Cobalt catalysts hydroformylation, Fischer-Tropsch

The polymers were converted to supported catalysts corresponding to homogeneous complexes of cobalt, rhodium and titanium. The cobalt catalyst exhibited no reactivity in a Fischer-Tropsch reaction, but was effective in promoting hydroformylation, as was a rhodium analog. A polymer bound titanocene catalyst maintained as much as a 40-fold activity over homogeneous titanocene in hydrogenations. The enhanced activity indicated better site isolation even without crosslinking. 

Q Fischer-Tropsch Synthesis and Hydroformylation on Cobalt Catalysts The Thermodynamic Control... 

The reaction does not proceed in the absence of catalysts. As the contemporary Fischer-Tropsch catalysts were heterogeneous, the first hydroformylation catalyst was a solid (66% silica, 30% cobalt, 2% thorium oxide, and 2% magnesium oxide). Only later was the conclusion reached and proved (5) that the actual catalytic species is homogeneous. 

The hydroformylation of alkenes was accidentally discovered by Roelen while he was studying the Fischer-Tropsch reaction (syn-gas conversion to liquid fuels) with a heterogeneous cobalt catalyst in the late thirties. In a mechanistic experiment Roelen studied whether alkenes were intermediates in the "Aufbau" process of syn-gas (from coal, Germany 1938) to fuel. He found that alkenes were converted to aldehydes or alcohols containing one more carbon atom. It took more than a decade before the reaction was taken further, but now it was the conversion of petrochemical hydrocarbons into oxygenates that was desired. It was discovered that the reaction was not catalysed by the supported cobalt but in fact by HCo(CO)4 which was formed in the liquid state. 

During a study of the origin of oxygenates in Fischer-Tropsch synthesis in the presence of a cobalt catalyst, Roelen observed the formation of propanal and 3-penta-none when ethylene was added to the feed.1 The process now termed hydroformylation or oxo reaction is the metal-catalyzed transformation of alkenes with carbon monoxide and hydrogen to form aldehydes ... 

Transition metal carbonyls and their derivatives are remarkably effective and varied in their ability to catalyze reactions between unsaturated molecules (e.g., CO and olefinic compounds) or between certain saturated and unsaturated molecules (e.g., olefins and H2 or H20). The carbonyl derivatives of cobalt are particularly active catalysts for such reactions and have been put to use in the industrial synthesis of higher aliphatic alcohols. In fact, much of the growth in knowledge concerning catalysis by metal carbonyls has been stimulated by the industrial importance of the Fischer-Tropsch synthesis, and by the economically less important, but chemically more tractable, hydroformylation reaction. 

One of the most interesting catalytic reactions to be discovered is the so-called oxo reaction. The oxo reaction consists of the catalytic addition of carbon monoxide and hydrogen to olefins to form, primarily, aldehydes possessing one carbon atom more than the original olefin. This hy-droformylation reaction was developed during World War II by Roelen and co-workers (22) in Germany. While they utilized solid Fischer-Tropsch cobalt-thoria catalyst, it became apparent to them that the hydroformylation reaction was probably a homogeneous catalytic process with either dicobalt octaearbonyl or cobalt hydrocarbonyl as the catalyst. 

The hydroformylation (or 0x0 ) reaction was discovered in 1938 by Roelen who was working on the formation of oxygenates as by-products of the Fischer-Tropsch reaction over cobalt catalysts. It soon became clear that the aldehydes and alcohols found were the products of secondary reactions undergone by the 1-alkenes (which are the primary products of the Fischer-Tropsch reaction, Section 4.7.2) with syngas. Further work showed that Roelen had discovered a new reaction, in which the elements of H and CHO were added to an olefin (hence hydroformylation), and which was catalyzed by cobalt. It was later found that the true precatalyst was not cobalt metal but derivatives of dicobalt octacarbonyl, such as the hydride, CoH(CO)4. 

One of the earliest reactions involving the insertion of CO into a Cn-olefin molecule to produce an aldehyde with one greater Cn+i carbon number is the so-called hydroformylation or "0x0 " reaction. The 0x0 reaction is carried out over homogeneous catalysts, rhodium or cobalt carbonyls, and is an important industrial process. Recently the production of acetic acid, acetaldehyde, and glycol from CO and H2 over heterogeneous and homogeneous rhodium catalysts have been reported. Straight-chain saturated hydrocarbons are not the only molecules that may be produced in the Fischer-Tropsch reaction. There have been... 

The discovery of hydroformylation by Otto Roelen was made while investigating the influence of alkenes on the Fischer-Tropsch reaction using a heterogeneous cobalt oxide catalyst supported on silica. Later it was concluded that hydroformylation is actually a homogeneous process catalyzed by ECo(CO) formed in situ. Many metals catalyze hydroformylation, but the most active catalysts contain cobalt, rhodium, palladium, and platinum as the central metal. The discussion in this chapter centers on the most utilized catalysts ECo(CO), ECo(CO)3PR3, ERh(CO)3(PR3)j, and HRhfCOljfdiphosphine). 

The hydroformylation or oxo reaction, or oxo synthesis discovered by Otto Roelen and patented in 1938 (1) is the addition of carbon monoxide and dihydrogen to an olefin double bond in the presence of a transition metal complex as the catalyst. The discovery of the reaction regarding the cobalt catalyzed Fischer-Tropsch reactions. Roelen s observation that ethylene, H2, and CO were converted into propanal, and at higher pressures, diethyl ketone, marked the beginning of hydroformylation catalysis (2). The term of hydroformylation relates to the formal addition of hydrogen and a formyl group to the olefin substrate. 

Several cobalt compounds are widely used as oxidation catalysts. Cobalt-based catalysts are also important in some industrial process such as the Fischer-Tropsch process [9] and the hydroformylation of alkenes [10]. Also, the cross-coupling reactions promoted by this metal have been recently highlighted [11]. Conversely, cobalt is not a suitable metal catalyst for the O-H addition to alkynes, alkenes, and nitriles. 

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