JP2686966B2 - Method for recovering unreacted sugar in powder form from sucrose fatty acid ester synthesis reaction mixture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

TECHNICAL FIELD The present invention relates to a method for industrially recovering unreacted sugar in a sucrose fatty acid ester synthesis reaction mixture by a solvent method in a powder state by separating it from a residual reaction solvent without using an organic solvent for purification.

[Prior art]

(Background) Currently, sucrose fatty acid ester (hereinafter also referred to as << SE >>) useful as a surfactant is industrially used as sucrose and C _{8 to} C _22.
With the higher fatty acid methyl ester of sucrose in a solvent (dimethylformamide, dimethylsulfoxide, etc.) under an appropriate catalyst (solvent method: JP-B-35-13102), or sucrose in the presence of water without a solvent. Is made into a solvent mixture with fatty acid soap and then reacted with higher fatty acid methyl ester in the presence of a catalyst (water medium method: JP-B-51-14485).
No.). However, according to either of these two synthetic methods, the reaction mixture contains unreacted sugar, in addition to the target SE.
It contains impurities such as unreacted fatty acid methyl ester, residual catalyst, soap, free fatty acids, and volatile matter.The impurities of which the content exceeds the specified amount must be removed before it becomes a product. No, but this requires a large amount of organic solvent. In particular, among the contaminants, the removal of residual solvent associated with the latter solvent method (volatiles) is only critical recently regulated ^Note) is have become stricter. Note) According to the US FDA standard, the residual amount of mesyl sulfoxide allowed in SE is 2ppm or less (Fed.Regist., 51
(214), 40160-1). Another important problem in industrial production of SE is the problem of recovering unreacted sugar. That is, as is well known,
The reaction rate of sucrose at the time of SE synthesis is low, and for example, even in the case of the dimethylformamide method, it does not reach 50% (Refer to Applicant Company 《Sugar Ester Story (1984)》 page 35), so there is no recovery of unreacted sucrose This industry is not established. Therefore, a large amount of organic solvent has been conventionally used for the dual purpose of removing residual reaction solvent from crude SE and recovering unreacted sugar.However, heavy use of such solvent is not suitable for industrial production of SE. , Brings the following significant disadvantages. 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 due to residual solvent remaining in product SE. The negative impact on employee health, and the rise in fixed costs associated with the increase in the number of shifts to prevent it. Under these circumstances, there has been a pressing need in the art to develop a technology that makes the use of an organic solvent unnecessary during SE purification and sugar recovery. (Problems of the prior art) Therefore, SE purification and sugar recovery methods that do not use organic solvents have been conventionally investigated. For example, (1) SE precipitation method 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 the method (1), for example, when an aqueous hydrochloric acid solution is added to the reaction mixture, the SE precipitates immediately, but unreacted sucrose easily decomposes and converts into glucose and fructose, for example, at a low temperature ( Decomposition cannot be avoided even when carried out at 0-5 ° C. This makes it difficult to recover and reuse unreacted sugar. As is well known, the reaction rate of sucrose during SE synthesis is low, for example, 50% even in the case of the dimethylformamide method.
(See "Sugar Ester Story (1984)", page 35) issued by the applicant company, this industry cannot operate without recovery of unreacted 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 is not decomposed, but the monoester, which is a useful component in SE, becomes a solvent on the aqueous phase side, which causes not only a large loss but also high HLB of which there is a large demand 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 solution 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, the light liquid layer (upper layer) contains a large amount of purified solvent, and therefore SE, fatty acid, unreacted fatty acid methyl ester, and other substances having a small polarity are dissolved in this light liquid layer. However, reaction solvents such as dimethyl sulfoxide dissolve in the lower heavy liquid layer, but unfortunately they also dissolve in the upper light liquid layer, so it is impossible to completely separate the reaction solvent by this method alone. Is. Moreover, not only a small amount of reaction solvent, but also a very large amount of purified solvent is necessary for the purpose of removing and collecting unreacted sugar. (Concept of the invention) Thus, in order to industrially enable purification of crude SE with water and recovery of unreacted sugar, the removal of the reaction solvent and the purified solvent is complete, and the sugar and product SE are not lost. The major premise is to develop a purification method that does not cause For the purification of reaction mixture based on this idea, SE for water is used.
It is inevitable that a large amount of unreacted sugar migrates to the water side because the difference in the degree of solvent between the unreacted sucrose and the unreacted sucrose is basically used. It cannot exist economically or socially. Therefore, it is an important subject of the invention how to effectively recover the sugar transferred to the water side during purification.

[Problems to be solved by the invention]

Therefore, the problem to be solved by the present invention is to industrially develop a means for removing a reaction solvent and recovering unreacted sugar in a reaction mixture without using a purification solvent. (Concept of the invention) Therefore, the present inventor not only (a) to suppress the amount of SE dissolved in the water phase side to the minimum, but to set the amount to zero if possible to precipitate the total amount of SE, (b) To avoid decomposition of unreacted sugar, (c) to separate from SE by dissolving the remaining reaction solvent outside the aqueous phase, and (d) to separate the precipitate on the filtrate (or supernatant) As a result of many salting-out experiments aimed at solving the three problems of efficiently recovering unreacted sugar, when sucrose and neutral salts were dissolved in an aqueous solution of the reaction mixture, an appropriate pH, Under the combination of temperature, concentration of neutral salt and sucrose, and water amount, not only almost all of SE is precipitated but also, surprisingly, the reaction solvent is dissolved in water other than unreacted sugar. I found a convenient phenomenon that leads to. Therefore, utilizing this phenomenon, the precipitated SE
Is dissolved in water again, and the precipitation operation with a neutral salt and an aqueous sucrose solution is repeated to effectively prevent the loss of SE, while completely removing the residual volatile components (remaining reaction solvent) in the aqueous phase. It is clear that the unreacted sugar in the SE reaction mixture can be efficiently recovered in a purified state by transferring the unreacted saccharide in the SE reaction mixture by contacting the residual liquid from which the precipitate is removed with an appropriate reverse osmosis membrane. (Summary) The present invention is based on the above findings, and its gist is, in addition to the target sucrose fatty acid ester, unreacted sugar, unreacted fatty acid methyl ester, catalyst, soap, fatty acid and volatilization. Adjust the pH of the sucrose fatty acid ester synthesis reaction mixture containing water to a neutral range, add water, neutral salt and sucrose, separate the precipitate, and then contact the residual liquid with a reverse osmosis membrane to make it impermeable. Characterized by spray drying Resides in a process for recovering unreacted sugars sucrose fatty acid ester synthesis reaction mixture as a powder. Hereinafter, various elements constituting the invention will be described. (Solvent method SE synthesis reaction mixture) In the synthesis of SE by the solvent method, a reaction solvent such as dimethylsulfoxide is usually added to a mixture of sucrose and fatty acid methyl ester in an amount several times as much as the total amount of these and dissolved. In the presence of an alkaline catalyst such as potassium carbonate (K ₂ CO ₃ ) under reduced pressure near 20 to 30 Torr for 80 hours
By holding at 90 ° C, the SE reaction mixture is easily formed with a reaction rate (based on fatty acid methyl ester) of 90% or more. Next, in order to eliminate the activity of the alkaline catalyst in the SE reaction mixture, an equivalent amount of an organic acid such as lactic acid or acetic acid or a mineral acid such as hydrochloric acid or sulfuric acid is added to the SE reaction composition. By this neutralization, the catalyst changes into a potassium salt such as potassium lactate depending on the type of acid used for the neutralization. Finally, the reaction solvent (for example, dimethyl sulfoxide) is distilled off under vacuum to give a composition (reaction mixture after neutralization and distillation) having the following composition range. SE = 15.0 to 92% Unreacted sugar = 1.0 to 80% Unreacted fatty acid methyl ester = 0.5 to 10% Neutral salt derived from potassium carbonate = 0.05 to 7% Soap = 1.0 to 10% Fatty acid = 0.5 to 10% Volatile (Residual reaction solvent) = 5.0 to 30% At this time, the ester distribution of SE is 10 to 75 monoesters.
% (90 to 25% for diester or higher). The fatty acid root mainly contained in each of the fatty acid methyl ester, soap and fatty acid is saturated, and C ₁₆
Has a common carbon number of ~ C ₂₂ . (Hydrolysis) Next, water is added to the above reaction mixture, and water: reaction mixture = 5: 1 to 40: 1 (weight ratio) (1). : Reaction mixture = 20: 1 (weight ratio) ... (2) In addition to the ratio of the formula, pH is 6.2 to 8.2, preferably pH
7.5. In this case, when the addition ratio of water is out of the above range, for example, when the amount ratio of water to the reaction mixture is less than 5,
The viscosity of the obtained aqueous solution becomes large, and subsequent operations become substantially difficult. Conversely, the ratio of water to the reaction mixture is
If an excess of water is added so as to exceed 40, the viscosity becomes small and the subsequent operation becomes easy, and the desired reaction solvent is preferably removed. When recovering water, a great deal of energy cost is required for removing water, and economic efficiency is lost. Furthermore, the pH of the aqueous solution is preferably adjusted to pH 6.2 to 8.2 in order to avoid the decomposition of the target SE. pH8.2
Under the above hydrogen ion concentration, the quantitative
There is a concern that SE will decompose, and even in a weakly acidic region of pH 6.2 or less, for example, exposure to a high temperature of 90 ° C or more may cause acid decomposition. (Salting out) The aqueous solution of the SE reaction mixture whose pH has been adjusted as described above is kept at 50 to 80 ° C as much as possible, and a neutral salt and sucrose are further added. In this case, the neutral salt to be added preferably first satisfies the following formula (3). Here, total salt amount = neutral salt amount to be added + salt amount formed from catalyst ... (4) Total sugar amount = sucrose to be added + unreacted saccharide amount from the beginning ... (5) The amount of sucrose to be added may be determined by the following formula (6). Further, in addition to both of the above formulas, it is preferable that the weight ratio of the total salt amount and the total sugar amount also satisfies the following formula (7). The present inventors heated an aqueous solution containing a precipitate of SE obtained by adding a neutral salt and sucrose so as to satisfy the above three formulas (3), (6) and (7) to 50 to 80 ° C. It was found that when the temperature was raised, even if the composition of the volatile matter (remaining reaction solvent) contained in the SE reaction mixture largely fluctuated to 5.0 to 30.0%, almost all SE was precipitated. . This phenomenon is a unique phenomenon and has an important value in relation to the object of the invention. The attached FIG. 1 is a ternary graph showing this phenomenon in more detail. In this figure, the weight of SE dissolved in the aqueous phase side = Y [g] The weight of precipitated SE = X [g] The total SE (X + Y) [g] dissolved in the aqueous phase side ing
If SE weight ratio = φ [%], φ is defined by the following equation (8). Here, the following conditions: temperature = 80 ° C., pH = 7.5, water: reaction mixture = 7.4: 1 (weight ratio) fatty acid residue = stearic acid composition of reaction mixture SE = 29% unreacted sugar = 35% unreacted Fatty acid methyl ester = 2% Catalyst-derived salt = 1% Soap = 3% Fatty acid = 1% Volatile content (remaining reaction solvent) = 29% Distribution of ester in SE: monoester = 73% Diester or higher = 27%, Triangular coordinates indicate how the value of φ changes. Here, the total salt is represented by the formula (4), and the total sugar is represented by the formula (5).
It is the amount defined by each, and is expressed as water amount + total salt amount + total sugar amount = 100%. The shaded area in FIG. 1 is a region that simultaneously satisfies the expressions (3), (6), and (7) discovered by the present inventors. By determining the amount of neutral salt and sucrose dissolved so as to fall within the shaded area, substantially φ = 0, that is, approximately the total amount of SE is precipitated, and at the same time, volatile matter ( The remaining reaction solvent), unreacted sucrose, the by-product salt from the catalyst and the added neutral salt can be dissolved and completely separated from the precipitated SE content. (Reverse Osmosis) Next, sucrose separated as an aqueous phase from the SE synthesis reaction mixture by the above steps, a by-product salt from the catalyst (K ₂ CO ₃ ), a neutral salt added for salting out and It is an important condition for achieving the object of the invention to selectively separate and recover only sucrose from a mixed aqueous solution containing four volatile components. However, the inventors have found that the use of the reverse osmosis method is particularly effective for this purpose. If you select a reverse osmosis membrane with a molecular weight cut-off in the range of 130 to 200, unreacted sugar (molecular weight 342) or SE that accidentally washed away to the filtrate side due to the salting-out treatment in the previous stage (molecular weight 600 or more)
Both are expected to be filtered out without problems. On the other hand, when the molecular weight cutoff of the membrane is less than 130-200, a by-product salt from the catalyst, for example, potassium lactate (molecular weight 128)
Alternatively, added neutral salts and volatiles, such as dimethyl sulfoxide (MW 78), will pass through the micropores of the reverse osmosis membrane without problems. As a result of many experiments based on this estimation, sucrose that had undergone the salting-out treatment in the previous stage, by-product salts from the catalyst, neutral salts and volatile components added during salting-out, and sometimes a small amount to a small amount of SE
Aqueous solution containing is at a temperature of 40-60 ° C and a molecular weight cutoff of 150-200.
When the reverse osmosis membranes in the vicinity are brought into contact with each other while being applied with a larger pressure as a driving source than during ultrafiltration, the by-produced salt from the catalyst, the added neutral salt and the volatile component are water. It was also found that they easily pass through the micropores of the reverse osmosis membrane. By this reverse osmosis operation, an impure sucrose aqueous solution (which may contain a small amount of SE in some cases) is produced from water, by-products from the catalyst, neutral salts added during salting out, and low molecular weight substances such as volatile matter. Separated and formed into a concentrated crude sugar solution. Then, the crude sugar aqueous solution obtained here is dissolved again in fresh water and subjected to the same reverse osmosis treatment again (or again) to obtain a sucrose aqueous solution having a 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, there will be concern about the heat resistance of the reverse osmosis membrane, and
Since the micelle structure of SE may change, it is advisable to treat at a temperature below 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. (Reverse Osmosis Membrane) Many industrial reverse osmosis membranes that have advanced in recent years are put on the market. Among these commercially available reverse osmosis membranes, crosslinked polyamide-based reverse osmosis membranes are examples of those having excellent durability, heat resistance, acid resistance, alkali resistance, bactericidal resistance and pressure resistance. This membrane is, for example, a reverse osmosis membrane sold by Toray Engineering Co., Ltd., trade name << SU-200 >> and the like has the above-mentioned molecular weight cutoff of about 200, which is well suited to the object of the present invention. In the case of a reverse osmosis membrane with a molecular weight cutoff of about 200, the solute concentration in the supplied aqueous solution is approximately 8 to 20% as the 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%, it becomes difficult for water, by-product salts and volatile components from the catalyst to pass through the fine pores of the reverse osmosis membrane, and the driving pressure must be increased accordingly. As a result, the film area must be wide, and
It is very uneconomical because it requires a lot of power.
On the other hand, if the solute concentration is about 8 to 15%, industrial separation of sucrose is sufficiently possible. For example, the following table-1
In the case of the aqueous solution having the composition of sucrose, the separation rate of sucrose is pH 7.5, the temperature is 50 ° C, and the driving pressure is 56.0 kg / cm ² G, the reverse osmosis membrane << SU-200 >> with an effective area of 8 m ² per unit. so , And similar results were obtained with similar films from other companies.
In all cases, a small amount of dissolved SE was recovered in good yield together with sucrose. In the above reverse osmosis treatment, by repeated reverse osmosis membrane treatment, the by-product salt from the catalyst, the added neutral salt and the volatile component of sucrose by-water solution in which the three components are sufficiently removed, is approximately 15 to 20%.
It is possible to keep the sugar concentration to some extent. It is technically difficult to obtain a sugar aqueous solution having a concentration of 20% or more, and the economic efficiency is reduced. (Spray drying) By the above reverse osmosis treatment, unreacted sucrose and sucrose added at the time of salting out can be recovered in the form of a substantially pure aqueous solution, and this sucrose solution is used for various purposes per se. Yes, but not for SE synthesis reaction. The reason for this is that it is known that the presence of a small amount of water adversely affects the transesterification reaction in the solvent synthesis process (LLOID OSIPOW et al.
al., Journal of the American Oil Chemistry Society [JAOCS, Vol. 34, p. 185), because anhydrous conditions of 0.05% or less are used as actual working conditions (above-mentioned p. 44). reference)). Therefore, even if a high-purity sucrose solution can be recovered, the recovery of sucrose is ultimately meaningless unless industrial dehydration and drying are successful. By the way, chemically pure sucrose melts at 188 ° C., but this melting point is significantly lowered by the presence of a small amount of impurities.
In addition, the concentrated aqueous sucrose solution becomes a viscous syrup and has the property of being caramelized by heating.Therefore, when the concentrated aqueous sucrose solution is vacuum dried using a conventional stirring solid vacuum dryer, the sugar concentration becomes high. As a result, it becomes difficult to dehydrate and dry, so that sucrose causes intense coloring and caramelization as a result of being forced to be treated at a high temperature for a long time. As another drying method, even when using a so-called flash type dryer that continuously heats the slurry and supplies and discharges it to the vacuum chamber, the large latent heat of water (500K
(more than cal / Kg / water), it is difficult to dehydrate and dry it. Even if these difficulties can be overcome, it is necessary to remove the sucrose after dehydration and drying under vacuum from the dryer, and then cool it by blowing cold air to a temperature below its melting point and then crush it. And The following is a summary of the series of steps for producing powdered sucrose: dehydration under vacuum, drying, removal of sucrose from a vacuum dryer, cooling and solidification of the extracted sucrose, and removal of solidified sucrose. Since multiple steps such as crushing are required, it is not economically desirable, and especially in the crushing step, there is a concern of dust explosion. However, as a result of research, the present inventor has found that a spray drying method is particularly suitable as an industrial dehydration / drying method that does not deteriorate the quality of sucrose from a sucrose solution obtained by reverse osmosis. That is, the aqueous sucrose solution is continuously supplied to the spray drying tower via a pump, and the aqueous sucrose solution supplied via a nozzle or a rotating disk, preferably the latter is dispersed and atomized to obtain an evaporation area of water. Can be made extremely large, so that dehydration and drying can be completed within a few seconds after spraying. The temperature of the aqueous sucrose solution supplied to the spray drying tower is usually
A temperature within the range of 40 ° C to 80 ° C is preferable. When dispersed by a rotating disk, when the diameter of the circle is 5-10 cmφ, 15,000
A suitable rotation speed is from rpm to 24,000 rpm. The air to be blown should have an amount of heat equal to or more than that required to evaporate the water content in the slurry, so when the air temperature is low, naturally,
A large amount of air is required. The air temperature can be selected between 10 ° C and 100 ° C, but it is desirable to select between 60 ° C and 80 ° C to avoid alteration of sucrose. The humidity in the blown air is also important together with the above air temperature, but in general, as absolute humidity, It is economical to choose the value of. The factors such as the volume, diameter and height of the spray drying tower are designed based on the above spraying conditions. If the conditions are suitable, powdery sucrose having a water content of 5% or less is continuously taken out from the lower part of the spray drying tower. As explained above, salting out, reverse osmosis and spray drying
By organically combining the steps, it becomes possible to industrially recover the unreacted sucrose in the SE reaction mixture.

[Action]

Unreacted sugar, unreacted fatty acid methyl ester, catalyst,
Add acid to the sucrose fatty acid ester forming reaction mixture containing soap, fatty acid and volatile matter (remaining reaction solvent) to adjust the pH to a neutral range, then add water, neutral salt and sucrose at an appropriate temperature. When salting out with, sucrose fatty acid ester, unreacted fatty acid methyl ester, soap and fatty acid precipitate, and volatile matter (remaining reaction solvent) moves to the water phase side, so no organic solvent is used. Residual volatiles can be removed. In particular, by operating so as to satisfy the conditions of formula (3), formula (6) and formula (7), it is possible to remove the residual solvent with substantially no loss of SE. Then, after subjecting the aqueous phase to reverse osmosis treatment, the residual liquid is spray-dried to selectively separate only the unreacted sucrose from the by-product salt from the catalyst, neutral salt for salting out and volatile matter. The sucrose of the reaction can be recovered in reusable powder form.

【Example】

Hereinafter, modes and effects of the invention will be described with reference to examples, but the examples are, of course, for the purpose of description, and are not intended to limit or limit the inventive idea. Example-1 Dry matter obtained by neutralizing the residual liquid obtained by distilling off the reaction solvent from the solvent method SE reaction mixture represented by the composition in Table 2 below with lactic acid and then drying.
1,000 kg of water was added to 100 kg and dissolved. Add 62.5 kg of sucrose and 9% of 50% potassium lactate to this aqueous solution.
7.6 kg was added, the temperature was raised to 75 ° C., the temperature was raised, the precipitated cake was filtered off, dried at 80 ° C. under vacuum, and the composition of the solid matter was examined. The water content in the cake was 45%. In addition, the SE amount in the filtrate separated by filtration from the cake was determined by gel filtration chromatography (GPC) method (described above, page 63).
The presence of SE was not observed at all, and 95% of the reaction solvent dimethyl sulfoxide was removed. Water was added to 1,180 kg of the filtrate thus obtained (an aqueous solution containing sucrose, salts and volatile components from which SE has been removed) to prepare a liquid having the composition shown in Table 4 below. This aqueous solution (pH7.4) is heated to 50 to 52.5 ° C, and the reverse osmosis membrane is used at a pump pressure of 58.2 Kg / cm ² G (<< Product name SU-200 >>, above).
(Diameter 4 inches x length 1 meter, filtration area 8 m ² ) was supplied under the following conditions. Discharge rate of the aqueous solution that permeates the membrane = 3.9 to 2.2 / min Circulation rate around the reverse osmosis membrane = 19.2 to 20.9 / min Supply time = 550 minutes The concentrate that did not permeate the membrane was initially included as sucrose. The amount of by-product salt from the catalyst
46.0% and volatile matter contained 52.0% of the initial amount, respectively. On the other hand, as shown in Table 5 below, the aqueous solution containing the by-product salt from the catalyst and the volatile components that have permeated the membrane contains almost no sugar, and the by-product salt from the catalyst and the added neutral salt are initially added. Of 54.0
%, And volatile matter contained 48.0% of the initial amount, respectively. Example-2 1,900 kg of water was newly added to 1,048 kg (concentration of solute of 12.5%) of the concentrated solution described in the previous Example-1 and Table-5, and the solution was supplied to the reverse osmosis membrane under the same conditions as in the above example. Separate sucrose and
Was obtained. Example-3 2,200 kg of water was newly added to 1,015.2 kg (solute concentration: 10.6%) of the concentrated solution described in Example-1 and Table-5, and the reverse osmosis membrane was supplied under the same conditions as in the same example. Sucrose was separated. The results are shown in Table 7 below. Example-4 1010.4 kg of the concentrated unreacted sugar aqueous solution (solute concentration about 10%) obtained in Example-3 above was supplied to a spray drying tower, and spray dried under the following conditions. Diameter of spray drying tower 2.0mφ Straight tube length: 1.5m Rotating disk diameter: 10 cmφ Rotation speed: 22,000 rpm Inlet air temperature: 80 ° C, Concentrated liquid supply rate: 1.7 kg / hour Drying can be continued stably, and sucrose obtained from the bottom of the spray-drying tower is a white powder that does not contain reducing substances such as glucose, 2.70% water, and bulk. The specific gravity was 0.41 and the fluidity was good. For reference, the analysis results of the obtained sucrose are shown in Table 8 below.

As described above, the present invention provides means for industrially removing a reaction solvent and industrially recovering unreacted sugars without using a purification solvent. The acquisition brings technological innovation to this industry.

[Brief description of the drawings]

FIG. 1 is a ternary graph showing the relationship between changes in the amounts of water, total sugar and total salt, and the amount of SE dissolved in the aqueous phase.

Claims (17)

(57) [Claims] 1. In addition to the desired sucrose fatty acid ester, unreacted sugar unreacted fatty acid methyl ester, catalyst, soap,
The sucrose fatty acid ester synthesis reaction mixture containing fatty acids and volatiles was adjusted to pH in the neutral range, water, neutral salt and sucrose were added, the precipitate was separated, and the residual liquid was contacted with the reverse osmosis membrane. A method for recovering unreacted sugar in the form of powder in a sucrose fatty acid ester synthesis reaction mixture, which comprises spray-drying the impermeable portion. 2. The method according to claim 1, wherein the reaction mixture is adjusted in the range of pH 6.2 to 8.2. 3. The method according to claim 1, wherein the pH-adjusted reaction mixture is heated to 50 to 80 ° C. 4. The method according to claim 1, wherein water is added to the reaction mixture after pH adjustment in a weight ratio of water: reaction mixture = 5: 1 to 40: 1. 5. The method according to claim 1, wherein the pH-adjusted reaction mixture is added with a neutral salt and sucrose according to the following relational expression. Here, total salt amount = neutral salt amount to be added + salt amount produced by neutralization of catalyst Total sugar amount = sucrose amount to be added + unreacted sugar amount from the beginning 6. The method according to claim 1 or 2, wherein the acid used for adjusting the pH of the reaction mixture is one selected from the group consisting of lactic acid, acetic acid, hydrochloric acid and sulfuric acid. 7. The composition of the reaction mixture is as follows: sucrose fatty acid ester = 15.0 to 92.0% unreacted sucrose = 1.0 to 80.0% unreacted fatty acid methyl ester 0.5 to 10.0% catalyst = 0.05 to 7.0% soap = 1.0 to The method according to claim 1, wherein 10.0% fatty acid = 0.5 to 10.0% volatile matter (remaining reaction solvent) = 5.0 to 30.0%. 8. The method according to claim 1 or 2, wherein the fatty acid roots mainly contained in each of the fatty acid methyl ester, soap and fatty acid in the reaction mixture have a common saturated fatty acid root having 16 to 22 carbon atoms. 9. The method according to claim 1, wherein the volatile matter (remaining reaction solvent) in the reaction mixture is dimethyl sulfoxide or dimethylformamide. 10. The method according to claim 1, wherein the neutral salt added to the reaction mixture is any salt selected from the group consisting of common salt, sodium sulfate, potassium lactate and potassium acetate. 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 reverse osmosis is performed within a temperature range of 40 to 60 ° C. 13. The method according to claim 1, wherein the pH of the feed liquid to the reverse osmosis membrane is 6.2 to 8.2. 14. The method according to claim 1, wherein the reverse osmosis membrane is made of crosslinked polyamide plastics. 15. The sucrose concentration of the feed solution to the reverse osmosis membrane is 20%.
The method according to claim 1 or 13, wherein: 16. The method according to claim 1, wherein the sucrose concentration of the reverse osmosis membrane impermeable part is 20% or less. 17. Humidity and temperature during spray drying are respectively The method according to claim 1, wherein the temperature is 10 to 100 ° C.