Production method of xylose and xylitol

Abstract

The invention provides a production method of xylose and xylitol, and the production method of xylose comprises the following steps: preparation of a decolorized sugar solution: sequentially performing impurity removal, hydrolysis, neutralization filtration, first ion exchange, first concentration and activated carbon decoloration on corncobs to obtain the decolorized sugar solution; ion exchange liquid preparation: carrying out secondary ion exchange on the decolored sugar liquid to obtain the ion exchange liquid; preparing effluent: carrying out particle carbon adsorption on the ion exchange liquid at a certain flow rate to obtain the effluent; preparing a concentrated sugar solution, namely concentrating the effluent for the second time to obtain the concentrated sugar solution; and preparing a crystallization raw material: filtering the concentrated sugar solution, and concentrating for the third time to obtain the crystallization raw material. The xylose production process is improved, crystallization inhibitors are reduced, stickers are reduced, the cleanliness of feed liquid before crystallization is improved, and the replacement frequency of a filter element during precise filtration is reduced. The invention also provides a method for preparing xylitol from xylose.

Description

Technical Field

[0001] The present application relates to a method for producing xylose and xylitol. Background Art

[0002] Xylose from corn cobs is affected by the origin of the corn cobs, the weather during the growing period, and the length of storage time. Changes in impurities such as colloid in the corn cobs will affect the filtration at all levels in the xylose production process, as well as the transmittance of the xylose ion solution, especially the precision filtration step before crystallization (which requires frequent replacement and cleaning of the filter element). In addition, the xylose after crystallization takes a long time to be centrifuged, and the crystal particles are fine, with a 100-mesh sieve pass rate of >70%. The fine particles cause the product to clump after about 30 days of storage.

[0003] When xylose, which is easy to clump, is used to produce xylitol, it will also cause the xylitol product to have a long membrane filtration time, poor fluidity, high water activity, and easy caking, resulting in a short shelf life and affecting its use. Summary of the invention

[0004] To solve the above problems, the technical solution of this application is as follows:

[0005] The present application provides a method for producing xylose, which comprises the following steps:

[0006] Preparation of decolorized sugar solution: corn cobs are sequentially subjected to impurity removal, hydrolysis, neutralization filtration, first ion exchange, first concentration, and activated carbon decolorization to obtain decolorized sugar solution;

[0007] Preparation of ion exchange liquid: subject the decolorized sugar solution to a second ion exchange to obtain ion exchange liquid, wherein the xylose content of the ion exchange liquid is greater than or equal to 70%, the conductivity is less than or equal to 100us / cm, and the transmittance is greater than or equal to 70%;

[0008] Preparation of effluent: adsorb the ionized liquid on granular carbon at a certain flow rate to obtain an effluent with a light transmittance of 90% to 99%;

[0009] Preparation of concentrated sugar solution: the effluent is concentrated for a second time to obtain a concentrated sugar solution, the chromaticity of the concentrated sugar solution is ≤50;

[0010] Preparation of crystallization raw material: The concentrated sugar solution is filtered and concentrated for a third time to obtain the crystallization raw material.

[0011] In some embodiments of the present application, the transmittance of the effluent is 90% to 95%.

[0012] In some embodiments of the present application, the method for producing xylose further comprises the following steps:

[0013] Cooling crystallization: xylose powder is added to the crystallization raw material as a seed crystal, and three stages of cooling crystallization are carried out in sequence;

[0014] Preparation of wet xylose: The crystallized raw material after cooling and crystallization is grown at 25℃~30℃ for 5h~24h, and wet xylose is obtained after centrifugation;

[0015] Preparation of xylose: Xylose is obtained by drying wet xylose.

[0016] In some embodiments of the present application, the moisture content in the wet xylose is less than 1.5%; and / or,

[0017] The moisture content in xylose is less than 0.3%.

[0018] In some embodiments of the present application, the sugar concentration of the concentrated sugar solution is 60% to 65%; and / or,

[0019] The crystallization raw material sugar concentration is 80% to 85%; and / or,

[0020] In the preparation of the decolorized sugar solution, the sugar concentration of the decolorized sugar solution is 20%~30%.

[0021] In some embodiments of the present application, in the preparation of the effluent, the flow rate is 0.5~4BV / h.

[0022] In some embodiments of the present application, in the preparation of the effluent, the flow rate is 1~3BV / h.

[0023] In some embodiments of the present application, in the preparation of the crystallization raw material, the temperature of the third concentration is lower than 75°C.

[0024] In some embodiments of the present application, in the cooling crystallization, the three stages of cooling crystallization are as follows: the first stage is cooled to 70-60°C at a cooling rate of 0.3-0.6°C / h, the second stage is cooled to 55-45°C at a cooling rate of 0.75-1.2°C / h, and the third stage is cooled to 25-35°C at a cooling rate of 1.2-1.7°C / h; or,

[0025] The mesh size of xylose powder is 80 mesh to 100 mesh.

[0026] In some embodiments of the present application, in the preparation of the crystallization raw material, a 0.45 um filter membrane is used for filtration.

[0027] The present application provides the use of xylose prepared by the above method in the preparation of xylitol.

[0028] The present application provides xylitol, which is xylose prepared using the above method.

[0029] The present application provides a method for preparing xylitol using xylose prepared by the above method, which comprises the following steps:

[0030] Xylose is processed through sugaring, hydrogenation, filtration, decolorization, ion exchange, concentration, crystallization and centrifugal drying.

[0031] Compared with the prior art, the beneficial effects of this application are:

[0032] Improve the xylose production process by adding a granular carbon adsorption step after ion exchange and before crystallization. The granular carbon can adsorb residual trace pigments and colored impurities analyzed during the operation of the ion exchange resin, reduce crystallization inhibitors, reduce stickies, improve the cleanliness of the feed solution before crystallization, and reduce the frequency of filter element replacement during fine filtration.

[0033] The light transmittance of the sugar solution after adsorption by the granular carbon of the present application is between 90% and 95%, and the chromaticity is ≤50. The xylose particles obtained after crystallization of the sugar solution within this index range are large (100 mesh sieve pass rate <30%), and the mother liquor is quickly secreted during centrifugation, the centrifugation time is shortened by more than half, the moisture content of the centrifuged xylose is reduced to less than 1%, the drying energy consumption is reduced, and the product agglomeration period is extended from about 30 days to more than 12 months.

[0034] In the technical solution of the present application, a sugar solution with a light transmittance of 90.0% to 95.0% and a crystallization raw material chromaticity of ≤50 is used. The time to pass through a 0.45um filter membrane is shortened from the original 20 minutes to less than 5 minutes, the xylose centrifugation time is shortened by more than half, and the number of centrifugal washings is shortened from 2 to 3 times to 1 time, which greatly improves production efficiency. The moisture content of xylose is greatly reduced after centrifugation, and the moisture content of dried xylose is reduced to <0.1%. The pass rate of 100 mesh sieve is <30%, and no agglomeration occurs after 392 days (13 months). Within this light transmittance range, product quality is significantly improved, data fluctuations are small, and stable production is conducive.

[0035] When the xylose prepared by this method is used to produce xylitol, the membrane filtration time of the xylitol product is greatly shortened, the water activity is significantly reduced, and the anti-caking performance is also significantly improved. DETAILED DESCRIPTION

[0036] The present application is further described below in conjunction with examples. It should be understood that the examples are only used to further describe and illustrate the present application and are not used to limit the present application.

[0037] Unless otherwise defined, the technical and scientific terms in this specification have the same meaning as those generally understood by those skilled in the art. Although similar or identical methods and materials as described herein may be used in experiments or practical applications, materials and methods are described herein below. In the event of a conflict, the present specification including the definitions therein shall prevail. In addition, materials, methods and examples are provided for illustration only and are not restrictive. The present application is further described below in conjunction with specific embodiments, but is not intended to limit the scope of the present application.

[0038] In the present application, sugar concentration refers to the total sugar content in the sugar solution, which includes a small amount of miscellaneous sugars other than xylose; the sugar concentration is measured by a handheld saccharimeter.

[0039] In this application, mesh number refers to the particle size or coarseness of the material. It is generally defined as the number of mesh holes in an area of ​​1 inch × 1 inch, that is, the number of mesh holes of the screen. The mesh hole through which the material can pass is defined as the mesh number.

[0040] The present application provides a method for producing xylose, which comprises the following steps: preparation of decolorized sugar solution: subjecting corn cobs to impurity removal, hydrolysis, neutralization filtration, first ion exchange, first concentration, and activated carbon decolorization in sequence to obtain decolorized sugar solution; preparation of ionized solution: subjecting the decolorized sugar solution to a second ion exchange to obtain an ionized solution, wherein the xylose content of the ionized solution is greater than or equal to 70%, the electrical conductivity is less than or equal to 100 us / cm, and the transmittance is greater than or equal to 70%; preparation of effluent: subjecting the ionized solution to granular carbon adsorption at a certain flow rate to obtain an effluent, wherein the transmittance of the effluent is 90% to 99%, preferably 90% to 95%; preparation of concentrated sugar solution: subjecting the effluent to a second concentration to obtain a concentrated sugar solution, wherein the chromaticity of the concentrated sugar solution is ≤50; preparation of crystallization raw material: filtering and concentrating the concentrated sugar solution for a third time to obtain a crystallization raw material.

[0041] In the present application, no limitation is imposed on the concentration, as long as the purpose is achieved, and the concentration can be selected from one or more of negative pressure concentration, vacuum concentration, normal pressure concentration, triple effect concentration, centrifugal concentration, membrane concentration, electrodialysis, and MVR.

[0042] In this application, the first concentration is MVR concentration.

[0043] In the present application, the second concentration is a triple-effect concentration.

[0044] In the present application, the third concentration is negative pressure concentration.

[0045] In some embodiments of the present application, the xylose content of the ionized liquid is greater than or equal to 70%. For example, the xylose content of the ionized liquid can be 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98% and above, or any range therebetween.

[0046] In some embodiments of the present application, the conductivity of the ionized liquid is less than or equal to 100us / cm. For example, the conductivity of the ionized liquid can be 100us / cm, 98us / cm, 96us / cm, 94us / cm, 92us / cm, 90us / cm, 88us / cm, 86us / cm, 84us / cm, 82us / cm, 80us / cm, 78us / cm, 76us / cm, 74us / cm, 72us / cm, 70us / cm, 68us / cm, 66us / cm, 64us / cm, 62us / cm, 60us / cm m, 58us / cm, 56us / cm, 54us / cm, 52us / cm, 50us / cm, 48us / cm, 46us / cm, 44us / cm, 42us / cm, 40us / cm, 38us / cm, 36us / cm, 34us / cm, 32us / cm, 30us / cm, 28us / cm, 26us / cm, 24us / cm, 22us / cm, 20us / cm, 18us / cm, 16us / cm, 14us / cm, 12us / cm, 10us / cm and below, or any range therebetween.

[0047] In some embodiments of the present application, the transmittance of the ionized fluid is greater than or equal to 70%. For example, the transmittance of the ionized fluid may be 70%, 68%, 66%, 64%, 62%, 60%, 58%, 56%, 54%, 52%, 50%, 48%, 46%, 44%, 42%, 40%, 38%, 36%, 34%, 32%, 30%, 28%, 26%, 24%, 22%, 20%, 18%, 16%, 14%, 12%, 10% and below, or any range therebetween.

[0048] In some embodiments of the present application, the transmittance of the effluent can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any range therebetween.

[0049] In some embodiments of the present application, the chromaticity of the concentrated sugar solution may be 50, 45, 40, 35, 30, 25, 20, 15, 10, 5 or any range therebetween.

[0050] In some embodiments of the present application, the method for producing xylose also includes the following steps: cooling and crystallizing: adding xylose powder to the crystallization raw material as a seed crystal, and performing three stages of cooling and crystallization in sequence; preparing wet xylose: growing the crystallization raw material after cooling and crystallization at 25°C~30°C for 5h~24h, and obtaining wet xylose after centrifugation; preparing xylose: obtaining xylose by drying the wet xylose.

[0051] In some embodiments of the present application, the crystal growing temperature may be 25° C., 26° C., 27° C., 28° C., 29° C., 30° C. or any range therebetween.

[0052] In some embodiments of the present application, the crystal growing time can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h or any range therebetween.

[0053] In some embodiments of the present application, in the cooling and crystallization, the three stages of cooling and crystallization are as follows: the first stage is cooled to 70~60℃ at a cooling rate of 0.3~0.6℃ / h, the second stage is cooled to 55~45℃ at a cooling rate of 0.75~1.2℃ / h, and the third stage is cooled to 25℃~35℃ at a cooling rate of 1.2~1.7℃ / h; for example, the cooling rate in the first stage can be 0.3℃ / h, 0.4℃ / h, 0.5℃ / h, 0.6℃ / h or any range therebetween, and the first stage can be cooled to 70℃, 69℃, 68℃, 67℃, 66℃, 65℃, 64℃, 63℃, 62℃, 61℃, 60℃ or any range therebetween; the second stage The cooling rate of the first stage can be 0.75℃ / h, 0.8℃ / h, 0.9℃ / h, 1.0℃ / h, 1.1℃ / h, 1.2℃ / h or any range therebetween, and the second stage can be cooled to 55℃, 54℃, 53℃, 52℃, 51℃, 50℃, 49℃, 48℃, 47℃, 46℃, 45℃ or any range therebetween; the cooling rate of the third stage can be 1.2℃ / h, 1.3℃ / h, 1.4℃ / h, 1.5℃ / h, 1.6℃ / h, 1.7℃ / h or any range therebetween, and the third stage can be cooled to 35℃, 34℃, 33℃, 32℃, 31℃, 30℃, 29℃, 28℃, 27℃, 26℃, 25℃ or any range therebetween.

[0054] In some embodiments of the present application, the mesh number of the xylose powder is 80 mesh to 100 mesh. For example, the mesh number of the xylose powder can be 80 mesh, 82 mesh, 84 mesh, 86 mesh, 88 mesh, 90 mesh, 92 mesh, 94 mesh, 96 mesh, 98 mesh, 100 mesh or any range therebetween.

[0055] In some embodiments of the present application, the sugar concentration of the concentrated sugar solution is 60% to 65%; for example, the sugar concentration of the concentrated sugar solution may be 60%, 61%, 62%, 63%, 64%, 65% or any range therebetween.

[0056] In some embodiments of the present application, the sugar concentration of the crystallization raw material is 80% to 85%; for example, the sugar concentration of the crystallization raw material can be 80%, 81%, 82%, 83%, 84%, 85% or any range therebetween.

[0057] In some embodiments of the present application, the sugar concentration of the decolorized sugar solution is 20% to 30%; for example, the sugar concentration of the decolorized sugar solution can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any range therebetween.

[0058] In some embodiments of the present application, in the preparation of the effluent, the flow rate is 0.5~4BV / h, preferably 1~3BV / h; further adsorb residual pigments, lignin, adhesives and other trace crystallization inhibitors that are difficult to detect; for example, the flow rate can be 0.5BV / h, 1BV / h, 1.5BV / h, 2BV / h, 2.5BV / h, 3BV / h, 3.5BV / h, 4BV / h or any range therebetween. The applicant found that if the flow rate is adjusted to 0.5BV / h, the requirements of 90%~95% transmittance and chromaticity ≤50 can also be achieved, but the flow rate is too slow, the production efficiency decreases, and the production capacity decreases; when the flow rate is greater than 3BV / h, the transmittance can also reach 93.0%, but the chromaticity is greater than 50, indicating that the adsorption is not thorough enough, and the final product will agglomerate in 161 days. From the perspective of production and efficiency, the flow rate of the effluent is 1~3BV / h.

[0059] In some embodiments of the present application, in the preparation of the crystallization raw material, the temperature of the third concentration is lower than 75°C.

[0060] In some embodiments of the present application, in the preparation of the crystallization raw material, a 0.45 um filter membrane is used for filtration.

[0061] In some embodiments of the present application, the moisture content of the wet xylose is less than 1.5%; for example, the moisture content of the wet xylose may be 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3% and below, or any range therebetween.

[0062] In some embodiments of the present application, the moisture content of the xylose is less than 0.3%; for example, the moisture content of the xylose may be 0.3%, 0.28%, 0.26%, 0.24%, 0.22%, 0.20%, 0.18%, 0.16%, 0.14%, 0.12%, 0.10%, 0.08%, 0.06%, 0.04%, 0.02% and below, or any range therebetween.

[0063] In some embodiments of the present application, the xylose content in the obtained xylose product is above 99.1%, which meets the requirements of the national standard for xylose GB / T 23532-2009.

[0064] In some embodiments of the present application, the method for producing xylose comprises the following steps:

[0065] (1) The corn cobs are screened and cleaned, washed and hydrolyzed, and the hydrolyzate is neutralized and filtered to obtain a xylose-rich sugar solution. The hydrolyzed sugar solution undergoes an ion exchange to remove most of the salt and lignin. The sugar solution after the first ion exchange is concentrated to a sugar concentration of 20% to 30% by MVR, and powdered activated carbon is added for decolorization to obtain a decolorized sugar solution;

[0066] (2) The decolorized sugar solution is subjected to secondary ion exchange in the ion exchange system to further remove residual salts and obtain an ion exchange solution with a xylose content of >70%, a conductivity of <100us / cm, and a transmittance of >70%;

[0067] (3) The ionized liquid flows through the granular carbon column at a flow rate of 0.5-4 BV / h to further adsorb residual pigments, lignin, adhesives and other trace crystallization inhibitors that are difficult to detect. The effluent has a transmittance of 90%-99% and is concentrated by three effects. The temperature of the sugar solution is controlled below 75°C during concentration and the sugar concentration is 60%-65%. The color is tested and the concentrated sugar solution with a color of ≤50 is used as the raw material for crystallization.

[0068] (4) The concentrated sugar solution is finely filtered through a 0.45um filter membrane and then sent to a sugar boiling tank for negative pressure concentration at a concentration temperature of 65°C to 75°C until the sugar concentration reaches 80% to 85%;

[0069] (5) Add 0.5‰~1‰ of 80-100-mesh xylose powder as a seed crystal, and then start cooling and crystallization. In the first stage, the temperature is lowered from 75°C to 65°C at a rate of 0.5°C / h. In the second stage, the temperature is lowered from 65°C to 50°C at a rate of 1.0°C / h. In the third stage, the temperature is lowered from 50°C to 30°C at a rate of 1.4~1.7°C / h. After the cooling is completed, continue to grow crystals at 30°C for 5h~24h. During this stage, the crystals continue to grow and the yield gradually increases.

[0070] (6) After the crystal is grown, centrifuge for 1-10 minutes and observe that no mother liquid is secreted. Observe the crystal condition. If there is no yellow sugar in the crystal, dry it. If the crystal is yellow, continue centrifugation and spray deionized water for 5 seconds to wash it. After each washing until no liquid is secreted, observe the crystals in the centrifuge. Stop centrifugation when there is no yellow sugar. If there is yellow sugar, continue the centrifugation and washing operation.

[0071] (7) The centrifuged crystals are dried and packaged.

[0072] The light transmittance of the sugar solution after adsorption by the granular carbon of the present application is 90.0%~95.0%, and the chromaticity of the crystallized raw material is ≤50. The time to pass through the 0.45um filter membrane is shortened from the original 20min to less than 5min, the xylose centrifugation time is shortened by more than half, and the number of centrifugal washings is shortened from 2~3 times to 1 time, which greatly improves production efficiency. The moisture content of xylose is greatly reduced after centrifugation, and the moisture content of dried xylose is reduced to <0.1%. The pass rate of 100 mesh sieve is <30%, and no agglomeration has occurred for 392 days (13 months). Within this light transmittance range, the product quality is significantly improved, the data fluctuation is small, and it is conducive to stable production.

[0073] The present application improves the xylose production process by adding a granular carbon adsorption step after ion exchange and before crystallization, so that the granular carbon adsorbs the remaining trace pigments and the colored impurities analyzed during the operation of the ion exchange resin, reduces crystallization inhibitors, reduces stickies, improves the cleanliness of the feed liquid before crystallization, and reduces the frequency of filter element replacement during fine filtration.

[0074] Example

[0075] The corncobs are screened and cleaned, washed and hydrolyzed, and the hydrolyzate is neutralized and filtered to obtain a xylose-rich sugar solution. The hydrolyzed sugar solution undergoes the first ion exchange to remove most of the salt and lignin. The sugar solution after ion exchange is concentrated to a sugar concentration of 20% to 30%, and powdered activated carbon is added for decolorization to obtain a decolorized sugar solution;

[0076] The decolorized sugar solution was subjected to a second ion exchange to further remove residual salts and obtain a separation solution; the separation solution indicators: xylose content 71.57%, conductivity 75.2us / cm, transmittance 74.1%;

[0077] The following Examples 1-17 and Comparative Examples 1-4 use the same batch of ion exchange liquid as the feed liquid for the granular carbon column. The ion exchange liquid has the following indicators: xylose content of 71.57%, electrical conductivity of 75.2 us / cm, and light transmittance of 74.1%.

[0078] Example 1

[0079] Granular carbon adsorption: After the granular carbon column was flushed, the ion exchange liquid flowed through the granular carbon column at a flow rate of 2BV / h, and the transmittance of the effluent was tested; the transmittance of the effluent was 98.3%.

[0080] Sugar solutions with different light transmittances are collected and concentrated as raw materials for crystallization. When the light transmittances of the inlet and outlet liquids of the granular carbon column are consistent (i.e., the light transmittance of the outlet liquid is 74.1%), the feeding is stopped. Deionized water is added to push out the residual sugar solution in the column until the sugar concentration of the outlet liquid is less than 0.1%. After the granular carbon is regenerated, it is recycled.

[0081] Preparation of concentrated sugar solution: The effluent with a light transmittance of 98.3% is subjected to triple-effect concentration to obtain a concentrated sugar solution, wherein the sugar concentration of the concentrated sugar solution is 61.5% and the chromaticity of the concentrated sugar solution is 35;

[0082] Preparation of crystallization raw material: 1000mL of concentrated sugar solution was filtered through a 0.45um filter membrane and then further concentrated under negative pressure. The filtration time was 3′54″ and the concentration temperature was 65°C~70°C to obtain a crystallization raw material. The sugar concentration of the crystallization raw material was 83%. 1‰ of 80-100 mesh xylose powder was added as a seed crystal, and then the temperature was lowered to crystallize. In the first stage, the temperature was lowered from 75°C to 65°C at a rate of 0.5°C / h. In the second stage, the temperature was lowered from 65°C to 50°C at a rate of 1.0°C / h. In the third stage, the temperature was lowered from 50°C to 30°C at a rate of 1.5°C / h. The crystal was cultured at 30°C with stirring and centrifuged after 24 hours of culture.

[0083] Centrifugation: After the sugar paste enters the centrifuge, centrifugation begins. After 7 minutes, it is observed through the sight glass that no mother liquor is secreted. The crystals in the centrifuge are slightly yellow. Deionized water spray washing is started for 5 seconds. After centrifugation for 5 minutes, no washing liquid is secreted. The crystals turn white. Centrifugation is stopped. The total centrifugation time is 12 minutes. Deionized water is sprayed for washing once. The moisture content of the xylose after centrifugation (referred to as wet xylose) is 1.08%.

[0084] After centrifugation, the xylose was dried in a fluidized bed to obtain a xylose product. The sample was tested for moisture content of 0.15%, and the pass rate of 100 mesh sieve was 39.56%. The xylose content in the obtained xylose product was above 99.1%, which met the requirements of the national standard for xylose GB / T 23532-2009. 1000g was packaged and stored in a sample cabinet, and its agglomeration was observed every 7 days.

[0085] The difference between Example 2-17 and Example 1 is only in Table 1, and the rest is the same as Example 1.

[0086] Comparative Examples 1 to 3

[0087] The difference between Comparative Examples 1 to 3 and Example 1 is that the granular carbon adsorption is replaced by powdered activated carbon adsorption, and the rest is the same as Example 1. The amount of powdered activated carbon added is 0.1%, 0.5%, and 1% of the mass of the sugar solution, respectively, and the mixture is stirred at 50°C to 60°C for 30 minutes and then filtered.

[0088] After the granular carbon adsorption in Comparative Examples 1 to 3 was replaced with powdered activated carbon decolorization adsorption, the applicant found that when the amount of powdered activated carbon was 0.1%, agglomeration began to occur in 77 days. When the amount of powdered activated carbon was increased to 1%, the agglomeration time was significantly improved, but it still began to agglomerate in 161 days. The whole process is time-consuming, and the activated carbon is powder, which is very harmful to the working environment. Increasing the amount of powdered activated carbon will produce a large amount of waste activated carbon, which will eventually become solid waste, making post-processing difficult.

[0089] Comparative Example 4

[0090] The only difference between Comparative Example 4 and Example 1 is that the step of granular carbon adsorption is removed.

[0091] Light transmittance: According to the method of the national standard GB / T 23532-2009 for xylose, a spectrophotometer with a wavelength of 380nm~850nm is used. The sugar solution to be tested is placed in a 0.5cm cuvette, and the zero point is adjusted with water as a blank. The light transmittance is measured at a wavelength of 420nm. The spectrophotometer is blanked with water and the zero point is adjusted with a 0.5cm cuvette at a wavelength of 420nm.

[0092] Sugar concentration: Use a handheld sugar meter to test. The specific method is as follows: open the cover, drop the liquid to be tested on the prism, close the cover, and make sure that the liquid covers the entire surface without bubbles. Aim the prism at the light source, and you can see the scale in the eyepiece. Just read the reading, and use distilled water as a blank sample to adjust to zero.

[0093] Xylose content: HPLC test, according to the national standard of xylose GB / T 23532-2009.

[0094] Flow rate: The multiple of the volume of the granular carbon column flowing through per hour is expressed as BV / h.

[0095] Xylose moisture: Take 1g sample and test it using a rapid moisture meter at 105℃.

[0096] 100-mesh sieve pass rate: The dried xylose is sieved with a 100-mesh standard sieve, and the mass of the xylose that passes through the sieve is the percentage of the total sample mass. The higher the 100-mesh sieve pass rate, the greater the proportion of fine particles.

[0097] Filtration time of finished xylitol: 200g of finished xylitol is dissolved in water to 1000ml. When filtered with a 0.45um microporous membrane, the time it takes for 1000ml of xylitol solution to be completely filtered. The shorter the filtration time, the higher the cleanliness of the xylitol and the less likely it is to clump.

[0098] Water activity: HD-3A intelligent water activity measuring instrument is used. The detection method is as follows: weigh 5g of the sample to be tested, spread it flat on the sample tray, place it in the sensor, set the detection time to 15min, click the confirmation button, the instrument will automatically detect, and automatically read the value after the time is up. Each sample is measured 3 times to get the average value.

[0099] Table 1 ; .

[0100] As shown in Table 1, the transmittance of the sugar solution after adsorption by granular carbon has the following characteristics at different values:

[0101] From Examples 3-5 and 7-9, it can be seen that for sugar solutions with a transmittance of 90.0% to 95.0% and a crystallization raw material chromaticity of ≤50, the time to pass through a 0.45um filter membrane is shortened from the original 20 minutes to less than 5 minutes, the xylose centrifugation time is shortened by more than half, and the number of centrifugal washings is shortened from 2 to 3 times to 1 time, which greatly improves production efficiency. After centrifugation, the moisture content of xylose is greatly reduced, the moisture content of dried xylose is reduced to <0.1%, the pass rate of 100 mesh sieve is <30%, and no agglomeration occurs after 392 days (13 months). Within this transmittance range, the product quality is significantly improved, the data fluctuation is small, and it is conducive to stable production.

[0102] It can be seen from Examples 1-2 that when the chromaticity of the crystallization raw material is less than 50 and the transmittance is greater than 95%, the filtration time and centrifugation time are significantly shortened, but the 100-mesh sieve pass rate is greater than 30%, and agglomerates appear at 175 days.

[0103] It can be seen from Example 13 that when the transmittance is greater than 95% and the chromaticity of the crystallization raw material is greater than 50, although the filtration time and centrifugation time are shortened, and the 100-mesh sieve pass rate is greater than 30%, agglomeration occurs at 70 days.

[0104] As can be seen from Example 6, for a sugar solution with a transmittance of less than 90%, the chromaticity of the crystallization raw material is less than 50, the membrane filtration time and the centrifugation time are both shorter than those without granular carbon adsorption, but the 100-mesh sieve pass rate is greater than 30%, the particles are relatively small, and agglomeration occurs within 77 days. In addition, as the transmittance decreases, the chromaticity increases, the centrifugation time is prolonged, the number of washings increases, the 100-mesh sieve pass rate increases, and the agglomeration time is shortened.

[0105] As can be seen from Example 12, for sugar solution with a transmittance of <90%, the chromaticity of the crystallization raw material is >50, the filtration time and centrifugation time are shorter than those without granular carbon adsorption, but the 100-mesh sieve pass rate is >30%, the particles are relatively small, and agglomeration occurs within 42 days. And as the transmittance decreases, the chromaticity increases, the centrifugation time is prolonged, the number of washings increases, the 100-mesh sieve pass rate gradually increases, and the time for agglomeration to occur is shortened.

[0106] From Comparative Example 4, it can be seen that the sugar solution that has not been adsorbed by granular carbon has a light transmittance of 74.1%, a chromaticity of the crystallization raw material of 150, a long filtration time, and a difficult centrifugation of the sugar paste, which is manifested by a long centrifugation time, a large number of washing times, a high moisture content of centrifuged xylose, and a large drying energy consumption; the particles are fine, which is manifested by a 100-mesh sieve pass rate of >70%. The final product began to clump after 35 days of storage.

[0107] It can be seen from Examples 14-17 that if the flow rate is adjusted to 0.5 BV / h, the requirements of 90% to 95% transmittance and chromaticity ≤ 50 can be achieved, but if the flow rate is too slow, the production efficiency and capacity will decrease; when the flow rate is greater than 3 BV / h, the transmittance can also reach 93.0%, but the chromaticity is greater than 50, indicating that the adsorption is not thorough enough, and the final product will clump after 161 days.

[0108] In summary, adding a granular carbon adsorption step after the secondary ion exchange and before crystallization, controlling the transmittance to 90%-95%, and controlling the chromaticity of the concentrated crystalline raw material to ≤50 can make the particles of the final product larger, the 100-mesh sieve pass rate to <30%, and the anti-caking period to more than 13 months.

[0109] Preparation of xylitol

[0110] The difference between Examples 18-21 and Comparative Examples 5-7 is only the different sources of xylose, as shown in Table 2.

[0111] The specific method of using xylose to produce xylitol is as follows:

[0112] Sugaring: Dissolve xylose to 50% sugar concentration, transfer into the reactor, and add 10% Raney nickel catalyst.

[0113] Hydrogenation: Maintain the hydrogen pressure in the reactor at 5.5~6.0MPa and the temperature at 100℃~120℃ for 2h.

[0114] Sedimentation filtration: After the reaction stops, the catalyst and the hydrogenation liquid are fully separated by sedimentation, and the hydrogenation liquid is released from above the catalyst. The hydrogenation liquid is filtered and then goes to the next process.

[0115] Decolorization: Add 1‰ activated carbon to the hydrogenated liquid, stir at 50℃~60℃ for 30min for decolorization, and obtain the xylitol decolorized liquid after filtration.

[0116] Ion exchange: The decolorizing solution passes through a cation exchange column and an anion exchange column in sequence to remove the remaining metal ions and obtain xylitol decolorizing solution.

[0117] Concentration: After the xylitol ion solution is concentrated to the point where crystals form, feed is added while the concentration is in progress. When the total mass of the material reaches the capacity of the crystallization kettle, the feeding is stopped.

[0118] Crystallization: The concentrated massecuite is discharged into the crystallization kettle and cooled at a rate of 1°C / h until the massecuite becomes viscous and the stirring current suddenly increases, and then the material is discharged and centrifuged.

[0119] Centrifugal drying: Put the crystallized sugar paste into the centrifuge and start centrifugation. When no mother liquor is secreted, start deionized water spray washing. Stop centrifugation when the crystals turn white. After centrifugation, the xylitol is dried in a fluidized bed to obtain a xylitol product. The indicators meet the requirements of GB1886.234-2016. Take 500g of the package and store it in the sample cabinet. Observe its agglomeration every 7 days.

[0120] Table 2

[0121]

[0122] As shown in Table 2, when the xylose produced by the method of the present application is used to produce xylitol, the water activity of the xylitol product is significantly reduced, and the product membrane filtration time is shortened to less than 4 minutes, indicating that the cleanliness of the xylitol crystals is very good. The reduction in water activity and the improvement in cleanliness are both conducive to improving the fluidity of the xylitol product and extending the agglomeration cycle of the product. Compared with Comparative Examples 5-7, the agglomeration cycle of xylitol is increased from 28 days to 420 days, which greatly extends the shelf life of the product and is beneficial to customer use.

[0123] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the patent application attached hereto.

Claims

1. A method for producing xylose, comprising the following steps: Preparation of decolorized sugar solution: corn cobs are sequentially subjected to impurity removal, hydrolysis, neutralization filtration, first ion exchange, first concentration, and activated carbon decolorization to obtain decolorized sugar solution; Preparation of the decolorized sugar solution: subjecting the decolorized sugar solution to a second ion exchange to obtain a decolorized solution, wherein the decolorized solution has a xylose content greater than or equal to 70%, an electrical conductivity less than or equal to 100 us / cm, and a light transmittance greater than or equal to 70%; Preparation of effluent: subjecting the ionized liquid to granular carbon adsorption at a certain flow rate to obtain an effluent, wherein the effluent has a light transmittance of 90% to 99%; Preparation of concentrated sugar solution: concentrating the effluent for a second time to obtain concentrated sugar solution, wherein the chromaticity of the concentrated sugar solution is ≤50; Preparation of crystallization raw material: the concentrated sugar solution is filtered and concentrated for the third time to obtain crystallization raw material.

2. The production method according to claim 1, wherein The light transmittance of the effluent is 90% to 95%.

3. The production method according to claim 1, wherein The production method of xylose also includes the following steps: Cooling crystallization: xylose powder is added to the crystallization raw material as a seed crystal, and three stages of cooling crystallization are carried out in sequence; Preparation of wet xylose: The crystallized raw material after cooling and crystallization is grown at 25℃~30℃ for 5h~24h, and wet xylose is obtained after centrifugation; Preparation of xylose: The wet xylose is dried to obtain xylose.

4. The production method according to claim 3, wherein: The moisture content of the wet xylose is less than 1.5%; and / or, The moisture content in the xylose is less than 0.3%.

5. The production method according to claim 1 or 3, wherein: The sugar concentration of the concentrated sugar solution is 60% to 65%; and / or, The crystallization raw material sugar concentration is 80% to 85%; and / or, In the preparation of the decolorized sugar solution, the sugar concentration of the decolorized sugar solution is 20% to 30%.

6. The production method according to claim 1 or 3, wherein: In the preparation of the effluent, the flow rate is 0.5~4BV / h.

7. The production method according to claim 6, wherein: In the preparation of the effluent, the flow rate is 1~3BV / h.

8. The production method according to claim 3, wherein: In the preparation of the crystallization raw material, the temperature of the third concentration is lower than 75°C.

9. The production method according to claim 3, wherein: In the cooling crystallization, the three stages of cooling crystallization are as follows: the first stage is cooled to 70-60°C at a cooling rate of 0.3-0.6°C / h, the second stage is cooled to 55-45°C at a cooling rate of 0.75-1.2°C / h, and the third stage is cooled to 25-35°C at a cooling rate of 1.2-1.7°C / h; or, The mesh size of xylose powder is 80 mesh to 100 mesh.

10. The production method according to claim 1, wherein: In the preparation of the crystallization raw material, a 0.45 um filter membrane was used for filtration.

11. Use of xylose prepared by the method according to any one of claims 1 to 10 in the preparation of xylitol.

12. Xylitol, which is prepared using xylose according to any one of claims 1 to 10.

13. A method for preparing xylitol using xylose prepared by the method according to any one of claims 1 to 10, comprising the following steps: The xylose is subjected to saccharification, hydrogenation reaction, filtration, decolorization, ion exchange, concentration, crystallization and centrifugal drying.

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