Hydroformylations of higher olefins

Our approach is to use the inexpensive ligands that are already used industrially as well as conventional solvents. The goal of this project is to develop a thermomorphic approach to the rhodium-catalyzed hydroformylation of higher olefins (>Ce) that enhances conversion rates and ease of product recovery while minimizing catalyst degradation and loss. 

The consequence of low alkene solubihty is in that industrially the RCH-RP process can be used only for the hydroformylation of C2-C4 olefins. In all other cases the overah production rate becomes unacceptably low. This is what makes the hydroformylation of higher olefins one of the central problems in aqueous/organic biphasic catalysis. Many solutions to this problem have been suggested (some of them will be discussed below), however, any procedure which increases the mutual solubihty of the organic components and the aqueous ingredients (co-solvents, surfactants) may... 

Hydroformylation of higher olefins provide long chain alcohols which find use mainly as plasticizers. No aqueous/organic biphasic process is operated yet for this reaction, for several reasons. First, solubility of higher olefins is too small to achieve reasonable reaction rates without applying special additives (co-solvents, detergents, etc.) or other means (e.g. 

The studies listed in Table 4.5 illustrate the practical realization of the above principles. Not surprisingly, research into the use of surfactants is directed mainly to the hydroformylation of higher olefins, which show negligibly small solubility in water. Four main approaches are clearly distinguishable (but not always separable) ... 

In conclusion it can be said, that micellar effects offer useful possibilities to tune the reactivity and separation characteristics of aqueous/organic biphasic hydroformylations. Nevertheless, the added sensitivity of the systems to small changes in process variables and the added cost of surfactants and/or specially synthetized ligands have to be justified by high added value products or on grounds of process cost savings. Whether this will happen on industrial scale (perhaps in the hydroformylation of higher olefins) remains to be seen. 

Thermoregulated Phase Transfer Catalysis - A conceptual advance in the field of biphasic hydroformylation of higher olefins is the use of rhodium catalysts generated from nonionic tenside phosphines, such as ethoxylated tris(4-... 

Figure 5 Flow diagram of the Union Carbide Process for hydroformylation of higher olefins catalysed by Rhltppms in a single phase with biphasic catalyst separation.

The aqueous biphasic processes require a minimum solubility of the reactants S in the catalyst phase [196, 205]. Therefore, hydroformylation of higher olefins (approx. > Cg) or functionally substituted olefins is more difficult but offers various advantages, such as the simplification of reaction sequences and reduced expenditure for the catalyst cycle. So far, work on these biphasic processes for the conversion of higher olefins, except for Kuraray s recent devel-... 

According to Horvath, the problems arising from the limited reciprocal solubilities of the water phase and higher olefins should be overcome by application of the SAPC technique [138, 144]. For this and other biphasic - but nonaqueous -processes, see Sections 3.1.1.2 and 3.1.1.3. A new concept concerning inner lipophilic cavities and hydrophilic surfaces of a-cyclodextrins may offer new possibilities for the hydroformylation of higher olefins [142]. Asymmetric hydro-formylations are dealt with in Section 2.9. 

First of all, these properties were used to separate the sulfonated phosphine from the excess of sulfuric acid affer sulfonation by forming a triisooctylammo-nium salt in toluene, which is totally insoluble in water [1], Later it was discovered, that the re-immobilized ligand in toluene as well as the immobilized ligand in water are useful and remarkably stable catalyst systems. As classical homogeneous catalysts they are very active, e. g., for the hydroformylation of higher olefins and olefins with internal double bonds. 

A systematic investigation of surfactants during the hydroformylation of higher olefins catalyzed by water-soluble Rh/TPPTS complexes (cf. Section 3.1.1.1), was conducted by Chen et al. [25]. The authors found that only cationic amphiphiles gave a significant effect on the yield and a moderate influence on the n/i ratio. 

Methylated cyclodextrins promote the hydroformylation of higher olefins, too. Molecular dynamics simulations show that the reaction takes place right at the interface and that cyclodextrins act as both surfactants and receptors that favour the meeting of the catalyst and the olefin. The methylated cyclodextrin adopts specific amphiphilic orientations at the interface, with the wide rim pointing towards the water phase. This orientation makes easier the formation of inclusion complexes with the reactant (1-decene), the key reaction intermediate [Rh(H)CO(TPPTS)2-decene)] and the reaction product (undecanal). ... 

Using RuCl(CO)(TPPTS)(BISBIS) the biphasic aqueous hydroformylation of higher olefins in the presence of the cationic surfactant CTAB ensures a TOF > 700 h and regioselectivity >96% for the linear aldehyde Piperazinium cationic surfactants were also successfully applied as catalysis promotion agents in the aq. biphasic hydroformylation of higher olefins. The property of surfactant and ligand can be assumed by the same molecule, e.g. di-sulfonated cetyl(diphenyl)phosphine 42. 1-Dodecene is hydroformylated in water/toluene (3 1) under mild conditions [olefin/Ru = 2500, CO/H2=1, P(CO + H2) = 15 bar, 42/Ru = 10] with TOF = 188 Another approach to... 

Unfortunately, the rhodium/sulfonated phosphine catalyst showed very low catalytic activities in the hydroformylation of higher olefins such as 1-octene in... 

If the reactants and reaction products have polarities which are very different from that of water, special measures have to be taken in order to be able to continue to employ a two-phase process using water as solvent. This is the case in the hydroformylation of higher olefins (> C5). The fall in the solubility in water associated with an increasing number of carbon atoms in the olefins used (and also in the resulting aldehydes) leads to a pronounced decrease in the reactivity (cf. Fig. 4). 

Table 4. Examples of proposed measures for improving the hydroformylation of higher olefins ...

In the hydroformylation of higher olefins, even using the aqueous biphasic method, it has to be assumed that, owing to the reduction in the reaction rate caused by decreasing solubility of the olefins, the actual reaction should be single phase and the separation should be two phase. From today s point of view, this leaves the following routes to a solution ... 

The development of thermoregulating ligands might well make a decisive contribution to solving the problems of aqueous, homogeneously catalyzed hydroformylations of higher olefins. 

In aqueous two-phase hydroformylation of 1-octene and 1-dodecene the amphiphilic ligands of type 25 (n = 10, 12) have been shown to form Rh catalysts that are superior to Rh/TPPTS systems [129]. The bicyclic ligands 26 were considered to be of interest as substitutes for TPPMS in the new oxo process developed by Union Carbide for the hydroformylation of higher olefins using N-methylpyrroli-done or polyalkylene glycols as solvents [7, 51, 52], Rh(I) complexes [Rh(26)2]+ [96] showed, however, a very poor performance as catalysts in biphasic systems for hydrogenation and hydroformylations in contrast to non-functionalized 1-phospha-norbornadiene [98], This was explained by formation of P,P(0) chelates blocking... 

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