Hydrogen carbonylation

The observed increase in CH formation and simultaneous decrease in CO formation with increasing catalyst potential and work function i.e. with increasing supply of O2 to the catalyst is remarkable and can be attributed to the preferential formation on the Rh surface of electron donor hydrogenated carbonylic species leading to formation of CH4 and to the decreasing coverage of more electron acceptor carbonylic species resulting in CO formation.59... 

Isolated double and triple bonds are reduced readily, whereas conjugated alkenes and aromatic systems are difficult to hydrogenate. Carbonyl double bonds react only very slowly, if at all, so it is possible to achieve selective reduction of C=C double bonds in the presence of aromatic and carbonyl functions. 

It must be emphasized that the above considerations were made in the absence of reaction. Interfacial mass transfer followed by reaction requires further consideration. The Hatta regimes classify transfer-reaction situations into infinitely slow transport compared to reaction (Hatta category A) to infinitely fast transport compared to reaction (Hatta category H) [42]. In the first case all reaction occurs at the interface and in the second all reaction occurs in the bulk fluid. Homogenous catalytic hydrogenations, carbonylations etc. require consideration of this issue. An extreme example of the severity of mass transport effects on reactivity and selectivity in hydroformylation has been provided by Chaudari [43]. Further general discussions for homogeneous catalysis can be found elsewhere [39[. 

The solubility of gases, e.g. H2, CO and O2, is generally good which makes them attractive solvents for catalytic hydrogenations, carbonylations, hydroformylations, and aerobic oxidations. 

The papers in this volume concern results observed in catalytic systems. They span a broad range of catalytic reactions including hydro-formylation, hydrocarboxylation, hydrogenation, carbonylation, cyana-tion, and olefin oxidation. To some extent, the results provide a significant extension of our understanding of previously studied catalysts and catalytic reactions. However, some of the papers are concerned with newer areas of research and feature results of both scientific and potential industrial importance. 

The support effect in terms of selectivity can be observed in Table 3. The results show that the axial-equatorial carvomenthol is the only product when the support is magnesia. Rh/MgO catalysts results to be highly stereoespecific for the hydrogen carbonyl addition. 

Hydrogenative carbonylation of methyl acetate to 1,1-diacetoxyethane followed by cleavage to vinyl acetate and acetic acid. Only syngas is involved as raw materials. 

The solubility of reactive gases such as H2, CO and 02 is also very important in many catalysed reactions such as hydrogenation, carbonylation, hydroformylation and oxidation. The general trend for the solubility of... 

Addition of ferric chloride to certain liquors produced in the manufacture of Prussian blue in a French factory by the methylamine method (see p. 213) resulted in the precipitation of a violet compound.1 Several hundred grams of this were isolated by Muller, warmed with potassium carbonate and hydroxide successively, and the filtered solution allowed to crystallise. The product thus isolated crystallised in thin scales and rectangular prisms, and proved to be the potassium salt of an entirely new acid, namely hydrogen carbonyl ferrocyanide, H3Fe(CN)5.CO. Following up this discovery, Muller succeeded in preparing a series of well-defined salts. 

Hydrogen carbonyl ferrocyanide, or carbonyl ferrocyanic acid,... 

A further useful feature of SCFs is their total miscibility with gases. This circumvents the problem of low gas solubility in organic solvents for reactions such as hydrogenation, carbonylation or hydroformylation, and obviates the need for stirring a single homogeneous phase is always present. 

In a first approximation, the new methods correspond to the conventional solvent techniques of supported catalysts (cf Section 3.1.1.3), liquid biphasic catalysis (cf Section 3.1.1.1), and thermomorphic ( smart ) catalysts. One major difference relates to the number of reaction phases and the mass transfer between them. Owing to their miscibility with reaction gases, the use of an SCF will reduce the number of phases and potential mass transfer barriers in processes such as hydrogenation, carbonylations, oxidation, etc. For example, hydroformylation in a conventional liquid biphasic system is in fact a three-phase reaction (g/1/1), whereas it is a two-phase process (sc/1) if an SCF is used. The resulting elimination of mass transfer limitations can lead to increased reaction rates and selectiv-ities and can also facilitate continuous flow processes. Most importantly, however, the techniques summarized in Table 2 can provide entirely new solutions to catalyst immobilization which are not available with the established set of liquid solvents. 

Cyclic secondary amines may be obtained by hydrogenating carbonyl compounds that contain, at a suitable position, a group that is reducible to a... 

Deoxygenation of sulfoxides. Palladium (5%) on charcoal is an effective catalyst for hydrogenation of alkyl and aryl sulfoxides to sulfides (ethanol, autoclave, 80-90°, 1 atm. of hydrogen). Carbonyl groups are not reduced, but a carbon—carbon double bond is reduced, although more slowly than the S=0 group. 

In analyzing more than 250 publications Chapter 4 covers effective metal catalysts, mainly nickel, but also bimetal- and multimetal-systems, and their best modifiers, amino acids and tartaric acids. It is noted that it took more than 25 years to improve the modified nickel catalysts from their original poorly efficient systems into the modem excellent heterogeneous catalysts that hydrogenate carbonyl compounds with enantioselectivities of 96-98%. 

Metal-catalyzed hydrogenations, carbonylations, hydroformylations, etc. involve transition metals in low oxidation states coordinated to soft ligands, e.g., phosphines, as the catalytically active species and organometallic compounds as reactive... 

Based on the activation and elementary steps outlined, a variety of catalytic reactions can be better understood and catalytic cycles defined. We consider a few major classes of reactions isomerization, hydrogenation, carbonylation, hydroformylation, oxidation, and metathesis. 

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