System and method for continuously catalyzing hydrolysis of cellulose into sugar

Abstract

The invention provides a system and a method for continuously catalyzing hydrolysis of cellulose into sugar. The invention relates to a method for continuously catalyzing hydrolysis of cellulose into sugar, which comprises the following steps: continuously conveying slurry containing solid acid and cellulose into a reactor, and hydrolyzing at the temperature of 100-250 DEG C under the condition of microwave irradiation to obtain hydrolysate; wherein the retention time of the slurry in the reactor is 1-60 minutes; and continuously outputting the hydrolysate from the reactor, and cooling until the temperature is less than or equal to 50 DEG C. According to the method, the slurry is subjected to high-power microwave irradiation coupling and synchronous cooling, cellulose in the slurry is rapidly depolymerized through the thermal effect and the non-thermal effect of microwaves, the cellulose is hydrolyzed into sugar, hydrolysate containing sugar products is obtained, meanwhile, the overall temperature of the hydrolysate is reduced, and side reactions such as sugar degradation are inhibited; meanwhile, rapid depolymerization of cellulose and selectivity of sugar are realized.

Description

Technical Field

[0001] This disclosure relates to the field of cellulose hydrolysis technology, and in particular to a system and method for continuous catalytic hydrolysis of cellulose into sugars. Background Technology

[0002] Cellulose is composed of glucose units linked by β-1,4-glycosidic bonds and is the most abundant renewable carbon source. The difficulty in hydrolyzing cellulose into sugar lies in: (1) the abundant intermolecular hydrogen bonds make the cellulose crystal structure stubborn, chemically stable, and reaction accessible, which seriously restricts the saccharification rate of cellulose. (2) the energy required for the depolymerization of cellulose macromolecules is significantly higher than the energy required for the ether bond breaking at O5 in the glucose ring, making the ring opening of glucose unavoidable, and there is a synchronous contradiction between cellulose depolymerization and glucose degradation.

[0003] Numerous hydrolysis systems have been developed for the efficient hydrolysis of cellulose into sugars. For example, isotropic homogeneous liquid acid hydrolysis systems possess excellent mass transfer rates, but they cannot precisely match the stage-specific energy requirements of the cellulose hydrolysis process, resulting in poor sugar selectivity. The high costs associated with artificial enzyme iteration and sugar-liquid separation in ionic liquid systems remain unresolved. In recent years, with the gradual development and improvement of theories driving cellulose hydrolysis, systems that break down cellulose aggregation structures using strongly adsorbed solid acids have gained increasing attention, offering advantages over homogeneous systems such as better chemical stability and ease of separation. Solid acids have a strong affinity for cellulose, effectively breaking down its aggregation structure and improving hydrolysis efficiency. However, traditional heat transfer methods result in prolonged solid acid-catalyzed cellulose hydrolysis reaction times, leading to excessive sugar degradation and making it difficult to resolve the synchronicity issue between cellulose depolymerization and glucose degradation. Summary of the Invention

[0004] This disclosure provides a system and method for the continuous catalytic hydrolysis of cellulose into sugars, to at least solve one of the technical problems existing in the prior art.

[0005] In a first aspect, this application provides a method for the continuous catalytic hydrolysis of cellulose into sugars, the method comprising: A slurry containing solid acid and cellulose is continuously fed into a reactor and hydrolyzed at a temperature of 100-250°C under microwave irradiation to obtain a hydrolysate; wherein the residence time of the slurry in the reactor is 1-60 min. The hydrolysate is continuously discharged from the reactor and then cooled to a temperature of less than or equal to 50°C.

[0006] In one embodiment, the pH value of the slurry is 1 to 7.

[0007] In an embodiment, the slurry is mixed from the solid acid, the cellulose and a solvent, and the solvent is water or low acid.

[0008] In an embodiment, the solid content in the slurry is 0.01% to 10%, and the mass ratio of the solid acid to the cellulose is 1:10 to 1:0.1.

[0009] In an embodiment, the surface of the solid acid has -OH groups and acid functional groups, and the acid functional groups are one or more of -COOH, -SO3H and -PO3H2. The cellulose is selected from one or more of virgin fiber, microcrystalline cellulose and regenerated cellulose. The low acid is dilute sulfuric acid.

[0010] In an embodiment, the particle size of the solid acid is 200 nm to 50 μm, and the particle size of the cellulose is 1 to 500 μm.

[0011] In an embodiment, the volume of the reactor to the flow rate of the slurry is 1 ml to 3 L: 1 to 50 ml / min.

[0012] In a second aspect, the present application provides a system for continuously catalyzing hydrolysis of cellulose into sugar, for implementing the above method, and the system comprises: a reaction device, which comprises a containing shell, a reactor with a reaction chamber inside, a microwave generator and an air compressor, the containing shell has a containing cavity, the reactor is placed in the containing cavity, the microwave generator is arranged on the inner wall of the containing cavity to microwave irradiate the reactor, and the air compressor is in communication with the containing cavity to adjust the temperature of the reaction system in the reactor; a feeding pipe in communication with the reactor, for continuously feeding a slurry containing solid acid and cellulose into the reactor, so that the slurry is hydrolyzed in the reaction chamber of the reactor to obtain a hydrolysis liquid; a first discharging pipe, a first end of which is in communication with the reactor, for continuously discharging the hydrolysis liquid; a cooler configured to cool the hydrolysis liquid.

[0013] In an embodiment, the system further comprises a storage tank for storing the slurry, the storage tank is in communication with the feeding pipe through a pressurizing pump, and the pressurizing pump is used to pump the slurry into the reaction chamber of the reactor.

[0014] In an embodiment, the system further comprises: a pressure stabilizing tank arranged between the reaction device and the cooler, and the pressure stabilizing tank is in communication with a second end of the first discharging pipe. The main gas line is connected to an external gas source at its first end. The first gas path branch has its first end connected to the second end of the main gas path and its second end connected to the reactor, and is used to deliver gas to the reactor. The second gas line branch has its first end connected to the second end of the main gas line and the first end of the first gas line branch, and its second end connected to the pressure stabilizing tank, and is used to deliver gas to the pressure stabilizing tank. The first back pressure valve is located on the main gas line and near its first end. The first back pressure valve is used to regulate and stabilize the pressure of gas from an external gas source entering the main gas line. The second back pressure valve is located on the first gas path branch and is used to regulate and stabilize the internal pressure of the reactor. The third back pressure valve, located at the outlet end of the pressure stabilizing tank, is used to regulate the exhaust pressure of the pressure stabilizing tank in order to balance the internal pressure of the reactor and the pressure stabilizing tank.

[0015] In one possible embodiment, the cooler includes: A coil, the first end of which is connected to the pressure stabilizing tank via a second discharge pipe; A cooling tank filled with coolant is used to immerse the coil in the coolant to cool the hydrolysate in the coil.

[0016] In one embodiment, the system further includes a collection tank, which is connected to the second end of the coil via a third discharge pipe, for storing the cooled hydrolysate.

[0017] Compared with existing technologies, the advantages of this application are as follows: 1) The method of this application simultaneously cools the slurry through high-power microwave irradiation coupling, utilizing the thermal and non-thermal effects of microwaves to rapidly depolymerize the cellulose in the slurry, hydrolyzing the cellulose into sugars to obtain a hydrolysate containing sugar products. Simultaneously, it lowers the overall temperature of the hydrolysate, inhibiting side reactions such as sugar degradation, and simultaneously achieving rapid depolymerization of cellulose and improved sugar selectivity. This method achieves rapid hydrolysis of cellulose in the slurry into sugars, overcoming the shortcomings of existing technologies and enabling large-scale, continuous, efficient, and highly selective hydrolysis of cellulose. 2) The method of this application utilizes the microwave absorption properties of solid acids to convert microwave energy into heat energy for rapid depolymerization of cellulose. The resulting hydrolysate is maintained at a low temperature using a simultaneous cooling system, inhibiting sugar degradation and improving sugar selectivity. Furthermore, by cleverly utilizing the characteristic that solid acids have a strong adsorption capacity for large cellulose molecules but a poor adsorption capacity for small sugar molecules, an adsorption-mass transfer-depolymerization-desorption cycle is formed on the surface of the solid acid, which enhances the mass transfer efficiency of the cellulose hydrolysis process, accelerates cellulose depolymerization, and improves cellulose saccharification performance, thus resolving the contradiction between the synchronicity of cellulose depolymerization and glucose degradation.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0019] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0020] Figure 1 A schematic diagram of a system for the continuous catalytic hydrolysis of cellulose into sugars according to an embodiment of the present disclosure is shown; Figure 2 A schematic diagram of the structure of the reaction apparatus according to an embodiment of the present disclosure is shown; Figure 3 The cellulose conversion rate of embodiments of this disclosure is shown; Figure 4 The cellulose hydrolysis yield to sugars according to embodiments of this disclosure is shown; Figure 5 The yield of cellulose hydrolyzed into sugars according to an embodiment of this disclosure is shown; Figure 6 A photograph of the hydrolysate obtained from the hydrolysis of cellulose according to an embodiment of this disclosure is shown.

[0021] Reference numerals: 1-Reaction apparatus, 2-Cooler, 3-Storage tank, 4-Pressure stabilizing tank, 5-Collection tank, 6-Ball valve, 11-Containing shell, 12-Reactor, 13-Microwave generator, 14-Air compressor, 15-Infeed pipe, 16-First discharge pipe, 17-Magnetic stirrer, 18-Temperature sensor, 21-Coil, 22-Second discharge pipe, 23-Cooling tank, 31-Pressure pump, 41-Main gas path, 42-First gas path branch, 43-Second gas path branch, 44-First back pressure valve, 45-Second back pressure valve, 46-Third back pressure valve, 51-Third discharge pipe, 111-Containing cavity, 121-Reaction chamber. Detailed Implementation

[0022] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0023] Firstly, addressing the shortcomings of existing solid acid-catalyzed cellulose hydrolysis to sugar conversion technologies, this application provides a method for continuous catalytic cellulose hydrolysis to sugar conversion, used for the efficient hydrolysis of cellulose to sugar in slurries in low-acid or pure water systems; the method includes: Step 1) The slurry containing solid acid and cellulose is continuously fed into the reactor and hydrolyzed at a temperature of 100~250℃ under microwave irradiation to obtain hydrolysate; wherein the residence time of the slurry in the reactor is 1~60min. Step 2), after the hydrolysate is continuously discharged from the reactor, it is cooled to a temperature of less than or equal to 50°C.

[0024] This application's method involves synchronously cooling the slurry using high-power microwave irradiation coupling. Utilizing the thermal and non-thermal effects of microwaves, the cellulose in the slurry is rapidly depolymerized, hydrolyzing it into sugars to obtain a hydrolysate containing sugar products. Simultaneously, the overall temperature of the hydrolysate is reduced, inhibiting side reactions such as sugar degradation. This achieves both rapid cellulose depolymerization and improved sugar selectivity. This method enables the rapid hydrolysis of cellulose in the slurry into sugars, overcoming the shortcomings of existing technologies and allowing for large-scale, continuous, efficient, and highly selective hydrolysis of cellulose.

[0025] This application utilizes the microwave absorption properties of solid acids to convert microwave energy into heat energy for rapid depolymerization of cellulose. The resulting hydrolysate is maintained at a low temperature (≤50°C) using a synchronous cooling system, inhibiting sugar degradation and improving sugar selectivity. Furthermore, it cleverly leverages the characteristic that solid acids have strong adsorption for large cellulose molecules but poor adsorption for small sugar molecules, forming an adsorption-mass transfer-depolymerization-desorption cycle on the solid acid surface. This enhances the mass transfer efficiency of the cellulose hydrolysis process, accelerates cellulose depolymerization, and improves cellulose saccharification performance, resolving the contradiction between the synchronicity of cellulose depolymerization and glucose degradation.

[0026] Furthermore, the method described in this application enables the continuous transport of slurries containing solid acids and cellulose, overcoming the bottleneck in continuous cellulose hydrolysis production and effectively increasing cellulose saccharification capacity. Therefore, the method described in this application can significantly improve the catalytic hydrolysis rate of cellulose in slurries, meeting the requirements for large-scale industrial application of the technology.

[0027] For example, in the method of this application, the hydrolysate is a hydrolysate including sugar products, which are water-soluble monosaccharides or mixed sugars (DP value between 1 and 10), and are glucose or short chains with glucose units linked by β-1,4-glycosidic bonds.

[0028] For example, the required temperatures for hydrolysis are 100°C, 125°C, 150°C, 175°C, 200°C, 225°C, and 250°C. Preferably, the required temperature for hydrolysis is 150~200°C. Preferably, the residence time of the slurry in the reactor is 1~20 min.

[0029] In one embodiment, the pH value of the slurry of this application is 1 to 7. Exemplarily, the slurry has pH values ​​of 1, 2, 3, 4, 5, 6, and 7. Preferably, the slurry is a mixture of a solid acid, cellulose, and a solvent, wherein the solvent is pure water or a low-acid solution. Preferably, the low-acid solution is dilute sulfuric acid. When the solvent is pure water, the slurry is a pure water system composed of a solid acid, cellulose, and pure water. When the solvent is dilute sulfuric acid, the slurry is a low-acid aqueous system composed of a solid acid, cellulose, and dilute sulfuric acid.

[0030] In one embodiment, the solid content in the slurry is 0.01% to 10%; the mass ratio of solid acid to cellulose is 1:10 to 1:0.1. Exemplarily, the solid content in the slurry is 0.01%, 0.1%, 1%, 5%, or 10%. Exemplarily, the mass ratio of solid acid to cellulose is 1:0.1, 1:0.5, 1:1, 1:5, or 1:10.

[0031] For example, the surface of the solid acid has -OH groups and acidic functional groups, which are one or more of -COOH, -SO3H, and -PO3H2. The solid acid is a water-insoluble solid, and its form includes, but is not limited to, spherical, gourd-shaped, nano-shaped, one-dimensional linear / rod-shaped, and two-dimensional sheet-like.

[0032] Preferably, the particle size of the solid acid is 200 nm to 50 μm.

[0033] For example, the solid acid of this application is prepared by hydrothermal functionalization of a carbon source and a substrate containing acidic groups.

[0034] For example, the solid acid includes, but is not limited to, sulfonic acid (-SO3H) type solid acid, phosphoric acid (-PO3H2) type solid acid, sulfonic acid-phosphoric acid coexisting type solid acid, and sulfonic acid-carboxyl coexisting type solid acid.

[0035] The sulfonic acid group (-SO3H) type solid acid includes, but is not limited to: sulfonated carbon-based solid acids (e.g., sulfonated carbon nanotubes, sulfonated mesoporous carbon, sulfonated graphene, sulfonated hydrothermal carbon), sulfonated polymer solid acids (e.g., sulfonated polystyrene resins (such as Nafion resins, cation exchange resins), sulfonated polyether ether ketones (SPEEK)).

[0036] Phosphoric acid (-PO3H2) type solid acids include, but are not limited to: phosphorylated carbon-based solid acids (such as phosphorylated hydrothermal carbon, phosphorylated molecular sieves, phosphorylated porous carbon, phosphorylated carbon nanotubes, etc.), phosphorylated polymer solid acids (such as: phosphorylated resins, phosphorylated polyesters / polyurethanes, etc.).

[0037] The sulfonic acid-phosphoric acid coexisting type solid acid includes, but is not limited to: sulfonated-phosphorylated silica composite oxide (SO3H-PO3H2-SiO2) and sulfonic acid-phosphoric acid hybrid carbon materials.

[0038] The sulfonic acid-carboxyl coexisting type solid acid includes, but is not limited to: sulfonated-carboxylated carbon nanotubes and sulfonic acid-carboxyl copolymers.

[0039] For example, the cellulose is selected from one or more of virgin fibers, microcrystalline cellulose, and regenerated cellulose. Virgin fibers include, but are not limited to, plant straw and pulp. Regenerated cellulose includes lyocell fiber, regenerated cellulose pretreated with phosphoric acid, etc., and viscose fiber. Exemplarily, the regenerated cellulose is regenerated corn cob cellulose.

[0040] Preferably, the cellulose particle size is 1~500μm.

[0041] In one embodiment, the reactor volume to slurry flow rate ratio is 1 ml~3 L : 1~50 ml / min. The method of this application controls the residence time of the continuously flowing slurry within the reactor by controlling the reactor volume and the slurry flow rate, thereby achieving continuous hydrolysis of cellulose into sugars.

[0042] For example, when the reactor volume is 10 ml and the slurry flow rate is 10 ml / min, the residence time of the slurry in the reactor is 1 min. When the reactor volume is 100 ml and the slurry flow rate is 20 ml / min, the residence time of the slurry in the reactor is 5 min. When the reactor volume is 1 L and the slurry flow rate is 50 ml / min, the residence time of the slurry in the reactor is 20 min. When the reactor volume is 3 L and the slurry flow rate is 50 ml / min, the residence time of the slurry in the reactor is 60 min.

[0043] Secondly, this application provides a system for the continuous catalytic hydrolysis of cellulose into sugars, the system comprising: The reaction apparatus 1 includes a housing 11, a reactor 12 having a reaction chamber 121 inside, a microwave generator 13, and an air compressor 14. The housing 11 has a cavity 111, the reactor 12 is placed in the cavity 111, the microwave generator 13 is disposed on the inner wall of the cavity 111 to irradiate the reactor 12 with microwaves, and the air compressor 14 is connected to the cavity 111 to regulate the temperature of the reaction system inside the reactor 12. Feed pipe 15, which is connected to reactor 12, is used to continuously feed a slurry containing solid acid and cellulose into the reaction chamber 121 of reactor 12 so that the slurry is hydrolyzed in the reaction chamber 121 of reactor 12 to obtain a hydrolysate containing sugar products. The first discharge pipe 16 is connected at its first end to the reactor 12 for continuous output of hydrolysate; Cooler 2 is configured to cool the hydrolysate.

[0044] In this system, a feed pipe 15 continuously delivers slurry to the reaction chamber 121 of the reactor 12. Microwave irradiation from a microwave generator 13 provides both thermal and non-thermal effects for the hydrolysis of cellulose in the slurry, and synergistically, solid acid catalyzes the hydrolysis of cellulose into sugars. The microwave generator 13 continuously irradiates the reactor 12 and, in conjunction with an air compressor 14 (which uses compressed air to purge the containment chamber 111), regulates the hydrolysis reaction temperature (i.e., the reaction system temperature) of the slurry contained in the reaction chamber 121 of the reactor 12.

[0045] For example, multiple microwave generators 13 are arranged in an array on the inner wall of the accommodating cavity 111. The microwave irradiation power of the microwave generators 13 can be adjusted within the range of 0~300W / cm². 2 The reactor 12 can be continuously irradiated.

[0046] For example, the air compressor 14 can be linked with the microwave generator 13 to control the temperature of the slurry hydrolysis reaction in the reactor, and the purge air flow rate of the air compressor 14 is in the range of 0~3 m³ / s. 3 / min, which can maintain the temperature of the hydrolysis reaction system (hereinafter referred to as the hydrolysis reaction temperature) between 100 and 250℃.

[0047] For example, the pressure required for hydrolysis of the slurry in the reaction chamber 121 of reactor 12 is 0.1 MPa to 2.6 MPa. Exemplarily, the pressure required for this hydrolysis is 0.1 MPa, 0.23 MPa, 0.48 MPa, 0.89 MPa, 1.55 MPa, or 2.6 MPa.

[0048] For example, such as Figure 2As shown, the feed pipe 15 extends into the bottom of the reaction chamber 121 of the reactor 12, and the first end of the first discharge pipe 16 is located at the top of the reaction chamber 121 of the reactor 12. Thus, when the slurry is fed into the bottom of the reaction chamber 121 via the feed pipe 15 and subjected to microwave irradiation to hydrolyze the cellulose in the slurry into sugars, the hydrolysate is slowly pushed out from the bottom of the reaction chamber 121 from bottom to top due to the continuous feeding of the slurry. This results in the hydrolysate being output from the first discharge pipe 16 located at the top of the reaction chamber. The output hydrolysate is then cooled to below 50°C by the cooler 2 to inhibit the degradation of the sugar products in the hydrolysate.

[0049] For example, reactor 12 is a reaction flask with a pressure-relieving soft cap, thereby forming a sealed reaction chamber 121 inside reactor 12. Reactor 12 is made of materials that do not absorb microwaves, including but not limited to glass, quartz, sapphire, etc.

[0050] For example, the reaction apparatus 1 also includes a stirring mechanism and a temperature sensor 18. Exemplarily, the stirring mechanism can be a magnetic stirrer 17, the main body of which is located outside and close to the reactor 12. The magnetic stirrer's magnet is located in the reaction chamber 121 of the reactor 12, and the stirring of the slurry within the reactor is achieved through magnetic stirring. Of course, the stirring mechanism can also be a paddle stirrer, a turbine stirrer, a propeller stirrer, etc., with the stirring shaft of these stirrers placed in the reaction chamber 121 to achieve stirring of the slurry within the reactor.

[0051] The temperature sensor 18 is located near the bottom of the reactor 12 and is used to collect the temperature of the reactor 12 in real time. The collected temperature is fed back to the control unit, which controls and adjusts the power of the microwave generator 13 and the purge air flow of the air compressor 14 to adjust the temperature inside the containment cavity 111, thereby achieving the regulation of the reaction temperature of the reactor 12.

[0052] Therefore, the system for continuous catalytic hydrolysis of cellulose into sugar of this application can realize the continuous conveying of slurry containing solid acid and cellulose. By cooperating with an air compressor and a microwave generator, the temperature and pressure required for the cellulose hydrolysis process are maintained, enabling real-time feeding and discharging. This breaks through the bottleneck of continuous cellulose hydrolysis production, effectively improves cellulose saccharification capacity, and meets the needs of large-scale industrial application of the technology.

[0053] In one embodiment, the system further includes a storage tank 3 for storing slurry. The storage tank 3 is connected to a feed pipe 15 via a pressure pump 31, which continuously pumps the slurry into the reaction chamber 121 of the reactor 12. The storage tank 3 is equipped with a mechanical stirring device with a rotation speed of 5-300 rpm. The volume of the storage tank 3 is between 500 ml and 5000 ml, and the internal environment is at atmospheric pressure, allowing for slurry replenishment at any time. The bottom of the storage tank 3 has a first outlet, which is connected to a first end of the feed pipe 15 via the pressure pump 31. The second end of the feed pipe 15 extends into the bottom of the reaction chamber 121 of the reactor 12. The pressure pump 31 continuously delivers the slurry from the storage tank 3 to the reaction chamber 121 of the reactor via the feed pipe 15. Preferably, a ball valve 6 is provided between the first outlet at the bottom of the storage tank 3 and the pressure pump 31 to control the slurry delivery. More preferably, a ball valve 6 is also provided at the first discharge port at the bottom of the storage tank 3 for discharging slurry. The flow rate of the pressure pump 31 is 1~50mL / min, which can transport suspension slurry containing solids, and the flow rate accuracy of the pressure pump 31 is controlled within 1ml / min.

[0054] In one possible implementation, the system of this application further includes: A pressure stabilizing tank 4 is located between the reaction device 1 and the cooler 2. The pressure stabilizing tank 4 is connected to the second end of the first discharge pipe 16. The main gas line 41 is connected to an external gas source at its first end. First gas path branch 42, the first end of the first gas path branch 42 is connected to the second end of the main gas path 41 and the second end is connected to the reactor 12, and is used to deliver gas to the reactor 12; The second gas path branch 43 has its first end connected to the second end of the main gas path 41 and the first end of the first gas path branch 42, and its second end connected to the pressure stabilizing tank 4, for supplying gas to the pressure stabilizing tank 4. The first back pressure valve 44 is located on the main gas line 41 and near its first end. The first back pressure valve 44 is used to regulate and stabilize the pressure of gas from the external gas source entering the main gas line 41. The second back pressure valve 45 is located on the first gas path branch 42 and is used to regulate and stabilize the internal pressure of the reactor 12. The third back pressure valve 46 is located at the outlet end of the pressure stabilizing tank 4 and is used to regulate the exhaust pressure of the pressure stabilizing tank 4 in order to balance the internal pressure of the reactor 12 and the pressure stabilizing tank 4.

[0055] The first back pressure valve 44 regulates the pressure of the gas from the external gas source entering the main gas path 41, ensuring a stable flow of gas into the first gas branch path 42 and the second gas branch path 43. The second back pressure valve 45 directly regulates the internal pressure of the reactor. The third back pressure valve 46 is located at the outlet of the pressure stabilizing tank, indirectly controlling the internal pressure of the pressure stabilizing tank by adjusting the exhaust pressure, thus achieving a balance with the internal pressure of the reactor.

[0056] For example, the pressure stabilizing tank 4 has a volume between 1000 mL and 5000 mL, and can withstand a pressure of 0 to 4 MPa. The connection point between the first discharge pipe 16 and the pressure stabilizing tank 4 is located near the top of the pressure stabilizing tank 4. Preferably, a ball valve 6 is provided on the first discharge pipe 16 for controlling the delivery of the hydrolysate. A stirring shaft is provided inside the pressure stabilizing tank 4, and the stirring shaft rotates at a speed of 5 to 300 rpm. An vent pipe is provided at the top of the pressure stabilizing tank 4, and a third back pressure valve 46 is provided on the vent pipe for adjusting the exhaust pressure of the pressure stabilizing tank 4.

[0057] For example, the cooler 2 of this application includes: Coil 21, the first end of coil 21 is connected to pressure tank 4 through second discharge pipe 22; Cooling tank 23 is filled with coolant, and coil 21 is immersed in coolant to cool the hydrolysate in coil 21.

[0058] The coolant includes, but is not limited to, water, organic solvents, or phase change materials. Preferably, the coolant is water; more preferably, the coolant is water, and the cooling tank is constructed as a heat exchange tank.

[0059] For example, the pressure tank 4 has a second discharge port at the bottom, which is connected to the second discharge pipe 22 via a ball valve 6.

[0060] For example, the system of this application also includes a liquid collection tank 5, which is connected to the second end of the coil 21 through a third discharge pipe 51, for storing the cooled hydrolysate.

[0061] The volume of the collection tank 5 is 1~10 L. It does not require mechanical stirring and is kept at normal pressure. The hydrolysate is injected from the top of the collection tank 5 and a ball valve 6 is connected to the bottom of the collection tank 5.

[0062] The present application will be further described in detail below with reference to specific embodiments: Example 1 Please see Figure 1 and Figure 2A system for the continuous catalytic hydrolysis of cellulose into sugars, along the material output direction, includes a storage tank 3 for storing slurry, a reaction device 1, a pressure stabilizing tank 4, a cooler 2, and a collection tank 5 arranged sequentially. The reaction device 1 includes a housing 11, a reactor 12 with an internal reaction chamber 121, a microwave generator 13, and an air compressor 14. The housing 11 has a cavity 111, the reactor 12 is placed in the cavity 111, the microwave generator 13 is disposed on the inner wall of the cavity 111 to irradiate the reactor 12 with microwaves, and the air compressor 14 is connected to the cavity 111 to regulate the temperature of the reaction system within the reactor 12. The cooler 2 is configured to cool the hydrolysate and includes a coil 21 and a cooling tank 23. The first outlet at the bottom of the storage tank 3 is connected to the first end of the feed pipe 15 via a ball valve 6 and a pressure pump 31. The pressure pump 31 is used to continuously pump the slurry into the reaction chamber 121 of the reactor 12. The second end of the feed pipe 15 is connected to the reactor 12 and extends into the bottom of the reaction chamber 121, used to continuously supply the slurry containing solid acid and cellulose to the reactor 12, so that the slurry can be hydrolyzed in the reaction chamber 121 of the reactor 12 to obtain hydrolysate. The first end of the first outlet pipe 16 is connected to... Reactor 12 is connected to and extends into the top of reaction chamber 121 for continuous output of hydrolysate; the second end of the first discharge pipe 16 is connected to pressure stabilizing tank 4; the second discharge port at the bottom of pressure stabilizing tank 4 is connected to the first end of coil 21 via ball valve 6 and second discharge pipe 22; cooling tank 23 is filled with coolant, and coil 21 is immersed in coolant to cool the hydrolysate; the second end of coil 21 is connected to collection tank 5 via third discharge pipe 51, which is used to store the cooled hydrolysate; The main gas line 41 is connected to an external gas source at its first end. First gas path branch 42, the first end of the first gas path branch 42 is connected to the second end of the main gas path 41 and the second end is connected to the reactor 12, and is used to deliver gas to the reactor 12; The second gas path branch 43 has its first end connected to the second end of the main gas path 41 and the first end of the first gas path branch 42, and its second end connected to the pressure stabilizing tank 4, for supplying gas to the pressure stabilizing tank 4. The first back pressure valve 44 is located on the main gas line 41 and near its first end. The first back pressure valve 44 is used to regulate and stabilize the pressure of gas from the external gas source entering the main gas line 41. The second back pressure valve 45 is located on the first gas path branch 42 and is used to regulate and stabilize the internal pressure of the reactor 12. The third back pressure valve 46 is located at the outlet end of the pressure stabilizing tank 4 and is used to regulate the exhaust pressure of the pressure stabilizing tank 4 in order to balance the internal pressure of the reactor 12 and the pressure stabilizing tank 4. The storage tank 3 has a volume of 500 mL, the reactor 12 has a volume of 10 mL, the pressure stabilizing tank 4 has a volume of 500 mL, and the collection tank 5 has a volume of 2 L. The flow rate of the pressurizing pump 31 is 10 mL / min. The mass ratio of solid acid to cellulose in the slurry is 1:10, the solid content is 0.01%, and the pH value of the slurry is 6 (i.e., the slurry is a low-acid aqueous phase system composed of solid acid (specifically sulfonated hydrothermal carbon), cellulose (specifically regenerated corn cob cellulose), and dilute sulfuric acid, resulting in a pH value of 6). The slurry is hydrolyzed in reactor 12 at a hydrolysis reaction temperature of 100 ℃, a pressure of 0.1 MPa, and under microwave irradiation conditions. The residence time of the slurry in reactor 12 is 1 min. The slurry is hydrolyzed in reactor 12 to obtain hydrolysate. The hydrolysate enters the pressure stabilizing tank 4 through the first discharge pipe 16, and then enters the coil 21 through the second discharge pipe 22. The hydrolysate in the coil is cooled to 50 ℃ by the coolant outside the coil 21. The cooled hydrolysate enters the collection tank 5 through the third discharge pipe 51.

[0063] In Example 1, a hydrolysate was prepared, in which the final cellulose conversion rate was 36.3%, the sugar yield was 18.8%, and the sugar yield was 0.11 kg / d.

[0064] Example 2 This embodiment 2 is largely the same as embodiment 1, except that: the volume of storage tank 3 is 1 L, the volume of reactor 12 is 100 mL, the volume of pressure stabilizing tank 4 is 1 L, and the volume of collection tank 5 is 3 L. The flow rate of pressurizing pump 31 is 20 mL / min, the mass ratio of solid acid to cellulose in the slurry is 1:5, the solid content is 0.1%, the pH value of the slurry is 5, and the slurry is hydrolyzed in reactor 12 under hydrolysis reaction conditions of 125 ℃, 0.23 MPa, and microwave irradiation. The residence time of the slurry in reactor 12 is 5 min; wherein, the slurry is hydrolyzed in reactor 12 to obtain hydrolysate, and the hydrolysate is cooled to 45 ℃ by a cooler.

[0065] In Example 2, a hydrolysate was prepared, in which the final cellulose conversion rate was 52.8%, the sugar yield was 38.1%, and the sugar yield was 0.74 kg / d.

[0066] Example 3 This embodiment 3 is largely the same as embodiment 1, except that: the volume of storage tank 3 is 2 L, the volume of reactor 12 is 300 mL, the volume of pressure stabilizing tank 4 is 2 L, and the volume of collection tank 5 is 4 L. The flow rate of pressurizing pump 31 is 30 mL / min, the mass ratio of solid acid to cellulose in the slurry is 1:1, the solid content is 1%, the pH value of the slurry is 4, and the slurry is hydrolyzed in reactor 12 under hydrolysis reaction conditions of 150 ℃, 0.48 MPa, and microwave irradiation. The residence time of the slurry in reactor 12 is 10 min. The slurry is hydrolyzed in reactor 12 to obtain hydrolysate, which is then cooled to 40 ℃ by a cooler.

[0067] In Example 3, a hydrolysate was prepared, in which the final cellulose conversion rate was 71.5%, the sugar yield was 59.4%, and the sugar yield was 1.32 kg / d.

[0068] Example 4 This embodiment 4 is largely the same as embodiment 1, except that: the volume of storage tank 3 is 3 L, the volume of reactor 12 is 600 mL, the volume of pressure stabilizing tank 4 is 3 L, and the volume of collection tank 5 is 5 L. The flow rate of pressurizing pump 31 is 40 mL / min, the mass ratio of solid acid to cellulose in the slurry is 1:0.5, the solid content is 5%, the pH value of the slurry is 3, and the slurry is hydrolyzed in reactor 12 under hydrolysis reaction conditions of 175 ℃, 0.89 MPa, and microwave irradiation. The residence time of the slurry in reactor 12 is 15 min; wherein, the slurry is hydrolyzed in reactor 12 to obtain hydrolysate, and the hydrolysate is cooled to 35 ℃ by a cooler.

[0069] In Example 4, a hydrolysate was prepared, in which the final cellulose conversion rate was 83.3%, the sugar yield was 72.5%, and the sugar yield was 1.96 kg / d.

[0070] Example 5 This embodiment 5 is largely the same as embodiment 1, except that: the volume of storage tank 3 is 4 L, the volume of reactor 12 is 1 L, the volume of pressure stabilizing tank 4 is 4 L, and the volume of collection tank 5 is 6 L. The pump flow rate is 50 mL / min, the mass ratio of solid acid to cellulose in the slurry is 1:0.1, the solid content is 10%, the pH value of the slurry is 2, and the slurry is hydrolyzed in reactor 12 under hydrolysis reaction conditions of 200℃, 1.55 MPa, and microwave irradiation. The residence time of the slurry in reactor 12 is 20 min; wherein, the slurry is hydrolyzed in reactor 12 to obtain hydrolysate, and the hydrolysate is cooled to 30℃ by a cooler.

[0071] In Example 5, a hydrolysate was prepared in which the final cellulose conversion rate was 100%, the sugar yield was 85.5%, and the sugar yield was 2.51 kg / d.

[0072] Example 6 This embodiment 6 is largely the same as embodiment 5, except that the slurry undergoes hydrolysis in reactor 12 at a temperature of 225 ℃ and a pressure of 2.6 MPa.

[0073] Example 6 prepared a hydrolysate in which the final cellulose conversion rate was 100%, the sugar yield was 68.84%, and the sugar yield was 1.04 kg / d.

[0074] Example 7 This Example 7 is largely the same as Example 3, except that the solid acid used for hydrolyzing cellulose is a phosphoric acid-based solid acid (specifically, phosphorylated carbon nanotubes).

[0075] Example 7 prepared a hydrolysate with a final cellulose conversion rate of 66.8%, a sugar yield of 50.3%, and a sugar production of 0.85 kg / d.

[0076] Example 8 This Example 8 is largely the same as Example 3, except that the solid acid used for hydrolyzing cellulose is a sulfonic acid-carboxyl coexisting solid acid (specifically, sulfonated-carboxylated carbon nanotubes are used).

[0077] Example 8 prepared a hydrolysate with a final cellulose conversion rate of 78.6%, a sugar yield of 61.3%, and a sugar yield of 1.57 kg / d.

[0078] Comparative Example 1 Comparative Example 1 is largely the same as Example 1, except that the slurry is hydrolyzed in reactor 12 at a temperature of 75°C.

[0079] The hydrolysate prepared in Comparative Example 1 had a final cellulose conversion rate of 25.37%, a sugar yield of 8.94%, and a sugar production of 0.028 kg / d.

[0080] Comparative Example 2 Comparative Example 2 is largely the same as Example 1, except that ZSM-5 catalyst was used. The hydrolysate obtained in Comparative Example 2 had a cellulose conversion rate of 28.35%, a sugar yield of 10.67%, and a sugar production of 0.079 kg / d.

[0081] Comparative Example 3 Comparative Example 3 is largely the same as Example 1, except that zeolite is used as the catalyst. The hydrolysate obtained in Comparative Example 3 has a cellulose conversion rate of 18.06%, a sugar yield of 9.45%, and a sugar production of 0.068 kg / d.

[0082] Based on Examples 1-5 above, the reaction system parameters of the slurry are shown in Appendix Table 1, and the hydrolysis effect of the slurry is shown in Appendix Table 1. Figures 3-5 The photos of the hydrolysates obtained in Examples 1-5 above are shown below. Figure 6 As shown.

[0083] Table 1. Cellulose conversion rate, sugar yield, and sugar production of each example and comparative example.

[0084] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0085] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0086] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for continuous catalytic hydrolysis of cellulose into sugars, characterized in that: The method includes: A slurry containing solid acid and cellulose is continuously fed into a reactor and hydrolyzed at a temperature of 100-250°C under microwave irradiation to obtain a hydrolysate; wherein the residence time of the slurry in the reactor is 1-60 min. The hydrolysate is continuously discharged from the reactor and then cooled to a temperature of less than or equal to 50°C.

2. The method according to claim 1, characterized in that: The pH value of the slurry is 1~7.

3. The method according to claim 2, characterized in that: The slurry is composed of the solid acid, the cellulose, and a solvent, wherein the solvent is water or a low-acid solution.

4. The method according to claim 3, characterized in that: The solid content in the slurry is 0.01% to 10%; the mass ratio of the solid acid to the cellulose is 1:10 to 1:0.

1.

5. The method according to claim 3, characterized in that: The surface of the solid acid has -OH groups and acidic functional groups, wherein the acidic functional groups are one or more of -COOH, -SO3H, and -PO3H2; The cellulose is selected from one or more of virgin cellulose, microcrystalline cellulose, and regenerated cellulose; The low acid is dilute sulfuric acid.

6. The method according to claim 3, characterized in that: The solid acid has a particle size of 200 nm to 50 μm; the cellulose has a particle size of 1 to 500 μm.

7. The method according to claim 1, characterized in that: The ratio of the reactor volume to the slurry flow rate is 1 ml to 3 L: 1 to 50 ml / min.

8. A system for the continuous catalytic hydrolysis of cellulose into sugars, used to implement the method according to any one of claims 1-7, characterized in that: The system includes: A reaction apparatus, comprising a housing, a reactor having a reaction chamber inside, a microwave generator, and an air compressor, wherein the housing has a cavity, the reactor is placed in the cavity, the microwave generator is disposed on the inner wall of the cavity to irradiate the reactor with microwaves, and the air compressor is connected to the cavity to regulate the temperature of the reaction system inside the reactor; A feed pipe, connected to the reactor, is used to continuously feed a slurry containing solid acid and cellulose into the reactor so that the slurry is hydrolyzed in the reaction chamber of the reactor to obtain a hydrolysate; The first discharge pipe, with its first end connected to the reactor, is used to continuously output the hydrolysate; A cooler configured to cool the hydrolysate.

9. The system according to claim 8, characterized in that: The system further includes a storage tank for storing the slurry, the storage tank being connected to the feed pipe via a pressure pump, the pressure pump being used to pump the slurry into the reaction chamber of the reactor.

10. The system according to claim 8, characterized in that: The system also includes: A pressure stabilizing tank is located between the reaction device and the cooler, and the pressure stabilizing tank is connected to the second end of the first discharge pipe; The main gas line is connected to an external gas source at its first end. The first gas path branch has its first end connected to the second end of the main gas path and its second end connected to the reactor, and is used to deliver gas to the reactor. The second gas line branch has its first end connected to the second end of the main gas line and the first end of the first gas line branch, and its second end connected to the pressure stabilizing tank, and is used to deliver gas to the pressure stabilizing tank. The first back pressure valve is located on the main gas line and near its first end. The first back pressure valve is used to regulate and stabilize the pressure of gas from an external gas source entering the main gas line. The second back pressure valve is located on the first gas path branch and is used to regulate and stabilize the internal pressure of the reactor. The third back pressure valve, located at the outlet end of the pressure stabilizing tank, is used to regulate the exhaust pressure of the pressure stabilizing tank in order to balance the internal pressure of the reactor and the pressure stabilizing tank.

11. The system according to claim 10, characterized in that: The cooler includes: A coil, the first end of which is connected to the pressure stabilizing tank via a second discharge pipe; A cooling tank filled with coolant is used to immerse the coil in the coolant to cool the hydrolysate in the coil.

12. The system according to claim 11, characterized in that: The system also includes a collection tank, which is connected to the second end of the coil via a third discharge pipe, for storing the cooled hydrolysate.

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