Butyraldehyde, hydroformylation propylene

Ans Ethylene a-alkenes (oligomerization), acetaldehyde (oxidation) propylene n-butyraldehyde (hydroformylation), propylene oxide (epoxidation) CO acetic acid, acetic anhydride (carbonylation). 

Hydroformylation of an olefin usiag synthesis gas, the 0x0 process (qv), was first commercialized ia Germany ia 1938 to produce propionaldehyde from ethylene and butyraldehydes from propylene (12). 

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,... 

Chemistry. The hydroformylation of allyl alcohol is illustrated in Eq. (58). The catalyst is a rhodium complex modified with triphenylphos-phine of the same type used for production of n-butyraldehyde from propylene in the oxo process. The reaction takes place in a toluene solution at approximately 2-3 atm pressure (15-30 psig) and 60°C (140 F). The conversion to 4-hydroxybutyraldehyde is 98% based on allyl alcohol with a selectivity of 79.1%. 

Rhodium Ca.ta.lysts. Rhodium carbonyl catalysts for olefin hydroformylation are more active than cobalt carbonyls and can be appHed at lower temperatures and pressures (14). Rhodium hydrocarbonyl [75506-18-2] HRh(CO)4, results in lower -butyraldehyde [123-72-8] to isobutyraldehyde [78-84-2] ratios from propylene [115-07-17, C H, than does cobalt hydrocarbonyl, ie, 50/50 vs 80/20. Ligand-modified rhodium catalysts, HRh(CO)2L2 or HRh(CO)L2, afford /iso-ratios as high as 92/8 the ligand is generally a tertiary phosphine. The rhodium catalyst process was developed joindy by Union Carbide Chemicals, Johnson-Matthey, and Davy Powergas and has been Hcensed to several companies. It is particulady suited to propylene conversion to -butyraldehyde for 2-ethylhexanol production in that by-product isobutyraldehyde is minimized. 

Propylene-Based Routes. The strong acid-catalyzed carbonylation of propylene [115-07-1] to isobutyric acid (Koch reaction) followed by oxidative dehydration to methacrylic acid has been extensively studied since the 1960s. The principal side reaction in the Koch reaction is the formation of oligomers of propylene. Increasing yields of methacrylic acid in the oxydehydration step is the current focus of research. Isobutyric acid may also be obtained via the oxidation of isobutyraldehyde, which is available from the hydroformylation of propylene. The -butyraldehyde isomer that is formed in the hydroformylation must be separated. 

The spectmm of oxo products ia Japan is far less diverse. Nearly 75% of Japan s total oxo capacity of 733,000 t is dedicated to the hydroformylation of propylene. 2-EH derived from -butyraldehyde is by far the dominant product. Other products iaclude linear alcohols and higher branched alcohols. Additionally, Japan is the world s principal source of branched heptyl alcohol. The three ptincipal Japanese oxo producers having slightly more than 70% of Japan s total oxo capacity are Mitsubishi Kasei, Kyowa Yuka, and Japan Oxocol. 

The catalytic hydroformylation of olefins is discussed in Chapter 5. The reaction of propylene with CO and H2 produces n-butyraldehyde as the main product. Isobutyraldehyde is a by-product °... 

The first stage of the process is a hydroformylation (oxo) reaction from which the main product is n-butyraldehyde. The feeds to this reactor are synthesis gas (CO/H2 mixture) and propylene in the molar ratio 2 1, and the recycled products of isobutyraldehyde cracking. The reactor operates at 130°C and 350 bar, using cobalt carbonyl as catalyst in solution. The main reaction products are n- and isobutyraldehyde in the ratio of 4 1, the former being the required product for subsequent conversion to 2-ethylhexanol. In addition, 3 per cent of the propylene feed is converted to propane whilst some does not react. 

One of the most selective hydroformylation catalysts was obtained when cobalt acetate was irradiated in the presence of an excess of a phosphine, with synthesis gas at 80 atm, in methanol as the solvent. Propylene was hydroformylated with this catalyst to give butyraldehyde with an n/i ratio of more than 99/1 /10/. In the absence of phosphine, the cobalt acetate forms a more active catalyst which is, however, less selective for straight chain products /23/. 

The principal product of the hydroformylation which is most desired in industrial applications is a linear aldehyde. The unmodified, cobalt-catalyzed processes produce a mixture of linear and branched aldehydes, the latter being mostly an a-methyl isomer. For the largest single application—propylene to butyraldehydes—the product composition has an isomer ratio (ratio of percent linear to percent branched) of (2.5 t.0)/l. The isobutyraldehyde cannot be used to make 2-ethylhexanol, and iso-... 

Butyraldehyde is made from propylene by the 0x0 process, also known as hydroformylation. Sjmthesis gas (CO + H2) is catalytically reacted with propylene to the butyraldehydes. The approximate yields are 67% -butyraldehyde and 15% isobutyraldehyde. 

The discovery and use of fluorophosphites and chlorophosphites as trivalent phosphorus ligands in the rhodium catalyzed, low-pressure hydroformylation reaction are described. The hydroformylation reaction with halophosphite ligands has been demonstrated with terminal and internal olefins. For the hydroformylation of propylene, the linear to branched ratio of the butyraldehyde product shows a strong dependency on the ligand to rhodium molar ratios, the reaction temperature, and the carbon monoxide partial pressure. 

The Ruhrchemie/Rhone-Poulenc process is performed annually on a 600,000 metric ton scale (18). In this process, propylene is hydroformylated to form butyraldehyde. While the solubility of propylene in water (200 ppm) is sufficient for catalysis, the technique cannot be extended to longer-chain olefins, such as 1-octene (<3 ppm solubility) (20). Since the reaction occurs in the aqueous phase (21), the hydrophobicity of the substrate is a paramount concern. We overcame these limitations via the addition of a polar organic co-solvent coupled with subsequent phase splitting induced by dissolution of gaseous CO2. This creates the opportunity to run homogeneous reactions with extremely hydrophobic substrates in an organic/aqueous mixture with a water-soluble catalyst. After C02-induced phase separation, the catalyst-rich aqueous phase and the product-rich organic phase can be easily decanted and the aqueous catalyst recycled. 

It was discovered by Roelen in 1938 and is the oldest and largest volume catalytic reaction of alkenes, with the conversion of propylene to butyraldehyde being the mosi important. About 5 million tons of aldehydes and aldehyde derivatives (mostly alcohols) are produced annually making the process the most important industrial synthesis using a metal carbonyl complex as a catalyst. The name hydroformylation arises from the fact that in a formal sense a hydrogen atom and. formyl group are added across a double bond. The net result of the process is extension of (he carbon chain by one and introduction of oxygen into the molecule. 

Metal-catalyzed reactions of CO with organic molecules have been under investigation since the late 1930s and early 1940s, when Roelen (/) discovered the hydroformylation reaction and Reppe (2) the acrylic acid synthesis and other related carbonylation reactions. These early studies of the carbonyla-tions of unsaturated hydrocarbons led to extremely useful syntheses of a variety of oxygenated products. Some of the reactions, however, suffered from the serious problem that they produced isomeric mixtures of products. For example, the cobalt-catalyzed hydroformylation of propylene gave mixtures of n-butyraldehyde and isobutyraldehyde. 

When P(OPh)3 was used as ligand, the effect of an excess of it on the isomer ratio was far less significant.301 These studies have led to the introduction of an industrial process for the rhodium-catalyzed hydroformylation of propylene to n-butyraldehyde which is rapidly gaining in importance relative to the older, cobalt-catalyzed route. 2,303 The relative merits of the two processes have been discussed.303,304... 

Subsequently, a whole host of both lower (C3, C4, C5) and higher (C5, Cy, C9, C q, C, etc.) oxo alcohols have been commercialized. Of all these alcohols, the most important by far have turned out to be n-butanol and 2-ethylhexanol - both of which are derived from n-butyraldehyde based on hydroformylation of propylene. In addition to n-butyraldehyde, the lower valued isobutyraldehyde is produced as a by-product. Some of this is converted to isobutanol. 

The production of 2-ethylhexanol from propylene by the rhodium catalyzed, low pressure oxo process is accomplished in three chemical steps. The first step of the process (described in section on n-butanol manufacture) converts propylene to normal butyraldehyde by hydroformylation in the presence of a rhodium catalyst. In a second step, the normal aldehyde is aldoled to form 2-ethylhexena1. 2-Ethylhexenal is then hydrogenated to 2-ethylhexanol and refined in the third and final step(see Figure 3). 

The aldehydes commercially produced this way are many. One of the most important is n-butyraldehyde. Isononyl aldehyde is also an important intermediate. As shown by reactions 5.2 and 5.3, propylene is hydroformylated to n-butyraldehyde which is then converted by aldol condensation and hydrogenation to 2-ethyl hexanol. 

In summary, then, in the rhodium-catalyzed industrial process for propylene hydroformylation a high phosphine-to-Rh molar ratio is used. Under these conditions the use of a moderately bulky ligand such as triphenyl phosphine ensures that the catalysis takes place by the topmost cycles in Fig. 5.5, and n-butyraldehyde with high selectivity is produced. 

Assuming that only the reactions shown in Fig. 5.1 operate for the hydroformylation of propylene to n-butyraldehyde with 5.1 as the catalyst, and oxidative addition of dihydrogen is the rate-determining step, what should be the rate expression What is the implicit assumption ... 

The largest volume hydroformylation reaction converts propylene into n-butyraldehyde, from which is made 1-butanol for solvents, or 2-ethylhexanol (the phthalate ester of which has been widely used as a plasticizer for PVC) via an aldol condensation. Estimated world production of butanol is approaching 2 Mt/a. 

Most acetone is manufactured today in the United States by thermochemical cumene oxidation. It is a co-product with phenol. Acetone is also manufactured by dehydrogenation of 2-propanol, which is made by hydration of propylene. Most 1-butanol is manufactured today by hydrogenation of n-butyraldehyde, which is obtained by the hydroformylation of propylene (0x0 reaction). It is also manufactured by hydrogenation of crotonaldehyde, which is obtained by the... 

The most important and oldest application of aqueous biphasic, homogeneous catalysis is hydroformylation (oxo process, Roelen reaction). This process is used to produce n-butyraldehyde, the desired main product of the reaction of propylene, which is converted by aldolization into 2-ethyUiexenal and this is finally hydrogenated to give 2-ethylhexanol (2-EH), the most economically important plasticizer alcohol (Scheme 1) ... 

In what may be another example of true cluster catalysis, [HRu3(CO)i,] , shows catalytic activity for the hydroformylation of ethylene and propylene ". Solvent, CO partial P, and T are important variables. In monoglyme, at 80°C, and starting partial of CjHg, CO and Hj of 0.034, 0.022 and 0.011 MPa, respectively, the catalyst turnover number (mols product/mols catalyst) was 34.3 and the n- to i-butyraldehyde ratio was 49.4/1. In acetonitrile solvent, all other things being equal, the turnover number dropped to 25.7 and the isomer ratio decreased to 12.1/1. 

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