Hydroformylation or Oxo Reaction

Biphasic techniques for recovery and recycle are among the recent improvements of homogeneous catalysis - and they are the only developments which have been recently and successfully applied in the chemical industry. They are specially introduced into the hydroformylation (or "oxo") reaction, where they form a fourth generation of oxo processes (Figure 5.1 [1]). They are established as the "Ruhrchemie/Rhone-Poulenc process" (RCH/RP) [2] cf. also Section 5.2.4.1), with annual production rates of approximately 800,000 tonnes y"1 (tpy). 

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 ... 

Otto Roelen at Ruhrchemie AG discovered the hydroformylation or oxo reaction in 1938. As shown by reaction 5.1, the basic reaction is the addition of a hydrogen atom and a formyl group to the double bond of an alkene. The reaction works efficiently, mainly with terminal alkenes. With an optimal choice of ligands and process conditions, very high selectivity (>95%) for the desired isomer of the aldehyde could be achieved. 

The hydroformylation or oxo reaction has been chosen for particular study for several reasons (a) The reaction was discovered by Roelen 2) in the course of an investigation of the mechanism of the Fischer-Tropsch reaction, and a study of the hydroformylation reaction could furnish information on the course of this heterogeneously catalyzed synthetic fuel process (6) hydroformylation involves the activation of hydrogen by a molecularly dispersed catalyst (c) there are few side reactions (d) the catalyst for the reaction, Co2(CO)s, is easily prepared, is relatively nontoxic, and is consequently readily available for study and (e) the reaction is of great industrial importance. 

This reduction is very likely the last step in the industrially important hydroformylation or oxo reaction for converting olefins into aldehydes (4). The catalytic species seems to be cobalt hydrocarbonyl, which first adds to the olefin as in Eq. (2). The alkylcobalt tetracarbonyl so formed then probably isomerizes to the acylcobalt tricarbonyl [Eq. (25)] and is reduced by hydrogen as in Eqs. (45) and (46). 

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. 

At the ACS National Meeting in the spring of 2013 in New Orleans, the 75th anniversary of this fundamental catalytic reaction [4], named hydroformylation (or oxo-reaction, Scheme 8.1), was celebrated through a special symposium. 

Propylene and a-alkenes can be reacted with synthesis gas to give -butyraldehyde and alcohols, respectively. These reactions are called hydroformylation or oxo-reactions. The reaction between butadiene and hydrocyanic acid to obtain adiponitrile is called hydrocyanation. The mechanistic details and the relevance of hydroformylation and hydrocyanation reactions for the manufacture of consumer products are discussed in Chapter 5. 

Garbonylation of Olefins. The carbonylation of olefins is a process of immense industrial importance. The process includes hydroformylation and hydrosdylation of an olefin. The hydroformylation reaction, or oxo process (qv), leads to the formation of aldehydes (qv) from olefins, carbon monoxide, hydrogen, and a transition-metal carbonyl. The hydro sdylation reaction involves addition of a sdane to an olefin (126,127). One of the most important processes in the carbonylation of olefins uses Co2(CO)g or its derivatives with phosphoms ligands as a catalyst. Propionaldehyde (128) and butyraldehyde (qv) (129) are synthesized industrially according to the following equation ... 

Oxo or Hydroformylation and Hydroesterification. Reactions of alkenes with hydrogen and formyl groups are cataly2ed by HCo(CO)4... 

C-19 dicarboxyhc acid can be made from oleic acid or derivatives and carbon monoxide by hydroformylation, hydrocarboxylation, or carbonylation. In hydroformylation, ie, the Oxo reaction or Roelen reaction, the catalyst is usually cobalt carbonyl or a rhodium complex (see Oxo process). When using a cobalt catalyst a mixture of isomeric C-19 compounds results due to isomerization of the double bond prior to carbon monoxide addition (80). 

Oxo reaction or hydroformylation reaction involves addition of a hydrogen atom and a formyl group (-CHO) to C=C double bond of an olefin making both anti—Markovnikov and Markovnikov products ... 

The hydroformylation reaction, also known as the oxo reaction, is used extensively in commercial processes for the preparation of aldehydes by the reaction of one mole of an olefin with one mole each of hydrogen and carbon monoxide. The most extensive use of the reaction is in the preparation of normal- and iso-butyraldehyde from propylene. The ratio of the amount of the normal aldehyde product to the amount of the iso aldehyde product typically is referred to as the normal to iso (N I) or the normal to branched (N B) ratio. In the case of propylene, the normal- and iso-butyraldehydes obtained from propylene are in turn converted into many commercially-valuable chemical products such as n-butanol, 2-ethyl-hexanol, trimethylol propane, polyvinylbutyral, n-butyric acid, iso-butanol, neo-pentyl glycol,... 

Mitsubishi Kasei introduced a process to manufacture isononyl alcohol, an important PVC (polyvinyl chloride) plasticizer, via the hydroformylation of octenes (a mixture of isomers produced by dimerization of the C4 cut of naphtha cracker or FCC processes).95 First a nonmodified rhodium complex exhibiting high activity and selectivity in the formation of the branched aldehyde is used. After the oxo reaction, before separation of the catalyst, triphenylphosphine is added to the reaction mixture and the recovered rhodium-triphenylphosphine is oxidized under controlled conditions. The resulting rhodium-triphenylphosphine oxide with an activity and selectivity similar to those of the original complex, is recycled and used again to produce isononanal. 

Hydroformylation, or the oxo process, is the reaction of olefins with CO and hydrogen to make aldehydes. The catalyst base is cobalt naphthenate which transforms to cobalt hydrocarbonyl in place. A rhodium complex that is more stable and functions at a lower temperature also is used. 

T,he hydroformylation reaction or oxo synthesis has been used on an industrial scale for 30 years, and during this time it has developed into one of the most important homogeneously-catalyzed technical processes (I). A variety of technical processes have been developed to prepare the real catalyst cobalt tetracarbonyl hydride from its inactive precursors, e.g., a cobalt salt or metallic cobalt, to separate the dissolved cobalt carbonyl catalyst from the reaction products (decobaltation) and to recycle it to the oxo reactor. The efficiency of each step is of great economical importance to the total process. Therefore many patents and papers have been published concerning the problem of making the catalyst cycle as simple as possible. Another important problem in the oxo synthesis is the formation of undesired branched isomers. Many efforts have been made to keep the yield of these by-products at a minimum. 

Hydroformylation (the oxo process) involves the addition of H2 and CO to an olefin to form aldehydes (eq. 2.8), which have a number of important industrial applications. Extensive mechanistic studies have shown that this reaction involves migratory insertion of a bound alkyl group (formed by insertion of an olefin into a metal hydride) into a bound CO, followed by reductive elimination of the aldehyde. The rate-limiting step for the hydroformylation in liquids is either the reaction of olefin and HCo(CO)4 or the reaction of the acyl complex with H2 to liberate the product aldehyde. The high miscibility of CO in sc C02 is therefore not necessarily a major factor in determining the rate of the hydroformylation. Typically, for a-olefins, linear aldehydes are preferred to branched products, and considerable effort has gone into controlling the selectivity of this reaction. 

Originally, Piacenti et al. explained the formation of isomeric products in terms of an equilibrium of alkylcobalt carbonyls with olefin-hydrocarbonyl complexes as in the Oxo reaction. More recently, however, they have noted that the conditions under which n-propyl orthoformate gave no isomeric products (below 150° C, carbon monoxide pressure 10 atm) are conditions under which isomerization occurs readily in the hydroformylation of olefins (115). Since alkylcobalt carbonyls were formed in both reactions they dismissed the possibility that this isomerization was due to alkyl- or acylcobalt carbonyls. The fact that Takegami et al. have found that branched-chain acylcobalt tetracarbonyls isomerize more readily than straight-chain acylcobalt tetracarbonyls would seem to fit in quite well with the results of Piacenti et al., however, and suggests that the two findings may not be so irreconcilable as might at first appear (see Section II, B,2). 

Formation of aldehydes by the reaction of alkene, CO and H2 catalysed by Co2(CO)8 was discovered by Rolen in 1938 [25]. This is the 1,2-addition of H and CHO to alkenes, and hence called hydroformylation or the oxo reaction. Production of butanal, (33) from propylene as a main product is an important industrial process. Aldol condensation of butanal, followed by hydrogenation affords 2-ethyl-1-hexanol (34), which is converted to phthalate, and used as a plasticizer of poly(vinyl chloride). 

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. 

In the normal oxo reaction a certain amount of hydrogenation occurs, a minor amount of olefins being converted to paraffins in the case of certain olefinic compounds hydrogenation indeed occurs to the exclusion of hydroformylation. It is a remarkable fact that this catalytic reaction occurs in the presence of carbon monoxide and also of sulfur compounds, although cobalt metal is notoriously poisoned by traces of these compounds. The significance of this was pointed out by Adkins and Krsek (23) and Wender, Orchin, and Storch (25) in terms of the concept that the hydroformylation catalyst is a homogeneous one, not sensitive to carbon monoxide or sulfur compounds and in this respect different from usual solid cobalt catalysts. 

The hydroformylation (oxo) reactions offer ways of converting a-olefins to aldehydes and/or alcohols containing an additional carbon atom. 

To account for the final stage of hydroformylation, Heck and Bres-low a) suggested the intermediacy of coordinately unsaturated acylcobalt tricarbonyls, which are reduced to aldehydes by hydrogen or converted into tetracarbonyls by carbon monoxide. The well known adverse effect of carbon monoxide on die course of the oxo reaction may, therefore, be attributed to this competition. 

The hydroformylation reaction or oxo synthesis, discovered in 1938 by O. Roelen in the laboratories of Ruhr Chemie in Germany, is of great importance as a synthetic tool. Starting from an alkene and using syn-gas (Hj/CO = 1/1), aldehydes with one more carbon are obtained, according to Eq. (1). More than 5 million tons of aldehydes are produced in the... 

The reaction of an alkene with carbon monoxide and hydrogen, catalyzed by cobalt or rhodium salts, to form an aldehyde is called hydroformylation (or sometimes the oxo... 

Hydroformylation (or the Oxo-process) is the conversion of alkenes to aldehydes (reaction 26.17). It is catalysed by cobalt and rhodium carbonyl complexes and has been exploited as a manufacturing process since World War II. 

When straight or branched olefins, with the double bond in other than the terminal position, are subjected to the Oxo reaction, the products are almost identical with those obtained from the isomeric olefin in which the double bond is in the terminal position. For example, almost the same distribution of products was obtained from pentene-2 as from pentene l. In these tests the aldehydes (which are sensitive to heat and light) were reduced to the corresponding alcohols, and these were separated and identified. The alcohols from pentene-2 contained 10 per cent 2-ethyl-butanol-1, 46 per cent 2-methylpentanol-l, and 44 per cent 1-hexanol those from pentene-1 contained 6 per cent 2-ethylbutanol-l, 46 per cent 2-methylpentanol-l, and 48 per cent 1-hexanoL However, the rates of hydroformylation were quite different, that of pentene-1 being approximately 3.5 times that of pentene-2. This is a general rate relationship for isomeric olefins with the double bond in the terminal and internal positions. 

Since its discovery by Roelen in 1938, hydroformylation or the oxo process has become one of the most important methods for the synthesis of aldehydes. Aldehydes produced via hydroformylation are critical feedstock and synthetic precursors in both basic research and industrial applications. The significance of this reaction in chemical industry has drawn much attention in both basic and applied research, leading to the development of more efficient and versatile reaction processes. 

Diisononyl phthalate and diisodecyl phthalate are produced by esteriflcation of oxo-alcohols of carbon chain length 9 and 10. The oxo-alcohols are produced through the carbonylation of alkenes (olefins). The hydroformylation or carbony-lation process (eq. 6) adds a carbon unit to an alkene chain by reaction with carbon monoxide and hydrogen with heat, pressure, and catalyst. In this way a Cs alkene is carbonylated to yield a Cg alcohol. Because of the distribution of the C=C double bond in the alkene and the varying effectiveness of certain catalysts, the position of the added carbon atom can vary and an isomer distribution is generally created in such a reaction. The nature of this distribution depends on the reaction conditions. Consequently, these alcohols are termed iso-alcohols and the subsequent phthalates iso-phthalates. 

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