Device and method for preparing xylose by electrothermal coupling dilute acid pretreatment of lignocellulose

Abstract

The application discloses a device and method for preparing xylose by electric-thermal coupling dilute acid pretreatment of wood fiber, and belongs to the technical field of biomass resource utilization. The device comprises an electric-thermal reaction unit, and a time-varying magnetic field in a magnetic core in the electric-thermal reaction unit is used as an excitation source to spontaneously induce electric effect and thermal effect on reaction liquid in the reaction tube, so that electric-thermal synergic treatment is completed. The method comprises the following steps: mixing wood fiber raw materials with a dilute acid solution, and then performing electric-thermal pretreatment by using the device; and the electric-thermal coupling dilute acid pretreatment can remove a large amount of hemicellulose and a small amount of lignin in the wood fiber. The application reduces energy loss of traditional hydrothermal treatment, pretreats the wood fiber by means of electric effect, reduces pretreatment temperature, and avoids requirements on equipment or devices under a high-temperature and high-pressure environment.

Description

TECHNICAL FIELD

[0001] The present application relates to a device and method for preparing xylose by electric heating coupling dilute acid pretreatment of lignocellulose, and belongs to the technical field of biomass resource utilization. BACKGROUND

[0002] With the increase of global energy demand and the overuse of fossil energy, it is urgent to seek a sustainable alternative fuel. Lignocellulose, as a kind of biomass resource, has a global annual output of about 180 billion tons, mainly composed of 5-30% lignin, 20-35% hemicellulose and 30-50% cellulose, including forest waste, straw and the like, and is widely used in the fields of bio-based materials, medicine, chemical industry, bioenergy and the like. Lignocellulosic biomass is one of the most important applicable energies after fossil energies such as coal, oil and natural gas, and is considered as the fourth largest energy 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 roughly buried and burned. Therefore, it is necessary and urgent to reasonably 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 and structural changes of hemicellulose, cellulose and lignin can have different effects on cellulose enzymolysis, such as crystallinity index and depolymerization of cellulose, accessibility of enzymes, content and structural properties of hemicellulose and lignin, etc. Acid pretreatment is considered to be one of the most promising pretreatment methods in the field of biomass resource utilization industry. 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 improve the crystallinity of cellulose by removing amorphous components (most of 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 realized in high-temperature and pressurized environment, which makes higher requirements and safety for traditional hydrothermal treatment devices; secondly, cellulose monomer (glucose) and hemicellulose monomer (xylose) will further degrade into 5-hydroxymethylfurfural and furfural and other inhibitors under acidic and high-temperature conditions; in addition, most of the high-temperature and pressurized environment are assisted by reaction kettles, which is difficult to solve the problem of industrial large-scale pretreatment. For example, CN 109097502B discloses a method for preparing polysaccharide by oxalic acid pretreatment of lignocellulose, which adopts oxalic acid solution to pretreat corncob in a hydrothermal reaction kettle at a pretreatment temperature of 120-160℃; CN 104328225B discloses a lignocellulose extraction method using a conjugate acid-base pair as a medium, which uses a pretreatment system composed of a conjugate acid-base pair buffer solution and biomass raw materials to continuously hydrolyze at a reactor temperature of 100-200℃; CN 105780565A discloses a dilute acid steam explosion pretreatment method for lignocellulose raw materials, which uses a steam explosion device to pretreat at 105-145℃. The above-mentioned pretreatment technologies and methods are currently the mainstream technologies, but there are the following problems: (1) the pretreatment temperature is too high, which easily leads to the generation of inhibitors and affects the subsequent saccharification and fermentation; (2) the traditional hydrothermal treatment equipment is difficult to realize the pressurized high-temperature environment, and needs to be assisted by a reactor or a reaction kettle; (3) it is difficult to realize large-scale treatment, which limits the industrialization process. SUMMARY

[0005] The main purpose of the present application is to provide a device and method for electrically heating and coupling dilute acid pretreatment of lignocellulose and preparation of xylose, thereby overcoming the deficiencies in the prior art.

[0006] To achieve the above-mentioned purposes, the technical scheme adopted by the present application comprises:

[0007] In one aspect, the present application provides a device for electrically heating and coupling dilute acid pretreatment of lignocellulose and preparation of xylose, which comprises an electric heating reaction unit 100, a pumping device 200, a stirring device 300, a power supply device 400 and a cooling device 500.

[0008] The electric heating reaction unit 100 comprises reaction tubes 101-102, a magnetic core 103, a water-cooled plate 104 and an excitation coil 105.

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

[0010] The water-cooled plate 104 is connected with the cooling device 500 through the cooling pipes 201-202; the cooling device 500 is used for cooling the cooling liquid in the pipes 201-202;

[0011] The reaction tube 101-102 is wound around the magnetic core and the water-cooled plate through the middle holes of the magnetic core 103 and the water-cooled plate 104; the reaction tube inlet end 101 is located at the bottom end of the electric heating reaction unit and is connected with the pumping device 200; the reaction tube outlet end 102 is located at the top end of the electric heating reaction unit and is connected with the stirring device 300 through pipes;

[0012] The excitation coil 105 is wound around the magnetic core 103 and is connected with the power supply device 400; the power supply device 400 is used for providing excitation voltage to make the magnetic core 103 generate time-varying magnetic field as an excitation source to spontaneously induce the formation of induced voltage and induced current in the reaction tube 101-102;

[0013] The stirring device 300 is connected with the pumping device 200 through pipes, and the pipes of the pumping device contact the bottom of the container of the stirring device to ensure the pumping of the solution.

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

[0015] Further, 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] Further, the pipe diameter of the reaction tube 101-102 ranges from 10 mm to 50 mm.

[0017] Further, the reaction tube 101-102 is acid and alkali resistant glass or silica gel tube.

[0018] The device provided by the application is applied in the field of lignocellulose separation.

[0019] The application further provides a method for electric heating coupling and dilute acid pretreatment of lignocellulose and preparation of xylose, which uses the above device for realizing lignocellulose full component separation and improving enzymatic saccharification efficiency.

[0020] The method specifically comprises the following steps:

[0021] (1) washing lignocellulose raw materials, then immersing them in an organic solvent for decolorization treatment, and then drying and crushing them for standby use;

[0022] (2) After the wood fiber raw material is crushed, it is mixed with a dilute acid solution, put into the stirring device, and mixed by starting the stirring. After the mixture is uniformly mixed, the mixture is sent into the reaction tube by starting the pumping device. The power supply device and the cooling device are started to perform the reaction.

[0023] (3) After the reaction of step (2) is completed, the reaction liquid is subjected to solid-liquid separation, and the solid is washed to electrical neutrality and dried. The obtained pretreated liquid is subjected to hydrolysis, purification and separation to obtain a crude xylose solid.

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

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

[0026] Further, the sawdust includes poplar sawdust, eucalyptus sawdust, sugarcane residue, and bamboo powder.

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

[0028] Further, the crushing size in step (1) is 30-80 mesh.

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

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

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

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

[0033] Further, the parameter settings of the power supply device in step (2) are voltage 100-800V, current 2-10A, and power 0.2-8KW.

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

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

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

[0037] Compared with the prior art, the present application has the following advantages:

[0038] The present application provides a new device, in which the electric heating reaction unit uses the induction heat generation mode, avoids the energy consumption of medium heat transfer in the traditional hydrothermal treatment process, greatly improves the heat energy utilization rate, and reduces the traditional hydrothermal pretreatment temperature. The pretreatment temperature is controlled within 100 DEG C, and the requirements for equipment or device under high temperature and high pressure environment are avoided. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0040] Figure 1 It is a whole structure schematic diagram of a device for electric heating coupling dilute acid pretreatment of wood fiber and preparation of xylose provided in a typical embodiment of the present application. In the figure, the electric heating reaction unit (100), the pumping device (200), the stirring device (300), the power supply device (400), and the cooling device (500).

[0041] Figure 2 It is a structure schematic diagram of the electric heating reaction unit and its top view, magnetic core, and water cooling plate in the device for electric heating coupling dilute acid pretreatment of wood fiber and preparation of xylose provided in a typical embodiment of the present application. The reaction tube (101-102), the magnetic core (103), the water cooling plate (104), the excitation coil (105), and the condensate water pipe (201-202).

[0042] Figure 3 The upper left is the content of each component in the wood fiber in the electric heating pretreatment and the hydrothermal pretreatment provided in the embodiment 1 and the comparative example 1 of the present application, Figure 3 The upper right is the retention rate of cellulose and the removal rate of hemicellulose and lignin, Figure 3 The lower is a comparison diagram of the concentration of each monosaccharide.

[0043] Figure 4 The upper left is the content of each component in the wood fiber in the electric heating pretreatment and the hydrothermal pretreatment provided in the embodiment 2 and the comparative example 2 of the present application, Figure 4 The upper right is the retention rate of cellulose and the removal rate of hemicellulose and lignin, Figure 3 The lower is a comparison diagram of the concentration of each monosaccharide.

[0044] Figure 5 The upper left is the content of each component in the wood fiber in the electric heating pretreatment and the hydrothermal pretreatment provided in the embodiment 3 and the comparative example 3 of the present application, Figure 5The top right side shows the retention rate of cellulose and the removal rates of hemicellulose and lignin. Figure 3 The following is a comparison chart of the concentrations of various monosaccharides. Detailed Implementation

[0045] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0046] The following will further explain the technical solution, its implementation process and principle in conjunction with the accompanying drawings and specific implementation examples. Unless otherwise specified, the power supply device, pumping device, electrothermal reaction unit, stirring device, cooling device, magnetic core, water-cooled plate and other components used in this invention are all known to those skilled in the art and can be obtained commercially. No specific product models or structures are 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 an apparatus for achieving complete separation of lignocellulose components and improving enzymatic hydrolysis and saccharification efficiency, as shown in the attached diagram. Figure 1 As shown, its components include 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 this device, the electrothermal reaction unit 100, as shown in the attached... Figure 2 As shown, the system comprises reaction tubes 101-102, a magnetic core 103, a water-cooled plate 104, and an excitation coil 105. The electrothermal reaction unit 100 generates a time-varying magnetic field as an excitation source, spontaneously inducing an induced voltage and current within 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 synergistic reaction. The pumping device 200 transports the liquid from the stirring device 300 into the reaction tubes 101-102 for the electrothermal synergistic reaction. The stirring device 300 stirs the liquid to maintain its uniformity. The stirring device 300 is connected to the pumping device 200 via a pipe, and the pipe 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 excitation voltage to the magnetic core 103 through the excitation coil 105. The cooling device 500 cools the cooling water in the cooling tubes 201-202.

[0052] In the electric heating reaction unit 100, the magnetic core 103 is a rectangular ring-shaped plate type magnetic conductive material with a hole in the middle; the water-cooled plate 104 is a rectangular ring-shaped plate type metal material with a hole in the middle, which is placed alternately with the magnetic core 103, so as to facilitate the dissipation of the heat energy generated by the eddy current loss and hysteresis loss in the magnetic core through the water-cooled plate; the four edges of the water-cooled plate 104 are embedded with cooling pipes 201-202 for cooling water flow; the water-cooled plate 104 is connected with the cooling device 500 through the cooling pipes 201-202; the reaction tube 101-102 is wound around the magnetic core 103 and the water-cooled plate 104 through the middle holes of the magnetic core 103 and the water-cooled plate 104; the reaction tube inlet end 101 is located at the bottom end of the electric heating reaction unit 100 and is connected with the pumping device 200 through a pipeline, so as to facilitate the filling of the pipeline with liquid material during transportation; the reaction tube outlet end 102 is located at the top end of the electric heating reaction unit 100 and is connected with the stirring device 300 through a pipeline, so as to circulate and transport the liquid material to the stirring device 300; the excitation coil 105 is wound around the magnetic core 103 and is connected with the power supply device 400.

[0053] The use method of the device is as follows: first, start the stirring device 300 to maintain the uniformity of the reaction liquid, then start the pumping device 200 to inject the reaction liquid into the reaction tube 101-102. When the reaction tube outlet end 102 starts to flow out the liquid material, the reaction tube is filled with the liquid material, at this time, the power supply device 400 is started, the excitation coil 105 provides excitation voltage to the magnetic core 103, the time-varying magnetic field in the magnetic core 103 acts as an excitation source to spontaneously induce an induced voltage and an induced current in the reaction tube 101-102, and the electric heating cooperative reaction is started. Then, the cooling device 500 is started to circulate cooling water to cool the device, and the number of water-cooled plates 104 and magnetic cores 103 can be adjusted according to actual application.

[0054] Example 2

[0055] The device for electric heating coupling and dilute acid pretreatment of wood fiber and preparation of xylose provided by the present application is shown in the device shown in Figure 1 and Figure 2 The reaction tube has a pipe diameter of 10 mm and is made of silica gel; the magnetic core has a length L1 of 30 cm, a width l1 of 6 cm, a width W1 of 18 cm, a width w1 of 6 cm, and a height H of 3 cm; the size of the water-cooled plate is similar to that of the magnetic core; in the electric heating reaction unit, the number of magnetic cores is 3, the number of water-cooled plates is 2, and the water-cooled plates are arranged between the two magnetic cores for heat dissipation.

[0056] Operation process: 25g of crushed wheat straw powder was mixed evenly with 1L of dilute sulfuric acid solution (solution concentration of 1%) to obtain a mixed liquid. The mixed liquid was then placed in a stirring device and pumped into an electrothermal reaction unit for electrothermal circulation treatment (the treatment temperature was 90℃, the treatment time was 5h; the power supply provided voltage was 200V, current was 5A, and power was 1KW). The treated mixed liquid was subjected to solid-liquid separation. The solid residue (wood fiber) was washed until electrically neutral and dried by forced air for analysis of its component composition. The supernatant was hydrolyzed (121℃, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0057] The untreated wheat straw contained 33.3% cellulose, 22.7% hemicellulose, 20.6% lignin, and 2.4% ash. After electrothermal coupling with dilute acid pretreatment, the cellulose content was 44.3%, hemicellulose was 11.6%, lignin was 29.7%, and ash was 5.1%. The calculated retention rate of cellulose in the pretreated wheat straw was 83.5%, the removal rate of hemicellulose was 70.2%, and the removal rate of lignin was 6.8%. The concentrations of glucose, xylose, and arabinose in the supernatant were 0.6 g / L, 3.9 g / L, and 0.9 g / L, respectively.

[0058] Example 3

[0059] Using the invention provided as follows Figure 1 and Figure 2 The apparatus shown is for electrothermally coupled dilute acid pretreatment of wood fibers to prepare xylose. It uses a reaction tube with a diameter of 10 mm and is made of silicone. It uses 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-cooled plate is similar to that of the magnetic core. The electrothermal reaction unit has 3 magnetic cores and 2 water-cooled plates, with the water-cooled plates placed between the two magnetic cores for heat dissipation.

[0060] Operation process: 25g of crushed wheat straw powder was mixed evenly with 1L of dilute sulfuric acid solution (solution concentration of 2%) to obtain a mixed liquid. The mixed liquid was then placed in a stirring device and pumped into an electrothermal reaction unit for electrothermal circulation treatment (the treatment temperature was 90℃, the treatment time was 3h; the power supply provided voltage was 200V, current was 5A, and power was 1KW). The treated mixed liquid was subjected to solid-liquid separation. The solid residue (wood fiber) was washed until electrically neutral and dried by forced air for analysis of its component composition. The supernatant was hydrolyzed (121℃, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0061] The untreated wheat straw contained 33.3% cellulose, 22.7% hemicellulose, 20.6% lignin, and 2.4% ash. After electrothermal coupling with dilute acid pretreatment, the cellulose content was 48.9%, hemicellulose was 10.4%, lignin was 31.35%, and ash was 5.4%. The calculated retention rate of cellulose in the pretreated wheat straw was 80.1%, the removal rate of hemicellulose was 75.6%, and the removal rate of lignin was 7.1%. The concentrations of glucose, xylose, and arabinose in the supernatant were 0.75 g / L, 4.1 g / L, and 1.0 g / L, respectively.

[0062] Example 4

[0063] Using the invention provided as follows Figure 1 and Figure 2 The apparatus shown is for electrothermally coupled dilute acid pretreatment of wood fibers to prepare xylose. It uses a reaction tube with a diameter of 20 mm and is made of silicone. It uses a magnetic core with L1 of 60 cm, l1 of 15 cm, W1 of 30 cm, w1 of 10 cm, and H of 5 cm. The size of the water-cooled plate is similar to that of the magnetic core. The electrothermal reaction unit has 8 magnetic cores and 7 water-cooled plates, with the water-cooled plates placed between the two magnetic cores for heat dissipation.

[0064] Operation process: 500g of crushed wheat straw powder was mixed evenly with 10L of dilute sulfuric acid solution (solution concentration of 1%) to obtain a mixed liquid. The mixed liquid was then placed in a stirring device and pumped into an electrothermal reaction unit for electrothermal circulation treatment (the treatment temperature was 90℃, the treatment time was 5h; the power supply provided voltage was 500V, current was 10A, and power was 5KW). The treated mixed liquid was subjected to solid-liquid separation. The solid residue (wood fiber) was washed until electrically neutral and dried by forced air for analysis of its component composition. The supernatant was hydrolyzed (121℃, 1h), rotary evaporated, extracted, and separated to obtain crude xylose solid.

[0065] The untreated wheat straw contained 33.3% cellulose, 22.7% hemicellulose, 20.6% lignin, and 2.4% ash. After electrothermal coupling with dilute acid pretreatment, the cellulose content was 44.6%, hemicellulose was 10.9%, lignin was 29.8%, and ash was 5.3%. The calculated retention rate of cellulose in the pretreated wheat straw was 84.5%, the removal rate of hemicellulose was 71.8%, and the removal rate of lignin was 7.1%. The concentrations of glucose, xylose, and arabinose in the supernatant were 1.3 g / L, 8.7 g / L, and 2.3 g / L, respectively.

[0066] Comparative Example 1

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

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

[0069] The cellulose content in the 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, the cellulose content in the wheat straw is 43.2%, the hemicellulose content is 15.6%, the lignin content is 26.8%, and the ash content is 4.1%. The retention rate of cellulose in the pretreated wheat straw is 85.9%, the removal rate of hemicellulose is 56.7%, and the removal rate of lignin is 8.6%. The glucose concentration in the supernatant is 0.5 g / L, the xylose concentration is 2.1 g / L, and the arabinose concentration is 0.7 g / L.

[0070] Comparative Example 2

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

[0072] Operation process: 25 g of crushed wheat straw powder is uniformly mixed with 1 L of dilute sulfuric acid solution (concentration of 1%) to obtain a mixed liquid, and then the mixed liquid is placed in a glass bottle and uniformly mixed on a magnetic stirring device. The mixed liquid is pumped into the circulating water bath cavity for hydrothermal circulation treatment (the treatment temperature is 90°C, and the treatment time is 5 h). The treated mixed liquid is subjected to solid-liquid separation, and the solid residue (wood fiber) is washed to electrical neutrality and air-dried for analysis of the composition of each component. The supernatant is hydrolyzed (121°C, 1 h), rotary evaporated, extracted, and separated to obtain a crude xylose solid.

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

[0074] Comparative Example 3

[0075] The specific implementation is the same as that of Example 4, except that the hydrothermal treatment device is directly used in Comparative Example 3, and an industrial-grade reaction kettle is used for operation. The specific operation steps are as follows:

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

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

[0078]

[0079] Table 1 Detection data of Examples 2-4 and Comparative Examples 1-3

[0080] In summary, compared with Comparative Examples 1, 2 and 3, respectively, the electric heating pretreatment is better than the hydrothermal pretreatment in removing the hemicellulose in the lignocellulose, and the concentration of xylose in the hydrolysis solution obtained by the electric heating pretreatment is significantly higher than that obtained by the hydrothermal pretreatment; taking the content of hemicellulose in the lignocellulose and the concentration of xylose in the pretreatment hydrolysis solution as the target, the advantages of the device and method for electric heating coupled with dilute acid pretreatment of lignocellulose and preparation of xylose are proved; compared with the traditional hydrothermal treatment, the device and method also improve the energy utilization rate.

[0081] Comparative Example 4

[0082] This comparative example is a comparison of Example 2, the same device as in Example 2 is used, only the voltage in the 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, when the voltage is adjusted to 400V, the response of the thermal effect and the electric effect is enhanced, and the removal rate of hemicellulose in the wheat straw is further improved, which shows that in the device of the application, the increase of the voltage can more effectively separate the hemicellulose.

[0086] Comparative Example 5

[0087] This comparative example is a comparison of Example 2, the same device as in Example 2 is used, only the voltage in the 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, when the voltage is adjusted to 100V, the pretreatment temperature is reduced and the electric effect is weakened, and the removal rate of hemicellulose in the wheat straw is greatly reduced, which shows that the selection of the voltage in the application cannot be too small, and the selection range of the voltage is above 200V.

[0091] It should be understood that the above examples are only for illustrating the technical concept and characteristics of the application, and the purpose is to enable those skilled in the art to understand the content of the application and implement it, and it cannot limit the protection scope of the application. Any equivalent changes or modifications made according to the spirit and principle of the application shall be covered within the protection scope of the application.

Claims

1. A method for the pretreatment of lignocellulose with dilute acid and the preparation of xylose by electrothermal coupling, characterized in that, The method uses an electric heating coupling dilute acid pretreatment device for lignocellulose and preparation of xylose; the device is composed of an electric heating reaction unit, a pumping device, a stirring device, a power supply device, and a cooling device; The electric heating reaction unit is composed of a reaction tube, a magnetic core, a water-cooled 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-cooled plate 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-cooled plate is embedded with a cooling pipe for cooling liquid flow; The water-cooled plate is connected to the cooling device through the cooling pipe; the cooling device is used for the cooling liquid in the cooling pipe; The reaction tube is wound around the magnetic core and the water-cooled plate through the middle holes of the magnetic core and the water-cooled plate; the inlet end of the reaction tube is located at the bottom end of the electric heating reaction unit and is connected to the pumping device; the outlet end of the reaction tube is located at the top end of the electric heating reaction unit and is connected to the stirring device through a pipeline; The excitation coil is wound around the magnetic core and connected to the power supply device; the power supply device is used to provide excitation voltage to make the magnetic core generate time-varying magnetic field as excitation source to form induced voltage and induced current in 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; The method comprises the following steps: (1) washing the lignocellulose raw material, then immersing it in an organic solvent for decolorization treatment, and then drying and crushing for standby; (2) mixing the crushed lignocellulose raw material with a dilute acid solution, placing it in the above stirring device, starting the stirring for mixing, and obtaining a mixed solution after uniform mixing, starting the pumping device to send the mixed solution into the reaction tube, starting the power supply device and the cooling device, and performing the reaction; (3) after the reaction in step (2) is completed, the reaction liquid is subjected to solid-liquid separation, the solid is washed to electrical neutrality, and dried; the obtained pretreatment liquid is subjected to hydrolysis, purification and separation to obtain a crude xylose solid; The reaction temperature in step (2) is 80-100℃, the treatment time is 3-7 h; the parameter settings of the power supply device are voltage 200-800 V, current 5-10 A, and power 1-8 KW; the ratio of the voltage set by the power supply device to the pipe diameter of the reaction tube is 200-250 V : 10 mm.

2. The method as claimed in claim 1, characterized in that The material of the magnetic core is amorphous nanocrystalline soft magnetic material; the length of the magnetic core is 30~100 cm L 1 is 30~100 cm, the width of the magnetic core is 15~50 cm W 1 is 30~100 cm, the width of the magnetic core is 15~50 cm H The distance from the middle hole to the width is 3~8 cm l The distance from the middle hole to the length is 5~20 cm w The distance from the middle hole to the length is 5~20 cm.

3. The method of claim 1, wherein, The reaction tube is an acid and alkali resistant glass or silica gel tube.

4. The method of claim 1, wherein, In step (1), the lignocellulose raw material includes straw and sawdust; the straw includes wheat straw and corn straw; the sawdust includes poplar sawdust, eucalyptus sawdust, sugarcane residue, and bamboo powder.

5. The method as claimed in claim 1, wherein, 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%.

6. The method as claimed in claim 1, wherein, In step (2), the mass-volume ratio of the crushed lignocellulose raw material to the dilute acid solution is 1 g : 10-50 mL.

7. The method as claimed in claim 1, wherein, After the power supply device is turned on in step (2), the magnetic field strength of the magnetic core is 0.5-2 T.

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