Catalysts in hydroformylation

To date, these functionalized ligands have been investigated on the laboratory scale, in batch operations to immobilize rhodium catalyst in hydroformylation. 

Rhodium complexes of phosphorus based ligands are of considerable importance as (pre-)catalysts in hydroformylation which has developed into one of the most important homogeneous catalytic processes [57]. A recent advantage in this field involved the use of phosphinines as ligands whose low-lying r -orbitals provide for similar r-acceptor qualities as for phosphites [13, 58]. 

The use of cobalt carbonyls, modified cobalt catalysts, and ligand-modified rhodium complexes, the three most important types of catalysts in hydroformylation,... 

Polyquinolines have been used as polymer supports for transition-metal catalyzed reactions. The coordinating ability of polyquinoline ligands for specific transition metals has allowed their use as catalysts in hydroformylation reactions (99) and for the electrochemical oxidation of primary alcohols... 

Catalyst performance has of course been a permanent theme in industry. For example, the catalytic activity of oxo catalysts (in hydroformylation) has improved in the past 50 years by a factor of 10 000 change from diadic and triadic process technology to continuous plant operation, replacement of cobalt by rhodium, tailoring of the ligand sphere (phosphines), change of phase application (from mono- to two-phase processes). At the same time, an improvement of selectivity has been achieved, apart from the ease of product/catalyst separation [132]. A similar development seems to occur in the Monsanto acetic acid process [49]. 

The surface-active character of sulfonated phosphines, e.g., TPPMS (lb, n = 2), was already noted in 1977 by Wilkinson et al., who also commented on the participation of the SOy groups in the coordination of these ligands to transition metals in catalyst complexes (13) [50]. Rh complexes of lb (TPPDS) have been employed as catalysts in hydroformylation of olefins in biphasic media [21a]. The p-isomer 2b (Ph2P—C6H4-p-S03K) was, however, much more reactive in the presence of a surfactant (lauric acid) [21b]. Rh catalysts using TPPMS have been employed in... 

The prediction that tetracarbonylcobalt hydride would act as a catalyst in hydroformylation reactions 133, 224) has been amply verified for example, the stoichiometric hydroformylation, using HCo(CO)4, of 1-pen-tene at room temperature affords a variety of isomeric aldehydes 187). Also, HCo(CO)4 is formed under the high pressure (100 atm. 1 1 H2 CO) and temperature (100°-300°C) conditions of the hydroformylation reaction 183, 226). 

Many engineering factors have a profound influence on the performance of catalysts in hydroformylation, and their effects are demonstrated in terms of reaction indices such as conversion and selectivity. More concretely, these factors influence the mass transfer rate, phase dispersion, emulsification and demulsification, catalyst distribution, product separation, etc. (Table 1). 

Pd showed significantly promotional effect than Pt and Ru for Co/Si02 catalyst in hydroformylation of 1-hexene [4], Cobalt free lwt% Ru, Pt and Pd supported on active carbon were prepared and tested in hydroformylation reaction. As shown in Table 1, these kinds of catalysts showed very low activity for 1-hexene hydroformylation. For the Ru catalyst, the 1-hexene eonversion was 81.3%, but the 1-hexene was only converted to isomerization produets. For the Pt and Pd catalysts, both the 1-hexene conversion and oxygenates selectivity were very low. Results show in Table 1 indicate that the noble metal/active carbon catalysts themselves had no catalytic activity of 1-hexene hydroformylation to form oxygenates. 

The formation and reactivity of catalytically important intra-zeolite rhodium carbonyls have been investigated in some detail [270-276]. Such materials are of interest as catalysts in hydroformylation [277, 278] and water-gas shift [279] reactions. 

CO can be almost completely expelled, and/or the required vacant coordination sites are blocked (V). As a consequence, the rate of hydroformylation decreases. Complexes with one (II) or two phosphorus ligands (III) are considered to be the most active catalysts in hydroformylation. In contrast, three monodentate and one tridentate, respectively, or even two bidentate diphosphorus ligands on rhodium can be efficient in related reactions, such as decarbonylation (see Chapter 8). 

Scheme 1.62 Comparison of hetero- and homobimetallic catalysts in hydroformylation.

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