Device and method for preparing xylose by pretreating wood fibers through electrothermal coupling dilute acid

Abstract

The invention discloses a device and a method for preparing xylose by pretreating wood fibers through electrothermal coupling dilute acid, and belongs to the technical field of biomass resource utilization. The device comprises an electric heating reaction unit, a time-varying magnetic field in a magnetic core in the electric heating reaction unit serves as an excitation source to spontaneously induce an electric effect and a heat effect on reaction feed liquid in a reaction tube, and electric heating coprocessing is completed. The method comprises the following steps: mixing a wood fiber raw material with a dilute acid solution, and then carrying out electric heating pretreatment by using the device disclosed by the invention; a large amount of hemicelluloses and a small amount of lignin in the wood fibers can be removed through electrothermal coupling dilute acid pretreatment. The energy loss of traditional hydrothermal treatment is reduced, the wood fibers are pretreated by means of the electric effect, the pretreatment temperature is reduced, and the requirement for equipment or devices in the high-temperature and high-pressure environment is avoided.

Description

Technical Field

[0001] The present invention particularly relates to a device and method for preparing xylose by pretreating wood fiber through electric heating and dilute acid coupling, and belongs to the technical field of biomass resource utilization. Background Art

[0002] With the increase in global energy demand and the overuse of fossil energy, it is urgent to seek a sustainable alternative fuel. As a biomass resource, lignocellulosic biomass has an annual global production of about 180 billion tons, mainly composed of 5-30% lignin, 20-35% hemicellulose and 30-50% cellulose, including forest waste, straw, etc., and is widely used in bio-based materials, medicine, chemical industry, bioenergy and other fields. Lignocellulosic biomass is one of the most important applicable energy sources after fossil energy such as coal, oil and natural gas, and is considered the fourth largest energy source in the world. Due to its abundance, sustainability and minimal impact on land use change, lignocellulosic biomass has great potential to replace fossil energy. Due to the lack of economic and environmentally friendly industrial methods to treat these large amounts of waste, most of them are rudely buried and incinerated. Therefore, it is necessary and urgent to rationally and efficiently utilize lignocellulosic biomass resources through necessary pretreatment and enzymatic hydrolysis steps.

[0003] The purpose of pretreatment is to eliminate the compact and complex structure of lignocellulose. The presence of hemicellulose, cellulose and lignin and their structural changes may have different effects on cellulose enzymatic hydrolysis, such as the crystallinity index and depolymerization of cellulose, enzyme accessibility, content and structural characteristics of hemicellulose and lignin, etc. Acid pretreatment is considered to be one of the most promising pretreatment methods in the industrial field of biomass resource utilization. Acid pretreatment can improve the accessibility of cellulose by dissolving hemicellulose and obtain more hemicellulose decomposition monomers (xylose) and digestible cellulose. In addition, acid pretreatment can also increase the crystallinity of cellulose by removing amorphous components (most of the hemicellulose and a small amount of acid-soluble lignin), change the ultrastructure of lignocellulose, and enhance the accessibility of enzymes to exposed cellulose.

[0004] However, most of the existing acid pretreatment technologies are implemented under high temperature and pressurized environments, which places higher requirements and safety on traditional hydrothermal treatment equipment; secondly, cellulose monomers (glucose) and hemicellulose monomers (xylose) will further degrade into inhibitors such as 5-hydroxymethylfurfural and furfural under acidic and high temperature conditions; in addition, most of the high temperature and pressurized environments must be completed with the assistance of reactors, which makes it difficult to solve the problem of industrial-grade large-scale pretreatment. For example, CN 109097502B discloses a method for preparing polysaccharides by pretreating wood fiber with oxalic acid, which can be recycled. Corn cobs are pretreated with oxalic acid solution at a pretreatment temperature of 120-160°C by means of a hydrothermal reactor; CN 104328225 B discloses a method for extracting wood cellulose using a conjugate acid-base pair as a medium. A pretreatment system composed of a conjugate acid-base pair buffer solution and a biomass raw material is continuously hydrolyzed at a reactor temperature of 100-200°C; CN 105780565 A discloses a method for pretreating wood cellulose raw materials with dilute acid steam explosion, which is pretreated at 105-145°C by means of a steam explosion device. The above-mentioned pretreatment technologies and methods are all mainstream technologies at present, but they have the following problems: (1) The pretreatment temperature is too high, which easily leads to the formation of inhibitors and affects the subsequent saccharification and fermentation; (2) It is difficult for traditional hydrothermal treatment equipment to achieve a pressurized high-temperature environment, and it needs to be completed with the help of a reactor or a reactor; (3) It is difficult to achieve large-scale processing, which limits the industrialization process. Summary of the invention

[0005] The main purpose of the present invention is to provide a device and method for pretreating wood fiber and preparing xylose by electrothermal coupling with dilute acid, thereby overcoming the shortcomings of the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] On one hand, the present invention provides a device for pretreating wood fiber and preparing xylose by electrothermal coupling with dilute acid, the device comprising an electrothermal reaction unit 100, a pumping device 200, a stirring device 300, a power supply device 400, and a cooling device 500;

[0008] The electrothermal reaction unit 100 is composed of reaction tubes 101-102, a magnetic core 103, a water cooling plate 104 and an excitation coil 105;

[0009] The magnetic core 103 is a ring-shaped plate-shaped magnetic conductive material with a hole in the middle; the water-cooling plate 104 is a ring-shaped plate-shaped metal material with a hole in the middle, which is placed alternately with the magnetic core; the outer edge of the water-cooling plate 104 is embedded with cooling pipes 201-202 for cooling liquid circulation;

[0010] The water cooling plate 104 is connected to the cooling device 500 through the cooling pipes 201-202; the cooling device 500 is used to cool the coolant in the cooling pipes 201-202;

[0011] The reaction tubes 101-102 pass through the middle holes of the magnetic core 103 and the water-cooling plate 104 and are wound around the magnetic core and the water-cooling plate; the reaction tube inlet end 101 is located at the bottom end of the electrothermal reaction unit and is connected to the pumping device 200; the reaction tube outlet end 102 is located at the top end of the electrothermal reaction unit and is connected to the stirring device 300 through a pipeline;

[0012] The excitation coil 105 is wound around the magnetic core 103 and connected to a power supply device 400; the power supply device 400 is used to provide an excitation voltage, so that the magnetic core 103 generates a time-varying magnetic field as an excitation source, and spontaneously induces an induced voltage and an induced current inside the reaction tubes 101-102;

[0013] The stirring device 300 is connected to the pumping device 200 through a pipeline, and the pipeline of the pumping device contacts the bottom of the container in the stirring device to ensure the pumping of the solution.

[0014] Furthermore, the material of the magnetic core 103 is amorphous nanocrystalline soft magnetic material.

[0015] Furthermore, the length L1 of the magnetic core 103 is 30-100 cm, the width W1 is 15-50 cm, the height H is 3-8 cm, the distance l1 from the middle hole to the width is 5-20 cm, and the distance w1 from the middle hole to the length is 5-20 cm.

[0016] Furthermore, the diameter of the reaction tubes 101-102 ranges from 10 mm to 50 mm.

[0017] Furthermore, the reaction tubes 101-102 are acid- and alkali-resistant glass or silicone tubes.

[0018] The device provided by the present invention is used in the field of wood fiber separation.

[0019] Another aspect of the present invention provides a method for pretreating wood fiber by electrothermal coupling with dilute acid and preparing xylose, wherein the method is carried out using the above-mentioned device for separating all components of wood fiber and improving the efficiency of enzymatic saccharification;

[0020] The method specifically comprises the following steps:

[0021] (1) washing the wood fiber raw material, then immersing it in an organic solvent for decolorization, and then drying and crushing it for later use;

[0022] (2) mixing the crushed wood fiber raw material with the dilute acid solution, placing the mixture in the stirring device, starting the stirring to mix, and after the mixture is evenly mixed to obtain a mixed solution, starting the pumping device to send the mixed solution into the reaction tube, and starting the power supply device and the cooling device to react;

[0023] (3) After the reaction in step (2) is completed, the reaction liquid is subjected to solid-liquid separation, the solid is washed to be electrically neutral, and then dried; the obtained pre-treated liquid is hydrolyzed, purified and separated to obtain crude xylose solids.

[0024] Furthermore, the wood fiber raw material in step (1) includes straw and sawdust.

[0025] Furthermore, the straw includes wheat straw and corn straw.

[0026] Furthermore, the wood chips include poplar wood chips, eucalyptus wood chips, bagasse and bamboo powder.

[0027] Furthermore, the organic solvent in step (1) includes ethanol.

[0028] Furthermore, the mesh size of the pulverization in step (1) is 30 to 80 meshes.

[0029] Furthermore, the dilute acid solution in step (2) includes one or more of dilute sulfuric acid and dilute hydrochloric acid.

[0030] Furthermore, the concentration of the dilute acid solution in step (2) is 0.5%-3%.

[0031] Furthermore, in step (2), the mass volume ratio of the crushed wood fiber raw material to the dilute acid solution is 1 g: 10-50 mL.

[0032] Furthermore, in step (2), the reaction temperature is 80-100° C. and the treatment time is 3-7 h.

[0033] Furthermore, the parameters of the power supply device in step (2) are set to a voltage of 100-800V, a current of 2-10A, and a power of 0.2-8KW.

[0034] Furthermore, in step (2), the ratio of the voltage set by the power supply device to the diameter of the reaction tubes 101-102 is 200-250V:10mm.

[0035] Furthermore, after the power supply device in step (2) is turned on, the magnetic field strength of the magnetic core is 0.5-2T.

[0036] Furthermore, the hydrolysis conditions in step (3) are a temperature of 110-130° C. and a time of 0.5 to 2 h.

[0037] Compared with the prior art, the beneficial effects of the present invention include:

[0038] The present invention provides a new device, in which the electric thermal reaction unit uses induction heat generation, which avoids the energy consumption of medium heat transfer in the traditional hydrothermal treatment process, greatly improves the thermal energy utilization rate, reduces the traditional hydrothermal pretreatment temperature, controls the pretreatment temperature within 100°C, and avoids the requirements for equipment or devices in high temperature and high pressure environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 The present invention is a schematic diagram of the overall structure of a device for pretreating wood fiber and preparing xylose by electrothermal coupling with dilute acid, provided in a typical embodiment of the present invention; the diagram includes: an electrothermal reaction unit (100), a pumping device (200), a stirring device (300), a power supply device (400), and a cooling device (500).

[0041] Figure 2 The invention discloses an electrothermal reaction unit in a device for pretreating wood fiber with dilute acid and preparing xylose, provided in a typical embodiment of the present invention, and its top view, magnetic core, and water-cooled plate; reaction tubes (101-102), magnetic cores (103), water-cooled plates (104), excitation coils (105), and condensing water pipes (201-202).

[0042] Figure 3 The upper left is the effect of the electrothermal pretreatment and hydrothermal pretreatment provided in Example 1 of the present invention and Comparative Example 1 on the content of each component in the wood fiber. Figure 3 The upper right shows the cellulose retention rate and the removal rates of hemicellulose and lignin. Figure 3 The following is a comparison chart of the concentrations of various monosaccharides.

[0043] Figure 4 The upper left is the effect of the electrothermal pretreatment and hydrothermal pretreatment provided in Example 2 of the present invention and Comparative Example 2 on the content of each component in the wood fiber. Figure 4 The upper right shows the cellulose retention rate and the removal rates of hemicellulose and lignin. Figure 3 The following is a comparison chart of the concentrations of various monosaccharides.

[0044] Figure 5 The upper left is the effect of the electrothermal pretreatment and hydrothermal pretreatment provided in Example 3 of the present invention and Comparative Example 3 on the content of each component in the wood fiber. Figure 5The upper right shows the cellulose retention rate and the removal rates of hemicellulose and lignin. Figure 3 The following is a comparison chart of the concentrations of various monosaccharides. DETAILED DESCRIPTION

[0045] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0046] The technical solution, its implementation process and principles, etc. will be further explained below in conjunction with the accompanying drawings and specific implementation cases. Unless otherwise specified, the power supply device, pumping device, electrothermal reaction unit, stirring device, cooling device, magnetic core, water-cooled plate, etc. used in the present invention are all known to those skilled in the art and can be purchased commercially. The specific product models and structures are not limited here.

[0047] Source of raw materials

[0048] Cellulase (400u / mg), filter paper enzyme activity (250FPU / g), Shanghai Yuanye Biotechnology Co., Ltd.; wheat straw, Donghai County, Lianyungang City, Jiangsu Province.

[0049] Example 1

[0050] This embodiment provides a device for separating all components of wood fiber and improving the efficiency of enzymatic saccharification, as shown in the attached Figure 1 As shown in , its composition includes an electrothermal reaction unit 100, a pumping device 200, a stirring device 300, a power supply device 400, and a cooling device 500.

[0051] In the device, the electrothermal reaction unit 100, as shown in the attached Figure 2 As shown in , its composition includes reaction tubes 101-102, magnetic cores 103, water cooling plates 104 and excitation coils 105. The electrothermal reaction unit 100 is used to generate a time-varying magnetic field as an excitation source, and spontaneously induces an induced voltage and an induced current inside the reaction tubes 101-102. The induced voltage acts on the reaction liquid to produce an electrical effect, and the induced current acts on the reaction liquid to produce a thermal effect, completing the electrothermal coordinated reaction; the pumping device 200 is used to transport the liquid from the stirring device 300 into the reaction tubes 101-102 for electrothermal coordinated reaction; the stirring device 300 is used to stir the liquid to maintain the uniformity of the reaction liquid, and the stirring device 300 is connected to the pumping device 200 through a pipeline, and the pipeline of the pumping device contacts the bottom of the container in the stirring device to ensure the pumping of the solution; the power supply device 400 provides an excitation voltage to the magnetic core 103 through the excitation coil 105; the cooling device 500 is used to cool the cooling water in the cooling tubes 201-202.

[0052] In the electrothermal reaction unit 100, the magnetic core 103 is a rectangular annular plate-shaped magnetic conductive material with a hole in the middle; the water-cooled plate 104 is a rectangular annular plate-shaped metal material with a hole in the middle, which is placed alternately with the magnetic core 103, so as to facilitate the heat energy generated by eddy current loss and hysteresis loss in the magnetic core to be dissipated through the water-cooled plate; cooling pipes 201-202 are embedded in the four sides of the water-cooled plate 104 for cooling water circulation; the water-cooled plate 104 is connected to the cooling device 500 through the cooling pipes 201-202; the reaction tubes 101-102 The middle hole passing through the magnetic core 103 and the water-cooling plate 104 is wrapped around the magnetic core 103 and the water-cooling plate 104; the reaction tube inlet end 101 is located at the bottom end of the electrothermal reaction unit 100, and is connected to the pumping device 200 through a pipeline, so that the pipeline is filled with liquid during transportation; the reaction tube outlet end 102 is located at the top end of the electrothermal reaction unit 100, and is connected to the stirring device 300 through a pipeline, and the liquid is circulated to the stirring device 300; the excitation coil 105 is wrapped around the magnetic core 103 and connected to the power supply device 400.

[0053] The method of using the device is as follows: first, the stirring device 300 is turned on to maintain the uniformity of the reaction liquid, and then the pumping device 200 is started to inject the reaction liquid into the reaction tube 101-102. When the liquid begins to flow out of the reaction tube outlet 102, the reaction tube is filled with liquid. At this time, the power supply device 400 is turned on, and an excitation voltage is provided to the magnetic core 103 through the excitation coil 105. The time-varying magnetic field inside the magnetic core 103 is used as an excitation source to spontaneously induce an induced voltage and an induced current inside the reaction tube 101-102, and an electrothermal coordinated reaction begins. Then, the cooling device 500 is started to circulate cooling water to cool the device. The number of water-cooled plates 104 and magnetic cores 103 can be adjusted according to actual applications.

[0054] Example 2

[0055] The present invention provides Figure 1 and Figure 2 The device shown is for pretreating wood fiber with dilute acid by electrothermal coupling and preparing xylose, adopting a reaction tube with a diameter of 10 mm, the material of the reaction tube is silica gel; adopting a magnetic core with L1 of 30 cm, l1 of 6 cm, W1 of 18 cm, w1 of 6 cm, and H of 3 cm; the size of the water-cooling plate adopted is equivalent to the size of the magnetic core; the number of magnetic cores in the electrothermal reaction unit adopted is 3, the number of water-cooling plates is 2, and the water-cooling plate is placed between the two magnetic cores to dissipate heat.

[0056] Operation process: 25g of crushed wheat straw powder is mixed with 1L of dilute sulfuric acid solution (solution concentration is 1%) to obtain a mixed liquid, and then the mixed liquid is placed in a stirring device. The mixed liquid enters the electrothermal reaction unit through a pumping device for electrothermal cycle treatment (the treatment temperature is 90°C, the treatment time is 5h; the voltage provided by the power supply device is 200V, the current is 5A, and the power is 1KW). The treated mixed liquid is separated into solid and liquid, and the solid residue (wood fiber) is washed to electrical neutrality and dried with air to prepare for analysis of its components; the supernatant is hydrolyzed (121°C, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0057] The cellulose content of untreated wheat straw is 33.3%, the hemicellulose content is 22.7%, the lignin content is 20.6%, and the ash content is 2.4%; after electrothermal coupled dilute acid pretreatment, the cellulose content of wheat straw is analyzed to be 44.3%, the hemicellulose content is 11.6%, the lignin content is 29.7%, and the ash content is 5.1%; after calculation, the cellulose retention rate in wheat straw after pretreatment is 83.5%, the hemicellulose removal rate is 70.2%, and the lignin removal rate is 6.8%; the analysis shows that the glucose concentration in the supernatant is 0.6 g / L, the xylose concentration is 3.9 g / L, and the arabinose concentration is 0.9 g / L.

[0058] Example 3

[0059] The present invention provides Figure 1 and Figure 2 The device shown is for pretreating wood fiber with dilute acid by electrothermal coupling and preparing xylose, adopting a reaction tube with a diameter of 10 mm, the material of the reaction tube is silica gel; adopting a magnetic core with L1 of 30 cm, l1 of 6 cm, W1 of 18 cm, w1 of 6 cm, and H of 3 cm; the size of the water-cooling plate adopted is equivalent to the size of the magnetic core; the number of magnetic cores in the electrothermal reaction unit adopted is 3, the number of water-cooling plates is 2, and the water-cooling plate is placed between the two magnetic cores to dissipate heat.

[0060] Operation process: 25g of crushed wheat straw powder is mixed with 1L of dilute sulfuric acid solution (solution concentration is 2%) to obtain a mixed liquid, and then the mixed liquid is placed in a stirring device. The mixed liquid enters the electrothermal reaction unit through a pumping device for electrothermal cycle treatment (the treatment temperature is 90°C, the treatment time is 3h; the voltage provided by the power supply device is 200V, the current is 5A, and the power is 1KW). The treated mixed liquid is separated into solid and liquid, and the solid residue (wood fiber) is washed to electrical neutrality and dried with air to prepare for analysis of its components; the supernatant is hydrolyzed (121°C, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0061] The cellulose content of untreated wheat straw is 33.3%, the hemicellulose content is 22.7%, the lignin content is 20.6%, and the ash content is 2.4%; after electrothermal coupled dilute acid pretreatment, the cellulose content of wheat straw is analyzed to be 48.9%, the hemicellulose content is 10.4%, the lignin content is 31.35%, and the ash content is 5.4%; after calculation, the cellulose retention rate of wheat straw after pretreatment is 80.1%, the hemicellulose removal rate is 75.6%, and the lignin removal rate is 7.1%; the analysis shows that the glucose concentration in the supernatant is 0.75g / L, the xylose concentration is 4.1g / L, and the arabinose concentration is 1.0g / L.

[0062] Example 4

[0063] The present invention provides Figure 1 and Figure 2 The device shown is for pretreating wood fiber with dilute acid and preparing xylose by electrothermal coupling. The device adopts a reaction tube with a diameter of 20 mm, and the material of the reaction tube is silica gel. The magnetic cores with L1 of 60 cm, l1 of 15 cm, W1 of 30 cm, w1 of 10 cm, and H of 5 cm are adopted. The size of the water-cooling plate adopted is equivalent to the size of the magnetic core. The number of magnetic cores in the electrothermal reaction unit adopted is 8, and the number of water-cooling plates is 7, and the water-cooling plate is placed between the two magnetic cores to dissipate heat.

[0064] Operation process: 500g of crushed wheat straw powder is mixed with 10L of dilute sulfuric acid solution (solution concentration is 1%) to obtain a mixed liquid, and then the mixed liquid is placed in a stirring device. The mixed liquid enters the electrothermal reaction unit through a pumping device for electrothermal cycle treatment (the treatment temperature is 90°C, the treatment time is 5h; the voltage provided by the power supply device is 500V, the current is 10A, and the power is 5KW). The treated mixed liquid is separated into solid and liquid, and the solid residue (wood fiber) is washed to electrical neutrality and dried with air to prepare for analysis of its various components; the supernatant is hydrolyzed (121°C, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0065] The cellulose content of untreated wheat straw is 33.3%, the hemicellulose content is 22.7%, the lignin content is 20.6%, and the ash content is 2.4%; after electrothermal coupled dilute acid pretreatment, the cellulose content of wheat straw is 44.6%, the hemicellulose content is 10.9%, the lignin content is 29.8%, and the ash content is 5.3%; the cellulose retention rate in wheat straw after pretreatment is calculated to be 84.5%, the hemicellulose removal rate is 71.8%, and the lignin removal rate is 7.1%; the analysis shows that the glucose concentration in the supernatant is 1.3 g / L, the xylose concentration is 8.7 g / L, and the arabinose concentration is 2.3 g / L.

[0066] Comparative Example 1

[0067] The specific implementation method is the same as Example 2, except that: Comparative Example 1 directly uses a hydrothermal treatment device and a laboratory-level circulating water bath for operation. The specific operation steps are as follows:

[0068] Operation process: 25g of crushed wheat straw powder is mixed with 1L of dilute sulfuric acid solution (solution concentration is 1%) to obtain a mixed liquid, and then the mixed liquid is placed in a glass bottle and mixed evenly on a magnetic stirring device, and the mixed liquid is pumped into a circulating water bath cavity by a peristaltic pump for hydrothermal circulation treatment (the treatment temperature is 90°C and the treatment time is 5h), and the treated mixed liquid is subjected to solid-liquid separation, and the solid residue (wood fiber) is washed to electrical neutrality and dried by air to prepare for analysis of its various components; the supernatant is hydrolyzed (121°C, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0069] The cellulose content of untreated wheat straw is 33.3%, the hemicellulose content is 22.7%, the lignin content is 20.6%, and the ash content is 2.4%; after hydrothermal pretreatment, analysis shows that the cellulose content of wheat straw is 43.2%, the hemicellulose content is 15.6%, the lignin content is 26.8%, and the ash content is 4.1%; after calculation, the cellulose retention rate in wheat straw after pretreatment is 85.9%, the hemicellulose removal rate is 56.7%, and the lignin removal rate is 8.6%; analysis shows that the glucose concentration in the supernatant is 0.5g / L, the xylose concentration is 2.1g / L, and the arabinose concentration is 0.7g / L.

[0070] Comparative Example 2

[0071] The specific implementation method is the same as Example 3, except that: Comparative Example 2 directly uses a hydrothermal treatment device and a laboratory-level circulating water bath for operation. The specific operation steps are as follows:

[0072] Operation process: 25g of crushed wheat straw powder is mixed with 1L of dilute sulfuric acid solution (concentration of 2%) to obtain a mixed liquid, and then the mixed liquid is placed in a glass bottle and mixed evenly on a magnetic stirring device. The mixed liquid is pumped into a circulating water bath cavity by a peristaltic pump for hydrothermal circulation treatment (the treatment temperature is 90°C and the treatment time is 3h). The treated mixed liquid is subjected to solid-liquid separation, and the solid residue (wood fiber) is washed to electrical neutrality and dried by air to prepare for analysis of its components; the supernatant is hydrolyzed (121°C, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0073] The cellulose content of untreated wheat straw is 33.3%, the hemicellulose content is 22.7%, the lignin content is 20.6%, and the ash content is 2.4%; after hydrothermal pretreatment, analysis shows that the cellulose content of wheat straw is 44.6%, the hemicellulose content is 12.7%, the lignin content is 28.1%, and the ash content is 4.7%; after calculation, the cellulose retention rate in wheat straw after pretreatment is 88.9%, the hemicellulose removal rate is 67.4%, and the lignin removal rate is 10.8%; analysis shows that the glucose concentration in the supernatant is 0.55 g / L, the xylose concentration is 2.95 g / L, and the arabinose concentration is 0.84 g / L.

[0074] Comparative Example 3

[0075] The specific implementation method is the same as Example 4, except that: Comparative Example 3 directly uses a hydrothermal treatment device and an industrial-grade reactor for operation. The specific operation steps are as follows:

[0076] Operation process: 500g of crushed wheat straw powder is mixed with 10L of dilute sulfuric acid solution (solution concentration is 1%) to obtain a mixed liquid, then the mixed liquid is placed in a glass bottle and mixed evenly on a magnetic stirring device, the mixed liquid is pumped into a circulating water bath cavity by a peristaltic pump for hydrothermal circulation treatment (the treatment temperature is 90°C and the treatment time is 5h), the treated mixed liquid is subjected to solid-liquid separation, the solid residue (wood fiber) is washed to electrical neutrality, and air-dried for analysis of its components; the supernatant is hydrolyzed (121°C, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0077] The cellulose content of untreated wheat straw is 33.3%, the hemicellulose content is 22.7%, the lignin content is 20.6%, and the ash content is 2.4%; after hydrothermal pretreatment, analysis shows that the cellulose content of wheat straw is 43.6%, the hemicellulose content is 14.9%, the lignin content is 26.1%, and the ash content is 4.3%; after calculation, the cellulose retention rate in wheat straw after pretreatment is 86.4%, the hemicellulose removal rate is 58.9%, and the lignin removal rate is 9.2%; analysis shows that the glucose concentration in the supernatant is 1.0 g / L, the xylose concentration is 4.8 g / L, and the arabinose concentration is 1.5 g / L.

[0078]

[0079] Table 1 Test data of Examples 2 to 4 and Comparative Examples 1 to 3

[0080] In summary, compared with comparative examples 1, 2 and 3, respectively, the electrothermal pretreatment of Examples 2, 3 and 4 has better removal effect on hemicellulose in wood fiber than the hydrothermal pretreatment, and the xylose concentration in the hydrolyzate obtained by the electrothermal pretreatment is significantly higher than that in the hydrothermal pretreatment group; the hemicellulose content in the wood fiber and the xylose concentration in the pretreated hydrolyzate are targeted, which proves the advantages of the device and method of the present invention for electrothermal coupled dilute acid pretreatment of wood fiber and preparation of xylose; compared with traditional hydrothermal treatment, the device and method of the present invention also improve energy utilization.

[0081] Comparative Example 4

[0082] This comparative example is a comparison of Example 2. The same device as Example 2 is used, and only the voltage in operation is adjusted from 200V to 400V, and other operations and parameters remain unchanged.

[0083] Table 2 Pretreatment results of Example 2 and Comparative Example 4

[0084]

[0085] According to Table 2, it can be found that when the voltage is adjusted to 400 V, the response of the thermal effect and the electrical effect is enhanced, and the hemicellulose removal rate in the wheat straw is further improved, indicating that in the device of the present invention, the increase in voltage can more effectively separate hemicellulose.

[0086] Comparative Example 5

[0087] This comparative example is a comparison with Example 2. The same device as Example 2 is used, and only the voltage in operation is adjusted from 200V to 100V, and other operations and parameters remain unchanged.

[0088] Table 3 Pretreatment results of Example 2 and Comparative Example 5

[0089]

[0090] According to Table 3, it can be found that when the voltage is adjusted to 100V, the pretreatment temperature decreases and the electrical effect weakens, and the hemicellulose removal rate in the wheat straw is greatly reduced, indicating that the voltage selected in the present invention cannot be too small, and the voltage selection range is above 200V.

[0091] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for separating all components of wood fiber, characterized in that: The device is composed of an electrothermal reaction unit, a pumping device, a stirring device, a power supply device, and a cooling device; The electrothermal reaction unit is composed of a reaction tube, a magnetic core, a water cooling plate and an excitation coil; The magnetic core is a ring-shaped plate-shaped magnetic conductive material with a hole in the middle; the water-cooling plate is a ring-shaped plate-shaped metal material with a hole in the middle, which is placed alternately with the magnetic core; a cooling pipe is embedded in the outer edge of the water-cooling plate for the circulation of cooling liquid; The water-cooled plate is connected to the cooling device through a cooling pipe; the cooling device is used for cooling the coolant in the cooling pipe; The reaction tube passes through the middle hole of the magnetic core and the water-cooling plate and is wound around the magnetic core and the water-cooling plate; the inlet end of the reaction tube is located at the bottom end of the electrothermal reaction unit and is connected to the pumping device; the outlet end of the reaction tube is located at the top end of the electrothermal reaction unit and is connected to the stirring device through a pipeline; The excitation coil is wound around the magnetic core and connected to a power supply device; the power supply device is used to provide an excitation voltage, so that the magnetic core generates a time-varying magnetic field as an excitation source, and spontaneously induces an induced voltage and an induced current inside the reaction tube; The stirring device is connected to the pumping device through a pipeline, and the pipeline of the pumping device contacts the bottom of the container in the stirring device to ensure the pumping of the solution.

2. The device according to claim 1, characterized in that The material of the magnetic core is amorphous nanocrystalline soft magnetic material; the length L1 of the magnetic core is 30-100cm, the width W1 is 15-50cm, the height H is 3-8cm, the distance l1 from the middle hole to the width is 5-20cm, and the distance w1 from the middle hole to the length is 5-20cm.

3. The device according to claim 1, characterized in that The reaction tube is an acid- and alkali-resistant glass or silicone tube.

4. Use of the device according to any one of claims 1 to 3 in the field of wood fiber separation.

5. A method for pretreating wood fiber by electrothermal coupling with dilute acid and preparing xylose, characterized in that: The method is carried out using the device according to any one of claims 1 to 3; The method specifically comprises the following steps: (1) washing the wood fiber raw material, then immersing it in an organic solvent for decolorization, and then drying and crushing it for later use; (2) mixing the crushed wood fiber raw material with the dilute acid solution, placing the mixture in the stirring device, starting the stirring to mix, and after the mixture is evenly mixed to obtain a mixed solution, starting the pumping device to send the mixed solution into the reaction tube, and starting the power supply device and the cooling device to react; (3) After the reaction in step (2) is completed, the reaction liquid is subjected to solid-liquid separation, the solid is washed to be electrically neutral, and then dried; the obtained pre-treated liquid is hydrolyzed, purified and separated to obtain crude xylose solids.

6. The method according to claim 5, characterized in that The wood fiber raw materials in step (1) include straw and wood chips; the straw includes wheat straw and corn straw; the wood chips include poplar sawdust, eucalyptus sawdust, bagasse and bamboo powder.

7. The method according to claim 5, characterized in that In step (2), the dilute acid solution includes one or more of dilute sulfuric acid and dilute hydrochloric acid; the concentration of the dilute acid solution is 0.5%-3%.

8. The method according to claim 5, characterized in that The mass volume ratio of the crushed wood fiber raw material and the dilute acid solution in step (2) is 1g:10-50mL.

9. The method according to claim 5, characterized in that In step (2), the reaction temperature is 80-100° C., and the processing time is 3-7 hours; the parameters of the power supply device are set to a voltage of 100-800 V, a current of 2-10 A, and a power of 0.2-8 KW; and the ratio of the voltage set by the power supply device to the tube diameter of the reaction tube is 200-250 V:10 mm.

10. The method according to claim 5, characterized in that After the power supply device is turned on in step (2), the magnetic field strength of the magnetic core is 0.5-2T.

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