 2 O 3 ,a ctivated carbon,T iO 2 ,a nd mesoporous silica as porous support materials have been reported for various catalytic reactions. [28][29][30][31][32][33][34][35][36][37] In the liquid-phase reactions, leaching of the IL reduces the reactivity and stability of the material. Therefore, several approaches have been established for the synthesis of efficient IL-based poroush eterogeneousc atalysts.…”

Life cycle assessment of novel supercritical methyl propionate process with carbon dioxide feedstock

“…Moreover, the employment of a water scavenger or a perfluoroalkyl-functionalized silica substrate has demonstrated an improvement in the stability of the employed catalyst (140 000 TON). 24 However, such engineering issues linked to product purification and catalyst recovery are likely to supersede the value of the final product. 24 Continuous-flow systems could be a solution to that with both their steadystate homogeneous turnover in a stationary liquid phase and efficient integrated product separation.…”

“…24 However, such engineering issues linked to product purification and catalyst recovery are likely to supersede the value of the final product. 24 Continuous-flow systems could be a solution to that with both their steadystate homogeneous turnover in a stationary liquid phase and efficient integrated product separation. Also for this reason, this paper considers that kind of operation.…”

Homogeneous Catalyst Recycling and Separation of a Multicomponent Mixture Using Organic Solvent Nanofiltration

“…Many efforts have been invested in new ways to make the recyclability of homogeneous catalysts easier. One approach was to change the catalyst, e.g., by immobilization . Other approaches focused on the development of new methods which would allow the separation of the catalyst from the reaction mixture , .…”