JP2000256249A - Production of acetaldehyde - Google Patents

Abstract

PROBLEM TO BE SOLVED: To selectively produce the subject acetaldehyde with industrial advantage by the vapor-phase reaction between methyl acetate, carbon monoxide and hydrogen in the presence of a catalyst carrying a single element, for example, palladium or the like and an alkali metal halide or the like and of a cocatalyst. SOLUTION: In the presence of a catalyst supporting a single element of palladium and/or rhodium or their compounds and an alkali metal halide and/or an alkaline earth metal halide and a cocatalyst (preferably an organic halide or a hydrogen halide, methyl acetate, carbon mono-oxide and hydrogen are allowed to react one another, preferably under pressure of 2-6 MPa at 150-250 deg.C to obtain the objective acetaldehyde. The amount of rhodium or palladium elementary body or their compound is 0.5-5 wt.% on the carrier and the molar ratio of hydrogen to carbon monoxide is preferably 0.25-4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing acetaldehyde by reacting methyl acetate with carbon monoxide and hydrogen in the gas phase. Acetaldehyde is an intermediate such as ethyl acetate, pyridine, and ethylamine, and is a very industrially useful compound.

[0002]

2. Description of the Related Art Acetaldehyde is conventionally produced by the Wacker oxidation of ethylene with oxygen, and there are two methods, a one-step method and a two-step method, using a water-soluble catalyst system of palladium chloride, copper chloride and hydrochloric acid. Has been put to practical use. In the Wacker method, a high chloride ion concentration and a large amount of copper chloride are required, so that the apparatus is highly corrosive, and it is necessary to use a material such as titanium which is practically expensive. Further, since chlorine-based by-products are generated, it is necessary to appropriately separate and dispose of the by-products, and there is a problem of cost.

Under the influence of the raw material circumstances, as a method not using ethylene, (1) a reaction between acetic anhydride and hydrogen at normal temperature, normal pressure and liquid phase using a platinum oxide catalyst or a metal palladium catalyst supported on barium sulfate. (Chem. Ber., 95,
1844 (1962)), (2) Production from acetic anhydride and synthesis gas using cobalt carbonyl catalyst
48-19285), (3) A method of producing acetic anhydride by hydrogenating acetic anhydride at 100 to 200 ° C. under liquid phase pressure using a rhodium chloride catalyst in the presence of triphenylphosphine (US Pat.
No. 566). In the case of these methods, industrialization is considered difficult because the yield and selectivity of acetaldehyde are very low. (4) JP-B-63-37092 describes a method for synthesizing acetaldehyde from methyl acetate, carbon monoxide and hydrogen using a rhodium compound or a palladium compound-supported catalyst.

[0004]

In the embodiment of the above method (4) for synthesizing acetaldehyde from methyl acetate, carbon monoxide and hydrogen, an acetaldehyde selectivity of about 88% is obtained. When the reaction rate is calculated to be about 5%, the yield of acetaldehyde is low. Industrially, it is conceivable to recycle unreacted raw materials, but a catalyst having higher selectivity and conversion is required. An object of the present invention is to develop a highly active catalyst for selectively producing acetaldehyde by contacting methyl acetate with carbon monoxide and hydrogen in the gas phase, and to provide a method for industrially producing acetaldehyde in an advantageous manner. It is.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing acetaldehyde having the above-mentioned problems, and as a result, methyl acetate was brought into contact with carbon monoxide and hydrogen in a gas phase to selectively react acetaldehyde. As a catalyst to be produced, Pd, Rh-supported catalyst, by further adding an alkali metal halide or an alkaline earth metal halide,
The inventors have found that a highly active catalyst can be obtained, and have reached the present invention. That is, the present invention provides a method for producing methyl acetate, carbon monoxide and hydrogen in a gas phase in the presence of a simple substance or a compound of palladium and / or rhodium, a catalyst supporting an alkali metal halide and / or an alkaline earth metal halide and a cocatalyst. A method for producing acetaldehyde, which comprises reacting.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The reaction for producing acetaldehyde from methyl acetate, carbon monoxide and hydrogen in the present invention is represented by the following formula.

Embedded image CH ₃ COOCH ₃ + CO + H ₂ → CH ₃ CHO + CH ₃ COOH (I) In the above reaction, the present invention relates to a simple substance or a compound of palladium and / or rhodium, and an alkali metal halide and / or alkaline earth. In this method, a catalyst supporting a metal-like halide is used.

Specific examples of the palladium compound of the catalyst of the present invention include palladium chloride, palladium ammonium tetrachloride, palladium acetate, dichlorotetramine palladium, and palladium nitrate. Rhodium compounds include rhodium trichloride and rhodium hexamine chloride. , Rhodium ammonium hexachloride, rhodium acetate, rhodium nitrate and the like. Note that simple substances of palladium and rhodium can also be used. As alkali metal halides, chlorides such as lithium, sodium and potassium,
Bromide and iodide. Examples of the alkaline earth metal halide include chlorides, bromides, and iodides such as magnesium, calcium, and strontium. These may be used alone or in combination of two or more.

[0008] Examples of the carrier of the catalyst of the present invention include activated carbon, alumina, silica, silica-alumina, zirconia, titania and the like. Activated carbon and zirconia are preferably used, and a highly active and highly selective catalyst can be obtained. The supported amount of rhodium or palladium alone and the compound on the carrier is 0.1 to 10 wt% as a metal, preferably
It is 0.5 to 5 wt%. The amount of the alkali metal halide or alkaline earth metal halide carried on the carrier is 0.1 to 10% by weight, preferably 0.5 to 5% by weight as a halide. The mixing ratio of a simple substance or a compound of palladium or rhodium with an alkali metal halide or an alkaline earth metal halide can be arbitrarily adjusted.

The catalyst can be prepared by a generally known method. A support is impregnated and supported with a rhodium compound, a palladium compound and an alkali metal halide or an alkaline earth metal halide. As a pretreatment of the catalyst, thermal calcination may be performed under a stream of an inert gas such as nitrogen, helium, or argon. Moreover, you may reduce at 100-400 degreeC under carbon monoxide or hydrogen gas flow.

In the present invention, an organic halogen compound or hydrogen halide is used as a promoter. Examples of the organic halogen compound include methyl iodide, methyl bromide, acetyl iodide, acetyl bromide, and the like, and examples of the hydrogen halide include hydrogen iodide and hydrogen bromide. These may be used alone or in combination of two or more.

The reaction in the present invention is carried out by allowing methyl acetate, carbon monoxide and hydrogen to pass through the above catalyst and a cocatalyst, and reacting them in the gas phase. At this time, the reaction can be performed in the presence of an inert gas such as nitrogen. The ratio of hydrogen to carbon monoxide should be between 0.1 and 0.1 in molar ratio (hydrogen / carbon monoxide).
10, preferably 0.25-4. The supply amounts of hydrogen and carbon monoxide are 5,000 h ^-1 or less in GHSV, preferably 1,000 to 3,000 h.
It is ^-1 . The raw materials methyl acetate and co-catalyst may be supplied individually or as a mixture. The ratio of the cocatalyst to the total amount of methyl acetate and the cocatalyst is 10 to 50 wt%, preferably 20 to 40 wt%. The supply amounts of methyl acetate and the cocatalyst are not more than 10 h ^-1 , preferably not more than 5 h ^-1 in WHSV.
The reaction pressure is not particularly limited. However, if the reaction pressure is too high, liquefaction tends to occur on the catalyst. Generally, 10 MPa or less, preferably 2 to
6MPa. The reaction temperature is equal to or higher than the temperature at which the supplied methyl acetate or cocatalyst is vaporized, and is generally 100 to 300 ° C, preferably 150 to 250 ° C.

[0012]

Next, the method of the present invention will be described more specifically with reference to examples and comparative examples. However, the scope of the present invention is not limited by these examples.

Comparative Example 1 Granular activated carbon (Kuraray Chemical Co., Kuraray Coal GC, 10-
Palladium chloride and rhodium chloride trihydrate were dissolved in an aqueous hydrochloric acid solution so that each metal contained 1 wt% of each metal (32 mesh) and impregnated and supported by an evaporator to prepare a catalyst. This catalyst was charged into a Zr reactor. The upper and lower sides of the catalyst were filled with porcelain Raschig rings having a diameter of 2 mm and a height of 2 mm to fix the catalyst. As a pretreatment of the catalyst, a mixed gas of 50/50 mol% of hydrogen / carbon monoxide is 1000 to 20% by GHSV.
The mixture was flowed at a rate of 00 h ^-1 and subjected to a reduction treatment at 2 MPa and 350 ° C. for 3 hours. For the reaction, a mixed gas of 50/50 mol% of hydrogen / carbon monoxide is flowed at a rate of 3000 h ^-1 by GHSV, and a mixed solution of methyl acetate / methyl iodide (80/20 wt%) is supplied at a rate of 2 h ^-1 by WHSV. Then, the reaction was carried out at 6 MPa and 180 ° C. The product liquid and product gas from the reactor outlet were analyzed by gas chromatography. Table 1 shows the results.

Example 1 The same reaction was carried out as in Comparative Example 1 except that 0.5 wt% of lithium chloride was added to the supported catalyst. Table 1 shows the results.

Example 2 The same reaction was carried out as in Comparative Example 1 except that 0.5 wt% of sodium iodide was added to the supported catalyst. Table 1 shows the results
Shown in

Example 3 The same reaction was carried out as in Comparative Example 1 except that 1.0% by weight of sodium chloride was added to the supported catalyst. Table 1 shows the results.

[0017]

Table 1 Comparative Example 1 Example 1 Example 2 Example 3 Additives No LiCl NaI NaCl Conversion of methyl acetate (%) 28 34 42 40 Selectivity (%) Acetaldehyde 95 98 97 93 Acetic acid 110 100 100 100 Methane 0.1 0.1 0.1 0.1 Ethylidene diacetate 2 1 1 3 (Note) Acetaldehyde selectivity is a value that includes paraaldehyde (trimer of acetaldehyde).

[0018]

As is clear from the above examples, the use of the catalyst according to the present invention not only improves the conversion, but also provides an extremely high acetaldehyde selectivity.
Since acetic acid produced as a by-product can be reacted with methanol to produce methyl acetate, acetaldehyde can be industrially advantageously produced using methanol, carbon monoxide and hydrogen as raw materials according to the present invention. Is big.

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Claims (2)

[Claims] (1) Methyl acetate, carbon monoxide and hydrogen in the gas phase in the presence of a simple substance or a compound of palladium and / or rhodium, a catalyst and a co-catalyst supporting an alkali metal halide and / or an alkaline earth metal halide. A method for producing acetaldehyde, which comprises reacting. 2. The method for producing acetaldehyde according to claim 1, wherein the cocatalyst is an organic halogen compound and / or hydrogen halide.