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CN-117567524-B - Method for preparing high-purity lactulose solution by utilizing sodium metaaluminate in continuous circulation mode

CN117567524BCN 117567524 BCN117567524 BCN 117567524BCN-117567524-B

Abstract

The invention discloses a method for continuously and circularly preparing a high-purity lactulose solution by utilizing sodium metaaluminate, belonging to the technical field of oligosaccharide preparation. The preparation method of the invention reduces the reaction temperature, improves the conversion rate and purity of the lactulose, adsorbs the lactulose clear liquid by using the food-grade active carbon, removes 96.0% of aluminum ions at the maximum, greatly reduces the cost of removing the aluminum ions, and circularly prepares sodium metaaluminate by calcining aluminum hydroxide precipitation, thereby reducing the catalyst consumption. The process optimization method provided by the invention is simple, convenient and feasible, meets the production requirements of resource conservation and environmental friendliness, and provides a beneficial reference and reference for promoting the industrial production of preparing lactulose by taking sodium metaaluminate/alkaline substances as alkaline complex catalysts.

Inventors

  • YANG RUIJIN
  • WANG ZIYIN
  • TONG YANJUN

Assignees

  • 江南大学

Dates

Publication Date
20260508
Application Date
20231023

Claims (8)

  1. 1. A process for the continuous cyclic preparation of high purity lactulose, comprising the steps of: (1) Dissolving lactose and sodium metaaluminate in water according to the concentration of 10-50% w/v and 5-10% w/v, regulating the pH of a system to 11.5-12.5, reacting for 1-2 hours at 50-70 ℃, adding water to dilute and cool after the reaction is finished, regulating the pH to 5.0-7.0, separating and washing to obtain a first lactulose clear solution and a first aluminum hydroxide precipitate; (2) Dissolving lactose in water according to the concentration of 10-50% w/v to obtain lactose solution, adding the first aluminum hydroxide precipitate obtained in the step (1) into the lactose solution, adding sodium metaaluminate to the lactose solution according to the concentration of 12-18% of the mass of sodium metaaluminate in the step (1), regulating the pH of a system to 11.8-12.4, reacting for 1-2 h at 50-70 ℃, adding water to dilute and cool after the reaction is finished, and regulating the pH to 5.0-7.0; (3) Adding active carbon into the second lactulose clear liquid obtained in the step (2) to dealuminate, separating and washing after dealuminating to obtain third lactulose clear liquid and active carbon for adsorbing aluminum; (4) Adding the sodium metaaluminate prepared in the step (3) into the step (1), and repeating the steps (1) - (3) to circularly prepare lactulose; The addition amount of the activated carbon in the step (3) is 0.1-5% w/v of the supernatant, and the activated carbon is dealuminated and adsorbed for 10-600 min.
  2. 2. The method according to claim 1, wherein the reaction in steps (1) and (2) is completed and then cooled to 20 to 30 ℃.
  3. 3. The method of claim 1, wherein the pH is adjusted in steps (1) and (2) using hydrochloric acid until the system no longer precipitates.
  4. 4. The method of claim 1, wherein sodium hydroxide is added to adjust the pH to 11.8-12.4 in steps (1) and (2).
  5. 5. The method according to claim 1, wherein the aluminum hydroxide precipitate is obtained by washing for 5 to 300 minutes in the steps (1) and (2).
  6. 6. The method of claim 1, wherein the activated carbon powder in step (3) is food grade powdered activated carbon.
  7. 7. The method according to claim 1, wherein an aqueous sodium hydroxide solution is added in step (3).
  8. 8. The method of claim 1, wherein in step (3) the aluminum hydroxide is calcined at 600-800 ℃.

Description

Method for preparing high-purity lactulose solution by utilizing sodium metaaluminate in continuous circulation mode Technical Field The invention relates to a method for preparing a high-purity lactulose solution by utilizing sodium metaaluminate in a continuous circulation way, belonging to the technical field of oligosaccharide preparation. Background Lactulose (beta-D-Galactopyranosyl- (1- & gt 4) -D-furctofuranose) is a non-digestible oligosaccharide with unique functional characteristics, can inhibit the growth of various pathogenic bacteria, and can promote the proliferation of beneficial intestinal bacteria, and has wide application in the fields of health foods and clinical medicines. The industrial preparation of lactulose mainly adopts a chemical method, and utilizes an alkaline catalyst to isomerise lactose to prepare the lactulose. The preparation method has strong thermodynamic equilibrium inhibition effect and product inhibition effect, and the lactulose generated under high temperature and strong alkaline environment can be further degraded, so that the final product has lower lactulose and content, contains a large amount of byproducts such as residual lactose, sugar acid, monosaccharide, pigment and the like, and has very difficult purification of high-purity lactulose due to the existence of a homogeneous alkaline catalyst, thereby severely restricting the further development of a chemical isomerization method in the industrial preparation of the lactulose. Owing to the stronger affinity of the complex catalyst and lactulose, the complex catalyst can be preferentially complexed with the lactulose generated by isomerization in a strong alkaline environment to generate anion complexes such as lactulose-boric acid, lactulose-aluminate, lactulose-organic germanium and the like, the inhibiting effect of the product lactulose is reduced, the isomerization reaction is promoted to continuously proceed towards the positive direction of generating the lactulose, and the formed lactulose complex can also play a role in avoiding the degradation of the lactulose in the strong alkaline environment. The lactulose complex can be dissociated by acidification treatment, and free lactulose and the complexing catalyst are released. The complex catalyst can greatly improve the isomerization reaction efficiency to 70-85%, the isomerization temperature is lower (60-70 ℃), the required reaction time is shorter, and the yield of lactulose is higher. A continuous circulation preparation method of high-purity lactulose solution is proposed by adopting sodium metaaluminate/alkaline substances as alkaline catalysts in China (such as China patent application No. 2016, 201611103063.5). The method comprises the steps of isomerizing lactose to form isomerized fructose syrup, respectively obtaining lactulose clear liquid and precipitate through acidity adjustment, dilution, dispersion, slag-liquid separation and other operations, obtaining high-concentration lactulose solution after desalting and removing monosaccharide from the lactulose clear liquid, directly converting the precipitate into meta-aluminate after alkali liquor treatment, and realizing recycling of catalyst. The invention has the following problems that the reaction of a circulating batch is not thorough, lactose residues in the mixed syrup after the reaction are more, the purity of the final syrup solution is lower (66 percent), the lactulose solution produced by the circulating batch is difficult to purify to prepare high-purity lactulose meeting the standard, the residual aluminum content in the clear liquid of the second round of circulating lactulose is increased by tens to twenty times compared with the first reaction, the residual aluminum content in the clear liquid of the third round of circulating lactulose is increased by thirty to fifty times compared with the first reaction, the consumption of the ion exchange dealuminated resin in the refining process of the lactulose is greatly increased, and the precipitate cannot be generated in the third round of isomerization, namely, the follow-up aluminum hydroxide is difficult to separate out by adjusting the pH along with the increase of the reaction times. The existing research on aluminum adsorption by the unmodified activated carbon is mainly focused on aluminum residue in the water purification process of a water plant, and no research on decoloring and simultaneously dealuminizing the activated carbon in the sugar manufacturing process exists in China. In the paper 'experimental study of adsorption and desorption of activated carbon on aluminum', a researcher adopts columnar activated carbon to adsorb polyaluminium chloride, 1g of activated carbon is added into 100mL of solution with the aluminum concentration of 0.3ppm, the solution is subjected to rotary oscillation at 20 ℃ for 12-120 h, the aluminum removal rate reaches 64.43% in 12h and 95.83% in 120h under the condition of pH10.5, the alumi