KR960004769B1 - Process for the preparation of ethanol from methanol - Google Patents

Abstract

carbonylation of methanol in the gas phase with CO, opt. mixed with H2 with a catalyst and a cocatalyst under mild conditions and high GHSV to produce a mixture(I) of acetic acid and methyl acetate; separating by distillation of (I) a low boiling fraction comprising methyl acetate and halide, and a high boiling fraction comprising acetic acid; separating the methyl acetate from the halide, and recycling the latter, opt. with a minor portion of methyl acetate, to the carbonylation reactor; and hydrogenating the separated methyl acetate in presence of a copper-contg. catalyst to produce ethanol in high yield. The ethanol is economically obtained in high yield. The methanol obtained together with ethanol may be recycled to the carbonylation.

Description

How to prepare ethanol from methanol

The present invention relates to a process for producing ethanol from methanol.

Ethanol is not only an industrially important raw material, but also occupies an important position in food and medicine. Commercial production of ethanol is produced by fermentation from raw materials obtained from sugar, starch and similar plants. In particular, industrial use is made by gas phase reaction of ethylene, which is a major raw material of the petrochemical industry, with water in a solid acid catalyst. do.

Recently, various petrochemical raw materials other than petroleum have been searched for. Currently, petroleum substitutes include coal and natural gas, which are lower carbon sources. According to this trend, studies are being actively conducted to produce ethanol from coal and natural gas, which are the most powerful petroleum alternative carbon sources, and as a result, several methods have been attempted.

Catalytic reaction studies have been attempted to synthesize higher alcohols directly from synthesis gas, but all of these cases require harsh reaction conditions at high pressures, and the selectivity of products is very poor. These results are described in detail in European Patent Application No. 0,172,431 A2 filed by Dow Chemical Co. and U.S. Patent No. 4,122,110 filed by IEP, France. These patents describe that only 30-60% of the alcohol product is methanol, with the remainder being a mixture of higher alcohols than ethanol.

On the other hand, in Japan, the results of research conducted under the CI Chemical Development Plan were recently announced, but there was no significant progress in the catalytic reaction for synthesizing pure ethanol directly from syngas.

Therefore, a research into a reaction for obtaining ethanol by preparing primary methanol from syngas by a commercially established catalytic process and then reacting with syngas again by a catalytic reaction known as homologation is performed. At this time, the best catalytic reaction was about 80% ethanol selectivity (compared to methanol used), but this also has a lot of problems in the process. Related patents are described in detail in British Patent No. 2,053,915 A filed by BP Corporation, in which the reaction conditions require high reaction pressures and high reaction temperatures, and low value added by-products. A considerable amount is produced. These reactions were already published long ago in J. Am. Chem. Soc 71, 4160 (1949), but in recent years, a lot of research is being conducted on fuel. At this time, various catalysts such as ruthenium, cobalt, rhodium, palladium, platinum, osmium, iridium, chromium, manganese, iron, and nickel were used, but the conversion rate was low, and in particular, the selectivity was poor, thus not taking practicality of the reaction. [D. W. See S. W. Slocum, Catalyst in Organic Synthesis, Academic Press, 245-276 (1980). The main byproducts here are ethers, esters, acetals, organic acids, higher alcohols and the like. Therefore, there is no known catalytic process for producing highly selective ethanol that has industrial significance.

However, methanol is a compound synthesized primarily from a lower carbon source via a synthesis gas by a commercial process and is a material having high economic feasibility that can be supplied in the long term. Therefore, efforts to synthesize organic compounds with these starting materials are very important, especially ethanol has a great meaning.

Currently used homologation catalysis can produce mixed alcohols that can be mixed with fuel, but all of these catalysis reactions contain about 50% of unreacted methanol after the reaction, and ethanol or more pentane. Various alcohol mixtures are obtained up to all. Thus, no direct homologation catalysis to obtain pure ethanol is known.

On the other hand, a method of esterifying acetic acid to make methyl or ethyl acetate and hydrogenating it to synthesize ethanol has recently been attempted. For example, WO83 / 034409 and UK Patent Publication No. 2 162 172 A, filed by Davey Mckee Ltd., are produced by a process for acetic acid production by carbonylation of methanol currently commercialized. A process for producing ethanol is disclosed by esterifying one acetic acid to obtain a methyl ester and hydrogenating it. The carbonylation reaction of methanol described in this patent proceeds in a liquid phase reaction, in which the acetic acid is produced and a small amount of methyl acetate is produced as a by-product.

Therefore, methyl acetate is synthesized by esterification of the resulting acetic acid with methanol again, and then a hydrogenation reaction is performed, so that one more step is added, and another separation step is also required. However, the advantage of this method is that ethanol can be produced with high selectivity, and more importantly, ethanol is synthesized from syngas and methanol synthesized therefrom, resulting in the selectivity of producing ethanol from lower carbon source materials. It is a high process.

BASF Aktiengesellschaft and Humphreys and Glassgow have also reported similar matters, as reported in EP 56488 and EP 100406. Acetic acid was converted directly to ethanol without the esterification step. However, not only the esterification step was omitted, but also a problem of separating ethanol and water was caused, and since the hydrogenation reaction proceeds under a high pressure of 400 psi, the equipment cost is high. In this regard, B. Juran and R. V. Porcelli of Halcon SDGroup compared economics by dividing them into carbonyl reaction, esterification reaction and hydrogenation reaction (hydrocarbon processing). See page 85, October 1985]. Halcon is synthesized acetic acid in the liquid phase using a catalyst that does not use rhodium metal, and then methyl ester through the esterification reaction with methanol to produce ethanol and methanol by hydrogenation. This mixture is separated and methanol is again administered to the acetic acid synthesis step. However, all of the ethanol synthesis processes by hydrogenation of methyl acetate, including the Halcon method, have problems in the methylacetate production step.

Conventional methyl acetate production methods are roughly divided into two methods: direct methanol production and acetic acid production, followed by esterification with methanol to produce methyl acetate. Both of these methods have problems. In the first method, the reaction is mainly liquid phase, so that direct methylacetate production is problematic not only for selectivity and reactivity but also for its separation. The second method adds an additional burden on the process due to the addition of a reaction step called an esterification reaction.

The present inventors can complement various difficult problems of the liquid phase process by adopting the gaseous phase methanol carbonylation catalyst process, and furthermore, by adjusting the reaction conditions, selectively preparing methyl acetate instead of acetic acid, and competing with the ester hydrogenation catalyst reaction Not only is a new ethanol production method possible, methanol has been produced as a by-product of the final reaction, and thus it can be recycled and used to achieve the present invention.

It is therefore an object of the present invention to provide a process for the efficient production of ethanol from methanol in a series of processes.

An object of the present invention is the first step to obtain acetic acid and methyl acetate by the gas phase carbonylation of methanol with carbon monoxide in the presence of a rhodium catalyst and a halide cocatalyst for the carbonylation reaction, acetic acid from a mixture of the resulting acetic acid and methyl acetate 2nd step of separating the acetic acid, 3rd step of separating the halide-based cocatalyst and methyl acetate from the remaining reaction mixtures, and the presence of a hydrogenation catalyst containing Cu oxide as a main component by introducing the separated methyl acetate into a hydrogenation reactor. The fourth step of obtaining Methanol and ethanol by hydrogenation of methyl acetate at a temperature of 0.3-6.0, 200-300 ° C. and a pressure of 350-700 psig, and separating ethanol from the resulting mixture and recovering methanol in the first step Method for producing ethanol from methanol consisting of the fifth step to recycle To be achieved.

Hereinafter, the present invention will be described in detail.

The first step of the method for producing ethanol according to the present invention is a step of forming acetic acid and methyl acetate by gas phase carbonylation of methanol with carbon monoxide in the presence of a carbonylation catalyst and a halide promoter.

The gas phase methanol carbonylation reaction in the first process was carried out at atmospheric pressure and carbon monoxide pressure of 100 to 1,000 psi and 100 in the presence of a rhodium catalyst as described in patent application 1115 filed on June 30, 1992 by the same applicant as the present invention. The reaction can be carried out by reacting methanol and carbon monoxide at a molar ratio of 1: 1 to 1: 100 at a temperature of -400 ° C.

A halide catalyst used in the co-catalyst is _{CH 3 I, CH 3 Br,} CH 3 Cl, I 2, Br 2, Cl 2, HI, HBr There are, such as HCL, preferably CH ₃ I.

By adjusting the reaction conditions of the gas phase carbonylation reaction, it is possible to control the production rate of methyl acetate and acetic acid produced. In the case of carrying out the carbonylation reaction under more severe reaction conditions, for example, increasing the reaction temperature increases the production rate of acetic acid, whereas under mild reaction conditions, the production rate of methyl acetate increases.

Therefore, the production rate of the product can be easily adjusted as needed.

Next, acetic acid is separated from the carbonylation reaction mixture of methanol in the second step, and then methyl acetate and the halide cocatalyst are separated in the third step. This separation process can be carried out according to a conventional separation method, it can be performed integrated in a one-step process.

The separated promoter is recycled to the carbonylation reactor of the first step, thereby improving economic efficiency. Methyl acetate is sent to the next hydrogenation reactor.

In the fourth step, methanol and ethanol are obtained by hydrogenating the methyl acetate obtained in the third step using a hydrogenation catalyst. Methyl acetate is hydrogenated to produce one molecule of methanol and ethanol.

The hydrogenation reaction of methyl acetate is carried out in the presence of a hydrogenation catalyst at a liquid hourly space velocity (LHSV) of methyl acetate of 0.3-6.0, a temperature of 200-300 ° C. and a pressure of 350-700 psig.

More preferably the hydrogenation reaction is carried out at 0.5 LHSV of methyl acetate, at a temperature of 260 ° C. and at a pressure of 600 psig.

As a catalyst for promoting the hydrogenation reaction, a compound containing Cu oxide as a main component is used. For example, Cu-Co-Zn, Cu-Zn-Fe, Cu-Co-Zn-Fe-Ca, and Cu-Co-Zn-Mo-Na are mentioned, Preferably Cu-Co-Zn is used do.

The hydrogenation catalyst may be Zn (OAc) ₂ .2H ₂ O, Cu (OAc) ₂ .2H ₂ O, Cu (OAc) ₂ .H ₂ O, Fe (NO ₃ ) ₃ .9H ₂ O or (NH in distilled water. _{4) 6} M _O7 O ₂₄ · can be produced by after 4H ₂ reaction by (NH ₄₎ was added to ₂ CO ₃ distilled water solution to O solution, dried overnight at about 120 ℃ and calcined to 450 ℃ for about 16 hours.

In addition to the components mentioned above, Ca, Na, Pt, Pd, Rh, Ru can be added in the form of salts of Cl or NO ₃ , with salts of Ca (NO ₃ ) ₂ 4H ₂ O, NaOH, K ₂ PtCl ₄ , PdCl ₂ , RhCl ₃ , RnCl ₃ was added to 0.5% by weight of the total metal.

The counter anions of the metals used are not significantly affected by their type and can be anything as long as they can burn off after sintering and form the remaining metal oxides.

The fifth step is a step of separating and recycling unreacted methanol and methyl acetate in the initial reaction product as well as methanol generated in the fourth step, and separating ethanol. Ethanol produced by the hydrogenation reaction can be separated from the product mixture by conventional known methods. In the method of the present invention, methanol is used as an initial reactant to obtain methyl acetate, and ethanol is prepared therefrom. The methanol produced as a by-product of the final reaction is recovered and recycled to be used in a carbonylation reaction process. Therefore, by-products can be recycled and used as a very economical ethanol production method.

Hereinafter, the present invention will be described in more detail. However, the present invention is not limited to these examples.

Example 1

The catalyst was prepared by supporting RhCl ₃ and LiI on activated carbon in an aqueous solution and then sintering at 300 ° C. on 400 mol% of Li based on the amount of Rh + Rh based on the amount of activated carbon on the activated carbon carrier. 5 g of the catalyst was filled in a titanium reaction tube of about 1.27 cm (1/2 inch) in diameter and 40 cm in length, and the upper 15 cm and 15 cm of the upper part of the reaction tube were filled with alkali-treated glass fibers to increase the catalyst bed length. It was made into 10 cm, and the titanium tube of about 0.64 cm (1/4 inch) in diameter was put in the middle of the tube, and the thermoelectric pair was attached. The outside of the reaction tube was covered with an oil jacket to heat the reaction tube with fruit. Methanol and carbon monoxide were introduced into the reactor to be 1: 2: 3, and as a promoter, in the presence of 10 mol% CH ₃ I based on the amount of methanol, the reaction pressure was 200 psi and the reactor internal temperature was 270 ° C or higher. The reaction was carried out.

The conversion of methanol and the yield of acetic acid according to gas space velocity (GHSV) under the above reaction conditions are shown in Table 1 below.

GHSV = Gas hourly space velocity (hr ^-1 ): This is a measure of how many times the volume of reactant per hour passed through the catalyst volume in the gaseous state.The higher the CHSV, the shorter the contact time between the catalyst and the reactant. And the amount of reactant processed per unit time increases.

Example 2

The same catalyst was used under the same conditions as in Example 1 except that the reaction pressure was 150 psi and the reaction temperature was 233 ° C. The results obtained under the above reaction conditions are shown in Table 2 below.

As can be seen in Tables 1 and 2, even when the same catalyst was used, the production ratio of methyl acetate and acetic acid could be adjusted by different reaction conditions. That is, it can be seen that a large amount of methyl acetate is produced from the result of Example 2, in which the reaction conditions are relatively mild.

Example 3

The reaction was carried out in the same manner as in Example 1 except that 400 mol% of Li activated carbon catalyst was used as the catalyst based on the amount of Rh + Rh of 1.8% by weight, and the reaction conditions were further relaxed at 270 ° C. under CO pressure of 150 psi. The results thus obtained are shown in Table 3 below.

Example 4

The reaction was carried out in the same manner as in Example 1 except that 200 mol% of Na was supported on activated carbon based on the amount of Rh + Rh of 0.6 wt% based on the amount of activated carbon, and the reaction temperature was 240 ° C. Was performed. The results thus obtained are shown in Table 4 below.

Example 5

The reaction was carried out in the same manner as in Example 1, using a catalyst in which RhCl ₃ and IrCl ₃ were supported on activated carbon at a molar ratio of 1: 0.5, and the reaction temperature was 225 ° C. The results thus obtained are shown in Table 5 below.

Example 6

22 g of Zn (OAc) ₂ · 2H ₂ O, 25 g of Co (OAc) ₂ · 2H ₂ O, 20 g of Cu (OAc) ₂ · H ₂ O, and 1.46 g of Fe (NO ₃ ) ₃ · 9H ₂ O are dissolved in 500 ml of distilled water. And stirred at room temperature. When the solution became clear, a solution in which 40 g of (NH ₄ ) ₂ CO ₃ was dissolved in 400 ml of distilled water was slowly added thereto. After the solution was added, the mixture was stirred for about 1 hour, filtered through a filter paper, and the precipitate was washed with distilled water. The washed precipitate was dried at about 120 ° C. in a vacuum furnace overnight, and then calcined at 450 ° C. for 16 hours in a heating furnace to prepare a hydrogenation catalyst.

When preparing a catalyst in which the Mo component was added instead of the Fe component, 0.368 g of (NH ₄ ) ₆ M ₇ O ₂₄ .4H ₂ O was used.

Example 7

2.5 g of the catalyst prepared in Example 6 was charged to a fixed bed reactor, reduced to hydrogen at 350 ° C. for 2 hours at atmospheric pressure, and methyl acetate was transferred to the reactor through a preheating unit so that the LHSV was 4.4. And hydrogenation reaction at a pressure of 500 psig. The reaction result is as follows.

Example 8

2.5 g of the catalyst prepared in Example 6 was charged to a fixed bed reactor, and reduced in the same manner as in Example 7, after which the methyl acetate was transferred to the reactor through a preheating unit so as to be LHSV 1 and hydrogen 5 times in molar ratio relative to methyl acetate. Inflow was carried out so that a hydrogenation reaction was performed at a temperature of 220 ° C. and a pressure of 400 psig. The reaction result is as follows.

Example 9

4 g of a Cu-Co-Zn-Fe catalyst was charged to a fixed bed reactor, reduced in the same manner as in Example 7, and then hydrogenated at a temperature of 260 ° C. The reaction result is as follows.

The ethanol manufacturing method of the present invention improves the economics by improving all the existing techniques to improve the efficiency of each step, and requires a separate esterification step by producing methyl acetate directly in the carbonylation reaction of methanol and carbon monoxide. The cost of raw materials can be reduced by recycling the methanol byproduct obtained in the final step to the carbonylation step.

Claims (5)

A first step of obtaining acetic acid and methyl acetate by gas-phase carbonylation of methanol with carbon monoxide under a rhodium catalyst and a halide-based promoter for carbonylation reaction, and a second step of separating acetic acid from a mixture of the resulting acetic acid and methyl acetate In the third step of separating the acetic acid and the acetate halide co-catalyst and the methyl acetate into the remaining reaction mixture, the separated methyl acetate is introduced into the hydrogenation reactor, and the LSHV of methyl acetate is present in the presence of a hydrogenation catalyst composed mainly of Cu oxide. A fourth step of hydrogenating at a temperature of = 0.3-6.0, 200-300 ° C. and a pressure of 350-700 psig to obtain methanol and ethanol, and a fifth step of separating ethanol from the resulting mixture and recovering methanol to recycle to the first step. Method for producing ethanol from methanol consisting of. The method of claim 1, wherein the second process and the third process are performed in one process. The method of claim 1, wherein the halide promoter is recycled to the carbonylation process after separation. The hydrogenation catalyst used for hydrogenation of methyl acetate is composed of Cu-Co-Zn, Cu-Zn-Fe, Cu-Co-Zn-Fe-Ca and Cu-Co-Zn-Mo-Na. And selected from the group. The method of claim 1 wherein the halide promoter is CH ₃ I.