Hermetia illucens chitosan-based catalytic functional membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of functional membrane materials and green chemical engineering, in particular to a hermetia illucens chitosan-based catalytic functional membrane as well as a preparation method and application thereof. The method comprises the following steps: carrying out quaternization modification on hermetia illucens chitosan; the preparation method comprises the following steps: loading layered double hydroxides or nano solid base catalytic active components into quaternized chitosan through an in-situ hydrothermal growth method or a physical blending method; and finally, carrying out film casting, crosslinking and curing to obtain the catalytic functional film with a three-dimensional network structure. According to the invention, renewable hermetia illucens chitosan is taken as a matrix, and firm anchoring of a catalyst and the matrix on a molecular / nanoscale and optimization of a mass transfer channel are realized through a synergistic strategy of'functionalized matrix design-in-situ structure symbiotic construction-cross-linked network reinforcement '. The obtained membrane has excellent anion conductivity, catalytic activity, mechanical strength and operation stability, can be directly used as a core component of a membrane reactor, and is used for continuously and efficiently preparing biodiesel.

Description

Technical Field

[0001] This invention relates to the fields of functional membrane materials and green chemical technology, specifically to a black soldier fly chitosan-based catalytic functional membrane, its preparation method, and its application. Background Technology

[0002] Biodiesel, as a green and renewable liquid fuel, is crucial for achieving the "dual carbon" goal through its large-scale production. Currently, catalytic membrane reactors, which couple heterogeneous catalysis with membrane separation technology, show great potential. However, the core catalytic membrane faces a series of bottlenecks in the process of transitioning from laboratory to industrial applications, particularly regarding the combination of catalyst and support.

[0003] For example, current technologies often load catalysts onto polymer membranes through simple physical blending or impregnation. The weak interactions make these catalysts prone to leaching and detachment under long-term fluid shear, thermal, and chemical conditions, leading to catalytic activity degradation, product contamination, and the loss of the advantages of easy separation in heterogeneous catalysis. Crosslinking modification also fails to fundamentally solve this problem. Secondly, increasing catalyst loading is necessary to improve efficiency, but high loading can lead to membrane densification and blockage of mass transfer channels, creating a contradiction of high loading and low utilization. Furthermore, traditional polymer supports only provide mechanical support, further exacerbating mass transfer limitations. In addition, existing catalytic membranes have limited functions. Acidic membranes can only catalyze the esterification of free fatty acids and are inefficient for triglycerides; alkaline membranes or solid alkali catalysts excel at transesterification but are easily deactivated by saponification of free fatty acids in the feedstock. For real waste oil feedstocks containing both types of components, complex pretreatment is required, increasing process costs. For example, the paper "Optimization of HTCC / Na2SiO3 / ECH Hybrid Membrane by Response Surface Methodology" uses epichlorohydrin as a linker to chemically fix sodium silicate onto the chitosan quaternary ammonium salt molecular chain to prepare a sodium silicate / chitosan quaternary ammonium salt organic-inorganic hybrid membrane. However, sodium silicate has the risk of leaching, and the covalent bonds may break during long-term use. Patent CN117339630A discloses a solid-phase preparation of sulfonated chitosan membrane, which can only catalyze esterification, and its acidic nature limits its application in transesterification.

[0004] Therefore, there is an urgent need to develop a catalytic functional membrane that systematically solves the above-mentioned dilemmas from the perspectives of combination method, structural design and functional integration, which is of milestone significance for promoting the greening and continuous process of biodiesel production. Summary of the Invention

[0005] In view of this, the present invention provides a black soldier fly chitosan-based catalytic functional membrane, its preparation method, and its application. The present invention aims to achieve a robust and uniform loading of catalytically active components in the membrane matrix through innovation in material design and preparation processes, constructing a permeable microstructure that facilitates mass transport, and endowing the membrane with the ability to synergistically catalyze multiple reactions; it solves the technical problems of existing catalytic functional membranes, such as poor stability due to weak bonding between the catalyst and the support, low mass transfer efficiency due to dense structure, and limited adaptability to raw materials due to single function.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a chitosan-based catalytic functional membrane from black soldier fly larvae, comprising the following steps: S1. Quaternization modification of black soldier fly chitosan to obtain quaternized chitosan; S2. The catalytically active component is loaded onto the quaternized chitosan to obtain a catalyst-loaded complex; the catalytically active component is a layered bimetallic hydroxide or a nano-solid base catalyst. S3. The composite is formed into a membrane and cross-linked and cured to obtain the catalytic functional membrane.

[0007] Preferably, the layered bimetallic hydroxide comprises ZnCo-LDH, and the layered bimetallic hydroxide is loaded onto the quaternized chitosan by in-situ hydrothermal growth.

[0008] Specifically, the ZnCo-LDH has the advantages of acid-base synergistic catalysis, good compatibility with chitosan matrix, high structural stability, and controllable cost.

[0009] Preferably, the nano-solid base catalyst is selected from at least one of nano-CaO, nano-MgO, or nano-SrO, and the nano-solid base catalyst is loaded into the quaternized chitosan by physical blending.

[0010] Specifically, the nano-CaO, nano-MgO, or nano-SrO has the characteristics of strong alkalinity, high specific surface area, good dispersibility, low cost, environmental friendliness, and easy combination with chitosan matrix.

[0011] Preferably, the in-situ hydrothermal growth method includes: S2-1. Dissolve zinc salt, cobalt salt and urea in water to form a precursor solution; S2-2. Dissolve the quaternized chitosan obtained in step S1 and mix it with the precursor solution; S2-3. The mixed solution is subjected to a hydrothermal reaction.

[0012] Specifically, zinc salt, cobalt salt, and urea are dissolved in deionized water to form a precursor solution, which is then mixed with a quaternized chitosan solution. The dense positive charges on the quaternized chitosan chains are used as nucleation sites to guide the in-situ crystallization and growth of ZnCo-LDH crystals within the polymer network. Subsequently, a hydrothermal reaction is carried out. After the reaction is completed, the mixture is washed and dried to obtain a composite powder loaded with ZnCo-LDH.

[0013] Preferably, the zinc salt contains Zn 2+ Co in cobalt salts 2+ The molar ratio is (0.5-3):1; the mass ratio of the quaternized chitosan, the total mass of the zinc salt and cobalt salt and the mass of urea is 1:(2-3):(1.6-2.4).

[0014] Preferably, the hydrothermal reaction is carried out at a temperature of 120-180°C for 6-24 hours.

[0015] Specifically, the proportion range of raw materials used in this invention ensures that LDH crystals grow fully and uniformly, while maintaining the porosity and integrity of the membrane structure; the appropriate reaction temperature and time ensure that LDH crystals crystallize in situ in the chitosan network, ensuring that LDH crystals grow fully and the structure is stable.

[0016] Preferably, the amount of the nano-solid base catalyst is 10%-60% of the mass of quaternized chitosan. This range balances catalytic activity, membrane mechanical strength, and mass transfer efficiency.

[0017] Specifically, the dosage range of the nano-solid base catalyst ensures the balanced catalytic activity of the membrane, membrane structural integrity, mass transfer efficiency, operational stability, and process feasibility.

[0018] Preferably, in step S1, the quaternizing agent used in the quaternization modification is selected from at least one of 2,3-epoxypropyltrimethylammonium chloride (GTMAC) and chloroacetamide, and the molar ratio of the quaternizing agent to the chitosan structural unit is (1-3):1.

[0019] Specifically, the ratio of the quaternizing agent to chitosan ensures sufficient quaternization to provide adequate nucleation sites and ion conduction capacity.

[0020] More preferably, in step S1, the degree of deacetylation of the black soldier fly chitosan is not less than 85%; the quaternization modification time is 4-12 hours and the temperature is 60-80℃.

[0021] Specifically, the degree of deacetylation directly affects the number of free amino groups, which in turn determines the efficiency of the quaternization reaction and the membrane's film-forming properties, mechanical strength, and ion conductivity. A degree of deacetylation of not less than 85% is a necessary condition to ensure the basic performance of the membrane.

[0022] More preferably, in step S3, the crosslinking agent is selected from at least one of glutaraldehyde and epichlorohydrin, the volume concentration of the crosslinking agent is 0.5%-5%, and the crosslinking time is 1-12h.

[0023] Specifically, the crosslinking parameters are optimized settings to maintain the stability of the catalytic membrane in high-temperature, alkaline, and solvation reaction environments. If the concentration is too low or the time is too short, the crosslinking will be insufficient, the membrane will easily swell, and the catalyst will easily leach out; if the concentration is too high or the time is too long, the membrane will become brittle and the mass transfer channels will be blocked.

[0024] Specifically, the crosslinking treatment further strengthens the inorganic-organic symbiotic three-dimensional network formed in step S2, which can improve the chemical stability and mechanical integrity of the membrane under high temperature, solvent and alkaline reaction environments.

[0025] In a second aspect, the present invention provides a black soldier fly chitosan-based catalytic functional membrane prepared by the method described in the first aspect.

[0026] Thirdly, the present invention provides an application of the black soldier fly chitosan-based catalytic functional membrane as described in the second aspect in the preparation of biodiesel, wherein the feedstock oil used to prepare the biodiesel contains free fatty acids and triglycerides.

[0027] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention uses chitosan obtained from the resource utilization of waste black soldier fly pupa shells as raw material to replace traditional petroleum-based polymers. The membrane material itself is biodegradable, the raw material source is wide, the cost is low, and it is environmentally friendly, which is in line with the concepts of green chemistry and circular economy.

[0028] (2) In particular, the present invention uses an in-situ hydrothermal growth strategy to grow LDH catalyst in a polymer network in a chemical bond and structural interlocking manner, thereby achieving a firm anchoring of the catalyst at the nanoscale. Compared with the traditional physical blending method, the long-term operation stability of the membrane is significantly improved.

[0029] (3) The LDH nanosheets or uniformly dispersed nanocatalysts grown in situ in this invention form a porous, interconnected mesoscopic structure within the membrane. These structures serve as both high specific surface area catalytic active centers and nanochannels for rapid diffusion of reactants and products. Combined with the OH groups of the quaternized chitosan matrix itself... - The ion conduction capability enables the integrated design of active sites, i.e., mass transfer channels, achieving synergistic enhancement of catalysis and mass transfer.

[0030] (4) The catalytic functional membrane prepared by this invention is a multifunctional synergistic system. The quaternary ammonium group provides an alkaline environment and the ability to activate alcohols; ZnCo-LDH not only provides strong alkalinity and possible Lewis acid sites, but its unique binding state with the polymer may also modulate the electronic properties. The synergy of the two enables a single membrane to simultaneously and efficiently catalyze transesterification and esterification reactions, thereby directly treating high-acid-value waste oils, eliminating the pre-esterification step, greatly broadening the source of raw materials and simplifying the process.

[0031] (5) The membrane preparation method is simple, with mild and controllable conditions, and is easy to scale up. The resulting membrane has good mechanical properties and is easy to assemble into membrane modules, providing a reliable material basis and technical solution for the continuous and integrated production of biodiesel. Examples show that after 200 hours of continuous operation, the biodiesel yield of the membrane is stable at over 94%, with no significant catalyst loss, overcoming the core stability bottleneck in the application of heterogeneous catalytic membranes. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a surface SEM image of the catalytic functional membrane prepared in Example 1 of the present invention. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] In existing technologies, acidic membranes (such as sulfonated chitosan) can only catalyze esterification reactions and treat high-acid-value oils; alkaline systems (such as sodium silicate) mainly catalyze transesterification reactions and are prone to saponification and deactivation when encountering high-acid-value oils. When dealing with real waste oils with complex and varied compositions (containing both triglycerides and free fatty acids), cumbersome pretreatment or multi-step processes are necessary.

[0036] This invention creatively designs an integrated acid-base synergistic catalytic membrane. The quaternary ammonium groups within the membrane provide an alkaline environment and OH- ions. - Conductive pathways, quaternized chitosan transports reactants OH- via ion exchange. - Or CH3O -Rapid transport to catalytic active sites; at the same time, ZnCo-LDH itself has both basic sites and Lewis acidic sites, and its unique electronic structure has a certain catalytic ability for esterification reaction; the two active sites work together at the nanoscale, enabling the membrane to catalyze both esterification and transesterification reactions simultaneously.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] In this document, the terms “containing,” “comprising,” or “including” are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0039] In this document, the terms “optional,” “optionally,” or “optional” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0041] All materials used in this invention were purchased from the market; among them, 2,3-epoxypropyltrimethylammonium chloride (GTMAC, ≥95%), Zn(NO3)2·6H2O (AR), Co(NO3)2·6H2O (AR), urea (AR), glutaraldehyde (AR), nano CaO (≥98%, <160 nm), and nano MgO (≥99.9%, 100-300 nm) were all purchased from Aladdin Reagent Co., Ltd.

[0042] The black soldier fly chitosan with a degree of deacetylation of 92% used in this invention is obtained by the following preparation method: (1) Raw material pretreatment: Take 100 g of dried black soldier fly pupa shells, clean them with deionized water by ultrasonic cleaning, rinse them with anhydrous ethanol, dry them at 60℃ for 24 hours, pulverize them and pass them through a 60-mesh sieve to obtain sieved powder. (2) Decalcification treatment: The sieved powder was mixed with a composite organic acid solution (0.02 M citric acid and 0.03 M malic acid, molar ratio 2:3) at a solid-liquid ratio of 1:12 (g / mL), and the mixture was shaken at room temperature (25-35℃) for 3 hours. After the reaction, the mixture was filtered, washed with deionized water until neutral, and dried at 60℃ to obtain the decalcified product. (3) Deproteinization treatment: Place the decalcified products in the following order: ① React in 1.5% NaOH solution (solid-liquid ratio 1:18 g / mL) at 45℃ in an air shaker for 1.5 hours, then wash; ② 3.5% NaOH solution (solid-liquid ratio 1:18 g / mL), react in an air shaker at 70℃ for 1.5 hours, then wash; ③ React in 5% NaOH solution (solid-liquid ratio 1:18 g / mL) in an air shaker at 85℃ for 1 hour, then wash. After each reaction, the chitin was washed with deionized water until neutral, and finally dried at 60°C to remove proteins, yielding flake chitin. (4) Depigmentation treatment: Chitosan and 15% hydrogen peroxide solution were mixed at a solid-liquid ratio of 1:35 (g / mL), reacted at 75°C for 3 hours, washed until neutral, and dried to obtain the depigmented product; (5) Deacetylation treatment: The depigmented chitin was mixed with 40% NaOH solution at a solid-liquid ratio of 1:18 (g / mL), placed in a 90℃ water bath, and reacted for 6 hours under the assistance of 600 W ultrasound. After the reaction, the mixture was filtered, washed with deionized water until neutral, and dried at 60℃ to obtain the final product chitosan.

[0043] Example 1

[0044] This embodiment provides an in-situ hydrothermal growth method for chitosan-based catalytic functional membranes from black soldier fly larvae, comprising the following steps: (1) Quaternization modification of chitosan: 2g of black soldier fly chitosan with a degree of deacetylation of 92% was dissolved in 100mL of 2% (v / v) acetic acid solution. 1.85g of GTMAC (the molar ratio of GTMAC to chitosan structural units was 1:1) was added, and the mixture was stirred at 70℃ for 8h. After the reaction was completed, the mixture was precipitated with ethanol, washed, and dried under vacuum at 60℃ to obtain quaternized chitosan; (2) Loading of ZnCo-LDH: Weigh 0.5g of the above quaternized chitosan and dissolve it in 20mL of 2% (v / v) acetic acid; separately take 0.5g of Zn(NO3)2·6H2O and 1.0g of Co(NO3)2·6H2O (Zn 2+ Co 2+1.0 g of urea and 1.0 g of urea were dissolved in 20 mL of deionized water. The two solutions were mixed and stirred for 2 h, then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and hydrothermally reacted at 150 °C for 12 h. After the reaction was completed, the precipitate was collected by centrifugation, washed with deionized water and ethanol, and dried at 60 °C to obtain a dark green composite powder. (3) Film formation and crosslinking: 0.5g of the above composite powder was dispersed in 10mL of 2% (v / v) acetic acid, cast onto a glass plate, and dried at 45℃ to form a film; the film was peeled off and immersed in 2% (v / v) glutaraldehyde aqueous solution for crosslinking for 4h; then it was thoroughly washed with deionized water and dried to obtain a catalytic functional film, denoted as M1.

[0045] Figure 1 The image shows a surface SEM image of the catalytic functional membrane M1 prepared in Example 1. An inorganic-organic symbiotic composite structure can be observed, consisting of a bright inorganic phase (ZnCo-LDH nanostructure) and a dark organic polymer matrix (quaternized chitosan).

[0046] Example 2

[0047] This embodiment provides an in-situ hydrothermal growth method for chitosan-based catalytic functional membranes from black soldier fly larvae, comprising the following steps: (1) Quaternization modification of chitosan: 2g of black soldier fly chitosan with a degree of deacetylation of 92% was dissolved in 100mL of 2% (v / v) acetic acid solution. 3.69g of GTMAC (the molar ratio of GTMAC to chitosan structural units was 2:1) was added, and the mixture was stirred at 70℃ for 8h. After the reaction was completed, the mixture was precipitated with ethanol, washed, and dried under vacuum at 60℃ to obtain quaternized chitosan; (2) Loading of ZnCo-LDH: Weigh 0.5g of the above quaternized chitosan and dissolve it in 20mL of 2% (v / v) acetic acid; separately take 0.75g Zn(NO3)2·6H2O and 0.25g Co(NO3)2·6H2O (Zn 2+ Co 2+ 0.8 g of urea and 0.8 g of urea were dissolved in 20 mL of deionized water. The two solutions were mixed and stirred for 2 h, then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and hydrothermally reacted at 120 °C for 24 h. After the reaction was completed, the precipitate was collected by centrifugation, washed with deionized water and ethanol, and dried at 60 °C to obtain a dark green composite powder. (3) Film formation and crosslinking: 0.5g of the above composite powder was dispersed in 10mL of 2% (v / v) acetic acid, cast onto a glass plate, and dried at 45℃ to form a film; the film was peeled off and immersed in 1% (v / v) glutaraldehyde aqueous solution for crosslinking for 2h; then it was thoroughly washed with deionized water and dried to obtain a catalytic functional film, denoted as M2.

[0048] Example 3

[0049] This embodiment provides an in-situ hydrothermal growth method for chitosan-based catalytic functional membranes from black soldier fly larvae, comprising the following steps: (1) Quaternization modification of chitosan: 2g of black soldier fly chitosan with a degree of deacetylation of 92% was dissolved in 100mL of 2% (v / v) acetic acid solution. 5.54g of GTMAC (the molar ratio of GTMAC to chitosan structural units was 3:1) was added, and the mixture was stirred at 70℃ for 8h. After the reaction was completed, the mixture was precipitated with ethanol, washed, and dried under vacuum at 60℃ to obtain quaternized chitosan; (2) Loading of ZnCo-LDH: Weigh 0.5g of the above quaternized chitosan and dissolve it in 20mL of 2% (v / v) acetic acid; separately take 0.67g Zn(NO3)2·6H2O and 0.33g Co(NO3)2·6H2O (Zn 2+ Co 2+ 1.2 g of urea and 1.2 g of urea were dissolved in 20 mL of deionized water. The two solutions were mixed and stirred for 2 h, then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and hydrothermally reacted at 180 °C for 6 h. After the reaction was completed, the precipitate was collected by centrifugation, washed with deionized water and ethanol, and dried at 60 °C to obtain a dark green composite powder. (3) Film formation and crosslinking: 0.5g of the above composite powder was dispersed in 10mL of 2% (v / v) acetic acid, cast onto a glass plate, and dried at 45℃ to form a film; the film was peeled off and immersed in 5% (v / v) glutaraldehyde aqueous solution for crosslinking for 1h; then it was thoroughly washed with deionized water and dried to obtain a catalytic functional film, denoted as M3.

[0050] Example 4

[0051] This embodiment provides a physical blending method for black soldier fly chitosan-based catalytic functional membranes, including the following steps: (1) Quaternization modification of chitosan: Same as in Example 1; (2) Introduction of nano-CaO: Take 1g of the above quaternized chitosan and dissolve it in 40mL of 2% (v / v) acetic acid solution; add 0.3g of commercial nano-CaO (loading of 30%) and ultrasonically disperse for 2h to obtain a uniform casting solution; (3) Film formation and crosslinking: The above casting solution was cast onto a glass plate and dried at 45°C to form a film; the film was peeled off and immersed in a 1.5% (v / v) glutaraldehyde aqueous solution for crosslinking for 6 hours; then it was thoroughly washed with deionized water and dried to obtain a catalytic functional film, denoted as M4.

[0052] Example 5

[0053] This embodiment provides a physical blending method for black soldier fly chitosan-based catalytic functional membranes, including the following steps: (1) Quaternization modification of chitosan: Same as in Example 1; (2) Introduction of nano-MgO: Take 0.5g of the above quaternized chitosan and dissolve it in 20mL of 2% (v / v) acetic acid solution; add 0.3g of commercial nano-MgO (loading of 60%) and ultrasonically disperse for 2h to obtain a uniform casting solution; (3) Film formation and crosslinking: The above casting solution was cast onto a glass plate and dried at 45°C to form a film; the film was peeled off and immersed in a 3% (v / v) glutaraldehyde aqueous solution for crosslinking for 8 hours; then it was thoroughly washed with deionized water and dried to obtain a catalytic functional film, denoted as M5.

[0054] Example 6

[0055] This embodiment provides a physical blending method for black soldier fly chitosan-based catalytic functional membranes, including the following steps: (1) Quaternization modification of chitosan: Same as in Example 1; (2) Introduction of nano-SrO: Take 1.0g of the above quaternized chitosan and dissolve it in 20mL of 2% (v / v) acetic acid solution; add 0.1g of commercial nano-SrO (loading amount of 10%), and ultrasonically disperse for 2h to obtain a uniform casting solution; (3) Film formation and crosslinking: The above casting solution was cast onto a glass plate and dried at 45°C to form a film; the film was peeled off and immersed in a 0.5% (v / v) glutaraldehyde aqueous solution for crosslinking for 12 h; then it was thoroughly washed with deionized water and dried to obtain a catalytic functional film, denoted as M6.

[0056] Comparative Example 1 In this comparative example, pure quaternized chitosan membranes were prepared without catalyst loading in step (2), and the remaining steps were the same as in Example 1; the resulting membrane was denoted as C1.

[0057] Comparative Example 2 This comparative example uses a physically mixed ZnCo-LDH loading method: (1) Take 0.5g Zn(NO3)2·6H2O, 1.0g Co(NO3)2·6H2O (Zn 2+ Co 2+ 1.0 g of urea and 1.0 g of urea were dissolved in 20 mL of deionized water. The two solutions were mixed and stirred for 2 h, then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and hydrothermally reacted at 150 °C for 12 h to obtain pure ZnCo-LDH powder. (2) Then weigh 0.5g of quaternized chitosan and 0.25g of pure ZnCo-LDH powder from step (1) of Example 1, disperse them in 10mL of 2% (v / v) acetic acid and sonicate for 2h to obtain casting solution; (3) The subsequent film formation and crosslinking steps are the same as in Example 4; the resulting film is labeled C2.

[0058] Comparative Example 3 The difference between this comparative example and Example 1 is that the temperature of the hydrothermal reaction in step (2) is 200°C, while the rest is the same as in Example 1; the resulting membrane is labeled C3.

[0059] Comparative Example 4 The difference between this comparative example and Example 1 is that the temperature of the hydrothermal reaction in step (2) is 100°C, while the rest is the same as in Example 1; the resulting membrane is labeled C4.

[0060] Comparative Example 5 The difference between this comparative example and Example 1 is that the hydrothermal reaction time in step (2) is 36 hours, while the rest is the same as in Example 1; the resulting membrane is labeled C5.

[0061] Comparative Example 6 The difference between this comparative example and Example 1 is that the hydrothermal reaction time in step (2) is 3 hours, while the rest is the same as in Example 1; the resulting membrane is labeled C6.

[0062] Comparative Example 7 The difference between this comparative example and Example 6 is that in step (2), 0.05g of commercial nano-SrO (5% loading) was added, while the rest were the same as in Example 1; the resulting membrane was labeled C7.

[0063] Comparative Example 8 The difference between this comparative example and Example 5 is that in step (2), 0.4g of commercial nano-MgO (with a loading of 80%) was added, while the rest were the same as in Example 1; the resulting membrane was labeled C8.

[0064] Comparative Example 9 The difference between this comparative example and Example 1 is that in step (1), 0.92g of GTMAC (the molar ratio of GTMAC to chitosan structural units is 0.5:1) is added, and the rest is the same as in Example 1; the resulting film is labeled C9.

[0065] Comparative Example 10 The difference between this comparative example and Example 1 is that step (1) involves stirring the reaction at 90°C for 8 hours, while the rest is the same as in Example 1; the resulting membrane is labeled C10.

[0066] Comparative Example 11 The difference between this comparative example and Example 1 is that step (1) involves stirring the reaction at 70°C for 2 hours, while the rest is the same as in Example 1; the resulting membrane is labeled C11.

[0067] Comparative Example 12 The difference between this comparative example and Example 1 is that in step (3), the glutaraldehyde concentration is 0.2% (v / v), and the crosslinking time is 4h. The rest are the same as in Example 1. The resulting film is labeled as C12.

[0068] Comparative Example 13 The difference between this comparative example and Example 1 is that in step (3), the glutaraldehyde concentration is 8% (v / v), and the crosslinking time is 4h. The rest are the same as in Example 1. The resulting film is labeled C13.

[0069] Comparative Example 14 The difference between this comparative example and Example 1 is that in step (3), the glutaraldehyde concentration is 2% (v / v), and the crosslinking time is 0.5 h. The rest are the same as in Example 1. The resulting film is labeled C14.

[0070] Comparative Example 15 The difference between this comparative example and Example 1 is that in step (3), the glutaraldehyde concentration is 2% (v / v), and the crosslinking time is 24h. The rest are the same as in Example 1. The resulting film is labeled as C15.

[0071] To verify the catalytic activity, mechanical properties, and stability of the catalytic functional membranes prepared in the embodiments and comparative examples of the present invention, the following performance characterization and application tests were conducted.

[0072] 1) Determination of tensile strength: According to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", the catalytic functional film was cut into long strips (40 mm × 10 mm) and tested at room temperature (25℃) at a rate of 5 mm / min using a universal testing machine. Five parallel samples were tested in each group.

[0073] 2) Ionic conductivity test: The membrane sample (1 cm in diameter) was assembled into a symmetrical "electrode|membrane|electrode" test cell using the AC impedance method. The test was conducted at 65°C with an AC perturbation amplitude of 5-10 mV and a frequency of 0.1 Hz - 1 MHz.

[0074] 3) Test of batch reaction yield: Soybean oil (acid value ≤0.2 mg KOH / g, containing ≤0.2% free fatty acids), methanol (oil-to-methanol molar ratio of 6:1) and catalytic membrane were added to a batch reactor. After reacting at 65°C for 7 hours, the upper oil phase was collected for analysis.

[0075] 4) Test of catalytic leaching rate: The mixture of feed oil and methanol (oil-methanol molar ratio of 6:1) was pumped into the membrane reactor at a flow rate of 1 mL / min. After running continuously for 200 h under the set conditions, the sample was collected and the ion concentration in the solution was determined using an atomic absorption spectrometer.

[0076] In addition, for the catalytic functional membrane prepared in Example 1, the present invention replaced soybean oil (acid value ≤0.2 mg KOH / g, containing ≤0.2% free fatty acids) with waste cooking oil (filtered through a 120-mesh sieve to remove large particulate solid impurities such as food residues, without any chemical refining treatment such as deacidification and dehydration, acid value 25 mg KOH / g, containing 12.5 wt% free fatty acids) and tested the batch reaction yield and catalytic leaching rate.

[0077] The membranes obtained in the above embodiments and comparative examples were characterized for performance and applied for testing. The results are summarized in Table 1.

[0078] Table 1. Comparison of performance parameters of catalytic functional membranes prepared in the embodiments and comparative examples of the present invention.

[0079] Table 1 shows that the membranes in the embodiments of the present invention exhibit excellent overall performance. The catalyst leaching rates of membranes M1, M2, and M3, prepared using the in-situ hydrothermal growth method, are an order of magnitude lower than that of the C2 membrane prepared using the simple physical mixing method in Comparative Example 2. This directly proves the chemical bonding and structural interlocking between the ZnCo-LDH formed by the in-situ growth strategy and the quaternized chitosan, fundamentally solving the problem of catalyst detachment caused by weak interactions in traditional physical loading. Furthermore, after 200 hours of continuous operation using high-acid-value waste oil from catering, the leaching rate of membrane M1 remained <0.5%, and the yield remained stable at 95.0%, verifying the membrane's excellent long-term operational stability.

[0080] All in-situ grown films (M1, M2, M3) exhibited significantly higher ionic conductivity than the pure quaternized film C1 in Comparative Example 1, indicating that the introduction of LDH and the quaternized matrix synergistically optimized the ion transport pathway. Simultaneously, these films maintained high catalytic activity. This demonstrates that the porous structure formed by LDH nanosheets and the polymer network within the film simultaneously serves as a highly efficient ion / molecular mass transfer channel and a high specific surface area catalytic active center, achieving "instant catalysis and transport" and avoiding the contradiction of high-loading densification.

[0081] In summary, the M1 membrane achieved a biodiesel yield of up to 95.8% when processing feedstocks containing free fatty acids; even when using waste cooking oil with higher acid values ​​and more complex compositions, its continuous operation yield remained stable at 95.0%. This demonstrates that the membrane can simultaneously and efficiently process free fatty acids (FFA) and triglycerides (TG), converting FFA into biodiesel through esterification and TG through transesterification. This membrane can directly, continuously, efficiently, and stably convert complex, high-acid-value real waste oils, eliminating the need for pretreatment, greatly expanding feedstock sources and simplifying the process. In contrast, the C1 membrane prepared in Comparative Example 1 showed almost no catalytic activity, proving that the quaternary ammonium base alone has limited effect.

[0082] Comparative Examples 3-6 show that too low an in-situ hydrothermal reaction temperature or too short a time will lead to poor crystallization and a sharp drop in activity and conductivity; too high a temperature may damage the matrix, making the film brittle and causing overall performance degradation.

[0083] Comparative Examples 7-8 show that if the loading of the nano-solid base catalyst is too low, the activity will be severely insufficient; if it is too high, it will lead to agglomeration, film embrittlement, a sharp increase in leaching, and a decrease in activity.

[0084] Comparative Examples 12-15 showed that insufficient crosslinking led to a loose membrane network, resulting in severe catalyst leaching and structural failure during long-term operation; while excessive crosslinking caused the membrane to become brittle, its conductivity to plummet, and its mass transfer capacity to be sacrificed.

[0085] The tensile strength of the membranes in all embodiments was generally higher than that in the comparative example, indicating that functional membranes with excellent mechanical properties can be prepared using high-deacetylated black soldier fly chitosan as a matrix, combined with optimized in-situ or blending composite and crosslinking processes, thus ensuring their assembly and long-term operation in membrane modules. This invention, through systematic innovation in materials, methods, structures, and processes, successfully prepared a catalytic functional membrane based on black soldier fly chitosan. This membrane not only exhibits good mechanical and ion conductivity but also demonstrates high catalytic activity and excellent operational stability in biodiesel production. This provides a novel technical path and material solution for the green and continuous production of biodiesel.

[0086] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a chitosan-based catalytic functional membrane from black soldier fly larvae, characterized in that, Includes the following steps: S1. Quaternization modification of black soldier fly chitosan to obtain quaternized chitosan; S2. The catalytically active component is loaded onto the quaternized chitosan to obtain a catalyst-loaded complex; the catalytically active component is a layered bimetallic hydroxide or a nano-solid base catalyst. S3. The composite is formed into a membrane and cross-linked and cured to obtain the catalytic functional membrane.

2. The preparation method according to claim 1, characterized in that, The layered bimetallic hydroxide includes ZnCo-LDH, and the layered bimetallic hydroxide is loaded onto the quaternized chitosan by in-situ hydrothermal growth.

3. The preparation method according to claim 1, characterized in that, The nano-solid base catalyst is selected from at least one of nano-CaO, nano-MgO or nano-SrO, and the nano-solid base catalyst is loaded into the quaternized chitosan by physical blending.

4. The preparation method according to claim 2, characterized in that, The in-situ hydrothermal growth method includes: S2-1. Dissolve zinc salt, cobalt salt and urea in water to form a precursor solution; S2-2. Dissolve the quaternized chitosan obtained in step S1 and mix it with the precursor solution; S2-3. The mixed solution is subjected to a hydrothermal reaction.

5. The preparation method according to claim 4, characterized in that, Zn in zinc salt 2+ Co in cobalt salts 2+ The molar ratio is (0.5-3):1; the mass ratio of the quaternized chitosan, the total mass of the zinc salt and cobalt salt and the mass of urea is 1:(2-3):(1.6-2.4).

6. The preparation method according to claim 4, characterized in that, The hydrothermal reaction is carried out at a temperature of 120-180℃ for 6-24 hours.

7. The preparation method according to claim 3, characterized in that, The amount of the nano-solid base catalyst used is 10%-60% of the mass of quaternized chitosan.

8. The preparation method according to claim 1, characterized in that, In step S1, the quaternizing agent used in the quaternization modification is selected from at least one of 2,3-epoxypropyltrimethylammonium chloride and chloroacetamide, and the molar ratio of the quaternizing agent to the chitosan structural unit is (1-3):

1.

9. A chitosan-based catalytic functional membrane of black soldier fly larvae obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the black soldier fly chitosan-based catalytic functional membrane as described in claim 9 in the preparation of biodiesel, characterized in that, The feedstock oil used to prepare the biodiesel contains free fatty acids and triglycerides.

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