JPH0566179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for oxidizing and regenerating palladium using an oxygen complex, and particularly to a method for rapidly oxidizing and regenerating Pd(0) using an oxygen complex. (Prior Art) As an example of the oxidation reaction of various olefins that has been carried out industrially in the past, there is the Hoechst-Watzka method (Japanese Patent Publications Nos. 36-1475 and 36-7869). This method uses a composite catalyst in which catalysts Pd(2)Cl ₂ and Cu(2)Cl ₂ are dissolved in an aqueous hydrochloric acid solution (PH: 0 to 2). For example, to explain the oxidation reaction of ethylene, first, ethylene is oxidized by Pd(2)Cl ₂ to produce acetaldehyde. The reaction is shown by the following formula. CH ₂ = CH ₂ + Pd (2) Cl ₂ + H ₂ O → CH ₃ CHO+
Pd(0)↓＋2HCl (1) Here, the ring element Pd(0) is mixed with a large amount of Cu(2)Cl ₂
Pd(2) is oxidized and regenerated into Cl ₂ . Pd (0) + 2Cu (2) Cl ₂ → Pd (2) Cl ₂ + 2Cu (1)
Cl ₂ (2) At this time, poorly soluble Cu(1)Cl produced as a by-product is oxidized with oxygen according to the following formula in the coexistence of HCl and returned to Cu(2)Cl ₂ . 2Cu(1)Cl+1/2O ₂ +2HCl→2Cu(2)Cl ₂ +
H ₂ O (3) also in the presence of sodium acetate in acetic acid solvent,
There is also a method to synthesize vinyl acetate from ethylene and acetic acid.
Pd(2) _Cl2 is used as an oxidizing agent (JJ
Moiseau et al., Doklady.Akad.Nauk SSSR.
133, 377 (1960). This stoichiometric acetoxylation becomes a catalytic process in the presence of a redox system that can regenerate Pd(2)Cl ₂ (reaction equations (2) and (3)). In this way, in the oxidation reaction of olefin, Pd(2)
Pd(2)Cl ₂ is used as a salt, while Pd(2)Cl ₂ is also used for oxidative carbonylation of olefins, oxidation of aromatic compounds, or oxidative carbonylation reactions, but generally the reaction conditions are There is a problem that the response rate is becoming more difficult and the response rate is low (Tamura,
Catalyst, 21 , 168, 379 (1979)). Therefore, we investigated the oxidation of aromatic compounds using Pd(2)(CHCOO) ₂ in acetic acid solvent (R. van Helden et al.
al., Rec.Trav.Chim.Pays−Bas. 8 , 1263 (1965)
Alternatively, attempts to perform oxidative carbonylation have been considered, but this is a stoichiometric reaction and has the problem that oxidative regeneration of Pd(0) is difficult. (Problems to be Solved by the Invention) The purpose of the present invention is to solve the problem under mild conditions in an acetic acid solvent.
An object of the present invention is to provide a method for oxidizing and regenerating Pd(0). [Means for Solving the Problems] In short, the present invention provides Pd reduced in an acetic acid solvent by oxygen activated by coordinating to a transition metal.
This is a method of oxidizing and regenerating (0) to Pd(2) (CH ₃ COO) ₂ . That is, the present invention provides palladium Pd
In the method of oxidizing and regenerating (0) with an oxidizing agent in an acetic acid solvent, the oxidizing agent is a complex (MmXn・Ll) that can form an oxygen complex by coordinating with oxygen (where M is a member of the periodic group , a transition metal belonging to the iron group of group ~ or group X
is a halogen ion of Cl ^- , Br ^- , I ^- or BF ₄ ^- ,
Anions such as PF ₆ ^- and SO ₄ ^2- , the ligand L is an organic phosphorus compound, nitriles, m and n are constants determined by the valence balance, and l indicates the coordination number) are used. Features. The present inventors previously demonstrated that the oxygen complex formed by coordinate bonding of oxygen to a transition metal complex is Pd(0).
discovered that it has the ability to efficiently oxidize and regenerate olefin into Pd( ₂ )Cl2, and proposed a process for oxidizing olefin under mild conditions in a water-containing mixed solvent (Japanese Patent Application No. 122600/1986, 60 −8862). The present inventors oxidized and regenerated the reduced Pd(0) to produce Pd
(2) In order to obtain (CH ₃ COO) ₂ , we investigated using the above oxygen complex and acetic acid as a solvent.
(0) is quickly oxidized to Pd(2) (CH ₃ COO) ₂
The present invention was achieved by discovering that. That is, if we describe it as a typical example, this reaction will be as shown in the following formula (5). Pd(0)+1/2(Cu(1)Cl・L ₁ ) ₂・O ₂ +
2CH ₃ COOH+L ₁ +L ₂ →Pd(2)(CH ₃ COO) ₂ ×
L ₁ ·L ₂ +Cu (1) Cl ·L ₁ +H ₂ O (5) Here, L ₁ and L ₂ are, for example, L ₁ =hmpa or benzonitrile (PhCN), and L ₂ =PhCN. To further explain the characteristics of the reaction in more detail,
Pd(2) (CH ₃ COO) ₂ of Pd(0) shown in formula (5)
The rate of oxidative regeneration reaction to L ₁ and L ₂ at 70℃ is:
The regeneration rate was about 10 times higher than the regeneration rate by Cu(2)Cl ₂ according to reaction formula (2) described above. In addition, it was confirmed that Pd(0) is not oxidized and regenerated by Cu(2)(CH ₃ COO) ₂ in an acetic acid solvent (formula (6)). Pd(0)+2Cu(2)(CH ₃ COO) ₂ →Pd(2)
(CH ₃ COO) ₂ +2Cu(1) (CH ₃ COO) (6) The complex that forms the above oxygen complex is expressed by the general formula
When expressed as MmXn·Ll, Cu(1)Cl·hmpa corresponds to the case where m=1, n=1, and l=1. For example, when Ti(3) or V(3) is the central metal and the anion is Cl ^- , the complex formed is
Ti(3) _Cl3・hmpa, V(3) _Cl3・hmpa,
In either case, m=1, n=3, and l=1. Needless to say, Cu(1)Cl·L ₁ produced in reaction formula (5) selectively absorbs oxygen from the air and returns to an oxygen complex. (Special Application No. 122600, 1982). Therefore, if the above oxygen complex is used in an acetic acid solvent,
This allows efficient regeneration of Pd(0) to Pd(2)(CH ₃ COO) ₂ . As described above, in the present invention, the ring element
Since Pd(0) is oxidized and regenerated by the activated oxygen in the oxygen complex, high selectivity and high yield can be achieved in a short period of time under mild conditions such as normal pressure or slightly increased pressure and temperatures below 80°C. It becomes possible to carry out oxidative carbonylation of olefins, oxidation of aromatic compounds or oxidative carbonylation reactions. In the present invention, M in MmXn/Ll as a complex catalyst capable of forming an oxygen complex includes Cu, Ag of the periodic group, Ti, Zr of the group, V, Nb of the group, Cr of the group, Mo, W, of the tribe
Transition metals such as Mn, group Fe, Co, etc. are preferred;
More preferred are Cu(1), Ti(3), and V(3). Further, as X, balogenide ions such as Cl ^- , Br ^{- and} I ^- , anions such as BF ₄ ^- , PF ₆ ^- and SO ₄ ^2- are preferable, and Cl ^- , Br ^- and I ^- are more preferable. Ligands include nitriles, phosphoric acid derivatives such as triphenylphosphine oxide, hexamethylphosphoramide, mono-, di-, or triester formed from the reaction of phosphoric acid with methanol, ethanol, etc., and dimethyl methylphosphonate. , methyl dimethylphosphinate, or derivatives of phosphorous acid, mono-, di-, or triester formed from the reaction of phosphorous acid with methanol, ethanol, etc., and phenylphosphonite, dimethylphosphinate, triethylphosphine. , triphenylphosphine, and the like are preferred, with acetonitrile, benzonitrile, and hexamethylphosphoramide (hmpa) being particularly preferred. On the other hand, as ligands for the Pd(2)(CH ₃ COO) ₂ complex, nitriles such as acetonitrile, propionitrile, and benzonitrile, and the above-mentioned organic phosphorus compounds, as well as toluene fluoride and benzotriflo Preferred examples include organic fluorine compounds such as Ride. As the solvent for the reaction system, in addition to acetic acid, it is preferable to add a solvent that dissolves the complex catalyst, is easily separated from the produced compound, and also reduces the viscosity of the catalyst solution and promotes mass transfer. For example, heptane, toluene, methylcyclohexane, dioxane, propylene carbonate, chlorobenzene, N-methylpyrrolidone, tetrahydrofuran and ethylene glycol monomethyl ether, ethylene glycol dibutyl ether,
At least one solvent selected from various solvents such as ethers such as dilythylene glycol monomethyl ether, or a mixture thereof may be added, or the ligand itself may be mixed with acetic acid. In addition, to increase the stability of the oxygen complex, sulfolane, dimethylsulfolane, dimethylsulfoxide, dimethylformamide, trimethylmethane,
It is preferable to coexist with an electron-donating compound such as dimethylsulfone. The method of oxidizing and regenerating Pd(0) to Pd(2)(CH ₃ COO) ₂ in an acetic acid solvent using an oxygen complex has been described above, and the present invention will now be explained in more detail with reference to Examples. (Example) Example 1 5g of Cu(1)Cl in a reaction vessel with an internal volume of 200ml
(0.05 mol), 61.5 g (0.6 mol) of benzonitrile,
3.8g (0.04mol) of sulfolane, 5.8g of acetic acid
(0.1 mol) and 28.7 g (0.38 mol) of ethylene glycol monomethyl ether, Cu (1)
100 ml of Cl/PhCN complex solution was prepared. The inside of the reaction vessel was degassed and air was introduced at 30°C under normal pressure to form a solution containing an oxygen complex of 0.125 mol/l. Then 40℃
Although the reactor was heated to a temperature of It was found that the oxygen absorption reaction was irreversible. This is advantageous in terms of safety in the actual process. After completely replacing the inside of the system with nitrogen, the inside of the reaction vessel was kept at 70℃ and preliminarily filled with Pd(2).
(CH ₃ COO) ₂ equivalent to 12.5 mM of Pd(0) reduced with hydrogen was quickly introduced into the reactor, and the regeneration reaction of Pd(0) was followed by absorption spectrum. The spectrum confirmed that Pd(0) was completely oxidized and regenerated in 2 minutes to give Pd(2)(CH ₃ COO) ₂ . Examples 2 to 6 In Example 1, when experiments were conducted under the conditions shown in Table 1, Pd(2) after 2 minutes
The reproduction rate of (CH ₃ COO) ₂ was as shown in the rightmost column of Table 1. [Table] These results show that to increase the Pd(0) regeneration rate, the oxygen complex concentration should be increased, and for this purpose, the Cu(1)Cl concentration should be increased. . Further, it is preferable that the CH ₃ COOH concentration is 1M or more. It was found that the reaction did not seem to be very dependent on temperature, and there was no change in regeneration rate up to a H ₂ O concentration of 5M. Example 8 The same procedure as in Example 1 was performed except that 30.8 g (0.17 mol) of hmpa was used instead of ethylene glycol monomethyl ether, and the Pd(0) regeneration rate was 100% in 2 minutes. It was hot. Example 9 Ti(3) instead of Cu(1)Cl in Example 1
When a similar experiment was conducted except that Cl ₃ 0.5M was used, the Pd(0) regeneration rate was 50% in 2 minutes. Example 10 V(3) instead of Cu(1)Cl in Example 1
When a similar experiment was conducted except that Cl ₃ 0.5M was used, the Pd(0) regeneration rate was 55% in 2 minutes. Comparative example 1 Cu (2) in a reaction vessel with an internal volume of 200ml
(CH ₃ COO) ₂ 1.82g (0.01 mol) CH ₃ COOH100
ml, the inside of the reaction vessel was degassed, and nitrogen gas was passed through to 1 atm. The inside of the reaction vessel was kept at 70°C and Pd (2) (CH ₃ COO) ₂ was reduced with hydrogen in advance.
(0) Immediately introduce the equivalent of 12.5mM into the reaction container,
The regeneration reaction of Pd(0) was followed by absorption spectroscopy. Figure 1 shows the visible absorption spectrum of Pd(2)(CH ₃ COO) _2. As the Pd(2)(CH ₃ COO) ₂ concentration increases, the absorbance at 395 nm increases, indicating that it has a maximum absorption. I understand. In addition, Cu (2) is shown in Figure 2.
The visible absorption spectrum of (CH ₃ COO) ₂ was shown,
It was found that there are two maximum peaks at 379nm and 680nm. Therefore, if the regeneration reaction proceeds,
According to reaction formula (6), Pd(2)(CH ₃ COO) ₂ increases,
Cu(2)(CH ₃ COO) ₂ decreases. That is,
The absorption at 395nm should increase and the absorption at 680nm should decrease. For the regeneration reaction, the reaction solution is diluted with CH ₃ COOH.
Since the absorption spectrum was measured after diluting the sample 10 times, if the regeneration reaction did not proceed at all, the result in Figure 2 would be
It should overlap with the absorption spectrum of Cu(2)(CH ₃ COO) ₂ = 1.0×10M. Figure 3 shows reaction time of 2 minutes ~
The reaction absorption spectra for 17 hours were shown, but both spectra showed Cu(2)(CH ₃ COO) ₂ = 1.0×10 ^-2 M
It was found that the reaction did not proceed. By the way, the dotted line in the figure is Pd(0)
This is a spectrum assuming that all of Pd(2)(CH ₃ COO) ₂ is regenerated. As mentioned above, Pd(0) is converted into Cu(2) in acetic acid solvent.
It was found that (CH ₃ COO) ₂ does not regenerate it, but it can be regenerated efficiently by using an oxygen complex. (Effects of the Invention) According to the present invention, Pd(0) reduced by oxygen coordinated to a transition metal complex and activated is quickly converted into Pd(2) in an acetic acid solvent under mild conditions.
(CH ₃ COO) Can be played to ₂ . As a result, Pd(2), which had poor regeneration efficiency of conventional Pd(0),
It becomes possible to carry out the oxidative carbonylation of olefins, the oxidation of aromatic compounds, or the oxidative carbonylation reaction using (CH ₃ COO) ₂ under mild conditions.

[Brief explanation of the drawing]

Figure 1 shows the visible absorption spectrum of Pd(2)(CH ₃ COO) ₂ , Figure 2 shows the visible absorption spectrum of Cu(2).
FIG. 3 is a diagram showing the visible absorption spectrum of (CH ₃ COO) ₂ , and is a diagram showing a spectrum tracing the regeneration reaction of Pd(0) by Cu(2)(CH ₃ COO) ₂ .

Claims (1)

[Claims] 1 In a method of oxidizing and regenerating palladium Pd(0) using an oxidizing agent in an acetic acid solvent, a complex (MmXn・Ll) ( In ^the formula, M is _a transition metal belonging ^to Group ¹ , Group ₂ ^, or ^Iron group of Periodic ^Table _; An anion such as ^- , the ligand L is an organic phosphorus compound, a nitrile, m and n are constants determined by the valence balance, and l indicates the coordination number) is used. Oxidative regeneration method of palladium. 2. Claim 1 provides an oxygen complex characterized in that the organic phosphorus compound as the ligand L is a compound represented by an alkoxy, alkyl or amide derivative of phosphoric acid or phosphorous acid. Palladium oxidation regeneration method used. 3. In claim 1 or 2, the oxidative regeneration of palladium using an oxygen complex characterized by using a basic (electron-donating) compound such as sulfolane, dimethylsulfolane, dimethylsulfoxide, dimethylformamide, etc. Law. 4 In claim 1, 2, or 3, in addition to the acetic acid solvent, ligand L, water, aliphatic, aromatic, alicyclic hydrocarbons, oxygen-containing organic compounds, organic halogens A method for oxidizing and regenerating palladium using an oxygen complex, characterized in that at least one compound selected from compounds, organic fluorine compounds, and heterocyclic compounds is used as a solvent.