Method for driving biomass to deoxidize and simultaneously preparing hydrogen peroxide by water microdroplets

Abstract

The invention discloses a method for driving biomass to deoxidize and simultaneously preparing hydrogen peroxide by water droplets, which comprises the following steps of: spraying the water droplets with the diameter of less than or equal to 20 microns onto the surface of a biomass material, and collecting spraying liquid dripping from the surface of the biomass material; breaking the spraying liquid into micro-drops with the diameter smaller than or equal to 20 microns, spraying the micro-drops onto the surface of the biomass material again, and repeating the operation until the collected spraying liquid contains hydrogen peroxide with the target concentration. The problems that an existing hydrogen peroxide preparation method and an existing biomass deoxidation method are large in energy consumption, serious in pollution and the like can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen peroxide preparation, and more specifically to a method for preparing hydrogen peroxide while driving biomass deoxygenation with water droplets. Background Art

[0002] Hydrogen peroxide is a cleaning chemical with an increasing demand and is widely used in various fields of industry. At present, there are four main methods for preparing hydrogen peroxide in industry: direct synthesis method (DSHP), electrochemical oxidation method, isopropanol oxidation method, and anthraquinone method. However, the preparation process is energy-intensive and risky, and the preparation of some of these methods will cause great harm to the environment. Finding a green, low-energy, and low-risk production process hydrogen peroxide preparation method is an inevitable trend under the concept of green sustainable production.

[0003] Jae Kyoo Lee et al. found that pure water can be atomized into droplets (1 μm to 20 μm in diameter) and sprayed onto a solid surface to spontaneously generate H2O2. Jae Kyoo Lee et al. believed that the generated hydrogen peroxide was formed by the recombination of hydroxyl radicals (OH), where OH is formed by the OH on the surface of or near the water droplets. - It is produced by losing electrons. Bolei Chen et al. subsequently used isotope labeling to prove that hydrogen peroxide is produced when water droplets come into contact with hydroxyl groups on the solid surface, that the hydroxyl groups on the solid surface participate in the generation of H2O2, and that the density of hydroxyl groups directly affects the yield of H2O2.

[0004] Biomass deoxygenation and upgrading refers to the process of reducing the oxygen content in biomass by physical, chemical or biological methods to increase its energy density and fuel quality. This process increases the calorific value of biomass fuel, making it more suitable for combustion or conversion into other types of energy. Through biomass deoxygenation and upgrading, renewable resources can be used more effectively and the development of sustainable energy can be promoted. At present, the main method of deoxygenating biomass is baking. This method has high energy consumption, high equipment requirements, and the baking process will cause the loss of biomass raw materials. Due to these shortcomings, baking deoxygenation cannot be widely used.

[0005] Therefore, it is necessary to study the deoxygenation and upgrading of biomass in the case where water droplets contact solids to produce hydrogen peroxide, so that while water droplets spontaneously generate hydrogen peroxide, biomass as a solid substrate can be deoxygenated and upgraded to expand the economic benefits of the process. Summary of the invention

[0006] To this end, the technical problem to be solved by the present invention is to provide a method for preparing hydrogen peroxide by deoxygenating biomass using water droplets, so as to solve the problems of high energy consumption and serious pollution in the existing hydrogen peroxide preparation method and biomass deoxygenation method.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets, comprising spraying water droplets with a diameter of less than or equal to 20 μm onto the surface of a biomass material, collecting the spray liquid dripping from the surface of the biomass material, breaking the spray liquid into droplets with a diameter of less than or equal to 20 μm and spraying them onto the surface of the biomass material again, and repeating the above operation until the collected spray liquid contains a target concentration of hydrogen peroxide.

[0009] In the above-mentioned method for preparing hydrogen peroxide by deoxygenating biomass with water droplets, in step (1), the material is one or a combination of two or more of pine wood chips, paulownia wood chips or willow bend wood chips; the oxygen content of the biomass material is 33-43%. The type, surface roughness and oxygen content of the biomass material will affect the yield of hydrogen peroxide; compared with paulownia and willow bend wood, the present invention selects pine wood chips with an oxygen content of 33-43% as the biomass material for water droplet spraying, and the surface roughness is moderate, and the hydrogen peroxide yield is higher.

[0010] The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets comprises the following steps:

[0011] Step (1), pretreating the biomass material to obtain an activated biomass material;

[0012] Step (2), using activated biomass material to prepare a biomass substrate;

[0013] Step (3), using a droplet spraying device to spray water droplets onto the surface of the biomass substrate, and collecting the spraying liquid dripping from the biomass substrate;

[0014] Step (4), atomizing the spraying liquid into water droplets and re-spraying the water droplets onto the surface of the biomass substrate for cyclic droplet spraying until the liquid dripping from the biomass substrate contains a target concentration of hydrogen peroxide.

[0015] In the above-mentioned method for simultaneously preparing hydrogen peroxide by deoxygenating biomass with water droplets, in step (1), the pretreatment of the biomass material comprises the following steps:

[0016] Step (1-1), placing the biomass material in a sodium hydroxide ethanol solution and soaking it at a constant temperature, washing it with deionized water until it is neutral after soaking, and then drying it to obtain a primary treated biomass material;

[0017] Step (1-2), placing the primary treated biomass material in a calcium hydroxide solution and soaking it at a constant temperature, and drying it after soaking to obtain a secondary treated biomass material;

[0018] Step (1-3), placing the secondary treated biomass material in an atmospheric pressure dielectric barrier discharge device for surface plasma treatment, and obtaining an activated biomass material after the treatment.

[0019] The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass with water droplets, in step (1-1), the concentration of the sodium hydroxide ethanol solution is 1-1.5 g / L, the constant temperature soaking conditions are: soaking at 50-55° C. for 18-24 hours; the drying conditions are: drying at 60-70° C. for 8-12 hours; the concentration of the sodium hydroxide ethanol solution, the soaking temperature, the soaking time and the drying conditions will affect the treatment effect of the primary treatment; under the above-mentioned primary treatment conditions, the present invention can not only effectively remove lignin from the biomass material and significantly increase the hydroxyl density on the surface of the biomass material, but also ensure that the organizational structure of the biomass material is not destroyed, so that the surface roughness is maintained in a relatively ideal state, providing conditions for subsequent secondary treatment to achieve a better activation effect;

[0020] In step (1-2), the concentration of the calcium hydroxide solution is 1.5-2.0 g / L, and the constant temperature soaking condition is: soaking at 50-55° C. for 6-8 hours; the drying condition is: drying at 60-70° C. for 8-12 hours; if the calcium hydroxide concentration is too high, or the soaking temperature exceeds the above range, crystalline powder will be attached to the surface of the biomass material after the secondary treatment, affecting the effect of subsequent water droplet spraying to produce hydrogen peroxide; and if the soaking condition exceeds the above range, it may also lead to incomplete soaking, so that the subsequent water droplet spraying produces hydrogen peroxide with unstable high and low yields; compared with other strong alkaline solutions such as sodium hydroxide, the present invention selects a calcium hydroxide solution with a concentration of 1.5-2.0 g / L for constant temperature soaking. Under the above soaking and drying conditions, the alkaline environment on the surface of the biomass material can be significantly improved without destroying the organizational structure of the biomass material, which is conducive to promoting the reaction process of spontaneously producing hydrogen peroxide by water droplet spraying, and can significantly reduce the decomposition of hydrogen peroxide, thereby facilitating the increase of the yield of hydrogen peroxide;

[0021] In step (1-3), the working power of the dielectric barrier discharge device is 4-5kW, the sample feeding speed is 10-15mm / s, and the surface plasma treatment is repeated at least twice. The surface plasma treatment is placed at the last stage of the "three-stage treatment" for treatment: on the one hand, the surface plasma treatment will not destroy the alkaline environment formed on the surface of the biomass after the secondary treatment; on the other hand, the surface plasma treatment of the biomass material after the primary treatment (delignification) has a more significant effect on improving its hydroxyl density.

[0022] In the above-mentioned method for simultaneously preparing hydrogen peroxide by deoxygenating biomass with water droplets, in step (1-1), the concentration of the sodium hydroxide ethanol solution is 1 g / L, the constant temperature soaking condition is: soaking at 50° C. for 24 hours; the drying condition is: drying at 60° C. for 12 hours;

[0023] In step (1-2), the concentration of the calcium hydroxide solution is 1.5 g / L, and the constant temperature soaking condition is: soaking at 50° C. for 6 h; the drying condition is: drying at 60° C. for 12 h;

[0024] In step (1-3), the operating power of the dielectric barrier discharge device is 4.5 kW, the injection speed is 10 mm / s, and the surface plasma treatment is repeated twice.

[0025] In the above method of water droplets driving biomass deoxygenation and simultaneously preparing hydrogen peroxide, in step (2), the method for preparing the biomass substrate is:

[0026] Step (2-1), processing the activated biomass material into an isosceles triangle plate, wherein the height and base of the isosceles triangle are equal;

[0027] Step (2-2), four isosceles triangle plates are spliced ​​into a quadrangular pyramid to form a biomass substrate.

[0028] In the above-mentioned method for simultaneously preparing hydrogen peroxide by deoxygenating biomass with water droplets, in step (3), the droplet spraying device comprises a high-pressure air pump, a liquid injection pump and a liquid droplet nozzle; the fluid outlet end of the high-pressure air pump is fluidly connected to the sheath tube fluid inlet end of the liquid droplet nozzle, and the fluid outlet end of the liquid injection pump is fluidly connected to the inner tube fluid inlet end of the liquid droplet nozzle; the sheath tube is sleeved on the inner tube and the central axis of the sheath tube coincides with the inner tube, and the length of the sheath tube is greater than that of the inner tube; the fluid outlets of the sheath tube and the inner tube are both facing the surface of the biomass substrate;

[0029] The air flow rate of the high-pressure air pump is 1-1.5 L / min, and the liquid flow rate of the liquid injection pump is 100-120 μL / min; the distance between the fluid outlet of the sheath tube and the fluid outlet of the inner tube is 0.5-0.8 mm; the distance between the outlet of the liquid droplet nozzle and the surface of the biomass substrate is 80-100 mm; the outer diameter of the sheath tube is 0.6 mm, and the wall thickness is 0.03 mm; the outer diameter of the inner tube is 0.12 mm, and the wall thickness is 0.015 mm; the material of the sheath tube and the inner tube is polyimide.

[0030] In the above method of water droplet-driven biomass deoxygenation and simultaneous preparation of hydrogen peroxide, in step (3) and step (4), the biomass substrate is removed and dried after spraying for 5 to 10 minutes, and then reused for spraying after drying until the deoxygenation target is achieved.

[0031] In the above-mentioned method for simultaneously preparing hydrogen peroxide by deoxygenating biomass with water droplets, in step (1), the biomass is pine wood chips; the oxygen content of the pine wood chips is 43%; and the pretreatment of the biomass material comprises the following steps:

[0032] Step (1-1), placing the biomass material in a sodium hydroxide ethanol solution with a concentration of 1 g / L at a constant temperature of 50° C. for 24 hours, washing with deionized water until neutral after the soaking, and then drying at 60° C. for 12 hours to obtain a primary treated biomass material;

[0033] Step (1-2), placing the primary treated biomass material in a calcium hydroxide solution with a concentration of 1.5 g / L at a constant temperature of 50° C. for 6 hours, and drying at 60° C. for 12 hours after the soaking to obtain a secondary treated biomass material;

[0034] Step (1-3), placing the secondary treated biomass material in an atmospheric pressure dielectric barrier discharge device under working conditions of a working power of 4.5 kW and a sample feed speed of 10 mm / s for surface plasma treatment twice, and obtaining an activated biomass material after the treatment;

[0035] In step (2), the method for preparing the biomass substrate is:

[0036] Step (2-1), processing the activated biomass material into an isosceles triangle plate, wherein the height and base of the isosceles triangle are equal;

[0037] Step (2-2), splicing four isosceles triangle plates into a quadrangular pyramid to form a biomass substrate;

[0038] In step (3), the droplet spraying device includes a high-pressure air pump, a liquid injection pump and a liquid droplet nozzle; the fluid outlet end of the high-pressure air pump is fluidly connected to the sheath tube fluid inlet end of the liquid droplet nozzle, and the fluid outlet end of the liquid injection pump is fluidly connected to the inner tube fluid inlet end of the liquid droplet nozzle; the sheath tube is sleeved on the inner tube and the central axis of the sheath tube coincides with the inner tube, and the length of the sheath tube is greater than that of the inner tube; the fluid outlets of the sheath tube and the inner tube are both facing the surface of the biomass substrate;

[0039] The air flow rate of the high-pressure air pump is 1L / min, and the liquid flow rate of the liquid injection pump is 100μL / min; the distance between the fluid outlet of the sheath tube and the fluid outlet of the inner tube is 0.5mm; the distance between the outlet of the liquid droplet nozzle and the surface of the biomass substrate is 100mm; the outer diameter of the sheath tube is 0.6mm, and the wall thickness is 0.03mm; the outer diameter of the inner tube is 0.12mm, and the wall thickness is 0.015mm; the materials of the sheath tube and the inner tube are both polyimide;

[0040] In step (3) and step (4), the biomass substrate is removed and dried after spraying for 5 minutes, and then reused for spraying after drying until the deoxygenation target is achieved.

[0041] The technical solution of the present invention achieves the following beneficial technical effects:

[0042] 1. The method of the present invention for simultaneously preparing hydrogen peroxide by driving biomass deoxygenation with water droplets, utilizing the ability of water droplets to spontaneously generate hydrogen peroxide on the surface of solid biomass materials, repeatedly spraying water droplets with a diameter of less than or equal to 20 μm onto the surface of the biomass materials, and the water droplets can combine with hydroxyl radicals on the surface of the solid biomass materials to generate hydrogen peroxide, while achieving the purpose of deoxygenating the solid biomass materials. The present invention realizes the synchronous deoxygenation of biomass materials while preparing hydrogen peroxide, and the whole process has low energy consumption and no pollution, and has obvious economic advantages compared with the existing hydrogen peroxide preparation method and biomass deoxygenation method.

[0043] 2. The present invention sequentially uses sodium hydroxide ethanol solution soaking treatment, calcium hydroxide solution soaking treatment and surface plasma treatment to activate biomass materials, which can significantly improve the reaction efficiency of hydroxyl groups on the surface of biomass materials and water droplets, thereby facilitating the improvement of hydrogen peroxide yield. It is found in the experiment that the pretreatment method and treatment sequence of biomass materials have an important influence on the hydrogen peroxide yield. If the treatment sequence of the above pretreatment is changed, the treatment conditions of each treatment method cannot achieve the ideal activation effect, and the biomass material tissue is easily destroyed, and even the problem of biomass material fragmentation occurs. The present invention can significantly improve the yield of hydrogen peroxide spontaneously generated by water droplets with a diameter less than or equal to 20 μm and biomass materials according to the treatment sequence of sodium hydroxide ethanol solution soaking, calcium hydroxide solution soaking and plasma treatment, and can achieve the purpose of deoxygenating biomass materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic structural diagram of a droplet spray system in an embodiment of the present invention;

[0045] Figure 2 The results of the sample obtained after a single experiment of droplet spraying in the embodiment of the present invention were tested by hydrogen peroxide test paper;

[0046] Figure 3 The sample obtained after the droplet spraying experiment in the embodiment of the present invention was repeated 15 times was tested by hydrogen peroxide test paper;

[0047] Figure 4 The sample obtained after soaking the pine wood chips with the large droplets in the embodiment of the present invention was tested with hydrogen peroxide test paper;

[0048] Figure 5a The liquid obtained after soaking the pine wood chips with a large droplet for 20 minutes and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0049] Figure 5b The liquid obtained after soaking the pine wood chips with droplet spray for 20 minutes (repetition number 1) and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0050] Figure 5c The liquid obtained after soaking the pine wood chips with large droplets for 60 minutes and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0051] Figure 5d The liquid obtained after soaking the pine wood chips with droplet spray for 60 minutes (repeated times 3) and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0052] Figure 5e The liquid obtained after soaking the pine wood chips with large droplets for 100 minutes and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0053] Figure 5f The liquid obtained after soaking the pine wood chips with droplet spray for 100 minutes (repeated times 5) and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0054] Figure 5g The liquid obtained after soaking the pine wood chips with large droplets for 140 minutes and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0055] Figure 5h The liquid obtained after soaking the pine wood chips with droplet spray for 140 min (repeated times 7) and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0056] Figure 5i The liquid obtained after soaking the pine wood chips with large droplets for 180 minutes and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0057] Figure 5j The liquid obtained after soaking the pine wood chips with droplet spray for 180 min (repeated times 9) and the test results of hydrogen peroxide test paper in the embodiment of the present invention;

[0058] Figure 6 In the embodiment of the present invention, standard hydrogen peroxide solutions of different concentrations were fully mixed with an equal volume of 0.1M potassium titanium oxalate solution, and the absorption spectrum thereof was detected by an ultraviolet spectrophotometer;

[0059] Figure 7a A graph showing the relationship between the number of times the spraying experiment is repeated and the concentration of hydrogen peroxide in the obtained sample in the embodiment of the present invention;

[0060] Figure 7b Comparison chart of hydrogen peroxide test paper test results of samples obtained from the spray experiment in the embodiment of the present invention;

[0061] Figure 8Comparison of the relationship curves between the number of spray test repetitions and the hydrogen peroxide concentration of the obtained samples when different pine wood chips are used as spray substrates in the embodiments of the present invention;

[0062] Fig. 9 In the embodiment of the present invention, after each spraying, the pine wood chips after spraying are replaced with pine wood chips that have not been sprayed, and the relationship curves between the number of spraying test repetitions and the hydrogen peroxide concentration of the obtained samples when different pine wood chips are used as spray substrates are compared;

[0063] Fig.10a XPS test results of surface groups of pine wood chips in the W treatment group in the embodiment of the present invention;

[0064] Fig.10b XPS test results of surface groups of pine wood chips in the PW treatment group in the embodiment of the present invention;

[0065] Fig.10c XPS test results of surface groups of pine wood chips in the SW treatment group in the embodiment of the present invention;

[0066] Fig.10d XPS test results of surface groups of pine wood chips in the SPW treatment group in the embodiment of the present invention;

[0067] Fig.10e XPS test results of surface groups of pine wood chips in the WW treatment group in the embodiment of the present invention;

[0068] Fig.10f XPS test results of surface groups of pine wood chips in the WPW treatment group in the embodiment of the present invention;

[0069] Fig.11 Changes of different oxygen-containing groups on the surface of pine wood chips after different treatments in the embodiments of the present invention;

[0070] Fig.12 In the embodiment of the present invention, when pure water and galactitol solution are used as spray liquids and untreated pine wood chips are used as spray substrates, the relationship curve between the number of spray test repetitions and the hydrogen peroxide concentration of the obtained sample;

[0071] Fig.13 The global warming potential of each process of the two deoxygenation methods in the embodiments of the present invention. DETAILED DESCRIPTION

[0072] 1. Materials and methods

[0073] (1) Materials

[0074] Pine wood chips (Pinus sylvestris, Zhejiang, China), oxygen content of pine wood chips is 43%; NaOH (Macklin, Shanghai, China), potassium titanium oxalate (Macklin, Shanghai, China), galactitol (Macklin, Shanghai, China), Ca(OH)2 (Aladdin, Shanghai, China); hydrogen peroxide test paper (Quantofix 1319, Germany), O2 (Zebra Experimental Equipment Co., Ltd., Nanjing, China), hydrogen peroxide solution (Macklin, Shanghai, China), ethanol (Aladdin, Shanghai, China).

[0075] (2) Method for making pine wood substrate

[0076] Pine wood chips with a thickness of 0.5 mm were cut into isosceles triangles with a base and a height of 30 mm. The cut pine wood chips were subjected to delignification treatment, alkaline treatment and surface plasma treatment in sequence. After the pretreatment, four triangles were spliced ​​into a four-sided pyramid as a substrate for spraying.

[0077] The method of delignification treatment is as follows: the cut pine wood chips are placed in an ethanol solution of NaOH (1 g / L) and soaked in a water bath at a constant temperature of 50°C for 24 hours to remove part of the lignin in the pine wood chips. After soaking, the chips are washed with deionized water until the pH value of the surface of the pine wood chips returns to 7, and then placed in a vacuum drying oven at 60°C for 12 hours.

[0078] The alkaline treatment method is: put the delignified pine wood chips into a Ca(OH)2 solution (1.5 g / L, pH=11), soak them in a water bath at a constant temperature of 50°C for 6 hours to form an alkaline environment on the surface of the pine wood chips, and then put them in a vacuum drying oven at 60°C for 12 hours.

[0079] The surface plasma treatment method is as follows: the alkaline treated pine wood chips are placed in an atmospheric pressure dielectric barrier discharge device (DBD) with a working power of 4.5 kW and a feed speed of 10 mm / s, and the surface plasma treatment of the pine wood chips is performed twice.

[0080] (3) Droplet spray method

[0081] The structural schematic diagram of the droplet spray system of this embodiment is as follows Figure 1As shown. High-pressure air flows out of the sheath tube through the pipeline, and the air flow rate is 1L / min; the liquid is sent into the pipeline by a micro-injection pump, flows out through the inner tube, and is broken into droplets with a diameter of less than 20μm by the high-pressure air. The total amount of liquid is 10mL, and the liquid flow rate is 100μL / min (the sheath tube of the nozzle is slightly longer than the inner tube, and the spacing at the outlet is 0.5mm; the outer diameter of the sheath tube is 0.6mm, and the wall thickness is 0.03mm; the outer diameter of the inner tube is 0.12mm, and the wall thickness is 0.015mm; the material of the sheath tube and the inner tube is polyimide). The distance between the nozzle outlet and the upper surface of the pine wood chip substrate is 100mm, ensuring that most of the droplets can contact the surface of the pine wood chip and drip from the tip of the tetrahedron.

[0082] In order to ensure that the droplets do not form a water film on the surface of the pine wood chips and prevent the contact between the liquid droplets and the pine wood chips, the spraying time is 5 minutes each time. When the surface of the pine wood chips is completely soaked, replace it with a dry pine wood chip. After continuous spraying for 20 minutes, collect 500 μL of the sample dripping from the tip of the tetrahedron for testing the hydrogen peroxide content, and add the remaining part back into the injection pump to mix with the unsprayed liquid and spray again.

[0083] For pine chips that need to be sprayed repeatedly, the spray system is turned off after each spraying, and the pine chips are placed in a vacuum drying oven at 60°C and dried for 20 minutes.

[0084] This embodiment has a control group, that is: pure water is dripped on the surface of the pine wood chips, where the water is dripped on the surface of the pine wood chips in the form of large droplets (about 1 mm in diameter), the volume of water dripped is the same as the total amount sprayed in the above-mentioned spraying method, and the retention time of the large droplets on the pine wood chips is the same as the total spraying time (due to the large droplets, the treatment of the control group will be unified as "immersing wood chips" in the following text, corresponding to the "spraying wood chips" of the experimental group).

[0085] (4) Detection of hydrogen peroxide in droplets

[0086] a. Qualitative detection: Take 20 μL of the collected sample and drop it on the detection area of ​​the hydrogen peroxide test paper. After 30 seconds, determine whether hydrogen peroxide exists based on whether there is a color change reaction. The concentration of hydrogen peroxide can be roughly identified by comparing it with the colorimetric card.

[0087] b. Quantitative detection: fully mix the hydrogen peroxide standard solutions with concentrations of 0.02mM, 0.05mM, 0.1mM, 0.15mM, 0.2mM, 0.3mM, 0.5mM, 0.7mM, and 1.0mM with an equal volume of 0.1M potassium titanium oxalate (PTO) solution, use an ultraviolet spectrophotometer to detect the absorption spectrum of each standard sample, take the solution absorbance at 400nm and the hydrogen peroxide concentration of the solution as the horizontal and vertical coordinates, and draw the absorbance-hydrogen peroxide concentration curve. After obtaining the slope, the relationship between the concentration y (mM) of the sample hydrogen peroxide and the absorbance x at 400nm is: y = 2.42x. After detecting the absorption spectrum of the sample, use this functional relationship to obtain the hydrogen peroxide concentration of the sample.

[0088] (5) Comparison of Life Cycle Assessment (LCA) of Pine Chip Deoxidation by Baking and Water Spraying

[0089] Table 1 shows the life cycle assessment process of the two methods of baking deoxygenation and water spray deoxygenation. Taking 100 kg of raw materials and a transportation distance of 250 km as an example, the energy consumption and CO2 emissions in the raw material acquisition and transportation stages are calculated.

[0090] Table 1 Comparison of the life cycle assessment process of pine wood chips deoxidation by baking and water spraying

[0091]

[0092]

[0093] When the pine wood chips are torrefied and deoxidized, the heating rate is 15℃ / min, the torrefaction time is 270℃, and the torrefaction time is 40min. Based on the heating efficiency of the tubular furnace of 90%, the energy consumed in processing 100kg of pine wood chips is calculated; according to the calculation method in the paper "Predicting the energy properties of torrefied debarked pine pellets from torrefaction temperature and residence time", the carbon dioxide yield is calculated to be 1.95%, and the carbon dioxide emissions generated during the torrefied and deoxidized period of the pine wood chips are calculated.

[0094] When spraying deoxygenation of pine chips, the calculation model in the paper “An assessment of the torrefaction of North American pine and life cycle greenhouse gas emissions” was used to calculate the energy consumed in processing 100 kg of pine chips and the carbon dioxide emissions generated during the spray deoxygenation of pine chips.

[0095] 2. Experimental results

[0096] (1) Detection of hydrogen peroxide in droplets

[0097] a. Qualitative testing:

[0098] After the water droplets were sprayed, the droplets on the surface of the pine wood chips were collected, e.g. Figure 1 The hydrogen peroxide test paper (Quantofix 1319) was used to detect whether H2O2 was generated. The results were as follows: Figure 2 shown. Figure 2 The test paper did not change color obviously, and it was speculated that the concentration of hydrogen peroxide produced by this method was too low. The collected samples were sprayed again, and the process was repeated for many times. The samples obtained were tested with hydrogen peroxide test paper. It was found that after repeating this process 15 times, the hydrogen peroxide test paper had a significant color change reaction, such as Figure 3 The droplets on the surface of the pine wood chips in the control group were collected and tested with hydrogen peroxide test paper, and the results showed that no color change reaction occurred (see Figure 4 ). This result indicates that hydrogen peroxide is produced during the spraying of water droplets onto the surface of pine wood chips, and that hydrogen peroxide is produced in the form of droplets and cannot be detected at the liquid-solid interface of bulk water. Figures 5a to 5j The results of the samples obtained after repeated droplet spraying for different times were tested by hydrogen peroxide test paper and compared with the corresponding control group results.

[0099] b. Quantitative detection:

[0100] The absorption spectra of standard hydrogen peroxide solutions of different concentrations mixed thoroughly with an equal volume of 0.1 M potassium titanium oxalate (PTO) solution are shown in Figure 2. Figure 6 shown.

[0101] Figure 7a is the relationship curve between the number of spray test repetitions and the hydrogen peroxide concentration of the obtained sample. Figure 7b It is a comparison chart with the test results of hydrogen peroxide test paper. Figure 7b It can be seen that the results obtained by the two detection methods are basically the same.

[0102] (2) Effect of pine wood chip pretreatment on hydrogen peroxide yield

[0103] In this embodiment, the pine wood chips are treated with an ethanol solution of NaOH to remove part of the lignin in the pine wood chips, thereby increasing the oxygen content of the pine wood chips, which can indirectly increase the hydroxyl density on the surface of the pine wood chips; the pine wood chips after the partial lignin is removed are then immersed in a Ca(OH)2 solution to form an alkaline environment on the surface of the pine wood chips to enhance the reaction of generating hydrogen peroxide; finally, the pine wood chips after the alkaline treatment are subjected to plasma treatment to further increase the surface hydroxyl density.

[0104] The pine wood chips treated as above were sprayed repeatedly, and the obtained samples were fully mixed with an equal volume of 0.1MPTO solution, and their absorption spectra were detected. The concentration of hydrogen peroxide in the sample was calculated using the absorbance-hydrogen peroxide concentration curve. The results were as follows: Figure 8 As shown ( Figure 8 and Fig. 9 In the figure, the three-time treated pine chips as the spray substrate refer to the spray substrate made of pine chips that have been soaked in NaOH ethanol solution, soaked in Ca(OH)2 solution, and treated with plasma in sequence). The results show that the yield of hydrogen peroxide is directly related to the hydroxyl density on the surface of the pine chips. Increasing the hydroxyl density on the biomass surface and changing the pH of the biomass surface can increase the yield of hydrogen peroxide. The increasing trend of the subsequent spray hydrogen peroxide concentration in the figure gradually decreases, which is speculated to be caused by the continuous consumption of hydroxyl groups on the surface of the pine chips.

[0105] In order to verify this conjecture, a subsequent experiment was conducted in this embodiment: after each spraying and collecting sample, the unsprayed pine wood chips were replaced, and then water droplets were sprayed onto the surface of the unsprayed pine wood chips again and then collected. The above operation was repeated 40 times to obtain the following Fig. 9 Results shown.

[0106] pass Fig. 9 It can be concluded that when the hydroxyl groups on the surface of the pine wood chips are not consumed, the yield of hydrogen peroxide does not decrease each time it is sprayed, which directly verifies that the hydrogen peroxide in the droplets is synthesized by the free hydroxyl groups on the surface of the water droplets and the pine wood chips.

[0107] (3) Effects of pine wood chip pretreatment and water droplet spraying on the surface oxygen content and surface groups of pine wood chips

[0108] A proper amount of powder was gently scraped off the surface of the pine wood chips (W) without the above-mentioned pretreatment, the pine wood chips (PW) after the above-mentioned pretreatment, the pine wood chips (SPW) after the above-mentioned pretreatment, and the pine wood chips (SW) without the above-mentioned pretreatment but sprayed with water droplets, and the changes in their surface oxygen content and specific surface groups were analyzed using an element analyzer and an X-ray tube electron spectrometer (XPS).

[0109] In order to make the results more accurate, two treatment groups were set up as controls: the pine wood chips that had undergone the above pretreatment were taken, pure water was dripped on their surface, and the pine wood chips in this treatment group were recorded as WPW; in addition, the pine wood chips that had not undergone the above pretreatment were taken, pure water was dripped on their surface, and the pine wood chips in this treatment group were recorded as WW; the water here was dripped onto the surface of the pine wood chips in the form of large droplets, the volume of water dripped was the same as the total amount of spraying, and the retention time of the large droplets on the pine wood chips was the same as the total spraying time.

[0110] The oxygen content of elemental analysis is shown in Table 2, and the XPS test results are shown in Figures 10a to 10f , Fig.11 shown.

[0111] Table 2 Oxygen content of pine wood surface scraping powder after different treatments

[0112]

[0113] From the results of elemental analysis, it can be seen that the oxygen content of the pine chips increased significantly after the above three treatments, decreased after spraying and was lower than the pine chips that had not undergone the above pretreatment. The XPS test results also show that after the pine chips were pretreated as above, the surface hydroxyl density increased, and the hydroxyl density decreased rapidly after spraying. The above results also show that although long-term contact with a large amount of water will also cause a decrease in the oxygen content and hydroxyl density on the surface of the pine chips, the decrease is not large compared to the contact with water droplets. It can be inferred that increasing the hydroxyl density on the surface of pine chips can greatly improve the yield of hydrogen peroxide when water droplets contact the surface of pine chips, and the contact with water droplets has a significant deoxygenation and quality improvement effect on the surface of pine chips.

[0114] (4) Analysis of the mechanism of hydrogen peroxide generation when water droplets contact the surface of pine wood chips

[0115] In order to explore whether the hydroxyl content in water has an effect on the improvement of hydrogen peroxide yield, the pure water in the injection pump was replaced with galactitol (C6H 14 O6) aqueous solution with a concentration of 10 mg / L. This solution was sprayed onto the surface of the pine wood chips and the experiment was repeated. The concentration of hydrogen peroxide in the droplets detected was compared with the previous results. In order to eliminate the interference of galactitol solution on the potassium titanium oxalate colorimetric method, galactitol solution (10 mg / L) was fully mixed with an equal volume of 0.1M PTO solution, and the absorbance was detected. After removing the error, the following results were obtained: Fig.12The results are shown in Figure 1. As can be seen from the figure, although the addition of galactitol increases the hydroxyl content in the solution, the increase in the yield of hydrogen peroxide is negligible. Therefore, it is reasonable to speculate that the hydroxyl content in water does not affect the generation of hydrogen peroxide. In other words, the hydroxyl dissolved in water does not participate in the reaction of the droplet contacting the solid surface to generate hydrogen peroxide, while the hydroxyl on the solid surface participates in the reaction of generating hydrogen peroxide.

[0116] Regarding the formation of hydroxyl radicals, the current mainstream view is that when contact occurs between a solid surface and water molecules, electrons can be transferred from H2O to the solid surface, and the hydroxyl groups on the solid surface become hydroxyl radicals after gaining electrons, and the hydroxyl radicals combine with each other to generate hydrogen peroxide.

[0117] In this embodiment, water droplets generate hydroxyl radicals when contacting hydroxyl groups on the surface of pine wood chips, and then the hydroxyl radicals combine with each other to produce hydrogen peroxide. Through the experiments of this embodiment, it can be determined that the hydroxyl radicals that combine to generate hydrogen peroxide come from the hydroxyl groups on the surface of the pine wood chips.

[0118] (5) Comparison of Life Cycle Assessment (LCA) of Pine Chip Deoxidation by Baking and Water Spraying

[0119] When pine wood chips are baked and deoxidized: the heating rate is 15℃ / min, the baking time is 270℃, the baking time is 40min, the heating efficiency of the tube furnace is 90%, and the energy consumed to process 100kg of pine wood chips is 8.325×10 5 During the deoxygenation of pine chips during torrefaction, the yield of carbon dioxide is 1.95% according to simulation experiments, so 100 kg of pine chips produce 1.95 kg of carbon dioxide after torrefaction.

[0120] When the pine wood chips are sprayed for deoxidation: the air kinetic energy at the nozzle outlet is 0.0477W. According to the model calculation, 14.3% of the air kinetic energy is transmitted to the droplets at the nozzle during spraying, so that the droplets are broken into droplets and sprayed out from the nozzle. Each spraying lasts for 5 minutes, the number of pine wood chips processed each time is 4, and the number of times each pine wood chip is processed is 40 times. The energy consumed to process 100kg of pine wood chips is 0.894×10 5 kJ. During the spray deoxygenation of pine wood chips, the emission of carbon dioxide is 0kg.

[0121] The global warming potential (GWP) of each process of the two deoxygenation methods is as follows: Fig.13 As shown, from the perspective of the whole process, carbon dioxide emissions mainly occur in the baking deoxygenation stage. Compared with baking deoxygenation, spray deoxygenation has significant advantages in reducing greenhouse gas emissions.

[0122] The above experiments show that spraying water droplets on the surface of biomass can react to produce hydrogen peroxide, and at the same time has a significant effect on deoxygenating and improving the quality of biomass.

Claims

1. A method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets, characterized in that: Water droplets with a diameter less than or equal to 20 μm are sprayed onto the surface of the biomass material, and the spray liquid dripping from the surface of the biomass material is collected; the spray liquid is broken into droplets with a diameter less than or equal to 20 μm and re-sprayed onto the surface of the biomass material, and the above operation is repeated until the collected spray liquid contains the target concentration of hydrogen peroxide.

2. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 1, characterized in that: In step (1), the biomass material is one or a combination of two or more of pine wood chips, paulownia wood chips or willow wood chips; the oxygen content of the biomass material is 33-43%.

3. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 1, characterized in that: The steps include: Step (1), pretreating the biomass material to obtain an activated biomass material; Step (2), using activated biomass material to prepare a biomass substrate; Step (3), using a droplet spraying device to spray water droplets onto the surface of the biomass substrate, and collecting the spraying liquid dripping from the biomass substrate; Step (4), atomizing the spraying liquid into water droplets and re-spraying the water droplets onto the surface of the biomass substrate for cyclic droplet spraying until the liquid dripping from the biomass substrate contains a target concentration of hydrogen peroxide.

4. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 3, characterized in that: In step (1), the pretreatment of the biomass material comprises the following steps: Step (1-1), placing the biomass material in a sodium hydroxide ethanol solution and soaking it at a constant temperature, washing it with deionized water until it is neutral after soaking, and then drying it to obtain a primary treated biomass material; Step (1-2), placing the primary treated biomass material in a calcium hydroxide solution and soaking it at a constant temperature, and drying it after soaking to obtain a secondary treated biomass material; Step (1-3), placing the secondary treated biomass material in an atmospheric pressure dielectric barrier discharge device for surface plasma treatment, and obtaining an activated biomass material after the treatment.

5. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 4, characterized in that: In step (1-1), the concentration of the sodium hydroxide ethanol solution is 1-1.5 g / L, and the constant temperature soaking conditions are: soaking at 50-55° C. for 18-24 h; and the drying conditions are: drying at 60-70° C. for 8-12 h; In step (1-2), the concentration of the calcium hydroxide solution is 1.5-2.0 g / L, and the constant temperature soaking condition is: soaking at 50-55° C. for 6-8 hours; the drying condition is: drying at 60-70° C. for 8-12 hours; In step (1-3), the operating power of the dielectric barrier discharge device is 4 to 5 kW, the injection speed is 10 to 15 mm / s, and the surface plasma treatment is repeated at least twice.

6. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 5, characterized in that: In step (1-1), the concentration of the sodium hydroxide ethanol solution is 1 g / L, the constant temperature soaking condition is: soaking at 50° C. for 24 h; the drying condition is: drying at 60° C. for 12 h; In step (1-2), the concentration of the calcium hydroxide solution is 1.5 g / L, and the constant temperature soaking condition is: soaking at 50° C. for 6 h; the drying condition is: drying at 60° C. for 12 h; In step (1-3), the operating power of the dielectric barrier discharge device is 4.5 kW, the injection speed is 10 mm / s, and the surface plasma treatment is repeated twice.

7. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 3, characterized in that: In step (2), the method for preparing the biomass substrate is: Step (2-1), processing the activated biomass material into an isosceles triangle plate, wherein the height and base of the isosceles triangle are equal; Step (2-2), four isosceles triangle plates are spliced ​​into a quadrangular pyramid to form a biomass substrate.

8. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 3, characterized in that: In step (3), the droplet spraying device includes a high-pressure air pump, a liquid injection pump and a liquid droplet nozzle; the fluid outlet end of the high-pressure air pump is fluidly connected to the sheath tube fluid inlet end of the liquid droplet nozzle, and the fluid outlet end of the liquid injection pump is fluidly connected to the inner tube fluid inlet end of the liquid droplet nozzle; the sheath tube is sleeved on the inner tube and the central axis of the sheath tube coincides with the inner tube, and the length of the sheath tube is greater than that of the inner tube; the fluid outlets of the sheath tube and the inner tube are both facing the surface of the biomass substrate; The air flow rate of the high-pressure air pump is 1-1.5 L / min, and the liquid flow rate of the liquid injection pump is 100-120 μL / min; the distance between the fluid outlet of the sheath tube and the fluid outlet of the inner tube is 0.5-0.8 mm; the distance between the outlet of the liquid droplet nozzle and the surface of the biomass substrate is 80-100 mm; the outer diameter of the sheath tube is 0.6 mm, and the wall thickness is 0.03 mm; the outer diameter of the inner tube is 0.12 mm, and the wall thickness is 0.015 mm; the material of the sheath tube and the inner tube is polyimide.

9. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to claim 8, characterized in that: In step (3) and step (4), the biomass substrate is removed and dried after spraying for 5 to 10 minutes, and then reused for spraying after drying until the deoxygenation target is achieved.

10. The method for simultaneously preparing hydrogen peroxide by deoxygenating biomass using water droplets according to any one of claims 2 to 9, characterized in that: In step (1), the biomass is pine wood chips; the oxygen content of the pine wood chips is 43%; the pretreatment of the biomass material includes the following steps: Step (1-1), placing the biomass material in a sodium hydroxide ethanol solution with a concentration of 1 g / L at a constant temperature of 50° C. for 24 hours, washing with deionized water until neutral after the soaking, and then drying at 60° C. for 12 hours to obtain a primary treated biomass material; Step (1-2), placing the primary treated biomass material in a calcium hydroxide solution with a concentration of 1.5 g / L at a constant temperature of 50° C. for 6 hours, and drying at 60° C. for 12 hours after the soaking to obtain a secondary treated biomass material; Step (1-3), placing the secondary treated biomass material in an atmospheric pressure dielectric barrier discharge device under working conditions of a working power of 4.5 kW and a sample feed speed of 10 mm / s for surface plasma treatment twice, and obtaining an activated biomass material after the treatment; In step (2), the method for preparing the biomass substrate is: Step (2-1), processing the activated biomass material into an isosceles triangle plate, wherein the height and base of the isosceles triangle are equal; Step (2-2), splicing four isosceles triangle plates into a quadrangular pyramid to form a biomass substrate; In step (3), the droplet spraying device includes a high-pressure air pump, a liquid injection pump and a liquid droplet nozzle; the fluid outlet end of the high-pressure air pump is fluidly connected to the sheath tube fluid inlet end of the liquid droplet nozzle, and the fluid outlet end of the liquid injection pump is fluidly connected to the inner tube fluid inlet end of the liquid droplet nozzle; the sheath tube is sleeved on the inner tube and the central axis of the sheath tube coincides with the inner tube, and the length of the sheath tube is greater than that of the inner tube; the fluid outlets of the sheath tube and the inner tube are both facing the surface of the biomass substrate; The air flow rate of the high-pressure air pump is 1L / min, and the liquid flow rate of the liquid injection pump is 100μL / min; the distance between the fluid outlet of the sheath tube and the fluid outlet of the inner tube is 0.5mm; the distance between the outlet of the liquid droplet nozzle and the surface of the biomass substrate is 100mm; the outer diameter of the sheath tube is 0.6mm, and the wall thickness is 0.03mm; the outer diameter of the inner tube is 0.12mm, and the wall thickness is 0.015mm; the materials of the sheath tube and the inner tube are both polyimide; In step (3) and step (4), the biomass substrate is removed and dried after spraying for 5 minutes, and then reused for spraying after drying until the deoxygenation target is achieved.

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