Propylene, rhodium-catalyzed

Kvaerner Process Technology/ Union Carbide Corp. 2-Ethylhexanol Propylene Rhodium-catalyzed, low pressure oxo process high efficiency with minimal coproducts 14 1997... 

The stringency of the conditions employed in the unmodified cobalt 0x0 process leads to formation of heavy trimer esters and acetals (2). Although largely supplanted by low pressure ligand-modified rhodium-catalyzed processes, the unmodified cobalt 0x0 process is stiU employed in some instances for propylene to give a low, eg, - 3.3-3.5 1 isomer ratio product mix, and for low reactivity mixed and/or branched-olefin feedstocks, eg, propylene trimers from the polygas reaction, to produce isodecanol plasticizer alcohol. 

Fig. 4. Mechanism for the TPP-modified rhodium-catalyzed oxo reaction of propylene to -butyraldehyde.

Another route to the diol monomer is provided by hydroformylation of allyl alcohol or allyl acetate. Allyl acetate can be produced easily by the palladium-catalyzed oxidation of propylene in the presence of acetic acid in a process similar to commercial vinyl acetate production. Both cobalt-and rhodium-catalyzed hydroformylations have received much attention in recent patent literature (83-86). Hydroformylation with cobalt carbonyl at 140°C and 180-200 atm H2/CO (83) gave a mixture of three aldehydes in 85-99% total yield. 

For the rhodium-catalyzed hydroformylation of propylene in an aqueous biphasic system. Cents et al. have shown that the accurate knowledge of the mass transfer parameters in the gas-liquid-liquid system is necessary to predict and optimize the production rate [180]. Choudhari et al. enhanced the reaction rate by a factor of 10-50 by using promoter Ugands for the hydroformylation of 1-octene in a biphasic aqueous system [175]. 

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. 

Fig. 5. Plot of log(rates) vs. log(pressure) for rhodium-catalyzed CO hydrogenation. Reaction conditions 75 ml sulfolane, 3 mmol Rh, 1.25 mmol pyridine, H2/CO = 1, 240 C, 4 hr (96). Total rate includes rates to methanol, methyl formate, ethanol, ethylene glycol monoformate, and propylene glycol ( ) total ( ) methanol ( ) ethylene glycol. Open figures are for an experiment with H2/CO = 0.67.

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... 

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). 

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. 

Application To produce normal and iso-butyraldehyde from propylene and synthesis gas (CO + H2) using the LP Oxo SELECTOR Technology, utilizing a low-pressure, rhodium-catalyzed oxo process. 

The rhodium-catalyzed addition of ethylene to 1,3-butadiene to yield 1,4-hexadiene (5a, 151) proceeds via a similar mechanism (151) with the exception that, upon formation of the alkylrhodium(III) species, the hexadiene synthesis proceeds without further change in the oxidation state of the metal. In these reactions with butadiene the coordinated alkyl groups are either chelate or 7r-allyl structures which appear to stabilize Rh(III) (151). The addition of propylene to butadiene and isoprene to produce [Pg.297]

A plausible mechanism was reported for the catalytic formation of benzene resulting from phosphorus-carbon bond cleavage which occurs during propylene hydroformylation catalyzed by triphenylphos-phine-substituted rhodium carbonyls under higher H2 partial pressures (Scheme 37). " ... 

It has been known for many years that transition metals catalyze reactions of coordinated phosphines (2). Known reactions of phosphines as ligands include carbon-hydrogen lx)nd cleavage (cyclometalation), as well as direct carbon-phosphorus bond cleavage. Such metal-catalyzed reactions of phosphines lead to formation of new metal complexes which can affect catalyst properties. A known example is the reaction of triphenylphosphine to propyldiphenylphosphine during the rhodium-catalyzed propylene hydrogenation or hydroformylation (5). 

During a study of this reaction, we observed a surprisingly facile rhodium-catalyzed interchange of aryl groups of tertiary phosphines (4). Thus we observed that during rhodium-catalyzed propylene... 

Scheme 1. Rhodium catalyzed aryl-aiyl and aryl-propyl interchange between tertiary phosphines during propylene hydrogenation. (Conations 130°C, 2.5 hours 1000 ppm Rh as Rh(CO)2acetylacetonate 2.5 wt. percent each triphenylphosphine and tris-para-tolylphosphine 100 psia H2 propylene toluene solvent.)...

The analogous phenomenon was first reported by Bergbreiter etal. [17, 18]. In the presence of phosphorus-bonded block copolymers of ethylene oxide and propylene oxide as ligands ( smart ligands ), rhodium-catalyzed hydrogenation of maleic acid or allyl alcohol in the aqueous phase would show the same anti-Arrhenius reactivity. 

Also homogeneous hydroformylation catalysts are able to degrade triarylphos-phines. Gregario et al. noted that, during the rhodium-catalyzed hydroformylation of propylene, PPhj was slowly converted into PPhgPr [194]. 

In the course of the rhodium-catalyzed hydroformylation, metal diarylphos-phides can be alkylated to give alkyldiarylphosphines. For example, with propylene as substrate, propyldiphenylphosphine, benzene, and benzalde-hyde were formed (Scheme 2.58) [96b]. Propyldiphenylphosphine and... 

Synthesis of Benzyl 2-Silyl-2-diazoacetates. Bolmetal. synthesized benzyl 2-dimethylthexylsilyl-2-diazoacetate from benzyl 2-diazoacetate with TDSOTf in the presence of ethyldiiso-propylamine in Et20 in 86% yield after column chromatography (eq 20). In contrast to other benzyl 2-silyl-2-diazoacetates, an attempt to prepare the corresponding benzyl 2-dimethylthexyl-silyl-2-oxoacetate via rhodium-catalyzed reaction of benzyl 2-dimethylthexylsilyl-2-diazoacetate with propylene oxide failed because of steric hindrance, forming a silacyclobutane via intramolecular C-H insertion reaction. 

Two-phase, or biphasic, catalysis has gained increasing attention over the past two decades. One driving force undoubtedly was the successful implementation of large-scale applications in industry. Rhodium-catalyzed aqueous biphasic propylene hydroformylation, performed by the Ruhrchemie/Rhone-Polenc process, represents the most important carbonylation reaction today, with a total outcome of more than... 

The unmodified rhodium-catalyzed hydroaminomethylation of 1-octene and morpholine was investigated in ternary thermophoric solvent systems [26]. Therefore, hexane or dodecane, together with propylene carbonate and a mediator solvent, provided complete miscibility at the desired reaction temperature of 125 °C. N- and iso-N-nonylmorpholine products adopted the nonpolar phase after cooling and could be separated (Scheme 5.8). Applying a 1-octene/morpholine ratio of 1.5,96% amine selectivity was the highest achieved in the PC/dodecane/l,4-dioxane (1 0.55 1.3, volume ratio) polar/nonpolar/mediator solvent system. Rhodium loss was measured by ICP-OES to be less than 1.5% and was correlated to the mediator solvent polarity. 

The rhodium-catalyzed hydroaminomethylation of 1-octene with morpholine was studied using temperature-dependent solvent systems consisting of propylene carbonate, an alkane, and a semipolar mediator such as N-octylpyrrolidone. The conversion of 1-octene and the selectivity to the corresponding amine is 92%. After the reaction, the catalyst can be easily recovered by a simple phase separation with only a negligible loss of rhodium [167]. 

Complex (23) also catalyzes reaction (147). In addition to the products (120)-(122), the diformate ester of 1,2-propylene glycol was also formed.582 Other epoxides were studied and the complex [CoCl(PPh3)3] catalyzed the formation of the lactone (122) only. Formate complexes were believed to be present, resulting from the insertion of C02 into a rhodium-hydride bond (equation 149). The formate complex then initiates the catalytic cycle. The general mechanism given in Scheme 54 was proposed for the reaction. 

Kuntz subsequently showed that the RhCl (tppts) 3 catalyzed the hydroformylation of propylene in an aqueous biphasic system [29]. These results were further developed, in collaboration with Ruhrchemie, to become what is known as the Ruhrchemie/Rhone-Poulenc two-phase process for the hydroformylation of propylene to n-butanal [18, 19, 22, 30]. Ruhrchemie developed a method for the large scale production of tppts by sulfonation of triphenylphosphine with 30% oleum at 20 °C for 24 h. The product is obtained in 95% purity by dilution with water, extraction with a water insoluble amine, such as tri(isooctylamine), and pH-controlled re-extraction of the sodium salt of tppts into water with a 5% aqueous solution of NaOH. The first commercial plant came on stream in 1984, with a capacity of 100000 tons per annum of butanal. Today the capacity is ca. 400000 tpa and a cumulative production of millions of tons. Typical reaction conditions are T=120°C, P=50bar, CO/H2 = 1.01, tppts/Rh = 50-100, [Rh] = 10-1000 ppm. The RhH(CO) (tppts)3 catalyst is prepared in situ from e.g. rhodium 2-ethylhexanoate and tppts in water. 

Copper compounds are catalysts for the Michael addition reaction (249), olefin dimerizations (245, 248), the polymerization of propylene sulfide (142), and the preparation of straight-chain poly phenol ethers by oxidation of 2,6-dimethylphenol in the presence of ethyl- or phenyl-copper (209a). Pentafluorophenylcopper tetramer is an intriguing catalyst for the rearrangement of highly strained polycyclic molecules (116). The copper compound promotes the cleavage of different bonds in 1,2,2-tri-methylbicyclo[1.1.0]butane compared to ruthenium or rhodium complexes. Methylcopper also catalyzes the decomposition of tetramethyllead in alcohol solution (78, 81). 

The hydroformylation of alkenes is commonly run using soluble metal carbonyl complexes as catalysts but there are some reports of heterogeneously catalyzed reactions of olefins with hydrogen and carbon monoxide. Almost all of these are vapor phase reactions of ethylene or propylene with hydrogen and carbon monoxide catalyzed by rhodium, " 20 ruthenium,nickel, 22,123 cobalt, 23,124 and cobalt-molybdenum 23 catalysts as well as various sulfided metal catalysts. 23,125,126... 

Rhodium trichloride catalyzes the addition of ethylene or propylene to a conjugated diene such as butadiene-1,3, for example 1... 

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