Carbon-containing material directional conversion method based on molten salt thermoelectric synergy

Abstract

The invention discloses a carbon-containing material directional conversion method based on molten salt thermoelectric synergy, and belongs to the field of energy chemical industry and high-value utilization of resources. According to the method, a carbon-containing material and derivative small molecules thereof are used as substrates. The core of the method is as follows: at 150-300 DEG C, in a specific molten salt medium, an electric field response type interface confinement catalyst is used as a working electrode, and a cathode potential of-0.5 V to-1.2 V is applied. Through a coupling mechanism of molten salt thermoelectric synergy and electric field induced hydrogen overflow, directional migration and fixed-point hydrogenation of hydrogen species from catalyst active sites to carbon-containing material target functional groups are precisely regulated and controlled. The method effectively solves the problems of high energy consumption, poor selectivity, low electro-catalysis efficiency and the like of traditional thermocatalysis, is suitable for efficient and high-selectivity conversion of various carbon-containing materials and derivative small molecules thereof, and has the outstanding advantages of accurate reaction path, high energy efficiency, good catalyst stability, high process universality and the like.

Description

Technical Field

[0001] This invention belongs to the field of energy chemical engineering and high-value utilization of resources, specifically relating to a method for the directional conversion of carbon-containing materials. More specifically, this invention relates to a method for the directional hydrogenation conversion of carbon-containing materials within a temperature range of 150–300°C, based on the synergistic effect of molten salt thermoelectricity and the electric field-induced hydrogen overflow mechanism. Background Technology

[0002] Achieving efficient and selective conversion of carbon-containing materials (such as biomass, waste plastics, and coal) is key to promoting the recycling of carbon resources. Carbon-containing small molecules derived from these materials, such as platform molecules from biomass (e.g., furfural, 5-hydroxymethylfurfural), small molecules from plastic pyrolysis (e.g., styrene, propylene), and coal platform molecules (e.g., toluene or phenol), face common technical challenges in their directional conversion (e.g., selective hydrogenation), including complex reaction pathways, poor selectivity of target products, harsh reaction conditions (high temperature and high pressure), high energy consumption, and easy catalyst deactivation.

[0003] Currently, the directed conversion of carbon-containing materials and their derived small molecules mainly relies on traditional thermocatalysis and electrocatalysis technologies. Traditional thermocatalysis generally requires noble metal catalysts such as Pt and Pd, and the reaction must be carried out at high temperatures and high pressures exceeding 300°C. This approach not only leads to high catalyst costs and energy consumption but also easily triggers side reactions such as excessive cracking of reactants and carbon deposition, resulting in catalyst deactivation, significantly reducing the selectivity of the target product, and limiting the efficiency and economy of the conversion process. While electrocatalysis can utilize renewable energy-driven electricity for reactions under relatively mild conditions, it generally suffers from low current efficiency, severe mass transfer limitations, and poor electrode stability, making large-scale application difficult.

[0004] Existing technologies have attempted to utilize molten salt media for reactions, but all have significant limitations. For example, patent CN202511237855.0 primarily uses molten salt as a high-temperature heat carrier for pyrolysis reactions, without addressing the introduction and synergistic effects of an electric field, thus failing to solve the selectivity problem of directional conversion of carbon-containing materials. Although patent CN202510828227.3 uses molten salt as an electrolyte for electrochemical synthesis, its technical system fails to solve core scientific problems and technical bottlenecks such as the directional transport of hydrogen species (H*) from active sites to reaction sites and the compatibility of catalyst microstructure with the molten salt ionic environment, resulting in unsatisfactory efficiency and selectivity.

[0005] Therefore, there is an urgent need in this field to develop a general conversion method that can precisely control the reaction pathway of carbon-containing materials in the medium and low temperature range (e.g., 150–300 °C), is compatible with a variety of catalysts and carbon-containing substrates, and has industrialization potential, in order to solve the problems of high energy consumption, poor selectivity, easy catalyst deactivation, and imprecise reaction pathway control in the existing technology. Summary of the Invention

[0006] I. Purpose of the Invention

[0007] The purpose of this invention is to provide a method for the directional conversion of carbon-containing materials based on molten salt thermoelectric synergy. This method uses carbon-containing materials and their derived small molecules as substrates and aims to solve the problems of high energy consumption, poor selectivity, easy catalyst deactivation, and imprecise reaction pathway control in existing technologies. It achieves efficient, directional, and scalable conversion of carbon-containing materials and their derived small molecules in a low-temperature range of 150–300℃.

[0008] II. Technical Solution

[0009] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0010] (I) Core Methodology:

[0011] In a molten salt medium of a specific composition, a catalyst is used as the working electrode. By precisely controlling the reaction temperature and the applied cathode potential, the resulting thermoelectric synergistic effect and the electric field-induced hydrogen spillover mechanism are utilized to achieve the directional conversion of carbon-containing materials and their derived small molecules. The method comprises the following three key elements:

[0012] (1) Reaction medium and environment: including molten salt medium (nitrate, carbonate, chloride or their mixture), hydrogen source (water, alcohol, acid) and substrate. Molten salt serves as a conductive medium, ion regulation carrier and hydrogen species (H*) stabilizer.

[0013] (2) Catalyst and hydrogen source: An electric field-responsive interface confined catalyst is used as the active reaction center, and a hydrogen source is continuously introduced to provide active H*.

[0014] (3) External field coupling: Applying a precisely controlled cathode potential, in conjunction with the temperature field, drives and guides the reaction.

[0015] (II) Method and Flow:

[0016] A method for the directional conversion of carbon-containing materials based on molten salt thermoelectric synergy, using carbon-containing materials and their derived small molecules as substrates for directional conversion, includes the following steps:

[0017] S1: System Construction and Activation of Molten Salt

[0018] Molten salt is placed in a corrosion-resistant reaction vessel. The molten salt is a nitrate, chloride, or a mixture thereof, wherein the nitrate can be selected from the LiNO3-NaNO3-KNO3 eutectic system, and the chloride can be selected from the ZnCl2-KCl eutectic system. Under the protection of an inert gas (such as N2), the molten salt is heated to 150–300°C to form a uniform ionic molten pool. A catalyst electrode, which is a catalyst electrode formed by loading a catalyst onto a working electrode, is then placed in the molten salt. The catalyst is an electric field-responsive interface-confined catalyst, specifically selected from mesoporous metal oxide supported catalysts, two-dimensional layered composite catalysts, or core-shell encapsulated catalysts. At least one of the following catalysts is used, wherein the support for the mesoporous metal oxide supported catalyst is TiO2, Al2O3, ZrO2, SiO2 or CeO2, and the supported metal is one or more of Ni, Co, Fe and Cu; simultaneously, a hydrogen source is continuously introduced at a rate of 0.01 to 0.05 wt.% / min, wherein the hydrogen source is at least one of water, alcohol or acid; a cathode potential of -0.5V to -1.2V (relative to the reference electrode in the molten salt) is applied to the catalyst electrode for pre-activation for 1 to 60 minutes to form a stable "catalyst-molten salt ion-active hydrogen" interface.

[0019] S2: Substrate introduction and adsorption

[0020] The substrate is continuously injected into the reaction system described in step S1 at a rate of 0.1–0.5 wt.% / min. The substrate can be at least one of carbon-containing materials (such as biomass, waste plastics, coal, etc.); it can also be a carbon-containing material-derived small molecule, selected from at least one of biomass platform molecules (such as furfural, 5-hydroxymethylfurfural), plastic pyrolysis small molecules (such as styrene, propylene), and coal platform molecules (such as toluene or phenol). The mass ratio of substrate to molten salt is controlled to be 1:5 to 1:50. Under the high temperature and ionic environment of the molten salt, the substrate fully swells and diffuses and adsorbs onto the catalyst surface.

[0021] S3: Thermoelectric Synergistic Reaction and Directed Conversion

[0022] Maintaining the reaction temperature between 150 and 300°C provides the basic activation energy for the substrate, effectively weakening the bond energy of its target functional groups (such as C=O and C=C), thus activating them. The cathode (catalyst electrode) potential drives the hydrogen source to undergo electrochemical reduction at the active sites of the catalyst, continuously generating adsorbed hydrogen species (H*). Under the directional induction of the applied electric field, the hydrogen species (H*) "escape" along the catalyst surface or bulk structure, precisely migrating to the adjacent, thermally activated target functional groups of the substrate, undergoing selective hydrogenation and achieving directional conversion. The magnitude of the cathode potential directly controls the rate and direction of hydrogen overflow.

[0023] S4: Product Separation and Material Circulation

[0024] After the reaction is completed, the gaseous products are carried out of the system by the carrier gas, and the condensable products are condensed and recovered by the condenser, while the non-condensable products are collected in the gas bag. After the reaction vessel is cooled to room temperature, the liquid products are separated by cooling, dissolving, filtering and centrifugation. The catalyst is taken directly from the molten salt and recycled after roasting or cleaning. The molten salt is cooled, dissolved and recrystallized, or directly melted and replenished with new components to achieve recycling.

[0025] Furthermore, the molten salt system can be replaced with a eutectic solvent, an ionic liquid (for low temperatures, such as <150°C), or a high-temperature carbonate system (for high temperatures, such as >300°C) for compounding to adapt to substrates with different thermal stability, such as heat-sensitive carbon-containing materials or high-stability polyethylene carbon-containing materials.

[0026] Furthermore, the mesoporous support of the catalyst can be replaced with a hierarchical pore material; the active component of the catalyst is not limited to metal, but can also be replaced with metal sulfides, phosphides, carbides or non-metal-doped carbon-based catalysts (such as nitrogen-doped carbon) with metal-like catalytic properties, to adapt to the conversion requirements of different types of substrates.

[0027] Furthermore, in addition to liquid hydrogen sources, ammonia or low-carbon hydrocarbon gases (such as methane) can also be used as hydrogen sources. By controlling the cathode potential, the hydrogen source can be controlled to undergo cracking on the catalyst surface, thereby achieving in-situ hydrogen supply and meeting the hydrogen source requirements for the directional transformation of carbon-containing material molecules.

[0028] III. Beneficial Effects

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The reaction selectivity is significantly improved:

[0031] The coupling mechanism of "molten salt thermoelectric synergy and electric field-induced hydrogen overflow" in this invention uses carbon-containing materials and their derived small molecules as substrates for directional transformation. Utilizing the high ionic conductivity and ability of molten salt to stabilize hydrogen species, the generation, migration, and overflow path of hydrogen species (H*) on the catalyst surface are precisely controlled by applying an external electric field within the temperature range of 150–300°C. This achieves targeted and preferential hydrogenation of target functional groups (such as C=O and C=C) of the substrate, fundamentally suppressing side reactions. For a typical reaction, such as the hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan, the selectivity of the target product can be stably higher than 85% within the temperature range of 150–300°C, far exceeding traditional thermocatalytic methods (typically <70%).

[0032] (2) Significantly improved energy efficiency:

[0033] This invention fully utilizes the excellent thermal conductivity of molten salt and combines it with the driving effect of an electric field under mild conditions to significantly reduce the dependence of the conversion of carbon-containing materials and their derived small molecules on the overall reaction temperature. The reaction can be carried out efficiently in the medium-low temperature range of 150–300℃. Preliminary estimates suggest that, to achieve the same conversion rate, the total energy consumption of the system can be reduced by more than 40% compared to traditional pure thermal catalysis methods.

[0034] (3) Enhanced catalyst stability:

[0035] By designing electric field-responsive interface-confined catalyst microstructures (such as mesoporous, two-dimensional layered, core-shell, etc.) that match the molten salt ion environment and electric field, the hydrogen overflow efficiency is significantly improved. At the same time, the specific catalyst configuration and mild electrochemical environment help to alleviate metal sintering and carbon deposition problems, which can significantly extend the service life of the catalyst and meet the needs of long-term stable conversion of carbon-containing materials.

[0036] (4) Advantages of versatility and platformization:

[0037] The method of this invention is universally applicable to a variety of carbon-containing materials (such as biomass, waste plastics, coal, etc.) and their derivative small molecules (such as biomass platform molecules, plastic pyrolysis small molecules, coal platform molecules) and hydrogen sources. Different substrates can be processed using a single process unit with adjustments to key parameters, breaking the traditional limitation of "one reaction, one catalyst." Simultaneously, the molten salt medium functions as a heat carrier, ion conductor, and reaction promoter, simplifying the reaction system and subsequent separation process, and possessing strong potential for industrial scale-up.

[0038] (5) Application scenarios can be expanded:

[0039] The "molten salt thermoelectric synergy and electric field-induced hydrogen overflow" mechanism disclosed in this invention can be extended to other fields of precise small molecule conversion, such as the preparation of high-value-added chemicals by carbon dioxide hydrogenation and the synthesis of ammonia by nitrogen electrochemical reduction, further expanding the application scope of the technology. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the reaction apparatus of the present invention.

[0041] Figure 2 Typical structural diagrams of electric field-responsive interface-confined catalysts: (a) two-dimensional layered catalyst; (b) core-shell encapsulated catalyst; (c) mesoporous metal oxide supported catalyst.

[0042] Figure reference numerals: 1-molten salt; 2-Hastelloy C276 reaction vessel; 3-reactor inlet; 4-high-purity N2; 5-electromagnetic heating stirrer; 6-rotor; 7-catalyst electrode; 8-reference electrode; 9-power supply; 10-hydrogen source injection pump; 11-heating jacket; 12-feed pipe; 13-substrate injection pump; 14-reactor outlet; 15-filtration device; 16-condensation device; 17-gas bag; 18-reactor flange Detailed Implementation

[0043] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The described embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0044] Example 1: Directed hydrogenation conversion of biomass platform molecule (5-hydroxymethylfurfural)

[0045] (I) Experimental Setup

[0046] As shown in the attached document Figure 1 The reaction apparatus shown includes a Hastelloy C276 reaction vessel (2), a reactor inlet (3), an electromagnetic heating stirrer (5), a rotor (6), a catalyst electrode (7), a reference electrode (8), a power supply (9), a hydrogen injection pump (10), a heating jacket (11), a feed pipe (12), a substrate injection pump (13), a reactor outlet (14), a filter (15), a condenser (16), a gas bag (17), and a reactor flange (18), etc. The connection relationships of each component are shown in the attached figure. Figure 1 As shown. The catalyst electrode (7) uses the method shown in the attached figure. Figure 2 (c) shows a mesoporous metal oxide supported catalyst with TiO2 as the support and Ni-Co bimetal as the supported metal (the mass ratio of Ni to Co is 1:1).

[0047] (II) Experimental Procedure

[0048] (1) System construction and activation:

[0049] 500g of LiNO3-NaNO3-KNO3 eutectic molten salt (mass ratio 30:40:30) was placed in a Hastelloy C276 reaction vessel (2). High-purity N2 (4) was introduced through the reactor inlet (3) to purge the air from the vessel. The electromagnetic heating stirrer (5) was started to heat the molten salt to 220°C, forming a uniform ionic molten pool under the disturbance of the rotor (6). The prepared Ni-Co / TiO2 mesoporous catalyst was coated on the surface of a conductive substrate to form a catalyst electrode (7), which was placed in the molten salt along with the reference electrode (8) and connected to the negative and positive terminals of the power supply (9), respectively. Deionized water was continuously injected as a hydrogen source at a rate of 0.03 wt.% / min via an injection pump (10). The hydrogen source was heated by a heating jacket (11) and then entered the reaction system through a feed pipe (12). A cathode potential of -0.8V (relative to the Ag / AgCl reference electrode in the molten salt) was applied to the catalyst electrode. Pre-activation was carried out for 60 minutes. During this process, the hydrogen source flowed to the catalyst electrode and an electrochemical reduction reaction occurred at the active site of the catalyst electrode, continuously generating hydrogen species (H*), and finally forming a stable “catalyst-molten salt ions-active hydrogen” interface.

[0050] (2) Substrate introduction and adsorption:

[0051] After the reaction had proceeded for 60 minutes, 5-hydroxymethylfurfural (HMF), a small molecule derived from carbon-containing materials, was used as the substrate. A methanol solution of HMF (HMF concentration: 10 wt.%) was continuously injected into the reaction system at a rate of 0.3 wt.% / min using a syringe pump (13), controlling the mass ratio of HMF to molten salt to be 1:10. Under the high temperature and ionic environment of the molten salt at 220°C, the HMF molecules fully swelled and diffused, adsorbing onto the surface of the catalyst electrode.

[0052] (3) Thermoelectric synergistic reaction and directional conversion: The reaction continues for 120 minutes, maintaining a reaction temperature of 220℃ and a cathode potential of -0.8V. This temperature provides the basic activation energy for HMF molecules, weakening their C=O bond energy and putting them in an activated state. Under the thermoelectric synergistic effect, the -0.8V cathode potential drives the hydrogen source (water) to undergo electrochemical reduction at the active site of the catalyst electrode, continuously generating adsorbed hydrogen species (H*). Under the directional induction of the applied electric field, H* overflows along the catalyst mesoporous channels and surface, precisely migrating to the thermally activated C=O functional groups of HMF molecules, undergoing a selective hydrogenation reaction to generate 2,5-bis(hydroxymethyl)furan (BHMF), inhibiting the hydrogenation of C=C bonds on the furan ring and the ring-opening side reaction.

[0053] (4) Product separation and material recycling

[0054] After the reaction lasted for 4 hours, the feed and power supply were stopped. The gaseous product was carried out through the reactor outlet (14) by the carrier gas, and after impurities were removed by the filter (15), the condensable product was condensed and recovered in the condenser (16), while the non-condensable product was collected in the gas bag (17). After the reaction vessel cooled to room temperature, the reactor flange (18) was opened, and the reaction mixture was taken out. The liquid product BHMF was obtained by dissolving, filtering, and centrifuging. The catalyst electrode was taken out, and after calcination to remove a small amount of carbon deposits on the surface, it could be put back into the reaction for use. The molten salt was cooled, dissolved, recrystallized and purified, and after replenishing a small amount of lost components, it could be recycled.

[0055] (III) Experimental Results

[0056] Testing showed that the conversion rate of 5-hydroxymethylfurfural in this example reached 95%, the selectivity of the target product 2,5-bis(hydroxymethyl)furan was 90%, and the total energy consumption of the system was reduced by 65% ​​compared with the traditional thermocatalytic method.

[0057] II. Example 2: Directed hydrogenation conversion of small molecules (styrene) from plastic pyrolysis

[0058] (I) Experimental Setup

[0059] The same reaction apparatus as in Example 1 is used, wherein the catalyst electrode (7) is as shown in the attached diagram. Figure 2 (b) shows a core-shell encapsulated catalyst with Fe as the core and Al2O3 as the shell, and a core-shell mass ratio of 2:3.

[0060] (II) Experimental Procedure

[0061] (1) System construction and activation:

[0062] 600g of ZnCl2-KCl eutectic molten salt (mass ratio 60:40) was placed in a reaction vessel. After purging the air by introducing high-purity N2, the electromagnetic heating stirrer (5) was started to heat the molten salt to 260℃, forming a uniform ionic molten pool under the disturbance of the rotor (6). The catalyst electrode made of Fe@Al2O3 core-shell catalyst and the reference electrode were placed in the molten salt and connected to the positive and negative terminals of the power supply. Methanol was injected as a hydrogen source at a rate of 0.04wt.% / min using an injection pump, and a cathode potential of -1.0V was applied to the catalyst electrode for pre-activation for 45 minutes to form a stable reaction interface.

[0063] (2) Substrate introduction and adsorption:

[0064] The substrate was styrene derived from small molecule plastic pyrolysis products of carbon-containing materials. Styrene was injected via an injection pump at a rate of 0.4 wt.% / min, with the mass ratio of styrene to molten salt controlled at 1:10. In a molten salt environment at 260°C, styrene molecules swelled and adsorbed onto the surface of the core-shell catalyst.

[0065] (3) Thermoelectric synergistic reaction and directional conversion:

[0066] Maintaining a reaction temperature of 260℃ and a cathode potential of -1.0V, methanol is electrochemically reduced to H* at the Fe active sites in the catalyst core. Under the induction of the electric field, H* overflows through the Al2O3 shell channel to the catalyst surface, where it undergoes a selective hydrogenation reaction with the C=C functional groups activated by styrene molecules to produce ethylbenzene.

[0067] (4) Product separation and material recycling:

[0068] After the reaction was completed, the product ethylbenzene was recovered using the same separation process as in Example 1. The catalyst was cleaned and recycled, and the molten salt was directly melted to replenish the loss and then reused.

[0069] (III) Experimental Results

[0070] The styrene conversion rate is 95%, the ethylbenzene selectivity reaches 90%, the system energy consumption is reduced by 42% compared with traditional thermocatalysis, and the catalyst retains 89% of its activity after being recycled 5 times.

[0071] III. Example 3: Directed Conversion of Coal Platform Molecules (Ethanol)

[0072] (I) Experimental Setup

[0073] The same reaction apparatus as in Example 1 is used, wherein the catalyst electrode (7) is as shown in the attached diagram. Figure 2 (a) shows a two-dimensional layered composite catalyst, which is a Co-MoS2 two-dimensional layered structure.

[0074] (II) Experimental Procedure

[0075] (1) System construction and activation:

[0076] 400g of a nitrate-chloride composite molten salt (LiNO3-NaNO3-ZnCl2 mass ratio 20:30:50) was placed in a reaction vessel, and heated to 200℃ under N2 protection to form an ionic molten pool. A catalyst electrode made of Co-MoS2 two-dimensional layered catalyst was placed in the molten salt, connected to a power source, and formic acid was injected as a hydrogen source at a rate of 0.02wt.% / min. A cathode potential of -0.6V was applied, and pre-activation was performed for 20 minutes.

[0077] (2) Substrate introduction and adsorption:

[0078] Phenol, a small molecule derived from carbon-containing materials—coal platform molecules—was used as a substrate. 40g of ethanol was injected, and the mass ratio of phenol to molten salt was controlled at 1:10. Phenol molecules diffused and adsorbed onto the catalyst surface in the molten salt.

[0079] (3) Thermoelectric synergistic reaction and directional conversion:

[0080] Maintaining 200℃ and a potential of -0.6V, formic acid generates H* on the catalyst surface. The electric field induces H* to overflow to the functional group sites activated by phenol, achieving directional conversion to cyclic ethanol.

[0081] (4) Product separation and material recycling:

[0082] Ethane products are recovered using conventional separation processes. The catalyst is calcined and then recycled, and the molten salt is recrystallized and reused.

[0083] (III) Experimental Results

[0084] The phenol conversion rate was 89%, the cyclic ethanol selectivity was 86%, and the system energy consumption was reduced by 43% compared with traditional thermocatalysis.

[0085] IV. Example 4: Directed Hydrogenation Conversion of Carbon-Containing Materials (Coal)

[0086] (I) Experimental Setup

[0087] As shown in the attached document Figure 1 The reaction apparatus shown includes a Hastelloy C276 reaction vessel (2), a reactor inlet (3), an electromagnetic heating stirrer (5), a rotor (6), a catalyst electrode (7), a reference electrode (8), a power supply (9), a hydrogen injection pump (10), a heating jacket (11), a feed pipe (12), a substrate injection pump (13), a reactor outlet (14), a filter (15), a condenser (16), a gas bag (17), and a reactor flange (18), etc. The connection relationships of each component are as shown in the attached diagram. Figure 1 Consistent. The catalyst electrode (7) adopts the method shown in the attached figure. Figure 2 (c) shows a mesoporous metal oxide supported catalyst with ZrO2 as the support and Fe-Cu bimetallic metal as the supported metal (the mass ratio of Fe to Cu is 2:1).

[0088] (II) Experimental Procedure

[0089] (1) System construction and activation

[0090] 600g of ZnCl2-KCl eutectic molten salt (mass ratio 60:40) was placed in a Hastelloy C276 reaction vessel (2). High-purity N2 (4) was introduced through the reactor inlet (3) to purge the air from the vessel. The electromagnetic heating stirrer (5) was started to heat the molten salt to 240°C, forming a uniform ionic molten pool under the disturbance of the rotor (6). The prepared Fe-Cu / ZrO2 mesoporous catalyst was coated on the surface of a conductive substrate to form a catalyst electrode (7). This electrode, along with the reference electrode (8), was placed in the molten salt and connected to the negative and positive terminals of the power supply (9), respectively. Water is continuously injected as a hydrogen source at a rate of 0.04 wt.% / min via an injection pump (10). The hydrogen source is heated by a heating jacket (11) and then enters the reaction system through a feed pipe (12). A cathode potential of -1.0V (relative to the Ag / AgCl reference electrode in the molten salt) is applied to the catalyst electrode. Pre-activation is performed for 45 minutes to allow the hydrogen source to undergo an electrochemical reduction reaction at the active site of the catalyst electrode, continuously generating hydrogen species (H*), and finally forming a stable “catalyst-molten salt ions-active hydrogen” interface.

[0091] (2) Substrate introduction and adsorption

[0092] The raw coal is pretreated by grinding it into particles with a diameter of less than 80 micrometers, treating the ash with a 5% hydrofluoric acid solution at a volume ratio of 1:1, and drying it to obtain a refined coal substrate containing carbon. After pre-activation, the coal substrate is directly mixed with molten salt in the reaction system, with the mass ratio of coal substrate to molten salt controlled at 1:10. Under the high temperature and ionic environment of molten salt at 240℃, the coal particles fully swell and diffuse, adsorbing onto the surface of the catalyst electrode.

[0093] (3) Thermoelectric synergistic reaction and directional conversion

[0094] The reaction continued for 6 hours, maintaining a reaction temperature of 240℃ and a cathode potential of -1.0V. This temperature provides the basic activation energy for functional groups such as carbon-hydrogen bonds and aromatic rings in the coal substrate, weakening their bond energies and putting them in an activated state. Under the synergistic effect of thermoelectricity, the -1.0V cathode potential drives the hydrogen source (water) to undergo electrochemical reduction at the active sites of the catalyst electrode, continuously generating adsorbed hydrogen species (H*). Under the directional induction of the applied electric field, H* overflows along the mesoporous channels and surface of the catalyst, precisely migrating to the target functional groups such as thermally activated aromatic rings and unsaturated carbon-carbon bonds in the coal substrate, undergoing selective hydrogenation reactions, and directionally generating alkane hydrogenation products, suppressing side reactions such as excessive cracking.

[0095] (4) Product separation and material recycling

[0096] After the reaction is complete, the feed and power supply are stopped. The gaseous products are carried out through the reactor outlet (14) by the carrier gas, and after impurities are removed by the filter (15), the condensable liquid products are condensed and recovered in the condenser (16), while the non-condensable products are collected in the gas bag (17). After the reaction vessel cools to room temperature, the reactor flange (18) is opened, and the reaction mixture is taken out. The liquid alkane products are obtained by dissolving, filtering, and centrifuging. The catalyst electrode is taken out, and after calcination to remove a small amount of carbon deposits on the surface, it can be reused in the reaction. The molten salt is cooled, dissolved, recrystallized and purified, and after replenishing a small amount of lost components, it can be recycled.

[0097] (III) Experimental Results

[0098] Tests showed that the coal feed conversion rate in this embodiment increased from 17% in the traditional process to 83%, the liquid product yield increased by 35% compared with the traditional process, and the selectivity of the target hydrogenation product alkane increased significantly from 11% to 66%.

[0099] Comparison with Example 1: Thermocatalytic reaction without electric field

[0100] The steps of Example 1 were repeated, but without applying a cathode potential (i.e., only thermal catalysis was performed). Other conditions (temperature, catalyst, reaction time) were exactly the same as in Example 1. The results showed that the HMF conversion was 40%, but the selectivity for BHMF was only 54%. This indicates that without the regulation of the electric field-induced hydrogen spillover mechanism, the reaction pathway is difficult to control precisely, resulting in a significant reduction in selectivity.

[0101] Comparative Example 2: Reactions at different temperatures

[0102] The steps of Example 1 were repeated, but the reaction temperature was lowered to 120°C (below the range of this invention). At a potential of -0.8V, the HMF conversion was only 25%, and the BHMF selectivity was 37%. This indicates that the temperature was too low, resulting in insufficient thermal activation, making it difficult to effectively activate the reactant molecules and leading to low overall reaction efficiency. Raising the reaction temperature to 350°C (above the range of this invention) resulted in a higher conversion rate, but the BHMF selectivity decreased to 63%, side reactions intensified, and molten salt volatilization and decomposition increased. This demonstrates the importance of the 150–300°C temperature range for this method.

[0103] In summary, this invention achieves efficient and highly selective directional conversion of various carbon-containing materials and their derivative small molecules under mild conditions through a coupling mechanism of molten salt thermoelectric synergy and electric field-induced hydrogen overflow. Specific embodiments fully verify the significant advantages of this method in terms of reaction selectivity, energy efficiency, catalyst stability, and substrate universality.

Claims

1. A method for the directional conversion of carbonaceous materials based on molten salt thermoelectric synergy, characterized in that, Includes the following steps: S1. System construction and activation: The molten salt medium is placed in a corrosion-resistant reaction vessel and heated to 150-300°C under inert gas protection to form a uniform ion pool. An electric field-responsive interface confined catalyst was placed in the molten salt as the working electrode, and a hydrogen source was continuously introduced at a rate of 0.01 to 0.05 wt.% / min. At the same time, a cathode potential of -0.5 V to -1.2 V relative to the reference electrode in the molten salt was applied to the working electrode for pre-activation for 1 to 60 minutes to form a stable interface. S2, Substrate introduction and adsorption: Carbon-containing material is continuously injected into the reaction system described in step S1 at a rate of 0.1 to 0.5 wt.% / min, and the mass ratio of the carbon-containing material to the molten salt medium is controlled to be 1:5 to 1:50, so that the carbon-containing material is adsorbed on the catalyst surface in the molten salt medium. S3. Thermoelectric Synergistic Reaction and Directed Conversion: Maintaining a reaction temperature of 150-300°C, under the synergistic effect of the cathode potential and temperature field, the hydrogen source is electrochemically reduced at the active site of the catalyst to generate adsorbed hydrogen species. The adsorbed hydrogen species undergo directional overflow under the induction of electric field force and migrate to the target functional groups of the thermally activated carbon-containing material to undergo a selective hydrogenation reaction. S4. Product Separation and Material Recycling: After the reaction is completed, the product is separated and recovered, and the catalyst and molten salt medium are recycled after treatment.

2. The method according to claim 1, characterized in that, The carbon-containing material is at least one of biomass, waste plastics, and coal.

3. The method according to claim 1, characterized in that, The carbon-containing material in step S2 is replaced with carbon-containing small molecules derived from the carbon-containing material, wherein the carbon-containing small molecules derived from the carbon-containing material are selected from at least one of biomass platform molecules, plastic pyrolysis small molecules, and coal platform molecules.

4. The method according to claim 3, characterized in that, The biomass platform molecule is furfural or 5-hydroxymethylfurfural; the plastic pyrolysis small molecule is styrene or propylene; the coal platform molecule is toluene or phenol.

5. The method according to claim 1, characterized in that, The molten salt medium is a nitrate, a chloride, or a mixture thereof.

6. The method according to claim 5, characterized in that, The nitrate is a LiNO3-NaNO3-KNO3 eutectic system; the chloride is a ZnCl2-KCl eutectic system.

7. The method according to claim 1, characterized in that, The electric field-responsive interface confined catalyst is selected from at least one of mesoporous metal oxide supported catalysts, two-dimensional layered composite catalysts, or core-shell encapsulated catalysts.

8. The method according to claim 7, characterized in that, The support for the mesoporous metal oxide supported catalyst is TiO2, Al2O3, ZrO2, SiO2 or CeO2, and the supported active metal is one or more of Ni, Co, Fe and Cu.

9. The method according to claim 1, characterized in that, The hydrogen source is at least one of water, alcohol, or acid.

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