Hydroformylation of lower olefins

Ethylene (C2), propene (C3), and butane (C4) are usually referred to as the lower olefins. Their solubihty in the aqueous phase is high enough to ensure reaction rate without phase-transfer additives. In the following, we will mainly introduce the appHcation of aqueous-organic biphasic catalysis in the hydroformylation of 

Our group studied ethylene hydroformylation catalyzed by HRh(CO)(TPPTS)3 in an aqueous-organic biphasic catalytic system, and successfully applied it in the industrial productionin Nanjing, China. The current capacity is 20 000 tons per year. 

The industrial process showed high activity turnover frequency (TOF 1043 h ) and high selectivity (98%) for propionaldehyde, as well as the very low loss of catalyst in organic layer at 65 °C and 1.8 MPa. Moreover, it also showed excellent advantage in the separation of propionaldehyde from the catalyst in aqueous phase. 

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Following the recommendations of Manassen [18] the history of biphasic hydroformylation began with work on various water-soluble ligands (Table 1). After this preparatory work on various aspects [30], Kuntz [22, 199] expressed the basic idea of a new generation of water-soluble oxo catalysts with triphenyl-phosphine trisulfonate (TPPT S, as the Na salt, as compared with TPPMS and TPPDS, the mono- and disulfonate) as ligands for a Rh-based oxo process, mainly for the hydroformylation of lower olefins such as propene (eq. (5)). 

The lack of data is obvious and surprising at a time when the Ruhrchemie/ Rhone-Poulenc process has been in operation for more than 20 years. A rigid reaction rate model, established under idealized conditions, becomes complex and complicated when it is transferred to the hydroformylation of lower olefins under conditions relevant to the industrial practice, as the mass transfer phenomena involved in a triphasic system (gas-liquid-liquid) in large reactors have to be taken... 

The concept of TRPTC provides a reasonable explanation for the satisfactory catalytic reactivity of Rh/nonionic phosphine complexes in the case of the two-phase hydroformylation of higher olefins. At a temperature lower than the cloud point, a nonionic phosphine-modified rhodium catalyst would remain in the aqueous phase since the partition of the catalyst between water and a nonpolar aprotic organic solvent strongly favors the aqueous phase. On heating to a temperature higher than the cloud point, however, the catalyst loses its hydrate shell, transfers into the organic phase and then catalyzes the transformation of alkenes to aide-... 

The most important point is the complete separation of the catalyst and the products. The Union Carbide process proposal for the hydroformylation of higher olefins solves this problem [36, 37]. The catalyst leaching is lower than 20 ppb of... 

The first example of application of a chiral early-late heterobimetallic complex in asymmetric catalysis was reported by Bomer in 1999 and deals with hydroformylation of activated olefins (Scheme 39) [122]. The chiral bimetallic complex 66 was generated in situ by reacting the (R,R)-Diph-salenophos-Ti(0 Pr)2 ligand (67) with [Rh(acac)(CO)2]. This complex gives rise to a diminished conversion in aldehyde (21 % vs 99%) as well as a lower selectivity (i n = 77/23 vs 99/1) with respect to the monometallic salenophos-Rh complex generated in situ from the free-metal ligand 68 and [Rh(acac)(CO)2] but affords the branched aldehyde with 30% ee. 

Conventional triorganophosphite ligands, such as triphenylphosphite, form highly active hydroformylation catalysts (95—99) however, they suffer from poor durabiUty because of decomposition. Diorganophosphite-modified rhodium catalysts (94,100,101), have overcome this stabiUty deficiency and provide a low pressure, rhodium catalyzed process for the hydroformylation of low reactivity olefins, thus making lower cost amyl alcohols from butenes readily accessible. The new diorganophosphite-modified rhodium catalysts increase hydroformylation rates by more than 100 times and provide selectivities not available with standard phosphine catalysts. For example, hydroformylation of 2-butene with l,l -biphenyl-2,2 -diyl... 

In the case of aqueous multiphasic catalytic conversions, the reaction rate can be strongly affected by the ability of the substrate to move over into the catalyst phase. For biphasic hydroformylation, the velocity decreases with increasing chain length of the olefins due to their lower solubility in the aqueous phase [78]. 

With increasing concentration of methylated /1-cyclodextrin the selectivity to n-nonanal increases from 64% to 72%, while the conversion of the olefin is constantly as high as 97%. Obviously the addition of the methylated /i-cyclodextrin has only a moderate influence on the isomerizing hydroformylation of trans-4-octene to n-nonanal. The addition of only 0.2 mol.-% of methylated /3-cyclodextrin lowers the isomerization rate which results in the formation of slightly more branched aldehydes. In pharmacy j6-cyclodextrins are established as solvation mediators between polar and less polar solvents. This is one possible explanation for the rise in selectivity to n-nonanal with an increasing j6-cyclodextrin concentration. At higher con-... 

The only other olefin feedstock which is hydroformylated in an aqueous/organic biphasic system is a mixture of butenes and butanes called raffinate-II [8,61,62]. This low-pressure hydroformylation is very much like the RCH-RP process for the production of butyraldehyde and uses the same catalyst. Since butenes have lower solubility in water than propene, satisfactory reaction rates are obtained only with increased catalyst concentrations. Otherwise the process parameters are similar (Scheme 4.3), so much that hydroformylation of raffinate-11 or propene can even be carried out in the same unit by slight adjustment of operating parameters. 

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