JPS5811409B2 - Ethanol manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for selectively producing ethanol from methanol and synthesis gas (a mixture of carbon monoxide and hydrogen) in the presence of a cobalt-containing catalyst.

Ethanol is a key industrial product that has traditionally been produced either by fermentation of sugars, grains, etc., or by hydration of ethylene derived from petroleum in the presence of an acid catalyst.

However, due to the recent sharp rise in oil prices and the depletion of oil resources, there is an urgent need to convert industrial products currently derived from oil to methods that do not use oil.

On the other hand, synthetic gas (a mixture of carbon monoxide and hydrogen), which is easily obtained from fossil resources other than petroleum, such as natural gas whose main component is methane, or coal, which exists in larger quantities than petroleum, is converted into methanol. However, it is known that ethanol can be produced according to the following formula by reacting methanol and synthesis gas under appropriate conditions.

CH30H+CO+2H2→CH3CH20H+H20
Regarding this method, various studies have been conducted on methods for promoting the reaction.

For example, it is known to react methanol with synthesis gas in the presence of cobalt compounds such as cobalt acetate or dicobalt octacarbonyl to obtain ethanol, but large amounts of by-products such as acetaldehyde, acetic acid,
The drawback was that methyl acetate or ethyl acetate was produced and the selectivity to ethanol was low.

A method of coexisting a halogen compound such as iodine with the above catalyst is also known, and although this method slightly improves the selectivity to ethanol, it still has the drawback of producing a large amount of by-products.

Furthermore, in recent years, a method has been proposed in which the reaction is carried out in the coexistence of various phosphines using a cobalt halide catalyst to increase the selectivity to ethanol (Japanese Unexamined Patent Publication No. 149213/1983).
issue).

In this method, cobalt iodide and tri-n-butylphosphine, diethylphenylphosphine, etc. are used as the phosphine, octane is used as the solvent, and when methanol and synthesis gas are reacted, ethanol and its precursors are produced with good selectivity. However, the phosphine used here is highly volatile, easily oxidized, and highly toxic, making it extremely difficult to handle safely.

Furthermore, in this method, a special bicyclic heterocyclic phosphine is used that exhibits extremely high ethanol selectivity, but the synthesis of this phosphine is extremely complicated and has many practical problems.

In addition, a method using triphenylphosphine, which is easy to handle, as a ligand has also been proposed (Japanese Patent Application Laid-Open No. 73708/1983).
(No.) cannot be said to have a sufficiently high selection rate.

Other catalysts for use in the above reaction have been proposed, such as ruthenium, nickel, or cobalt catalysts with ruthenium added, but ruthenium is expensive and these have low selectivity, so they are not suitable for industrial implementation. could not be said to be satisfactory.

The present inventors have conducted intensive research to overcome the drawbacks of the conventional method of producing ethanol from methanol and synthesis gas, and as a result, we have developed a method that uses a chelating phosphine with a specific structure as a ligand and contains a halogen. 170-250 in the presence of water and an inert solvent.
We have discovered that ethanol can be synthesized with high selectivity by reacting methanol and synthesis gas at °C, and based on this we have accomplished the present invention.

That is, in producing ethanol by reacting methanol and synthesis gas, the present invention uses cobalt or a cobalt compound, general formula (in which R1, R2, R3, and R4 are aliphatic groups, alicyclic groups, or aromatic groups). a chelating phosphine, bromine, iodine, or a compound thereof; The present invention provides a method for producing ethanol, characterized in that the reaction is carried out at 170 to 250°C in the presence of water in an inert solvent.

The catalyst used in the process of the invention consists of cobalt or a compound thereof, a chelating phosphine and a halogen-containing substance.

Cobalt iodide or cobalt bromide is usually used as the cobalt compound, but other cobalt compounds such as cobalt carboxylates such as cobalt acetate, cobalt carbonate, cobalt hydroxide, cobalt acetylacetonate or dicobalt octacarbonyl are also used. Can be used.

Cobalt or its compound is used in an amount of 1 to 100 ■ atoms, preferably 5 to 40 ■ atoms, per mole of methanol.

When the amount is less than 1 mg atoms, the reaction rate is slow and the selectivity is low, and when it exceeds 100 atoms, the cost of the catalyst increases and is not economical.

Next, addition of a halogen-containing substance is also essential in the method of the present invention, but when a cobalt compound also serves as this compound, such as cobalt bromide or cobalt iodide, the addition can be omitted.

Examples of bromine or iodine compounds include inorganic compounds such as hydrobromic acid, hydriodic acid, potassium iodide, sodium iodide, and cesium iodide, and organic iodine compounds such as methyl iodide and ethyl iodide. can.

The amount of this halogen component added per 1 g atom of cobalt is
It is used in a range of 0.5 to 3.0 mol, preferably 1.0 to 2.0 mol.

If the amount added is less than 0.5 mol, the reaction rate is slow and the selectivity is low, and if it exceeds 3.0 mol, the equipment will be severely corroded, which is not preferable.

The chelating phosphine used in the present invention is 2
It is a compound that has 4 phosphino groups and can form a chelate ring with cobalt, and is represented by the general formula above.

Among the phosphines represented by the general formula, preferred are those in which R1, R2, R3 and R4 each have 1 to 10 carbon atoms, and X is a dimethylene group.

Examples of this chelating phosphine include 1,2-bis(diphenylphosphino)ethane, 1,2-bis(di-
Examples include n-butylphosphino)ethane, 2-bis(cycyclohexylphosphino)ethane, and the like.

The amount of these phosphines added is generally 0.5 to 3.0 mol, preferably 1.0 to 2.0 mol, per 1 g atom of cobalt.

If the amount of phosphine is outside this range, the reaction rate will be low and the selectivity will also be low.

The catalyst used in the process of the present invention is active under milder conditions than conventional catalysts and has very high ethanol selectivity.

In this case, the cotanol synthesis reaction is usually carried out at a reaction temperature of 170~
The temperature is 250°C, preferably 180 to 230°C.

The reaction pressure is a filling pressure at room temperature of 25 to 100
0Ky/cA (gauge pressure), preferably 50-400K
It is determined in the range of fI/cd (gauge pressure).

The molar ratio of hydrogen to carbon monoxide in the synthesis gas is usually 1.0:4.0 to 4.0:1.0, preferably 0.5:1.0 to 3.0. : Implemented within the range of 1.0.

Further, in the method of the present invention, the molar ratio of methanol to synthesis gas is 0.5:1.0 to 20.0:l, preferably 1.0:1.
: 1.0 to 4.0 : Performed in the range of 1.0.

The process of the invention is carried out using an inert solvent, preferably one having 6 to 10 carbon atoms.

Examples of such solvents include, but are not limited to, benzene, toluene, xylene, tetralin, octane, decane, cyclohexane, decalin, liquid paraffin, and the like.

The amount of this solvent used is usually 0.5:1.0 to 50.0:1.0, preferably 1.0:1.0 to 20.0:1.0 by volume to methanol. range.

In the method of the present invention, water must be present in the reaction system together with the catalyst and solvent described above.

The presence of this water not only does not inhibit the action of the catalyst but also promotes the reaction.

The amount of this water is preferably in the range of 10 to 60 parts (volume) relative to the raw material methanol; if it is less than 10%, the ethanol selectivity will be low, and if it is more than 60%, a problem will arise in the uniformity of the catalyst.

The main by-products in this invention are acetaldehyde,
These include 1-dimethoxyethane, acetic acid, methyl acetate, ethyl acetate, n-propanol, and the like.

Acetaldehyde and 1,1-dimethoxyethane are considered to be precursors of ethanol and can be easily converted to ethanol, and these compounds themselves are also useful.

In carrying out the method of the present invention, either batch-type or continuous-type reaction operations can be employed.

According to the method of the present invention, the target ethanol can be produced with high selectivity (selectivity equivalent to or higher than conventional methods using phosphine, which have high selectivities) under relatively mild conditions.

The chelating phosphines used in this case are resistant to oxidation, have low volatility and toxicity, and are easily available.

Therefore, the method of the present invention is extremely advantageous for industrial implementation.

Next, the present invention will be explained in more detail based on examples.

Examples 1-3 1.2-bis(diphenylphosphino)ethane 4-6 mmol, cobalt iodide 1.25f (4 mmol), methanol 107! ,Wed 57! And 20 ml of benzene as a solvent was charged into a 100 mA stainless steel autoclave, the inside of the autoclave was purged with nitrogen, and the autoclave was pressurized with synthesis gas at a predetermined pressure.

The reaction mixture was quickly heated to 200° C. and heated and stirred at the same temperature for a predetermined time. After the reaction was completed, the autoclave was cooled, residual gas was purged, and the reaction mixture was analyzed by gas chromatography.

The results are shown in Table 1 together with the reaction conditions.

Comparative Example 1.2 The reaction was carried out in the same manner as in Example 1 or 2, except that water was not added.

The results are shown in Table 2. Examples 4-6 Cobalt acetate tetrahydrate 1, OS instead of cobalt iodide
The reaction was carried out in exactly the same manner as in Example 2, except that a combination of '(4 mmol) and various halogen compounds was used.

The results are shown in Table 3. Example 7 Cobalt bromide trihydrate 1.31 instead of cobalt iodide
The reaction was carried out in the same manner as in Example 2 except that g (4 mmol) was used.

The conversion rate of methanol was 22%, and the selectivity to ethanol and ethanol and its precursors were 71% and 77%, respectively.

Claims (1)

[Scope of Claims] 1. In producing ethanol by reacting methanol and synthesis gas, cobalt or a cobalt compound, general formula (in the formula, R1, R2, R3 and R4 are aliphatic groups, alicyclic groups) or an aromatic group, and X is a hydrocarbon residue having 2 carbon atoms. A method for producing ethanol, characterized in that the reaction is carried out at 170 to 250°C in the presence of a catalyst and water in an inert solvent. 2. The method for producing ethanol according to claim 1, wherein each of R1, R2, R3 and R4 has 1 to 10 carbon atoms, and X is a dimethylene group. 3. The method for producing ethanol according to claim 1 or 2, wherein R1, R2, R3 and R4 are phenyl groups. 4. The method for producing ethanol according to claim 1, wherein the halogen-containing substance is hydroiodic acid, hydrobromic acid, or methyl iodide. 5. The method for producing ethanol according to claim 1, 2, or 3, wherein cobalt bromide or cobalt iodide serves as cobalt or a cobalt compound and a halogen-containing substance. 6 Reaction temperature 170-230°C1 Reaction pressure 25-10
The method for producing ethanol according to claim 1, wherein the pressure is 00 Kg/cm2 (gauge pressure). 7 The molar ratio of carbon monoxide and hydrogen in the synthesis gas is 0.25
: 1.0 to 1.0 : 0.25, and the molar ratio of synthesis gas to methanol is 0.25 : 1.0 to 20.
:1.0. 8 The amount of cobalt or cobalt compound is 1 to 100 mg atom per mole of methanol, the amount of chelating phosphine is 0.5 to 3.0 mole per 1 g atom of cobalt, and the amount of halogen component is 0 to 1 g atom of cobalt. .5-3
．． The method for producing ethanol according to claim 1, wherein the amount is in the range of 0 mol. 9 The solvent is a hydrocarbon having 6 to 10 carbon atoms or liquid paraffin, and it is 0.5% per volume of methanol.
The method for producing ethanol according to claim 1, wherein the volume is 50 to 50 volumes. 10. The method for producing ethanol according to claim 1, wherein the solvent is benzene. 11 The amount of water added is 5 to 60% per volume of methanol.
A method for producing ethanol according to claim 1.