阅读说明：本技术 一种利用木糖二蒸液生产木糖醇及联产l-阿拉伯糖的方法 (Method for producing xylitol and co-producing L-arabinose by using xylose secondary distillation liquid ) 是由 曹玉华 孙鲁 王关斌 黄伟红 刘海朋 杜瑞锋 史晓委 袁其朋 朱道辰 于 2020-12-29 设计创作，主要内容包括：公开了一种利用木糖二蒸液生产木糖醇及联产L-阿拉伯糖的生产方法,包括步骤：(1)取木糖二蒸液；(2)对木糖二蒸液进行顺序式模拟移动床色谱分离去除阿拉伯糖,提取液主要成分为木糖和葡萄糖,残液主要成分为阿拉伯糖；(3)将上述提取液和残液分别进行脱色、离子交换提纯；(4)将提纯后的提取液浓缩、结晶、离心、烘干得到木糖晶体；(5)将提纯后的残液浓缩、结晶、离心、烘干得到阿拉伯糖晶体；(6)将所得木糖晶体加水溶解,进行木糖加氢,得到木糖加氢液；(7)对木糖加氢液进行阳-阴离子交换,将交换液浓缩、结晶、离心、烘干,得到木糖醇晶体。该方法提高了木糖液的加氢效率,进而大幅提高了木糖醇的结晶收率。(Discloses a method for producing xylitol and co-producing L-arabinose by using xylose secondary distilled liquid, which comprises the following steps: (1) taking second xylose steam; (2) performing sequential simulated moving bed chromatographic separation on the xylose secondary distillate to remove arabinose, wherein the main components of the extract are xylose and glucose, and the main component of the raffinate is arabinose; (3) decolorizing the extractive solution and residual solution, and purifying by ion exchange; (4) concentrating, crystallizing, centrifuging and drying the purified extracting solution to obtain xylose crystals; (5) concentrating, crystallizing, centrifuging and drying the purified residual liquid to obtain arabinose crystals; (6) dissolving the obtained xylose crystals in water, and carrying out xylose hydrogenation to obtain xylose hydrogenation liquid; (7) and (3) carrying out cation-anion exchange on the xylose hydrogenation solution, concentrating, crystallizing, centrifuging and drying the exchange solution to obtain xylitol crystals. The method improves the hydrogenation efficiency of the xylose liquid, and further greatly improves the crystallization yield of the xylitol.)

1. A production method for producing xylitol and co-producing L-arabinose by using xylose secondary distilled liquid is characterized by comprising the following steps:

(1) taking a xylose secondary distillation liquid with the area percentage content of 75-81% detected by liquid chromatography, wherein the mass concentration of the xylose secondary distillation liquid is 40-45%;

(2) performing sequential simulated moving bed chromatographic separation on the xylose secondary distillate to remove arabinose, wherein the main components of the extract are xylose and glucose, and the main component of the raffinate is arabinose;

(3) decolorizing the extractive solution and residual solution, and purifying by ion exchange;

(4) concentrating the purified extracting solution to the mass concentration of 75-78%, placing the extracting solution into a crystallizer for gradient cooling crystallization, centrifuging and drying to obtain xylose crystals;

(5) concentrating the purified residual liquid to the mass concentration of 65-75%, placing the concentrated residual liquid into a crystallizer for gradient cooling crystallization, centrifuging and drying to obtain arabinose crystals;

(6) adding water to the xylose crystals obtained in the step (4) to dissolve the xylose crystals to a mass concentration of 40-50%, and carrying out xylose hydrogenation to obtain xylose hydrogenation liquid;

(7) and (3) carrying out cation-anion exchange on the xylose hydrogenation solution, concentrating the exchange solution to a mass concentration of 78-82%, carrying out gradient cooling crystallization, centrifuging, and drying to obtain a xylitol crystal.

2. The production process according to claim 1, wherein in the step (2), arabinose is removed by sequential simulated moving bed chromatography under the separation conditions of: the feeding flow rate is 52-55ml/min, the detergent flow rate is 75-85ml/min, the extracting solution flow rate is 80-82ml/min, the residual liquid flow rate is 45-55ml/min, the circulating flow rate is 75-85ml/min, the circulating time is 840-870s, and the separation temperature is 63-67 ℃.

3. The production process according to claim 1, wherein in the step (3), the decolorization is carried out by activated carbon in an amount of 1 to 3% by mass based on the extract or raffinate.

4. The production process according to claim 1, wherein in the step (3), the ion exchange is carried out by using a cation-anion exchange resin.

5. The production process according to claim 1, wherein in the step (4) or (5), the concentration is vacuum concentration evaporation using a rotary evaporator.

6. The production method according to claim 1, wherein in the step (4), the crystallization condition is that the initial temperature is 78-82 ℃, the temperature is reduced to 68-72 ℃ at the rate of 0.8-1.2 ℃/h, the temperature is maintained for 1.5-2.5h, and then the temperature is reduced to 35-40 ℃ for centrifugation.

7. The production method according to claim 1, wherein in the step (5), the crystallization conditions are: the initial temperature is 78-82 ℃, the temperature is reduced at the speed of 0.8-1.2 ℃/h, the temperature is reduced to 30-35 ℃ and the centrifugation is carried out.

8. The production process according to claim 1, wherein in the step (6), the hydrogenation conditions are: the concentration of xylose liquid is as follows: 40-45 mass%, temperature 125-: 7-8, the hydrogenation pressure is 8-10MPa, the stirring speed is 450-470rpm, and the catalyst is a nickel catalyst.

9. The production method according to claim 1, wherein in the step (7), the crystallization conditions are: the initial temperature is 78-82 ℃, the temperature is reduced to 65-70 ℃ at the speed of 0.8-1.2 ℃/h, xylitol seed crystals are added, the temperature is kept for 1.5-2.5h, and then the temperature is continuously reduced to 40-45 ℃ for centrifugation.

10. The production process according to claim 1 or 9, wherein the xylitol seed crystals are added by uniformly mixing the seed crystals with alcohol so as to better disperse the xylitol particles in the xylitol solution.

Technical Field

The invention belongs to the technical field of functional sugar, and particularly relates to a production method of xylitol.

Background

As is well known, xylitol is produced by two processes, chemical and fermentation.

The fermentation method is to utilize xylose reductase in microbial cells to reduce xylose into xylitol, and although the biological fermentation reaction conditions are mild and the operation is relatively safe, the one-time investment of equipment is large and the production period is long.

The chemical process of producing xylitol is to prepare xylose as material with corn cob containing hemicellulose as material and to produce xylitol through the subsequent hydrogenation of xylose liquid.

The existing production process has low production yield of xylitol, which is generally about 50%, so a new xylitol production method is urgently needed to solve the technical problems.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for producing xylitol and co-producing L-arabinose by using xylose two-distilled liquid.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a production method for producing xylitol and co-producing L-arabinose by using xylose secondary distilled liquid is characterized by comprising the following steps:

(1) taking a xylose secondary distillation liquid with the area percentage content of 75-81% detected by liquid chromatography, wherein the mass concentration of the xylose secondary distillation liquid is 40-45%;

(2) performing sequential simulated moving bed chromatographic separation on the xylose secondary distillate to remove arabinose, wherein the main components of the extract are xylose and glucose, and the main component of the raffinate is arabinose;

(3) decolorizing the extractive solution and residual solution, and purifying by ion exchange;

(4) concentrating the purified extracting solution to the mass concentration of 75-78%, placing the extracting solution into a crystallizer for gradient cooling crystallization, centrifuging and drying to obtain xylose crystals;

(5) concentrating the purified residual liquid to the mass concentration of 65-75%, placing the concentrated residual liquid into a crystallizer for gradient cooling crystallization, centrifuging and drying to obtain L-arabinose crystals;

(6) adding water to the xylose crystals obtained in the step (4) to dissolve the xylose crystals to a mass concentration of 40-50%, and carrying out xylose hydrogenation to obtain xylose hydrogenation liquid;

(7) and (3) carrying out cation-anion exchange on the xylose hydrogenation solution, concentrating the exchange solution to a mass concentration of 78-82%, carrying out gradient cooling crystallization, centrifuging, and drying to obtain a xylitol crystal.

Wherein, in the step (1), the xylose secondary distillation liquid comprises xylose secondary distillation liquid prepared by hydrolyzing, purifying and concentrating corn cob, bagasse, straw and other raw materials or xylose secondary distillation liquid prepared by saccharifying, purifying and concentrating xylose raw materials;

wherein in the step (2), arabinose is removed by the sequential simulated moving bed chromatographic separation, and the separation conditions are as follows: the feed flow rate is 52-55ml/min (preferably 53.3ml/min), the detergent flow rate is 75-85ml/min (preferably 80ml/min), the extract flow rate is 80-82ml/min (preferably 81.3ml/min), the raffinate flow rate is 45-55ml/min (preferably 50ml/min), the circulation flow rate is 75-85ml/min (preferably 80ml/min), the circulation time is 840-870s, and the separation temperature is 63-67 deg.C (preferably 65 deg.C).

In the step (3), the decolorization is carried out by adopting activated carbon, the adding amount of the activated carbon is 1-3% of the mass of the sugar solution, the decolorization condition is that the temperature is 60-70 ℃, and the decolorization time is 30-40 min.

Wherein, in the step (3), the ion exchange is performed by using a cation-anion exchange resin.

In the step (4) or (5), the concentration is vacuum concentration evaporation by using a rotary evaporator.

Wherein, in the step (4), the crystallization condition is that the initial temperature is 78-82 ℃ (preferably 80 ℃), the temperature is reduced to 68-72 ℃ (preferably 70 ℃) at the speed of 0.8-1.2 ℃/h (preferably 1 ℃/h), the temperature is kept for 1.5-2.5h (preferably 2h), and then the temperature is reduced to 35-40 ℃ for centrifugation.

Wherein, in the step (5), the crystallization conditions are as follows: initial temperature is 78-82 deg.C (preferably 80 deg.C), cooling at 0.8-1.2 deg.C/h (preferably 1 deg.C/h), and centrifuging at 30-35 deg.C.

Wherein, in the step (6), the water is added with deionized water.

Wherein, in the step (6), the hydrogenation conditions are as follows: the concentration of xylose liquid is as follows: 40-45 mass%, temperature 125-: 7-8, the hydrogenation pressure is 8-10MPa (preferably 9MPa), the stirring speed is 450-470rpm (preferably 460rpm), and the catalyst is a nickel catalyst.

Wherein, in the step (7), the crystallization conditions are as follows: initial temperature is 78-82 deg.C (preferably 80 deg.C), cooling to 65-70 deg.C at 0.8-1.2 deg.C/h (preferably 1 deg.C/h), adding xylitol seed crystal (no less than 100 mesh), keeping the temperature for 1.5-2.5h (preferably 2h), cooling to 40-45 deg.C, and centrifuging.

Preferably, the seed crystal adding mode is as follows: uniformly mixing the seed crystal with a small amount of alcohol, and adding the seed crystal to enable xylitol particles to be better dispersed in a xylitol sugar solution;

preferably, the crystals are centrifuged and washed with a small amount of alcohol to further improve the yield and purity of the product.

The invention has the beneficial technical effects that:

according to the invention, firstly, the simulated moving bed is adopted to carry out chromatographic separation on the xylose liquid, and the arabinose in the xylose liquid is separated, so that the influence of the isomer arabinose on the xylose hydrogenation can be avoided in the hydrogenation process, the hydrogenation efficiency of the xylose liquid is improved, and the crystallization yield of the xylitol is greatly improved to about 60%.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

(1) Taking about 40 liters of xylose secondary distilled liquid with the area percentage content of 80.02 percent (the area percentage content is the same as below) detected by liquid chromatography, wherein the mass concentration of the xylose secondary distilled liquid is 42 percent;

(2) and (3) carrying out Sequential Simulated Moving Bed (SSMB) chromatographic separation on the xylose secondary distillate to remove arabinose, wherein the separation conditions are as follows: the system pressure is 0.2Mpa, the feed flow is 53.3ml/min, the detergent flow is 80ml/min, the extract flow is 81.3ml/min, the residual liquid flow is 50ml/min, the circulation flow is 80ml/min, the circulation time is 840s, the separation temperature is 65 ℃, about 52 liters of extraction mixed liquor with the mass concentration of 26 percent and the main components of xylose and glucose is obtained, and the xylose purity is 89.23 percent; about 35 liters of residual liquid with the mass concentration of 3 percent and the main component of arabinose is obtained, and the purity of the arabinose is 79.05 percent;

(3) adding activated carbon into the extractive solution and the residual solution respectively according to 1% of the dry matter of sugar solution, maintaining at 60 deg.C for 40min, decolorizing, and filtering to obtain decolorized solution, and performing ion exchange with cation exchange resin (001 × 7) -anion exchange resin (D301);

(4) concentrating the extract after ion exchange to 78% by mass concentration by using a rotary evaporator, placing the concentrate into a crystallizer for gradient cooling crystallization, starting cooling at 80 ℃, keeping the temperature for 2h for growing crystals when crystal grains appear at the cooling rate of 1 ℃/h, then continuously cooling at the rate of 1 ℃/h, centrifuging to about 35 ℃, and drying to obtain 7.55Kg of xylose crystals;

(5) concentrating the residual liquid after ion exchange to reach a mass concentration of 71% by using a rotary evaporator, and putting the residual liquid into a crystallizer for gradient cooling crystallization, wherein the crystallization conditions are as follows: the initial temperature is 80 ℃, the cooling rate is 1 ℃/h, the temperature is continuously reduced to 32 ℃, and 400g of arabinose crystals are obtained through centrifugation and drying;

(6) adding water to the xylose crystals obtained in the step (4) to dissolve the xylose crystals to 42% of mass concentration, and carrying out xylose hydrogenation under the following hydrogenation conditions: temperature 125 ℃, pressure 9.0MPa, pH: 7.5, catalyst: nickel catalyst to obtain xylose hydrogenated liquid with xylitol content of 97.51%;

(7) and (2) carrying out cation exchange resin (001 x 7) -anion exchange resin (D301) ion exchange on the xylose hydrogenation liquid, concentrating the exchange liquid to 78% of mass concentration, carrying out gradient cooling crystallization, carrying out initial temperature of 80 ℃, carrying out cooling rate of 1 ℃/h, adding xylitol seed crystals (not less than 100 meshes) when the temperature is reduced to 65 ℃, carrying out heat preservation for 2h, then continuously cooling to 40 ℃, centrifuging, and drying to obtain 4.56kg of xylitol crystals, wherein the yield of the xylitol crystals relative to the xylose hydrogenation raw material crystals reaches 60.4%.

Example 2:

(1) about 40 liters of xylose secondary distilled liquid with 81.09 percent of area percentage content (the area percentage content is the same as the following content) detected by liquid chromatography is taken, and the mass concentration of the xylose secondary distilled liquid is 41.5 percent;

(2) and (3) carrying out Sequential Simulated Moving Bed (SSMB) chromatographic separation on the xylose secondary distillate to remove arabinose, wherein the separation conditions are as follows: the system pressure is 0.2Mpa, the feed flow is 53.3ml/min, the detergent flow is 80ml/min, the extract flow is 81.3ml/min, the residual liquid flow is 50ml/min, the circulation flow is 80ml/min, the circulation time is 840s, and the separation temperature is 65 ℃, so that about 53.2 liters of extraction mixed liquor with the mass concentration of 26.2 percent and the main components of xylose and glucose is obtained, and the xylose purity is 89.51 percent; about 34.6 liters of raffinate with the mass concentration of 2.8 percent and the main component of arabinose is obtained, and the arabinose purity is 79.85 percent;

(3) adding active carbon into the extractive solution and the residual solution respectively according to 1% of the dry matter of sugar solution, maintaining at 60 deg.C for 40min, decolorizing, and filtering to obtain decolorized solution, and performing ion exchange with cation exchange resin (001 × 7) -anion exchange resin (D301);

(4) concentrating the extract after ion exchange to reach mass concentration of 79% by using a rotary evaporator, placing the extract into a crystallizer for gradient cooling crystallization, starting cooling at 80 ℃, keeping the temperature for 2h for growing crystals at the cooling rate of 1 ℃/h, then continuously cooling at the rate of 1 ℃/h, centrifuging to about 35 ℃, and drying to obtain 7.69Kg of xylose crystals;

(5) concentrating the residual liquid after ion exchange to reach mass concentration of 71.5% in a rotary evaporator, and performing gradient cooling crystallization in a crystallizer under the crystallization conditions: the initial temperature is 80 ℃, the cooling rate is 1 ℃/h, the temperature is continuously reduced to 35 ℃, and the arabinose crystal is obtained by centrifugation and drying;

(6) adding water to the xylose crystals obtained in the step (4) to dissolve the xylose crystals to 42% of mass concentration, and carrying out xylose hydrogenation under the following hydrogenation conditions: temperature 125 ℃, pressure 9.0MPa, pH: 7.5, catalyst: nickel catalyst to obtain xylose hydrogenated liquid with xylitol content of 97.80%;

(7) and (2) carrying out cation exchange resin (001 x 7) -anion exchange resin (D301) ion exchange on the xylose hydrogenation liquid, concentrating the exchange liquid to 80% of mass concentration, carrying out gradient cooling crystallization, carrying out initial temperature of 80 ℃, carrying out cooling rate of 1 ℃/h, adding xylitol seed crystals (more than or equal to 100 meshes) in an alcohol mixing and adding mode when the temperature is reduced to 65 ℃, carrying out heat preservation for 2h, then continuously cooling to 40 ℃, washing with a small amount of alcohol, centrifuging, and drying to obtain 4.76kg of xylitol crystals, wherein the yield of the xylitol crystals relative to the xylose hydrogenation raw material crystals reaches 61.9%.

Example 3:

(1) taking about 40 liters of xylose secondary distilled liquid with the area percentage content of 75.52 percent (the area percentage content is the same as below) detected by liquid chromatography, wherein the mass concentration of the xylose secondary distilled liquid is 42 percent;

(2) and (3) carrying out Sequential Simulated Moving Bed (SSMB) chromatographic separation on the xylose secondary distillate to remove arabinose, wherein the separation conditions are as follows: the system pressure is 0.2Mpa, the feeding flow is 53.3ml/min, the detergent flow is 80ml/min, the extracting solution flow is 81.3ml/min, the residual solution flow is 50ml/min, the circulating flow is 80ml/min, the circulating time is 870s, the separation temperature is 65 ℃, and about 51 liters of extracting mixed liquor with the mass concentration of 25.8 percent and the main components of xylose and glucose is obtained, and the purity of the xylose is 89.06 percent; about 37 liters of residual liquid with the mass concentration of 3.2 percent and the main component of arabinose is obtained, and the purity of the arabinose is 79.85 percent;

(3) adding active carbon into the extractive solution and the residual solution respectively according to 1% of the dry matter of sugar solution, maintaining at 60 deg.C for 40min, decolorizing, and filtering to obtain decolorized solution, and performing ion exchange with cation exchange resin (001 × 7) -anion exchange resin (D301);

(4) concentrating the extract after ion exchange to 78% by mass concentration by using a rotary evaporator, placing the concentrate into a crystallizer for gradient cooling crystallization, starting cooling at 80 ℃, keeping the temperature for 2h for growing crystals when crystal grains appear at the cooling rate of 1 ℃/h, then continuously cooling at the rate of 1 ℃/h, centrifuging to about 35 ℃, and drying to obtain 7.05Kg of xylose crystals;

(5) concentrating the residual liquid after ion exchange to reach a mass concentration of 71% by using a rotary evaporator, and putting the residual liquid into a crystallizer for gradient cooling crystallization, wherein the crystallization conditions are as follows: the initial temperature is 80 ℃, the cooling rate is 1 ℃/h, the temperature is continuously reduced to 30-35 ℃, and the arabinose crystals are obtained after centrifugation and drying;

(6) adding water to the xylose crystals obtained in the step (4) to dissolve the xylose crystals to 42% of mass concentration, and carrying out xylose hydrogenation under the following hydrogenation conditions: temperature 125 ℃, pressure 9.0MPa, pH: 7.5, catalyst: nickel catalyst to obtain xylose hydrogenated liquid with xylitol content of 96.89%;

(7) and (2) carrying out cation exchange resin (001 x 7) -anion exchange resin (D301) ion exchange on the xylose hydrogenation liquid, concentrating the exchange liquid to 78% of mass concentration, carrying out gradient cooling crystallization, cooling to 80 ℃ at an initial temperature at a cooling rate of 1 ℃/h, adding xylitol seed crystals (not less than 100 meshes) when the temperature is reduced to 65 ℃, preserving the temperature for 2h, then continuously cooling to 40 ℃, centrifuging, and drying to obtain 4.16kg of xylitol crystals, wherein the yield of the xylitol crystals relative to the xylose hydrogenation raw material crystals reaches 59.0%.

Comparative example 1: arabinose removal without Sequential Simulated Moving Bed (SSMB) chromatographic separation, otherwise same as in example 1

(1) Taking about 15 liters of xylose secondary distilled liquid with the area percentage content of 80.02 percent (the area percentage content is the same as below) detected by liquid chromatography, wherein the mass concentration of the xylose secondary distilled liquid is 42 percent;

(2) adding activated carbon into the xylose secondary distillation liquid according to 1% of the dry matter weight of the sugar liquid, preserving the heat at 60 ℃ for 40min, decoloring and filtering, and performing ion exchange on the decolored liquid through cation exchange resin (001 x 7) -anion exchange resin (D301);

(3) concentrating the sugar solution after ion exchange to a mass concentration of 78% by using a rotary evaporator, placing the sugar solution into a crystallizer for gradient cooling crystallization, starting cooling at 80 ℃, keeping the temperature for 2h for growing crystals after the temperature is reduced by 1 ℃/h, then continuously cooling at the speed of 1 ℃/h, centrifuging and drying the sugar solution until the temperature is about 35 ℃ and obtaining 2.47Kg of xylose crystals;

(4) adding water to the xylose crystals obtained in the step (3) to dissolve the xylose crystals to 42% of mass concentration, and carrying out xylose hydrogenation under the following hydrogenation conditions: temperature 80 ℃, pressure 9.0MPa, pH: 7.5, catalyst: nickel catalyst to obtain xylose hydrogenated liquid with xylitol content of 89.92%;

(5) and (2) carrying out cation exchange resin (001 x 7) -anion exchange resin (D301) ion exchange on the xylose hydrogenation liquid, concentrating the exchange liquid to 78% of mass concentration, carrying out gradient cooling crystallization, carrying out initial temperature of 80 ℃, carrying out cooling rate of 1 ℃/h, adding xylitol seed crystals (not less than 100 meshes) when the temperature is reduced to 65 ℃, carrying out heat preservation for 2h, then continuously cooling to 40 ℃, centrifuging, and drying to obtain 1.108kg of xylitol crystals, wherein the yield of the xylitol crystals relative to the xylose hydrogenation raw material crystals is 44.86%.

Comparative example 2: arabinose removal without Sequential Simulated Moving Bed (SSMB) chromatographic separation, remainder example 2

(1) Taking about 15 liters of xylose secondary distillation liquid with the area percentage content of 81.09 percent (the area percentage content is the same as below) detected by liquid chromatography, wherein the mass concentration of the xylose secondary distillation liquid is 41.5 percent;

(2) adding activated carbon into the xylose secondary distillation liquid according to 1% of the dry matter weight of the sugar liquid, preserving the heat at 60 ℃ for 40min, decoloring and filtering, and performing ion exchange on the decolored liquid through cation exchange resin (001 x 7) -anion exchange resin (D301);

(3) concentrating the sugar solution after ion exchange to a mass concentration of 77% by using a rotary evaporator, placing the sugar solution into a crystallizer for gradient cooling crystallization, starting cooling at 80 ℃, keeping the temperature for 2h for growing crystals at a cooling rate of 1 ℃/h after crystal grains appear, continuously cooling at a rate of 1 ℃/h, centrifuging and drying the sugar solution to about 35 ℃ to obtain 2.52Kg of xylose crystals;

(4) adding water to the xylose crystals obtained in the step (3) to dissolve the xylose crystals to 42% of mass concentration, and carrying out xylose hydrogenation under the following hydrogenation conditions: temperature 80 ℃, pressure 9.0MPa, pH: 7.5, catalyst: nickel catalyst to obtain xylose hydrogenated liquid with xylitol content of 90.02%;

(5) and (2) carrying out cation exchange resin (001 x 7) -anion exchange resin (D301) ion exchange on the xylose hydrogenation liquid, concentrating the exchange liquid to 80% of mass concentration, carrying out gradient cooling crystallization, carrying out initial temperature of 80 ℃, carrying out cooling rate of 1 ℃/h, adding xylitol seed crystals (more than or equal to 100 meshes) in an alcohol mixing and adding mode when the temperature is reduced to 65 ℃, carrying out heat preservation for 2h, then continuously cooling to 40 ℃, centrifuging, washing with a small amount of alcohol, centrifuging, and drying to obtain 1.160kg of xylitol crystals, wherein the yield of the xylitol crystals relative to the xylose hydrogenation raw material crystals is 46.03%.

Comparative example 3: arabinose removal without Sequential Simulated Moving Bed (SSMB) chromatographic separation, remainder example 3

(1) Taking about 15 liters of xylose secondary distillation liquid with the area percentage content of 75.52 percent (area percentage content, the same below) detected by liquid chromatography, wherein the mass concentration of the xylose secondary distillation liquid is 42 percent;

(2) adding activated carbon into the xylose secondary distillation liquid according to 1% of the dry matter weight of the sugar liquid, preserving the heat at 60 ℃ for 40min, decoloring and filtering, and performing ion exchange on the decolored liquid through cation exchange resin (001 x 7) -anion exchange resin (D301);

(3) concentrating the sugar solution after ion exchange to a mass concentration of 78% by using a rotary evaporator, placing the sugar solution into a crystallizer for gradient cooling crystallization, starting cooling at 80 ℃, keeping the temperature for 2h for growing crystals after the temperature is reduced by 1 ℃/h, then continuously cooling at the speed of 1 ℃/h, centrifuging and drying the sugar solution until the temperature is about 35 ℃ and obtaining 2.07Kg of xylose crystals;

(4) adding water to the xylose crystals obtained in the step (3) to dissolve the xylose crystals to 42% of mass concentration, and carrying out xylose hydrogenation under the following hydrogenation conditions: temperature 80 ℃, pressure 9.0MPa, pH: 7.5, catalyst: a nickel catalyst is used for obtaining xylose hydrogenation liquid with xylitol content of 89.99 percent;

(5) and (2) carrying out cation exchange resin (001 x 7) -anion exchange resin (D301) ion exchange on the xylose hydrogenation liquid, concentrating the exchange liquid to 78% of mass concentration, carrying out gradient cooling crystallization, carrying out initial temperature of 80 ℃, carrying out cooling rate of 1 ℃/h, adding xylitol seed crystals (not less than 100 meshes) when the temperature is reduced to 65 ℃, carrying out heat preservation for 2h, then continuously cooling to 40 ℃, centrifuging, and drying to obtain 0.91kg of xylitol crystals, wherein the yield of the xylitol crystals relative to the xylose hydrogenation raw material crystals is 43.98%.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.