JPS6232179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to a method of making carboxylic acids. More specifically, the present invention relates to a rhodium-catalyzed process for oxidizing aldehydes to produce the corresponding carboxylic acids. Carboxylic acids have many uses in the chemical industry. For example, propionic acid is useful as a grain preservative, and higher acids are used in the manufacture of detergents. Many different methods are known for producing carboxylic acids, such as hydroformylation of olefins and subsequent oxidation of the resulting aldehyde. The acid produced is 1 more than the olefin.
It has a larger number of carbon atoms. For example, olefins (eg, ethylene) are hydroformylated by reaction with carbon monoxide and hydrogen to produce the corresponding aldehyde (propionaldehyde), which is then oxidized to the corresponding acid (propionic acid). In some cases, after the hydroformylation reaction of olefins with carbon monoxide and hydrogen (also known as the oxo process), the aldehyde is recovered and purified before oxidizing it to acid. Other related methods of the prior art do not require purification of the aldehyde. For example, German patent no.
No. 2604545 discloses that the corresponding olefins are hydroformylated under elevated pressures of 100 to 600 bar and the resulting aldehyde-containing reaction mixture is directly oxidized, both steps being carried out in the presence of a rhodium carbonyl complex catalyst. A two-step process for producing alkyl carboxylic acids is disclosed. U.S. Pat. No. 3,980,670 first hydroformylates allyl esters of lower fatty acids in the presence of both a rhodium carbonyl complex catalyst and an inert organic solvent, then directly oxidizes the resulting reaction mixture in the presence of lower fatty acids, and A process is disclosed for simultaneously obtaining both methacrylic acid and butyrolactone by including a rhodium catalyst and recovering the product after separation of the residue. US Pat. No. 3,520,937 discloses a technique for treating a cobalt- and aldehyde-containing oxo reaction mixture with an oxidizing agent to provide a cobalt-free material. The amount of oxygen is said to be insufficient to oxidize the product aldehyde. Still other prior art methods allow for the direct oxidation or carboxylation of olefins to produce various compounds. For example, U.S. Pat.
3384669 for converting olefins to the corresponding aldehydes or ketones by oxidation with molecular oxygen in the presence of a catalyst comprising an aqueous solution containing various noble metal ions and ions of either nitric acid or nitrous acid, or mixtures thereof. Disclose the method. German Patent No. 2744207 discloses the presence of a rhodium complex catalyst and a stabilizing phosphine or phosphite ligand in the absence of an inert solvent and in a reaction medium containing an organic phosphine or phosphite to facilitate product recovery. A method for oxidizing olefins to, for example, ketones by reacting them is disclosed below. US Pat. No. 3,818,060 discloses a Group metal catalyzed hydrocarboxylation process for producing carboxylic acids that involves reacting an olefin with carbon monoxide and water. The catalyst system comprises an iridium or rhodium containing compound, a halide promoter and a stabilizer consisting of an organic derivative of pentavalent phosphorus, arsenic, antimony, nitrogen or bidimus. This stabilizer is said to prevent precipitation and solids build-up, which usually adversely affect the stability of the catalyst. Additionally, U.S. Patent No.
See also 3816488, 3816489 and 3944604. In Tetrahedron Letters No. 38 , pages 3665-3668 (1967), Mr. Blum et al. describe the rhodium complex catalyst chlorotris(triphenylphosphine)rhodium RhCl(PPh ₃ ) ₃ (here, "Ph" = phenyl). The α-oxidation of alkylbenzenes by Specifically, the alkylbenzene ethylbenzene is oxidized to acetophenone by air in the presence of a catalyst. Other than Mr. Fushi, Journal of Organometallic
On pages 417-430 of Chemistry 26 (1971),
A mechanism of cyclohexene oxidation by transition metal complexes is proposed. Specific results have been given for the oxidation of cyclohexene to cyclohexene oxide, cyclohexanone and cyclohexanol in the presence of various catalysts containing rhodium complexed with triphenylphosphine. Takao et al. Journal of the Chemical Society of Japan 43(12) (December 1970)
, pp. 3898-3900 of May), report on the oxidation of the olefin styrene with the rhodium complex chlorotris(triphenylphosphine)rhodium or rhodium chloride and the effects of various solvents on the oxidation products. In non-polar solvents such as toluene, the main products were both acetophenone and benzaldehyde. The oxidation of methylstyrene using the same catalyst has also been reported. Journal of the Chemical Society of Japan, a later report by Takao et al.
45(5) (May 1972), pages 1505-1507, the oxidation of cinnamaldehyde catalyzed by rhodium complexes in various solvents is reported. Two rhodium complexes, chlorocarbonylbis(triphenylphosphine)rhodium and chlorotris(triphenylphosphine)rhodium, cause catalytic oxidation of cinnamaldehyde in toluene to produce benzaldehyde, glyoxal,
It was found to produce benzene and styrene. Also, the Journal of the Chemical Society of Japan 45(7) (July 1972)
On pages 2003-2006, Takao et al. report on the oxidation of vinyl esters in solvents catalyzed by chlorotris(triphenylphosphine)rhodium. The type of reaction product obtained is determined in part by the substituents on the olefinic carbon atoms. For example, vinyl acetate was oxidized in toluene to produce acetone, propionaldehyde, and methyl vinyl ether, whereas vinyl propionate yielded methyl ethyl ketone, butyraldehyde, and ethyl vinyl ether. Mr. Datsudori et al. JCSDalton (1974)
On pages 1926-1931, the rhodium-promoted oxidation of α-olefins to methyl ketones in benzene is disclosed. Two rhodium complexes have been shown to catalyze the reaction: chlorotris(triphenylphosphine)rhodium and carbonylhydridotris(triphenylphosphine)rhodium. Other than Mr. Mercer, Journal of the American
Chemical Society 97(7) (April 1975)
On pages 1967-1968, the rhodium complex Rh ₆
We disclose that (CO) ₁₆ catalyzes the oxidative cleavage of C--C bonds in ketones to carboxylic acids. The particular reaction reported involved suspending rhodium in cyclohexanone as a solvent and pressurizing with oxygen to purify adipic acid. Various other prior art methods disclose hydroformylation processes in which the presence of oxygen retards the reaction. For example, Mr. Polybuka et al. Petrochemia
1979, 19(1-2), 5-12, the rhodium complex catalyst HRh(CO)(PPh ₃ ) ₃ (here,
The low pressure hydroformylation of olefins (1-octene, di- and triisobutylene, allyl alcohol, styrene and dipentene) with "Ph" = phenyl is disclosed. The authors disclose that compounds such as oxygen, which is more reactive towards catalysts than alkenes or CO, form stable complexes that retard hydroformylation. In Journal of the Chemical Society of Japan 19, No. 1 (May 1977), Matsui et al. propose a mechanism to explain the deactivation of rhodium complex catalysts used in hydroformylation reactions. A specific catalyst reported is rhodium (as Rh ₂ Cl ₂ (CO) ₄ ) complexed with a triphenylphosphite ligand. The authors concluded that the deactivation of the catalyst was primarily due to the oxidation of triphenyl phosphate to triphenyl phosphate caused by the small amount of oxygen present in the syngas. The prior art also teaches regenerating deactivated rhodium complex catalysts with oxygen. For example, Japanese Patent Publication No. 51-23212 discloses a rhodium-catalyzed hydroformylation process, more specifically, in which the deactivated rhodium catalyst is treated with oxygen in a separate step and the regenerated catalyst is recycled to the hydroformylation reaction. A technique for regenerating a rhodium catalyst that has become deactivated during the process is disclosed. Currently pending U.S. Patent Application No. 703,130 (published as Belgian Patent No. 856,542) describes the development of a hydroformyl compound that can regenerate a deactivated rhodium complex catalyst by introducing a catalytic small amount of oxygen into the hydroformylation reaction system. Disclose the legal method. The amount of oxygen used is small (i.e., just enough to detoxify and reactivate the catalyst) and substantially all of the oxygen is consumed by the ligands in the catalyst to liberate the catalytic rhodium. , which reactivates the catalyst. Other prior art discloses hydroformylation processes where oxygen is present. For example, U.S. Pat.
No. 3,920,754 discloses a hydroformylation process in which formyl- and hydroformyl-substituted alkene derivatives are formed by reacting an alkene with carbon monoxide and hydrogen in the presence of a free radical initiator (preferably molecular oxygen). US Pat. No. 3,954,877 discloses an olefin hydroformylation process using a complex of a Group metal (eg, rhodium) with a ligand consisting of a pentavalent phosphorous, arsenic, or antimony compound (eg, phosphine oxide). U.S. Pat. No. 3,555,098 discloses a group noble metal that maintains catalyst activity by treating all or a portion of the recycled reaction medium containing the catalyst with an aqueous alkaline solution to extract the carboxylic acid by-product that deactivates the catalyst. A catalytic hydroformylation reaction is disclosed. This acid is believed to be formed by slight oxidation of the aldehyde product due to oxygen contamination of the reactant gas stream. For many years, all industrial hydroformylation reactions used cobalt carbonyl catalysts that required relatively high pressures (often on the order of 100 atmospheres or more) to maintain catalyst stability. U.S. Patent No. 3527809 issued September 8, 1970 to R.L. Brute and G.A. Smith.
No. 1 discloses a novel hydroformylation process in which α-olefins are hydroformylated with carbon monoxide and hydrogen to produce aldehydes in high yields at low temperatures and pressures, in which the normal to iso( or branched) aldehyde isomer ratio is high. This process uses certain rhodium complex catalysts and operates under limited reaction conditions to achieve hydroformylation of olefins. This new process operates at significantly lower pressures than previously required by the prior art, resulting in substantial benefits, including lower initial capital investment and lower operating costs. Furthermore, many desirable linear aldehyde isomers could be produced in high yields. The hydroformylation process described in the Brute and Smith patents mentioned above includes the following essential reaction conditions. (1) A rhodium complex catalyst, which is a complex combination of rhodium, carbon monoxide, and a triorganophosphorous ligand. The term "complex" refers to a combination of one or more electron-rich molecules or atoms that can exist independently.
It refers to a coordination compound formed by the combination of more than one electron-poor molecule or electron, each of which can also exist independently. Triorganophosphorus ligands, where the phosphorus atom has an available or unshared pair of electrons, can form a configurational bond with rhodium. (2) α-olefin feedstock for α-olefin compounds characterized by a terminal ethylenic carbon-carbon bond such as a vinyl group CH ₂ =CH-. They may be straight-chain or branched and may contain groups or substituents that do not essentially interfere with the hydroformylation reaction, and they may contain more than one ethylenic bond. I can do it. Propylene is an example of a preferred α-olefin. (3) Triorganophosphorus ligands such as triarylphosphines. Desirably, each organic moiety in the ligand has no more than 18 carbon atoms. Triarylphosphines are preferred ligands, one example of which is triphenylphosphine. (4) in addition to the ligands complexed with or bound to the rhodium atoms, sufficient triorganophosphorus ligands in the reaction mixture to provide at least 2, preferably at least 5 moles of free ligand per mole of rhodium metal. concentration. (5) A temperature of about 50 to about 145°C, preferably about 60 to about 125°C. (6) Total hydrogen and carbon monoxide pressure below 450 psia, preferably below 350 psia. (7) A maximum partial pressure of carbon monoxide of no more than about 75% based on the total pressure of carbon monoxide and hydrogen, preferably less than 50% of this total gas pressure. In industrial hydroformylation-oxidation processes for producing carboxylic acids, the aldehyde obtained is usually recovered and then oxidized to the corresponding acid. If the oxidation step is carried out without an aldehyde purification step and with a Group metal catalyst such as a rhodium-based catalyst, harsh Catalyst stability and activity problems are encountered. Hydroformylation of olefins to acids - even without the use of inert solvents in the oxidation route, the prior art has divided the process into two steps (i.e., hydroformylation followed by a separate oxidation without purification of the aldehyde). It was necessary to do so. The present invention encompasses a process for producing carboxylic acids by oxidizing aldehydes in the presence of a stable rhodium complex catalyst, wherein the stability and activity of the rhodium catalyst It is maintained by using family ligands. Thus, a catalyst system is provided that is stable under oxidative reaction conditions even in inert organic solvents. The process of the invention allows the production of acids and their anhydrides directly from the corresponding aldehydes in a single operation using a single stabilized catalyst. According to the invention, from 3 to about 21 (or more)
It is possible to produce carboxylic acids having carbon atoms of . Embodiments of the invention include oxidizing an aldehyde to the corresponding acid in the presence of a rhodium complex catalyst, preferably in an inert organic solvent. In this case, the rhodium complex catalyst contains a pentavalent group ligand which stabilizes the catalyst against deactivation. In the process of embodiments of the invention, the aldehyde starting material can be prepared by any suitable means, such as by hydroformylation of the corresponding olefin. The olefins that can be reacted in the hydroformylation process associated with this invention can be any olefins having from 2 to about 20 carbon atoms and one ethylenic carbon-carbon bond. The olefin may be linear or branched and may contain groups or substituents that do not essentially interfere with the progress of the reaction. Additionally, it is intended to include within this scope both alpha-olefins as well as internal olefins. Typical α-olefins include, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1
-undecene, 1-dodecene and higher analogues. The most preferred α-olefin is ethylene. Typical internal olefins include, for example, 2-butene, 2-pentene, 2-
or 3-hexene, 3-decene, 4-decene, 2
- undecene, 3-undecene, 4-undecene, 5-undecene and higher analogs. As previously described, the process is preferably performed in an organic solvent inert to the reaction conditions, preferably with a boiling point at least as high as (but preferably higher than) that of the carboxylic acid produced. It is carried out in some inert aliphatic or aromatic organic solvent. Typical aliphatic inert solvents include saturated hydrocarbons having about 9 to about 20 carbon atoms such as nonane, undecane, dodecane, and the like. These saturated hydrocarbons may be straight chain or branched, and more highly branched materials are preferred. Typical inert aromatic solvents include aromatic hydrocarbons such as benzene and biphenyl, and aromatic hydrocarbons substituted with at least one saturated aliphatic hydrocarbon group such as toluene, xylene, and the like.
Generally, the saturated aliphatic hydrocarbon substituents in these aromatic solvents can contain from 1 to about 15 carbon atoms, and they can be straight or branched. Generally, the type of solvent used is not critical, and the reaction conditions can be adjusted to prevent the solvent from becoming more volatile than the carboxylic acid produced. Optionally, the inert organic solvent may initially contain from 0.5 to 5% by weight of solvent, based on the total weight of the carboxylic acid to be prepared. The amount of acid in the solvent is not particularly critical. This is because, in practice, this is a limitation on how quickly the produced acid is desired to be removed from the reaction system.
By having an acid in the reaction medium at the beginning of the reaction, the formation of the anhydride is promoted more than the acid. The amount of solvent used in the practice of this invention is limited only with respect to the catalyst, ie, it must be such that it solubilizes at least a catalytic amount of rhodium. Generally, the solvent is used to provide a concentration of catalytically active rhodium from about 25 to about 1200 ppm, preferably from about 50 to about 400 ppm, calculated as free metal. Regardless of the amount of solvent or its presence, the catalyst is used in an amount that provides the stated amount of catalytically active rhodium. The pentavalent group rigadone used in the present invention has the formula [In the above formula, R ₁ , R ₂ and R ₃ are each 5
is a straight chain saturated hydrocarbon group containing ~8 carbon atoms]. The most preferred ligand is tri(n-octyl)phosphine oxide. Pentavalent group ligands can be obtained commercially or made by conventional methods. For example, in the case of the preferred ligand tri(n-octyl)phosphine oxide, tri(n-octyl)phosphine is first made by methods known in the art and then treated with an oxidizing agent such as hydrogen peroxide or oxygen. The resulting phosphine oxide can then be recovered. For example, Mr. Harvey et al.'s Journal of the Chemical Society,
See Chemical Communications 369 (1976). The exact nature of the active rhodium complex catalyst species is not known, but it is believed to consist essentially of rhodium stabilized by a pentavalent group ligand. The expression "consisting essentially of" is meant to include rather than exclude other ligands such as hydrogen and carbon monoxide if they are complexed with the rhodium under the reaction conditions. However, this term is meant to exclude amounts of other materials (such as halides and sulfur) that would poison or deactivate the catalyst. What is known is that rhodium is a stable catalyst for the production of carboxylic acids from aldehydes in the presence of pentavalent group ligands. Active rhodium complex catalyst species are free of any rhodium-bonded halogens, such as chlorine and similar species, and are generally stable in hydrogen, carbon monoxide, and possibly liquids that can be used as solvents in the reaction and under the reaction conditions. is theorized to contain a pentavalent ligand complexed with rhodium metal to produce a stable catalyst. The active species, whatever its exact structure, can be obtained by two different techniques. The active rhodium complex catalyst precursor can be preformed and added neat to the aldehyde oxidation reaction mixture, or the necessary rhodium complex catalyst precursor components can be introduced directly into the reaction mixture, but both In the case of , the active rhodium complex catalyst is formed in situ. For example, preforming an active rhodium complex catalyst precursor in solution by combining a rhodium compound such as rhodium dicarbonylacetylacetonate and a suitable pentavalent ligand such as tri(n-octyl)phosphine oxide. I can do it. This precursor solution can then be added to the aldehyde oxidation reaction mixture to form an active rhodium complex catalyst in situ. Alternatively, the required active rhodium catalyst precursor components, i.e. rhodium dicarbonylacetylacetonate or Rh ₄ (CO) ₁₂ or
Rhodium compounds such as Rh ₆ (CO) ₁₆ and tri(n
A pentavalent ligand such as -octyl)phosphine oxide is added neat to the aldehyde oxidation reaction mixture. In either case, the active rhodium complex catalyst species is formed in situ and under the conditions present in the reaction medium. The latter technique, i.e.
A preferred technique is to form an active rhodium complex catalyst species by adding a rhodium compound and a ligand to the reaction medium. The pentavalent group ligand stabilizes the catalyst against deactivation, regardless of its method of formation, and generally contains from about 0.0008 to about 0.08 mole in the liquid reaction medium based on the total liquid reaction medium volume. added in an amount sufficient to provide a concentration of The process can be carried out continuously or batchwise or semi-batchwise. In any case, it is sometimes necessary to recharge the system with catalyst components. Whether it is necessary depends on several factors, including the desired reaction rate, amount of reaction medium, reaction conditions, etc. The catalyst or components thereof can be added to the reaction medium by any suitable technique such as those described above for initial catalyst loading. The carboxylic acid produced can be recovered by any suitable conventional technique, such as by distillation or extraction. Embodiments of the invention include the direct oxidation of aldehydes to carboxylic acids having the same number of carbon atoms as the aldehyde. This reaction (herein, for convenience,
The aldehyde oxidation reaction) is carried out in the presence of a rhodium complex catalyst containing a pentavalent group ligand. The starting aldehyde can be obtained by any suitable technique, such as by hydroformylation of the corresponding olefin. Although the aldehyde can have from 3 to about 21 carbon atoms in accordance with the present invention, the preferred aldehyde is propionaldehyde, which is processed according to this embodiment to produce propionic acid. The aldehyde oxidation reaction generally oxidizes an aldehyde to its corresponding acid by supplying an oxygen-containing gas such as air or dilute oxygen into a liquid reaction medium containing at least a starting aldehyde and a rhodium complex catalyst. be carried out for a sufficient period of time. The reaction can be carried out at about atmospheric pressure, but it is preferred to use a substantially constant pressure of about 1 to 2 atmospheres above atmospheric pressure. This is because the catalyst is more stable at these pressures compared to its stability at atmospheric pressure. It is to be understood that oxygen can become explosive at pressures substantially higher than atmospheric pressure and therefore such pressures should be avoided. Generally, the maximum reaction pressure is approximately
100 psig. The aldehyde oxidation reaction is preferably carried out in an inert organic solvent, in which case the liquid reaction medium initially contains the aldehyde, the inert organic solvent and the rhodium complex catalyst. As the reaction progresses, the aldehyde content will of course decrease as acid is formed. The inert organic solvent is as described above. The aldehyde oxidation reaction takes place at temperatures ranging from approximately room temperature to approximately 100°C.
It can be carried out at temperatures up to When the temperature exceeds about 100°C, it is necessary to pay attention to the safety of the reaction.
This is because oxygen tends to become explosive with increasing temperature. Additionally, although the reaction rate generally decreases with decreasing temperature, there is no critical factor determining the minimum reaction temperature. Preferred reaction temperatures are from about 40°C to about 90°C, and higher temperatures generally result in higher reaction rates. The oxygen-containing gas supplied to the liquid reaction medium generally contains about 2 to 100% by volume oxygen. Typically, this gas stream consists of pure oxygen diluted with air or nitrogen, and although it is possible and desirable to use a stoichiometric excess of oxygen to the aldehyde, using too much excess There is no profit whatsoever. Again, the maximum amount of oxygen in the gas stream supplied to the liquid reaction medium is determined primarily by safety considerations, taking into account the reaction temperature and pressure. It has been found that rhodium catalysts are more stable when carbon monoxide is also present in the reaction medium in up to approximately equimolar amounts based on air as the oxygen source, and this is therefore preferred. Conventional techniques such as those described above can be used to recover the carboxylic acid product and remove unwanted by-products from the reaction medium. In addition, the aldehyde oxidation reaction can be carried out continuously or batchwise or semi-batchwise, if desired. Also, all conventional equipment can be used in embodiments of the invention. In embodiments of the invention, at least one of carboxylic acids and their anhydrides can be produced, ie, individually or as a mixture. Of course, the anhydride can be converted to its acid form by conventional techniques such as by hydrolysis. The invention is further illustrated by the following examples:
Some of these represent methods outside the scope of the present invention for comparison. Example 1 (Reference example) Solvent and ligand are added to a 3L rotucone container.
0.12 g of rhodium dicarbonylacetylacetonate Rh(CO) ₂ AcAc and 100 psi of ethylene.
A mixture of 100 psi carbon monoxide and 100 psi hydrogen (total gas pressure 300 psia) was charged at an initial charge temperature of 30-35°C. The system was then heated to 100 ± 3 °C (unless otherwise noted), the system was maintained under these conditions for 4.5-5.5 h by starting the rocker and repressurizing with gas as needed, and brought to 25 °C. Cooled, degassed, and the liquid contents were removed and analyzed by gas phase chromatography (VPC) to determine the yield of propionaldehyde. The conditions and results are shown in Table 1 below. Although these experiments are not within the scope of the present invention, they
It is illustrated that under hydroformylation conditions, as opposed to trivalent Group A ligands, their pentavalent analogues appear to work effectively in the inert solvent toluene rather than acetophenone. [Table] Example 2 (Reference example) The solvent (500 ml in total) was changed and di(rhodium dicarbonylacetate) (Rh(CO) ₂ OAc) was used as the rhodium precursor instead of rhodium dicarbonylacetylacenate in experiment 26. The procedure of Example 1 was repeated except that ₂ was used. material,
The conditions and results are shown in Table 2 below. None of these experiments fall within the scope of the present invention, however, they do show the effect of various solvents on pentavalent phosphine oxide under hydroformylation conditions. [Table] [Table] Example 3 (Reference Example) The procedure of Example 1 was followed except that the ligands shown in Table 3 below were used. Upon completion of the reaction,
The amount of rhodium still retained in the liquid reaction medium was determined by atomic absorption and is shown in Table 3.
Shown as Rh%. The conditions and results are shown in Table 3 below. Although none of these experiments fall within the scope of the present invention, they demonstrate the effect of pentavalent ligands on the stability of rhodium. [Table] Example 4 A 0.1 fisherman equipped with an electromagnetic stirrer.
In a Porter bottle, 70 c.c. of toluene (blank experiment) or 8.29 g of triphenylphosphine oxide (TPPO) was dissolved in 90 g of toluene.
20ml of a saturated solution of cc, 200mg of rhodium dicarbonylacetylacetonate (Rh(CO) _2AcAc )
of solution in toluene, 5 g of propionaldehyde and 0.5 g of acetic acid. The system was then heated to 50 ± 3 °C using an oil bath and initially a CO:air mixture (1:
1 volume ratio) to 75 psia. This temperature and pressure of 60-75 psia was maintained for 3.25 hours by periodic repressurization with the same CO:air mixture, then the pressure was allowed to drop overnight. The system was then repressurized again to 70 psia and heated to a temperature of 52±3°C. This temperature was maintained for 4.5 hours, during which time the pressure was allowed to drop, after which the system was allowed to cool to room temperature, degassed, the liquid contents were removed, and
Propionic acid (EtCO ₂ H) analyzed by VPC
The yield of rhodium was obtained and the amount of rhodium retained in solution by atomic absorption was determined. Comparable amounts of propionic acid were obtained in each experiment based on total product. The results are shown in Table 6 below. experiment
Run No. 46 is outside the scope of the present invention due to the absence of a pentavalent ligand, whereas Experiment No. 47 exemplifies a specific example of aldehyde oxidation of the present invention. [Table] Example 5 Add 200 g of rhodium carbonyl triphenylphosphine acetylacetonate Rh to the same 0.1 Fisher Porter Bolt used in Example 4.
(CO)(TPP)AcAc, 50 ml toluene (PhCH ₃ ) and 5 g tri(n-octyl)phosphine oxide or 5 g additional toluene (blank experiment) with 5 g propionaldehyde and 100 g acetic acid. I prepared it. The system was then charged with 30 psi of oxygen and it was heated to 40±2° C. in an oil bath. The reaction solution was stirred and the gas pressure was maintained for 28 hours by periodic addition of oxygen (experiment no.
50 and 51 were maintained at 25° C. for 48 hours under the same gas pressure). Samples were taken at various times and treated with propionic acid, EtCO ₂ H by VPC.
and propionic anhydride (EtCO) ₂ O and obtained the amount (%) of rhodium retained in solution by atomic absorption. The conditions and results are shown in Table 5 below. Experiments No. 49 and 51 are outside the scope of the present invention since no pentavalent ligand was present, whereas Experiments No. 48 and 50 illustrate specific examples of aldehyde oxidation of the present invention. TABLE It is to be understood that the above description is merely illustrative of the invention and that various changes and modifications of the invention will be apparent to those skilled in the art. It is further understood that such changes and modifications are intended to be included within the spirit and scope of the purpose of this application and the claims.

Claims (1)

[Claims] 1 formula [In the above formula, R ₁ , R ₂ and R ₃ are each 5
3 to 3 in the presence of a rhodium complex catalyst consisting essentially of rhodium stabilized by a pentavalent Group V ligand represented by An aldehyde containing about 21 carbon atoms is mixed with an oxygen-containing gas from about 40 to about
A process for producing at least one of carboxylic acids and their anhydrides, comprising reacting and oxidizing at a temperature of 90° C. and a supernormal pressure of about 1 to about 2 atmospheres (gauge). 2. The method according to claim 1, wherein the pentavalent Group V ligand is trioctylphosphine oxide. 3. The method according to claim 1, wherein the reaction is carried out in an inert organic solvent. 4. The inert organic solvent is a saturated aliphatic hydrocarbon having about 9 to about 20 carbon atoms, benzene, and 1
4. The method of claim 3, wherein the aromatic hydrocarbon is selected from the group consisting of aromatic hydrocarbons substituted with at least one saturated aliphatic hydrocarbon group having from about 15 carbon atoms. 5 The concentration of catalytically active rhodium in the solvent is about 25 to about 1200 ppm calculated as free metal.
The method according to claim 3, wherein: 6. The method of claim 3, wherein the concentration of the ligand in the liquid reaction medium is from about 0.0008 to about 0.008 molar based on total liquid reaction medium. 7. The method of claim 3, wherein the reaction is carried out at a substantially constant pressure of about 1 to about 2 atmospheres (gauge) and in the presence of carbon monoxide. 8 The aldehyde is propionaldehyde,
4. The method of claim 3, wherein the acid is propionic acid and the anhydride is propionic anhydride. 9. The method according to claim 8, wherein the inert organic solvent is toluene. 10. The method according to claim 9, wherein the pentavalent vicinal ligand is trioctylphosphine oxide.