JPS605581B2 - Manufacturing method of vinyl acetate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing vinyl acetate in one step by reacting acetic anhydride with hydrogen.

For more details, see "Lithium, potassium, cesium, barium, and strontium fluoride used as cocatalysts in a method for producing vinyl acetate by reacting acetic anhydride with hydrogen in the presence of palladium metal and/or its compound and methyl chloride." Compound L A method for producing vinyl acetate, characterized in that chloride, bromide, iodide or an organic acid salt is used in an amount of 2.5 x 10-3 to 1% by weight based on the reaction solution.Conventionally, a method for producing vinyl acetate A method using acetylene as a raw material has been known for a long time, but in recent years, a method of converting the raw material to ethylene has been developed, and the ethylene method has become more advantageous.

Direct synthesis of vinyl acetate from ethylene began with methods such as palladium chloride catalysts or the coexistence of sodium acetate in this system. On the other hand, another method has been proposed in which acetaldehyde and acetic anhydride are converted into vinyl acetate and acetic acid directly or via ethylidene diacetate (1,1-diacetoxychetane) as raw materials. [For example, Hydrocarb
Process, 44(11) 287 (1965), UK Patent 1112555, US Patent 2021698, 24
2,538,928,6015 ships etc. ]. In other words, these methods include direct reaction between acetaldehyde and acetic anhydride, and methods in which acetaldehyde and acetic anhydride are reacted to produce aethylidene diacetate, which is then thermally decomposed to produce vinyl acetate. known as. In addition, as another method, the present inventors have already proposed a method for synthesizing vinyl acetate in one step by reacting acetic anhydride with hydrogen (Japanese Patent Application No. 55-138-411).
.

This method produces vinyl acetate by reacting acetic anhydride with hydrogen in the presence of one or more Group 8 metals and/or their compounds and halides such as chlorides, bromides and/or iodides. This is a method of manufacturing.
In this method, in addition to the target product vinyl acetate, by-products such as ethylidene diacetate and acetaldehyde may be produced. The present inventors have continued to conduct intensive research in order to eliminate the drawbacks of conventional methods and improve the production rate and selectivity of vinyl acetate, and have discovered that the above objectives can be achieved by adding appropriate additives. Completed the invention.

That is, the present invention uses fluorides of lithium, potassium, cesium, barium and strontium as co-catalysts in a method for producing vinyl acetate by reacting acetic anhydride and hydrogen in the presence of palladium metal and its compounds and methyl chloride. , a chloride, bromide, iodide or organic acid salt is used in an amount of 2.5 x 10-3 to 1% by weight based on the reaction solution.

Although the detailed reaction mechanism for producing pinyl acetate by the hydrogen reduction reaction of acetic anhydride according to the present invention is not clear, the overall reaction can be expressed by the following chemical reaction formula.

2 (C ratio CO) 20 days 21 CH2 = CHOCOCH3
The reaction represented by the above chemical formula can be suitably carried out by using palladium metal and/or its compound and methyl iodide as catalysts, and further by using the above-mentioned infant catalyst.

Any form of palladium metal catalyst can be used.

For example, the metal itself or in its fragmented form;
Raney metal forms or carbonates, oxides, peroxides,
hydroxide, nitrate, sulfate, phosphate, halide, cyanide, thiocyanide, sulfonate, C, ~C
5 lower alkoxides such as methoxides or ethoxides, phenoxides, metal carboxylates in which the carboxy ion is derived from alkanoic acids having 1 to 20 carbon atoms, oxyhalides, hydrides, carbonyls, nitrites,
Sulfites, phosphites, acetylacetone salts, sulfides,
There are also compounds containing ammonia, cyanide, amines, amino acids, etc. Some examples include Pd metal, PdX2, P clothing 2, 2nd 20, P sail 2, 3rd
d(CN)2, P also day, Pd(OH)2, Pd(OH)
2. State day 3, Pd (N03) 2, P is also 0, Pd0, Pd
02, PdS04/General 20 “P also S, [Pd(PPh3
)2] CI2, PdS, PdS2, Pd3 (P04)2
, Na2PdX4, Pd [(n-C4 is)3P] (CO
) CI2, K2PdX4, Li2PdX4, Pd(OA
c) 2, Pd(AcAc)2・Pho2(PhCN)2・
Pd(SCN)2/Pd(NC)2, palladium benzenesulfonate (× in the above formula is F, CI, Br or 1
, Ph is a phenyl group, Ac0 is an acetoxy group, AcAc
represent an acetylacetonate group, respectively. ) can be given. Also, Group 8 metals bonded to silica, polyvinyl chloride or polystyrene-divinylbenzene groups cross-linked by phosphine, silyl, amine, pyridine or sulfide bonds [e.g.
H, 560-566p (1973); 117-12 (
It is also possible to use a metal-polymer money body made of the following: (1975) and the like. As described above, palladium metal is used as the catalyst metal in the present invention.

The metal catalyst can be used from the beginning or in a final state soluble in the reaction solution to form a homogeneous catalyst.

Alternatively, a faceless or only partially soluble form can be used, resulting in a heterogeneous catalyst system. In the case of heterogeneous catalyst systems, the group metal compound or the metal itself,
It can be used in the form of finely pulverized metal or Raney metal, but it can also be supported on a carrier as described below. In this case, the supporting method may be, for example, a conventional dipping method, kneading method, adsorption method, coprecipitation method, ion exchange method, etc., but other methods are also possible.

To give some examples, a carrier is mixed with a solution containing palladium metal or its metal compound and other components as necessary, and then formalin, hydrogen, sodium formate, etc.
Carbon monoxide, sodium borohydride, lithium aluminum hydride, or by denaturing a metal compound into a metal using ordinary reducing means such as hydrazine, followed by drying, but is limited to these methods. The method is not critical as long as it can support palladium metal and/or its compounds.Supports that can be used include carbon, graphite, bone char, alumina, silica, silica alumina, barium sulfate, zeolite, and spinel. , alumina with magnesia, thoria, titanium oxide, zirconium oxide, thorium oxide, lanthanum oxide, cerium oxide, zinc oxide, tantalum, clay, diatomite, celite, asbestos, pumice, bauxite, white clay, Super-F
Natural and treated clays such as iltrol, silicon carbide, zeolite and zeolite molecular sieves, ceramic bee mirrors, boria' cement etc. are used, but preferably carbon, graphite, bone char, alumina, silica, silica alumina, barium sulfate, zeolite, spinel,
Alumina with magnesia is used. The carriers are used as particles of uniform and non-uniform size and capillary shape and optionally in forms such as moldings, extrudates, ceramic rods, balls, broken pieces, tiles and the like. As described above, it has been disclosed that the group metal catalyst according to the present invention can be used in the form of either a homogeneous catalyst or a heterogeneous catalyst. Using a catalyst is a preferred embodiment.

The present invention requires the presence of methyl chloride along with a metal catalyst.

The amount of palladium metal catalyst used in the present invention varies depending on whether a homogeneous catalyst or a heterogeneous catalyst is used, or whether the reaction is carried out in a fluidized bed or a fixed bed in the case of a heterogeneous catalyst, but in principle, it can be used in any range. usage is possible.

However, generally speaking, 1×10-4 to 25% by weight, preferably 5×10-4 to 2% by weight, more preferably 1×
A range of 10-3 to 15% by weight is selected, but especially 2
．． A range of 5x10-3 to 1% by weight is useful. The amount of methyl iodide used together with the palladium metal catalyst is 10-3 to 15 mol, preferably 10-2 to 5 mol per 1 iodine atom based on the total volume of the reaction solution.
It is used in moles, more preferably in the range of 10-1 to 3 moles. In the present invention, in addition to the catalyst system described above, a co-catalyst is used in order to further increase the reaction rate or improve the selectivity to the target product.

The co-catalyst used in the present invention is a compound such as fluoride, chloride, bromide, iodide or an organic acid salt of lithium, potassium, cesium, barium or strontium, preferably an acetate. Of course, a mixture of these may be used. Cocatalysts can also be used together with the palladium metal catalyst or separately supported on a support.

The amount of co-catalyst used is 2.5 x 10-3 to 1% by weight based on the reaction solution. In the present invention, by using a solvent in addition to the catalyst system described above, the production rate and selectivity of vinyl acetate, which is the target product, can be improved.

Preferred solvents that can be used have a dielectric constant of 18
Below, the organic substance preferably has a molecular weight of 15 or less, more preferably 8 or less, and optimally 6.5 or less.

Any structure of the organic substance used as a solvent may be used, but aliphatic hydrocarbons having 5 to 20 carbon atoms, aromatic hydrocarbons having 6 to 20 carbon atoms, and 4 to 2 carbon atoms may be used.
Organic acid esters having 0 carbon atoms, ethers having 4 to 20 carbon atoms, ketones having 4 to 20 carbon atoms, alcohols having 4 to 20 carbon atoms, halogenated hydrocarbons having 4 to 20 carbon atoms, and the like can be used.
Saturated aliphatic hydrocarbons, aromatic hydrocarbons, and organic acid esters are preferred solvents. Specific examples of solvents that can be used include pentane, hexane, heptane, octane, aliphatic hydrocarbons such as nona, decane, undecane, dodecane, tridecane, tetradecane, bentadecane, hexadecane, cyclobentane, cyclohexane, and alkyl derivatives thereof. Benzene, toluene, o-, m-,
p-Xylene Aromatic hydrocarbons such as trimethylbenzenes, ethylbenzene, propylbenzene, naphthalene, biphenyl, diphenylmethane and their alkyl derivatives Ethyl acetate, propyl acetate, butyl acetate, amyl acetate, hexyl acetate, cyclohexyl acetate, octyl acetate , phenyl acetate, tolyl acetate, pendyl acetate, butyl formate, amyl formate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl benzoate, ethyl benzoate, methyl toluate, dimethyl adipate, ethylene glycol diacetate , diethylene glycol diacetate, propylene glycol diacetate, y-valerolactone, 6-cuff.

Organic acid esters such as rolactone, diethyl ether, dipropyl ether, methyl butyl ether, dibutyl ether, butyl ethyl ether, diamyl ether, diphenyl ether, anisole, tetrahydrofuran,
Ethers such as 114-dioxane, butylpropyl ether, benzyl ethyl ether, phenetol, dibenzyl ether Ketones such as acetophenone, cyclohexanone, 3-bentanone, 4-methyl-2-bentanone 1-pentanol t 3-methyl-1- Alcohols such as butanol, 3-methyl-2-propanol, 1-hexanol, 1-octanol, cyclohexanol, phenol, and benzyl alcohol Halogenated hydrocarbons such as chlorobenzene, dichlorobenzene, and iodobenzene Amount of solvent used Although there is no particular restriction on
more preferably 5 to 9 weight %, most preferably 5 to 8 weight %.

It is preferable to select the type and amount of the solvent so that the dielectric constant of the reaction solution at 2500° C. is 19 or less, preferably 18 or less, more preferably 17 or less. To carry out the method of the present invention, the reaction temperature is 20 to 50,000, preferably 30 to 50,000.
A range of 350 qo, more preferably 40 to 25,000 qo is suitable, but a range of 80 to 220 qo is particularly effective.

The total reaction pressure is also not a critical parameter in the production, as long as it is sufficient to keep the reaction liquid in the liquid phase and the hydrogen at a suitable partial pressure.

The preferred partial pressure of hydrogen is between 0.05 and 30 atmospheres, optimally 0.
．． The partial pressure is 1 to 200 atmospheres, more preferably 0.2 to 100 atmospheres, but a wider partial pressure range of 0.01 to 500 atmospheres is also acceptable. The hydrogen used does not necessarily have to be of high purity and may contain carbon monoxide, carbon dioxide, methane, nitrogen, rare gas, etc. The raw material gas can be supplied in the form of synthesis gas (mixed gas of carbon monoxide and hydrogen). In general, carbon monoxide in the reaction gas, which is likely to be mixed with hydrogen gas, tends to stabilize the catalyst and suppress side reactions. Therefore, it is a preferred embodiment to mix carbon monoxide in the reaction gas in an amount of 0.1 mol % or more, preferably 1 mol % or more, more preferably 2 mol % or more. Acetic anhydride, which is a raw material of the present invention, is an example of oxidation of acetaldehyde.
Alternatively, acetic acid produced by the oxidation of acetaldehyde or the reaction of methanol and carbon monoxide can be supplied by the so-called Watsuka method using ketene as an intermediate, or acetic anhydride produced by the reaction of methyl acetate and carbon monoxide. You can also use

[For example, Tokuko Sho 52-3920 Hakama Kai Sho 51-65709
Examples include Tokubatsu-Kai 54-59214. ] In the above case, it is expected that impurities such as acetic acid, methyl acetate, acetaldehyde, etc. will be mixed into the raw materials, but as long as they do not disturb the overall balance of the reaction, it is preferable to allow the above impurities and proceed with the reaction. You can proceed to

In addition, when acetic anhydride produced by the carbonylation reaction of methyl acetate is used as a raw material, synthesis gas is used as the raw material gas in the carbonylation reaction, and part or all of the reaction waste gas in this step is used as the hydrogen gas in the present invention. It can also be used as a raw material gas for chemical reactions. Furthermore, it is a reasonable embodiment to reuse part or all of the reaction waste gas in the hydrogenation reaction step in the carbonylation reaction step, thereby reusing the raw material gas and the reaction waste gas. Furthermore, acetic anhydride according to the above method is produced using a halide such as methyl iodide as a cocatalyst. It can also be used in part or in whole. Furthermore, it is a reasonable embodiment to mutually repurpose the methyl iodide catalyst by reusing part or all of the methyl iodide catalyst in the reaction step of the present invention in the carbonylation reaction step. . The presence of water in reaction raw materials and solvents is a common phenomenon, but hydrogen and acetic anhydride allow the presence of a small amount of water, which is common with commercially available reactants, and there is no problem. Does not occur.

However, the presence of more than 10 mol% of water in one or more of the reaction raw materials and solvent used in the present invention should generally be avoided, and introducing a large excess of water into the reaction system may lead to the decomposition of the raw materials and products. Easy to invite. In this respect, it is desirable that the water content be 5 mol% or less, more preferably 3 mol% or less. Since water is not a reaction product, maintaining near-anhydrous conditions in the reaction solution is easily accomplished by maintaining proper dryness of the necessary reactants, solvents, and reaction working fluids introduced into the reaction zone. Ru. The method of the invention can be carried out batchwise, semi-batchwise or continuously. In addition, in the case of a heterogeneous catalyst, the reaction type can be carried out in either a fluidized bed type or a fixed bed type. Vinyl acetate, which is kept in a mixed liquid state containing tylidene diacetate, vinyl acetate as the desired product, acetic acid as the by-product, and the main components, has the property of separating the generated vinyl acetate from the reaction liquid and causing a polymerization reaction. It is important to maintain a low concentration of in the reaction system.

Therefore, by separating the product, for example by distillation, the concentration of vinyl acetate in the reaction solution can be reduced to 25% by weight or less based on the reaction solution.
It is preferably kept below 15% by weight, more preferably below 1% by weight, but it is particularly effective to keep the concentration below 5% by weight. Similarly, in the reaction of the present invention, it is necessary to avoid a large excess of acetic acid, which is a by-product, remaining in the reaction system, as this tends to inhibit the production of the desired product.

Therefore, the concentration of acetic acid in the reaction solution is 50% of the reaction solution.
It is particularly effective to keep the concentration below 40% by weight, more preferably below 3% by weight, but below 2% by weight. In order to effectively separate vinyl acetate and acetic acid from the reaction solution described above, evaporation removal can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing will be better understood by reference to the drawings, which show, by way of illustration only, a diagrammatic illustration of a curved reaction and separation system implementing the process of the invention.

In Figure 1, reaction zone 10 comprises one or more pressure reactors of any type containing a suitable catalyst, typically consisting of palladium metal in combination with methyl iodide. Introduce the reaction solution.

A raw material gas containing hydrogen is pressurized into the lower part of the reaction zone 10 via 11, and acetic anhydride is introduced from 12. The effluents of the reaction and coagulation reactions via the reaction zones 10 to 13 are introduced into a separation zone 20' consisting of one or more distillation units, e.g. flash devices and/or fractionation columns, in order to separate them into their main parts. . The high boiling components of the reaction mixture containing essentially non-volatile catalyst components are recycled to reaction zone 10 via 21. Low-boiling components in the reaction mixture consisting of acetaldehyde, methyl iodide, methyl acetate, vinyl acetate, acetic acid, etc. are introduced via 22 into a separation zone 30 consisting of one or more distillation units. Methyl chloride and methyl acetate are recycled to the reaction zone 10 via 33, but crudely separated vinyl acetate and acetic acid are extracted together or separately from 31 or 32. Explain how.
In Figure 2, the reaction zone 10 consists of one or more pressure reactors of any type containing a suitable catalyst, typically palladium metal in combination with methyl iodide. Introduce the reaction solution.

The feed gas is passed from 101 to 103 along with a circulating gas stream 109.
acetic anhydride is pressurized into the lower part of the reaction zone 100 via
Introduce from 2. The effluent stream passing through the reaction zones 100 to 105, i.e. the reacted and unreacted effluent vapor stream containing the reactant gas, is separated into its main components by one or more gas stations, as is well known to those skilled in the art. It is introduced into a separation zone 200 consisting of a liquid separator and a distillation unit. That is, the effluent vapor stream containing hydrogen passes through 105 and is separated into gas and liquid at separation zone 200 . A gas stream containing non-condensable hydrogen passes through 108 and 109 and is circulated together with the feed gas from 101 to the reaction zone 100 via 103, but is partially discharged from the system through 110 as necessary. Sometimes. On the other hand, components such as acetaldehyde, methyl iodide, methyl acetate, pinyl acetate, and acetic acid are separated into gas and liquid by stripping and/or evaporation in a separation zone 200 via a stripping and/or evaporation 105. A portion of acetic acid, or a large portion of components such as acetaldehyde, methyl iodide, methyl acetate, etc., is recycled to reaction zone 100 with the reactant gas stream. On the other hand, the effluent containing vinyl acetate and acetic acid separated into gas and liquid by the separation zone 200 is 10
7 and is introduced into the separation zone 300. The low boiling point components mainly consisting of methyl acetate and methyl iodide are 300 to 3
The high-boiling components, mainly consisting of acetic anhydride, ethylidene diacetate and solvent, are recycled to the reaction zone 100 via 300 and 304. The desired products, vinyl acetate and acetic acid, are 301
Alternatively, they are extracted from 302 together or separately.
In some cases, a portion of the reaction liquid in the reaction zone is removed from 104 in order to prevent the accumulation of created polymers and other high-boiling byproducts that may be generated during the reaction, or to extract a portion of the catalyst. Sometimes it is purged. The method of the present invention, which has been described in detail above, produces vinyl acetate by reacting acetic anhydride with hydrogen using a novel reaction, and has extremely high industrial significance.

This will be explained in more detail below with reference to Examples. Example 1 In a pressure reactor, 135 minutes of acetic anhydride, 15 minutes of methyl iodide, and 5 hours were added to a pressure-resistant reactor.
% Palladium activated carbon (manufactured by Engelhard Japan, commercially available)
Add 4.5 liters of water, acetic acid, and 5.0 liters of lithium, and use a mixed gas of hydrogen and carbon monoxide (ship: CO! 2:1).
With a G of 0k9', 50k9/lump G while supplementing hydrogen,
The temperature was kept at 175°C and the reaction was carried out for 30 minutes.

After the reaction, the solution contains a considerable amount of acetic acid as well as 1.4% vinyl acetate.
This included 18.4 days of ethylidene diacetate. Comparative Example 1 The same procedure as Example 1 was carried out except that lithium acetate was not added.

After the reaction, the solution contains a considerable amount of acetic acid and 0.6 vinyl acetate.
It contained 75 parts, ethylidene diacetate, 35.1 parts, and ethyl acetate, 0.136 parts. Example 2 In a pressure-resistant reactor, 1359% of acetic anhydride, 15% of methyl iodide, 0.45% of palladium black, and 2.0% of potassium fluoride were added.
The reaction mixture was heated at 175°C using L hydrogen at 10k9'G, and reacted for 30 minutes.

After the reaction, the solution contains vinyl acetate 1.1 along with a considerable amount of acetic acid.
This included 4.92 days of ethylidene diacetate.

Examples 3 to 11, Comparative Example 2 15 kg of methyl iodide and 0.45 kg of palladium black were used, and additives were added.
Table 1 summarizes the results of the minute reaction.

Comparative Example 2 is an example in which nothing is added.

Table 1 Example 12 In a pressure-resistant reactor, acetic anhydride 90 days, methyl iodide 15 days, ethylidene diacetate 45.0 days, palladium flux 0.075 days, barium iodide (gloss 121 is 20) 4.5 days
The reaction mixture was allowed to react for 2 hours using hydrogen at 10k9'G and 175qo.

After the reaction, the solution contains a considerable amount of acetic acid as well as 2.0% vinyl acetate.
Contains 8 mols, 45.1 ml of ethylidene diacetate, and 0.041 ml of acetaldehyde.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are illustrations of process diagrams for carrying out the method of the present invention, and the numbers in the figures are respectively 10; reaction zone, 20;
, 30: Separation zone, 11; Raw material gas supply line, 12; Raw material and catalyst supply line, 100; Reaction zone, 200, 30
0: Separation zone, 101: Indicates raw material supply line. Figure 2 of the mackerel map

Claims (1)

[Claims] 1. In a method for producing vinyl acetate by reacting acetic anhydride and hydrogen in the presence of palladium metal and/or its compound and methyl iodide, lithium,
A method for producing vinyl acetate, characterized in that 2.5 x 10^-^3 to 10% by weight of potassium, cesium, barium, strontium fluoride, chloride, bromide, iodide or organic acid salts are used in the reaction solution. Production method.