The oxo process

An example of such recychng in a parallel reaction system is in the Oxo process for the production of C4 alcohols. Propylene and synthesis gas (a mixture of carbon monoxide and hydrogen) are first reacted to ra- and isobutyraldehydes using a cobalt-based catalyst. Two parallel reactions occur ... 

The 13—carbon tridecyl alcohol is usually considered to be a plasticizer range alcohol because of its manufacture by the oxo process and its use in making plasticizers. On the other hand, some types of linear 9- and 11-carbon alcohols find major appHcation in detergents. 

A.luminum Jilkyl Chain Growth. Ethyl, Chevron, and Mitsubishi Chemical manufacture higher, linear alpha olefins from ethylene via chain growth on triethyl aluminum (15). The linear products are then used as oxo feedstock for both plasticizer and detergent range alcohols and because the feedstocks are linear, the linearity of the alcohol product, which has an entirely odd number of carbons, is a function of the oxo process employed. Alcohols are manufactured from this type of olefin by Sterling, Exxon, ICI, BASE, Oxochemie, and Mitsubishi Chemical. 

Oxo Synthesis. Ad of the synthesis gas reactions discussed to this point are heterogeneous catalytic reactions. The oxo process (qv) is an example of an industriady important class of reactions cataly2ed by homogeneous metal complexes. In the oxo reaction, carbon monoxide and hydrogen add to an olefin to produce an aldehyde with one more carbon atom than the original olefin, eg, for propjiene ... 

Lighter C —Cg a-olefias and Cg branched olefins are converted by the oxo process into fatty acids containing one carbon number greater than the starting a-olefin. These fatty acids are then used to produce alkenylhen enesulfonic acid products which are used ia the United States and ia Europe as perborate bleach activators ia heavy-duty laundry detergents. 

Hiadered esters are also produced from and Cg a-olefias. These olefias are coaverted iato C —C fatty acids by the oxo process the acids are thea treated with polyols such as peataerythritol and trimethylol propane to produce hindered esters, which find use ia lubricants for jet engines and other high performance appHcations. 

Synthesis gas, a mixture of CO and o known as syngas, is produced for the oxo process by partial oxidation (eq. 2) or steam reforming (eq. 3) of a carbonaceous feedstock, typically methane or naphtha. The ratio of CO to may be adjusted by cofeeding carbon dioxide (qv), CO2, as illustrated in equation 4, the water gas shift reaction. 

Union Carbide Chemicals and Plastics Company Inc. is the only producer of C-5 oxo derived alcohols (148,150) in the United States. About 75% of the 30,000 t of valeraldehyde and 2-methylbutyraldehyde produced by the oxo process was converted to the isomeric mixture of primary amyl alcohols in 1988 (150). The primary amyl alcohol mixture was available in tank car quantities for 1.02/kg in 1991. The Dow Chemical Company appears to have stopped commercial production of / fZ-amyl alcohol (151). 

The demand for amyl alcohols is expected to remain unchanged until 1993. Competition from other alcohols and limited appHcations limit growth in markets for amyl alcohols. U.S. demand was predicted to grow from 29 x 10 t in 1983 to 32 x Kf t by 1990 (152). In Europe, amyl alcohols account for over 80% of the demand for valeraldehyde (17,000 t in 1984). BASE and Hoechst AG produce both / -valeraldehyde and 2-methylbutyraldehyde from butenes by the oxo process (149). The demand for C-5 in Europe is also predicted not to grow substantially (150). Amyl alcohols are growing at a much lower rate than other oxo alcohols as shown in Table 7. 

The switch from the conventional cobalt complex catalyst to a new rhodium-based catalyst represents a technical advance for producing aldehydes by olefin hydroformylation with CO, ie, by the oxo process (qv) (82). A 200 t/yr CSTR pilot plant provided scale-up data for the first industrial,... 

The earhest modification of the Oxo process (qv) employed cobalt hydrocarbonyl, HCo(CO)4, as catalyst. The reaction was carried out in the Hquid phase at 130—160°C and 10—20 MPa (1450—2900 psi) to give a ratio of n- to isobutyraldehyde of between 2 1 to 4 1. / -Butyraldehyde, the straight-chain isomer and the precursor of 2-ethylhexanol, was the more valuable product so that a high isomer ratio of n- to isobutyraldehyde was obviously advantageous. 

Olefin Hydroformylation (The Oxo Process). One of the most important iadustrial applications of transition-metal complex catalysis is the hydroformylation of olefins (23), ihusttated for propjdene ... 

Catalyst improvements allow methanol plants and plants using the Oxo process for aldehyde production to operate at lower pressures. The process also has a higher yield and produces a better quality product (Dale, 1987). 

Currently, worldwide production of aldehydes exceeds 7 million tons/year (1). Higher aldehydes are important intermediates in the synthesis of industrial solvents, biodegradable detergents, surfactants, lubricants, and other plasticizers. The process, called hydroformylation or more familiarly, the Oxo process, refers to the addition of hydrogen and the formyl group, CHO, across a double bond. Two possible isomers can be formed (linear or branched) and the linear isomer is the desired product for these applications. 

The synthesis of phthalimidines by dicobalt octacarbonyl-catalyzed carbonylation of Schiff bases was first described by Pritchard78 and the scope of the reaction was evaluated by Murahashi et a/.79 Later Rosenthal et al.80-83 subjected a variety of related compounds to carbonylation, and also achieved a phthalimidine synthesis directly from benzonitrile under the conditions of the oxo process.84 An example illustrating the formation of a phthalimidine is shown in Scheme 49 a comprehensive review of the scope and mechanism of reactions of this type is available.85... 

The synthesis of tetrahydrofuran derivatives from unsaturated alcohols via hydroformylation intermediates was developed many years ago. Moderate yields are obtained from but-2-en-l,4-diol (Scheme 54)94 but hydroformylation is not the major pathway when coniferyl alcohol is subjected to the oxo process (Scheme 55).9S A more complicated reaction is involved... 

Pyrrolidone is the major product when allylamine is subjected to the conditions of the oxo process using dicobalt octacarbonyl as the catalyst.203 The by-products are pyridine derivatives 112 and 113 and these compounds become the major products when iron pentacarbonyl is used as the catalyst ... 

Also referred to as the oxo process or hydrocarbonylation, hydroformylation is a route to producing an aldehyde from an alkene, hydrogen, and carbon monoxide. This process has been known for approximately 70 years, and it is still economically important because useful compounds are produced in enormous quantities by this means. The reaction is summarized by the following equation ... 

The mechanism of hydrosilation can be rationalized as described by Chalk and Harrod (1 l-lId). In this view, all the chemical changes take place within the coordination sphere of a transition metal. Other reactions of unsaturated molecules are explained in much the same way. Hydrogenation, the oxo-process, and the Ziegler process are important examples. 

Normal butyl alcohol (NBA) was first recovered in the 1920s as a by-product of acetone manufacture via cornstarch fermentation. That route is almost extinct now. A small percent is still made from acetaldehyde. The primary source of NBA, however, is the Oxo process. 

Ethyl hexanol, sometimes called 2-ethyl hexyl alcohol, 2-ethyl hex, or more simply 2-EH, is one of the oldest high molecular weight aliphatic alcohols. What does it have in common with NBA Both are made from propylene via the Oxo process, and both have the same aldehyde intermediate— normal butyraldehyde. 

The same front-end Oxo process is used to make the butyraldehyde feed for 2-EH manufacture, but then the butyraldehyde is dimerized in a reaction called aldol condensation. Some plants even combine the Oxo process and the Aldol process and then refer to it as the Aldox process. 

Unfortunately, secondary and tertiary butyl alcohols (SBA and TBA) cannot be made by the Oxo process. Instead they are produced either by indirect or direct hydration of the corresponding olefin. Normal butylene gives SBA and isobutylene gives TBA. The processes are similar to the corresponding routes to IPA. 

The Oxo process, a.k.a. the hydroformylation reaction, is the same as that described in Chapter l4, Some Other Alcohols, in the section on NBA. This process can also be applied to higher alcohols by just substituting feeds of longer chain length. 

The Oxo process uses synthesis gas with a H2 to C(0 ratios of 1 1 to 2 1, Hydro for mylation in the Oxo reactor takes place at moderate temperatures, 212-400°F, but very high pressures, 3000-5000 psi. The effluent from the reactor is cleaned up to remove light gas by-products to recover the catalyst for recycling and to recycle any unreacted olefin. Ac this point, the balance between the aldehyde isomers can be adjusted by fractionating out the... 

Another source, catalytic oligomerization, which produces the alpha olefins using the Ziegler process mentioned above, has its own treatment in Chapter 21. But then the Oxo process really only replaces steps-three and four in Figure 15-3. Besides, Oxo higher alcohols still have branches. 

In 25 words or less, describe the differences between the Oxo process and the Ziegler process for making higher alcohols. 

Aldox process. A two-step process combining the Oxo process and the Aldol Process. For example, propylene is reacted with carbon monoxide and hydrogen to form butyraldehyde (Oxo process), which is then dimerized and hydrogenated to give 2-ethylhexyl alcohol. 

To get the long-chain olefins to feed the Oxo process, some producers use a Ziegler process to grow them on the Al(C2H5)3 root. The difference then is only how to get from the AJ(C2H5)3-connected chain to the alcohol, via Oxo or via oxidation and hydrolysis. 

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