Fischer-Tropsch reactions homogeneous

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. 

The actual structure of the active catalyst in the above reactions is a matter of speculation. The evidence, however, points to the presence of a homogeneous but immobilized Fischer-Tropsch catalyst. Since soluble CpCo(CO)2 does not possess Fischer-Tropsch activity, this activity is a unique feature of the polymer-bound system. The finding that 5 is regenerated quantitatively upon exposure of the active Fischer-Tropsch catalyst resin to CO implies that the n5-cyclopentadienylcobalt bond remains intact throughout the Fischer-Tropsch reaction. Similar... 

Support for the propagation step of the Fischer-Tropsch reaction is provided by the homogeneous reaction 1 11... 

In this chapter we also discuss two other catalytic reactions that involve CO as one of the reactants. These are the water-gas shift (see Section 1.2) and Fischer-Tropsch reactions. Although for these reactions homogeneous catalysts are not used industrially, for explaining the formation of by-products in the... 

Some mechanistic information is available on ruthenium-based homogeneous Fischer-Tropsch reactions. By in situ IR spectroscopy, in the absence of any promoter, only Ru(CO)5 is observed. An important difference between the cobalt and the rhodium system on the one hand and ruthenium on the other is that in the latter case no ethylene glycol or higher alcohols are obtained. In other words, in the catalytic cycle the hydroxymethyl route is avoided. 

Earl L. Mnetterties et al. Metal clusters as homogeneous catalysts for reduction of carbon monoxide in Fischer-Tropsch reaction... 

The two philosophies are typically exemplified by hydroformylation (eq. (1)) [26] on the one hand and the Fischer-Tropsch reaction (eq. (2)) [7] on the other. They both represent catalytic carbon monoxide chemistry in the first case the molecular structure of the homogeneous catalyst (Structures 1 and 2) is precisely known to be trigonal-bipyramidal,... 

Like Rh/1 systems, the Ir4(CO),2/l2 system catalyzes the carbonylation of methanol to acetic acid [70]. In homogeneous hydrogenation of CO (Fischer Tropsch reaction), Ir4(CO)i2 shows a relatively high catalytic activity compared with other transition metal carbonyls (eq (62)) [71]. 

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). 

Maitlis has reviewed the homogeneous and heterogeneous systems and noted that the former produce mainly oxygenated products, such as alcohols and esters. Most of the recent work on the Fischer-Tropsch reaction has focused on heterogeneous catalysts. The mechanism(s) of the later ate mainly inferred from isotope labeling and product distributions. The observations and mechanistic proposals of the Sheffield group have been summarized by Maitlis. However, there is still some controversy about the heterogeneous pathways. ... 

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. 

C. Homogeneous Catalysts for the Fischer-Tropsch and the Water Gas Shift Reactions... 

Only visual inspection of the reaction solution was made. Since the metals used, i.e., Ru, Os, Ir, Co, are heterogeneous Fischer-Tropsch catalysts, definite proof of the homogeneity of these systems must await detailed spectroscopic and kinetic measurements. 

A search for alternative energy supplies has triggered efforts to develop efficient homogeneous catalysts for Fischer-Tropsch-type syntheses via hydrogenation of carbon monoxide, a likely future key material available, for example, through oxidation of coal (33, 327, 328, 417, 418). Metal cluster systems have been used in attempts to emulate the presently used heterogeneous catalysts. The important reactions are methanation,... 

With the recent development of zeolite catalysts that can efficiently transform methanol into synfuels, homogeneous catalysis of reaction (2) has suddenly grown in importance. Unfortunately, aside from the reports of Bradley (6), Bathke and Feder (]), and the work of Pruett (8) at Union Carbide (largely unpublished), very little is known about the homogeneous catalytic hydrogenation of CO to methanol. Two possible mechanisms for methanol formation are suggested by literature discussions of Fischer-Tropsch catalysis (9-10). These are shown in Schemes 1 and 2. 

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