阅读说明：本技术 一种三区带模拟移动床除盐以净化木糖水解液的方法 (Method for purifying xylose hydrolysate by desalting with three zones with simulated moving bed ) 是由 张军伟 袁苗新 贾彩敬 于 2020-07-08 设计创作，主要内容包括：本发明公开了一种三区带模拟移动床除盐以净化木糖水解液的方法,属于功能糖制取分离技术领域。本发明提供的方法以木糖水解液为对象,采用三区带模拟移动床色谱除去无机盐以净化木糖水解液,以去离子水为洗脱剂,工作温度50～70℃,以钠型或钙型强酸性阳离子树脂为色谱固定相,木糖水解液电导率大幅度降低,部分色泽物同时也被去除,糖组分保持较低损失率。本发明不仅能除去无机盐以净化木糖水解液,革新了离子交换除盐的方法,降低了酸碱消耗和工艺废水产生量,还将木糖生产工艺化繁为简,降低了后续浓缩成本和生产损耗,提高了生产效率。(The invention discloses a method for purifying xylose hydrolysate by desalting with a three-zone simulated moving bed, belonging to the technical field of functional sugar preparation and separation. The method provided by the invention takes the xylose hydrolysate as an object, adopts three-zone simulated moving bed chromatography to remove inorganic salt so as to purify the xylose hydrolysate, takes deionized water as an eluent, has the working temperature of 50-70 ℃, takes sodium type or calcium type strong acid cation resin as a chromatographic stationary phase, greatly reduces the conductivity of the xylose hydrolysate, removes partial color and luster substances simultaneously, and keeps a low loss rate of sugar components. The method can remove inorganic salt to purify xylose hydrolysate, innovate an ion exchange desalting method, reduce acid and alkali consumption and process wastewater generation amount, simplify xylose production process, reduce subsequent concentration cost and production loss, and improve production efficiency.)

1. A three-zone simulated moving bed chromatographic desalination process for purifying xylose hydrolysate, comprising the steps of:

(1) alkali neutralization and concentration of xylose hydrolysate: neutralizing the xylose hydrolysate with alkali liquor to pH 4.5-5.5, and filtering to remove solid impurities and insoluble matters to obtain xylose filtrate; performing rotary evaporation on the xylose filtrate, controlling the temperature at 60-75 ℃, and concentrating to obtain a sugar solution with the refractive concentration of 40-60% and the conductivity of 150000-250000 mu S/m, namely the raw material;

(2) three-zone simulated moving chromatography desalting: carrying out three-zone simulated moving bed chromatographic separation on the raw material obtained in the step (1) to remove inorganic salt; the three-zone simulated moving bed chromatography takes calcium type or sodium type strong acid cation resin as a stationary phase and deionized water as an eluent at the working temperature of 50-70 ℃; the three-zone simulated moving bed chromatogram consists of a zone I, a zone II and a zone III which are connected in series in sequence; each zone contains at least 1 chromatographic column; the zone I is an extraction zone and is positioned between an eluent inlet and an extracting solution outlet; the zone II is an enrichment zone and is positioned between an extracting solution outlet and a raw material inlet; the zone III is a separation zone and is positioned between a raw material inlet and a raffinate outlet; the extract contains a sugar component; the raffinate contains an inorganic salt component.

2. The method of claim 1, wherein the xylose hydrolysate is prepared by a method comprising: the agricultural and forestry wastes, namely corncobs, bagasse, straws, eucalyptus or birch, are hydrolyzed by 0.5-1.8% of dilute inorganic acid at the hydrolysis temperature of 105-125 ℃ under the working pressure of 0.1-0.18 MPa for 1.5-2 h.

3. The method according to claim 1, wherein the cross-linking agent of the stationary phase is polyene benzene, the cross-linking level is 6-15%, the calcium or sodium rate is more than 95%, and the particle size of the resin is 120-250 μm.

4. The method according to claim 1, wherein adjacent chromatographic columns are connected by a pipeline, and a one-way valve is arranged on the pipeline; the bed height-diameter ratio of the chromatographic column is as follows: 15: 1-25: 1.

5. The method as claimed in claim 1, wherein the pipelines before the raw material inlet and the eluent inlet are provided with flow meters, the pipelines after the extracting solution outlet and the raffinate outlet are provided with conductivity meters, flow meters and flow regulating valves, and the flow meters, the conductivity meters, the flow meters and the flow regulating valves are respectively connected with a PLC program control system.

6. The method of claim 5, wherein the outside of the chromatography column is incubated with a concentric jacket by circulating water; and the PLC program controls the opening or closing of valves of an eluent inlet, a raw material liquid inlet, an extracting solution outlet and a raffinate outlet, the opening degree of a flow regulating valve and the simulated reverse movement of the stationary phase.

7. The method according to claim 1, wherein the raw material and the deionized water are respectively flowed into the three-zone simulated moving bed chromatography through a raw material inlet and an eluent inlet, the raw material inlet, the extract outlet and the raffinate outlet are synchronously switched to the next sequential position along the flow direction of the eluent after the completion of the single cycle, and the sugar component and the inorganic salt component are flowed out from the extract outlet and the raffinate outlet, so that the inorganic salt in the raw material is continuously removed.

8. The method according to claim 1, wherein the flow rate of the eluent is 3-7 mL/min, the flow rate of the raw material is 2-4 mL/min, the flow rate of the extracting solution is 2.5-5 mL/min, and the flow rate of the raffinate is 1.8-3.5 mL/min; the time of the single period is 15-25 min.

Technical Field

The invention belongs to the technical field of functional sugar preparation and separation, and relates to a method for purifying xylose hydrolysate by desalting with a three-zone simulated moving bed.

Background

Carbohydrates are a major source of cellular energy and play an important role in the construction of cells, biosynthesis, and regulation of vital activities. The functional sugar with special effects as one of the saccharides has the effects of low calorie, providing nutrition, promoting improvement of human physiological functions and the like, is mainly represented by functional sugar alcohol, functional dietary fiber and functional oligosaccharide, is originally used in nutrition health care and food industry, and is currently used in non-food fields of chemical industry, pharmacy, energy, petroleum and the like.

At present, the primary xylose water solution is obtained mainly from agricultural and forestry waste products such as corncobs, straws, bagasse and the like through the catalytic hydrolysis of dilute inorganic acid, or a biological method or an enzymatic hydrolysis method, and functional sugars such as xylose, arabinose and the like are prepared through refining, concentration and crystallization, wherein the dilute inorganic acid hydrolysis method is the current mainstream method. However, no matter what kind of process is adopted in the existing production, the xylose hydrolysate can enter a crystallization unit to obtain a functional sugar crystallization product only after being refined and concentrated, so that the refining of the xylose hydrolysate is an important link in the production and preparation process of the xylose hydrolysate, and the production efficiency and the process economy are determined.

Industrially, inorganic salt ions generated by acid-base neutralization in xylose hydrolysis and dissolved out from agricultural and forestry waste acids are mainly removed by ion exchange, and the inorganic salt ions are removed in a stepwise ion exchange form (e.g., mixed ion exchange → anion exchange → cation exchange, or mixed ion exchange → cation exchange → anion exchange), as shown in fig. 1, and as shown in chinese patents (publication nos. CN102584907A, CN109503676A, CN109908977A, etc.), part of color and luster is additionally removed. However, each ion exchange requires consumption of a large amount of acid and base, generates a large amount of wastewater, and the process water consumption and wastewater treatment cost are high. For this purpose, the scholars or inventors reduce the consumption of acid and alkali and the generation of wastewater as shown in fig. 2 by forming a ring by connecting the ion exchange columns in stages end to end, setting functional compartments, and filling the corresponding functional compartments with anion or cation exchange resins, thereby removing inorganic salt ions from the sugar solution in a continuous mode, as disclosed in chinese patents (publication nos. CN209138051A, CN10714233A, CN209307258A, etc.). The continuous ion exchange method reduces the consumption of acid and alkali and the amount of process wastewater to a certain extent, but the continuous ion exchange system is too complex, and the demand of stationary phase resin is also large.

Further, the present inventors or the present inventors performed deionization purification by an electrodialysis method. Chinese patent (publication No. CN103409565A) discloses a method for electrodialysis deacidification and desalination after ultrafiltration impurity removal and primary decolorization, and the conductivity is controlled below 500 μm/cm. Chinese patent (publication No. CN205868022A) discloses a xylose desalting and concentrating device, which removes inorganic salt ions in xylose feed liquid by electrodialysis. Chinese patent publication No. CN102597253A discloses a method for extracting xylose from hydrolysate by electrodialysis direct recovery method, and the conductivity of xylose electrodialysis liquid is lower than 1000 muS/cm. Chinese patent (publication No. CN106187731A) discloses a method for preparing xylonic acid by one-step method of electrodialysis desalination and acid conversion, and the conductivity of the obtained product solution can be reduced to below 300 mu S/cm.

The chromatographic separation is based on the difference of the distribution coefficient, adsorption or affinity acting force of components in two phases of a mobile phase and a stationary phase, the components are redistributed and rebalanced for many times in the process of moving along with the mobile phase, and the components have retention time difference on the stationary phase to realize the separation. The chromatographic stationary phase resin has different adsorption coefficients to saccharides, inorganic ions and the like, and the retention time of each substance in a chromatographic system is different. The student or inventor has sought to use chromatography to separate the sugar component from the inorganic salt ion.

Chinese patent (publication No. CN107142337A) discloses a method for preparing xylose and arabinose by taking bagasse as a raw material, and a decoloring, deionization and separation mixing device is used for separating sugar components, color materials and inorganic salt ions. However, the apparatus used and the method steps described therein are cumbersome (seven substeps), couple together with inorganic salt ion removal and separation, do not allow for good ion removal and separation of sugar components, and suffer from excessive dilution of the solution. Chinese patent (publication No. CN106282427A) discloses a method for preparing xylose, and inorganic salt ions are removed by combining chromatographic desalting and ion exchange to refine xylose hydrolysate, but the process is complicated, and the chromatographic desalting method and the operation example are not given in the text. Chinese patent (publication No. CN107893132A) discloses a method and a device for producing xylose, wherein the method and the device are used for removing impurities, decoloring and removing electrolyte of xylose hydrolysate by combining chromatography and a nanofiltration membrane, and a technical scheme for implementing chromatographic separation is not given in the text.

Chinese patent (publication No. CN208087530A) discloses a deacidification and desalination device for xylose hydrolysate, which uses a four-zone simulated moving bed to deacidify and desalt; the four-zone simulated moving bed at least needs 4 chromatographic columns, and the number of control sites and matched valves is increased; the problem that inorganic salt ions with high migration speed in circulating liquid pollute other functional subareas occurs. Chinese patent (publication No. CN107936066A) discloses a sugar solution desalting and decoloring method for extracting stevioside by using stevioside, wherein a sequential simulated moving bed is used for carrying out primary desalting and decoloring on the sugar solution; as shown in fig. 3, the sequential simulated moving bed is divided into three sub-steps, one sub-step of separating a salt component and a pigment component, two sub-steps of separating steviol glycoside, and three sub-steps of a cycle. Chinese patent (publication No. CN109439807A) discloses a xylose production process, wherein xylose hydrolysate is subjected to flash evaporation, decoloration and filtration, secondary flash evaporation and membrane distillation concentration, and closed loop Novasep Varicol multi-column continuous system chromatography is used for separating acid and removing salt, and as shown in figure 4, the removal rate of the acid and the salt is about 95%; however, the method uses an asynchronous switching simulated moving bed device, the switching valve and the control system are more demanding, multiple sub-steps are needed to realize the variability of the number of chromatographic columns, and the operation steps and the system are relatively complex.

The three-zone simulated moving bed is a novel chromatographic device, which has three chromatographic functional zones, namely an I zone (extraction zone), a II zone (enrichment zone) and a III zone (separation zone), and can effectively avoid the pollution of reflux flow to the I zone in the operation process because no IV zone, namely no circulation zone, exists. The method for purifying the xylose hydrolysate by desalting by using three-zone simulated moving bed chromatography can overcome the defects of a conventional four-zone or sequential or Varicol multi-column continuous simulated moving bed and the like, can efficiently remove inorganic salt ions and partial color substances in the xylose hydrolysate, and improves the production efficiency of xylose.

Disclosure of Invention

In order to solve the problems, the invention provides a method for purifying xylose hydrolysate by three-zone simulated moving bed chromatographic desalination. By using the method, inorganic salt ions and partial color substances in the xylose hydrolysate can be continuously and efficiently removed.

The invention provides a method for purifying xylose hydrolysate by three-zone simulated moving bed chromatography desalination, which comprises the following steps:

(1) alkali neutralization and concentration of xylose hydrolysate: neutralizing the xylose hydrolysate with alkali liquor to pH 4.5-5.5, and filtering to remove solid impurities and insoluble matters to obtain xylose filtrate; performing rotary evaporation on the xylose filtrate, controlling the temperature at 60-75 ℃, and performing evaporation concentration to obtain a sugar solution with a refractive concentration of 40-60% (measured by an Abbe photometer) and an electric conductivity of 150000-250000 mu S/m, namely a raw material;

(2) three-zone simulated moving chromatography desalting: carrying out three-zone simulated moving bed chromatographic separation on the raw material obtained in the step (1) to remove inorganic salt; the three-zone simulated moving bed chromatography takes calcium type or sodium type strong acid cation exchange resin as a stationary phase and deionized water as an eluent at the working temperature of 50-70 ℃; the three-zone simulated moving bed chromatogram consists of a zone I, a zone II and a zone III which are connected in series in sequence; each zone contains at least 1 chromatographic column; the zone I is an extraction zone and is positioned between an eluent inlet and an extracting solution outlet; the zone II is an enrichment zone and is positioned between an extracting solution outlet and a raw material inlet; the zone III is a separation zone and is positioned between a raw material inlet and a raffinate outlet; the extract contains a sugar component; the raffinate contains an inorganic salt component.

Further, the preparation method of the xylose hydrolysate comprises the following steps: the agricultural and forestry wastes, namely corncobs, bagasse, straws, eucalyptus or birch, are hydrolyzed by 0.5-1.8% (m/m) of dilute inorganic acid at the hydrolysis temperature of 105-125 ℃, the working pressure of 0.1-0.18 MPa and the hydrolysis time of 1.5-2 h.

Furthermore, the cross-linking agent of the stationary phase is polyene benzene, the cross-linking level is 6-15%, the calcium or sodium rate is more than 95%, and the particle size of the resin is 120-250 μm.

Furthermore, adjacent chromatographic columns are connected through a pipeline, and a one-way valve is arranged on the pipeline; the bed height-diameter ratio of the chromatographic column is as follows: 15: 1-25: 1.

Furthermore, a flow meter is arranged on a pipeline in front of the raw material inlet and the eluent inlet, a conductivity meter, a flow meter and a flow regulating valve are arranged on a pipeline behind the extracting solution outlet and the raffinate outlet, and the flow meter, the conductivity meter, the flow meter and the flow regulating valve are respectively connected with a PLC program control system.

Further, the outside of the chromatographic column is insulated by circulating water through a concentric jacket; and the PLC program controls the opening or closing of valves of an eluent inlet, a raw material liquid inlet, an extracting solution outlet and a raffinate outlet, the opening degree of a flow regulating valve and the simulated reverse movement of the stationary phase.

Further, the raw material and the deionized water respectively flow into the three-zone simulated moving bed chromatography through the raw material inlet and the eluent inlet, after the operation of the eluent inlet, the raw material inlet, the extracting solution outlet and the raffinate outlet in a single period is finished, the eluent inlet, the raw material inlet, the extracting solution outlet and the raffinate outlet are synchronously switched to the next sequence position along the flowing direction of the eluent, the sugar component and the inorganic salt component flow out of the three-zone simulated moving bed chromatography through the extracting solution outlet and the raffinate outlet, and the inorganic salt in the raw material is continuously removed.

Further, the flow rate of the eluent is 3-7 mL/min, the flow rate of the raw material is 2-4 mL/min, the flow rate of the extracting solution is 2.5-5 mL/min, and the flow rate of the raffinate is 1.8-3.5 mL/min; the time of the single period is 15-25 min.

The working mechanism of the invention is as follows: the affinity of the calcium type or sodium type chromatographic fixation relative to the saccharides is higher than that of the inorganic salt ions, the retention time of the saccharides and the inorganic salt ions on the chromatographic column bed is different, and the inorganic salt ions flow out of the chromatographic column bed firstly and then flow out of the chromatographic column bed; xylose hydrolysate is continuously injected into the three-zone simulated moving bed chromatogram (three or more than three chromatographic columns form a three-zone open-loop simulated moving bed system), saccharides with long retention time are collected at an extract outlet, inorganic salt ions with short retention time are collected at a raffinate outlet, and then ports are switched along the flowing direction of eluent to simulate the movement of stationary phase, so that the inorganic salt ions in the xylose hydrolysate are continuously removed.

The invention has the beneficial effects that:

(1) the invention adopts open-loop three-zone simulated moving bed chromatography to remove salt, and overcomes the problem that inorganic salt ions in circulating liquid pollute sugar components in a first functional zone because no IV zone, namely no circulating zone, exists; the four ports (the eluent inlet, the raw material inlet, the extracting solution outlet and the raffinate outlet) are synchronously switched, so that the operation steps of a control system and a device are simplified, and inorganic salt and part of color and luster objects can be continuously and stably removed;

(2) the open-loop three-zone simulated moving bed chromatography adopted in the invention reduces the usage amount of the stationary phase resin and the number of chromatographic columns, reduces investment and loss, simultaneously innovates an ion exchange desalting method, reduces acid and alkali consumption and the generation amount of process wastewater, has simple process, high product yield and better energy-saving and emission-reducing effects;

(3) the conductivity of the continuously recovered sugar components is lower than 2500 mu S/m, the desalting rate is more than 90%, the light transmittance of the sugar solution is higher than 45%, the yield is more than 85%, the desalting effect is good, and the technical advantages are obvious.

Drawings

FIG. 1 is a schematic diagram of the ion exchange process for removing inorganic salt ions from xylose mother liquor. FIGS. 1a and 1b show the mixed ion exchange → anion exchange → cation exchange → inorganic ion removal mode, mixed ion exchange → cation exchange → anion exchange → inorganic ion removal mode, respectively.

FIG. 2 is a schematic diagram of the continuous ion exchange process for removing inorganic salt ions from the xylose mother liquor.

FIG. 3 is a schematic diagram of a sequencing batch simulated moving bed for removing inorganic salt ions from stevia sugar.

FIG. 4 is a schematic diagram of a Novasep Varicol multi-column continuous system for removing inorganic salt ions from xylose mother liquor.

FIG. 5 is a schematic diagram of three-zone simulated moving bed chromatographic desalination for purification of xylose hydrolysate in accordance with the present invention.

Detailed Description