Efficient biomass surface treatment process
The external surface of biomass is exposed through adsorption pore filling and desorption technology and chemically modified in a gas phase environment, solving the problem of biomass micropowder modifier enrichment on the inner surface, achieving efficient and economical surface modification, and improving the performance of biomass materials.
Patent Information
- Application Number
- CN202411973789.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-03-14
AI Technical Summary
Due to its complex fine structure and high adsorption capacity, biomass micropowders mainly enrich the modifiers on their inner surfaces, making it difficult to form a good interface with the resin matrix, resulting in poor surface modification effect and low cost performance.
By filling the biomass with adsorbents, exposing the outer surface of the biomass after desorption, chemical modification is performed by gas phase reaction to ensure that the modifier reacts only with the outer surface of the biomass that is not covered by the adsorbents.
The efficiency and economicality of surface modification of biomass micropowders are achieved. The use of a small amount of modifier can achieve excellent surface treatment effect, and the comprehensive performance of bio-based materials is improved.
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Figure CN119613763A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of agriculture, and in particular relates to an efficient biomass surface treatment process. Background Art
[0002] The main components of non-food biomass (straw) are cellulose, hemicellulose, lignin, and a small amount of inorganic salts, phosphates, proteins, and nucleic acids. As a natural renewable resource with abundant reserves, the efficient conversion and application of non-food biomass is of vital importance to the sustainable development of the national economy. The biomass powder prepared by crushing non-food biomass can be used as a filling material in the preparation of bio-based composite materials and degradable resins, thereby significantly reducing the cost of environmentally friendly materials while ensuring the biodegradability of the material, thereby efficiently converting excess biomass resources on the one hand, and promoting the application of environmentally friendly materials on the other hand, reducing the consumption of petroleum resources. However, biomass powder is hydrophilic, has rich microstructures, and also has pesticide residues and complex impurity components that are not suitable for application in environmentally friendly materials, which makes it difficult for biomass to form a good interface with the resin matrix, so it is necessary to perform surface modification on the biomass to improve its comprehensive performance as a filling material.
[0003] The biomass surface contains a large number of hydroxyl functional groups, which can react chemically with a variety of modifiers such as acids, anhydrides, acyl chlorides, epichlorohydrin, silane coupling agents, isocyanates, etc., thereby significantly changing the physical and chemical properties of the biomass surface. However, as a natural material, biomass powder still maintains the unique organizational structure of organisms, and thus has a complex texture and abundant pores, which makes the area of the "inner surface" of the biomass powder much larger than the area of the "outer surface". When biomass is surface treated, the modifier is usually a small molecule substance, which is easy to penetrate into the pores of biomass, and thus will be adsorbed on the inner surface of the biomass in large quantities, mainly forming chemical modifications on the inner surface of the biomass. In contrast, the resin matrix is usually a polymer, because the volume of the molecule is much larger than that of the small molecule substance, it cannot penetrate into the microscopic pores of the biomass, so the resin matrix can often only contact with the outer surface of the biomass and form an interface bond between the two. Due to the difference in the penetration ability of the modifier and the resin matrix and the degree of wetting to the biomass, a large number of active centers formed by surface modification are usually concentrated in the pores of the biomass, and thus cannot fully contact with the resin matrix during material molding, so a good modification effect cannot be achieved. In summary, although biomass micropowder is easy to achieve chemical modification in principle, in actual production, even if more modifiers are consumed, only a very low cost-effective modification effect can be achieved. Summary of the invention
[0004] The present invention provides an efficient biomass surface treatment process, which can overcome the adverse effects brought by the biomass structure itself, efficiently realize the surface modification of biomass micropowder, thereby helping to improve the comprehensive performance of bio-based materials and effectively promote the vigorous development of the bio-based materials industry.
[0005] An efficient biomass surface treatment process of the present invention is carried out according to the following contents:
[0006] The pores of the biomass are filled with adsorbents, and then the filled adsorbents are desorbed to expose the outer surface of the biomass, thereby chemically modifying the biomass, thereby completing the efficient biomass surface treatment.
[0007] Furthermore, the biomass is corn straw powder, rice husk powder, reed powder, palm peel powder, bagasse powder, soybean meal powder, bamboo powder or wood powder with a mesh size of 200 to 1600.
[0008] Furthermore, the adsorbent is one or more of alkanes, cycloalkanes, lipids, naphthalene and petroleum ether.
[0009] Furthermore, the alkane is n-pentane, n-hexane or n-octane; the cycloalkane is cyclohexane or cyclopentane; and the lipid is ethyl acetate or butyl acetate.
[0010] Furthermore, the angle between the adsorbent and the biomass is less than 90°.
[0011] Furthermore, the method of filling the pores of biomass with adsorbent is to saturate the biomass powder with the heated adsorbent.
[0012] Furthermore, the desorption of part of the filled adsorbent is to heat the biomass adsorbed with the adsorbent to make its temperature higher than the adsorption temperature of the adsorbent, and then desorb part of the adsorbent.
[0013] Furthermore, the chemical modification of the biomass is completed by using a modifier, converting the modifier into vapor, and chemically reacting with the groups on the outer surface of the biomass micropowder that are not covered by the adsorbent in a gas phase environment.
[0014] Furthermore, the efficient biomass surface treatment process is completed by a surface treatment device; the surface treatment device includes an adsorbent heating tank, a modifier heating tank, a sand core plate, a metering feeder, a low-speed mixer, a temperature-controllable main engine, a fast-changing sand core plate and a fractionation column;
[0015] The modifier heating tank is provided with a feed port, the air inlet of the modifier heating tank is connected to the carrier gas connection port, and a carrier gas pressure gauge is installed on the pipeline between the air inlet and the carrier gas connection port; the adsorbent heating tank is provided with a feed port, the modifier inlet of the adsorbent heating tank is connected to the modifier outlet of the modifier heating tank, and a carrier gas throttle valve is installed on the pipeline connecting the modifier inlet and the modifier outlet; the adsorbent outlet of the adsorbent heating tank is connected to the adsorbent feed port of the sand core plate through a pipeline, and an adsorbent is installed on the pipeline. The material is connected to a throttle valve, the sand core plate is connected to one port of the temperature-controllable main engine, and the other port of the temperature-controllable main engine is connected to the quick-change sand core plate; the discharge port of the low-speed mixer is connected to the feed port of the metering feeder; the feed port of the temperature-controllable main engine is connected to the discharge port of the metering feeder; one end of the conveying screw arranged in the temperature-controllable main engine is connected to the transmission shaft of the motor, and a discharge port is arranged on the side wall of the temperature-controllable main engine, and the outlet of the quick-change sand core plate is connected to the inlet of the fractionating column; the fractionating column is provided with an air compressor connection port.
[0016] Further, a method for treating the surface of biomass using a surface treatment device:
[0017] Step 1, closing the discharge port, the carrier gas connection port, the carrier gas throttle valve, the adsorbent throttle valve and the air compressor connection port, placing the biomass powder to be processed into a low-speed mixer after being fully dried, and evenly filling the biomass powder to be processed into the temperature-controllable main machine through a metering feeder, a motor and a conveying screw, and after filling, closing the metering feeder;
[0018] Step 2, open the carrier gas throttle valve and the air compressor connection port, pass the carrier gas for purging, and close the carrier gas throttle valve after the purging is completed; open the adsorbent throttle valve and the air compressor connection port, control the temperature of the adsorbent heating tank to make the adsorbent boil, and enter the temperature-controlled main engine through the adsorbent throttle valve and the sand core plate, and pass through the filling layer of biomass micropowder; control the temperature of the temperature-controlled main engine, and control the pressure of the main engine and the fractionation column through the external air compressor, so that the adsorbent completes the saturated adsorption of the biomass micropowder in the temperature-controlled main engine, and the unadsorbed adsorbent passes through the quick-changing sand core plate, is condensed and recovered by the fractionation column, and is recycled; after adsorption, close the adsorbent throttle valve, increase the temperature of the temperature-controlled main engine to partially desorb the adsorbent, and the desorbed adsorbent passes through the quick-changing sand core plate, is condensed and recovered by the fractionation column, and is recycled;
[0019] Step 3: After desorption is completed, the modifier is injected into the modifier heating tank, heated to convert the modifier into steam, and the carrier gas throttle valve is opened, so that the modifier is carried by the carrier gas through the carrier gas throttle valve and the sand core plate into the temperature-controllable main engine, passes through the filling layer of the biomass micropowder, and reacts chemically with the groups on the outer surface of the biomass micropowder not covered by the adsorbent in the gas phase environment to complete the surface modification process; the unreacted modifier is condensed and recovered by the fractionation column through the quick-changing sand core plate, and can be re-added to the modifier heating tank after collection;
[0020] Step 4: After the surface modification reaction is completed, the temperature of the temperature-controllable host is increased again, and at the same time, an external air compressor is used to evacuate the adsorbate that has not yet been desorbed to completely desorb it;
[0021] Step 5: After desorption is completed, close the carrier gas throttle valve and the air compressor connection port, open the discharge port, and use the motor to drive the conveying screw to evenly discharge the processed biomass powder to obtain surface-modified biomass powder.
[0022] Technical principle of the present invention: The essence of chemical modification of biomass powder is the chemical adsorption process of biomass powder in gas phase or liquid phase, and chemical adsorption is based on physical adsorption. Biomass powder and other porous powders have complex microstructures, and the area of their outer surface (the outer surface of the powder) is much smaller than the area of the inner surface (the surface of the pores). Although biomass is generally hydrophilic, the contact angle with most solvents and modifiers is less than 90°. Affected by the interfacial tension of the curved interface and the capillary condensation phenomenon, the inner surface of the biomass pores has a stronger adsorption capacity for solvents and modifiers, and a larger surface area. Therefore, when the surface of biomass powder is treated in an ordinary homogeneous system (liquid phase or gas phase), physical adsorption is preferentially generated at the inner surface of the biomass and further capillary condensation occurs, so that a large amount of modifiers are enriched in the pore structure of the biomass powder. Because physical adsorption is the premise of chemical modification, the functional groups generated by surface modification are also mainly enriched in the pores of biomass micropowders, and only a small amount of functional groups will be formed on the outer surface of biomass micropowders. When the composite material is formed, only the functional groups on the outer surface of biomass micropowders can form physical entanglement and chemical bonding with the resin matrix, so the surface treatment often fails to achieve the expected effect. In order to improve the treatment effect, the process usually adopts the method of increasing the amount of surface modifier to make up for the lack of modification efficiency. However, biomass micropowders have strong adsorption capacity and large pore volume, and can generally adsorb more than 10% of the adsorbate to complete the pore filling. However, for cost and safety considerations, the cost-effectiveness of using more than 10% of expensive surface modifiers to treat cheap biomass micropowders is extremely low, and even not worth the cost. Therefore, the process does not have the economy and applicability, which is also the main bottleneck problem plaguing the bio-based materials industry.
[0023] In order to solve the above bottleneck problem, we first select an inert substance with poor compatibility with biomass as the adsorbent to saturate the biomass powder in a gas phase environment. The reason for choosing a gas phase environment is that any gas can be adsorbed on the surface of any solid; the reason for choosing an inert adsorbent is to avoid chemical reactions between the adsorbent and the modifier during the subsequent surface treatment process; the reason for choosing an adsorbent with poor compatibility with biomass is to facilitate the desorption of the adsorbent after surface treatment. At the same time, the contact angle between the adsorbent and the biomass is required to be slightly less than 90°, which is the prerequisite for the adsorbent to fill the pores in the biomass powder. (Additional note: Most organic solvents, including oils and alkanes, can achieve pore filling in biomass.)
[0024] After achieving saturated adsorption, the adsorption environment is changed (increasing the temperature or reducing the partial pressure of the adsorbate) to partially desorb the adsorbate adsorbed on the biomass powder. Since the contact angle between the adsorbate and the biomass is less than 90°, the attachment occurs preferentially on the inner surface of the biomass and forms pore filling, while the desorption occurs preferentially on the outer surface of the biomass powder. Only when the outer surface is desorbed and the temperature is higher and the adsorbate pressure is lower, the adsorbate filled in the pores of the biomass powder will begin to desorb. In other words, the saturated adsorption process occupies all the surfaces of the biomass powder through adsorption and pore filling, and after partial desorption, the inner surface of the biomass powder is still occupied by the adsorbate, while the outer surface is exposed.
[0025] Under the condition of partial desorption, further surface modification is completed. Because the inner surface is still occupied by the adsorbate at this time, the surface modification only occurs on the outer surface of the biomass powder. Therefore, only a small amount of modifier can be used to achieve the surface treatment effect that can only be achieved (or even not achieved) by using a large amount of modifier in a homogeneous modification environment. In order to achieve the above process, the adsorbate is required to have as low a solubility as possible for the modifier and not to react chemically with the modifier. The modifier is required to have active chemical properties and be able to complete the interfacial reaction with the outer surface of the biomass under low temperature conditions and in a short reaction time.
[0026] After the surface modification is completed, the biomass micropowder that still adsorbs a large amount of adsorbents and has functional groups connected to the outer surface needs to be fully desorbed under the conditions of heating and vacuuming. After the desorption is completed, dry biomass micropowder with only the outer surface modified can be obtained. In order to achieve the above process, the boiling point of the adsorbent is required to be moderate, that is, the temperature conditions for the chemical reaction of the modifier must be taken into account, and at the same time, it must be ensured that the adsorbent can be completely desorbed under not too high a temperature.
[0027] In the entire process described above, the adsorbent does not participate in the chemical reaction, the amount used is relatively small (relative to liquid phase modification in an organic solvent) and can be recycled. The amount of modifier used is extremely small, and only 0.01 to 0.5 wt% by mass is required to achieve a good surface modification effect. At the same time, the reaction only occurs on the outer surface of the biomass, which will not damage the structure of the biomass, and the strength of the biomass itself will not be reduced due to chemical modification. During the modification process, the biomass powder does not come into contact with any liquid phase, so there will be no agglomeration phenomenon, and no industrial wastewater will be generated. Therefore, it is a clean and environmentally friendly green process.
[0028] The present invention has the following beneficial effects:
[0029] The present invention first fills the pores of the microstructure of biomass by adsorption, and uses the capillary condensation of the adsorbate to occupy the inner surface of the biomass; then a small amount of the adsorbate is desorbed to expose the outer surface of the biomass, and the chemical modification of the biomass is completed by gas phase reaction. This process can achieve excellent surface treatment effects using a very small amount of modifier, so a relatively expensive but effective modifier can be selected to perform surface modification on the biomass; the process only uses a small amount of organic solvent as an adsorbate, and it can be recycled; it can be combined with supercritical extraction and supercritical reaction technology to efficiently remove pesticide residues and impurities in the biomass, further improving the safety and performance of bio-based material products. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 Schematic diagram of biomass surface treatment equipment using adsorption occupancy method; in the figure, 1 is an adsorbent heating device, 2 is a modifier heating device, 3 is a carrier gas connection port, 4 is an adsorbent pressure gauge, 5 is a carrier gas pressure gauge, 6 is a carrier gas throttle valve, 7 is an adsorbent throttle valve; 8 is a motor, 9 is a sand core plate, 10 is a metering feeder, 11 is a low-speed mixer, 12 is a conveying screw, 13 is a temperature-controllable main engine, 14 is a discharge port, 15 is a quick-change sand core plate, 16 is a fractionation column, and 17 is an air compressor connection port;
[0031] Figure 2 XPS full spectrum of untreated biomass powder;
[0032] Figure 3 C1s spectrum of untreated biomass powder;
[0033] Figure 4 XPS full spectrum of biomass powder acylated with decanoyl chloride;
[0034] Figure 5 C1s spectrum of biomass micropowder acylated with decanoyl chloride;
[0035] Figure 6 Scanning electron microscope photo of biomass powder after surface treatment;
[0036] Figure 7 XPS full spectrum of coupled treated biomass powder;
[0037] Figure 8 C1s spectrum of coupled treated biomass micropowder. DETAILED DESCRIPTION
[0038] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clearly understood, the spirit of the contents disclosed by the present invention will be described in detail below. After understanding the embodiments of the contents of the present invention, any technician in the relevant technical field can change and modify them according to the techniques taught by the contents of the present invention without departing from the spirit and scope of the contents of the present invention.
[0039] The exemplary embodiments of the present invention and the description thereof are used to explain the present invention, but are not intended to limit the present invention.
[0040] Example 1
[0041] The discharge port 14, carrier gas connection port 3, carrier gas throttle valve 6, adsorbent throttle valve 7 and air compressor connection port 17 are closed, and the 600-mesh rice husk to be processed is fully dried and placed in the low-speed mixer 11. The biomass powder to be processed is evenly filled in the temperature-controllable main machine 13 through the metering feeder 10, motor 8 and conveying screw 12, and the filling density is 0.95g / cm 3 , the biomass powder occupies about 70% of the volume of the host. Open the carrier gas throttle valve 6 and the air compressor connection port 17, and introduce compressed air for purging. After the purging is completed, close the carrier gas throttle valve 6. A mixture of n-octane and cyclohexane (the mass ratio of n-octane to cyclohexane is 3:1) is selected as the adsorbent. Open the adsorbent throttle valve 7 and the air compressor connection port 17, and control the temperature of the adsorbent heating tank 1 to 110°C to make the mixed adsorbent boil. The adsorbent n-octane and cyclohexane enter the temperature-controlled host 13 through the adsorbent throttle valve 7 and the sand core plate 9, and pass through the filling layer of the biomass powder. The temperature of the temperature-controlled host 13 is controlled to 120°C, and the pressure of the temperature-controlled host 13 and the fractionation column 16 is controlled to 0.3 bar through the external air compressor, so that the adsorbent completes the saturated adsorption of the biomass powder in the space of the host, and samples are taken for detection. At this time, the adsorption amount of the biomass powder is about 8.5% of the biomass mass. The unadsorbed adsorbate passes through the quickly replaceable sand core plate 15, is condensed and recovered by the fractionation column, and is recycled. After the adsorption lasts for 30 minutes, the adsorbate throttle valve 7 is closed, and the temperature of the temperature-controllable host 13 is increased to 125°C to partially desorb the adsorbate, and samples are taken for testing. When the adsorption amount of the sample drops to 8.0% of the total mass of the biomass, the temperature of the host is quickly reduced to 95°C.
[0042] Decanoyl chloride is selected as a modifier, and the modifier is injected into the modifier heating tank 2, heated to 115°C to convert the modifier into steam, and the carrier gas throttle valve 6 is opened to allow the modifier to enter the temperature-controlled main engine 13 through the carrier gas throttle valve 6 and the sand core plate 9 under the carrying of the compressed air dried at the same temperature, pass through the filling layer of the biomass micropowder, and react chemically with the groups on the outer surface of the biomass micropowder that are not covered by the adsorbent in the gas phase environment. At this time, the decanoyl chloride reacts with the hydroxyl groups on the outer surface of the biomass, and a carbon chain of ten carbon atoms is connected on the surface of the biomass, so that the outer surface of the biomass is changed from hydrophilic to hydrophobic. The reaction lasts for 45 minutes, and the unreacted decanoyl chloride passes through the sand core plate (device 15) that can be quickly replaced, and is condensed and recovered by the fractionation column. After collection, it can be re-added to the modifier heating tank 2 for full utilization.
[0043] After the surface modification reaction is completed, the temperature of the temperature-controllable main engine 13 is raised to 130°C, and at the same time, an external air compressor is used to evacuate the main engine so that the vacuum degree in the main engine is reduced to below 15Pa, so that the adsorbent that has not yet been desorbed is completely desorbed. During this process, the temperature of the main engine should not be too high to avoid the functional groups generated by the surface treatment from falling off due to heat. The rotation speed and reverse frequency of the conveying screw can be accelerated to make the biomass powder turn in the main engine, accelerating the desorption of the adsorbent. After the desorption is completed, the carrier gas throttle valve 6 and the air compressor connection port 17 are closed, and the discharge port (device 14) is opened. The conveying screw 12 is driven by the motor 8 to convey the treated biomass powder evenly to discharge the material, that is, dry modified biomass powder with a hydrophobic surface is obtained. The mass of the modifier decanoyl chloride consumed during the entire surface treatment process is approximately 0.2% of the mass of the biomass.
[0044] XPS full spectrum and C of biomass powder before acylation 1s The spectra are Figure 2 and Figure 3 As shown, the XPS spectrum of biomass powder before acylation and C 1s The spectra are Figure 4 and Figure 5 As shown. Figure 3 and Figure 5From the shape of the C1s spectrum, it can be seen that after acylation, the absorption peaks at the chemical shift corresponding to the C atom in the CC single bond and the chemical shift corresponding to the C atom in C=O have increased, which indicates that after acylation, a longer fatty chain is indeed connected to the interface of the biomass through the chemical bonding of the ester bond. In addition, before acylation, the C element content on the biomass surface is 62.74%, and the O element content is 34.31%, while after acylation, the C element content on the surface of the biomass sample is 74.0%, and the O element content is 24.66%. Considering that the increase in the C element content is due to the connection of a long fatty chain consisting of ten carbon atoms, it can be judged that the interface compatibility of the biomass micropowder modified by acylation with polyolefin resins such as PE and PP will be significantly enhanced.
[0045] Example 2
[0046] The discharge port 14, the carrier gas connection port 3, the carrier gas throttle valve 6, the adsorbent throttle valve 7 and the air compressor connection port 17 are closed, and the 800-mesh corn stalk powder to be processed is fully dried and placed in the low-speed mixer 11. The biomass powder to be processed is evenly filled in the temperature-controllable host 13 through the metering feeder 10, the motor (device 8) and the conveying screw 12, and the filling density is 0.90g / cm 3 , the biomass powder occupies about 60% of the volume of the host. Open the carrier gas throttle valve 6 and the air compressor connection port 17, and introduce compressed air for purging. After the purging is completed, close the carrier gas throttle valve 6. A mixture of n-hexane and petroleum ether (the mass ratio of n-hexane to cyclohexane is 4:1) is selected as the adsorbent. Open the adsorbent throttle valve 7 and the air compressor connection port 17, and control the temperature of the adsorbent heating tank 1 to 100°C to make the mixed adsorbent boil. The adsorbent n-octane and petroleum ether enter the temperature-controlled host 13 through the adsorbent throttle valve 7 and the sand core plate 9, and pass through the filling layer of the biomass powder. The temperature of the temperature-controlled host 13 is controlled to 110°C, and the pressure of the temperature-controlled host 13 and the fractionation column 16 is controlled to 0.5 bar by the external air compressor, so that the adsorbent completes the saturated adsorption of the biomass powder in the space of the host, and samples are taken for detection. At this time, the adsorption amount of the biomass powder is about 9.5% of the biomass mass. The unadsorbed adsorbate passes through the quickly replaceable sand core plate 15, is condensed and recovered by the fractionation column, and is recycled. After the adsorption lasts for 30 minutes, the adsorbate throttle valve 7 is closed, the temperature of the temperature-controllable host 13 is increased to 120°C, and the pressure of the host is reduced to 0.1 bar to partially desorb the adsorbate, and samples are taken for testing. When the adsorption amount of the sample drops to 8.5% of the total mass of the biomass, the temperature of the host is quickly reduced to 60°C.
[0047] Select epichlorohydrin as the modifier, inject the modifier into the modifier heating tank 2, heat it to 75°C to convert the modifier into steam, open the carrier gas throttle valve 6 to allow the modifier to enter the temperature-controlled main engine 13 through the carrier gas throttle valve 6 and the sand core plate 9 under the carry of dry nitrogen at the same temperature, pass through the filling layer of biomass micropowder, and react chemically with the groups on the outer surface of the biomass micropowder that are not covered by the adsorbent in the gas phase environment. At this time, epichlorohydrin reacts with the hydroxyl groups on the outer surface of the biomass, removes a molecule of hydrogen chloride, and forms active epoxy functional groups on the outer surface of the biomass. The reaction lasts for 25 minutes, and the unreacted epichlorohydrin passes through the sand core plate 15 that can be quickly replaced, and is condensed and recovered by the fractionation column. After collection, it can be re-added to the modifier heating tank 2 for full utilization.
[0048] After the surface modification reaction is completed, the temperature of the temperature-controllable main engine 13 is raised to 110°C, and at the same time, an external air compressor is used to evacuate the main engine so that the vacuum degree in the main engine is reduced to below 10Pa, so that the adsorbent that has not yet been desorbed is completely desorbed. During this process, the temperature of the main engine should not be too high to avoid the functional groups generated by the surface treatment from falling off due to heat. The rotation speed and reverse frequency of the conveying screw can be accelerated to make the biomass powder turn in the main engine, accelerating the desorption of the adsorbent. After the desorption is completed, the carrier gas throttle valve 6 and the air compressor connection port 17 are closed, the discharge port 14 is opened, and the conveying screw 12 is driven by the motor 8 to convey the treated biomass powder evenly to discharge the material, that is, dry modified biomass powder with highly active surface is obtained. The mass of the modifier epichlorohydrin consumed during the entire surface treatment process is about 0.4% of the mass of the biomass.
[0049] The scanning electron microscope photos of the modified biomass powder are as follows: Figure 6 shown.
[0050] 30 parts of biomass micropowder before and after modification and 70 parts of polylactic acid were melt-extruded and injection-molded into specimens to test their tensile strength and impact strength. The experimental results showed that the tensile strength of the bio-based composite material prepared from the modified biomass micropowder increased by 32.4% to 33.6MPa, and the impact strength increased by 22.7% to 46.3J / m.
[0051] Example 3
[0052] The discharge port 14, the carrier gas connection port 3, the carrier gas throttle valve 6, the adsorbent throttle valve 7 and the air compressor connection port 17 are closed, and the 1200-mesh palm residue powder to be treated is fully dried and placed in the low-speed mixer 11. The biomass powder to be treated is evenly filled in the temperature-controllable main machine 13 through the metering feeder 10, the motor (device 8) and the conveying screw 12, and the filling density is 1.0 g / cm 3 , biomass powder occupies about 60% of the volume of the host.
[0053] Select supercritical carbon dioxide at 50°C and 20MPa as the carrier gas, open the carrier gas throttle valve 6 and the air compressor connection port 17, and continue to introduce supercritical carbon dioxide for 30 minutes to perform supercritical extraction on the palm micropowder to remove the rich organic components and pesticide residues in the palm micropowder.
[0054] Select n-hexane as the adsorbent. Open the adsorbent throttle valve 7 and the air compressor connection port 17, control the temperature of the adsorbent heating tank 1 to 80°C to make the mixed adsorbent boil. The adsorbent n-octane and petroleum ether enter the temperature-controlled main engine 13 through the adsorbent throttle valve 7 and the sand core plate 9, and pass through the filling layer of biomass micropowder. The temperature of the temperature-controlled main engine 13 is controlled to 70°C, and the pressure of the temperature-controlled main engine 13 and the fractionation column 16 is controlled to 0.4 bar through the external air compressor, so that the adsorbent completes the saturated adsorption of the biomass micropowder in the space of the main engine, and samples are taken for detection. At this time, the adsorption amount of the biomass micropowder is about 7.6% of the mass of the biomass. The unadsorbed adsorbent passes through the sand core plate 15 that can be quickly replaced, and is condensed and recovered by the fractionation column for recycling. After adsorption lasts for 40 minutes, the adsorbate throttle valve 7 is closed, the temperature of the temperature-controllable host 13 is increased to 90°C, and the pressure of the host is reduced to 0.3 bar to partially desorb the adsorbate. Samples are taken for testing. When the adsorption amount of the sample drops to 6.5% of the total mass of the biomass, the temperature of the host is quickly reduced to 50°C.
[0055] Silane coupling agent A-171 is selected as a modifier, and the modifier is injected into the modifier heating tank 2, and supercritical carbon dioxide at 50°C and 22MPa is introduced as a carrier gas. The carrier gas throttle valve 6 is opened to allow the silane coupling agent A-171 to enter the temperature-controlled main engine 13 through the carrier gas throttle valve 6 and the sand core plate 9 under the supercritical carbon dioxide, penetrate the filling layer of the biomass micropowder, and react chemically with the groups on the outer surface of the biomass micropowder not covered by the adsorbent in the supercritical environment, and introduce double bond functional groups on the outer surface of the biomass. The reaction lasts for 15 minutes, and the unreacted silane coupling agent A-171 is separated and recovered after decompression, and re-added to the modifier heating tank 2 for full utilization.
[0056] After the surface modification reaction is completed, stop the input of supercritical carbon dioxide. Raise the temperature of the temperature-controllable main engine 13 to 110°C, and use an external air compressor to evacuate the main engine to reduce the vacuum degree to below 10Pa, so that the adsorbent that has not yet been desorbed is completely desorbed. In this process, the rotation speed and reverse frequency of the conveying screw are accelerated to make the biomass powder flip in the main engine, accelerating the desorption of the adsorbent. After the desorption is completed, close the carrier gas throttle valve 6 and the air compressor connection port 17, open the discharge port 14, and drive the conveying screw 12 through the motor 8 to transport the treated biomass powder evenly to discharge, that is, to obtain dry modified biomass powder with highly active surface. The mass of the modifier silane coupling agent consumed during the entire surface treatment process is approximately 0.06% of the mass of the biomass.
[0057] The full spectrum and C1s spectrum of the X-ray photoelectron spectrum of the biomass powder sample after coupling treatment are shown as follows: Figure 7 and Figure 8 As shown, since the detection depth of the XPS test is only 4 to 10 nm, it can more effectively characterize the composition and functional group changes on the surface of the biomass micropowder sample before and after modification compared to the infrared spectrum test. From the shape of the XXC1s spectrum in Figure XX, it can be seen that after the coupling treatment, the absorption peaks of the chemical shift corresponding to the C atom in the CC single bond are all enhanced. At the same time, the changes in the element content show that the C element content on the biomass surface before the coupling treatment is 62.74%, the O element content is 34.31%, and there is no Si element. After the coupling treatment, the C element content on the surface of the biomass sample is 65.59%, the O element content is 28.00%, and the Si element content is as high as 4.76%. The above changes in element content strongly prove that after the coupling treatment, a surface covering layer cross-linked by -O-Si-O-bonds between silane coupling agents is indeed formed on the surface of the biomass micropowder. Only in this way can a chemical modification with a Si element content of up to 4.76% be formed on the surface of the biomass.
Claims
1. An efficient biomass surface treatment process, characterized in that It is carried out as follows: The pores of the biomass are filled with adsorbents, and then the filled adsorbents are desorbed to expose the outer surface of the biomass, thereby chemically modifying the biomass, thereby completing the efficient biomass surface treatment.
2. An efficient biomass surface treatment process according to claim 1, characterized in that The biomass is corn straw powder, rice husk powder, reed powder, palm peel powder, bagasse powder, soybean meal powder, bamboo powder or wood powder with a mesh size of 200 to 1600.
3. An efficient biomass surface treatment process according to claim 1, characterized in that The adsorbent is one or more of alkanes, cycloalkanes, lipids, naphthalene and petroleum ether.
4. An efficient biomass surface treatment process according to claim 1 or 3, characterized in that The alkanes are n-pentane, n-hexane or n-octane; the cycloalkanes are cyclohexane or cyclopentane; and the lipids are ethyl acetate or butyl acetate.
5. An efficient biomass surface treatment process according to claim 1 or 3, characterized in that The angle between the adsorbent and the biomass is less than 90 degrees.
6. The efficient biomass surface treatment process according to claim 1, characterized in that The method of filling the pores of biomass with adsorbent is to saturate the biomass powder with the heated adsorbent.
7. The efficient biomass surface treatment process according to claim 1, characterized in that The method of desorbing part of the adsorbent is to heat the biomass adsorbed with the adsorbent to make its temperature higher than the adsorption temperature of the adsorbent, and then desorb part of the adsorbent.
8. The efficient biomass surface treatment process according to claim 1, characterized in that The chemical modification of biomass is completed by using a modifier, converting the modifier into vapor, and chemically reacting with the groups on the outer surface of the biomass micropowder that are not covered by the adsorbent in a gas phase environment.
9. The efficient biomass surface treatment process according to claim 1, characterized in that The highly efficient biomass surface treatment process is completed by a surface treatment device; the surface treatment device comprises an adsorbent heating tank (1), a modifier heating tank (2), a sand core plate (9), a metering feeder (10), a low-speed mixer (11), a temperature-controllable main machine (13), a fast-changing sand core plate (15) and a fractionation column (16); The modifier heating tank (2) is provided with a feed port, the air inlet of the modifier heating tank (2) is connected to a carrier gas connection port (3), and a carrier gas pressure gauge (5) is installed on the pipeline between the air inlet and the carrier gas connection port (3); the adsorbent heating tank (1) is provided with a feed port, the modifier inlet of the adsorbent heating tank (1) is connected to the modifier outlet of the modifier heating tank (2), and a carrier gas throttle valve (6) is installed on the pipeline connecting the modifier inlet and the modifier outlet; the adsorbent outlet of the adsorbent heating tank (1) is connected to the adsorbent feed port of the sand core plate (9) through a pipeline, and an adsorbent throttle valve (7) is installed on the pipeline; the sand core plate (9) is connected to the adsorbent outlet of the sand core plate (9) through a pipeline. One port of the temperature-controllable main machine (13) is connected, and the other port of the temperature-controllable main machine (13) is connected to the quick-change sand core plate (15); the discharge port of the low-speed mixer (11) is connected to the feed port of the metering feeder (10); the feed port of the temperature-controllable main machine (13) is connected to the discharge port of the metering feeder (10); one end of the conveying screw (12) arranged in the temperature-controllable main machine (13) is connected to the transmission shaft of the motor (8), a discharge port (14) is arranged on the side wall of the temperature-controllable main machine (13), the outlet of the quick-change sand core plate (15) is connected to the inlet of the fractionating column (16); the fractionating column (16) is provided with an air compressor connection port (17).
10. An efficient biomass surface treatment process according to claim 9, characterized in that Method for treating biomass surface using surface treatment equipment: Step 1, closing the discharge port (14), the carrier gas connection port (3), the carrier gas throttle valve (6), the adsorbent throttle valve (7) and the air compressor connection port (17), placing the biomass powder to be treated in a low-speed mixer (11) after being fully dried, and uniformly filling the biomass powder to be treated in a temperature-controllable main machine (13) through a metering feeder (10), a motor (8) and a conveying screw (12), and after filling, closing the metering feeder (10); Step 2: Open the carrier gas throttle valve (6) and the air compressor connection port (17), introduce the carrier gas for purging, and close the carrier gas throttle valve (6) after the purging is completed; open the adsorbent throttle valve (7) and the air compressor connection port (17), control the temperature of the adsorbent heating tank (1) to make the adsorbent boil, and enter the temperature-controllable main engine (13) through the adsorbent throttle valve (7) and the sand core plate (9), and pass through the filling layer of biomass micropowder; control the temperature of the temperature-controllable main engine (13) through the external air compressor to control the main engine The pressure of the machine (13) and the fractionation column (16) is increased so that the adsorbent completes saturated adsorption of the biomass powder in the temperature-controllable main machine (13), and the unadsorbed adsorbent passes through the quick-changing sand core plate (15) and is condensed and recovered by the fractionation column (16) for recycling; after adsorption, the adsorbent throttle valve (7) is closed, and the temperature of the temperature-controllable main machine (13) is increased to partially desorb the adsorbent, and the desorbed adsorbent passes through the quick-changing sand core plate (15) and is condensed and recovered by the fractionation column (16) for recycling; Step 3: After desorption is completed, the modifier is injected into the modifier heating tank (2), heated to convert the modifier into steam, and the carrier gas throttle valve (6) is opened, so that the modifier is carried by the carrier gas through the carrier gas throttle valve (6) and the sand core plate (9) into the temperature-controllable main engine (13), passes through the filling layer of the biomass micropowder, and reacts chemically with the groups on the outer surface of the biomass micropowder not covered by the adsorbent in the gas phase environment, thereby completing the surface modification process; the unreacted modifier is condensed and recovered by the fractionation column (16) through the quick-changing sand core plate (15), and can be re-added to the modifier heating tank (2) after being collected; Step 4: After the surface modification reaction is completed, the temperature of the temperature-controllable main unit (13) is increased again, and at the same time, an external air compressor is used to evacuate the air to completely desorb the adsorbate that has not yet been desorbed; Step 5: After desorption is completed, close the carrier gas throttle valve (6) and the air compressor connection port (17), open the discharge port (14), and use the motor (8) to drive the conveying screw (12) to convey the treated biomass micropowder to be evenly discharged to obtain surface-modified biomass micropowder.