JPH0364495B2 - - 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 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 if returned to alcoholic beverages, it will help improve the aroma, and it can also be sold as a natural flavoring agent. BACKGROUND TECHNOLOGY Conventional fermentation gas recovery methods are mainly aimed at recovering ethanol vaporized from a fermentation tank, and known methods include a cooling trap method and an 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 that are undesirable or useless for the aroma of alcoholic beverages, such as acetaldehyde and fusel oil, are also recovered at the same time, and the concentration of aromatic components (esters) is about 2000 ppm at the highest. 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 adsorbed, and the adsorbed components are desorbed and recovered with water vapor. One of the methods is energy saving. This is currently being developed as a method for recovering alcohol, 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 alcohol recovery method, fusel oil remains in the recovery liquid, 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 structural problems of the invention The method of recovering esters from fermentation gas according to the present invention is based on a method for recovering esters from fermentation gas using a group consisting of Y-type zeolite and pentasil-type high-silica zeolite, which are treated with dealumination of gas generated from an alcohol fermentation process. The method is characterized in that the adsorbed components are desorbed after being brought into contact with an adsorbent selected from the following. The dealuminated Y-type zeolite or pentasil-type high-silica zeolite may be a H ion exchange type or a metal ion exchanged zeolite. Considering that the recovered components can be used as fragrances, metal ion exchange zeolite is
Those ion-exchanged with harmless alkali metals or alkaline earth metals such as Na, K, Mg, and Ca are preferable. Dealumination treated Y-type zeolite
The SiO ₂ /Al ₂ O ₃ molar ratio is preferably 10 or more.
This does not mean that there is no selectivity below this level;
This is because the amount of adsorption becomes extremely small. As a pentasil type high silica zeolite,
ZSM-5 is a typical example, and its SiO ₂ /
The Al ₂ O ₃ molar ratio is preferably 50 or more. 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, high silica mordenite, dealuminated mordenite, and ferrierite show almost no adsorption ability, so hydrophobicity alone cannot explain this. The gas generated from the alcohol fermentation process may be any gas containing aroma components generated during the fermentation process, including fermentation gases obtained in the production of sake, wine, beer, soy sauce, and the like.
Such fermentation gas is brought into contact with the zeolites in a gaseous state. Adsorption conditions may be room temperature and normal pressure. The adsorption device may be either a batch type or a packed column type. However, in terms of economy, the packed column type is advantageous. The esters selectively adsorbed on the zeolites can be easily desorbed and recovered by treatment with an organic solvent such as ethanol in a liquid or gas state, or by treatment with water vapor or the like. When desorbing esters using ethanol, the ethanol concentration is preferably 30 vol% or more, and 50 vol.
% or more is more preferable. The higher the ethanol concentration, the easier it is to recover esters, but if it exceeds 60 vol%, it is treated as a dangerous substance and is subject to legal restrictions, so it is convenient to keep it below 60 vol%. Desorption of esters using a liquid solvent may be performed at room temperature, but the desorption time can be shortened by increasing the temperature. In this case, the heating temperature is preferably about 60° C. or less from the viewpoint of saving energy consumption. Example 1 A stainless steel column with an inner diameter of 10 mm was filled with 2 g of Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 14), which was sized to a size of 30 to 60 mesh and treated with dealuminization using high-temperature steam. Model 1 fermentation gas (ethanol 15vol%, ethyl acetate 60ppm, isoamyl alcohol 140ppm, isoamyl acetate 40ppm
and a model aqueous solution of 30 ppm ethyl caproate.
CO ₂ is blown into the solution to bring out the dissolved components).
It was supplied at a linear velocity of 6 cm/sec. The gas after treatment was analyzed by gas chromatography, and the gas supply was stopped when isoamyl acetate began to flow out, and then a 59 vol% ethanol aqueous solution was flowed in the opposite direction to that during adsorption to desorb the adsorbed material. Recovered. 50 c.c. of the recovered liquid was collected, and the composition of each outflow was analyzed by gas chromatography. Table 1 shows the adsorption amount of each component (the first 100
The amount of each component contained in cc) is shown.

[Table] It can be seen that among the components of the model aqueous solution, isoamyl acetate and ethyl caproate are selectively adsorbed and recovered. In addition, almost the same results were obtained when the adsorbed material was desorbed and recovered by flowing a 59 vol% ethanol aqueous solution in the same direction as during adsorption. FIG. 1 shows the breakthrough curve during adsorption, where the horizontal axis represents the adsorption time (Hr) and the vertical axis represents the relative concentration (outlet/inlet). From Figure 1, ethanol (EtOH) and ethyl acetate (EtOAc) break through immediately, followed by isoamyl alcohol (i-AmOH) and isoamyl acetate (i-AmOH).
-AmOAc) is found to flow out in this order. In addition
Ethyl caproate did not flow out even after 20 hours. That is, it can be seen that isoamyl acetate and caproic acid ether can be selectively adsorbed by stopping the gas supply when ethanol, ethyl acetate, and isoamyl alcohol break through and isoamyl acetate begins to flow out. Example 2 As a pentasil type high silica zeolite
The model fermentation gas was adsorbed and desorbed and recovered using 59 vol% ethanol in the same manner as in Example 1 except that ZSM-5 (SiO ₂ /Al ₂ O ₃ molar ratio = 70) was used. The results are shown in Table 1. Isoamyl acetate and ethyl caproate could be selectively adsorbed and recovered. Almost the same results were obtained when the adsorbed material was desorbed and recovered by flowing a 59 vol% ethanol aqueous solution in the same direction as during adsorption. Example 3 Adsorption and desorption/recovery using 59 vol% ethanol were carried out in the same manner as in Example 1, except that dealuminated Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 120) was used as the adsorbent. Summer. Results first
Shown in the table. Isoamyl acetate and ethyl caproate could be selectively adsorbed and recovered. Almost the same results were obtained when the adsorbed material was desorbed and recovered by flowing a 59 vol% ethanol aqueous solution in the same direction as during adsorption. Example 4 A model fermentation gas was adsorbed in the same manner as in Example 1 using dealuminated Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 14) as an adsorbent.
For desorption, 50 vol% ethanol was used and the adsorbed material was recovered by flowing in the opposite direction to that during adsorption. The results are shown in Table 1. Isoamyl acetate and ethyl caproate could be selectively adsorbed and recovered. In addition, almost the same results were obtained when the adsorbed material was desorbed and recovered by flowing a 50 vol% ethanol aqueous solution in the same direction as during adsorption. Example 5 A model fermentation gas was adsorbed in the same manner as in Example 1 using dealuminated Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 14) as an adsorbent. For regeneration, 30 vol% ethanol was used and the adsorbed material was recovered by flowing in the opposite direction to that during adsorption. The results are shown in Table 1. In this case as well, isoamyl acetate and ethyl caproate can be selectively adsorbed and recovered, but due to their low solubility, the amount of ester contained in the recovered solution (100 c.c.) is small, and a large amount of ethanol is required for complete recovery. Therefore, it can be said that it is desirable to use higher concentration ethanol. Comparative Example 1 Adsorption and desorption were carried out in the same manner as in Example 1 except that activated carbon (SGP, manufactured by Nimura Chemical Co., Ltd.) was used as the adsorbent. The results are shown in Table 1. In the case of activated carbon, the adsorption of isoamyl alcohol was stronger than that of isoamyl acetate, and even when isoamyl acetate broke through, no isoamyl alcohol leaked out. That is, it was not possible to selectively concentrate and recover esters. Comparative Example 2 Adsorption was carried out in the same manner as in Example 1, except that Y-type zeolite (SiO ₂ /Al ₂ O ₃ molar ratio = 4.8), which was not subjected to dealumination treatment, was used as the adsorbent. All the components broke through over 1 hour after the start of supply. Therefore, the ester could not be recovered.

[Brief explanation of drawings]

FIG. 1 shows the breakthrough curve during adsorption in Example 1, where the horizontal axis represents the adsorption time (Hr) and the vertical axis represents the relative concentration (outlet/inlet).

Claims (1)

[Claims] 1. From a fermentation gas characterized in that the gas generated from the alcohol fermentation process is brought into contact with an adsorbent selected from the group consisting of dealuminated Y-type zeolite and pentasil-type high-silica zeolite, and then the adsorbed components are desorbed. Method for recovering esters.