JPS5846490B2 - Method for purifying impure alcohol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for continuous purification of impure ethyl alcohol.

In particular, gas-phase hydrogenation of "impure ethyl alcohol containing many low-boiling point impurities" (hereinafter abbreviated as "impure alcohol"), which is produced as a by-product when crude ethyl alcohol produced by fermentation is purified by a known continuous distillation method. Concerning a continuous purification method by.

Conventionally, impure alcohol has no commercial value as it contains a lot of bad odor and coloring substances, and polymerizes during storage, resulting in significant bad odor and coloration. , which removes bad odors and colored substances and is used as an alcohol-based solvent for special purposes, such as printing ink solvents, etc. However, this method not only has a very low yield, but also removes auxiliary materials due to chemical treatment. In addition to the high refining costs due to the use of large amounts of water, there are also problems with wastewater treatment.

Furthermore, the impure alcohol purified by this method still has some unpleasant odor and as time passes, it is inevitable that it will become colored again due to polymerization of the remaining impurities. However, in recent years, the above refining methods have been avoided, and the reality is that they are simply incinerated as fuel.

The present inventor provides a purification method using continuous gas phase hydrogenation that overcomes the above-mentioned problems in purifying impure alcohol.

Industrial methods for producing ethyl alcohol include a synthesis method using ethylene water-use reaction, and a long-established method for producing ethyl alcohol by fermentation of molasses, sweet potatoes, grains, etc.; ,
Low boiling point impurities such as ethyl acetate and acetal and high boiling point impurities such as isoamyl alcohol and isobutyl alcohol are produced as by-products.

During continuous distillation purification, high-boiling point impurities are extracted from the middle stage of the distillation column as an ethyl alcohol solution containing high-boiling point impurities, while low-boiling point impurities are extracted from the top of the extractive distillation column. It is separated as an ethyl alcohol solution containing

Among the ethyl alcohols containing these impurities, the composition of the impure alcohols separated as low-boiling point impurities is shown in Table 1, which mainly consists of acetaldehyde, acetone, ethyl acetate, acetal, methyl alcohol, ethyl alcohol, water, etc. However, the composition of these impure alcohols varies depending on the raw materials used during fermentation, the operating conditions of the distillation column, etc.
It fluctuates greatly.

The foul odor and coloring of this impure alcohol is caused by the polymerization of carbonyl compounds contained in trace amounts, such as diacetyl, as well as acetaldehyde, etc. contained in large quantities, and the foul odor and colored substances further increase over time during storage after separation. It will be done.

Conventionally, the impure alcohol is treated with chemicals, such as using an aqueous caustic alkali solution, to polymerize or decompose bad odors, coloring substances, and other impurities, and then purified to some extent by distillation, and then used as an alcohol-based solvent for special purposes, such as printing ink. Although some solvents are commercially available, the above method uses a large amount of caustic alkali to remove bad odors and colored substances, and the pH of the wastewater after treatment is high, so it not only requires wastewater treatment equipment. The work environment is deteriorated due to bad odors during loading and unloading.

As can be seen from the composition of impure alcohol shown in Table 1, impurities can be removed by treatment with caustic alkali, and ethyl acetate can be hydrolyzed and partially recovered as ethyl alcohol, but acetal, which has an aldehyde odor, is stable against alkali. However, since it cannot be decomposed and removed even with caustic alkali treatment, and other caribonyl compound impurities polymerize, impure alcohol with a high purity of ethyl alcohol, such as sample A1 manufactured by Company A in Table 1, is usually used. Since the refining yield and product purity of impure alcohols other than the one sample manufactured by Company A in Table 1 are extremely poor, they are not purified by chemical treatment and are either incinerated as is or used as fuel. It's just being used.

From the standpoint of resource conservation, there has been a desire for an effective purification method for these impure alcohols.

The present inventor developed the present invention based on the technical idea that since impurities in impure alcohol are composed of oxygen-containing unsaturated compounds such as aldehydes and ketones, malodors and colored substances can be removed by reduction. completed.

Among the reductive purification methods, there are gas phase methods and liquid phase methods.As for the liquid phase method, there is a Raney nickel catalyst that is commonly used in laboratories, and it is fully satisfactory for reductive purification of impure alcohol. However, it is not suitable for continuous purification on an industrial scale.

Furthermore, as a method for purifying ethyl ether, a continuous liquid phase hydrogenation purification method has been disclosed (Japanese Unexamined Patent Publication No. 73711/1983), but when used for purifying impure alcohol, the catalyst becomes deactivated in an extremely short period of time. .

Although the liquid phase method is energy saving, it cannot be used as a stable industrial process.

On the other hand, as a gas phase hydrogenation refining method, there is a known method for refining crude ethyl alcohol purified by ethylene water condensation using a hydrogenation catalyst.

(Special Publication No. 33-3162, Chemistry and Industry
ry) August 10 issue (1953) S28-531) This gas phase hydrogenation purification is a method of hydrogenating impurity aldehydes and converting them into the corresponding alcohols, and the reaction temperature is usually 100 to 110°C. , reaction pressure 1-2 g/d
It is held near G.

The impurity aldehydes in the crude ethyl alcohol usually weighs less than 1.5 weight φ at most, so even if the reaction conditions such as the molar ratio of hydrogen to alcohol and the reaction space velocity are changed significantly, the purification effect and catalyst life will be affected. It is well known among those skilled in the art that this has little effect.

However, as shown in Table 1, the impure alcohol by-produced when crude ethyl alcohol produced by fermentation is purified by continuous distillation is crude ethyl alcohol produced by synthesis of reducing substances such as aldehydes. Since the amount of catalytic acid is significantly higher than that of aldehydes contained in the water, sometimes up to several tens of weight percent, known hydrogenation purification methods result in significant deactivation of the catalyst, and have not been adopted industrially.

A gas phase hydrogenation purification method for crude ethyl ether has also been disclosed (Japanese Patent Publication No. 54-32763);
The purpose of hydrogenation purification can be achieved even if the reaction conditions are changed to fairly miscible conditions, but for impure alcohols containing aldehydes, which sometimes amount to several tens of weight percent, known hydrogenation methods are difficult to achieve in terms of catalyst life. It was not used industrially.

The present inventor completed the present invention as a result of exploring various conditions for a continuous gas phase hydrogenation purification method for impure alcohols that can maintain the activity of the catalyst even for impure alcohols that contain aldehydes sometimes in excess of several tens of weight percent. This is what I did.

That is, the continuous gas phase hydrogenation refining method of the present invention uses a hydrogenation catalyst, the reaction temperature is 80 to 150°C, and the reaction pressure is normal pressure to 1.
0Kt/dG, reaction space velocity 50-10.000 h
r'-' (however, the reaction space velocity (hr-') is the total volume of the feedstock system per hour (m8, converted to standard conditions) divided by the apparent volume of the catalyst (m3)). In particular, the essential requirements are that the reaction molar ratio (the number of moles of hydrogen gas supplied per hour divided by the number of moles of impure alcohol supplied per hour) is 1 or more, and the molar ratio of hydrogen to acetaldehyde (the number of moles of hydrogen gas supplied per hour divided by the number of moles of impure alcohol supplied per hour) is 1 or more. (divided by the number of moles of acetaldehyde contained in the impure alcohol supplied per hour) is set to 5 or more, the catalyst activity decreases significantly when conventionally performing gas phase hydrogenation of impure alcohol, so continuous gas phase Although hydrogenation purification had not been adopted, the present invention was completed by discovering that continuous gas phase hydrogenation purification could be carried out stably over a long period of time without deactivation of the catalyst.

The method of the present invention is not only extremely effective in hydrogenating and refining impure alcohol, but also provides a high yield and does not require wastewater treatment equipment. Impure alcohol originally has a bad odor, which worsens the working environment. However, since it is a closed and continuous type, there is no longer any deterioration of the working environment due to these bad odors.

The present invention will be explained in detail below.

The impure alcohol for raw materials as used in the present invention refers to impure alcohol containing many low-boiling point impurities, which is produced as a by-product when crude ethyl alcohol produced by fermentation is purified by continuous distillation, and contains many high-boiling point impurities. Impure ethyl alcohol (so-called fusel oil) does not contain momme.

The reactor used in the present invention is a normal fixed bed catalytic hydrogenation reactor, and the raw material impure alcohol is in a gaseous state.
It is preferable to feed the reaction column from the top or the bottom, and to feed hydrogen by cocurrent flow.

The hydrogenation catalyst used in the method of the present invention is preferably a cylindrical, spherical or crushed granular nickel catalyst for use in a conventional fixed bed catalytic reaction apparatus.

The carrier may be commonly used diatomaceous earth, bentonite, alumina, etc., and is not particularly limited.

The nickel content is not particularly limited, but is preferably 40
It is preferable that the weight of the rice cake is higher than that of the rice cake.

The reaction conditions for continuous gas phase hydrogenation of impure alcohol are a reaction pressure of normal pressure to 10 Ky/mG, preferably normal pressure to 5 Kp/dG.
, reaction temperature 80-150°C, preferably 90-130°C
, reaction space velocity 50~io, oo.

hr', preferably 100-3,000hr'
The hydrogenation is carried out at a reaction molar ratio of 1 or more, preferably 2 to 10, and a molar ratio of hydrogen to acetaldehyde of 5 or more, preferably 10 or more.

The purpose of hydrogenation purification can be achieved even at normal reaction pressure, but after cooling the reaction mixture, the gas and liquid are separated, and in some cases, unreacted hydrogen gas must be partly recycled and partly discharged to the outside of the system. .

In order to recover the ethanol entrained in the hydrogen gas discharged outside the system, it is more advantageous to separate the gas and liquid under pressure, so it is more effective to operate the reaction system under pressure. .

10 from the viewpoint of reaction temperature and pressure equipment construction cost, etc.
Ky/dG or less is preferable.

A reaction temperature of 150° C. or higher is not preferred because not only side reactions become significant, but also the hydrogenation rate of acetaldehyde becomes unfavorable in terms of reaction equilibrium and the amount of residual acetaldehyde increases.

If the temperature is below 80°C, the reaction rate is slow, which not only lowers the hydrogenation rate of acetaldehyde, but also lowers the temperature below the dew point, which is undesirable because the catalyst bed may become wet and the catalyst may be deactivated.

If the reaction space velocity is less than 50 hr''-1, it is not industrially economical, and if it is more than 10,000 hr', the purpose of hydrogenation purification cannot be achieved.

Furthermore, it is extremely important to set the reaction molar ratio to 1 or more and the hydrogen to acetaldehyde molar ratio to 5 or more, which are particularly essential requirements in the method of the present invention.

If the reaction molar ratio is less than 1 or the molar ratio of hydrogen to acetaldehyde is less than 5, the polymerization reaction of acetaldehyde will proceed and the polymerization product will poison the active sites of the catalyst, resulting in a rapid decrease in catalyst activity.

Catalysts deactivated in this way can no longer be reactivated.
It does not return to its original activity.

Therefore, when industrially purifying impure alcohol by continuous gas phase hydrogenation, from the viewpoint of catalyst stability, it is important to keep the reaction molar ratio at least 1 and the molar ratio of hydrogen to acetaldehyde at 5 or more.

More preferably, when the reaction molar ratio is 2 or more and the molar ratio of hydrogen to acetaldehyde is 10 or more, a fully satisfactory purified product can be obtained.

In terms of reaction, the higher the reaction molar ratio, the more effective it is, but from the economic point of view, such as the size of the reaction tower, a reaction molar ratio of 10 or less is preferred.

By using the method of the present invention, impure alcohols having any of the compositions shown in Table 1 can be purified by hydrogenation in a stable manner and with good yield.

Furthermore, all acecool having an aldehyde odor, which could not be decomposed and removed by conventional caustic alkaline treatment, is recovered as ethyl alcohol, resulting in a high yield and a purified product free of unpleasant odor.

The impure alcohol that has been hydrogenated and purified in this way, either as it is or in combination with a conventionally known rectification method, is an alcohol-based solvent that has no odor or color, does not polymerize during storage, and is harmless from an industrial hygiene perspective. As, various paints,
It can be widely used in the production of paint diluents (thinners), printing inks, adhesives, and for cleaning machinery and equipment.

The present invention is applicable to any case in which a conventional distillation method is combined before or after continuous gas phase hydrogenation purification, or before and after continuous gas phase hydrogenation purification.

In particular, when impure ethyl alcohol is stored or left for a long period of time, a colored precipitate polymer, so-called Harz, is formed.
An important aspect of the present invention is a method in which Harz is separated and then hydrogenated in the gas phase in a pretreatment step for evaporation or distillation.

The present invention has been described in detail above, and the method of the present invention provides a continuous gas phase hydrogenation refining method that has not been available in the past for the purification of impure alcohol. It is possible to purify impure alcohol with a high yield, 2. It prevents deterioration of the working environment due to bad odors, and 3. Since no other chemicals are used, there is no need for wastewater treatment equipment, and the resulting product is unpleasant. This method produces an alcohol-based solvent that has no odor.

Additional explanation will be provided below using some examples.

Example 1 As an impure alcohol, a reaction molar ratio of 3 was applied to A2 sample manufactured by Company A in Table 1, and a molar ratio of hydrogen to acetaldehyde at this time was 21.
A commercially available nickel catalyst for a fixed bed catalyst device, which had been activated in advance by a conventional method and whose activity was stabilized for 10 hours, was mixed with hydrogen so that The reaction pressure was normal pressure, the reaction temperature was 110°C, and the reaction space velocity was 780 h.
The reaction was carried out at r'.

After cooling the reaction product with ice water, the hydrogenated product was analyzed by gas chromatography.

Table 2 shows the properties and composition of the hydrogenated product. The hydrogenated product was colorless and transparent, had no unpleasant odor, and was an ethyl alcohol solution with a slight ethyl acetate odor.

Also, the acetaldehyde was less than 0.01 weight φ, which was lower than the conventional commercially available product (containing 0.22 weight φ of acetaldehyde), and was of good quality.

For comparison, Table 2 also shows the properties and compositions of impure alcohols purified by caustic alkali treatment and distillation and commercially available as special purpose solvents.

Example 2 An A4 sample manufactured by Company B in Table 1 was used as an impure alcohol, and hydrogen was mixed so that the molar ratio of hydrogen to acetaldehyde at this time was 4, and the molar ratio of hydrogen to acetaldehyde was 18. Introduced into the same apparatus as 1, and at a reaction pressure of 2.3 °C
f1G, reaction temperature 110℃, reaction space velocity 970hr
' was used to react.

The hydrogenated product was analyzed in the same manner as in Example 1.

Hydrogen raw. *Table 2 shows the properties and composition of the product.

This hydrogenated product was an ethyl alcohol solution that was colorless and transparent, had no unpleasant odor, and had a slight odor of ethyl acetate.

Also, the amount of acetaldehyde was 0.05% by weight less than that of conventionally commercially available products and was of good quality.

Example 3 Using the same sample as in Example 1 as impure alcohol,
Hydrogen was mixed so that the reaction molar ratio was 1 and the molar ratio of hydrogen to acetaldehyde at this time was 7, and the mixture was introduced into the same apparatus as in Example 1 using 15 rul of the same newly activated catalyst as in Example 1. The reaction was carried out for a long time at a reaction pressure of normal pressure, a reaction temperature of 130° C., and a reaction space velocity of 780 hr'.

The hydrogenated product was analyzed in the same manner as in Example 1.

Figure 1 shows the changes in the hydrogenation rate of acetaldehyde and acetone.

The catalyst activity became stable after about 10 hours and remained stable even after 28 hours.

Comparative Example 1 Using the same sample as in Example 2 as impure alcohol,
The same reaction conditions as in Example 3 were carried out using the same apparatus as in Example 1, using the same newly activated catalyst 15TrLl as in Example 1 (however, due to the high content of acetaldehyde in this sample, hydrogen The molar ratio of acetaldehyde was 4.5.

) That is, reaction molar ratio 1, reaction pressure normal pressure, reaction temperature 130°C
, when the reaction was carried out at a reaction space velocity of 780 hr',
The catalyst activity decreases and after 11 hours the acetaldehyde in the hydrogenated product is 3. lO weight rice cake (hydrogenation rate 84.Omo
1), making hydrogenation purification impossible.

This catalyst with decreased activity was reactivated by a conventional method and the hydrogenation reaction was attempted again, but the activity did not improve.

Example 4 Using the same sample as in Example 2 as the impure alcohol, hydrogen was mixed so that the reaction molar ratio was 4, and the molar ratio of hydrogen to acetaldehyde at this time was 18, and Example 1 was newly activated. The mixture was introduced into the same apparatus as in Example 1 using 15 rnl of the same catalyst as above, and the reaction was carried out for a long time at normal pressure, reaction temperature 110° C., and reaction space velocity 730 hr.

The hydrogenated product was analyzed in the same manner as in Example 1.

No acetaldehyde after 24.5 hours of reaction time
．． 02 weight φ (hydrogenation rate 99.9 molφ) and catalyst activity were stable.

The properties and composition of the hydrogenated product after 24.5 hours are shown in Table 2.

Examples 5 to 13 Using the same sample as in Example 1 as impure alcohol,
A reaction was attempted using the same apparatus as in Example 1, using the same catalyst as in Example 1, and changing the reaction conditions.

Table 3 shows the reaction conditions and reaction results for gas phase hydrogenation.

All of the hydrogenated products were colorless and transparent, had no unpleasant odor, were ethyl alcohol solutions with a slight ethyl acetate odor, and were of good quality with a lower amount of acetaldehyde than conventional commercially available products.

It is clear that the reaction molar ratio and reaction temperature are important to enhance the gas phase hydrogenation purification effect.

[Brief explanation of the drawing]

Figure 1 shows the change in hydrogenation rate over time.
indicates acetaldehyde. B is acetone

Claims (1)

[Claims] 1. Impure ethyl alcohol containing many low-boiling point impurities, which is produced as a by-product during continuous distillation purification of crude ethyl alcohol produced by a fermentation method, is heated in the presence of a hydrogenation catalyst at a reaction pressure of normal pressure to 10Ky/cIftG, reaction temperature 80-150
°C, reaction space velocity 50 to 10,000 hr-', ratio of the number of moles of hydrogen to the number of moles of impure ethyl alcohol, that is, the reaction molar ratio is 1 or more, and the ratio of the number of moles of hydrogen to the number of moles of acetaldehyde in the impure ethyl alcohol. 1. A continuous purification method for impure ethyl alcohol, characterized by carrying out gas phase hydrogenation under conditions of 5 or more. 2. The continuous purification method according to claim 1, wherein a residual fraction containing a resinous substance is extracted from the bottom of the evaporator when impure ethyl alcohol is evaporated into the gas phase before gas phase hydrogenation. 3. The continuous purification method according to claim 1, in which vapor phase hydrogenation is further combined with a distillation method before, after, or before and after gas phase hydrogenation.