JP6084198B2 - Economic process for the production of xylose from saccharified liquid using electrodialysis and direct recovery methods - Google Patents

Description

  The present invention eliminates processes that generate a large amount of wastewater such as neutralization and ion purification processes from the existing xylose production process, and is not only environmentally friendly, but also simplifies the process to reduce production costs. The present invention relates to an economical process for producing xylose.

Conventionally, precipitation methods and ion exchange resin methods are most commonly used as methods for purifying useful sugar components including xylose from sulfuric acid hydrolysates. Among them, the ion exchange resin method is widely used commercially because it has a low facility cost and has a merit that it is a process that has been used traditionally. However, since the amount of wastewater containing high-concentration salt is generated during the regeneration of ion exchange resin and the burden of wastewater treatment is unavoidable, the amount of chemical substances used and wastewater Development of an alternative technology that can reduce the amount of generation is desired.
In recent years, as a new separation technique, a method of desalting molasses and fermentation broth by electrodialysis and effectively utilizing resources is well known. For example, Patent Document 1 below discloses a method for producing xylose from tropical fruit biomass through hydrolysis, neutralization, precipitation, filtration, electrodialysis and ion exchange resin. However, ion exchange membrane contamination has been pointed out as a problem of such electrodialysis devices, and such a contamination phenomenon not only causes a reduction in the efficiency of the device, but also shortens the lifetime of the membrane. Is well known.
In order to avoid such problems, pretreatment such as treatment with a water softening device or an anion exchange resin has been tried (see, for example, Patent Document 2 below), but it must undergo multistage pretreatment. In addition, there is a drawback in that the use of sub-materials is unavoidable, which increases the cost, and there is a limit to industrial application. For example, Patent Document 3 below relates to a method for recovering lactic acid by an electrodialysis process, and a merit (efficiency and environmental friendliness) of a recirculation process of some separated substances (ammonium sulfate) and an electrodialysis process. ) Is described. However, electrodialysis still has problems in membrane applications such as membrane cost, membrane contamination and long-term stability.

Korean Patent Publication No. 2008-0074687 JP 54-67093 A Korean Patent Publication No. 2001-0107331

As a result of intensive studies focusing on the above-mentioned problems, the present inventors have provided a pH range capable of preventing a scale that becomes a source of contamination of an ion exchange membrane during electrodialysis, thereby improving productivity due to membrane contamination. By preventing the decrease, it was possible to reduce the burden of the huge initial investment cost and operation cost and overcome the limitations of the industrial application of electrodialysis. In addition, by removing the ion exchange resin process through a direct recovery process that maximizes the advantages of high-purity extraction, the burden on wastewater treatment of high-concentration salt is reduced and a simplified xylose production process is completed. It was.
Therefore, an object of the present invention is to extract as much as possible soluble components from tropical fruit biomass through countercurrent extraction, and to selectively separate and recover sulfate ions from a high concentration extract. By reusing it repeatedly in the process and preventing contamination of the ion exchange membrane of the electrodialyzer, it can be operated for a long time without chemical washing, and the organic matter separated from sulfuric acid is concentrated and directly converted into crystals. It is to provide a recovery step.

  In order to achieve the above object, the present invention comprises: a) a step of countercurrent extraction of tropical fruit biomass by a sulfuric acid hydrolysis reaction; b) adjusting the pH of the extract to 1.5 to 2.5; A step of performing decolorization and filtration; c) a step of performing desalting by introducing the filtrate into an electrodialyzer; and d) recycling the sulfuric acid waste liquid recovered in step c) to the step a). And a step of concentrating and directly recovering the desalted organic matter to obtain xylose crystals, to provide a process for producing xylose.

  When xylose is produced using an electrodialysis apparatus and a direct recovery process according to the present invention, not only can the burden on the environment associated with wastewater treatment be reduced, but also the production cost can be reduced by simplifying the process. can do. Thereby, this invention can provide the manufacturing process of the low pollution and pollution-free xylose which can respond | correspond actively to the reduction of raw material cost and prevention of environmental pollution.

FIG. 1 is a system diagram of a process for producing xylose using a conventional neutralization and ion exchange method and an electrodialysis process, and a process for producing xylose through a simplification process using electrodialysis and a direct recovery method according to the present invention. The comparison figure of a system diagram is shown. FIG. 2 shows the details of a process for producing xylose by separating organic substances and sulfuric acid through the electrodialysis process according to the present invention, reusing the collected sulfuric acid repeatedly, and directly crystallizing the organic substances. FIG. FIG. 3 is a diagram showing the details of the flow of the countercurrent multistage extraction process used in the present invention. FIG. 4 is a graph showing changes in electrical conductivity depending on processing time in the electrodialysis apparatus used in the present invention.

  The present invention includes a) a step of countercurrent extraction of tropical fruit biomass by sulfuric acid hydrolysis reaction, b) a step of adjusting the pH of the extract to 1.5 to 2.5, and performing decolorization and filtration; c ) A step in which the filtrate is introduced into an electrodialyzer to perform desalting; d) the sulfuric acid waste liquid recovered in step c) is recycled to step a), and the desalted organic matter is concentrated. And a step of directly recovering to obtain xylose crystals, and providing a process for producing xylose characterized by comprising:

  The production process of the xylose of the present invention is shown in FIG. 2, and the production process of the xylose of the present invention will be described below in detail with reference to the accompanying drawings.

The tropical fruit biomass 9 may be dried coconut shell, palm shell or palm empty bunch (OPEFB).
In the hydrolysis, a 2,000 to 50,000 ppm sulfuric acid solution 10 is added to the tropical fruit biomass 9, and the reaction temperature is 100 to 200 ° C. and the reaction pressure is 0 to 10 kgf / cm ² . It is performed by reacting for a time.

  Extraction is performed under the conditions of the hydrolysis reaction, and countercurrent extraction can be performed using the extractor 1 shown in FIG.

  The sugar composition ratio of the extract 11 obtained by the countercurrent extraction step is 60 to 90%, preferably 80 to 90% of the separated mixed sugar solution.

  The extract 11 is decolorized using activated carbon and filtered by a filter press 2 or an ultrafiltration device 2 to remove suspended substances. Specific examples of the present invention include filtration using a 0.5 μm mesh filter cloth, filtration using a filter press, and filtration using an ultrafiltration device.

  The pH of the filtrate 12 from which the suspended substances have been removed is adjusted to 1.5 to 2.5. This is to prevent contamination of the ion exchange membrane by preventing the formation of scales in the hydrolyzed solution containing substances that contaminate the electrodialysis membrane such as proteins, dyes and humic substances. .

  In step c), the recovered sulfuric acid waste solution 13 can be recycled by the extraction process in step a) and reused for the next extraction. The recovered sulfuric acid can be reused continuously and repeatedly. Preferably, 2,000 to 4,000 ppm of sulfuric acid is further added to the recovered sulfuric acid waste solution, and more preferably the final concentration of the extracted sulfuric acid. Can be reused by adding 25,000 ppm.

  In the step b), the decolored filtrate 12 whose pH has been adjusted is put into a diluting tank of the electrodialyzer 3, and the electrical conductivity (conductivity) of the organic substance 14 is 1,500 μS / cm or less, preferably 1 And desalting until 000 μS / cm or less.

  The desalted organic substance 14 is sent to the concentrator 4 and concentrated to a sugar concentration of 50 to 70 Brix (Bx). Then, the concentrated concentrate 15 is vacuum crystallized or cooled crystallized through a direct recovery process to obtain xylose. It was collected. The direct recovery step can be preferably performed over 3 steps 5, 6, and 7.

The following examples are for explaining the present invention in more detail, and these examples do not limit the technical scope of the present invention.
Example 1

Example 2 Production of high-concentration xylose by countercurrent extraction The simplest extraction method is to perform repeated extraction with a pure solvent. In the present invention, soluble components are extracted as completely as possible from raw materials. At the same time, countercurrent extraction was performed to obtain a highly concentrated extract.

  When a tropical fruit biomass and a sulfuric acid solution are reacted for a predetermined time using an extractor, they are separated into an upper layer solution and a lower layer slurry and sequentially move in opposite directions. That is, the primary extract b and the secondary extract c of a solution composed of a solvent and a solute move sequentially in the opposite direction to the solid phase and dissolve the solute while moving through each stage. Extract. The flow of the countercurrent multistage extraction process is shown in FIG.

  Specifically, the extractor is composed of a stage 1 extraction reactor and a stage 2 extraction reactor, and the continuous countercurrent multistage extraction method includes the following steps: Brix 3 obtained from the stage 1 extraction reactor A step of feeding a low concentration primary extract b of ˜7 to the stage 2 extraction reactor, and passing the fed low concentration primary extract b through the stage 2 extraction reactor to increase the Brix 10-20 Obtaining a xylose secondary extract c of high concentration and high purity.

  Under the same conditions as in Example 1, the extraction yields in the simple batch extraction method and the multi-stage countercurrent extraction method in which extraction was repeated with a pure solvent were compared. High extraction yields of 90-80% were obtained by multistage countercurrent extraction.

  The pH 0.8-1.2 acid hydrolyzate c obtained by the countercurrent extraction is adjusted to pH 1.5-2.5 with caustic soda, and then filtered with activated carbon and a 0.5 μm mesh filter cloth. And filtered to remove suspended solids.

Example 3: Desalted electrodialysis (Electrodialysis)
The desalting electrodialysis process according to the present invention, such as the desalting rate of sulfate ions and the loss rate of organic substances (sugar) when the acid hydrolyzate produced by the countercurrent extraction process is purified using a desalting electrodialyzer. In order to investigate the separability and economic efficiency of organic substances (sugar) and sulfuric acid, the current efficiency and energy consumption were examined.
The sugar concentration of the reaction solution subjected to desalting and filtration was Brix 10 to 15, pH 1.5 to 2.5. The voltage was a constant voltage of 40 to 70 V using a DC power supply (120 V, 30 A), and the temperature of the solution was kept constant at about 40 to 70 ° C. using a heat exchange coil. Desalting was performed at a flow rate of 6 to 8 L / min for 100 to 150 minutes until the electrical conductivity reached 1,500 μS / cm or less.
At this time, a 3-compartment type electrodialyzer is used, and the ion membrane is composed of a strongly acidic cation exchange membrane and a strongly basic anion exchange membrane, and has a total effective membrane area. Was 0.6 m ² . The results of electrodialysis are shown in Table 3.

  The sulfuric acid desalting rate can be obtained from the value of the electrical conductivity of the dilution tank, and the loss rate of the organic matter can be confirmed by the change in the Brix value of the dilution tank.

Sulfuric acid desalination rate = 100 − {(end value of electrical conductivity / treated value of electrical conductivity) * 100}
Organic Loss Rate = 100 − {(Final Brix Value / First Brix Value) * 100}
As a result of the calculation, the desalting rate of sulfuric acid was 98%, and the loss rate of organic substance (sugar) was 3.4%.

Example 4: Measurement of ion exchange membrane contamination index Under the same conditions as in Example 3, the ion exchange capacity and performance by adjusting the pH of the acid hydrolyzate were measured. In the case of pH 1.5 to 2.5, there is not much decrease in the ion exchange capacity and performance of the membrane, suggesting that little membrane contamination has occurred. The results are shown in Table 4.

Example 5: Reuse of recovered sulfuric acid Xylose extraction when the recovered sulfuric acid is reused in the next extraction step in order to investigate the possibility of reusing sulfuric acid recovered from the electrodialysis step and the economics The yield was measured.
As a result of the measurement, as shown in Table 5, the extraction yield when only the recovered sulfuric acid is used is 10.61%, and the extraction yield when the concentration is increased by mixing sulfuric acid and recovered sulfuric acid is The result was 12.80%, which was almost the same as the control group. Table 4 shows the extraction yield when a minimum amount of sulfuric acid was added to the recovered sulfuric acid and reused repeatedly. In the extraction experiment using sulfuric acid which was reused six times in total, the average yield was 12.57%, which is shown in Table 6. From this, it can be seen that the recovered sulfuric acid can be reused continuously and repeatedly.

Example 6: Recovery of xylose through a direct recovery process To examine the direct crystal recovery of desalted organics from the electrodialysis process, the sugar concentration of the recovered organics was concentrated from 10-15 Brix to 50-70 Brix. The recovery yield of xylose was measured through a direct recovery process over 3 steps.
As a result of the measurement, as shown in Table 6, the recovery rate of recovered xylose (5, 6, 7 in FIG. 2) was 33.5%, and the secondary crystal mother liquor (16, 17 in FIG. 2). The total recovery rate of xylose when re-recovered was crystallized was 87%, indicating almost the same recovery rate of xylose as that obtained through the existing ion purification step.

Claims (4)

A process for producing xylose by sulfuric acid hydrolysis of tropical fruit biomass,
a) a counter-current extraction of tropical fruit biomass by sulfuric acid hydrolysis reaction to obtain an extract; b) adjusting the pH of the extract to 1.5 to 2.5, decolorizing and filtering, filtrate Wherein the composition ratio of xylose sugar in the filtrate is 80% or more ,
c) adding the filtrate to an electrodialyzer to perform desalting to obtain a sulfuric acid waste solution and desalted organic matter;
d) recycling the sulfuric acid waste solution recovered in step c) to step a), concentrating the desalted organic matter and directly recovering to obtain xylose crystals;
As well as
The method of producing xylose, wherein the steps a) to c ) are sequentially performed without a precipitation method and an ion purification step.
The method for producing xylose according to claim 1, wherein 2,000 to 4,000 ppm of sulfuric acid is further added to the sulfuric acid waste solution recovered in step c) and recycled to step a). .
The method for producing xylose according to claim 1, wherein in the step c), desalting is performed until the electric conductivity of the filtrate becomes 1,000 µS / cm or less.
  The method for producing xylose according to claim 1, wherein in the step a), the sugar composition ratio of the extract is 60 to 90% by weight of the separated mixed sugar solution.

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