A green hydrogenation method for crude anthracene using an electrochemical reactor

Abstract

This invention relates to a novel green hydrogenation process for crude anthracene under ambient temperature and pressure conditions using an electrochemical reactor. Specifically, it aims at the refined utilization of crude anthracene resources. A solid-state proton conductor electrochemical reactor, powered by an external power source, oxidizes the hydrogen-donating material at the anode into protons and electrons. The protons pass through a proton exchange membrane to the cathode, where they combine with electrons and are reduced to adsorbed hydrogen. This process enables highly selective, stepwise, and gradient hydrogenation of the complex crude anthracene system. This invention utilizes the in-situ hydrogen generation characteristic of the electrochemical reactor at the cathode to achieve highly selective, stepwise, and gradient hydrogenation of the complex crude anthracene system. Hydrogenation disrupts the intermolecular association effects of the crude anthracene components, achieving refined component separation and high-value applications. This new process achieves green and safe hydrogenation, reduces energy consumption and operational hazards, improves the overall efficiency of the reactor, reduces equipment costs, and maximizes the effective utilization of crude anthracene resources and the value of refined chemicals.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical engineering technology, specifically relating to a new method for green hydrogenation of crude anthracene using an electrochemical reactor under ambient temperature and pressure conditions. Background Technology

[0002] Anthracene oil is a crucial fraction in coal tar distillation, primarily containing important aromatic components such as anthracene, phenanthrene, carbazole, pyrene, and fluoranthene, with a yield of approximately 20%–25% of high-temperature coal tar. Current utilization methods for anthracene oil include its use as a feedstock for carbon black production, blending with pitch as fuel oil, or full hydrogenation to produce liquid fuels. However, traditional utilization methods do not address the specific characteristics of the individual components of anthracene oil.

[0003] After solvent treatment, anthracene oil components yield crude anthracene, mainly composed of three aromatic hydrocarbons: anthracene, phenanthrene, and carbazole. Traditional separation of crude anthracene components involves solvent extraction and distillation, but due to the association effect between aromatic hydrocarbon molecules, separation and purification are difficult, and these processes suffer from high energy consumption and low efficiency. Selective hydrogenation, by disrupting the association effect between aromatic hydrocarbon molecules, facilitates the efficient separation of crude anthracene components. Traditional catalytic hydrogenation technology utilizes hydrogen as a reducing agent and selects a suitable catalyst to hydrogenate and upgrade polycyclic aromatic hydrocarbons to generate hydrogenated products under appropriate temperature and pressure. However, the catalytic hydrogenation refining process of crude anthracene requires high temperature and high hydrogen pressure. Firstly, deep hydrogenation requires a high concentration of adsorbed hydrogen on the catalyst surface; secondly, the low solubility of hydrogen necessitates high hydrogen pressure during the reaction; and thirdly, the selectivity of the hydrogenated products is poor, making it difficult to meet the separation requirements and high-value applications of anthracene oil.

[0004] The electrochemical reactor utilizes the powerful and sustainable nature of electrons as a reagent, activating the substrate through cathode surface reduction, successfully solving the problem of difficult hydrogen transfer to the catalyst surface in traditional three-phase reactions. It transforms the processes of hydrogen dissolution, mass transfer, and dissociation adsorption in existing hydrogenation methods into an electrochemical in-situ generation process where hydrogen is adsorbed onto the catalyst and directly reacts with the adsorbed unsaturated reactants in a liquid-phase hydrogenation reaction. This hydrogenation method can achieve sufficient hydrogen concentration adsorbed on the catalyst surface at ambient temperature and pressure, eliminating the high pressure, high energy consumption, and equipment complexity caused by hydrogen mass transfer resistance in external hydrogen supply methods. Furthermore, based on the independent yet coupled nature of the electrochemical reaction processes at the cathode and anode, selective deep hydrogenation can achieve staged purification and quality improvement. Summary of the Invention

[0005] This invention provides a novel green hydrogenation method for crude anthracene under ambient temperature and pressure conditions using an electrochemical reactor. Specifically, it aims at the refined utilization of crude anthracene resources. Addressing the problems of harsh conditions, poor selectivity of hydrogenation products, and difficulties in separation and purification associated with traditional catalytic hydrogenation methods, this invention utilizes the in-situ hydrogen generation at the cathode of the electrochemical reactor to perform highly selective, stepwise, and gradient hydrogenation on the complex crude anthracene system. Hydrogenation disrupts the intermolecular association effects of the crude anthracene components, achieving refined component separation and high-value applications. This new process achieves green and safe hydrogenation, reduces energy consumption and operational hazards, improves the overall efficiency of the reactor, reduces equipment costs, and maximizes the effective utilization of crude anthracene resources and the value of refined chemicals.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A green hydrogenation method for crude anthracene using an electrochemical reactor aims to make rational use of crude anthracene resources. The method employs a solid-state proton conductor electrochemical reactor under applied electrical energy. At the anode, the hydrogen-donating material is oxidized into protons and electrons. The protons pass through a proton exchange membrane to the cathode, where they combine with electrons and are reduced to adsorbed hydrogen. This allows for highly selective, stepwise, gradient hydrogenation of the complex crude anthracene system. Most 2-3 ring polycyclic aromatic hydrocarbons in the crude anthracene are saturated with hydrogen, and nitrogen- and sulfur-containing heteroatoms are completely removed. Even polycyclic aromatic hydrocarbons that are difficult to convert, especially those with four or more rings, are achieved with a high degree of hydrogenation.

[0008] The applied electrical energy refers to a constant current mode with a current density of 4–12 mA / cm². 2 .

[0009] The temperature of the crude anthracene hydrogenation reaction occurring at the cathode is controlled at 20–25 °C.

[0010] The hydrogen supply material for the anode is hydrogen gas or water.

[0011] The proton exchange membrane is a perfluorosulfonic acid proton exchange membrane.

[0012] The catalyst layer of the cathode is one of Pt-Ni, Pt-Pd, and Pt-Ru, and the loading of the alloy catalyst is 0.5–4.5 mg / cm³. 2 .

[0013] The concentration of the crude anthracene mixture in the cathode is 4–10 g / L, the solvent is a mixture of DMF and sulfuric acid, and the flow rate is 20–120 mL / min.

[0014] Compared with existing technologies, the beneficial effects of this invention are:

[0015] 1) This invention provides a safe and green new reaction process for the graded gradient hydrogenation of crude anthracene complex systems. It utilizes the low electrochemical window of the hydrogen-donating material to generate in-situ adsorbed hydrogen that directly participates in the liquid-phase reaction, thereby coordinating and enhancing the reaction process. This avoids the conventional high-pressure hydrogenation method, reduces energy consumption and operational hazards, and enables the engineering of clean hydrogenation refining of crude anthracene.

[0016] 2) The solid-state proton conductor electrochemical reaction system proposed in this invention overcomes the shortcomings of traditional liquid electrolyte electrochemical hydrogenation reactions, such as difficulty in control, poor product selectivity, and difficulty in product purification. It has the characteristics that the electrochemical reaction processes of the cathode and anode are both independent and coupled. Based on this, a unique and efficient multi-process integrated coupled enhanced reaction device is provided. Through highly selective graded gradient hydrogenation, the components are finely separated and utilized at high value, while reducing mass transfer resistance and activation resistance, improving the overall efficiency of the reactor and reducing equipment costs.

[0017] 3) Most of the 2-3 ring polycyclic aromatic hydrocarbons in crude anthracene were saturated hydrogenated, and organic compounds containing nitrogen and sulfur heteroatoms were completely removed. Polycyclic aromatic hydrocarbons that are difficult to convert, especially those with more than four rings, were also hydrogenated to a high degree. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the electrochemical deep hydrogenation of crude anthracene in this invention.

[0019] In the diagram: 1-anode catalyst layer, 2-proton exchange membrane, 3-cathode catalyst layer. Detailed Implementation

[0020] The present invention is further illustrated below by way of embodiments, but these embodiments are not intended to limit the invention to the scope of the embodiments described. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] See Figure 1 As shown, a green hydrogenation method for crude anthracene using an electrochemical reactor aims to make rational use of crude anthracene resources. The solid proton conductor type electrochemical reactor consists of a proton exchange membrane 2, a catalyst layer, a gas diffusion layer, and bipolar plates. The catalyst layer includes an anode catalyst layer 1 and a cathode catalyst layer 3. Under applied electrical energy, the hydrogen-donating substance is oxidized into protons and electrons at the anode. The protons pass through the proton exchange membrane 2 to the cathode, where they combine with electrons and are reduced to adsorbed hydrogen, thus performing highly selective, stepwise, and gradient hydrogenation on the complex crude anthracene system.

[0022] The applied electrical energy refers to a constant current mode with a current density of 4–12 mA / cm². 2 .

[0023] The temperature of the crude anthracene hydrogenation reaction occurring at the cathode is controlled at 20–25 °C.

[0024] The hydrogen supply material for the anode is hydrogen gas or water.

[0025] The proton exchange membrane 2 is a perfluorosulfonic acid proton exchange membrane.

[0026] The cathode catalyst layer 3 is one of Pt-Ni, Pt-Pd, and Pt-Ru, and the loading of the alloy catalyst is 0.5–4.5 mg / cm³. 2 .

[0027] The concentration of the crude anthracene mixture at the cathode is 4–10 g / L, the solvent is a mixture of DMF and sulfuric acid, and the flow rate is 20–120 mL / min.

[0028] Example 1:

[0029] Loading 4mg / cm 2 Pt-Ni / C carbon paper was used as the cathode, with a loading of 0.5 mg / cm². 2 The Pt gas diffusion electrode was used as the anode, and the Nafion 117 membrane was used as the proton exchange membrane. Hydrogen was fed to the anode at a rate of 30 mL / min; a 5 g / L crude anthracene mixed solution was introduced into the cathode, and the outflowing solution was recirculated back into the cathode at a rate of 85 mL / min. The reaction temperature was 25 °C. The electrochemical reactor was operated at a rate of 4 mA / cm². 2 After 0.5 hours of constant current operation, the products were collected for gas chromatography analysis. The hydrogenation conversion rate of anthracene, phenanthrene, and carbazole in crude anthracene was 100%, and the hydrogenation products were mainly dihydrogen and tetrahydrogen products, with a current efficiency of 87%. In Example 1 of this invention, under conditions of low applied power and different catalyst layers, i.e., relatively basic reaction conditions, the products can be simply hydrogenated to obtain products with relatively low saturation, such as dihydrogen and tetrahydrogen products, which can be used as new fuels through other pathways.

[0030] Example 2:

[0031] Using a loading of 4 mg / cm 2 Pt-Pb / C carbon paper was used as the cathode, with a loading of 0.5 mg / cm². 2 The Pt gas diffusion electrode was used as the anode, and the Nafion 117 membrane was used as the proton exchange membrane. Hydrogen was fed to the anode at a rate of 15 mL / min; a 4 g / L crude anthracene mixture was introduced to the cathode, and the outflowing solution was recirculated back into the cathode at a rate of 20 mL / min. The reaction temperature was 25 °C. The electrochemical reactor was operated at 10 mA / cm². 2After 1.5 hours of constant current operation, the mixed solution gradually changed from a deep yellow to a colorless and clear solution, at which point the product was collected for gas chromatography analysis. The hydrogenation conversion rate of anthracene, phenanthrene, and carbazole in the crude anthracene was 100%. Anthracene, fluorene, naphthalene, and fluoranthene were almost completely converted to all-hydrogen products. After deep hydrogenation of phenanthrene, the hydrogenation products contained no dihydrogen or tetrahydrogen products, and were mainly octahydrophenanthrene, with a relative content of 71.1%. The N in carbazole, the S in quinoline, and the S in benzothiazole were all completely removed after hydrogenation. In Example 2 of this invention, under conditions of increased external power and different catalyst layers (i.e., higher reaction conditions), deep hydrogenation of the product can be achieved, resulting in a higher degree of hydrogenation and the absence of low-saturation hydrogenation products, such as dihydrogen and tetrahydrogen products.

[0032] Example 3:

[0033] Using a loading of 4 mg / cm 2 Pt-Pb / C carbon paper was used as the cathode, with a loading of 0.5 mg / cm². 2 The Pt gas diffusion electrode was used as the anode, and the Nafion 117 membrane was used as the proton exchange membrane. Distilled water was fed to the anode at a rate of 20 mL / min; a 4 g / L crude anthracene mixture was introduced into the cathode, and the outflowing solution was recirculated back into the cathode at a rate of 20 mL / min. The reaction temperature was 25 °C. The electrochemical reactor was operated at 12 mA / cm². 2 After 2 hours of constant current operation, the mixed solution gradually changed from a deep yellow to a colorless and clear solution, at which point the products were collected for gas chromatography analysis. The hydrogenation conversion rates of anthracene, phenanthrene, and carbazole in crude anthracene were 100%. Anthracene, fluorene, and naphthalene were completely converted to perhydroanthracene, perhydrofluorene, and perhydronaphthalene, respectively. After deep hydrogenation of phenanthrene, the main hydrogenation products were octahydrophenanthrene and perhydrophenanthrene, with relative contents of 69.5% and 28.9%, respectively. After deep hydrogenation of pyrene, the main hydrogenation products were decahydropyrene and perhydropyrene, with relative contents of 96.5% and 3.5%, respectively. The nitrogen (N) in carbazole and the sulfur (S) in benzothiazole were completely removed after hydrogenation.

[0034] Comparative Example 1:

[0035] The reaction was carried out in a high-temperature, high-pressure reactor. The reactant was crude anthracene, and the catalyst was Pt-Ni / Al2O3. Hydrogen gas was introduced to replace the air in the reactor, and the pressure reducing valve was adjusted to achieve an initial pressure of 4 MPa. The reaction temperature was 320℃, the stirrer speed was maintained at 300 r / min, and the reaction was carried out for 1.5 h. The reactor was then allowed to cool statically, the gas was vented, and the product was taken out for gas chromatography analysis. The anthracene hydrogenation conversion rate in the crude anthracene reached 93%, and the total hydrogen anthracene content in the hydrogenation product was 43.2%, including tetrahydroanthracene and octahydroanthracene. The phenanthrene hydrogenation conversion rate was 87%, and the total hydrogen phenanthrene content in the hydrogenation product was 35.5%, including dihydrophenanthrene, tetrahydrophenanthrene, and octahydrophenanthrene. The carbazole hydrogenation conversion rate was 97%, and no nitrogen-containing heteroatom compounds were detected in the hydrogenation product. Comparative Example 1 is a traditional catalytic hydrogenation method, which cannot achieve selective hydrogenation. The product contains dihydro, tetrahydro, octahydro, and total hydrogen, as well as low-saturation and high-saturation products, and various hydrogenation levels, making it difficult to achieve fractional separation of the products.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A green hydrogenation method for crude anthracene using an electrochemical reactor, characterized in that, A solid proton conductor electrochemical reactor was used to oxidize the hydrogen-supplying material into protons and electrons at the anode under external power. The protons passed through the proton exchange membrane to the cathode and were reduced to adsorbed hydrogen by combining with electrons at the cathode. This process was used to perform graded gradient hydrogenation on the complex crude anthracene system in the crude anthracene mixture. The applied electrical energy refers to a constant current mode with a current density of 4–12 mA / cm². 2 ; The catalyst layer of the cathode is one of Pt-Ni, Pt-Pd, and Pt-Ru, and the loading of the alloy catalyst is 0.5–4.5 mg / cm³. 2 .

2. The green hydrogenation method for crude anthracene using an electrochemical reactor according to claim 1, characterized in that, The temperature of the crude anthracene hydrogenation reaction occurring at the cathode is controlled at 20–25 °C.

3. The green hydrogenation method for crude anthracene using an electrochemical reactor according to claim 1, characterized in that, The hydrogen supply material for the anode is hydrogen gas or water.

4. The green hydrogenation method for crude anthracene using an electrochemical reactor according to claim 1, characterized in that, The proton exchange membrane is a perfluorosulfonic acid proton exchange membrane.

5. A green hydrogenation method for crude anthracene using an electrochemical reactor according to claim 1, characterized in that, The concentration of the crude anthracene mixture in the cathode is 4–10 g / L, the solvent is a mixture of DMF and sulfuric acid, and the flow rate is 20–120 mL / min.

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