Method for separating xylose from inorganic acid in xylose production process

Abstract

The invention discloses a xylose and inorganic acid separation method in a xylose production process, which comprises the following steps: diluting xylose hydrolysate to obtain primarily diluted low-concentration hydrolysate; xylose and inorganic acid in the low-concentration hydrolysate are separated through a molecular sieve membrane, a low-concentration acid solution and a high-concentration xylose solution are obtained, and the obtained high-concentration xylose solution is discharged to the next procedure; inorganic acid and water in the low-concentration acid solution are separated through a molecular sieve membrane, water and a high-concentration acid solution are obtained, the obtained high-concentration acid solution is discharged to the xylose production process to be reused, and the obtained water is used for diluting the xylose hydrolysate. After the xylose hydrolysate is diluted, inorganic acid in the hydrolysate is separated by adopting the molecular sieve membrane, so that the pH value is increased in a manner of reducing the content of the inorganic acid, the process requirement is met, most inorganic acid and water can be recycled in the whole process, the generation of wastewater is greatly reduced, the cost is reduced, and the environmental burden is also reduced.

Description

Technical Field

[0001] The present invention relates to the field of xylose production, and particularly to a method for separating xylose and inorganic acid during the xylose production process. Background Art

[0002] Currently, in the process of producing xylose, the neutralization method is generally used to remove acid to prepare xylose. The process route is as follows: raw materials (i.e., agricultural fiber waste) are successively subjected to raw material pretreatment, hydrolysis, neutralization, decolorization, ion exchange, concentration, crystallization, and finally xylose crystals are separated. Since xylose is a reducing sugar that is stable under acidic conditions and extremely unstable under alkaline conditions, when neutralizing the hydrolysis solution, the local pH value is too high, which will inevitably cause some xylose to denature and affect the quality of the finished product. At the same time, a large amount of wastewater will be generated during the entire production process, greatly wasting water resources. Treating and discharging the wastewater will incur a great cost and also cause a serious burden on the environment. Summary of the Invention

[0003] The object of the present invention is to provide a method for separating xylose and inorganic acid during the xylose production process. The specific technical solution is as follows:

[0004] A method for separating xylose and inorganic acid during the xylose production process includes: diluting the xylose hydrolysis solution to obtain a preliminarily diluted low-concentration hydrolysis solution; separating xylose and inorganic acid in the low-concentration hydrolysis solution by using a molecular sieve membrane to obtain a low-concentration acid solution and a high-concentration xylose solution, wherein the obtained high-concentration xylose solution is discharged to the next process; separating inorganic acid and water in the low-concentration acid solution by using a molecular sieve membrane to obtain water and a high-concentration acid solution, wherein the obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the xylose hydrolysis solution.

[0005] Before the high-concentration xylose solution is discharged to the next process, it is diluted with water again to obtain a low-concentration xylose solution; separating xylose and inorganic acid in the low-concentration xylose solution by using a molecular sieve membrane to obtain an ultra-high-concentration xylose solution and an extremely low-concentration acid solution, wherein the obtained ultra-high-concentration xylose solution is discharged to the next process for crystallization; separating inorganic acid and water in the extremely low-concentration acid solution by using a molecular sieve membrane to obtain water and a high-concentration acid solution, wherein the obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the high-concentration xylose solution.

[0006] When separating inorganic acid and water in the low-concentration acid solution and the extremely low-concentration acid solution, the same molecular sieve membrane can be used, and the obtained water is added to the xylose hydrolysis solution and the high-concentration xylose solution as needed respectively.

[0007] When adding water to the xylose hydrolysis solution, the amount of added water is 1-4 times that of the xylose hydrolysis solution, that is, the concentration of each component in the xylose hydrolysis solution is diluted to 20%-50% of the original.

[0008] When using a molecular sieve membrane to separate xylose and inorganic acids in a low-concentration hydrolysis solution, 50%-90% of the low-concentration hydrolysis solution is separated. That is, the concentration of inorganic acid components in the obtained low-concentration acid solution and high-concentration xylose solution remains unchanged. The concentration of xylose components in the high-concentration xylose solution is 2-10 times that of the xylose components in the low-concentration hydrolysis solution. The greater the dilution factor, the greater the separation ratio.

[0009] When adding water to dilute the high-concentration xylose solution before discharging, the amount of water added is 2-9 times that of the high-concentration xylose solution, that is, the concentration of each component in the high-concentration xylose solution is diluted to 10%-33% of the original.

[0010] When using a molecular sieve membrane to separate xylose and inorganic acids in a low-concentration xylose solution, 50%-90% of the low-concentration xylose solution is separated. That is, the concentration of inorganic acid components in the obtained ultra-high-concentration xylose solution and extremely low-concentration acid solution remains unchanged. The xylose in the ultra-high-concentration xylose solution is 2-10 times that of the xylose components in the low-concentration xylose solution. The greater the dilution factor, the greater the separation ratio.

[0011] When separating inorganic acid and water from the low-concentration acid solution, 80%-90% of the low-concentration acid solution is separated. That is, the concentration of inorganic acid in the obtained high-concentration acid solution is 5-10 times that of the inorganic acid concentration in the low-concentration acid solution.

[0012] When separating inorganic acid and water from the extremely low-concentration acid solution, 80%-90% of the extremely low-concentration acid solution is separated. That is, the concentration of inorganic acid in the obtained high-concentration acid solution is 5-10 times that of the inorganic acid concentration in the extremely low-concentration acid solution.

[0013] The above technical solutions of the present invention have the following beneficial technical effects: By diluting the xylose hydrolysis solution and then using a molecular sieve membrane to separate the inorganic acid in the hydrolysis solution, the pH value is increased by reducing the content of inorganic acid to meet the process requirements, thereby avoiding the occurrence of too high local pH value. The separated acid solution can be further separated. The separated high-concentration acid solution then enters the pretreatment to produce xylose hydrolysis solution, and the separated water is used to dilute the xylose hydrolysis solution. Most of the inorganic acid and water can be reused in the whole process, greatly reducing the generation of wastewater, reducing costs and also reducing the environmental burden. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic flow chart of Embodiment 1 of the present invention;

[0015] Figure 2 is a schematic flow chart of Embodiment 2 of the present invention;

[0016] Figure 3It is a schematic flowchart of the third embodiment of the present invention. Detailed implementation manners

[0017] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the specific implementation manners and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0018] Embodiment 1

[0019] A method for separating xylose and inorganic acid during the production of xylose, comprising: diluting the xylose hydrolysis solution to obtain a preliminarily diluted low-concentration hydrolysis solution; separating xylose and inorganic acid in the low-concentration hydrolysis solution by using a molecular sieve membrane to obtain a low-concentration acid solution and a high-concentration xylose solution, wherein the obtained high-concentration xylose solution is discharged to the next process; separating inorganic acid and water in the low-concentration acid solution by using a molecular sieve membrane to obtain water and a high-concentration acid solution, wherein the obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the xylose hydrolysis solution. By diluting the xylose hydrolysis solution and then separating the inorganic acid in the hydrolysis solution by using a molecular sieve membrane, the pH value is increased by reducing the content of inorganic acid to meet the process requirements, thereby avoiding the occurrence of a too high local pH value. The separated acid solution can be further separated. The separated high-concentration acid solution enters the pretreatment to produce the xylose hydrolysis solution, and the separated water dilutes the xylose hydrolysis solution. Most of the inorganic acid and water can be reused in the whole process, greatly reducing the generation of wastewater, reducing costs and also reducing the environmental burden.

[0020] When adding water to the xylose hydrolysis solution, the amount of added water is 1-4 times that of the xylose hydrolysis solution, that is, the concentrations of the components in the xylose hydrolysis solution are diluted to 20%-50% of the original. When separating xylose and inorganic acid in the low-concentration hydrolysis solution by using a molecular sieve membrane, 50%-90% of the low-concentration hydrolysis solution is separated, that is, the concentration of the inorganic acid component in the obtained low-concentration acid solution and high-concentration xylose solution remains unchanged, and the concentration of the xylose component in the high-concentration xylose solution is 2-10 times that of the xylose component in the low-concentration hydrolysis solution. When separating inorganic acid and water in the low-concentration acid solution, 80%-90% of the low-concentration acid solution is separated, that is, the concentration of the inorganic acid in the obtained high-concentration acid solution is 5-10 times that of the inorganic acid in the low-concentration acid solution.

[0021] During actual production, the concentration of the xylose hydrolysate is generally about 3%, and the concentration of the inorganic acid is generally about 0.6%. In this embodiment, the concentration of the xylose hydrolysate is 3% and the concentration of the inorganic acid is generally 0.6% for illustration purposes. For better illustration, this embodiment uses relatively extreme data for example. During production, specific data can be adaptively adjusted according to actual situations such as production volume, site, and equipment investment to carry out production in a more suitable manner.

[0022] (1) Assume that 100 cubic meters of xylose hydrolysate are fed into the first buffer tank per hour. At this time, 100 cubic meters of water, which is 1 times the amount, are fed into the first buffer tank per hour. The concentration of the xylose hydrolysate in the resulting 200 cubic meters of low-concentration hydrolysate is 1.5%, and the concentration of the inorganic acid is 0.3%.

[0023] The 200 cubic meters of low-concentration hydrolysate are fed into the molecular sieve membrane for separating xylose and inorganic acid. According to the flow rate, 50% of the 100 cubic meters, which is 100 cubic meters, is separated to obtain 100 cubic meters of high-concentration xylose solution and 100 cubic meters of low-concentration acid solution. Although the xylose concentration in the 100 cubic meters of high-concentration xylose solution is still 3%, its inorganic acid concentration is reduced to 0.3%, and the pH value increases to a certain extent, basically meeting the production requirements, and it can be discharged to the next process.

[0024] The 100 cubic meters of low-concentration acid solution are fed into the molecular sieve membrane for separating water and inorganic acid. According to the flow rate, 80% of the 80 cubic meters, which is 80 cubic meters, is separated to obtain 80 cubic meters of water and 20 cubic meters of high-concentration acid solution. At this time, the inorganic acid concentration in the 20 cubic meters of high-concentration acid solution is 1.5%, basically meeting the production requirements, and it can be discharged to the pretreatment process for the production of xylose hydrolysate. The 80 cubic meters of water are discharged into the first buffer tank to dilute the xylose hydrolysate.

[0025] As above, 100 cubic meters of water are input into the process, but all of this 100 cubic meters of water circulates in the production link without additional burden. The 100 cubic meters of high-concentration xylose solution discharged to the next process replaces the acid neutralization process by reducing the acid content, avoiding the problem of local excessive pH value, and improving the reusability rate, thereby reducing the generation of wastewater.

[0026] (2) Assume that 100 cubic meters of xylose hydrolysate are fed into the first buffer tank per hour. At this time, 400 cubic meters of water, which is 4 times the amount, are fed into the first buffer tank per hour. The concentration of the xylose hydrolysate in the resulting 500 cubic meters of low-concentration hydrolysate is 0.6%, and the concentration of the inorganic acid is 0.16%.

[0027] The 500 cubic meters of low-concentration hydrolysate are fed into the molecular sieve membrane for separating xylose and inorganic acid. According to the flow rate, 90% of the 450 cubic meters, which is 450 cubic meters, is separated to obtain 50 cubic meters of high-concentration xylose solution and 450 cubic meters of low-concentration acid solution. The xylose concentration in the 50 cubic meters of high-concentration xylose solution is 6%, its inorganic acid concentration is reduced to 0.16%, and the pH value increases to a certain extent, meeting the production requirements, and it can be discharged to the next process.

[0028] Introduce 450 cubic meters of low-concentration acid solution into the molecular sieve membrane for separating water and inorganic acid. Separate 405 cubic meters of 90% of it according to the flow rate to obtain 405 cubic meters of water and 45 cubic meters of high-concentration acid solution. At this time, the concentration of inorganic acid in the 45 cubic meters of high-concentration acid solution is 1.6%, which basically meets the production requirements, and it can be discharged into the pretreatment process for the production of xylose hydrolysis solution. The 405 cubic meters of water is discharged into the first buffer tank to dilute the xylose hydrolysis solution and for equipment cleaning.

[0029] Above, 400 cubic meters of water is input into the process, but all of this 400 cubic meters of water circulates in the production process without additional burden. The 50 cubic meters of high-concentration xylose solution discharged into the next process greatly increases the xylose concentration, and replaces the acid neutralization process by reducing the acid content, avoiding the problem of local excessive pH value and greatly reducing the generation of wastewater. It should be noted that the higher the separation ratio in the production process, the heavier the burden on the equipment and the greater the risk of equipment failure. Therefore, it is necessary to select appropriate data for production.

[0030] Example Two

[0031] A method for separating xylose and inorganic acid in the production process of xylose, including: diluting the xylose hydrolysis solution to obtain a preliminarily diluted low-concentration hydrolysis solution. Using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration hydrolysis solution to obtain a low-concentration acid solution and a high-concentration xylose solution. The obtained high-concentration xylose solution is further diluted with water to obtain a low-concentration xylose solution. Using a molecular sieve membrane to separate inorganic acid and water in the low-concentration acid solution to obtain water and a high-concentration acid solution. The obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the xylose hydrolysis solution. Using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration xylose solution to obtain an ultra-high-concentration xylose solution and an extremely low-concentration acid solution. The obtained ultra-high-concentration xylose solution is discharged to the next process for crystallization. Using a molecular sieve membrane to separate inorganic acid and water in the extremely low-concentration acid solution to obtain water and a high-concentration acid solution. The obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the high-concentration xylose solution. After diluting the xylose hydrolysis solution, use a molecular sieve membrane to separate the inorganic acid in the hydrolysis solution to increase the pH value by reducing the inorganic acid content to meet the process requirements, thereby avoiding the occurrence of local excessive pH value. The separated acid solution can be separated again. The separated high-concentration acid solution enters the pretreatment to produce xylose hydrolysis solution, and the separated water dilutes the xylose hydrolysis solution. Most of the inorganic acid and water can be reused throughout the process, greatly reducing the generation of wastewater, reducing costs and also reducing the environmental burden.

[0032] When adding water to the xylose hydrolysis solution, the amount of water added is 1 - 4 times that of the xylose hydrolysis solution, that is, the concentrations of the components in the xylose hydrolysis solution are diluted to 20% - 50% of the original. When using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration hydrolysis solution, 50% - 90% of the low-concentration hydrolysis solution is separated. That is, the concentration of the inorganic acid component in the obtained low-concentration acid solution and high-concentration xylose solution remains unchanged, and the concentration of the xylose component in the high-concentration xylose solution is 2 - 10 times that of the xylose component in the low-concentration hydrolysis solution. The greater the dilution factor, the greater the separation ratio. When adding water to dilute the high-concentration xylose solution before discharging, the amount of water added is 2 - 9 times that of the high-concentration xylose solution, that is, the concentrations of the components in the high-concentration xylose solution are diluted to 10% - 33% of the original. When using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration xylose solution, 50% - 90% of the low-concentration xylose solution is separated. That is, the concentration of the inorganic acid component in the obtained ultra-high-concentration xylose solution and extremely low-concentration acid solution remains unchanged, and the xylose component in the ultra-high-concentration xylose solution is 2 - 10 times that of the xylose component in the low-concentration xylose solution. The greater the dilution factor, the greater the separation ratio.

[0033] Example 3

[0034] A method for separating xylose and inorganic acid in the xylose production process, including: diluting the xylose hydrolysis solution to obtain a preliminarily diluted low-concentration hydrolysis solution. Using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration hydrolysis solution to obtain a low-concentration acid solution and a high-concentration xylose solution, where the obtained high-concentration xylose solution is further diluted with water to obtain a low-concentration xylose solution. Using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration xylose solution to obtain an ultra-high-concentration xylose solution and an extremely low-concentration acid solution, where the obtained ultra-high-concentration xylose solution is discharged to the next process for crystallization. Using a molecular sieve membrane to separate inorganic acid and water in the low-concentration acid solution and the extremely low-concentration acid solution to obtain water and a high-concentration acid solution, where the obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the xylose hydrolysis solution and the high-concentration xylose solution. By diluting the xylose hydrolysis solution and then using a molecular sieve membrane to separate the inorganic acid in the hydrolysis solution, the pH value is increased by reducing the content of inorganic acid to meet the process requirements, thereby avoiding the occurrence of too high a local pH value. The separated acid solution can be further separated. The separated high-concentration acid solution enters the pretreatment to produce xylose hydrolysis solution, and the separated water dilutes the xylose hydrolysis solution. Most of the inorganic acid and water can be reused in the whole process, greatly reducing the generation of wastewater, reducing costs and also reducing the environmental burden.

[0035] When adding water to the xylose hydrolysis solution, the amount of water added is 1 to 4 times that of the xylose hydrolysis solution, that is, the concentration of each component in the xylose hydrolysis solution is diluted to 20% - 50% of the original. When using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration hydrolysis solution, 50% - 90% of the low-concentration hydrolysis solution is separated. That is, the concentration of the inorganic acid component in the obtained low-concentration acid solution and high-concentration xylose solution remains unchanged, and the concentration of the xylose component in the high-concentration xylose solution is 2 to 10 times that of the xylose component in the low-concentration hydrolysis solution. The greater the dilution multiple, the greater the separation ratio. When adding water for dilution again before discharging the high-concentration xylose solution, the amount of water added is 2 to 9 times that of the high-concentration xylose solution, that is, the concentration of each component in the high-concentration xylose solution is diluted to 10% - 33% of the original. When using a molecular sieve membrane to separate xylose and inorganic acid in the low-concentration xylose solution, 50% - 90% of the low-concentration xylose solution is separated. That is, the concentration of the inorganic acid component in the obtained ultra-high-concentration xylose solution and extremely low-concentration acid solution remains unchanged, and the xylose component in the ultra-high-concentration xylose solution is 2 to 10 times that of the xylose component in the low-concentration xylose solution. The greater the dilution multiple, the greater the separation ratio.

Claims

1. A method for separating xylose and inorganic acid during the production process of xylose, characterized in that, Comprising: Diluting the xylose hydrolysate to obtain a preliminarily diluted low-concentration hydrolysate; Separating xylose and inorganic acid in the low-concentration hydrolysate by using a molecular sieve membrane to obtain a low-concentration acid solution and a high-concentration xylose solution, wherein the obtained high-concentration xylose solution is discharged to the next process; Separating inorganic acid and water in the low-concentration acid solution by using a molecular sieve membrane to obtain water and a high-concentration acid solution, wherein the obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the xylose hydrolysate.

2. The method for separating xylose and inorganic acid in the xylose production process according to claim 1, characterized in that The high-concentration xylose solution is diluted with water again before being discharged to the next process to obtain a low-concentration xylose solution; Separating xylose and inorganic acid in the low-concentration xylose solution by using a molecular sieve membrane to obtain an ultra-high-concentration xylose solution and an extremely low-concentration acid solution, wherein the obtained ultra-high-concentration xylose solution is discharged to the next process for crystallization; Separating inorganic acid and water in the extremely low-concentration acid solution by using a molecular sieve membrane to obtain water and a high-concentration acid solution, wherein the obtained high-concentration acid solution is discharged for reuse in the xylose production process, and the obtained water is used to dilute the high-concentration xylose solution.

3. The method for separating xylose and inorganic acid during the xylose production process according to claim 2, characterized in that, When separating inorganic acid and water in the low-concentration acid solution and the extremely low-concentration acid solution, the same molecular sieve membrane can be used, and the obtained water is respectively added to the xylose hydrolysate and the high-concentration xylose solution as needed.

4. The method for separating xylose and inorganic acid in the xylose production process according to claim 1, characterized in that, When adding water to the xylose hydrolysate, the amount of added water is 1-4 times that of the xylose hydrolysate, that is, the concentration of each component in the xylose hydrolysate is diluted to 20%-50% of the original.

5. The method for separating xylose and inorganic acid in the xylose production process according to claim 4, wherein, When separating xylose and inorganic acid in the low-concentration hydrolysate by using a molecular sieve membrane, 50%-90% of the low-concentration hydrolysate is separated, that is, the concentration of the inorganic acid component in the obtained low-concentration acid solution and the high-concentration xylose solution remains unchanged, and the concentration of the xylose component in the high-concentration xylose solution is 2-10 times that of the xylose component in the low-concentration hydrolysate. The greater the dilution multiple, the greater the separation ratio.

6. The method for separating xylose and inorganic acid during the xylose production process according to claim 2, characterized in that, When adding water to dilute the high-concentration xylose solution again before discharging, the amount of added water is 2-9 times that of the high-concentration xylose solution, that is, the concentration of each component in the high-concentration xylose solution is diluted to 10%-33% of the original.

7. The method for separating xylose and inorganic acid in the xylose production process according to claim 6, characterized in that, When separating xylose and inorganic acid in the low-concentration xylose solution by using a molecular sieve membrane, 50%-90% of the low-concentration xylose solution is separated, that is, the concentration of the inorganic acid component in the obtained ultra-high-concentration xylose solution and the extremely low-concentration acid solution remains unchanged, and the xylose component in the ultra-high-concentration xylose solution is 2-10 times that of the xylose component in the low-concentration xylose solution. The greater the dilution multiple, the greater the separation ratio.

8. The method for separating xylose and inorganic acid during the xylose production process according to claim 1, wherein When separating inorganic acid and water in the low-concentration acid solution, 80%-90% of the low-concentration acid solution is separated, that is, the inorganic acid concentration in the obtained high-concentration acid solution is 5-10 times that of the inorganic acid concentration in the low-concentration acid solution.

9. The method for separating xylose and inorganic acid during the xylose production process according to claim 2, wherein When separating the inorganic acid and water from the extremely low-concentration acid solution, 80%-90% of the extremely low-concentration acid solution is separated, and the concentration of the inorganic acid in the resulting high-concentration acid solution is 5-10 times that of the inorganic acid in the extremely low-concentration acid solution.

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