GB2087393A - Process for preparing ethanol - Google Patents

Abstract

Ethanol is prepared with a high selectivity and a high space time yield by reacting methanol with carbon monoxide and hydrogen in the presence of a combination of manganese and ruthenium as a catalyst, if necessary, together with iodine or an iodine compound as a promotor, with or without methyl acetate.

Description

SPECIFICATION Process for preparing ethanol This invention relates to a process for preparing ethanol from methanol, carbon monoxide and hydrogen, and more particularly it relates to a process for preparing ethanol from methanol, carbon monoxide and hydrogen in the presence of a novel catalyst.

In preparing ethanol by the homologation reaction of methanol, processes employing a main catalyst of cobalt; ruthenium or osmium compound combined with iodine, bromine or a compound thereof have been well known. However, a variety of by-products such as dimethyl ether, acetaldehyde, dimethoxyethane, acetic acid, propionic acid, methyl formate, methyl acetate and ethyl acetate other than the desired ethanol are simultaneously formed by the reaction in the presence of the catalyst and the selectivity to ethanol has been generally low.

Various processes have been proposed recently as alternative processes; however, they can be regarded as improved processes using cobalt compounds as main catalysts. For example, a process for reaction in the presence of a catalyst consisting of cobalt and iodine, bromine or a compound thereof combined with tertiary phosphines as an accelerator in a hydrocarbon solvent (Japanese Laid-open Patent Application No. 149213/76) or a process using a combination catalyst system of a ruthenium compound in addition to said catalyst system (Japanese Laidopen Patent Application No. 92330/80) has been proposed.

In the former process, the selectivity to ethanol is improved by using tertiary phosphines as an accelerator. On the other hand, the process has a disadvantage of extremely reduced space time yield due to the low rate of reaction. In the latter process, the space time yield is improved by the combination of the former catalyst system with a ruthenium compound. On the other hand, there is a disadvantage of reduced selectivity to ethanol. In these processes, the following various industrial problems are raised with a plurality of iodine, or bromine and phosphorus compounds as a ligand: The complicated catalyst required troublesome steps for recovering the catalyst components.

The tertianry phosphine is unstable, and therefore the loss caused by recovery is great.

Furthermore, the high price thereof has a disadvantage of increasing the catalyst cost.

As described above, all the well-known processes have problems in selectivity to ethanol, rate of reaction and recovery and reuse of the catalyst systems, respectively. These processes can be regarded as satisfactory by no means in an industrial sense.

As a result of intensive research made to avoid the various disadvantages described above, the present inventors have found that ethanol can be synthesized with a high selectivity at a sufficient rate of reaction by carrying out the reaction in the presence of a combination of manganese with ruthenium, if necessary together with iodine or an iodine compound with or without methyl acetate, and have established the present invention.

Thus, the present invention provides a process for preparing ethanol by reacting methanol with carbon monoxide and hydrogen, which comprises conducting reaction in the presence of a combination of manganese and ruthenium as a catalyst, if necessary, together with iodine or an iodine compound as a promotor, with or without methyl acetate.

The use of manganese or ruthenium alone in combination with iodine or an iodine compound as a catalyst gives only a low rate of reaction and a low selectivity to ethanol. The present process however is characterized by the combination of both manganese and ruthenium as a catalyst.

The reaction is preferably carried out in the presence of methyl acetate. In this case, ethyl acetate formed simultaneously with ethanol is a precursor of ethanol and convertible into ethanol and acetic acid readily by hydrolysis, etc. in the ordinary manner. Acetic acid is readily convertible into methyl acetate with raw material methanol. In accordance with the present invention, the presence of methyl acm-ate in combination with the present catalyst increases a rate of reaction, and particularly has a strong suppressant action on the formation of acetic acid as a by-product from methanol.

Examples of a catalyst source of manganese in the present invention include metallic manganese, manganese carbonyl compound, and manganese salt of organic acid such as manganese formate, manganese acetate, manganese n-butyrate, manganese benzoate and manganese naphthenate, manganese (II) or (III) acetylacetonate and inorganic manganese compounds such as manganese dioxide, manganese carbonate and manganese chloride.

Examples of a catalyst source of ruthenium in the present invention may be any compound containing ruthenium and include halides, oxides, carbonyl compounds, phosphides, oxo acids or acid salts. Manganese (II) acetate and ruthenium chloride are preferred industrially from the viewpoint of availability.

As for the amount of the catalyst to be used for carrying out the present invention suitably, the molar ratio of manganese to methanol is 0.0001-0.1:1, preferably 0.005-0.05: 1. The molar ratio of ruthenium to methanol is 0.0001-0.05:1, preferably 0.001-0.02:1. Of the molar ratio is lower than the lower limit of the range described above, the rate of reaction is reduced. The molar ratio higher than the upper limit of the range described above has no adverse effect on the reaction, but is not economical. The combined use of both manganese and ruthenium in the above-mentioned ranges provides an improved catalytic activity.

Presence of methyl acetate in the reaction system is preferable and a molar ratio of methyl acetate to methanol is 0.01-5.0: 1, preferably 0. 1-2.0: 1. If the molar ratio is lower than the lower limit of range described above, the effect of presence there is reduced. If the molar ratio is higher than the upper limit of the range described above, the space time yield is reduced.

Therefore, the above-mentioned range is desirable.

Examples of iodine or an iodine compound in the present invention include methyl iodide, sodium iodide, potassium iodide, lithium iodide and iodic acid. A molar ratio of iodine or iodine compound to methanol is 0.001-0. 1:1. preferably 0.005-0.05:1. If the molar ratio is lower than the lower limit of the range described above, the rate of reaction tends to reduce. The molar ratio higher than the upper limit of the range described above is not economical.

Therefore, the above-mentioned range is desirable.

The reaction temperature is 1 20 to 300"C, preferably 150 to 250"C. At a temperature lower than 120"C, the rate of reaction is reduced and not economical. At a temperature higher than 300on, side reactions are increased.

The molar ratio of carbon monoxide to hydrogen is in the range of 4:1-1:4, preferably 1:22:1.

The reaction is carried out under pressure. There is no restriction to pressure level particularly, but the pressure is practically 50 kg/cm2 or higher, and preferably 100 to 500 kg/cm2.

In the present invention, ethanol can be obtained at a sufficient rate of reaction with an improved selectivity to ethanol with a reduced amount of by-products. Furthermore, the catalyst is recovered readily. The present process is commercially advantageous for preparing ethanol.

The present process is not limited to a batch process, and can be carried out continuously.

The present process will be described in detail, referring to examples.

Example 1 A shaking Hastelloy (Registered Trade Mark) autoclave with a net capacity of 100 ml was charged with 10 g of methanol, 10 g of methyl acetate, 1 g of manganese acetate [Mn(CH3CO0)24H2) and 0.2 g of ruthenium chloride (RuCI3) as a catalyst and 1 g of iodine, and tightly closed.

A gas mixture (H2/CO = 1) of carbon monoxide and hydrogen was then injected into the autoclave and subjected to reaction at 200"C for one hour.

After the reaction, the autoclave was cooled, and the remaining gas was purged. The reaction product solution was subjected to gas chromatography. Conversion of methanol was found to be 30.4% by mole. The selectivities to the respective products were found as follows: ethanol 65.8% by mole; acetic acid 3.85% by mole; ethyl acetate 18.8% by mole. Overall selectivity to ethanol including ethyl acetate as a precursor of ethanol was calculated at 75.2% by mole by using the following equation: Overall selectivity to ethanol (% by mole) Number of moles of ethanol and ethyl acetate in reaction solution = x100 Difference between charged methanol (moles) and unreacted methanol (moles) The methyl acetate added was substantially not lost.

Examples 2-6 Reaction was carried out in the same manner as in Example 1, except that charging ratio of raw materials, kind and amount of main catalyst used, kind and amount of the promotor and reaction conditions were changed. Results obtained are shown in Table 1.

Comparative Examples 1-2 Results of Comparative Examples 1-2 corresponding to Example 1 are shown in Table 2. As can be seen from Table 2, selectivities were low when manganese or ruthenium was used alone as a main catalyst.

Table 1 H2/Co Pressure Raw Materials Promotor (molar Temperature Example (g) Main catalyst (g) (g) ratio) (kg/cm)/( C) Methanol (10) *Mn(AcO)2.4H2)(1) 200 2 Methyl - 1:1 acetate (10) RuCl3(0.2) 200 Methanol (10) *Mn(AcO)2.4H2O (0.5) CH3I 200 3 Methyl 1:1 acetate (10) RuO4 (0.2) (1) 200 Methanol (7) *Mn(AcO)2.4H2O (0.5) Iodine 150 4 Methyl 2:1 acetate (14) RuCl3 (0.2) (1) Methanol (10) Mn2 (CO)8 (1) Iodine 200 5 Methyl 1::1 acetate (10) RuO4 (0.2) (1) Methanol (10) Acetylacetonate- Nal 200 6 Methyl manganese (II) acetate (10) RuCl3 (0.2) (1) 220 * Means manganese acetate (tetrahydrate) Conversion Selectivities (mol%) Overall Selectivity Time of methanol to ethanol (hr) (mol%) Ethanol Acetic Ethyl (mol%) acid acetate 1 13.0 39.4 - 3.76 41.6 2 41.7 59.4 5.99 23.3 71.1 1 55.6 44.3 8.73 44.0 66.5 1 40.2 68.2 4.10 17.8 77.1 2 31.9 52.1 9.53 32.1 68.2 Table 2 Compara- H2/Co Pressure/ tive Raw Material Promotor (molar Temperature example (g) Main catalyst (g) (g) ratio) (kg/cm)( C) Methanol (10) *Mn(AcO)2.4H2O Iodine 200 1 Methyl (1) 1:1 acetate (10) 200 Methanol (10) RuCl3 Iodine 200 2 Methyl (0.5) 1:1 acetate (10) (1) 200 * Means manganese acetate (tetrahydrate).

Selectivities (mol%) Conversion Overall selectivity Time of methanol Acetic Ethyl to ethanol (hr) (mol%) Ethanol acid acetate (mol%) 3 24.2 1.51 13.4 - 1.51 3 47.9 12.5 5.93 12.8 18.9

Claims (24)

1. A process for preparing ethanol by reacting methanol with carbon monoxide and hydrogen, which comprises conducting reaction in the presence of a combination of manganese and ruthenium as a catalyst.

2. A process according to claim 1 wherein iodine or an iodine compound is present in the catalyst as a promotor.

3. A process according to either of claims 1 or 2 wherein methyl acetate is present.

4. A process according to any one of claims 1 to 3 wherein the catalyst source of manganese is metallic manganese, manganese carbonyl compound, manganese salt of an organic acid, manganese acetylacetonate or inorganic manganese compound.

5. A process according to claim 4, wherein the catalyst source of manganese is manganese formate, manganese acetate, manganese n-butyrate, manganese benzoate or manganese naphthenate.

6. A process according to claim 4 wherein the catalyst source of manganese is manganese dioxide, manganese carbonate or manganese chloride.

7. A process according to any one of claims 1 to 6 wherein the catalyst source of ruthenium is a halide, oxide, carbonyl compound, phosphide, oxo acid salt of ruthenium.

8. A process according to any one of claims 1 to 3 wherein manganese (II) acetate and ruthenium chloride are used as the catalyst.

9. A process according to any one of claims 2 to 8 wherein the iodine compound is methyl iodide, sodium iodide, potassium iodide, lithium iodide or iodic acid.

1 0. A process according to any one of claims 1 to 9 wherein the manganese is used at a molar ratio of manganese to methanol of 0.0001 -0. 1:1 and the ruthenium is used at a molar ratio of ruthenium to methanol of 0.0001-0.05:1.

11. A process according to any one of claims 1 to 10 wherein the manganese is used at a molar ratio of manganese to methanol of 0.005-0.05:1 and the ruthenium is used at a molar ratio of ruthenium to methanol of 0.001-0.02: 1.

1 2. A process according to any one of claims 2 to 11 wherein the iodine or iodine compound is used at a molar ratio of iodine or iodine compound to methanol of 0.001-0. 1:1.

1 3. A process according to claim 1 2 wherein the iodine or iodine compound is used at a molar ratio of iodine or iodine compound to methanol of 0.005-0.05:1.

14. A process according to claim 1 wherein the methyl acetate is used at a molar ratio of methyl acetate to methanol of 0.01 5.0:1.

1 5. A process according to any one of claims 3 to 14 wherein the methyl acetate is used at a molar ratio of methyl acetate to methanol of 0.1~2.0:1.

16. A process according to any one of claims 1 to 1 5 wherein reaction temperature is 120-300"C.

1 7. A process according to claim 1 6 wherein reaction temperature is 150-250"C.

1 8. A process according to any one of claims 1 to 1 7 wherein the molar ratio of carbon monoxide to hydrogen is 4:1-1:4.

1 9. A process according to claim 1 8 wherein a molar ratio of carbon monoxide to hydrogen is 1:2-2:1.

20. A process according to any one of claims 1 to 1 g wherein the reaction is carried out under pressure.

21. A process according to claim 20 wherein the reaction pressure is 50 kg/cm2 or above.

22. A process according to claim 21 wherein the reaction pressure is 100-500 kg/cm2.

23. A process according to claim 1 substantially as hereinbefore described specifically with reference to the Examples.

24. Ethanol when produced by a process according to any one of claims 1 to 23.