Nonaqueous hydroformylation

Liu et al. [18] investigated the possibility of catalyst recycling in the nonaqueous hydroformylation of 1-decene by using the thermomorphic polyether phosphite 2a described earlier under phase-transfer conditions. Catalyst recovery with the procedure of phase-separable catalysis was possible with 0.92% rhodium loss in the seventh cycle. Complete olefin conversion and aldehyde yields of 98% were reached, but linear and branched aldehydes were formed in almost equal amounts. 

X0 reaction is thus recovered as the reboiler heat source. This is a great advantage over the classical (nonaqueous) hydroformylation, which simply discards parts of the oxo reaction heat. The RCH/RP process is a net steam exporter. In the case of the above-mentioned Oxeno developments the large catalyst flow is said to serve as a heat transfer medium itself, thus making the process nearly isothermal. ... 

Polyether phosphites with over 19 ethylene glycol units were used as ligands in the rhodium-catalyzed nonaqueous hydroformylation of 1-decene. The catalysts were recovered by precipitation from the reaction mixture after reaction on cooling to room temperature or lower. The precipitated catalysts could be reused up to six times without any decrease in activity. In situ formed polyetherphosphite/Ru3(CO)i2 catalyst was found to be active in hydroformylation of 1 -decene in n-heptane solution atl30°Cand50bar[20]. 

Water soluble Rh/tppts and Rh/tppms complexes dissolved in nonaqueous media such as the ionic liquids, l-ethyl-3-methylimidazolium or l-n-butyl-3-methylimidazolium salt have also been used as catalysts in the hydroformylation of 1-pentene employing a two phase system.15,16 The yields obtained were 16-33% (TOF=59-103 h 1) without any leaching of the rhodium from the ionic liquid to the aldehydes/feedstock phase. Rh/PPh3 catalysts exhibited higher rates (TOF=333 h 1) for the same biphasic reaction albeit with leaching of rhodium due to the uncharged nature of the catalytic system.15... 

On the industrial level, aqueous two-phase systems are used more often than nonaqueous two-phase systems. The Kuraray Co. operates a pilot plant for the hydrodimerization of 1,3-butadiene in a two-phase system with a Pd/tppms catalyst (140). The reaction is carried out in sulfolane-water, from which the products, the octadienols, separate. The final products can be octanol or nonanediol made by subsequent isomerization and hydroformylation. The capacity of the Kuraray process is about 5000 tons/year. 

Quite a number of contributions to ligand research in oxo chemistry are known (e.g., [16, 17, 23, 37, 38, 46, 49, 79, 80, 96, 113-119, 153]), as well as those in respect of other central atoms, binuclear complexes, photosensitized hydroformylations, or other starting olefins, including bioorganometallic applications (e.g., [38, 116, 120-123, 145, 146, 151]). The substitution of Na by Li, K or other cations in TPPTS-derived or other processes is claimed to be advantageous (e.g., [124, 125]). According to some observations [126] the kinetics of hydroformylations in aqueous phase may be different from those in nonaqueous media, as suspected by Chaudhari and co-workers [127]. Special aspects, mainly the behavior, control, and organization of the phases of aqueous biphasic processes, are dealt with in special papers [31, 41, 128, 129]. 

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. 

When the alkali-metal cation of a sulfonated phosphine or phosphite is replaced by ammonium ion it is possible to devise applications in nonaqueous solvents. Al-kylammonium salts of TPPTS were reported in the first patents of Kuntz [5] and catalytic examples were given in which water alone was the solvent. More recently Fell et al. prepared a series of sulfonated phosphites including the example shown below, 1 [6], and examined these in a variety of solvents for the hydroformylation of tetradecene. Catalytic results are reported with acetone and acetophenone as the... 

Non-aqueous approaches toward two-phase hydroformylation have been demonstrated by Horvath et al. [16] with the use of a fluorous biphasic system containing a rhodium catalyst bearing partially fluorinated ponytail ligands, and Olivier and Chauvin [17] with TPPMS and TPPTS dissolved in nonaqueous ionic liquids (see Sections 7.2 and 7.3). 

In order to overcome this limitation, the elegant concept of biphasic catalysis for hydroformylation reaction was further extended to media other than water [8]. The identity of this ideal second phase is far from obvious as very few solvents present chemical and physical properties in accordance with the hydroformylation requirements. Without giving a complete list, one can cite perfluorinated solvents [9] (see Chapter 4), supercritical fluids [10] (see Chapter 6), and nonaqueous ILs [11]. At... 

The concept of fluorous biphase hydroformylation of heavy olefins was introduced by Horvath at Exxon in 1994 [42, 43]. Fluorocarbon-based solvents, especially perfluorinated alkanes and ethers, are of modest cost, chemically inert, and nonpolar and show low intermolecular forces. Most of them are immiscible with water and can be therefore used as the nonaqueous phase. Moreover, their miscibility with organic solvents such as toluene, THF, or alcohols at room temperature is quite low. Only at elevated temperature miscibility occurs. These features allow hydroformylation at smooth reaction conditions at 60-120 °C in a homogeneous system [44]. Upon cooling, phase separation takes place. The catalyst is recovered finally by simple decantation. One of the last summaries in this area was given by Mathison and Cole-Hamilton in 2006 [45]. 

---