JPS5851935B2 - 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 11dE, which can be obtained without using 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 acetate or a cobalt compound such as dicobalt octacarbonyl to obtain ethanol, but it produces large amounts of by-products such as acetaldehyde, acetic acid, methyl acetate, etc. Another disadvantage is that ethyl acetate is degraded and the selectivity to ethanol is low.

There is also a known method in which a rogen compound such as iodine is present in the catalyst, and although this method slightly improves the selectivity to ethanol, it still has the disadvantage 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 phosphine) ') -n-7'' tylphosphine, diethylphenylphosphine, etc. are used, octane is used as a solvent, and methanol and synthesis gas are reacted to produce ethanol and its precursors. Although it is produced with good selectivity, the phosphine used here has a high volatile potency, is easily oxidized, and is highly toxic, making it extremely difficult to handle safely.

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

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 used in the above reaction have been proposed, such as those containing ruthenium, nickel, or cobalt catalyst niruthenium, 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, the present inventors have developed a method using chelating phosphine as a ligand.
It was discovered that ethanol can be synthesized with high selectivity by reacting methanol and synthesis gas at 170 to 250°C in the presence of an inert solvent using a cobalt-based catalyst containing a halogen.Based on this, the present invention was developed. I arrived at the eggplant.

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 phenyl groups, and X is -( CH2) m- (where m is 1 to 10 excluding 2)
).

), and a catalyst consisting of at least one halogen-containing substance selected from bromine, iodine or their compounds, the reaction is carried out in an inert solvent at 170 to 250°C. The present invention provides a method for producing ethanol characterized by the following.

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

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.

This cobalt or its compound is used within the range of 1 to 100m9 atoms, preferably 5 to 40rr1g atoms per mole of methanol.If the amount is less than 1Tl9 atoms, the reaction rate is slow and the selectivity is low, and if it exceeds 1001v. This increases the cost of the catalyst, making it uneconomical.

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°O 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 has phosphino groups and is represented by the above general formula.

Among the phosphines represented by the general formula, R1, R2, R3 and R4 are preferably phenyl groups, and X is -(CH2)m- (where m is a number from 1 to 10 excluding 2). It is what is expressed.

Examples of this chelating phosphine include 1,1-bis(diphenylphosphino)methane, 1,3-bis(diphenylphosphino)propane, 4-bis(diphenylphosphino)butane, and 5-bis(diphenylphosphino)butane. Examples include α·ω-bis(diphenylphosphino)alkanes such as (diphenylphosphino)pentane, 16-bis(diphenylphosphino)hexane, and 110-bis(diphenylphosphino)decane.

The amount of these phosphines added is usually 0.5 to 3.0 mol, preferably 1.0 to 2.0 mol, per 1 g atom of cobalt.
Performed in the molar range.

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 ethanol 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 1
000 kg/cr;t (gauge pressure), preferably 5
It is defined in the range of 0 to 400 kg/lA (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, the ratio is 0.5:1.0 to 3.0:1.0.

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

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

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

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

The catalyst used in the method of the present invention smoothly promotes the reaction even in the presence of water, and the selectivity of ethanol is further improved by the presence of an appropriate amount of water. May exist.

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

Acetaldehyde and 1-dimethoxine ethane are considered to be precursors of ethanol and can be easily converted to ethanol, and these compounds themselves are 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 desired ethanol can be produced with high selectivity under relatively mild conditions.

Since the chelating phosphines used in this case are resistant to oxidation and have low volatility and toxicity, 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 to 8 α・ω-bis(diphenylphosphino)alkane (Ph
,,P(CH2)nPPh2(n=1~10),
(hereinafter abbreviated as PCnP) 4 to 6 mmol, cobalt iodide 1.25? (4 mmol), methanol 10IIl
1, 5 ml of water and 20 ml of benzene as a solvent.
The mixture was placed in a 0 ml stainless steel autoclave, and the inside of the autoclave was purged with nitrogen and pressurized with synthesis gas at a predetermined pressure.

The reaction mixture was heated to <200'C and stirred at the same temperature for a specified 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.

Examples 9-17 PC4P1PC3P or PC1P4-6 mmol, cobalt iodide 1.25f (4 mmol), methanol 10
m1 and benzene 20771A as solvent! 100m
Prepared in a 1 volume stainless steel autoclave.
Synthesis gas at a predetermined pressure was introduced and reacted in the same manner as in Example 1 without adding water, and the reaction mixture was analyzed.

The reaction conditions and analysis results are shown in Table 2.

Comparative Examples 1 to 3 Triphenylphosphine or tri-n instead of PCnPO
-The reaction was carried out in the same manner as in Example ※※l except that butylphosphine was used.

The results are shown in Table 3.

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 phenyl groups, and X is - (CH2) m- (where m is 1 to 1 excluding 2)
(indicates an integer of 0). ), and a catalyst consisting of at least one halogen-containing substance selected from bromine, iodine or their compounds, the reaction is carried out in an inert solvent at 170 to 250°C. A method for producing ethanol, characterized by the following. 2. The method for producing ethanol according to claim 1, wherein m is 4. 3. The method for producing ethanol according to claim 1, wherein the rogen-containing substance is bromine, iodine, or methyl iodide. 4. The method for producing ethanol according to claim 1 or 2, wherein cobalt or a cobalt compound and cobalt bromide or cobalt iodide serve as the rogen-containing substance. 5. The method according to claim 1, which is carried out in the presence of water. 6 Reaction temperature 170-230℃, reaction pressure 25-100℃
The method for producing ethanol according to claim 1, wherein the ethanol is 0 kti/crA (gauge pressure). 1 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. The method for producing ethanol according to claim 1, wherein 8) If the amount of cobalt or cobalt compound is 1 to 100 ■ atoms per mole of methanol, the amount of chelating phosphine is 0.5 to 3.0 moles per 12 atoms of cobalt, and the amount of halogen component is cobal)! 0.5 to 3 per atom
．． 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 to 1 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 or 9, wherein the solvent is benzene.