A process for separating sugar and acid using an eight-zone simulated moving bed

Abstract

The present invention discloses a process for separating sugar and acid using an eight-zone simulated moving bed. The eight-zone simulated moving bed system is composed of 16 chromatographic columns filled with H-type cation exchange resins, and every two columns form a zone with a total of eight zones, specifically separation zones (Zones II, III, VI, and VII), stationary phase regeneration zones (Zones I and V), and eluent regeneration zones (Zones IV and VIII). The mobile phase direction of the entire system is opposite to the column switching direction, and the flow rate is controlled by three inlets and three outlets to achieve continuous separation of three components (sulfuric acid, monosaccharides, and organic acids). The technical solution of the present invention can achieve a recovery rate of sulfuric acid and xylose higher than 98%, a mass purity of xylose and sulfuric acid higher than 99%, and a solvent consumption of only 0.09 mL of deionized water per 1 g of xylose produced.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and particularly relates to a process for separating sugar and acid by utilizing an eight-zone simulated moving bed. Background Art

[0002] As the most abundant sustainable resource on earth, lignocellulosic biomass can be used as a raw material to produce biofuels (such as bioethanol) and a series of bioproducts. However, due to the stable structure of lignocellulose, the process of hydrolyzing it into fermentable sugars such as oligosaccharides and monosaccharides becomes particularly difficult. After long-term exploration, dilute acid hydrolysis and dilute acid pretreatment under high temperature and high pressure conditions have been widely used in a large number of research and actual production due to their high efficiency and low cost. However, the disadvantage of this method is that the treated hydrolyzate contains a variety of toxic substances generated by degradation reactions, and the content is relatively high. These toxic substances will seriously inhibit the growth and metabolic process of fermenting microorganisms in the subsequent fermentation process, thereby reducing the yield and production of bioproducts such as bioethanol. Therefore, before fermentation, the hydrolyzate needs to be subjected to sugar purification treatment, which includes two parts: detoxification and sugar-acid separation. Relevant literature shows that suitable sugar-acid separation technology is very critical.

[0003] To date, a large number of literature has reported on sugar-acid separation technologies, including electrodialysis, ion exchange chromatography, acid retardation, extraction, and ion exclusion chromatography. Each of these technologies has its own advantages and disadvantages. For example, electrodialysis can avoid sulfuric acid dilution, but it is energy-intensive and results in significant sugar loss. Acid retardation can effectively separate sugars and acids, but it suffers from acid tailing, resulting in high eluent consumption and low recovered sulfuric acid concentration. While the extraction process maintains sulfuric acid concentration, residual organic solvents remain in the treated hydrolyzate. Ion exclusion chromatography is the most widely studied technology due to its low operating costs and environmental friendliness, but it also suffers from over-dilution of the recycled sulfuric acid. Given that recycled sulfuric acid concentration is a significant factor affecting the cost of sugar-acid separation and is often overlooked in the literature, it is imperative to develop a sugar-acid separation process that can separate sulfuric acid, organic acid, and monosaccharides while ensuring sugar purity and production efficiency, while also ensuring that the recovered sulfuric acid is not overly diluted. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a process for separating sugars and acids using an eight-zone simulated moving bed, so as to achieve continuous separation of the three components of inorganic acid, organic acid and monosaccharide while ensuring high purity and yield, and ensuring that the inorganic acid is not excessively diluted.

[0005] Invention Concept: Current ion exclusion chromatography technology is only used for the separation of two components: inorganic acid and monosaccharide. The present invention utilizes the characteristics of inorganic acid as a strong electrolyte, organic acid as a weak electrolyte, and monosaccharide as a non-electrolyte. By screening H-type cation exchange resins with different degrees of cross-linking, a filler that can achieve near-baseline separation of the three components of inorganic acid, organic acid, and monosaccharide is obtained. At the same time, the current three-component separation process cannot avoid the problem of excessive dilution of inorganic acid. The present invention, through the eight-zone SMB process, can achieve continuous separation of the three components of inorganic acid, organic acid, and monosaccharide while ensuring the purity and production efficiency of the sugar, and at the same time ensure that the recovered inorganic acid is not excessively diluted.

[0006] In order to solve the above technical problems, the present invention discloses a process for separating sugars and acids using an eight-zone simulated moving bed, in which a mixed liquid containing inorganic acid, sugar and organic acid is subjected to adsorption treatment using a simulated moving bed system to achieve separation of inorganic acid, sugar and organic acid.

[0007] The simulated moving bed process of the present invention realizes continuous separation and purification of the three components by continuously inputting a mixed solution containing inorganic acid, sugar and organic acid and an eluent and collecting the three components separately at the same time.

[0008] The simulated mobile phase of the present invention is formed by connecting n chromatographic columns filled with H-type cation exchange resin in series into a ring, where n is greater than or equal to 8, such as 16, and every 1 to 4 columns, such as 2 columns, form a zone, and the eight zones are composed of four separation zones (zones II, III, VI, and VII), two stationary phase regeneration zones (zones I and V), and two elution regeneration zones (zones IV and VIII). At the same time, the outlet of zone V is connected to the inlet of zone III inside the system.

[0009] The eight zones are, in sequence, stationary phase regeneration zone I, separation zone II, separation zone III, eluent regeneration zone IV, stationary phase regeneration zone V, separation zone VI, separation zone VII, and eluent regeneration zone VIII; the mixed liquid flows in a clockwise direction; a feed port is provided at the inlet of zone VII, a first eluent inlet is provided at the inlet of zone I, a second eluent inlet is provided at the inlet of zone V, a first outlet is provided at the outlet of zone VII, a second outlet is provided at the outlet of zone I, and a third outlet is provided at the outlet of zone III; the outlet of zone VI is connected to the inlet of zone III; the effluent from the outlet of zone V is transported to the inlet of zone III; and the chromatographic column is switched in a counterclockwise direction.

[0010] Here’s how it works:

[0011] First, a mixture containing inorganic acid, monosaccharide, and organic acid enters the inlet of Zone VII. The inorganic acid is then separated from the other two components (monosaccharide and organic acid) by Zones VI and VII. Simultaneously, the monosaccharide and organic acid mixture is directly transported to the inlet of Zone III through internal process piping. The monosaccharide and organic acid are then separated by Zones II and III, achieving the separation and purification of the three components.

[0012] The composition of the solutions at the inlet and outlet of each zone of the simulated moving bed process for separating sugar and acid is as follows:

[0013] Zone VII: The inlet solution contains inorganic acid, monosaccharide and organic acid (from the raw material solution and the outflow of Zone VI), and the outlet solution contains only inorganic acid (the separation and purification of inorganic acid is completed). In addition, the inorganic acid component also comes from the column switching in Zone VIII, thus reducing the dilution of inorganic acid;

[0014] Zone VIII: The inlet solution has the same composition as the outlet solution of Zone VII and contains only inorganic acid. The outlet solution is eluent-water (solvent regeneration is completed);

[0015] Zone I: The inlet solution and the outlet solution of Zone VIII have the same composition of eluent-water. The outlet solution contains only organic acid components (which come from the chromatographic column switched in Zone II), which completes the separation and purification of organic acids.

[0016] Zone II: The inlet solution has the same composition as the outlet solution of Zone I and contains only organic acid components, while the outlet solution contains organic acid and monosaccharide components (which are retained by the chromatographic column switched in Zone III);

[0017] Zone III: The inlet solution contains two components: organic acid and monosaccharide (outflow from zones V and II), and the outlet solution contains only monosaccharide components (separation and purification of monosaccharides are completed);

[0018] Zone IV: The inlet solution has the same composition as the outlet solution of Zone III and contains only monosaccharide components. The outlet solution is eluent-water (solvent regeneration is completed);

[0019] Zone V: The inlet solution has the same composition as the outlet solution of zone IV, which is the eluent. The outlet solution contains two components: organic acid and monosaccharide (derived from the chromatographic column retained by the switching of zone VI);

[0020] Zone VI: The inlet solution has the same composition as the outlet solution of zone V and contains two components: organic acid and monosaccharide. The outlet solution contains inorganic acid, organic acid and monosaccharide (which comes from the chromatographic column retained by the switching of zone VII).

[0021] In some embodiments, the inorganic acid includes sulfuric acid; in some embodiments, the concentration of the inorganic acid in the mixed solution is 5 to 70 g / L, preferably 10 to 60 g / L, and preferably 15 to 50 g / L.

[0022] In some embodiments, the organic acid includes formic acid and / or acetic acid; in some embodiments, the concentration of the organic acid in the mixed solution is 1 to 40 g / L, preferably 2 to 30 g / L, and preferably 3 to 20 g / L.

[0023] In some embodiments, the sugar includes monosaccharides, preferably glucose and / or xylose; in some embodiments, the concentration of sugar in the mixture is 20-110 g / L, preferably 30-100 g / L, preferably 40-90 g / L.

[0024] The H-type cation exchange resin has a basic skeleton of styrene-divinylbenzene copolymer, a functional group of sulfonic acid, a cross-linking degree of 4 to 6, a particle size of 50 to 350 μm, preferably 75 to 300 μm, and a total exchange capacity of ≥1 meq / g. Moisture content ≥60%.

[0025] Wherein, the eluent is water.

[0026] The simulated moving bed system needs to switch columns n times; preferably, the column switching interval is 5 to 40 minutes, preferably 15 to 30 minutes, and more preferably 18 to 25 minutes, such as 20 minutes.

[0027] The flow rates of each zone are controlled to meet the following requirements during switching: the flow rate in zone I should ensure that only eluent (water) remains in the column when zone I switches to zone VIII; the flow rate in zone II should ensure that only organic acids remain in the column when zone I switches to zone I; the flow rate in zone III should ensure that only monosaccharide components flow out of its outlet; the flow rate in zone IV should ensure that no monosaccharide components flow out of its outlet (only eluent); the flow rate in zone V should ensure that only eluent (water) remains in the column when zone IV switches to zone IV; the flow rate in zone VI should ensure that only organic acids and monosaccharides remain in the column when zone V switches to zone V; the flow rate in zone VII should ensure that only inorganic acids remain in its outlet; and the flow rate in zone VIII should ensure that no inorganic acids remain in its outlet (only eluent). The specific flow rate parameters can be adjusted accordingly based on the column height and column switching time in the process; for example, when the column switching interval is 20 minutes and the single column height is 28 cm, the flow rate ranges for each zone are shown in Table 1.

[0028] Table 1

[0029]

[0030] Among them, the relationship between the flow rate of each zone and the external flow rate is: the feed inlet flow rate Q F =Q VII -Q VI ; Eluent port-1 flow Q D1 =Q I -Q VIII ; Eluent port-2 flow Q D2 =Q V -Q IV ; Sulfuric acid outlet flow Q R =Q VII -Q VIII ; Monosaccharide outlet flow Q i =Q III -Q IV ;Organic acid outlet flow Q E =Q I -Q II ;Q V -Q VI =Q III -Q II Among them, Q I ~Q VIII These are the flow rates of zones I to VIII respectively.

[0031] After separation by the process of the present invention, the dilution of the inorganic acid is less than 20%, preferably less than 15%, and preferably less than 12%; the purity and yield of the inorganic acid and sugar are both above 97%, preferably, the recovery rates of sulfuric acid and xylose are both above 98%, and the mass purity of xylose and sulfuric acid are both above 99%; and less than 2 mL of eluent, preferably less than 1.5 mL, and preferably less than 1 mL, is required to produce 1 g of sugar.

[0032] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0033] (1) The present invention does not require the use of other reagents during the entire separation process, and only requires the use of deionized water, further reducing the consumption of additional reagents.

[0034] (2) The present invention is provided with two solvent regeneration zones, which further reduces the consumption of deionized water. This advantage cannot be achieved by other existing technologies.

[0035] (3) The H-type cation exchange resin used in the present invention has good performance in separating sulfuric acid, organic acid and sugar when the single column feed volume is 0.1BV. This advantage cannot be achieved by other existing technologies.

[0036] (4) The present invention can achieve the recovery of sulfuric acid without excessive dilution while ensuring the purity of sugar, further reducing the cost of sulfuric acid concentration and reuse. This advantage cannot be achieved by other existing technologies.

[0037] (5) The present invention can achieve continuous high-purity and high-recovery purification and collection of sugars, organic acids and sulfuric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0039] Figure 1 It is a process flow chart of the present invention.

[0040] Figure 2 Switch order diagram for columns.

[0041] Figure 3 This is the single-column separation result diagram of xylose, sulfuric acid and acetic acid in implementation case 1.

[0042] Figure 4 This is the single-column separation result diagram of xylose, sulfuric acid and acetic acid in comparative case 1. DETAILED DESCRIPTION

[0043] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0044] The composition of the detoxified corncob hydrolyzate described in the following examples is shown in Table 2.

[0045] Table 2

[0046]

[0047] In the following examples, the concentrations of sulfuric acid, glucose, xylose, and acetic acid were determined using high-performance liquid chromatography (HPLC, Agilent 1200 Series, USA). The detector was a differential refractive index detector (RID); the column was a Bio-Rad Aminex HPX-87 ion-exclusion column (300 mm × 7.8 mm, 9 μm); the mobile phase was a 5 mmol / L H₂SO₄ solution; the flow rate was 0.6 mL / min; the column temperature was 328.15 K; and the injection volume was 20 μL.

[0048] In the following examples, unless otherwise specified, the gel-type strongly acidic H-type cation exchange resin has a styrene-divinylbenzene copolymer as its basic skeleton, a sulfonic acid functional group, a cross-linking degree of 4, a particle size of 75 to 200 μm, and a total exchange capacity of 1.3 meq / g. Moisture content ≥60%.

[0049] The calculation formulas for the technical indicators in the following embodiments are as follows:

[0050]

[0051]

[0052]

[0053]

[0054] Example 1: Three-component separation performance test of a single column of H-type cation exchange resin

[0055] Liquid to be separated: According to Table 2, xylose, sulfuric acid, acetic acid, and water were compounded to obtain mixed liquids with concentrations of 50 g / L, 20 g / L, and 6 g / L, respectively.

[0056] Chromatographic column filling: Weigh a certain mass of gel-type strongly acidic H-type cation exchange resin and transfer it to a glass chromatographic column (column inner diameter is 2.2 cm, gel-type strongly acidic H-type cation exchange resin filling height is 28 cm), and continuously rinse the resin in the column with pure water to ensure that the resin is evenly filled until the resin height is constant.

[0057] Separation: At room temperature, the injection and elution flows were controlled at 0.6 BV / h by a peristaltic pump, and the injection volume was 0.1 BV. After the injection, the eluent (water) was replaced, and the effluent at the column outlet was collected regularly by an automatic fraction collector (5 min / tube).

[0058] Detect the concentration of each component in the effluent, with concentration as the vertical axis and volume as the horizontal axis. The effect of separating the three components is as follows: Figure 3 As shown, the calculated separations of sulfuric acid and xylose, and xylose and acetic acid in this example are both nearly 1. The resin's excellent separation performance ensures the feasibility of the process. This indicates that the gel-type, strongly acidic H-type cation exchange resin described herein can achieve baseline separation of the three components of inorganic acid, monosaccharide, and organic acid at a feed rate of 0.1 BV.

[0059] Comparative Case 1: Three-component separation performance test of a single column of H-type cation exchange resin with a cross-linking degree of 8

[0060] The experimental steps and conditions were the same as those in Example 1. The crosslinking degree of the H-type cation exchange resin used was 8. The results were as follows: Figure 4 As shown, xylose and acetic acid cannot be baseline separated, which illustrates the advantage of the H-type cation exchange resin used in this patent.

[0061] Example 2: Three-component separation and purification test using eight-zone SMB

[0062] The feed liquid to be separated is the same as that in Example 1.

[0063] Chromatographic column specifications: column inner diameter is 2.2 cm, and the filling height of gel-type strongly acidic H-type cation exchange resin is 28 cm.

[0064] The eight-zone SMB performs a three-component separation and purification process such as Figure 1 As shown, it consists of 16 packed chromatographic columns, with three inlets (feed port, eluent port-1 and eluent port-2) and three outlets (sulfuric acid outlet-R port, xylose outlet-I port and acetic acid outlet-E port), and every two columns form a zone, with a total of eight zones (zone I, zone II, zone III, zone IV, zone V, zone VI, zone VII and zone VIII).

[0065] The feed port (the inlet of the solution to be separated) is set at the inlet of zone VII, the eluent port-1 (the inlet of deionized water) is set at the inlet of zone I, the eluent port-2 (the inlet of deionized water) is set at the inlet of zone V, the sulfuric acid outlet-R port, the xylose outlet-I port and the acetic acid outlet-E port are set at the outlets of zone VII, zone III and zone I respectively. At the same time, the outlet liquid of zone V is directly transported to the inlet of zone III. The flow direction of the mobile phase is clockwise, while the switching direction of the chromatographic column is opposite to it.

[0066] The entire process feed and product collection are operated simultaneously to achieve the purpose of continuous separation of the three components. Each cycle requires 16 steps of column switching, as shown in the following example. Figure 2 shown.

[0067] The flow rates of each zone are shown in Table 3, and the column switching interval is 20 min.

[0068] Table 3

[0069]

[0070] Feed inlet flow Q F =Q VII -Q VI ,

[0071] Eluent port-1 flow rate Q D1 =Q I -Q VIII ,

[0072] Eluent port-2 flow Q D2 =Q V -Q IV ,

[0073] Sulfuric acid outlet-R port flow rate Q R =Q VII -Q VIII ,

[0074] Xylose outlet-I port flow rate Q i =Q III -QIV ,

[0075] Acetic acid outlet-E flow Q E =Q I -Q II ,

[0076] Q V -Q VI =Q III -Q II

[0077] After the above process was run and balanced, the obtained liquid was tested. The results are shown in Table 4:

[0078] Table 4

[0079]

[0080] From the table above, we can see that the purity of sulfuric acid and xylose is above 99%, and the recovery rate of both is above 98%. At the same time, the concentration of collected sulfuric acid is only diluted by 10%, and the solvent consumption is only 0.09 mL of deionized water per 1 g of xylose produced.

[0081] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A process for separating sugar and acid, characterized in that: The mixed liquid containing inorganic acid, sugar and organic acid is treated by adsorption using a simulated moving bed system to separate the inorganic acid, sugar and organic acid; The simulated moving bed system is composed of n chromatographic columns filled with H-type cation exchange resin connected in series into a ring, n≥8, and every 1 to 4 columns constitute a zone, and there are eight zones, namely, stationary phase regeneration zone I, separation zone II, separation zone III, eluent regeneration zone IV, stationary phase regeneration zone V, separation zone VI, separation zone VII, and eluent regeneration zone VIII; The mixed liquid flows in a clockwise direction; a feed port is provided at the inlet of zone VII, a first eluent inlet is provided at the inlet of zone I, a second eluent inlet is provided at the inlet of zone V, a first outlet is provided at the outlet of zone VII, a second outlet is provided at the outlet of zone I, and a third outlet is provided at the outlet of zone III; the outlet of zone VI is connected to the inlet of zone III; the effluent from the outlet of zone V is transported to the inlet of zone III; The chromatographic columns are switched in a counterclockwise direction.

2. The process for separating sugar and acid according to claim 1, characterized in that: The inorganic acid includes sulfuric acid.

3. The process for separating sugar and acid according to claim 1, characterized in that: The organic acid includes formic acid and / or acetic acid.

4. The process for separating sugar and acid according to claim 1, characterized in that: The sugars include monosaccharides.

5. The process for separating sugar and acid according to claim 1, characterized in that: The sugar is glucose and / or xylose.

6. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of the inorganic acid is 5-70 g / L.

7. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of the inorganic acid is 10-60 g / L.

8. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of the inorganic acid is 15-50 g / L.

9. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of the organic acid is 1-40 g / L.

10. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of the organic acid is 2-30 g / L.

11. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of the organic acid is 3-20 g / L.

12. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of sugar is 20-110 g / L.

13. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of sugar is 30-100 g / L.

14. The process for separating sugar and acid according to claim 1, characterized in that: In the mixed solution, the concentration of sugar is 40-90 g / L.

15. The process for separating sugar and acid according to claim 1, characterized in that: The H-type cation exchange resin has a styrene-divinylbenzene copolymer as a basic skeleton, a sulfonic acid functional group, a cross-linking degree of 4-6, a particle size of 50-350 μm, a total exchange capacity of ≥1 meq / g, an average pore diameter of ≥10 Å, and a water content of ≥60%.

16. The process for separating sugar and acid according to claim 1, characterized in that: The particle size of the H-type cation exchange resin is 75-300 μm.

17. The process for separating sugar and acid according to claim 1, characterized in that: The eluent is water.

18. The process for separating sugar and acid according to claim 1, characterized in that: The simulated moving bed system requires switching columns n times.

19. The process for separating sugar and acid according to claim 18, characterized in that: The column switching interval is 5~40min.

20. The process for separating sugar and acid according to claim 18, characterized in that: The column switching interval is 15~30 minutes.

21. The process for separating sugar and acid according to claim 18, characterized in that: The column switching interval is 18~25 minutes.

22. The process for separating sugar and acid according to claim 1, characterized in that: Control the rate of each zone so that it meets the following requirements during switching: There is only eluent in the column when zone I switches to zone VIII; The column where zone II is switched to zone I contains only organic acids; Only monosaccharide components flow out from the outlet of zone III; There is only eluent at the outlet of zone IV; There is only eluent in the column when zone V switches to zone IV; The column switched from zone VI to zone V contained only organic acid and monosaccharide components; Only inorganic acid components flow out from the outlet of zone VII; There is only eluent at the outflow port of zone VIII.

23. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: The dilution of the inorganic acid is below 20%.

24. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: The dilution of the inorganic acid is below 15%.

25. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: The dilution of the inorganic acid is below 12%.

26. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: The purity and yield of the inorganic acid and sugar are both above 97%.

27. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: Less than 2 mL of eluent is required to produce 1 g of sugar.

28. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: Less than 1.5 mL of eluent is required to produce 1 g of sugar.

29. The process for separating sugars and acids according to any one of claims 1 to 22, characterized in that: Less than 1 mL of eluent is required to produce 1 g of sugar.

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