Conductive heterojunction catalyst, preparation method and catalytic reaction device

Abstract

The invention provides a conductive heterojunction catalyst, a preparation method and a catalytic reaction device. The preparation method comprises the following steps: adding a molecular sieve into a mixed solution of a cationic polymer and a sulfonic acid group-containing anionic polyelectrolyte, and mixing to obtain a modified molecular sieve; chitosan and the modified molecular sieve are subjected to crosslinking treatment, a composite material is obtained, the composite material is sintered in a protective atmosphere, and the conductive heterojunction catalyst is obtained. The conductive heterojunction catalyst obtained by the preparation method provided by the invention is high in conductivity, excellent in catalytic performance and stable in structure, and can be used for converting electric heat into energy supply for reaction and reducing carbon emission.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more particularly to a conductive heterojunction catalyst, its preparation method, and a catalytic reaction apparatus. Background Technology

[0002] In petrochemical processes, traditional fossil fuel heating suffers from low thermal efficiency, high carbon emissions, and slow temperature response. With the rapid development of renewable energy, the capacity for clean electricity supply has significantly improved. Driven by the "dual carbon" goal (carbon reduction and emission reduction), introducing electricity into petrochemical production and using it to directly drive catalytic reactions, replacing traditional combustion heating with electrothermal catalysis technology, can substantially reduce carbon emissions and improve energy efficiency.

[0003] Molecular sieves are microporous materials with a regular pore structure, widely used in petrochemical and fine chemical reactions such as catalytic cracking, isomerization, aromatization, and hydrocracking. The electrical conductivity of molecular sieves is very close to that of insulators, which limits their application in electro-driven catalytic systems, requiring external heating for the catalytic reaction. Traditional conductive additives typically use metal catalysts, but when applied to molecular sieve catalytic reaction systems, they are prone to high-temperature deactivation, resulting in decreased structural stability of the molecular sieve while providing conductivity.

[0004] Therefore, developing a highly conductive and stable molecular sieve catalyst to enable electric power supply is a key requirement for the green transformation of the petrochemical industry. Summary of the Invention

[0005] This invention provides a method for preparing a conductive heterojunction catalyst. The conductive heterojunction catalyst obtained by this method has a stable structure, high conductivity, and excellent catalytic performance, enabling efficient electrothermal conversion to provide energy for the reaction and reduce carbon emissions. This method overcomes the conductivity bottleneck of molecular sieves in electro-driven catalysis, providing a solution for preparing efficient, low-carbon catalytic materials for the green transformation of the petrochemical industry.

[0006] The present invention also provides a conductive heterojunction catalyst, which has a stable structure, high conductivity, excellent catalytic performance, and can achieve efficient electrothermal conversion.

[0007] The present invention also provides a catalytic reaction apparatus, which can be loaded with the above-mentioned conductive heterojunction catalyst to carry out a catalytic reaction, thereby providing a reaction apparatus for the catalytic reaction.

[0008] In a first aspect, the present invention provides a method for preparing a conductive heterojunction catalyst, comprising the following steps:

[0009] Molecular sieves are added to a mixture of cationic polymers and anionic polyelectrolytes containing sulfonic acid groups, and the mixture is then treated to obtain modified molecular sieves.

[0010] Chitosan is cross-linked with the modified molecular sieve to obtain a composite material, which is then sintered in a protective atmosphere to obtain the conductive heterojunction catalyst.

[0011] Further, the cationic polymer comprises at least one of: polydiallyldimethylammonium chloride, polydimethylaminoethyl methacrylate, poly(acrylamide-co-dimethylaminopropylacrylamide), and polyethyleneimine;

[0012] Preferably, based on the mass of the mixture, the cationic polymer has a mass fraction of 1 to 10 wt.%.

[0013] Furthermore, the sulfonic acid-containing anionic polyelectrolyte comprises at least one of: sodium terephthalate sulfonate, poly(2-acrylamide-2-methylpropanesulfonic acid), and sulfonated styrene-maleic anhydride copolymer.

[0014] Preferably, based on the mass of the mixture, the mass fraction of the sulfonic acid-containing anionic polyelectrolyte is 1~10 wt.%.

[0015] Further, the sintering process includes: heating to 450-800 ℃ at a heating rate of 1-10 ℃ / min under the protective atmosphere, and holding at that temperature for 3-5 h;

[0016] Preferably, the protective atmosphere includes at least one of N2, H2, Ar, and He.

[0017] Further, the crosslinking treatment includes the following steps:

[0018] The first mixture includes the modified molecular sieve and the solvent;

[0019] The chitosan and acid solution are mixed to obtain a second mixture, and the pH value of the second mixture is adjusted to 2.26~2.76;

[0020] Mix the first mixture, the second mixture, and the crosslinking agent, and adjust the pH of the mixture to 8-10;

[0021] Preferably, the solvent comprises a dispersant and a surfactant, wherein the volume ratio of the dispersant to the surfactant is (10~50):1;

[0022] Preferably, the acid solution has a mass fraction of 1~10 wt.%;

[0023] Preferably, the second mixture is added dropwise to the first mixture.

[0024] Furthermore, the dispersant comprises at least one of the following: dimethyl silicone oil, cyclomethyl silicone oil, polybutene, liquid paraffin, and fatty acid ester;

[0025] The surfactant comprises at least one of lauryl glucoside, Tween 20, Tween 40, Tween 60, Span 20, Span 40, Span 60, and F127.

[0026] The crosslinking agent comprises at least one of glyoxal, acrolein, glutaraldehyde, ethylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether.

[0027] Furthermore, the mass ratio of chitosan to the modified molecular sieve is 1:(0.2~2).

[0028] Furthermore, the molecular sieve includes at least one of ZSM molecular sieve, Beta molecular sieve, SAPO molecular sieve, MOR molecular sieve, and Y-type molecular sieve.

[0029] In a second aspect, the present invention provides a conductive heterojunction catalyst obtained by the preparation method of the conductive heterojunction catalyst described in the first aspect.

[0030] Thirdly, the present invention provides a catalytic reaction apparatus comprising a power source, an insulated reactor, and a catalytic bed, wherein the catalytic bed is disposed within the insulated reactor; the catalytic bed comprises the conductive heterojunction catalyst described in the first aspect.

[0031] This invention first modifies a molecular sieve using a cationic polymer and an anionic polyelectrolyte containing sulfonic acid groups, giving its surface charged functional groups. Then, chitosan is cross-linked with the modified molecular sieve. The charged functional groups and chitosan molecules form a tight interface through electrostatic attraction, hydrogen bonding, and cross-linking reactions, thus cross-coating the chitosan onto the surface of the modified molecular sieve to obtain a composite material. This composite material is then sintered in a protective atmosphere to carbonize the chitosan, forming a conductive carbon-based phase. This phase, along with the molecular sieve phase, constitutes two phase regions with different properties, and the two phases are stably bonded together through the aforementioned tight interface, thereby forming a conductive heterojunction structure to obtain the conductive heterojunction catalyst. The conductive heterojunction catalyst prepared by the method described above has a structure in which carbonized chitosan encapsulates a molecular sieve. The tight heterojunction interface, constructed through ionic bonds or van der Waals forces, strengthens the interfacial electron migration pathway between the carbon material and the molecular sieve. This not only solves the problem of poor conductivity of the molecular sieve but also promotes the reaction. Therefore, the conductive heterojunction catalyst possesses the characteristics of structural stability, high conductivity, and excellent catalytic performance, enabling efficient electrothermal conversion into reaction energy. Compared to traditional fuel heating, its electrically driven system has lower carbon emissions, higher thermal efficiency, faster thermal response, and superior catalytic performance. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely 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 A schematic diagram of a catalytic reaction apparatus for a specific embodiment;

[0034] Figure 2 This is an infrared thermal image of the catalytic reaction apparatus of Example 1;

[0035] Figure 3 The images show the XRD patterns of the conductive heterojunction catalyst obtained in Example 1 and the commercially available ZSM-5 molecular sieve. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In a first aspect, the present invention provides a method for preparing a conductive heterojunction catalyst, comprising the following steps:

[0038] Molecular sieves are added to a mixture of cationic polymers and anionic polyelectrolytes containing sulfonic acid groups, and the mixture is then treated to obtain modified molecular sieves.

[0039] Chitosan and modified molecular sieves were cross-linked to obtain a composite material, which was then sintered in a protective atmosphere to obtain a conductive heterojunction catalyst.

[0040] This invention modifies molecular sieves with cationic polymers and sulfonic acid-containing anionic polyelectrolytes, introducing stable charged functional groups (such as sulfonic acid groups and quaternary ammonium groups) on their surface. Subsequently, in the cross-linking treatment with chitosan, the above-mentioned charged functional groups and chitosan molecules form a tight interface through electrostatic attraction, hydrogen bonding and cross-linking reaction. After sintering in a protective atmosphere, chitosan carbonizes to form a conductive carbon-based phase, which constitutes two phase regions with different properties with the molecular sieve phase. The two phases are stably bonded to each other through the above-mentioned tight interface, thereby forming a conductive heterojunction structure.

[0041] In the above preparation process, the sulfonic acid-containing anionic polyelectrolyte, through synergistic action with the cationic polymer, achieves efficient modification of the molecular sieve surface. It can introduce stable charged functional groups (such as sulfonic acid groups and quaternary ammonium groups) on the molecular sieve surface. These charged functional groups can form strong interactions (electrostatic attraction and hydrogen bonding) with the subsequent chitosan, avoiding the problem of "loose interfacial bonding" during subsequent composite formation and providing a precursor for the tight interface of the heterostructure. At the same time, the modified layer formed on the molecular sieve surface by the cationic polymer and the sulfonic acid-containing anionic polyelectrolyte can reduce the agglomeration of molecular sieve particles, enabling uniform dispersion during subsequent composite formation with chitosan. Ultimately, the carbonized chitosan can uniformly encapsulate the molecular sieve, avoiding the defect of "uneven conductivity caused by local lack of carbon material coverage".

[0042] In some preferred embodiments, the above mixing process includes: stirring for 0.5 to 6 hours, centrifugation, and drying to obtain the modified molecular sieve.

[0043] Stirring promotes mass transfer, ensuring that the cationic polymer and the anionic polyelectrolyte containing sulfonic acid groups interact fully and uniformly with the surface of the molecular sieve, allowing the molecules of the cationic polymer and the anionic polyelectrolyte containing sulfonic acid groups to be uniformly adsorbed onto the surface of the molecular sieve.

[0044] For example, the stirring time is 0.5 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, and 6 h.

[0045] After stirring, not all cationic polymers and anionic polyelectrolytes containing sulfonic acid groups adsorb onto the molecular sieve surface; a large amount of unbound free polyelectrolytes remain dissolved in the water. Therefore, centrifugation removes these free impurities, separating pure modified molecular sieve solids. This prevents these free polyelectrolytes from adhering to the molecular sieve surface and clogging the sieve pores during subsequent drying, thus affecting performance. Drying removes moisture from the surface and interior of the molecular sieve, making the bond between the polyelectrolytes and the molecular sieve more stable, fixing the modified layer, and stabilizing the structure of the modified molecular sieve.

[0046] The modified molecular sieve is then combined with chitosan to obtain a composite material, which is finally sintered in a protective atmosphere. On one hand, the carbon material formed by the sintering and carbonization of chitosan possesses excellent electrical conductivity and can tightly encapsulate the surface of the modified molecular sieve, forming a "carbon material-molecular sieve" conductive network. This improves the "electron transport obstruction" problem caused by the insulation of traditional molecular sieve catalysts, providing a foundation for electrothermal conversion, electrocatalysis, and other applications. On the other hand, the composite material, after sintering, forms a stable "carbon material-molecular sieve" heterojunction structure. Specifically, the charged functional groups on the surface of the modified molecular sieve and the carbon material can be tightly bound together through ionic bonds (such as the interaction between sulfonic acid groups and the surface charge of the carbon material) or van der Waals forces. This strong interfacial interaction enhances the electron migration path—electrons can be rapidly transferred between the carbon material and the molecular sieve. This can activate the reactants and promote the forward reaction.

[0047] The preparation process provided by this invention uses readily available and cost-controllable raw materials, is simple to operate, and is easy to scale up. Specifically, the cationic polymer, sulfonic acid-containing anionic polyelectrolytes, and molecular sieves are all conventional raw materials in the chemical industry, requiring no special customization, thus reducing production costs. Stirring, centrifugation, drying, and protective atmosphere sintering are all mature chemical unit operations, requiring no extreme reaction conditions (such as ultra-high temperature and ultra-high pressure), with low equipment requirements, facilitating large-scale production.

[0048] In some embodiments, the cationic polymer comprises at least one of: polydiallyldimethylammonium chloride, polydimethylaminoethyl methacrylate, poly(acrylamide-co-dimethylaminopropylacrylamide), and polyethyleneimine;

[0049] Preferably, based on the mass of the mixture, the cationic polymer mass fraction is 1~10 wt.%.

[0050] The cationic polymer molecular chain contains a large number of positively charged functional groups, which interact with the weakly negative potential sites (Si-O) on the molecular sieve surface. - Or Al-O - This generates a strong electrostatic attraction, driving the cationic polymer molecular chains to adsorb and anchor at multiple points on the molecular sieve surface primarily through electrostatic interactions and assisted by hydrogen bonding. For example, the cationic group -N... + R3 and the negatively charged oxygen atoms Si-O on the surface of the molecular sieve - The amino-NH2 groups in the cationic polymer molecular chain form stable electrostatic bonds. +- Imine-NH- groups can form hydrogen bonds (-NH…O-Si-) with undissociated Si-OH groups on the molecular sieve surface, further enhancing adsorption stability. A cationic polymer mass fraction of 1–10 wt.% ensures adequate adsorption, prevents polymer chains from self-aggregating in solution, guarantees a continuous coating layer, and improves the effective binding efficiency with the molecular sieve surface. By selecting cationic polymers with different charge densities and molecular weights, the charge density of the modified molecular sieve surface can be controlled. For example, polyethyleneimine, due to its branched structure, provides a higher amino density, making it suitable for applications requiring stronger surface functionalization. The cationic polymer removes unadsorbed free polymers, ensuring the purity of the modified molecular sieve.

[0051] In some embodiments, when polydiallyldimethylammonium chloride is used as a cationic polymer, its quaternary ammonium salt structure forms a stable ion exchange interaction with the silica framework of the molecular sieve, enabling the modified molecular sieve to maintain good stability in the pH range of 2 to 10.

[0052] For example, the cationic polymer concentration is 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, preferably 5 wt.%.

[0053] In some embodiments, the sulfonic acid-containing anionic polyelectrolyte comprises at least one of: sodium poly(2-acrylamide-2-methylpropanesulfonic acid), poly(2-acrylamide-2-methylpropanesulfonic acid), and sulfonated styrene-maleic anhydride copolymer.

[0054] Preferably, based on the mass of the mixture, the mass fraction of the anionic polyelectrolyte containing sulfonic acid groups is 1~10 wt.%.

[0055] In some embodiments, a certain mass of cationic polymer and sulfonic acid-containing anionic polyelectrolyte are weighed and dissolved in water to form an aqueous solution of cationic polymer and sulfonic acid-containing anionic polyelectrolyte, wherein the mass fraction of cationic polymer in the aqueous solution is 1~10 wt.% and the mass fraction of sulfonic acid-containing anionic polyelectrolyte in the aqueous solution is 1~10 wt.%.

[0056] The sulfonic acid groups on the sulfonic acid-containing anionic polyelectrolyte molecular chains carry a strong negative charge, which combines with the positively charged groups of the cationic polymer already anchored on the molecular sieve surface through ionic bonds. Simultaneously, through chain segment entanglement, the flexible segments of the two polymer molecular chains intertwine, further consolidating the composite layer structure and preventing the shedding of a single polymer layer due to charge repulsion, thus forming a "cationic polymer-anionic polyelectrolyte" composite layer. For example, the positively charged group -N... + R3 and sulfonic acid group -SO3 -Stable ion pairs -N are formed through electrostatic interactions. + R3… - O3S- allows the anionic polyelectrolyte to bind tightly to the surface of the cationic polymer layer. When the cationic polymer mass fraction is 1~10 wt.%, the problem of molecular sieve pore blockage due to imbalance can be avoided, ensuring the formation of a stoichiometric composite layer of appropriate thickness with the cationic polymer.

[0057] For example, the sulfonic acid-containing anionic polyelectrolyte has a mass fraction of 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, preferably 5 wt.%.

[0058] In some preferred embodiments, a certain mass of cationic polymer and anionic polyelectrolyte containing sulfonic acid groups are weighed and dissolved in deionized water, with mass fractions of 1~10 wt.%.

[0059] In this invention, the synergistic effect of the cationic polymer and the sulfonic acid-containing anionic polyelectrolyte utilizes multiple interactions such as electrostatic attraction, hydrogen bonding, and chain segment entanglement to stably introduce charged functional groups onto the surface of the molecular sieve. This invention does not limit the type of charged functional group; exemplarily, the charged functional group includes sulfonic acid group -SO3. - and quaternary ammonium-N + (CH3)2 - amino-NH2 + - At least one of the following. These charged functional groups not only provide sites for subsequent strong interactions (electrostatic attraction, hydrogen bonding) with chitosan, making the interface compact, but also reduce the agglomeration of molecular sieve particles through charge repulsion, laying the foundation for uniform coating of carbon materials and improving conductivity uniformity.

[0060] For example, polydiallyldimethylammonium chloride (PDDA, a cationic polymer) is mixed with sodium poly(p-styrene sulfonate) (PSS, a sulfonic acid-containing anionic polyelectrolyte), a molecular sieve, and water. PDDA first passes through the quaternary ammonium groups (-N) on its molecular chain. + (CH3)2-) forms an electrostatic adsorption with the negative potential points on the molecular sieve surface, firmly anchoring it to the surface; subsequently, PSS is attracted by the sulfonic acid groups (-SO3) on the molecular chain. - ) forms a strong ionic bond (-N) with the quaternary ammonium group of PDDA. + (CH3)2… -O3S- was used to construct a composite modified layer consisting of an inner PDDA layer and an outer PSS layer. This synergistic effect not only avoids the interlayer looseness caused by the positive repulsion of PDDA itself, but also solves the problem that PSS cannot directly bind to the molecular sieve, significantly enhancing the stability of the modified layer. Finally, charged functional groups quaternary ammonium groups (-N) were introduced onto the surface of the molecular sieve. + (CH3)2-) and sulfonic acid group (-SO3) - Quaternary ammonium group (-N) + (CH3)2-) can form hydrogen bonds with the hydroxyl groups of subsequent chitosan, and the sulfonic acid group (-SO3) - The amino group (-NH3) that can be protonated by chitosan + The electrostatic attraction generated by the catalyst creates a tight interface bond through a dual effect. At the same time, the balance and regulation of positive and negative charges prevents the agglomeration of molecular sieve particles due to excess of a single charge, resulting in uniform dispersion of the molecular sieve particles. This lays the foundation for the complete coating of carbon materials after subsequent chitosan carbonization and effectively improves the conductivity uniformity of the catalyst.

[0061] In some embodiments, the sintering process includes: heating to 450-800 °C at a heating rate of 1-10 °C / min under a protective atmosphere and holding at that temperature for 3-5 h;

[0062] Preferably, the protective atmosphere includes at least one of N2, H2, Ar, and He.

[0063] For example, the heating rate is 1 ℃ / min, 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min, 6 ℃ / min, 7 ℃ / min, 8 ℃ / min, 9 ℃ / min, 10 ℃ / min, preferably 1 ℃ / min.

[0064] For example, the temperature is raised to 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, and 800 ℃.

[0065] For example, the heat preservation time is 3 h, 3.5 h, 4 h, 4.5 h, and 5 h, with 4 h being preferred.

[0066] When the composite material is sintered under a protective atmosphere, it can provide dual protection by isolating oxygen: Firstly, it allows the carbon materials generated by chitosan carbonization (such as amorphous carbon and graphite-like carbon) to remain stable at high temperatures, preventing them from being lost due to oxidation to carbon dioxide or carbon monoxide. This maintains the integrity of the carbon material coating layer and ensures that the conductive network of the "carbon material-molecular sieve" heterojunction is not damaged, allowing it to continue to improve the conductivity of the molecular sieve. Secondly, it maintains the inertness of the high-temperature environment, preventing the silicon-aluminum framework of the molecular sieve from oxidizing and breaking, thus preserving its original structure and activity. This ensures the tight bonding of the heterojunction interface and lays the foundation for functional synergy in catalytic reactions.

[0067] In some implementations, the crosslinking treatment includes the following steps:

[0068] The first mixture includes a modified molecular sieve and a solvent;

[0069] Chitosan and acid solution were mixed to obtain a second mixture, and the pH value of the second mixture was adjusted to 2.26-2.76.

[0070] Mix the first mixture, the second mixture, and the crosslinking agent, and adjust the pH of the mixture to 8-10;

[0071] Preferably, the solvent includes a dispersant and a surfactant, wherein the volume ratio of the dispersant to the surfactant is (10~50):1;

[0072] Preferably, the mass fraction of the acid solution is 1~10 wt.%;

[0073] Preferably, the second mixture is added dropwise to the first mixture.

[0074] In some embodiments, the acid solution includes an acid solute and an acid solvent. The mass fraction of the acid solution is defined as the percentage of the mass of the acid solute relative to the total mass of the acid solution, based on the total mass of the acid solution.

[0075] In this invention, chitosan and acid are mixed to obtain a second mixture, and the pH of the second mixture is adjusted to 2.26-2.76. Chitosan molecules contain a large number of free amino groups (-NH2), which have extremely low solubility under neutral or alkaline conditions, making it difficult to form a homogeneous solution. The acid provides hydrogen ions (H+) to the mixture. + This causes the amino groups of chitosan to be protonated (converted to -NH3). +This significantly enhances its hydrophilicity, thereby promoting the dissolution of chitosan in the solution and forming a stable and homogeneous second mixture. The pH of the second mixture, 2.26-2.76, balances chitosan dissolution efficiency with molecular structural stability. The weakly acidic pH range of 2.26-2.76 ensures sufficient protonation and complete dissolution of chitosan while avoiding molecular chain degradation caused by excessive acidity. This lays the foundation for subsequent cross-linking reactions with the first mixture (containing modified molecular sieves) and cross-linking agents under alkaline conditions (pH 8-10), ensuring the homogeneity and structural stability of the composite material, and ultimately guaranteeing the performance of the final conductive heterojunction catalyst.

[0076] For example, the pH of the second mixture is 2.26, 2.36, 2.46, 2.56, 2.66, or 2.76, preferably 2.56.

[0077] In some preferred embodiments, the method for preparing the first mixture includes the following steps:

[0078] The dispersant and surfactant are mixed and subjected to a first ultrasonic treatment for 0.5–2 h. Then, modified molecular sieves are added and subjected to a second ultrasonic treatment for 5–60 min to obtain a suspension in which the molecular sieves are uniformly dispersed, i.e., the first mixture. The dispersant…

[0079] The volume ratio of surfactant to surfactant is (10~50):1.

[0080] For example, the volume ratio of dispersant to surfactant is 10:1, 20:1, 30:1, 40:1, or 50:1.

[0081] For example, the first ultrasound treatment time is 0.5 h, 1 h, 1.5 h, or 2 h.

[0082] For example, the second ultrasound treatment time is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min.

[0083] In some preferred embodiments, mixing chitosan and acid solution includes: weighing chitosan and adding it to an acetic acid solution with a mass fraction of 1-10 wt.%, followed by a third ultrasonic treatment for 10-60 min to form a uniform and transparent gel.

[0084] For example, the mass fraction of the acid solution is 1 wt.%, 2.5 wt.%, 5 wt.%, 7.5 wt.%, or 10 wt.%.

[0085] For example, the third ultrasound treatment time is 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min.

[0086] In some preferred embodiments, mixing the first mixture, the second mixture, and the crosslinking agent, and adjusting the pH of the mixture to 8-10 includes: adding the second mixture dropwise to the first mixture and stirring for 0.5-4 h; then adding 1-10 mL of the crosslinking agent; finally adding NaOH solution dropwise to the above solution, adjusting the pH to 8-10, reacting at room temperature for 8-20 h, and washing the resulting product thoroughly with acetone, petroleum ether, and deionized water, filtering, and vacuum drying to obtain the composite material, i.e., the composite material is a crosslinked chitosan catalyst coated with molecular sieve.

[0087] For example, the stirring time is 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, and 4 h.

[0088] For example, the volume of the crosslinking agent is 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL, 7 mL, 8 mL, 9 mL, or 10 mL.

[0089] For example, the room temperature reaction time is 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, and 20 h.

[0090] In some embodiments, the dispersant comprises at least one of dimethyl silicone oil, cyclomethyl silicone oil, polybutene, liquid paraffin, and fatty acid ester.

[0091] In some embodiments, the surfactant comprises at least one of lauryl glucoside, Tween 20, Tween 40, Tween 60, Span 20, Span 40, Span 60, and F127.

[0092] In some embodiments, the crosslinking agent comprises at least one of glyoxal, acrolein, glutaraldehyde, ethylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether.

[0093] In this invention, the core function of the acid in the system is to promote the dissolution and dispersion of chitosan. The dispersant, through an inert medium, isolates the modified molecular sieve particles, effectively preventing their aggregation and ensuring uniform dispersion of the particles in the first mixture, thus providing a foundation for sufficient subsequent contact with chitosan. The surfactant reduces the interfacial tension of the first mixture, promoting the compatibility of the dispersant with other components. Simultaneously, by adsorbing onto the surface of the modified molecular sieve and forming steric hindrance, it further enhances the dispersion stability of the particles, preventing sedimentation or aggregation. The crosslinking agent reacts chemically with the active groups of chitosan, promoting the formation of a three-dimensional crosslinked network, strengthening the interfacial bonding between chitosan and the modified molecular sieve, and ensuring a robust and stable coating structure.

[0094] For example, chitosan molecules contain a large number of amino groups (-NH2). Under acidic conditions (pH 2.26-2.76) regulated by acid, these amino groups will protonate to form positively charged -NH3. + This not only promotes the dissolution of chitosan to form a homogeneous solution, but also activates the reactivity of amino groups through protonation. When the crosslinking agent glutaraldehyde is added subsequently, the protonated amino groups and the aldehyde group (-CHO) of the crosslinking agent are more likely to undergo Schiff base reaction to form C=N bonds, which accelerates the formation of the crosslinking network. At the same time, the acidic environment can inhibit the self-polymerization of the crosslinking agent, ensuring that it preferentially binds to the amino groups of chitosan. Ultimately, this promotes the chitosan to be firmly coated on the surface of the modified molecular sieve through efficient crosslinking, avoiding the loose coating caused by simple physical mixing.

[0095] In some preferred embodiments, the dispersant is any two of the following: dimethyl silicone oil, cyclomethyl silicone oil, polybutene, liquid paraffin, and fatty acid ester.

[0096] For example, when the dispersant is a mixture of dimethyl silicone oil and liquid paraffin, the two can enhance the dispersion effect through complementary properties. Specifically, dimethyl silicone oil has strong chemical inertness and moderate viscosity, which can form a stable isolation film on the surface of modified molecular sieve particles, effectively preventing particle agglomeration through steric hindrance; liquid paraffin has excellent fluidity, which can reduce the overall viscosity of the system, promote the rapid diffusion of modified molecular sieves in the mixture, and avoid local accumulation. Under the synergistic effect of dimethyl silicone oil and liquid paraffin, the strong isolation stability of dimethyl silicone oil is retained, while the fluidity of liquid paraffin improves the dispersion efficiency. This allows the modified molecular sieves to achieve "uniform dispersion and long-term stable non-settling" in the first mixture, providing a foundation for sufficient contact and uniform coating with chitosan in the second mixture, and ultimately helping the carbon material form a continuous and complete conductive network after sintering.

[0097] In some preferred embodiments, the surfactant is any two of lauryl glucoside, Tween 20, Tween 40, Tween 60, Span 20, Span 40, Span 60, and F127.

[0098] For example, when Tween 20 and Span 20 are used as surfactants, they can complement each other through their hydrophilic-lipophilic balance (HLB) values ​​to enhance dispersion stability: Tween 20 is a hydrophilic nonionic surfactant with a high HLB value, which can adsorb onto the surface of the modified molecular sieve to increase its hydrophilicity, reduce the interfacial tension with the aqueous phase component, and prevent particles from agglomerating due to hydrophobic interactions; Span 20 is a lipophilic nonionic surfactant with a low HLB value, which can be well compatible with the dispersant in the system and enhance the wetting and encapsulation ability of the oil phase on the particles. The synergistic effect of the two can improve the dispersion uniformity of the modified molecular sieve in the oil-water mixture and form a more stable steric hindrance layer through synergistic adsorption, preventing particle sedimentation or aggregation, thus laying the foundation for sufficient contact and uniform coating with chitosan.

[0099] Adding the second mixture dropwise to the first mixture allows for multiple optimizations through precise control of the contact rate. Firstly, since the second mixture contains chitosan, dropwise addition prevents a sudden increase in chitosan concentration in the first mixture, thus preventing agglomeration due to excessive intermolecular forces and ensuring uniform dispersion for sufficient contact with the modified molecular sieve. Secondly, the dropwise addition method allows for gradual interaction between chitosan and the charged functional groups on the surface of the modified molecular sieve, ensuring uniform adsorption of chitosan by each molecular sieve particle. This avoids excessive or insufficient adsorption in certain areas, ultimately forming a complete and uniformly structured composite material. This lays the foundation for subsequent sintering to form a continuous "carbon-molecular sieve" heterostructure and improve conductivity uniformity.

[0100] In some preferred embodiments, the mass ratio of chitosan to modified molecular sieve is 1:(0.2~2).

[0101] For example, the mass ratio of chitosan to modified molecular sieve is 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, or 1:2.0, preferably 1:0.2.

[0102] In a preferred embodiment, the molecular sieve comprises at least one of ZSM molecular sieve, Beta molecular sieve, SAPO molecular sieve, MOR molecular sieve, and Y-type molecular sieve.

[0103] In some embodiments, the silica-to-alumina ratio of ZSM series molecular sieves is 25~1000, the silica-to-alumina ratio of Beta series molecular sieves is 20~100, the silica-to-alumina ratio of SAPO series molecular sieves is 0.4~0.8, the silica-to-alumina ratio of MOR series molecular sieves is 4.17~5, and the silica-to-alumina ratio of Y series molecular sieves is 2.5~6.

[0104] As for the particle size of the molecular sieve, the present invention does not impose any particular limitation. For example, the particle size of the molecular sieve is 0.01 μm to 10 μm.

[0105] In this invention, the aforementioned molecular sieve, as the core catalytic center of the conductive heterojunction catalyst, not only achieves shape-selective sieving by relying on regular channels, allowing only reactants of matching size to enter and suppressing macromolecular side reactions to improve selectivity; it can also customize acidic sites (Brønsted acid / Lewis acid) by adjusting the silicon-aluminum ratio, ion exchange, etc., to adapt to the activity requirements of different reactions and avoid over-reaction or insufficient activity; the high specific surface area of ​​the molecular sieve makes the active sites highly dispersed, reducing waste and improving reaction efficiency; the silicon-aluminum-oxygen framework has strong stability, can withstand harsh reaction conditions, and extend catalyst lifetime.

[0106] By selecting molecular sieves with different pore structures, the diffusion pathways and active site distribution of catalytic reactions can be controlled.

[0107] For example, when ZSM-5 molecular sieve (silicon-to-aluminum ratio 300) is used, its through-hole structure allows 1-hexene molecules to diffuse rapidly to the active sites, which significantly improves the selectivity of low-carbon olefins in the cracking reaction.

[0108] For example, for aromatization reactions, Beta molecular sieves (silicon-to-aluminum ratio 50) are preferred, as their three-dimensional cross-channel structure can effectively accommodate macromolecular intermediates and improve benzene selectivity.

[0109] Molecular sieves are synergistically modified with cationic polymers and sulfonic acid-containing anionic polyelectrolytes to introduce stable charged functional groups onto their surface. These functional groups bind to chitosan through electrostatic attraction and hydrogen bonding, and are then cured with a crosslinking agent to form a uniform crosslinked chitosan coating layer. Subsequently, sintering is performed in a protective atmosphere, where the chitosan carbonizes to form carbon material, ultimately forming a tightly connected heterojunction of "carbon material-molecular sieve". The conductive network of the carbon material obtained after sintering and carbonization of the molecular sieve and chitosan is anchored by the modified functional groups, resulting in a strong and non-loose interfacial bond. This allows for efficient electron and heat transfer while simultaneously fixing the sieve itself, making it suitable for various reactions such as cracking, isomerization, and aromatization, achieving highly efficient, highly selective, and long-life catalytic processes. Consequently, the conductive heterojunction catalyst containing the aforementioned molecular sieve exhibits a stable structure, high conductivity, and excellent catalytic performance, and can be powered via electrothermal conversion.

[0110] For example, the structure of the obtained carbon material is at least one of a composite form or a single form of graphite-like carbon and amorphous carbon.

[0111] In some embodiments, the pore structure of the molecular sieve includes micropores and mesopores.

[0112] In a second aspect, the present invention provides a conductive heterojunction catalyst obtained by the preparation method of the conductive heterojunction catalyst of the first aspect.

[0113] The conductive heterojunction catalyst provided by this invention comprises: a modified molecular sieve and a carbon material generated by the carbonization of chitosan. The surface of the modified molecular sieve contains charged functional groups, and the carbon material is loaded onto at least a portion of the surface of the modified molecular sieve through these charged functional groups. The carbon material exhibits excellent conductivity and, through continuous and strong interactions with the charged functional groups, is firmly loaded onto the surface of the molecular sieve, forming a heterojunction structure and simultaneously creating a continuous conductive network. This network solves the insulation problem of the molecular sieve, and when the reaction system is energized, electrons can be rapidly transferred along the carbon material to the active sites of the molecular sieve, activating the catalytic reaction. This improves the electronic accessibility of the active sites and ensures efficient mass transfer of reactants through the pores of the molecular sieve. Furthermore, the strong interactions significantly inhibit carbon material shedding, greatly improving the cycle stability of the catalyst.

[0114] Chitosan molecules contain a large number of amino groups (-NH2) and hydroxyl groups (-OH), among which the amino groups are easily protonated under acidic conditions to form -NH3. + It can react with negatively charged functional groups on the surface of modified molecular sieves (such as sulfonic acid groups -SO3). - The chitosan generates a strong electrostatic attraction, while the hydroxyl groups form dense hydrogen bonds with the hydroxyl groups (Si-OH) on the surface of the molecular sieve. This strong interfacial interaction allows chitosan to tightly coat the molecular sieve before carbonization, reducing the risk of subsequent carbon material detachment.

[0115] Meanwhile, because chitosan contains nitrogen, nitrogen atoms can be retained in the carbon framework during carbonization to form nitrogen doping, which can significantly increase the carrier concentration of carbon materials, enhance conductivity, and enable heteroatom functionalization. In addition, the rigid structure of chitosan macromolecular chains easily forms partially graphite-like carbon microcrystals after carbonization, constructing a more continuous electron transport path.

[0116] In this invention, the amino groups of chitosan can undergo a Schiff base reaction with a crosslinking agent (such as glutaraldehyde) to rapidly form a three-dimensional crosslinked network. This fixes the coating morphology before carbonization, avoids carbon layer defects caused by molecular chain aggregation, improves the crosslinking efficiency with the modified molecular sieve, and enhances the uniformity of the final carbon material dispersion on the surface of the modified molecular sieve.

[0117] In a preferred embodiment, before carbonization, chitosan uniformly coats the surface of the modified molecular sieve and partially penetrates into the pores through electrostatic attraction and hydrogen bonding of charged functional groups on the surface of the modified molecular sieve. After carbonization by sintering, the carbon material is distributed on the surface of the modified molecular sieve and some of the pores, forming a continuous coating layer. It is also firmly bonded to the molecular sieve framework through charged functional groups, forming a tightly bonded heterojunction structure. Finally, the conductive network of the carbon material and the pore structure of the molecular sieve synergistically construct an "electron transfer-mass diffusion" pathway, achieving functional complementarity between conductivity efficiency and catalytic selectivity.

[0118] The present invention does not specifically limit the application scenarios of the above-mentioned conductive heterojunction catalyst. Due to its advantages, in some embodiments, the conductive heterojunction catalyst of the present invention can be used for catalytic cracking reactions, isomerization reactions, aromatization reactions, and hydrocracking reactions with molecular sieves as the active phase.

[0119] For example, a conductive heterojunction catalyst prepared from ZSM-5 molecular sieve and chitosan was used for catalytic cracking reactions. First, the charged functional groups on the modified ZSM-5 surface and the carbon material formed by chitosan carbonization form a continuous and strong interaction. The carbon material is not only firmly loaded on the molecular sieve surface but also partially permeates into the pores, constructing a continuous conductive network that can rapidly transfer electrons. When the reaction system is energized, electrons are directly transferred along the carbon material to the aluminum active sites of the ZSM-5 framework, significantly increasing the electron density of the active sites and accelerating the polarization and breaking of C-C bonds in naphtha molecules, thereby increasing the yield of low-carbon olefins and demonstrating excellent catalytic activity. Second, the continuous coating layer of the carbon material reduces the direct adhesion of carbon deposits to the active sites, and the strong interaction inhibits the separation of the carbon material from the molecular sieve, resulting in structural stability significantly better than traditional catalysts. Furthermore, the carbon material does not clog the molecular sieve pores, allowing the feedstock to diffuse efficiently to the active sites and the product to desorb rapidly, avoiding secondary reactions and ensuring high selectivity for low-carbon olefins.

[0120] For example, a conductive heterojunction catalyst prepared from MOR molecular sieves and chitosan is used to catalyze the isomerization of n-pentane to isopentane. On one hand, the charged functional groups on the surface of the modified MOR molecular sieve form a tight heterojunction with the chitosan-based carbon material. The conductive network constructed by the carbon material enables uniform and rapid electron transfer. When the reaction is energized, electrons rapidly migrate through the nitrogen-doped carbon material to the strongly acidic sites on the surface of the MOR molecular sieve, increasing the electron density at these sites and making it easier to polarize the CH bonds in the n-pentane molecule, promoting its protonation to form a carbocation intermediate. Simultaneously, electrons are transferred through the carbon material to the reaction interface, regulating the activity of hydrogen species and inhibiting excessive dehydrogenation of carbocations to form carbon precursors. The synergistic effect of the thermal conductivity and electrical conductivity of the carbon material ensures a uniform temperature distribution in the reaction system, further reducing cracking side reactions caused by local overheating and guaranteeing the efficient isomerization reaction.

[0121] For example, a conductive heterojunction catalyst prepared from ZSM-5 molecular sieve and chitosan was used for propane aromatization. First, the charged functional groups on the modified ZSM-5 surface interact strongly with the chitosan carbonized material. The carbon material not only forms a continuous conductive layer on the molecular sieve surface but also partially enters the pores. The constructed conductive network efficiently transfers electrons to the acidic sites of the modified ZSM-5, improving the accessibility of electrons to these sites, accelerating the cyclization and dehydrogenation processes of low-carbon olefins, increasing conversion rate, and significantly enhancing catalytic activity. Second, the presence of the carbon material acts as a "carbon deposition accommodating site," reducing carbon buildup within the pores of the modified ZSM-5 and extending catalyst lifetime. Simultaneously, the strong bond between the carbon material and the molecular sieve forms a heterojunction structure, preventing catalyst particle detachment and ensuring relatively stable activity during recycling, demonstrating a clear advantage in structural stability.

[0122] For example, a conductive heterojunction catalyst of Y-type molecular sieve and chitosan can be used for the hydrocracking of n-dodecane, achieving highly efficient synergistic catalysis. When the reaction system is energized, electrons are transferred to the hydrogenation active sites via the carbon material, promoting the dissociation of H2 into highly active hydrogen species. Simultaneously, electrons migrate through the carbon-molecular sieve interface to the moderately acidic sites of the Y-type catalyst, adjusting the acidity. This allows n-dodecane to first crack into C5-C8 olefin intermediates at the acidic sites, and then be rapidly saturated into alkanes by adjacent active hydrogen species. The accelerated electron transfer between the active sites and molecular sieves reduces the residence time of olefin intermediates within the pores, thereby improving catalytic efficiency.

[0123] Thirdly, the present invention provides a catalytic reaction apparatus 1, which includes a power source 10, an insulated reactor 21, and a catalytic bed 22, wherein the catalytic bed 22 is placed inside the insulated reactor 21; the catalytic bed 22 includes a conductive heterojunction catalyst as described in the first aspect.

[0124] In a preferred embodiment, such as Figure 1 As shown, the catalytic reaction device 1 includes a power supply 10 and a reaction vessel 20. The power supply 10 includes a positive electrode and a negative electrode, which are connected to the reaction vessel 20 to supply power to the reaction vessel 20.

[0125] The reaction vessel 20 includes an insulated reactor 21, a catalyst bed 22, electrode plates 23, and an inlet / outlet A. The inlet / outlet A is located on the reaction vessel 20 and connects to the inner cavity of the insulated reactor 21, allowing the reactants to enter the inner cavity of the insulated reactor 21. In this invention, a conductive heterojunction catalyst is disposed within the inner cavity of the insulated reactor 21, allowing it to contact the reactants, and a catalyst bed 22 is formed at the location of the conductive heterojunction catalyst. The catalyst bed 22 is connected to the electrode plates 23.

[0126] The insulating reactor 21 is made of an insulating material, which may be, for example, quartz.

[0127] The conductive heterojunction catalyst on the catalyst bed 22 is connected to the power source 10 through the electrode plate 23. Specifically, the conductive heterojunction catalyst prepared in this invention is filled into the inner cavity of the insulating reactor 21, and the positive and negative electrodes of the power source 10 are connected to the electrode plate 23 respectively. The electrode plate 23 is connected to the conductive heterojunction catalyst. A complete conductive circuit of "power source-electrode plate-conductive heterojunction catalyst" is constructed through direct contact or indirect contact through a conductive medium to ensure that the current can be stably transmitted to the conductive heterojunction catalyst of this invention after power is applied.

[0128] In some embodiments, the catalytic reaction apparatus 1 includes a feed tank, a feed pump, a preheating furnace, a heat preservation device, a catalytic bed 22, a quartz reaction tube, electrodes 23, and a DC power supply. By filling the quartz reaction tube with a conductive heterojunction catalyst and applying a DC voltage between the two electrodes, the Joule heating effect can be used to rapidly heat the catalytic bed, providing the necessary thermal energy for the reaction and satisfying the electrothermal conversion required for driving the catalytic reaction with electrical power. On the other hand, it participates in the electron transfer process as an electrocatalytic active carrier, assisting the target catalytic reaction to proceed efficiently.

[0129] For example, in a catalytic cracking reaction, the device generates a local electric field at the heterojunction interface through the action of an electric field, optimizes the electronic state distribution of the active sites of the molecular sieve, reduces the activation energy of the reaction, and thus significantly improves the catalytic performance.

[0130] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. 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 scope of protection of the present invention.

[0131] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0132] Example 1

[0133] (1) Weigh out polydiallyldimethylammonium chloride and sodium poly(p-styrene sulfonate) and dissolve them in 100 mL of deionized water to make their mass fractions 10 wt.%; then add 1 g of ZSM-5 molecular sieve to the above aqueous solution and stir for 4 h. After centrifugation to separate the solid and drying, the modified molecular sieve can be obtained.

[0134] (2) Measure 80 mL of liquid paraffin and 4 mL of Tween 20 and place them in a beaker. Sonicate for 1 h to mix them evenly. Then add 0.2 g of modified molecular sieve and sonicate for 20 min to obtain a suspension in which the molecular sieve is evenly dispersed.

[0135] (3) Weigh 1 g of chitosan and add it to 30 mL of acetic acid solution with a mass fraction of 2.5 wt.%. Sonicate for 30 min to form a uniform and transparent gel. Add it dropwise to the suspension obtained in step (2) and stir for 2 h (the mass ratio of chitosan to modified molecular sieve is 1:0.2). Then add 4 mL of glutaraldehyde and stir at room temperature for 2 h. Finally, add 1.0 mol / L NaOH solution to the above solution, adjust the pH value to 9, react at room temperature for 12 h, and wash the obtained product thoroughly with acetone, petroleum ether and deionized water in sequence. Filter and dry under vacuum at 60 °C to obtain the cross-linked chitosan catalyst coated with molecular sieve, i.e., the composite material.

[0136] (4) The composite material obtained in step (3) is calcined at high temperature. Under a nitrogen atmosphere, the heating program is set to increase the calcination temperature to 700 ℃ at a rate of 1 ℃ / min. The calcination is carried out at this temperature for 4 h, and then cooled to room temperature to obtain the conductive heterojunction catalyst.

[0137] Example 2

[0138] The process is basically the same as in Example 1, except that in step (1), polydiallyldimethylammonium chloride and sodium poly(p-styrene sulfonate) are weighed and dissolved in 100 mL of deionized water to make their mass fractions 5 wt.%.

[0139] Example 3

[0140] The process is basically the same as in Example 1, except that in step (1), polydiallyldimethylammonium chloride and sodium poly(p-styrene sulfonate) are weighed and dissolved in 100 mL of deionized water, so that their mass fraction is 1 wt.%.

[0141] Example 4

[0142] It is basically the same as Example 1, except that the mass of the modified molecular sieve added in step (2) is 2 g, so that the mass ratio of chitosan to modified molecular sieve is 1:2.

[0143] Example 5

[0144] It is basically the same as Example 1, except that the molecular sieve used in step (1) is SAPO-34.

[0145] Experimental Example 1

[0146] The conductive heterojunction catalyst obtained in Example 1 was placed in, as... Figure 1In the catalytic reaction apparatus shown, the catalytic bed is heated to 450 °C using electrical power. Then, 1-hexene is fed a mixed feed of H₂O to perform a catalytic cracking reaction of 1-hexene to produce low-carbon olefins, as shown in Table 2. Infrared thermal imaging of the catalytic reaction apparatus in progress is shown in [Table 2]. Figure 2 Infrared thermal imaging of the catalytic reaction apparatus shown. Figure 2 As shown, the conductive heterojunction catalyst provided in Example 1, when applied to the electrically powered heating reaction device described above, can make the catalytic cracking reaction heat evenly and improve the catalytic performance.

[0147] Experimental Example 2

[0148] The results were basically the same as in Experiment 1, except that the catalyst bed was heated to 500 °C using an electric power source, as shown in Table 2.

[0149] Experimental Example 3

[0150] It is basically the same as Experiment 1, except that the catalyst bed is heated to 550 °C by electric power supply, as shown in Table 2.

[0151] Test Example 4

[0152] It is basically the same as Experiment 1, except that the catalyst bed is heated to 600 °C by electric power supply, as shown in Table 2.

[0153] Experimental Example 5

[0154] It is basically the same as Experimental Example 2, except that the catalyst bed is heated to 500 °C by external heating, as shown in Table 2.

[0155] Experimental Example 6

[0156] It is basically the same as Experimental Example 3, except that the catalyst bed is heated to 550 °C by external heating, as shown in Table 2.

[0157] Experimental Example 7

[0158] It is basically the same as Experiment 4, except that the catalyst bed is heated to 600 °C by external heating, as shown in Table 2.

[0159] Experimental Example 8

[0160] It is basically the same as Experimental Example 3, except that the conductive heterojunction catalyst obtained in Example 5 is used, as shown in Table 2.

[0161] Comparative Example 1

[0162] (1) Weigh a certain amount of polydiallyldimethylammonium chloride and sodium poly(p-styrene sulfonate) and dissolve them in 100 mL of deionized water. Their mass fractions are 10 wt.% respectively. Then add 1 g of ZSM-5 molecular sieve to the above aqueous solution and stir for 4 h. Then centrifuge to separate the solid and dry overnight to obtain the modified molecular sieve.

[0163] (2) Measure 80 mL of liquid paraffin and 4 mL of Tween 20 and place them in a beaker. Sonicate for 1 h to mix them evenly. Then weigh 1 g of chitosan and add it to 30 mL of acetic acid solution with a mass fraction of 2.5 wt.%. Sonicate for 30 min to form a uniform and transparent gel. Then add 4 mL of glutaraldehyde and stir at room temperature for 2 h. Finally, add 1.0 mol / L NaOH solution dropwise to the above solution to adjust the pH value to about 9. React at room temperature for 12 h. The obtained product is washed thoroughly with acetone, petroleum ether and deionized water in sequence and filtered. It is then dried under vacuum at 60 °C to obtain cross-linked chitosan.

[0164] (3) The modified ZSM-5 molecular sieve and the obtained cross-linked chitosan were combined by mechanical mixing at a mass ratio of 0.2:1.

[0165] (4) The solid obtained in step (3) is calcined at high temperature. Under a nitrogen atmosphere, the calcination temperature is increased to 700 ℃ at a rate of 1 ℃ / min. The solid is calcined at this temperature for 4 h and then cooled to room temperature to obtain a mechanically mixed molecular sieve catalyst. That is, the mechanically mixed molecular sieve catalyst obtained has no heterojunction structure.

[0166] The obtained molecular sieve catalyst was placed in, for example Figure 1 In the catalytic reaction apparatus shown, the catalytic bed is heated to 550 °C by electric power supply. Then, 1-hexene and H2O are mixed and fed to carry out the catalytic cracking reaction of 1-hexene to produce low-carbon olefins, as shown in Table 2.

[0167] Comparative Example 2

[0168] It is basically the same as Comparative Example 1, except that the obtained molecular sieve catalyst is placed in a... Figure 1 In the catalytic reaction apparatus shown, the catalytic bed is heated to 550 °C by external heating, and then 1-hexene and H2O are mixed and fed to carry out the catalytic cracking reaction of 1-hexene to produce low carbon olefins, as shown in Table 2.

[0169] Comparative Example 3

[0170] (1) Measure 80 mL of liquid paraffin and 4 mL of Tween 20 into a beaker, sonicate for 1 h to mix them evenly, then add 0.2 g of ZSM-5 molecular sieve and sonicate for 20 min to obtain a suspension in which the molecular sieve is evenly dispersed.

[0171] (2) Weigh 1 g of chitosan and add it to 30 mL of acetic acid solution with a mass fraction of 2.5 wt.%. Sonicate for 30 min to form a uniform and transparent gel. Add it dropwise to the suspension obtained in step (1) and stir for 2 h. Then add 4 mL of glutaraldehyde and stir at room temperature for 2 h. Finally, add 1.0 mol / L NaOH solution to the above solution, adjust the pH value to 9, react at room temperature for 12 h, and wash the obtained product thoroughly with acetone, petroleum ether and deionized water in sequence. Filter and dry under vacuum at 60 °C to obtain cross-linked chitosan catalyst coated with molecular sieve.

[0172] (3) The composite material obtained in step (2) is subjected to high-temperature calcination. Under a nitrogen atmosphere, the calcination temperature is increased to 700 ℃ at a rate of 1 ℃ / min. The material is calcined at this temperature for 4 h and then cooled to room temperature to obtain the molecular sieve catalyst.

[0173] The obtained molecular sieve catalyst was placed in, for example Figure 1 In the catalytic reaction apparatus shown, the catalytic bed is heated to 550 °C by electric power supply. Then, 1-hexene and H2O are mixed and fed to carry out the catalytic cracking reaction of 1-hexene to produce low-carbon olefins, as shown in Table 2.

[0174] Comparative Example 4

[0175] ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25 was pressed into tablets and sieved to obtain molecular sieve particles of 40-60 mesh. These particles were not combined with a conductive substrate. The obtained molecular sieve catalyst was placed in the catalytic reaction device provided by this invention. The catalytic bed was heated to 450 °C by external heating. Then, 1-hexene and H2O were mixed and fed to carry out the catalytic cracking reaction of 1-hexene to produce low-carbon olefins, as shown in Table 2.

[0176] Comparative Example 5

[0177] It is basically the same as Comparative Example 4, except that the catalyst bed is heated to 500 °C by external heating, as shown in Table 2.

[0178] Comparative Example 6

[0179] It is basically the same as Comparative Example 4, except that the catalyst bed is heated to 550 °C by external heating, as shown in Table 2.

[0180] Comparative Example 7

[0181] It is basically the same as Comparative Example 4, except that the catalyst bed is heated to 600 °C by external heating, as shown in Table 2.

[0182] Test Example 1

[0183] The conductivity of the catalysts provided in Examples 1-3 and Comparative Examples 1-7 was tested, and the results are shown in Table 1. It can be seen that the conductive heterojunction catalysts provided in Examples 1-3 have higher conductivity, and therefore better electrothermal conversion efficiency. Therefore, the conductive heterojunction catalyst of the present invention can convert the applied electrical energy into Joule heat, realizing a catalytic reaction system that relies solely on electrical heating, while possessing both high conductivity and catalytic performance.

[0184] Table 1:

[0185]

[0186] Test Example 2

[0187] The catalytic cracking performance of the catalysts provided in Examples 1, 5 and Comparative Examples 1-7 was tested, and the test results are shown in Table 2.

[0188] Table 2:

[0189]

[0190] As shown in Table 2, under the same heating conditions, the catalytic reaction using the conductive heterojunction catalyst provided in this application exhibits a higher conversion rate and yield. Therefore, compared to the comparative example, the conductive heterojunction catalyst of this invention demonstrates superior catalytic activity.

[0191] Furthermore, the results of Examples 2-7 show that, at the same heating temperature, the conversion rate and yield of the electrothermal conversion power supply method (electric heating) are higher than those of the conventional external heating method when using the conductive heterojunction catalyst prepared in Example 1. This indicates that the conductive heterojunction catalyst of the present invention can be used not only for catalytic reactions with conventional external heating, but also for catalytic reactions powered by electrothermal conversion, and exhibits superior catalytic activity in the electric power supply scenario.

[0192] Test Example 3

[0193] X-ray diffraction analysis was performed on the conductive heterojunction catalyst obtained in Example 1 above, as well as the commercially available ZSM-5 molecular sieve catalyst. Specific test results can be found in [link to relevant documentation]. Figure 3 .

[0194] like Figure 3As shown in the figure, ZSM-5 / C is the conductive heterojunction catalyst obtained in Example 1, and ZSM- is commercially available ZSM-5. The diffraction peaks of both are basically consistent, exhibiting typical diffraction peaks of ZSM-5. Therefore, the conductive heterojunction catalyst obtained using the preparation method provided by this invention retains the original catalytic activity of the molecular sieve components.

[0195] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a conductive heterojunction catalyst, characterized in that, Includes the following steps: Molecular sieves are added to a mixture of cationic polymers and anionic polyelectrolytes containing sulfonic acid groups, and the mixture is then treated to obtain modified molecular sieves. Chitosan is cross-linked with the modified molecular sieve to obtain a composite material, which is then sintered in a protective atmosphere to obtain the conductive heterojunction catalyst.

2. The method for preparing the conductive heterojunction catalyst according to claim 1, characterized in that, The cationic polymer comprises at least one of the following: polydiallyldimethylammonium chloride, polydimethylaminoethyl methacrylate, poly(acrylamide-co-dimethylaminopropylacrylamide), and polyethyleneimine; Preferably, based on the mass of the mixture, the cationic polymer has a mass fraction of 1 to 10 wt.%.

3. The method for preparing the conductive heterojunction catalyst according to claim 1 or 2, characterized in that, The sulfonic acid-containing anionic polyelectrolyte comprises at least one of: sodium terephthalate sulfonate, poly(2-acrylamide-2-methylpropanesulfonic acid), and sulfonated styrene-maleic anhydride copolymer. Preferably, based on the mass of the mixture, the mass fraction of the sulfonic acid-containing anionic polyelectrolyte is 1~10 wt.%.

4. The method for preparing the conductive heterojunction catalyst according to any one of claims 1-3, characterized in that, The sintering process includes: heating to 450-800 ℃ at a heating rate of 1-10 ℃ / min under the protective atmosphere, and holding at that temperature for 3-5 h; Preferably, the protective atmosphere includes at least one of N2, H2, Ar, and He.

5. The method for preparing the conductive heterojunction catalyst according to any one of claims 1-4, characterized in that, The crosslinking treatment includes the following steps: The first mixture includes the modified molecular sieve and the solvent; The chitosan and acid solution are mixed to obtain a second mixture, and the pH value of the second mixture is adjusted to 2.26~2.76; Mix the first mixture, the second mixture, and the crosslinking agent, and adjust the pH of the mixture to 8-10; Preferably, the solvent comprises a dispersant and a surfactant, wherein the volume ratio of the dispersant to the surfactant is (10~50):1; Preferably, the acid solution has a mass fraction of 1~10 wt.%; Preferably, the second mixture is added dropwise to the first mixture.

6. The method for preparing the conductive heterojunction catalyst according to claim 5, characterized in that, The dispersant comprises at least one of the following: dimethyl silicone oil, cyclomethyl silicone oil, polybutene, liquid paraffin, and fatty acid ester; The surfactant comprises at least one of lauryl glucoside, Tween 20, Tween 40, Tween 60, Span 20, Span 40, Span 60, and F127. The crosslinking agent comprises at least one of glyoxal, acrolein, glutaraldehyde, ethylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether.

7. The method for preparing the conductive heterojunction catalyst according to any one of claims 1-6, characterized in that, The mass ratio of chitosan to the modified molecular sieve is 1:(0.2~2).

8. The method for preparing the conductive heterojunction catalyst according to any one of claims 1-7, characterized in that, The molecular sieve includes at least one of ZSM molecular sieve, Beta molecular sieve, SAPO molecular sieve, MOR molecular sieve, and Y-type molecular sieve.

9. A conductive heterojunction catalyst obtained by the preparation method of the conductive heterojunction catalyst according to any one of claims 1-8.

10. A catalytic reaction apparatus, characterized in that, The catalytic reaction apparatus includes a power source, an insulated reactor, and a catalytic bed, wherein the catalytic bed is placed inside the insulated reactor; the catalytic bed contains the conductive heterojunction catalyst as described in claim 9.

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