Celanese hydroformylation studies

Figure 8.3. Examples of bidentate diphosphine ligands used in the Celanese hydroformylation studies (27-30).

Three commercial homogeneous catalytic processes for the hydroformyla-tion reaction deserve a comparative study. Two of these involve the use of cobalt complexes as catalysts. In the old process a cobalt salt was used. In the modihed current version, a cobalt salt plus a tertiary phosphine are used as the catalyst precursors. The third process uses a rhodium salt with a tertiary phosphine as the catalyst precursor. Ruhrchemie/Rhone-Poulenc, Mitsubishi-Kasei, Union Carbide, and Celanese use the rhodium-based hydroformylation process. The phosphine-modihed cobalt-based system was developed by Shell specih-cally for linear alcohol synthesis (see Section 7.4.1). The old unmodihed cobalt process is of interest mainly for comparison. Some of the process parameters are compared in Table 5.1. 

The Rh/PPhs hydroformylation catalyst system was developed approximately simultaneously by Geoffrey Wilkinson (and students),Union Carbide, BASF, and Celanese. This catalyst system has been extensively studied, and the key species is HRh(CO)(PPh3)2. Once again the core mechanism is the same as that discussed previously for the cobalt systems and shown in Figure 12. Rhodium catalysts are approximately 1,000 times faster than ones based on cobalt (Rh is also about 1,000 times more expensive). Thus, rhodium catalysts can be run at considerably milder pressures and temperatures (8-10 bar, 125 °C), which dramatically reduces the capital expenditures for industrial plant construction. The increased activity of Rh over Co mainly derives from the stronger electronic preference of... 

Conversion of teipenes to aldehyde derivatives by hydroformylation has been studied extensively. Hydroformylation of limonene is practiced commercially by Celanese [34]. Limonene aldehyde has a citrus odor and is used in soaps and lotions. Spirambrene is manufactured by Givaudan and Vigrai by hydroformylation of 2-carene [35, 36]. Tollens reaction of the resulting aldehyde gives a diol which is converted to the acetal with acetone. Spirambrene has a woody, spicy odor and is a component of perfumes. 

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