Hydroformylation of ethylene

MMA and MAA can be produced from ethylene [74-85-1/ as a feedstock via propanol, propionic acid, or methyl propionate as intermediates. Propanal may be prepared by hydroformylation of ethylene over cobalt or rhodium catalysts. The propanal then reacts in the Hquid phase with formaldehyde in the... 

Ligand-Modified Rhodium Process. The triphenylphosphine-modified rhodium oxo process, termed the LP Oxo process, is the industry standard for the hydroformylation of ethylene and propylene as of this writing (ca 1995). It employs a triphenylphosphine [603-35-0] (TPP) (1) modified rhodium catalyst. The process operates at low (0.7—3 MPa (100—450 psi)) pressures and low (80—120°C) temperatures. Suitable sources of rhodium are the alkanoate, 2,4-pentanedionate, or nitrate. A low (60—80 kPa (8.7—11.6 psi)) CO partial pressure and high (10—12%) TPP concentration are critical to obtaining a high (eg, 10 1) normal-to-branched aldehyde ratio. The process, first commercialized in 1976 by Union Carbide Corporation in Ponce, Puerto Rico, has been ficensed worldwide by Union Carbide Corporation and Davy Process Technology. 

Propanol has been manufactured by hydroformylation of ethylene (qv) (see Oxo process) followed by hydrogenation of propionaldehyde or propanal and as a by-product of vapor-phase oxidation of propane (see Hydrocarbon oxidation). Celanese operated the only commercial vapor-phase oxidation faciUty at Bishop, Texas. Since this faciUty was shut down ia 1973 (5,6), hydroformylation or 0x0 technology has been the principal process for commercial manufacture of 1-propanol ia the United States and Europe. Sasol ia South Africa makes 1-propanol by Fischer-Tropsch chemistry (7). Some attempts have been made to hydrate propylene ia an anti-Markovnikoff fashion to produce 1-propanol (8—10). However, these attempts have not been commercially successful. 

Propanediol is a colorless liquid that boils at 210-211°C. It is soluble in water, alcohol, and ether. It is an intermediate for polyester production. It could be produced via the hydroformylation of ethylene oxide which yields 3-hydroxypropionaldehyde. Flydrogenation of the product produces 1,3-propanediol. 

The catalyst formed in this manner exhibited carbonyl infrared absorptions, as shown in Table XXX. These catalysts were tested by hydroformylation of ethylene or propylene at 100°C and atmospheric pressure. Both were effective, with (A) being better than (B), probably because of the higher surface area. The aldehyde formed from propylene was a mixture of 63% n- and 37% isobutyraldehyde. The rate expression for ethylene hydroformylation was ... 

The potential energy surface for the hydroformylation of ethylene has been mapped out for several catalytic model systems at various levels of theory. In 1997, Morokuma and co-workers [17], considering HRh(CO)2(PH3) as the unsaturated catalytic species that coordinates alkene, reported free energies for the full catalytic cycle at the ab initio MP2//RHF level. Recently, in 2001, Decker and Cundari [18] published CCSD(T)//B3LYP results for the HRh(CO)(PH3)2 catalytic complex, which would persist under high phosphine concentrations. Potential energy surfaces for both Rh-catalyzed model systems were qualitatively very similar. The catalytic cycle has no large barriers or deep thermodynamic wells to trap the... 

Despite this setback, this catalyst system could also be used for the hydroformylation of ethylene and indeed the long-term stability of the catalyst was found to be better than that of the catalyst derived from triphenylphosphine. Hence, this catalyst system allowed the hydroformylation of both high and low molecular weight alkenes under homogeneous conditions combined with facile product separation by simple decantation. 

In CO hydrogenation, the achvity and selechvity to C1-C5 oxygenates over the bimetallic samples are higher than those of the monometallic counterparts [187-190]. Bimetallic catalysts also showed improved activity in the hydroformylation of ethylene compared to either of the monometallic catalysts [191]. The promotion for higher alcohol production is proposed to be associated with the adjacent Ru-Co sites. However, the lack of an exhaustive characterization of catalysts does not allow a clear correlation to be established between the characteristics of the active sites and the catalytic behavior. A formyl species bonded to a Ru-Co bimetallic site has been proposed to be the intermediate in the alcohol synthesis in these systems. A subsequent reaction with an alkyl-surface group would lead to the C2-oxygenate production [187]. 

The catalyst recovery problem has been approached in various other ways. The application of heterogeneous catalysts offers a possible solution.225 Heterogeneous catalysts, such as highly dispersed Rh on Si02226 and Co on Si02,227 show high activity in the gas-phase hydroformylation of ethylene. 

Further novel observations are the hydroformylation of ethylene over graphite nanofiber-supported Rh catalysts,270 the transformation of a mixture of isomeric octenes to Cg-aldehydes,271 and the preparation of linear long-chain dialdehydes by the hydroformylation of linear a,co-dienes.272... 

Ab initio molecular orbital studies on the whole catalytic cycle of hydroformylation of ethylene catalyzed by HRh(CO)2(PH3)2 has been performed [59,60], which points out the significance of the coordinating solvent—ethylene in this case—and identifies the oxidative addition of molecular hydrogen to the pentacoordinate acyl-Rh complex as the rate-determining step. In fact, this step is the only endothermic process in the catalytic cycle. 

In this last section we wish to illustrate the use of TAMREAC with three examples. The first, ethylene dimerization, is of importance since it is involved in the oligomerization and polymerization reactions of olefins. The second example concerns the hydroformylation of ethylene, and the last example is the allyl—alkyl coupling reaction induced by a Ni(II) complex. 

Other Uses of Ethylene Oxide. About 2 percent of ethylene oxide is consumed in miscellaneous applications, such as its use as a raw material in manufacture of choline, ethylene chlorohydrin, hydroxyethyl starch, and hydrox-yethyl cellulose and its direct use as a fumigant/ sterilant. Production of 1,3-propanediol via hydroformylation of ethylene oxide was begun on a commercial scale in 1999. 1,3-Propanediol is a raw material for polytrimethylene terephthalate, which finds uses in fibers, injection molding, and in film. Use of ethylene oxide in making 1,3-propanediol is expected to be as much as 185 million lb by 2004, up from 12 million lb in 1999. 

Ans. (a) Hydroformylation of ethylene, followed by alcohol condensation, followed by hydrogenation (b) hydroformylation followed by hydrogenation (c) hydroformylation followed by oxidation (d) hydroformylation followed by carbonylation. 

Suggest an isotope-labeling experiment for characterization of the catalytic intermediate, observed by in situ IR in the hydroformylation of ethylene by cobalt carbonyl. 

Indeed, this has been realised and BASF started a plant on a 5000ton/year scale in 1989 [81, 82]. The process is based on the hydroformylation of ethylene. Subsequently the propanal is converted via a Mannich reaction into methacro-lein, oxidation and esterification then leads to MM A (Scheme 5.45). 

Other routes to MMA start from ethylene, propylene or propyne and involve metal catalysis at some stage of multi-step transformations for example by the hydroformylation of ethylene to intermediate propionaldehyde, oxidation to propionic acid, followed by condensation with formaldehyde. The Pd-catalyzed carbonylation of propyne to MMA is a further method. However only the ethylene route has found some industrial application (see Chapter 4, Section 4.3.1). 

Scheme 4 shows a platinum catalyst 1 containing such a bis-SPO bidentate ligand anion, designed for the hydroformylation of ethylene and of 1-heptene, and various other, similarly built, platinum catalysts. Catalyst 1 has an activity comparable to that of the commercial cobalt catalysts that were used at the time and displays a higher selectivity for linear products than the cobalt-containing catalysts (66). Like the latter, the platinum complex exhibits hydrogenation activity to give, in part, alcohols in addition to aldehydes and also produces alkanes (an undesired reaction that implies a loss of feedstock). The catalysts are also active for isomerization, as are the cobalt complexes, and for internal heptene hydroformylation (Table 1), with formation of 60% linear products. 

The use of chiral SPOs in the hydroformylation reaction failed to lead to enantiomeric excess in the hydroformylation of styrene (72), a result that was surprising because the complexes otherwise behave like classic diphosphine catalysts, among which are highly enantioselective catalysts. Most likely, racemization of the chiral SPO had occurred. The catalytic hydroformylation of ethylene leads to mixtures of propanal, the expected product, and 3-pentanone. 

Ichikawa (98) has reported that ZnO-supported Rh4 Rh,3 carbonyl clusters exhibit marked catalytic activities for hydroformylation of ethylene and propene ... 

Hydroformylation of Ethylene on Surface-Deposited Ru Ketenylidene Cluster Catalysts"... 

Atmospheric pressure hydroformylation of ethylene and propene was conducted at 373-453 K on reduced [Rh5]-NaY and RhFe-NaY. The results show that acetaldehyde is catalytically obtained as the hydroformylation product on [Rhg]-NaY (142). In contrast, it is of interest to find that the bimetallic RhFe-NaY catalyst gives much higher activities and selectivities for the normal alcohols, as compared to those on [Rhg]-NaY. In particular. 

Over recent years a steady and continuous growth in production capacity of aldehydes by the hydroformylation reaction has taken place. Table 3 shows the estimated capacities for aldehydes generated by hydroformylation of ethylene, propene, and higher olefins, along with their regional distribution [143]. 

In the case of the cluster anion [HRu3(CO)i,j as hydroformylation catalyst, indirect evidence has been put forward for catalysis by intact trinuclear ruthenium clusters. The catalytic cycle proposed for the hydroformylation of ethylene by this cluster anion (55) is based on the isolation of the protonation product of the intermediate 56 in addition to isotope labeling studies 234) (Scheme 11). It is assumed that 55 is attacked by ethylene at the bridging carbon atom, possibly via an intermediary i/2-eth-... 

Scheme 11. Catalytic cycle proposed for the hydroformylation of ethylene, catalyzed by the cluster anion [HRu3(CO)u], according to (234). [From G. Sttss-Fink and F. Neumann, in The Chemistry of the Metal-Carbon Bond (F. R. Hartley, ed.), Vol. 5, p. 305. Wiley, New York, 1989. Reprinted by permission of John Wiley Sons, Ltd.]...

In the presence of alkali metal halides or iodine as promoters for the hydroformylation of ethylene catalyzed by [HRu3(CO)n]-, however, kinetic studies indicate that mono- and dinuclear species are responsible for the catalytic activity under these conditions (236). This is in line with reactivity studies involving [HRu3(CO)u]-, [HRu(CO)4]-, [Ru(CO)3I], and Ru(CO)4I2 (237). 

---