JPH0337910B2 - - Google Patents

Description

[Detailed description of the invention]

A. Field of Industrial Application of the Invention The present invention relates to a method for selectively recovering esters, known as aromatic components, from gas generated from an alcohol fermentation process. Taking Japanese sake as an example, the gases generated during the fermentation process include, in addition to ethanol, aldehydes, ethyl acetate, fusel oil (mainly composed of isoamyl alcohol, isobutyl alcohol, etc.), isobutyl acetate, isoamyl acetate, ethyl caproate, Contains ethyl caprylate and ethyl caprate. Among these, the ones called ginjoko are isoamyl acetate, ethyl caproate, ethyl caprylate,
It is an ester with a fruity aroma such as ethyl caprate. These esters are desired as flavoring or natural flavoring agents for Japanese sake, while aldehydes and fusel oils are undesirable ingredients. In the method of the present invention, only the desired aroma components (esters) can be selectively recovered, and when returned to alcoholic beverages, it helps to improve the quality of alcoholic beverages, and it is also possible to sell them as natural flavorings. BACKGROUND ART Conventional fermentation gas recovery methods are mainly aimed at recovering ethanol vaporized from a fermentation tank, and known methods include the cooling trap method and the adsorption method using activated carbon fibers. In the cooling trap method, fermentation gas is guided into a cooler,
This method involves cooling the gas to around -25°C to liquefy the ethanol, fusel oil, and esters contained in the gas and returning it to the fermentation tank. This method was originally widely used to prevent loss of ethanol. In this method, components such as acetaldehyde and fusel oil that are undesirable and useless as a flavor for alcoholic beverages are also recovered at the same time. The adsorption method using activated carbon fibers is a method in which fermentation gas is guided to activated carbon fibers, alcohol and aroma components contained in the gas are collected, and the collected components are desorbed and recovered with water vapor. This is currently being developed as an energy-saving alcohol recovery method, and also for the selective recovery of aroma components. This method is described in the literature [Brewing Association Journal Vol. 81, No. 3]
No., pp. 185-188 (1986)] According to the data, although it is an excellent method for recovering alcohol, fusel oil remains on the recovery liquid side, making it unsatisfactory in terms of selective recovery of aroma components. Problems to be Solved by the Invention An object of the present invention is to provide a method for selectively and efficiently recovering only esters, which are known as aromatic components, from gas generated from an alcohol fermentation process. (b) Means for Solving the Constituent Problems of the Invention The method of recovering esters from fermentation gas according to the present invention is based on dealuminated SiO ₂ , in which a column is filled with the liquid recovered by liquefying the fermentation gas generated in the alcohol fermentation process. /Al ₂ O ₃ is passed through an adsorbent made of Y-type zeolite or activated carbon with a molar ratio of 10 or more to adsorb esters on the adsorbent, and then the fermentation gas is liquefied and recovered. Ethanol is added in the opposite direction to the supply direction of the recovered liquid. It is characterized by eluating the adsorbed matter from the adsorbent by circulating an aqueous solution. As an adsorbent, dealuminated
It is preferable to use Y-type zeolite or activated carbon with a SiO ₂ /Al ₂ O ₃ molar ratio of 10 or more. Dealumination treated Y-type zeolite
The reason why the SiO ₂ /Al ₂ O ₃ molar ratio is set to 10 or more is because if it is less than this, the amount of adsorption becomes very small and is not practical. In general, increasing the SiO ₂ /Al ₂ O ₃ molar ratio of zeolite makes it hydrophobic, and the more hydrophobic the compound, the stronger the adsorption power to these zeolites, so hydrophobicity is a factor. There is no doubt about it. However, even if the SiO ₂ /Al ₂ O ₃ molar ratio is high, mordenite and ferrierite show almost no adsorption ability, so hydrophobicity alone cannot explain this. The dealuminated Y-type zeolite is H
It may be an ion exchange type or a zeolite exchanged with metal ions. When considering adding the recovered components to foods, the metal ion-exchanged zeolite is preferably one ion-exchanged with a harmless alkali metal or alkaline earth metal such as Na, K, Mg, or Ca. As the activated carbon used as the adsorbent, those that are generally commercially available for adsorption can be used. The esters selectively adsorbed on the zeolite and activated carbon are easily eluted with an ethanol aqueous solution, but the esters can be efficiently eluted by flowing the ethanol aqueous solution in the opposite direction to the direction in which the fermentation gas is liquefied and recovered. is concentrated. The ethanol aqueous solution used to elute the adsorbate is
It is preferable to use an aqueous solution containing 30 vol% or more of ethanol. If the concentration of ethanol is lower than 30vol%,
The solubility of esters is low, and the amount of ethanol aqueous solution used for elution increases. In particular, recovery of esters with large molecular weights becomes difficult. In order to recover esters more effectively,
It is desirable to use an ethanol aqueous solution that contains 30 vol% or more of ethanol and has a higher concentration of ethanol than the ethanol concentration of the liquid obtained by liquefying and recovering the fermentation gas. The higher the ethanol concentration in the elution solution, the easier it is to recover esters, but if it exceeds 60 vol%, it will be treated as a dangerous substance and will be subject to legal restrictions, so it is convenient to use an ethanol aqueous solution with less than 60 vol%. be. The fermentation gas may be any gas containing aromatic components generated during the fermentation process, including sake,
Examples include fermentation gases obtained in the production of wine, beer, soy sauce, etc. In the present invention, esters known as aroma components are recovered from the liquid obtained by liquefying and recovering this fermentation gas. The liquefied recovery liquid of the fermentation gas may be obtained by cooling and liquefying the fermentation gas. Furthermore, according to the present invention, esters can be successfully recovered even in a low-concentration liquid such as a liquid recovered by passing fermentation gas through activated carbon fibers and desorbing the adsorbed components with steam. can. The adsorption device used is a packed column type. When there is only one packed column, the esters are recovered by performing an elution operation after the adsorption is completed. Continuous operation is possible by providing a plurality of packed columns, performing adsorption operation in one or more columns, performing elution operation in the other one or more columns, and performing switching operations at appropriate times. The elution operation does not necessarily need to be performed until 100% of the esters are recovered, and may be performed as appropriate depending on the desired concentration of the esters. The adsorption conditions may be room temperature and normal pressure. Although the adsorbed esters may be eluted with an aqueous ethanol solution at room temperature, the elution time can be shortened by increasing the temperature. In this case, the heating temperature is preferably about 60° C. or lower from the viewpoint of saving energy consumption. The esters recovered by the method of the present invention may be returned to the fermenter as an ethanol solution, or the esters may be separated and recovered from the ethanol solution by a conventional method such as distillation. Example 1 [Using dealuminated Y-type zeolite,
Reverse regeneration using 59 vol% ethanol aqueous solution] A model solution prepared by adding 150 ppm i-aluminum alcohol, 75 ppm isoamyl acetate, 65 ppm ethyl caproate, and 70 ppm ethyl caprylate to a 25 vol% ethanol aqueous solution was mixed with dealuminated Y-type zeolite (SiO ₂ / Al ₂ O ₃ molar ratio = 14; particle size 0.5-1
mm) was fed into a column packed with 5 c.c. Each 50 c.c. of the effluent was collected and quantified by gas chromatography. When isoamyl acetate began to flow out, the supply of the raw material was stopped, and then a 59 vol% ethanol aqueous solution was supplied in the opposite direction to that during adsorption to recover the adsorbed ester. At this time, as in the case of adsorption, 50 c.c. of the effluent was collected and quantified by gas chromatography. The results are shown in Table 1. As shown in the table, esters could be recovered at high concentrations. Furthermore, the recovery rate of each ester was approximately 100% at the time when 100 c.c. of the effluent was collected, and the amount of ester adsorbed per adsorbent was 20.7 mg/cc of adsorbent. Example 2 [Using dealuminated Y-type zeolite,
Reverse regeneration using 40 vol% ethanol aqueous solution] Adsorption and regeneration were performed in the same manner as in Example 1, except that a 40 vol% ethanol aqueous solution was used for regeneration. The results are shown in Table 1. The difference from Example 1 is that the amount of regenerated liquid was increased because the ethanol concentration of the regenerated liquid was lowered, and the concentration of recovered ester was decreased. The recovery rate of esters was 300 c.c.
The amount of ester adsorbed per adsorbent was not much different from that of Example 1. Example 3 [Using dealuminated Y-type zeolite,
Reverse regeneration using 30 vol% ethanol aqueous solution] Adsorption and regeneration were performed in the same manner as in Example 1, except that a 30 vol% ethanol aqueous solution was used for the regeneration. The results are shown in Table 1. The difference from Examples 1 and 2 is that the amount of regenerated liquid was further increased because the ethanol concentration of the regenerated liquid was low, and the concentration of recovered ester was decreased. The recovery rate of esters was 100% when 500 c.c. of the effluent was collected, and the ester adsorption rate was not significantly different from that in Example 1. Example 4 [Using dealuminated Y-type zeolite,
Reverse regeneration using 59 vol% ethanol aqueous solution] Adsorption and adsorption were carried out in the same manner as in Example 1, except that 5 c.c. of dealuminated Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 30) was used as the adsorbent. I played it. The results are shown in Table 1. There was almost no difference except that the ester adsorption amount was 25 mg/cc of adsorbent, which was a slightly better result than the zeolite of Example 1. Example 5 [Using activated carbon, reverse regeneration with 59 vol% ethanol aqueous solution] Activated carbon (manufactured by Nimura Chemical: SGP) 5 as an adsorbent
Adsorption and regeneration were carried out in the same manner as in Example 1 except that cc was used. The results are shown in Table 1. Compared to the zeolite of Example 1, the ester recovery rate is the same (the ester recovery rate is almost 100% when 100 c.c. of the effluent is collected), but the amount of ester adsorbed per adsorbent is The amount of activated carbon was rather small at 8.7 mg/cc, and a small amount of isoamyl alcohol coexisted. Comparative Example 1 [Using dealuminated Y-type zeolite,
Forward regeneration using 40 vol% ethanol aqueous solution] Testing was carried out in the same manner as in Example 1, except that a 40 vol% ethanol aqueous solution was used for regeneration and flowed in the same manner as during adsorption. The results are shown in Table 1. In this case, ethyl caprylate could not be recovered, and the concentration of ethyl caproate was also quite low. Comparative Example 2 [Using activated carbon, forward regeneration with 40 vol% ethanol aqueous solution] A test was conducted in the same manner as in Example 1, except that a 40 vol% ethanol aqueous solution was used for regeneration and flowed in the same direction as during adsorption. As in Comparative Example 1, ethyl caprylate could not be recovered and the first fraction did not contain ethyl caproate. Comparative Example 3 [Using dealuminated Y-type zeolite,
Reverse regeneration using 20 vol% ethanol aqueous solution] Adsorption and regeneration were performed in the same manner as in Example 1, except that dealuminated Y-type zeolite was used as the adsorbent and regeneration was performed in the reverse direction using a 20 vol% ethanol aqueous solution. . The results are shown in Table 1. Even when regenerating in the reverse direction, if the ethanol concentration is low, a large amount of regenerating solution is required, and only a low concentration of recovered ester can be obtained. Comparative Example 4 [Using dealuminated Y-type zeolite,
Reverse regeneration using 59 vol% ethanol aqueous solution] Adsorption and adsorption were carried out in the same manner as in Example 1, except that 5 c.c. of dealuminated Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 6) was used as the adsorbent. I played it. Isoamyl acetate is already released in the first 50 c.c.
It showed almost no ester adsorption ability.

【table】

[Table] Figure 1 (Example 2) and Figure 2 (Comparative Example 1)
An example of regeneration in the reverse and forward directions using a 40 vol% ethanol aqueous solution is shown. The horizontal axis of the figure shows the outflow amount (cc) of recycled ethanol, and the vertical axis shows the relative concentration of ester (C/C ₀ ). Here, C is the ester concentration in the regenerated liquid, C ₀ is the ester concentration in the raw material, 〇 is isoamyl acetate, △
represents ethyl caproate, and ◇ represents ethyl caprylate. When regenerating in the reverse direction as shown in Figure 1, esters can be regenerated with a high concentration and a small amount of ethanol. On the other hand, during the forward regeneration shown in FIG. 2, ethyl caprylate cannot be regenerated. C. Effects of the invention Useful esters can be selectively recovered from a liquid obtained by liquefying and recovering fermentation gas. Since an aqueous ethanol solution is used to elute the esters from the adsorbent, the recovered esters are harmless and non-toxic even when added to drinks, foods, etc. Adsorption operations can be performed at room temperature, and elution operations do not need to be carried out at high temperatures, so energy savings are expected.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing examples of regeneration in the reverse and forward directions using a 40 vol% ethanol aqueous solution.

Claims (1)

[Scope of Claims] 1. Adsorption made of Y-type generalite or activated carbon with a dealuminated SiO ₂ /Al ₂ O ₃ molar ratio of 10 or more, in which a column is filled with a liquid obtained by liquefying and recovering fermentation gas generated in the alcohol fermentation process. The method is characterized in that the adsorbent is eluted from the adsorbent by passing an ethanol aqueous solution in the opposite direction to the supply direction of the liquid obtained by liquefying and recovering the fermentation gas. A method for recovering esters from fermentation gas. 2 The ethanol aqueous solution used to elute the adsorbate is
The method for recovering esters from fermentation gas according to claim 1 or 2, which is an aqueous solution containing 30 vol% or more of ethanol.