JP2721891B2 - Method for recovering unreacted sugar from reaction mixture containing sucrose fatty acid ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a process for purifying sucrose fatty acid esters useful as surfactants, from a reaction mixture containing sucrose fatty acid esters, on an industrial scale, to unreacted sugars and salts and by-products produced by neutralization of the catalyst by-products. And a method for removing the three.

[Prior art]

(Background) Currently, sucrose fatty acid esters (hereinafter also abbreviated as “SE”) useful as surfactants are commercially available from sucrose and C ₈ -C
Either react with ₂₂ higher fatty acid methyl ester in a solvent (dimethylformamide, dimethylsulfoxide, etc.) under an appropriate catalyst (solvent method: Japanese Patent Publication No. 35-13102) or use sucrose with water without solvent. After forming a melt mixture with fatty acid soap, it is reacted with higher fatty acid methyl ester in the presence of a catalyst (water-based method: Japanese Patent Publication No. 51-14485).
Has been obtained by However, in any of these two synthetic methods, the desired SE is contained in the reaction mixture.
In addition, it contains unreacted sugars, unreacted fatty acid methyl esters, residual catalysts (in the case of the solvent method), soaps, free fatty acids, volatiles, and other impurities, and the content of these impurities is regulated. Excess amounts of impurities must be removed before the product is formed. In particular, among the above contaminants, the removal of the residual solvent has recently become strictly regulated, and the removal and recovery of unreacted sugar is of the utmost importance because of its large amount. (Problems of the prior art) By the way, as a means for removing unreacted sugar from the reaction mixture of SE, a solvent is added to the reaction mixture by utilizing that a normal solvent has little ability to dissolve sucrose. In addition,
Conventionally, a method of removing contaminating unreacted sugar as a precipitate has been generally used. However, aside from the small scale, in factories engaged in the production of SE on an industrial scale, the inconvenience of handling solvents, such as troublesome solvent recovery, fire danger, and occupational health problems for workers, is noticeable. There is something extra. However, since there is no other effective means, the solvent is still used for removing unreacted sugar, which means, for example, in Japanese Patent Publication Nos. 42-11568 and 48-10448, butyl alcohol, toluene, methyl ethyl ketone. And solvents such as ethyl acetate are specified to be effective for purification, including removal of unreacted sugar. Now, for reference, the disadvantages associated with the handling of solvents are listed as follows. Explosion, fire hazard. Explosion-proof electrical equipment provided above. Sealing of the production equipment provided above. The fire-resistant structure of the whole building prepared above. Above, due to rising fixed costs. Cost increase due to solvent wear. Negative effect of residual solvent remaining in product SE. Adverse effects on employees' health, and consequently increase the number of units and the cost. Therefore, a purification method that does not use an organic solvent has been conventionally studied. For example, typical methods include (1) a method of precipitating SE using an acidic aqueous solution (UK Patent 809,81).
5 (1959)) (2) Precipitation method of SE with general neutral salt aqueous solution
−8850). However, as in method (1), for example, when an aqueous solution of hydrochloric acid is added to the reaction mixture, SE is immediately precipitated, but unreacted sucrose is easily decomposed and converted into glucose and fructose. (0-5 ° C.), decomposition cannot be avoided. This makes it difficult to recover and reuse unreacted sugar. As is well known, the reaction rate of sucrose during the synthesis of SE is low. For example, even in the case of the dimethylformamide method, the reaction rate does not reach 50% (see “Sugar Ester Story (1984)”, p. 35, issued by the applicant company). The industry is not feasible without the recovery of reactive sucrose. Also, as in method (2), SE is immediately precipitated even when an aqueous solution of a neutral salt such as salt or sodium sulfate is added to the reaction mixture. In this case, the unreacted sugar does not decompose, but the monoester, which is a useful component in the SE, is dissolved in the aqueous phase, causing not only a large loss but also high HLB, which is particularly popular in recent years. It is an obstacle when you want to get SE. According to a more recent Japanese Patent Application Laid-Open No. Sho 51-29417, a mixed solvent of water and a "purified solvent" (which is particularly called to distinguish it from the reaction solvent) is composed of a light liquid layer (upper layer) and a heavy liquid layer (lower layer). The property of phase separation is used. That is, generally a heavy liquid layer (lower layer)
Contains a large amount of water, and hydrophilic unreacted sugar, catalyst-derived salts, and the like are dissolved in the heavy liquid layer (lower layer).
On the other hand, since the light liquid layer (upper layer) contains a large amount of purified solvent, small polar substances such as SE, fatty acids and unreacted fatty acid methyl esters are dissolved in this light liquid layer. However, reaction solvents such as dimethyl sulfoxide also dissolve in the lower heavy liquid layer, but unfortunately also dissolve in the upper light liquid layer, so it is impossible to completely separate the reaction solvent by this method alone. It is. In addition, a very large amount of a purified solvent is required for removing unreacted sugars as well as a trace amount of a reaction solvent. (Principle of the Invention) As described above, in order to industrially enable the purification of mixed SE using water, a purification method that completely removes the reaction solvent and the purification solvent and that does not cause loss of sugar and product SE is required. Development is a major premise. An important issue that still needs to be considered is the means of recovering unreacted sugar associated with using water as the purification solvent. In purifying the reaction mixture based on this philosophy, it is essential to utilize the difference in solubility between SE and unreacted sucrose in water, so an enormous amount of unreacted sugar migrates to the water side. Without this recovery of dissolved sugars, the industry cannot be established economically or socially. Therefore, it is an important proposition of the invention how to effectively recover the sugar transferred to the water side during purification.

[Problems to be solved by the invention]

Under such circumstances, development of a technique capable of removing unreacted sugar and other impurities from an impure SE reaction mixture without a solvent, that is, without using a solvent other than water, has long been desired. Therefore, the problem to be solved by the present invention is to use not only a solvent but also unreacted sugar in an impure SE reaction mixture, residual catalyst, salts by-produced from the catalyst, volatile matter (solvent for reaction). To establish a technique for simultaneously removing other contaminants.

[Means for solving the problems]

(Summary) In order to solve the above problems, the method for recovering unreacted sugar from a reaction mixture containing a sucrose fatty acid ester according to the present invention comprises, in addition to the target sugar fatty acid ester, unreacted sucrose and unreacted sucrose. The method is characterized in that a mixed reaction mixture containing fatty acid methyl ester, catalyst, soap, fatty acid, volatile matter and the like in the reaction is brought into contact with an ultrafiltration membrane and a reverse osmosis membrane. Hereinafter, various elements constituting the invention will be described separately. (Ultrafiltration) It is known that SEs combine with each other under a certain condition in an aqueous solution to form an aggregate having a high molecular weight micelle structure (refer to the above-mentioned “Shogar Ester Story”, p. 102). It is a fact. By the way, in any of the oxygen atoms of three primary hydroxyl groups of sucrose in SE, respectively one to three monoester C ₈ -C ₂₂ fatty acid residue is bound to, diesters and type of such triesters There is. As is well known, monoesters have relatively low hydrophilicity compared to diesters and triesters, but have a small degree of micelle formation in water. Form. Conversely, diesters and triesters have an extremely large micelle-forming ability instead of relatively low hydrophilicity, and therefore form an SE micelle aggregate having an extremely large molecular weight (that is, a large molecular diameter) in water. Commercially available SEs are rarely manufactured as monoesters alone, and usually have a monoester content of, for example, 70%, 50%, 30%
・ It is manufactured as a mixed composition. The present inventors have conducted repeated studies aiming at solving the above-mentioned problems, and as a result, for example, SE having a monoester content as high as 70%
Produces a SE aggregate having a lower molecular weight than SE having a monoester content as low as 50%, and accordingly, the microscopic diameter of the aggregate is small, and therefore, ultrafiltration having a constant pore size It is easier to pass through the membrane than SE with a monoester content of 50%, so unreacted sugars and by-product salts from the catalyst (formed when the catalyst is neutralized with an acid), volatiles, etc. Have an undesired tendency to easily pass through the membrane together. Therefore, the present inventors, as a countermeasure against this, when it is desired to remove unreacted saccharides, salts derived from the catalyst, volatile matter, etc. from the impurity SE having a high monoester content, the fraction molecular weight is small (that is, the pore size is small). ) Selection of a filtration membrane, and conversely SE with low monoester content
In this case, it has been found that it is convenient to select a filtration membrane having a large molecular weight cut-off (that is, a large pore size) in order to increase the processing speed. Incidentally, the present inventors, among the substances contained in the reaction mixture, the unreacted fatty acid methyl ester, soap and fatty acid, the three are present in a state encapsulated in the micelle structure aggregate of SE, It was also confirmed from many experimental results that it was virtually impossible to separate SE and the three of them by filtration means. Thus, from many experiments, the inductive conclusion is that the impurities that can pass through the filtration membrane (with the appropriate molecular weight cut-off) with water, driven by pressure, are unreacted sugars, catalyst-derived salts, volatiles (Dimethylsulfoxide, dimethylformamide, and other substances used as solvents in the synthesis of SE, which are strongly polar, have high water solubility, and have high affinity for sucrose)
On the other hand, substances that are incorporated into the high molecular weight micelle aggregate and cannot pass through the filtration membrane include SE, unreacted fatty acid methyl ester, soap and free fatty acid. The ultrafiltration step in the present invention takes advantage of these facts and, by selecting an ultrafiltration membrane having an appropriate molecular weight cutoff, reduces the unreacted sugar, catalyst-derived salts and volatile components. It is intended to separate and remove SE, unreacted fatty acid methyl ester, soap and fatty acid. (Molecular weight of substance to be filtered) In order to select an ultrafiltration membrane having an appropriate molecular weight cut off, it is necessary to know the approximate molecular weight of the substance to be filtered.
The molecular weights of these single substances relevant to the invention are as follows: ○ Sucrose = 342 ○ Unreacted fatty acid methyl ester Stearic acid methyl ester = 290 ○ Salt generated by neutralization of catalyst (K ₂ CO ₃ ) When using lactic acid → potassium lactate = 128 When using acetic acid → potassium acetate = 98 ○ Volatile dimethyl sulfoxide = 78 Dimethylformamide = 73 ○ SE (as a monomer that does not form micellar aggregates) Sucrose monostearate = 600 Sucrose distearate = 858 Sucrose tristearate = 1116 Palmitate, araquinate,
There is no significant difference in the molecular weight of other fatty acid esters such as behenate. ○ Soap Sodium stearate = 298 Potassium stearate = 314 ○ Fatty acid stearic acid = 276 ○ Water = 18 By the way, the apparent molecular weight of the SE micelle structure aggregate (hereinafter referred to as the “molecular weight of SE micelle aggregate”) The following can be experimentally assumed. Since SE in an actual aqueous solution forms a micelle aggregate in water, for example, when the number of micelle associations of SE is 10, the molecular weight of the micelle aggregate is 100% monoester, Assuming that the molecular weight of the ester monomer (600) x 10 = 6,000 diester 100%, ◇ The molecular weight of the diester monomer (850) x 10 = 8,580 Assuming 100% of the triester, ◇ The molecular weight of the triester (1,116) x 10 = 11,160 Since the SE in the experiment is a mixture of a monoester, a diester and a triester, the average molecular weight of the micelle aggregate of SE may be defined as the molecular weight. (Molecular Weight of Fractionation of Filtration Membrane) Selection of a membrane suitable for the purpose of the invention is performed as follows. First, in an ultrafiltration membrane with a molecular weight cut off of 200, the reaction mixture in the form of an aqueous solution is supplied to the membrane while applying pressure to remove unreacted sugar and salts and volatiles generated from the catalyst (K ₂ CO ₃ ). In the filtration membrane, only water having a molecular weight lower than the molecular weight cut off of the filtration membrane of 200, salts and volatiles generated from the catalyst (K ₂ CO ₃ ) can be separated. Since sucrose having a molecular weight of 342 larger than the cut-off molecular weight of 200 does not pass through the filtration membrane, unreacted sugar cannot be separated and removed from SE. Next, in the case of a filtration membrane having a molecular weight cut-off of 5,000, sucrose, salts and volatile components from the catalyst have a molecular weight of 5,000, respectively.
Because they are smaller, they can easily pass through the micropores of the filtration membrane. SE
Constitutes a micelle aggregate as described above, and assuming that the number of micelle associations is, for example, 10, the molecular weight of the SE micelle aggregate is estimated to be 6,000 or more. Therefore, when the molecular weight cut off of the filtration membrane is larger than 5,000, it is presumed that the micelle aggregate cannot pass through the micropores, but this estimation has been experimentally confirmed. Further, the case of a filtration membrane having a molecular weight cut off of 1,000 was also examined, but the results were as expected. Thus, by appropriately selecting the molecular weight cutoff of the ultrafiltration membrane,
It is possible to remove impurities including unreacted sugar in the SE reaction mixture. (Conditions to be provided for the filtration membrane) The unreacted sugar contained in the SE reaction mixture, the salt by-produced from the catalyst (K ₂ CO ₃ ), and the volatile components are SE, soap, and unreacted fatty acid methyl. In the case of separating the ester and fatty acid from each other, the condition that the filtration membrane should have is that the membrane has resistance to a physical external force when the membrane has an appropriate molecular weight cutoff. It has heat resistance and is not decomposed by microorganisms. It has an appropriate molecular weight cut-off and high processing capacity. Long service life. Affordable pricing is available. And so on. In recent years, there have been remarkable technological advances in the production of ultrafiltration membranes, so that commercially available products satisfying the above conditions are found. (Ultrafiltration conditions) The preferred composition of the SE reaction mixture for performing the ultrafiltration step of the present invention is SE 15% to 90%, unreacted sugar 2% to 80%,
0.5% to 10% unreacted fatty acid methyl ester, the catalyst (K ₂ CO ₃₎
0.05% ~ 7%, soap 2% ~ 60%, fatty acid 0.5% ~ 10%,
The volatile content is 0.0% to 50%. In removing the unreacted sugar and the salt (K ₂ CO ₃ ) history of salts and volatiles (dimethylsulfoxide and dimethylformamide) from these reaction mixtures, the fatty acid methyl ester has a carbon number of C _{8 to} C ₂₂ . It does not matter whether it is saturated or unsaturated. Potassium carbonate (K ₂ CO ₃ ) is used as a catalyst for SE synthesis.
However, catalysts used in general alcoholysis reactions, such as sodium carbonate and sodium alkoxide, can also be used. The types of the soap and the fatty acid may correspond to the above-mentioned fatty acid methyl ester. Volatile components are dimethyl sulfoxide and dimethylformamide used as a solvent during SE synthesis in the previous step. In carrying out this step, the above-mentioned SE reaction mixture is desirably mixed with deionized water such that water: reaction mixture = 5: 1 to 40: 1 (weight ratio), more preferably water: reaction mixture = 20: 1 (weight ratio). Since SE is susceptible to hydrolysis in an alkaline under order to prevent its hydrolysis, prior to addition of water and neutralized by adding an acid to the catalyst (K ₂ CO _3), the pH of the solution from 6.2 to 8.2, preferably Is preferably adjusted to around pH 7.5. At this time, as the acid used for neutralization, an organic acid such as lactic acid and acetic acid and an inorganic acid such as hydrochloric acid and sulfuric acid are used. If the pH of the neutralized solution exceeds 8.2, the decomposition of SE proceeds, and if the pH is lower than 6.2, it is difficult to form micelle aggregates of SE, so that the SE flows out of the system during filtration and causes loss. The temperature of the aqueous solution at the time of filtration is preferably 80 ° C. or lower irrespective of the type of the fatty acid methyl ester, and if it exceeds the temperature, there is a concern that SE will decompose. The inventors have found that a maximum filtration rate is obtained, especially when the temperature is in the temperature range of 40-60 ° C. That is, the filtration temperature is 40-60
By adjusting the temperature to about 50 ° C, optimally about 50 ° C, the unreacted sugar, salts and volatiles (dimethylsulfoxide and dimethylformamide) from the catalyst (K ₂ CO ₃ ) It passes through the filtration membrane most efficiently with water. The reason for this is that, at 40 to 60 ° C., the size of the micelle aggregates of SE becomes large as a result, the total number of micelle aggregates decreases, and substances that do not participate in the formation of micelle aggregates, such as unreacted sugar, originally. This is presumed to be due to the fact that the resistance of SE is less likely to be received, and unreacted sugars and the like easily pass therethrough. As is known, aqueous SE solutions generally exhibit a maximum viscosity between 40 and 60 ° C. (p. 103, supra), indicating that the micellic assembly may have the highest molecular weight within the temperature range. This suggests, and this fact can also explain why unreacted sugars and the like show the maximum passage speed in the range of 40 to 60 ° C. Thus, the reaction mixture aqueous solution containing SE maintained at 40 to 60 ° C. was pressurized to ¹ to 20 kg / cm ² G by a pump to apply pressure as a driving source, and a hydrogen ion concentration region of pH 6.2 to 8.2 was applied. Contact with ultrafiltration membrane. Here as a filtration membrane,
Cellulose-based materials are not only physically weak, but also easily susceptible to microorganisms, and are therefore less desirable in practical use. Practically suitable are polysulfone or polyvinylidene fluoride membranes reinforced with a support layer. Both types of filtration membranes are currently on the market, and are heat resistant, acid resistant,
It has excellent alkali resistance, strong physical external force, and no microorganisms grow on the membrane surface. As described above, when determining the molecular weight cutoff of the filtration membrane,
Separation of unreacted sugars etc. is performed efficiently without leakage of SE,
It is important to select a material having a high filtration rate. As a result of the examination, the inventors found that there was no leakage of SE,
In addition, the separation molecular weight of the membrane that satisfies the desired condition that the unreacted sugar, by-product salts and volatiles are not impaired and that the filtration rate is high is preferably in the range of 1,000 to 100,000. It has been found that a filtration membrane having a molecular weight cut-off of 5,000 is most preferable as it has no SE leakage and is suitable for processing on an industrial scale. 5,000
Excessive molecular weight cut-offs will result in a small but leaky SE, whereas membranes with a molecular weight cut-off of less than 5,000 will have reduced filtration rates. However, in each case, it does not bring disadvantages beyond industrial profitability. Among the commercially available filtration membranes, those suitable for the purpose of the invention include, for example, trade names << TERP-E-5 >> (polyvinylidene fluoride type) among marginal filtration membranes sold by Toray Engineering Co., Ltd. << TERP-HF-10 >> (polysulfone type)
And << TERP-HF-100 >> (polysulfone-based). According to the filtration membrane << TERP-HF-10 >> (ultrafiltration membrane having a molecular weight cut off of 10,000), an aqueous solution of the SE reaction mixture (pH = 7.
5), even when the composition in the aqueous solution is as shown in Table 1 below, the temperature is 50
The separation rate of unreacted saccharide when the driving temperature was increased to 5.0 kg / cm ² G at 50 ° C. reached 4.7 kg saccharide / hour with a limit filtration membrane (per unit) having an effective area of 8 m ² . This is an industrially sufficient separation speed. In addition, the rate of separation of salts and volatiles by-produced from the catalyst was sufficient. Table 1 (Composition of reaction mixture and its aqueous solution) sucrose fatty acid ester (stearate) 42.0 kg unreacted sucrose 47.0 catalyst (K ₂ CO ₃ ) 0.5 unreacted fatty acid methyl (stearate) 1.5 soap (potassium stearate) 3.0 Fatty acid (stearic acid) 1.0 Volatile matter (dimethyl sulfoxide) 5.0 Subtotal 100.0 kg Water 2,000.0.0 kg Aqueous solution 2,100.0 kg Thus, the use of ultrafiltration membranes makes it easy to industrially convert unreacted sugars from SE reaction mixtures By-product salts and volatile components from the catalyst (K ₂ CO ₃ ) can be removed together with water, so that unreacted sugar and catalyst can be removed using only water and no solvent at all. The purpose of removing by-product salts and volatiles from (K ₂ CO ₃ ) is achieved. (Reverse osmosis) By performing the above ultrafiltration, from the SE synthesis reaction mixture, unreacted fatty acid methyl ester, soap and fatty acid encapsulated in the micellar structure of the target SE and unreacted fatty acid methyl ester An aqueous solution containing the sucrose of the reaction, by-product salts from the catalyst (K ₂ CO ₃ ) and volatiles is obtained. Therefore, from this mixed aqueous solution, only sucrose is selectively separated non-solvently.
Recovery is an important condition for achieving the object of the invention. However, as a result of research, the inventors have found that the use of the reverse osmosis method is particularly effective for this purpose. If the molecular weight cut-off of the reverse osmosis membrane is selected from the range of 130 to 200, unreacted sugar (molecular weight 342) or SE that has run off to the filtrate side due to ultrafiltration treatment at the front of every corner (molecular weight 600 or more) ) Cannot pass through the pores of the membrane, and are presumed to be filtered. In contrast, by-product salts from lower molecular weight catalysts, such as potassium lactate (molecular weight 128) and volatiles, such as dimethyl sulfoxide (molecular weight 78), pass through the micropores of the reverse osmosis membrane without problems. Would. As a result of many experiments based on the above estimation, the aqueous solution containing sucrose, by-product salts and volatiles from the catalyst, and sometimes a small amount to a small amount of SE, which had undergone the ultrafiltration treatment at the previous stage, had a temperature of 40 to 40. At 60 ° C., when contacted with a reverse osmosis membrane having a molecular weight cutoff of about 150 to 200 while applying a pressure higher than that during ultrafiltration as a driving source, water, by-product salts from the catalyst and volatile components They found that they easily passed through the micropores of the reverse osmosis membrane together with the water. By this reverse osmosis operation, an impure aqueous sucrose solution (including a small amount of SE in some cases) is separated from water, low-molecular-weight substances such as by-product salts from the catalyst and volatile components, and the concentrated crude aqueous sucrose solution is formed. Becomes Then, the obtained aqueous solution of crude sugar is dissolved in fresh water again and subjected to the same reverse osmosis treatment again (or repeatedly) to obtain an aqueous solution of sucrose with higher purity. In the above, the temperature of the aqueous solution to be supplied to the reverse osmosis membrane is important for expecting good results, and if the temperature is reduced to 40 ° C. or less, the processing capacity is significantly reduced. It is better to choose a temperature of 40 ° C or higher. However
If the temperature exceeds 60 ° C., the heat resistance of the reverse osmosis membrane and the micelle structure of SE may change. Therefore, it is prudent to treat at a temperature lower than the upper limit temperature. In addition, the pH of the aqueous solution is also important in practice, and the pH in the range of 6.2 to 8.2 is preferable because the possibility of affecting the quality of sucrose is small. Many industrial reverse osmosis membranes that have advanced in recent years have been put on the market by various companies. Among these commercially available membranes, there are polyether-based reverse osmosis membranes as examples of those having excellent durability, heat resistance, acid resistance, alkali resistance, bacteria resistance and pressure resistance. This membrane is, for example, a reverse osmosis membrane sold by Toray Engineering Co., Ltd., trade name << SU-200 >>, etc., having a value in the vicinity of the above-mentioned molecular weight cutoff of 200, and is well suited for the purpose of the present invention. Generally, in the case of a reverse osmosis membrane having a molecular weight cutoff of around 200, the solute concentration in the supplied aqueous solution is 8 to 20% as an upper limit,
Desirably, by controlling the upper limit of the solute concentration to about 8 to 15%, industrial processing capacity can be exhibited. If the solute concentration exceeds 15%, water, by-product salts and volatiles from the catalyst will not easily pass through the micropores of the reverse osmosis membrane, and the driving pressure must be increased accordingly. As a result, the membrane area must be widened, and
It is very uneconomical because it requires large power.
On the other hand, if the solute concentration is about 8 to 15%, industrial separation of sucrose is sufficiently possible. For example, Table 2 below
In the case of an aqueous solution having the following composition, the reverse osmosis membrane << SU-200 >> having an effective area of 8 m ² per unit at a pH of 7.5, a temperature of 50 ° C., and a driving pressure of 56.0 kg / cm ² G so , And similar results were obtained with similar films from other companies.
In each case, the dissolved SE was recovered together with sucrose in good yield. In the above reverse osmosis treatment, the sucrose-containing aqueous solution from which by-product salts and volatile components have been sufficiently removed from the catalyst by the repeated reverse osmosis membrane treatment can have a sugar concentration of about 15 to 20%. . It is technically difficult to obtain a sugar aqueous solution having a concentration of 20% or more, and the economic efficiency is reduced. Therefore, if a sugar concentration higher than the above sugar concentration is desired, it can be concentrated to a desired concentration, for example, 50% or more, using a usual concentration device, for example, a multiple vacuum effect can. Then, the recovered sucrose is used again for SE synthesis raw materials and other uses.

[Action]

SE in an aqueous solution forms an aggregate having a micellar structure in which many SE molecules are united under certain conditions. Therefore, by forcibly passing through an ultrafiltration membrane having micropores having a pore size that does not allow the aggregate to pass through, the unreacted sugar in the SE reaction mixture, the permeable fraction consisting of catalyst-derived salts and volatiles and , SE, soap, unreacted fatty acid methyl esters and fatty acids. Then, the unreacted sugar can be recovered in a purified state by bringing the upper permeable fraction into contact with a reverse osmosis membrane having an appropriate molecular weight cutoff.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to examples. However, each example is, of course, for explanation, and is not directly related to the technical scope of the invention. Example 1 To a mixture of stearic acid methyl ester: sucrose = 1: 2 (molar ratio) was added potassium carbonate at 3.0% by weight based on solids.
Dimethyl sulfoxide is 4 times the weight of solids (weight ratio)
Was added, and the mixture was sufficiently dehydrated and reacted under a vacuum of 30 Torr for 7 hours while stirring vigorously in the reactor. Then, the composition of 95 kg of the reaction mixture obtained by distilling off most of dimethyl sulfoxide under vacuum was as shown in Table 3 below. After neutralizing the above reaction mixture to pH 7.5 with acetic acid,
1,360 kg of deionized water was added to the neutralized solution, and the mixture was stirred and dissolved at 50 ° C. for 60 minutes to obtain an aqueous solution having a pH of 7.3. The aqueous solution above, Toray Engineering Co. ultrafiltration membrane "TERP-E-5" following conditions to spiral 4 "cylindrical pressure filter unit of membrane area 8m ² that device (fractionation molecular weight of 5,000) Temperature = 53.0 ° C to 53.5 ° C, pressure = 6.0 kg / cm ² G to 7.2 kg / cm ² G Seven hours after the passage, the dissolved sucrose in the filtrate discharged from the filtration membrane was measured by a Lovibond refractometer. As a result, 90.1% of the unreacted sugar initially contained in the reaction mixture was eluted in the filtrate. Was. In contrast, the leakage of SE was only 0.2% based on the amount initially contained in the reaction mixture. When the amount of dimethyl sulfoxide, which is a volatile component, was measured by gas chromatography, 91.2% of the amount initially contained in the reaction mixture was removed from the filtrate. Further, 93.2% of the amount initially contained in the reaction mixture of potassium acetate by-produced from the catalyst was removed. Water was added to the above ultrafiltrate (an unreacted sugar, by-product salt from the catalyst, volatiles and other mixed aqueous solution from which SE was separated by filtration) to prepare a liquid having a composition shown in Table 4 below. This aqueous solution (pH 7.3) is heated to 53 ° C., and pump pressure 56 kg /
In cm ² , the solution was supplied to a reverse osmosis unit (4 ″ φ × 1 m, effective filtration area 8 m ² ) equipped with the reverse osmosis membrane << SE-200 >> under the following conditions: Discharge rate of aqueous solution permeating through the membrane = 4.9 to 2.0 l / min Circulation speed around the reverse osmosis membrane = 16.3 to 18.5 l / min Feeding time = about 158 minutes The resulting concentrated liquid (impermeable part) is 99.5% of the unreacted sugar originally contained, It contained 40.2% of by-product salt from the catalyst and 39.5% of volatile matter.On the other hand, the liquid that passed through the membrane contained almost no sugar, and
It contained 59.7% by-product salts from the catalyst and 60.3% volatiles, respectively. The results are summarized in Table-5 below. Example 2 245.3 kg of the concentrated solution described in Table 5 in the previous example (solute concentration 15.0
%) And 190 kg of water, and under the same conditions as
It was supplied to a reverse osmosis membrane to separate sucrose, and the results in Table 6 below were obtained. Example-3 The above example, 208.5 kg of the concentrate described in Table 6 (solute concentration 15.0 kg)
%), Add 380 kg of water, and under the same conditions as in the same example,
The solution was supplied to the reverse osmosis membrane to separate unreacted sugar. The results are shown in the table below.
7

【The invention's effect】

As described above, the present invention provides the industry with the ability to industrially remove a reaction solvent and provide a means for recovering unreacted sugar in a reaction mixture without using a purification solvent. Bring technological innovation.

Claims (14)

(57) [Claims] 1. A crude reaction mixture containing unreacted sucrose, unreacted fatty acid methyl ester, catalyst, soap, fatty acid, volatile matter, etc., in addition to sucrose fatty acid ester, is treated with an ultrafiltration membrane and a reverse osmosis membrane. A method for recovering unreacted sugar from a reaction mixture containing a sucrose fatty acid ester, which is contacted. 2. The method according to claim 1, wherein the ultrafiltration membrane comprises a polysulfone or polyvinylidene fluoride resin. 3. The molecular weight cut off of the ultrafiltration membrane is 1,000-100,000.
The method according to claim 1 or 2, wherein 4. The method according to claim 1, wherein the pH of the reaction mixture is 6.2 to 8.2.
The described method. 5. The temperature of the aqueous reaction mixture of the mixture is 40-60.
The method of claim 1, wherein the temperature is ° C. 6. The method according to claim 1, wherein the pressure as a driving source is 1.0 to 20.0 kg / cmG. 7. The method according to claim 1, wherein the weight ratio of water to the reaction mixture added to the reaction mixture is 5: 1 to 40: 1.
The described method. 8. The composition of the reaction mixture containing sucrose fatty acid ester is as follows: sucrose fatty acid ester = 15-95% unreacted sugar = 1-80% unreacted fatty acid methyl ester = 0.5-10% catalyst (as K2C03) The method according to claim 1, wherein 0.05-7% soap = 1-60% fatty acid = 0.5-10% volatile matter = 5-30%. 9. The fatty acid residue mainly contained in each of the fatty acid methyl ester, soap and fatty acid in the reaction mixture has a carbon number within the range of C8 to C22, and all three correspond to each other. The method according to claim 1 or 8, wherein the method has a common fatty acid residue. 10. The process according to claim 1, wherein the fraction of the reaction mixture is water, dimethylsulfoxide or dimethylformamide. 11. The method according to claim 1, wherein the molecular weight cut off of the reverse osmosis membrane is 150 to 200. 12. The method according to claim 1, wherein the temperature of the liquid to be treated supplied to the reverse osmosis membrane is 40 to 60 ° C. 13. The pH of a liquid to be treated supplied to a reverse osmosis membrane is as follows:
13. A method according to claim 1 or claim 12, wherein the neutral region is 6.2-82. 14. The method according to claim 1, wherein the reverse osmosis membrane is made of polyether plastics.