Preparation method and application of a bio-based phytate high-efficiency charring agent

Abstract

The present invention discloses a preparation method and application of a bio-based phytate high-efficiency charring agent. In the present invention, lignin is used as a substrate to carry out phosphoric acid esterification coupling with phytic acid. The multi-coordination synergy sites of phytic acid and lignin itself provide a coordination microenvironment for metals. By changing the metal oxidation state, the catalytic carbonization effect of the charring agent is regulated. At the same time, the multi-element synergy carbonization effect of P, N, etc. is coupled. By catalyzing the self-carbonization of vegetation, the catalytic carbonization effect is significantly improved, which is beneficial to constructing an efficient carbonization fire barrier zone.

Description

Technical Field

[0001] The present invention belongs to the field of forest and grassland fire prevention and control of flame retardants, and particularly relates to a preparation method and application of a bio-based phytate high-efficiency charring agent. Background Art

[0002] Frequent forest and grassland fires caused by intensified climate change have caused immeasurable losses to human life and property. Building fire breaks is an important measure to control the development of sudden forest and grassland fires. However, the construction of traditional fire breaks such as mechanical tillage, burning, and biological fire prevention forests has a large amount of work, high costs, and poor emergency response, and it is difficult to quickly and efficiently suppress the spread of fires. Therefore, constructing an efficient emergency fire break is an important development requirement for the precise prevention and control of forest and grassland fires in China.

[0003] Currently, domestic and foreign forest and grassland fires often adopt emergency disposal methods such as spraying water-soluble fire extinguishing agents and foam fire extinguishing agents in the combustion area and downwind area, which are used to quickly extinguish the flames while piling up on the surface of vegetation to form a fire break. The currently used water-soluble fire retardants are mainly diammonium hydrogen phosphate, ammonium sulfate, and ammonium polyphosphate, which rely on their own pyrolysis to produce a certain fire retardant effect, with low efficiency; while the foam fire extinguishing agent can effectively adhere to the surface of vegetation and isolate air, but the accumulation of a large amount of harmful components is not conducive to ecological balance. Therefore, developing a bio-based catalytic charring fire retardant, through catalyzing the dehydration carbonization of cellulose, hemicellulose, etc. of vegetation to form a dense carbonized layer to isolate air and inhibit the thermal decomposition of the inner layer, and strengthening the interaction between the fire retardant and the high-efficiency charring of vegetation, is expected to improve the fire prevention efficiency, timeliness, and environmental protection of the fire prevention system. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a preparation method and application of a bio-based phytate high-efficiency charring agent. The present invention grafts phytic acid with multiple coordination sites on the lignin substrate through a phosphorylation reaction, provides metal anchoring sites and regulates the coordination microenvironment, and improves the catalytic carbonization effect of the charring agent. In addition, the multi-elements of N and P and the rich Lewis acid active sites provide different carbonization synergistic mechanisms, further enhancing the carbonization effect. The present invention utilizes the high coordination environment of phytic acid to provide metal, and at the same time couples the multi-Lewis sites and multi-element flame retardant synergistic effects of phytic acid itself to achieve a high charring rate of vegetation, which can be used to construct an emergency fire break.

[0005] The preparation method of the bio-based phytate high-efficiency charring agent of the present invention includes the following steps:

[0006] Step 1: Disperse lignin in a solvent, add phytic acid after stirring for 30 minutes, and then add urea as a reaction catalyst, and heat to reflux for an esterification reaction; after the reaction is completed, the product is centrifuged and washed to remove unreacted substances, and after drying, phytic acid-modified phosphatized lignin is obtained.

[0007] Step 2: Disperse the phytic acid-modified phosphatized lignin obtained in Step 1 in a solvent, add an aqueous copper salt solution dropwise under heating, stir magnetically, and obtain a high-efficiency charring agent for bio-based phytate after centrifugal washing.

[0008] In Step 1, the mass ratio of lignin to phytic acid solution is 2:3 - 4, and urea accounts for 10 - 25 wt% of lignin.

[0009] The phytic acid is added in the form of an aqueous phytic acid solution, and the concentration of the aqueous phytic acid solution is 50%. The mass ratio of lignin to phytic acid is calculated based on the mass of the phytic acid solution.

[0010] The lignin is de-alkali lignin.

[0011] In Step 1, the heating reaction temperature is 70 °C, and the reaction time is 8 h.

[0012] In Step 1, the solvent is tetrahydrofuran.

[0013] In Step 2, the copper salt is copper acetate.

[0014] In Step 2, the mass ratio of phytic acid-modified phosphatized lignin to copper salt is 1:0.025 - 0.25, preferably 1:0.05. If the proportion of copper salt is too high, the catalytic degradation rate of excessive Cu is relatively fast, the matrix is severely damaged, and it is not easy to form a stable carbon layer.

[0015] In Step 2, the heating temperature is 50 °C, and the reaction time is 2 h.

[0016] In Step 2, the solvent is deionized water.

[0017] Application of the high-efficiency charring agent for bio-based phytate of the present invention in constructing a fireproof barrier.

[0018] Specifically, the high-efficiency charring agent for bio-based phytate is added to a vegetation fireproof belt and used in combination with ammonium polyphosphate (acid source, gas source) to promote the charring of the vegetation itself and improve the flame retardancy and flame suppression effect.

[0019] The vegetation fireproof belt includes coniferous vegetation such as Pinus massoniana, Pinus armandii, Platycladus orientalis, Metasequoia glyptostroboides, and broad-leaved vegetation such as Quercus mongolica, Betula platyphylla, Ginkgo biloba, and arbors.

[0020] The mass ratio of the charring agent to ammonium polyphosphate is 1:1 - 7.

[0021] The spraying amount is required to reach at least 100 g / m 2 .

[0022] In the present invention, phytic acid is grafted onto the surface of lignin through an esterification reaction, and then copper ions are loaded through coordination. By combining the synergistic effect of multiple elements such as P and N and the carbonization effect catalyzed by Lewis acid, a remarkable fireproof carbonization effect is achieved. When metal ions coordinate with phytic acid, they also coordinate with the hydroxyl groups on lignin. In this multi-coordination environment, the oxidation state of Cu shifts more significantly, which is beneficial to improving the catalytic carbonization effect.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The present invention has good flame inhibition ability and high carbonization effect when compounded with traditional fire retardants for forest and grassland fires and APP.

[0025] 2. The preparation method of the carbonizing agent in the present invention is simple and easy to operate.

[0026] 3. The metal-modified phytic acid-based carbonizing agent of the present invention couples multiple element synergies and multiple active sites, which is beneficial to promoting the carbonization of vegetation itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0028] Figure 1 It is the scanning electron microscope image of the sample prepared in Example 1 of the present invention and the comparative sample.

[0029] Figure 2 It is the thermogravimetric analysis curve of the sample prepared in Example 1 of the present invention and the comparative sample.

[0030] Figure 3 It is the heat release rate diagram of the materials provided in Examples 2-5 and the comparative example of the present invention.

[0031] Figure 4 It is the total heat release rate diagram of the materials provided in Examples 2-5 and the comparative example of the present invention.

[0032] Figure 5 It is the total smoke release rate diagram of the materials provided in Examples 2-5 and the comparative example of the present invention.

[0033] Figure 6 It is the fire spread temperature curve diagram of pure pine needles.

[0034] Figure 7 It is the temperature curve diagram of the fire spread experiment set in Example 6 of the present invention.

[0035] Figure 8 It is the temperature curve diagram of the fire spread experiment set in Example 7 of the present invention.

[0036] Figure 9 It is the temperature curve graph of the fire spread experiment set in Example 8 of the present invention.

[0037] Figure 10 It is the thermogravimetric curve graph of the air after ammonium polyphosphate and charring agent in the examples of the present invention are compounded in different ratios and added according to 10% of the mass of pine needles.

[0038] Figure 11 For the examples of the present invention Figure 10 partial enlarged view.

[0039] Figure 12 It is the thermogravimetric analysis curve of the sample in Example 5 of the present invention under a nitrogen atmosphere. Specific embodiments

[0040] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in detail with reference to examples. The specific examples described herein are only used to explain the present invention and do not limit the present invention.

[0041] Example 1:

[0042] (1) Take 10 g of lignin and add it to 50 mL of tetrahydrofuran solution, stir for 30 min to fully disperse, then add 15 g of 50% phytic acid solution and 1 g of urea, and carry out condensation reflux at 70 °C for 8 h; after the reaction ends, centrifuge the obtained product, wash it several times with ethanol, and then vacuum dry it at 60 °C for 12 h to obtain phosphorylated lignin (P-Lignin).

[0043] (2) Take 2 g of the above-prepared modified lignin and disperse it in deionized water, add 0.1 g of Cu(Ac)2·H2O, stir at 50 °C for 2 h, centrifuge the product, wash it with deionized water and ethanol respectively until the washing liquid is completely colorless, and obtain a metal-modified phytic acid-based lignin charring agent (P-Lignin@Cu) after drying.

[0044] Characterize the morphology of the product sample by scanning electron microscope. Figure 1 They are the scanning electron microscope images of lignin (Lignin), phosphorylated lignin (P-Lignin) and metal-modified phytic acid-based lignin charring agent (P-Lignin@Cu) respectively. The introduction of phytic acid and metal has a great impact on the surface morphology of lignin. Due to the abundant hydroxyl groups in phytic acid being conducive to the formation of stable hydrogen bonds, the surface of P-Lignin is quite smooth compared with lignin. In addition, the multi-coordination sites in phytic acid enable Cu ions to be in a high-coordination state, resulting in significant changes in the particle size and morphology of P-Lignin@Cu, which is conducive to exposing more active sites.

[0045] Analyze the thermal stability of the product by thermogravimetric analyzer. Figure 2Mass loss curves and derivative mass curves of lignin, phosphoric acid esterified lignin (P-Lignin), and metal-modified phytic acid-based lignin charring agent (P-Lignin@Cu), respectively. The catalytic degradation of Cu ions results in a decrease in the thermal stability of P-Lignin@Cu, but also promotes the rapid formation of the carbon layer, ultimately leading to an increase in the char residue content. Compared with pure lignin, the incorporation of phytic acid and Cu ions increases the char residue yield from 10.07 wt% to 34.22 wt%. Due to the complex composition of lignin, including the Cα-Cβ-Cγ side chain and abundant functional groups on the aromatic ring, the temperature range for pyrolysis is relatively wide, from room temperature to about 600 °C. The derivative thermogravimetric curve of lignin has two representative rapid decomposition stages, corresponding to the decomposition of the C-C main chain and the β-β structure, respectively. Surface modification changes the degradation behavior of lignin. The catalysis of transition metal Cu enables almost complete pyrolysis of lignin before 350 °C. Cu accelerates the reaction between phosphoric acid and the lignin matrix, making the dehydration and carbonization rate faster and increasing the formation of the carbon layer.

[0046] Example 2:

[0047] First, dry pine needles are crushed, and then 9 g of pine needle powder and 1 g of ammonium polyphosphate are weighed and uniformly mixed to obtain a compound powder with a 10 wt% ammonium polyphosphate loading (PN / APP 10).

[0048] Example 3:

[0049] First, 4 g of ammonium polyphosphate and 1 g of the above-prepared copper-based phytic acid-modified lignin charring agent are weighed and uniformly mixed to obtain a compound fire retardant powder. Then, dry pine needles are crushed, and 9 g of pine needle powder and 1 g of the compound fire retardant are weighed and uniformly mixed to obtain a compound powder with a 10 wt% fire retardant loading (PN / APL@Cu 10).

[0050] Example 4:

[0051] First, 4 g of ammonium polyphosphate and 1 g of the above-prepared copper-based phytic acid-modified lignin charring agent are weighed and uniformly mixed to obtain a compound fire retardant powder. Then, dry pine needles are crushed, and 8 g of pine needle powder and 2 g of the compound fire retardant are weighed and uniformly mixed to obtain a compound powder with a 20 wt% fire retardant loading (PN / APL@Cu 20).

[0052] Example 5:

[0053] First, 4 g of ammonium polyphosphate and 1 g of the above-prepared copper-based phytic acid-modified lignin charring agent are weighed and uniformly mixed to obtain a compound fire retardant powder. Then, dry pine needles are crushed, and 7 g of pine needle powder and 3 g of the compound fire retardant are weighed and uniformly mixed to obtain a compound powder with a 30 wt% fire retardant loading (PN / APL@Cu 30).

[0054] The above materials were analyzed by a cone calorimeter, and pure pine needles (Pure PN) were used as a comparison. The results are referred to Figure 3 , Figure 4 and Figure 5 . Figure 3 This is the heat release rate graph of the composite materials provided in Examples 2-5 of the present invention. Since the Lewis acid coordination has a certain effect on the vegetation chain segment and can quickly catalyze the degradation of the segment, the peak heat release rate slightly increases after replacing part of the ammonium polyphosphate with the copper-based phytic acid charring agent, but the flame combustion time also decreases significantly. Figure 4 This is the total heat release graph of the composite materials provided in Examples 2-5 of the present invention, further verifying that the charring agent can quickly form char by promoting the degradation of the segment, thereby reducing the continuous release of heat. In addition, Figure 5 This is the total smoke release graph of the composite materials provided in Examples 2-5 of the present invention. It can be seen that through the catalytic charring effect, the copper-based charring agent also has good smoke suppression performance.

[0055] Example 6:

[0056] The dry pine needles were evenly spread on a test bench of 120×50 cm according to a loading amount of 0.6 kg / m 2 . Thermocouples were set every 15 cm starting from 5 cm (at 5, 20, 35, 50, 65, 80, 95, 110 cm). The barrier zone was set at 65-85 cm, and a heat flux meter was set in the center of the barrier zone to record the magnitude of the radiant heat flux. The ammonium polyphosphate and the copper-based phytic acid modified lignin charring agent were compounded in a ratio of 4:1 and sprayed at the barrier zone position through a peristaltic pump. After drying with a heat source, an ignition experiment was carried out. A cotton thread soaked in ethanol was set at the starting point of the test bench to ensure that the flame spread in a straight line.

[0057] 360 g of pine needles were weighed and evenly spread on the test bench. Subsequently, 4 g of ammonium polyphosphate and 1 g of copper-based phytic acid modified lignin charring agent were compounded into a powder and dissolved in water, and sprayed on the surface of the pine needles through a peristaltic pump. The spraying area was 20×50 cm. After drying with a heat source, an ignition experiment was carried out.

[0058] Example 7:

[0059] 360 g of pine needles were weighed and evenly spread on the test bench. Subsequently, 8 g of ammonium polyphosphate and 2 g of copper-based phytic acid modified lignin charring agent were compounded into a powder and dissolved in water, and sprayed on the surface of the pine needles through a peristaltic pump. The spraying area was 20×50 cm. After drying with a heat source, an ignition experiment was carried out.

[0060] Example 8:

[0061] Weigh 360 g of pine needles and spread them evenly on the test bench. Subsequently, weigh 10 g of ammonium polyphosphate powder and dissolve it in water. Spray it on the surface of the pine needles with a peristaltic pump. The spraying area is 20×50 cm. After drying with a heat source, conduct an ignition experiment.

[0062] The samples with the barrier band sprayed and pure pine needles (Pure PN) were compared for fire spread tests. The temperature changes during the fire spread provided in Examples 6-8 above are as Figure 6 、 Figure 7 、 Figure 8 and Figure 9 shown. It was significantly found that compared with Figure 6 pure pine needles, Figure 7 in 2 , after laying the barrier band with ammonium polyphosphate and copper-based phytic acid modified charring agent at 50 g / m 2 , the temperature of the thermocouple inside the barrier band decreased significantly. When the spraying dosage increased to 100 g / m 2 , the flame front stopped spreading after reaching the fifth thermocouple, confirming the effectiveness of the charring agent. In addition, Figure 9 the flame suppression effect of the barrier band with only ammonium polyphosphate added at 100 g / m 2 was compared. Since ammonium polyphosphate itself cannot form an effective carbon layer, it is almost impossible to prevent the flame from spreading, further verifying the high efficiency of the copper-based phytic acid modified charring agent.

[0063] The above are only the embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be within the protection scope of the present invention.

Claims

1. Application of a bio-based phytate efficient carbonizing agent in constructing a fire barrier, characterized in that: The bio-based phytate high-efficiency carbon-forming agent and ammonium polyphosphate are mixed and added to the vegetation firebreak; The mass ratio of the carbon-forming agent to ammonium polyphosphate is 1:1-7; The bio-based phytate high-efficiency carbon-forming agent is prepared by the following method: Step 1: Disperse lignin in a solvent, stir and disperse it evenly, then add phytic acid solution, then add urea as a reaction catalyst, heat to reflux for esterification reaction; after the reaction is completed, centrifuge and wash the product to remove unreacted products, and dry it to obtain phytic acid-modified phospholipid lignin; Step 2: dispersing the phytic acid-modified phospholipid lignin obtained in step 1 in a solvent, adding a copper salt aqueous solution dropwise under heating, stirring magnetically, and centrifuging and washing to obtain a bio-based phytate high-efficiency carbonizing agent; In step 1, the solvent is tetrahydrofuran; In step 1, the mass ratio of lignin to phytic acid solution is 2:3-4, and urea accounts for 10-25wt% of lignin; In step 2, the copper salt is copper acetate; the mass ratio of phytic acid-modified phospholipid lignin to the copper salt is 1:0.

05.

2. The use according to claim 1, characterized in that: In step 1, the heating reaction temperature is 70° C. and the reaction time is 8 h.

3. The use according to claim 1, characterized in that: In step 2, the heating temperature is 50° C. and the reaction time is 2 h.

4. The use according to claim 1, characterized in that: The total spraying amount of the carbon forming agent and ammonium polyphosphate is ≥100g / m 2 .

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