Supported, ionic liquid-phase

Rhodium Catalysed Hydroformylation Using Supported Ionic Liquid Phase SILP) Catalysis... 

The term Supported Ionic Liquid Phase (SILP) catalysis has recently been introduced into the literature to describe the heterogenisation of a homogeneous catalyst system by confining an ionic liquid solution of catalytically active complexes on a solid support [68], In comparison to the conventional liquid-liquid biphasic catalysis in organic-ionic liquid mixtures, the concept of SILP-catalysis offers very efficient use of the ionic liquid. Figure 7.10 exemplifies the concept for the Rh-catalysed hydroformylation. 

Figure 7.10. Supported ionic liquid phase (SILP) catalysis exemplified for the Rh-catalysed hydroformylation reaction...

Supported aqueous phase (Chapter 3, Section 3.6, Chapter 5, Section 5.2.5) and supported ionic liquid phase catalysts, Chapter 7, Section 7.3) are probably not suitable for use with higher alkenes because the liquid feed slowly dissolves some of the water or ionic liquid changing the nature of the catalyst and leading to catalyst leaching. 

A rather new concept for biphasic reactions with ionic liquids is the supported ionic liquid phase (SILP) concept [115]. The SILP catalyst consists of a dissolved homogeneous catalyst in ionic liquid, which covers a highly porous support material (Fig. 41.13). Based on the surface area of the solid support and the amount of the ionic liquid medium, an average ionic liquid layer thickness of between 2 and 10 A can be estimated. This means that the mass transfer limitations in the fluid/ionic liquid system are greatly reduced. Furthermore, the amount of ionic liquid required in these systems is very small, and the reaction can be carried in classical fixed-bed reactors. 

A major step towards applicability of multiphase catalysis in ionic liquids is the development of Supported Ionic Liquid Phase (SLIP) -catalysis by the Wasserscheid group [28,29]. The SLIP concept enables quasi-heterogeneous catalysis in ionic liquids and opens the door to the production of basic chemicals. 

Fig.1 Schematic presentation of supported ionic Liquid Phase (SILP) catalyst...

SILP hydroformylation catalysts were prepared by dissolving appropriate amounts of Rh(CO)2 (acac) and ligand in dried methanol followed by stirring for 30 min. Afterwards, the ionic liquid was added to the solution. After stirring for another 30 min, the support was added and the solution stirred for 60 min. Finally, the methanol was removed in vacuo and a pale red powder was obtained. The supported ionic liquid-phase catalyst was stored imder argon for further use. 

Table 6 Stirred batch reactor ARO of epoxides catalyzed by a dimeric (R,R)-Cr(III)(salen) complex 65 immobilized in a supported ionic liquid phase compared to the dimeric complex impregnated on silica 64-silica and the reported homogeneous reactions with the monomeric Cr(salen) complex 63...

The catalyst/substrate ratio is 1.5 mol% for the supported ionic liquid phase (SILP) catalyst, 3 mol% for the impregnated catalyst and 2 mol% for the homogeneous reaction aRuns 1 -4 are consecutive experiments with the same catalyst in a stirred batch reactor. bDimeric Cr (salen) catalyst impregnated on silica cHomogeneous reaction at 0-2 OC optimized for product selectivity dHomogeneous reaction at room temperature optimized for product selectivity... 

Hintermair, U. and Zhao, G. and Santini, C.C. and Muldoon, M.J. and Cole-Hamilton, D.J. (2007). Supported ionic liquid phase catalysis with supercritical flow. Chem. Commun., 14, 1462-1464. 

The first fixed-bed application of a supported ionic liquid-phase catalyst was hydroformylation of propylene, with the reactants concentrated in the gas phase (265). The catalyst was a rhodium-sulfoxantphos complex in two ionic liquids on a silica support. The supported ionic liquid phase catalysts were conveniently prepared by impregnation of a silica gel with Rh(acac)(CO) and ligands in a mixture of methanol and ionic liquids, [BMIMJPFg and [BMIM][h-C8Hi70S03], under an argon atmosphere. 

An area in which functionalised ionic liquids are already playing an important role in catalysis is heterogenisation on solid supports. The general concept involves the immobilisation of imidazolium and other cationic fragments onto solid supports using appropriate functional groups attached to the cation. An ionic catalyst then resides within the ionic matrix and several examples of such supported ionic liquid phase catalysts are provided in the subsequent chapters of this book. The concept is illustrated in Figure... 

Silica-supported ionic liquid-phase (SILP) catalysis has been developed as an alternative approach to address the problem of product isolation, a methodology well known from aqueous catalysis, and an overview of SILP-hydroformylation reactions in ionic liquids is given in Table 4.4.[631... 

Table 4.4 Supported ionic liquid phase hydroformylation in ionic liquids...

Figure 4.6 Silica-supported ionic liquid phase hydroformylation...

C jimlfPFe] Pd(OAc)2 Pd(PPh3)4 Et3N k2co3 100-150 °C. Supported ionic liquid phase catalysis (SILP) with silica as solid phase catalyst relatively stable for at least 5 runs product decanted and solid phase washed with hexane less than 0.24% catalyst loss. [87]... 

Another method used for recycling TSOSs consists in using the so-called supported ionic liquid phase (SILP) [44-49], The general principle is using an OS with a trialkoxysilane moiety that can be grafted covalently to a particle of silica. The particle, now coated with onium salt, has a special affinity for other onium salts, especially ILs. ILs can therefore get immobilized on a solid particle and subsequently be used for immobilizing other reagents (transition metal complexes, proline, etc.). This method has recently been reviewed and employs mostly non-functional ILs, so it won t be explained in more detail [44-49] (Fig. 17). 

Keywords Heterogeneous catalysis, biphasic catalysis, ionic liquids, task-specific ionic liquids, supported ionic liquid phases... 

Supported Ionic Liquids Phases for Catalytic Applications... 

It must be also noted that supported ionic liquid phase (SILP) catalysis can also be successfully combined with supercritical fluids. Cole-Hamilton et al. [127] have reported recently high activity (rates up to 800 h ), stable performances (>40 h) and minimum rhodium leaching (0.5 ppm) in the hydroformylation of 1-octene using a system that involves flowing the substrate, reacting gases and products dissolved in... 

Figure 2.13 Examples of three concepts of catalysis in supported ionic liquids (a) hydroformylation catalysis [121] (b) methanol carbonylation [122] (c) supported ionic liquid phase catalysis combined with SCCO2 [127].

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