Hydroformylation SILP catalysts

Figure 7.11. Set-up for the continuous, Rh-catalysed propene hydroformylation using an impregnated SILP-catalyst...

TABLE 7.5. Continuous, Rh-catalysed hydroformylation of propene using impregnated SILP-catalysts with different ligands - results at 300 min time on stream... 

The ionic liquid investment could be further reduced if future research enables the application of ammonium based alkylsulfate or arylsulfonate ionic liquids. For these systems bulk prices around 15 /kg are expected. Ammonium based alkylsulfate or arylsulfonate ionic liquids usually show melting points slightly above room temperature but clearly below the operating temperature of the hydroformylation reaction. Therefore these systems may be less suitable for the liquid-liquid biphasic process in which the ionic liquid may be involved in process steps at ambient temperature (e.g. phase separation or liquid storage). In contrast, for the SILP catalyst a room temperature ionic liquid is not necessarily required as long as the film becomes a liquid under the reaction conditions. Assuming an ammonium based SILP catalyst, the capital investment for the ionic liquid for the industrial SILP catalyst would add up to 105,000 . 

A summary of the research activities of the last four years reveals three different important trends (a) The design of new ionic ligands for excellent catalyst immobilisation in ionic liquids and high regioselectivity (b) the successful application of cheap, halogen-free ionic liquids in the biphasic Rh-catalysed hydroformylation (c) the successful development of unusual multiphasic reaction concepts for Rh-catalysed hydroformylation, namely catalysis in ionic liquid/supercritical C02 and SILP-catalysts. 

The use of catalytic SILP materials has been reviewed recently [10] covering Friedel-Crafts reactions [33-37], hydroformylations (Rh-catalyzed) [38], hydrogenation (Rh-catalyzed) [39,40], Heck reactions (Pd-catalyzed) [41], and hydroaminations (Rh-, Pd-, and Zn-catalyzed) [42]. Since then, the SILP concept has been extended to additional catalytic reactions and alternative support materials. In this paper we will present results from continuous, fixed-bed carbonylation and hydroformylation reactions using rhodium-based SILP catalysts as reaction examples demonstrating the advantages of the SILP technology for bulk chemical production. 

To verify the homogeneous nature of Rh-3-SILP catalysts, as previously suggested based on IR and NMR spectroscopic studies, [30] kinetic experiments have also been conducted with the catalyst. Here, a continuous fixed-bed reactor setup equipped with online gas-chromatography, described elsewhere in detail, [31] was applied. The general rate law for the hydroformylation of propene was assumed ... 

Higher alkenes too, liquid at room temperature, can be hydroformylated over a fixed bed SILP catalyst. In this case the carrier gas is scCO . which is soluble in ILs but does not dissolve ionic compounds. For example, 1-octene, CO and H2 are mixed in SCCO2 and flowed through a tubular reactor containing the catalytic system 37 (Figure 40) dissolved in [omim][Tf2N] which, in turn, is supported on silica gel. 

Hydroformylation and Carbonylation Reactions Promoted by SILP Catalysts... 

Butene has been also successfully hydroformylated under these conditions using the SILP catalyst, which exhibited a higher activity and selectivity with respect to propene. 

SILP catalysts are versatile materials that can be also used under standard batch conditions. Thus, allyl alcohol was hydroformylated with a SILP Rh/ PPhs system, affording 80-90% of linear aldehydes with nii up to 31 (Scheme... 

Another SILP catalyst used under batch conditions employed mesoporous MCM-41 as the solid support. The catalyst was derived from [Rh(CO)2(acac)] and TPPTS (1 5 mol ratio) in the desired IL. The excellent catalytic performance of this SILP catalyst in the hydroformylation of C6-C12 linear alkenes (TOF up to 500 h ) was determined by the large surface area and uniform mesopore structure of MCM-41 and was almost independent of the type of IL used [bmim][BF4], [bmim][PF6] and 1,1,3,3-tetramethylguanidinium lactate. 

Fig. 5.3-2 Schematic representation of a supported ionic liquid phase (SILP) catalyst exemplified for a typical rhodium hydroformylation catalyst.

Importantly, it was also realized in these initial studies that the catalysts deactivated in prolonged use with simultaneous decrease in catalytic activity and selectivity, independent of the type of ionic liquid, ionic liquid loading a, and the ligand/rhodium ratio of the system. However, additional studies demonstrated a suitable thermal pre-treatment of the silica support to be necessary to obtain stable SILP catalysts. This technique was applied to prepare Rh-sulfoxantphos catalysts with [BMIMjfn-CsHiyOSOs] and similar systems without ionic liquid. Both systems were compared in 60 h continuous propene hydroformylation reactions using similar conditions as previously reported (Table 5.6-4, entries 11 and 12, Fig. 5.6-8) [93]. 

I Ls can also be immobilized by impregnation of an inorganic support. This is a direct transposition of the Supported Aqueous-Phase Catalysis (SAPC) concept to ionic liquids (see Section 2.6). Supported Ionic Liquid Phase (SILP) catalysts containing Rh-biphosphine ligands were applied to perform continuous-flow gas-phase hydroformylation of propene in [BMIMJIPFg] or [BMIMJIRSOJ (R=octyl). 

Regelein, D. (2005) Hydroformylation of 1 Octene using Supported Ionic Liquid Phase (SILP) Catalysts Diploma Thesis. FAU Erlangen-Nuremherg. 

In a follow-up study, a more detailed NMR investigation of this hydroformylation catalyst was done using liquid HR NMR spectroscopy [13]. For this purpose, both a freshly prepared and a used SILP catalyst were washed with ethanol to remove the IL film. Ethanol was removed in vacuo, and the residue was analyzed by NMR spectroscopy. As side reaction of catalyst formation (4, Scheme 8.2), the sequential... 

IR spectroscopy has proved that SILP catalysts have metalorganic complexes dissolved in the liquid layer, which then worked as a homogeneous catalyst Riisager et al. [12] have made spectroscopic measurements of a rhodirun-sulfoxantphos complex which was immobilized in an SILP system. This SILP catalyst was tested in the continuous-flow fixed-bed hydroformylation of propene. Spectroscopy of the SILP system was performed in situ under conditions closely related to the reaction conditions, that is, imder various gas atmospheres and at 100 °C. The result was that the Rh-sulfoxantphos complex of the SILP catalyst behaved similar to an analogous rhodium-xanthene catalyst dissolved in the homogeneous phase. Analysis of the CO stretching band showed that the catalyst was in equilibrium between a dimeric form and two monomeric forms (Scheme 8.3) and, consequently, that the hydroformylation reactions were indeed homogeneously catalyzed. 

Figure 15.7 Continuous hydroformylation of a technical C4 feed (Raffinate 1, containing 500 ppm (O, C) and less than 16 ppm ( , ) of water) in the presence of Rh-17 SILP catalyst Reaction conditions r = 100 C. = 10 bar, p, = 2 bar.

The examples described above of the successful use of SILP catalysis were aU gas-phase reactions under conditions where no condensation of substrates or products in the gas stream was possible. (Note that capillary condensation inside the porous network of a SILP catalyst might nonetheless occur under certain circumstances.) This is an important prerequisite for effective SILP catalysis as a continuous flow of liquid could remove the thin film of IL from the support (either by dissolution or mechanical displacement), rendering the catalyst inactive in most cases. In case of propene and 1-butene hydroformylation, the formation of the so-caUed heavies 18 and 19 via aldol condensation of the respective aldehyde products (see Scheme 15.3) was reported to reduce the catalyst activity over time, whereas the selectivity remained unchanged [15]. 

In 2007, a SILP-SCCO2 system was first applied to a continuous-flow process by Hintermair et al. [53]. They reported the continuous-flow hydroformylation of 1-octene (Figure 18.8) using a SILP catalyst where a rhodium complex was dissolved in [OMIM][NTf2] (l-octyl-3-mefhylimidazoliumbis(trifluoromethanesulfonamide)) supported on silica by adsorption. The system is shown schematically in Figure 18.8. 

In 2005, Riisager and Wasserscheid [109] linked a Rh(Sulfoxantphos) complex via [BMIM] [n-CgHj yOSOg] on a partly dehydroxylated silica support. In the hydroformylation of propene, a large dependence on the nature of the support and especially the P/Rh ratio was found. Fast deactivation took place at a small excess of the ligand. The stability of the supported ionic liquid phase (SILP) catalyst was directly related to the degradation of the catalytically active complex. 

Interestingly, not only long-chain olefins were meanwhile submitted to SILP systems. Bell and coworkers [113] investigated the hydroformylation of propene using [BMIM] [OctSO J and a Rh(Sulfoxantphos) catalyst. The activity and stability of the rhodium-based SILP catalyst were highly sensitive to its formulation. Dehydration ofthe support at 750 C or removal ofthe silanol groups reduced the... 

SILP catalysts composed of monophosphines (PPha and TPPTS) dissolved in BMI X (X = Pp6 or BF4) on a l-n-butyl-3-[3-(triethoxysilanyl)propyl]imidazolium-modified silica gel support have been prepared and used in rhodiumhexene hydroformylation [39]. The SILP catalysts were found to have higher activity than analogous biphasic systems however, a significant amount of the metal catalyst leached into the product phase at high conversions (rhodium loss of up to 2.1 mol%), because of the depletion of the ionic liquid phase from the support. Importantly, even at lower conversion, pronounced catalyst deactivation was... 

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