Cobalt zeolite, hydroformylation

Propylene Hydroformylation Data Obtained Using Various Cobalt Zeolites ... 

A recent patent (to UOP) (228) claims that active hydroformylation catalysts can be prepared by reacting an aluminated zeolite (prepared from a hydrosol) with HCo(CO)4 vapor. The HCo(CO)4 complex apparently reacts with surface hydroxyl groups releasing hydrogen and yielding a surface-bound cobalt carbonyl complex. The catalyst so formed is claimed to hydroformylate higher olefins to aldehydes and alcohols at 120°C and 240 atm pressure. 

For hydroformylation over cobalt and rhodium zeolites the active species have not been defined. However, in the case of RhNaY the in situ formation of a rhodium carbonyl cluster has been identified (226) by infrared spectroscopy. Interestingly, this cluster appears to be different from known compounds such as Rh4(CO)12 and Rh6(CO)16. This does suggest that alternative carbonyl clusters may possibly be formed in zeolites due to the spatial restrictions of the intracrystalline cavities. The mechanism of hydroformylation in these zeolites is probably similar to that known for homogeneous catalysis. 

Anchoring of active catalysts to insoluble materials such as oxides, silicates, and zeolites often reduces the loss of catalyst during the catalytic process (66). The fixation of the active centers can be achieved either by means of their interaction with hydroxyl groups on a solid surface or, alternatively, by means of interactions between the CO ligands of the metal complex and a Lewis acidic center of the surface. Zeolite-supported cobalt catalysts have been reported for hydroformylation reactions (67). 

Hydroformylation reactions are important from the industrial point of view and the two commonly used hydroformylation catalysts are either Rh or Co based. We thought it would be interesting to anchor a SiOs unit on a cobalt cluster via hydrosilylation. This would be a close model to a silica-supported cobalt cluster. Secondly, since the reactions of silanetriols have been demonstrated to afford three-dimensional metallasiloxanes, we anticipated that this silanetriol would react with substrates such as trialkylaluminums, affording cobalt carbonyl cluster anchored aluminosiloxanes. Such compounds would resemble a modified zeolite having on its surface catalytically active cobalt carbonyl moieties and might inspire the preparation of actual zeolite systems with these modifications. 

Hetorogenized Catalysts.—Reaction of [Ru(NH3)60H] + with a Faujasite-type zeolite gives a supported Ru complex, which effects hydroformylation of ethylene the catalytic species may be ruthenium clusters that are trapped in the zeolite cages. The effect of reaction conditions upon the selectivity of the hydroformylation of methyl methacrylate with [RhH(CO)(PPh3)3] or its polymer-anchored analogue has been investigated and hydroformylation of hex-l-ene and cyclo-octa-1,5-diene has been carried out with cobalt, rhodium, and platinum-tin complexes anchored to an ion-exchange resin via quaternary amino-phosphines. ... 

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