Electrochemical desulfurization method of petroleum coke
By using an electrochemical method involving graphite electrodes and bromide acetate electrolyte solution, the sulfide bonds in high-sulfur petroleum coke are broken at low temperatures, solving the problem of difficult desulfurization of high-sulfur petroleum coke and achieving a high-efficiency, low-energy-consumption, and environmentally friendly desulfurization effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2025-01-08
- Publication Date
- 2026-07-24
AI Technical Summary
Existing technologies are insufficient for efficiently removing sulfur from high-sulfur petroleum coke at low temperatures, and conventional methods suffer from high energy consumption, safety hazards, and pollution problems.
Using graphite as the anode and cathode, high-sulfur petroleum coke is electrochemically treated at low temperature using an electrolytic solution of bromide and acetate. The oxidizing environment generated by electrolysis breaks the sulfide bonds, thereby achieving the oxidation and removal of sulfur.
It achieves a high-efficiency, low-temperature, green and clean desulfurization process, maintains the physical and chemical properties of petroleum coke, and the desulfurization products are easy to handle, thus reducing production costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of desulfurization technology and relates to an electrochemical desulfurization method for petroleum coke. Background Technology
[0002] Petroleum coke is a solid coke formed after the pyrolysis of residual oil at a certain temperature. It is a black, lumpy char with a typical amorphous carbon structure. The carbon content is typically above 80%, with the remainder composed of sulfur (S), nitrogen (N), oxygen (O), and small amounts of metallic elements. Based on the sulfur content, petroleum coke can be classified into high-sulfur coke (>3wt%), medium-sulfur coke, and low-sulfur coke (<1.5wt%). Its quality is mainly affected by the quality of the crude oil and subsequent residual oil coking processes. Low-sulfur coke is generally used to prepare graphite electrodes and graphite anodes for lithium-ion batteries; medium-sulfur coke is often used to prepare prebaked anodes in aluminum electrolysis; and high-sulfur coke is mostly used for fuel combustion in chemical plants. Currently, the proportion of high-sulfur petroleum coke is increasing, while low-sulfur petroleum coke resources are scarce. Direct use of high-sulfur petroleum coke not only causes severe corrosion to equipment but also results in SO2 emissions, polluting the atmosphere, thus limiting its utilization. Currently, the sulfur in high-sulfur petroleum coke mainly exists in the form of organic and inorganic sulfur. In petroleum coke, most sulfur (S) adheres to the surface as sulfides, while a small amount exists in organic form, linked to carbon rings. The resulting structures mainly fall into four categories: thiols, sulfides, disulfides, and thiophenes. Among these, the organic sulfur form, CS / C=S, is difficult to remove, while inorganic sulfur can be released as H2S gas at certain temperatures.
[0003] Desulfurization processes mainly include: high-temperature calcination desulfurization, oxidation desulfurization, metal compound desulfurization, and medium gas desulfurization. In calcination desulfurization, the temperature must be above 1250℃ for desulfurization to begin. Oxidation desulfurization involves mixing an oxidant with high-sulfur petroleum coke and, under specific experimental conditions, reducing and removing sulfur from the petroleum coke. Metal compound desulfurization involves introducing metal compounds such as NaOH, KOH, and FeCl3 into high-sulfur petroleum coke and desulfurizing it under specific temperature and pressure. Medium gas desulfurization involves introducing a medium gas (H2, O2, or N2, etc.) during the heating process of high-sulfur petroleum coke to react with sulfur, thus achieving desulfurization.
[0004] Existing technology CN2024100342055 discloses a desulfurization method for high-sulfur petroleum coke. The method involves pulverizing the high-sulfur petroleum coke and adding sodium carbonate powder for mechanical ball milling (360-720 r / min) to obtain a petroleum coke-alkali mixture. This mixture is then placed in a high-temperature desulfurization reactor, where an inert atmosphere is introduced to purge air. Finally, methane gas is introduced and the reactor is heated to 700-1000℃ and held at that temperature for 60-150 min. The mixture is then cooled, washed, and dried to obtain low-sulfur, high-carbon petroleum coke with a desulfurization rate of 75.37%. However, this existing technology requires alkaline chemical reagents, which poses problems for subsequent wastewater treatment. Furthermore, the high operating temperature (700-1000℃) results in high energy consumption, and the presence of methane gas during the reaction also increases safety hazards.
[0005] Existing technology 2020102561699 discloses a method for electrochemical desulfurization of petroleum coke, which involves crushing the petroleum coke to below 1 cm; using foamed nickel and tin oxide coated with petroleum coke as the anode and cathode, respectively; and electrolyzing for 8 hours in CaCl2 salt under argon protection at 900°C, with a measured desulfurization rate of 83.2% after electrolysis. However, this existing technology requires a relatively high temperature, and the desulfurization effect decreases as the temperature decreases, increasing energy consumption during operation. Summary of the Invention
[0006] The purpose of this invention is to provide a low-temperature electrochemical desulfurization method for petroleum coke.
[0007] To achieve the above objectives, the present invention provides the following technical solution:
[0008] An electrochemical desulfurization method for petroleum coke includes the following steps:
[0009] S1. Mix petroleum coke and electrolytic solution at a solid-liquid ratio of 1g:1-9.5mL to obtain a slurry;
[0010] S2. Using graphite as the anode and cathode, the slurry is electrolyzed at 5-80℃ for 4-20 hours to purify it and obtain desulfurized petroleum coke.
[0011] The electrolyte solution includes bromide and acetate.
[0012] Graphite plates have strong electrical conductivity, are resistant to acids and alkalis, and are not prone to introducing impurities, making them suitable as anodes and cathodes.
[0013] In one preferred embodiment, the petroleum coke is pulverized into fine coke powder and then mixed with the electrolyte solution.
[0014] In one preferred embodiment, the fine coke has a particle size of less than 100 μm.
[0015] Excessively large particle size hinders the dispersion of petroleum coke in solution, reducing the desulfurization effect.
[0016] In one preferred embodiment, the bromide salt is at least one of calcium bromide, lithium bromide, silver bromide, and magnesium bromide.
[0017] In one preferred embodiment, the acetate is at least one of sodium acetate and potassium acetate.
[0018] In one preferred embodiment, the bromide and acetate are mixed uniformly in a mass ratio of 1:(0.5-15), preferably 1:(3-15); more preferably 1:(5-9).
[0019] If the mass ratio of bromide to acetate is too small, the desulfurization effect is poor; if the ratio is too large, the desulfurization effect is not significantly changed, but the reagent cost increases considerably.
[0020] In one preferred embodiment, the bromide salt and acetate are mixed by mechanical grinding and / or impregnation.
[0021] In one preferred embodiment, the solid-liquid ratio of solute to solvent in the electrolyte solution is 1g:4-20ml, preferably 1g:4-12ml.
[0022] The solutes are bromide and acetate.
[0023] In one preferred embodiment, the solvent in the electrolyte solution is water.
[0024] In one preferred embodiment, the solid-liquid ratio of petroleum coke to electrolytic solution is 1 g: 4.5-9.5 mL.
[0025] Too low a solid-liquid ratio increases desulfurization costs, while too high a solid-liquid ratio reduces desulfurization efficiency.
[0026] In one preferred embodiment, the electrolysis current is 0.1-7A, preferably 3-7A.
[0027] Too low a current results in low desulfurization efficiency, while too high a current increases desulfurization costs and does not significantly improve the desulfurization effect.
[0028] In one preferred embodiment, the electrolysis temperature is 10-70°C.
[0029] In one preferred embodiment, the electrolysis time is 7-14 hours.
[0030] In one preferred embodiment, the electrolysis is performed with stirring at a speed of 1000-1500 r / min, preferably 1000-1300 r / min.
[0031] In one preferred embodiment, purification involves washing the product with water, separating the solid and liquid phases, and drying.
[0032] In one preferred embodiment, the solid-liquid separation is vacuum filtration.
[0033] The following is intended to further explain the present invention:
[0034] This invention prepares a specific electrolytic solution by uniformly mixing bromide, acetate, and aqueous solution. This solution is then used to electrolytically desulfurize a slurry of high-sulfur petroleum coke mixed with the electrolytic solution, ultimately yielding a low-sulfur petroleum coke product. The principle of sulfur removal from high-sulfur petroleum coke in this invention is as follows: Sulfur in petroleum coke typically exists in the form of sulfides, thiophenes, and sulfides, especially thiophenes. Because sulfur and carbon in their molecular structure are bonded by stable covalent bonds, these sulfides are difficult to remove by conventional oxidation, heat treatment, or chemical methods. Thiophene sulfides are extremely stable at room temperature; their structure can only be destroyed under high temperature, specific catalysts, or strong oxidizing conditions. Complete removal of sulfur from petroleum coke typically requires temperatures above 1600℃. Therefore, ordinary desulfurization methods cannot achieve satisfactory desulfurization results. By applying an external voltage, current is passed through the electrolytic cell, thereby creating an oxidizing environment. During electrolysis, the added electrolyte not only increases the conductivity of the solution but also generates strong oxidizing substances (such as oxygen, ozone, and hydroxyl radicals) through electrochemical reactions. These oxidants have strong oxidizing power, and when petroleum coke comes into contact with them, they can break its sulfide bonds, oxidizing sulfur into soluble sulfate or other oxygen-containing sulfur compounds, thereby gradually removing sulfur from the petroleum coke. The desulfurization effect can be improved by changing the electrolysis conditions (current, time, and temperature). This invention provides a highly efficient and deep electrochemical desulfurization method for high-sulfur petroleum coke. This invention not only has high desulfurization efficiency but also a green and clean process, which can significantly reduce production costs and increase the application value of high-sulfur petroleum coke.
[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0036] (1) The equipment of the present invention has simple requirements, mild process conditions, and low temperature, which greatly reduces energy consumption.
[0037] (2) The present invention can achieve selective oxidation of sulfides by controlling conditions such as current, without significantly destroying the carbon structure in petroleum coke, thereby preserving the physical and chemical properties of petroleum coke.
[0038] (3) This invention does not produce harmful gases, and the desulfurization products are mostly water-soluble sulfate or sulfite, which are easy to collect and treat and have good environmental performance. Attached Figure Description
[0039] Figure 1SEM images of the high-sulfur petroleum coke feedstock in Example 1: (a) 100x; (b) 1000x; (c) 5000x;
[0040] Figure 2 These are SEM images of high-sulfur petroleum coke after electrolysis in Example 1; (a) 100x; (b) 1000x; (c) 5000x;
[0041] Figure 3 These are XRD patterns of high-sulfur petroleum coke before and after electrolysis in Example 1; (a) raw material; (b) petroleum coke after desulfurization. Detailed Implementation
[0042] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0043] Example 1
[0044] Five grams of high-sulfur petroleum coke from a domestic factory were taken, containing 83.37 wt.% fixed carbon, 12.2 wt.% volatile matter, 0.2 wt.% ash, and 6.52 wt.% sulfur. The coke was crushed to below 75 μm (200 mesh) to obtain fine coke powder. Pressed graphite plates were used as the cathode and anode materials. Sodium bromide and sodium acetate were mixed uniformly using mechanical grinding at a ratio of 1:5 (g:g). The mixed salt was then stirred uniformly with an aqueous solution at a ratio of 1:12 (g:ml) to obtain the electrolytic solution. The fine coke powder was then mixed uniformly with the electrolytic solution at a ratio of 1:4.5 (g:ml). Electrolysis was carried out at 45℃, with a cell current of 3A, an electrolysis time of 8 hours, and a stirring speed of 1100 r / min. The electrolyzed petroleum coke was washed multiple times with water, filtered, and dried. The sulfur content of the electrolyzed petroleum coke was measured to be 0.59 wt.%, and the desulfurization rate was 91%. XRD patterns of petroleum coke before and after electrolysis are as follows: Figure 3 As shown, a is the raw material; b is the petroleum coke after desulfurization; the characteristic peaks of the petroleum coke after electrolysis have not changed compared with those before electrolysis, indicating that the structure of the petroleum coke after electrolysis has not introduced other impurity elements.
[0045] Example 2
[0046] Five grams of high-sulfur petroleum coke from a domestic factory were taken, containing 83.37 wt.% fixed carbon, 12.2 wt.% volatile matter, 0.2 wt.% ash, and 6.52 wt.% sulfur. The coke was crushed to below 75 μm (200 mesh) to obtain fine coke powder. Pressed graphite plates were used as the cathode and anode materials. Sodium bromide and potassium acetate were mixed uniformly by mechanical grinding at a ratio of 1:6 (g:g). The mixed salt was then stirred uniformly with an aqueous solution at a ratio of 1:12 (g:ml) to obtain the electrolytic solution. The fine coke powder was mixed uniformly with the electrolytic solution at a ratio of 1:4.5 (g:ml). Electrolysis was carried out at 45℃, with a cell current of 3A, an electrolysis time of 8 hours, and a stirring speed of 1100 r / min. The electrolyzed petroleum coke was washed multiple times with water, filtered, and dried. The sulfur content of the electrolyzed petroleum coke was measured to be 0.88 wt.%, and the desulfurization rate was 86.5%.
[0047] Comparative Example 1
[0048] Replace sodium acetate
[0049] Five grams of high-sulfur petroleum coke from a domestic factory were taken, containing 83.37 wt.% fixed carbon, 12.2 wt.% volatile matter, 0.2 wt.% ash, and 6.52 wt.% sulfur. The coke was crushed to below 75 μm (200 mesh) to obtain fine coke powder. Pressed graphite plates were used as the cathode and anode materials. Sodium bromide and ammonium acetate were mixed uniformly using mechanical grinding at a ratio of 1:5 (g:g). The mixed salt was then stirred uniformly with an aqueous solution at a ratio of 1:12 (g:ml) to obtain the electrolytic solution. The fine coke powder was then mixed uniformly with the electrolytic solution at a ratio of 1:4.5 (g:ml). Electrolysis was carried out at 45℃, with a cell current of 3A, an electrolysis time of 8 hours, and a stirring speed of 1100 r / min. The electrolyzed petroleum coke was washed multiple times with water and dried. The sulfur content of the electrolyzed petroleum coke was measured to be 5.27 wt.%, and the desulfurization rate was 19.17%.
[0050] Comparative Example 2
[0051] No electrolyte solution added
[0052] Five grams of high-sulfur petroleum coke from a domestic factory were taken, containing 83.37 wt.% fixed carbon, 12.2 wt.% volatile matter, 0.2 wt.% ash, and 6.52 wt.% sulfur. This coke was crushed to below 75 μm (200 mesh) to obtain fine coke powder. Pressed graphite plates were used as the cathode and anode materials. The fine coke powder was mixed with an aqueous solution at a ratio of 1:4.5 (g:ml). Electrolysis was carried out at 45℃, with a cell current of 3A, an electrolysis time of 8 hours, and a stirring speed of 1100 r / min. The electrolyzed petroleum coke was washed multiple times with water and dried. The sulfur content of the electrolyzed petroleum coke was measured to be 6.38 wt.%, and the desulfurization rate was 2.15%.
[0053] Comparative Example 3
[0054] Add only acetate
[0055] Five grams of high-sulfur petroleum coke from a domestic factory were taken, containing 83.37 wt.% fixed carbon, 12.2 wt.% volatile matter, 0.2 wt.% ash, and 6.52 wt.% sulfur. This coke was crushed to below 75 μm (200 mesh) to obtain fine coke powder. Pressed graphite plates were used as the anode and cathode materials. Sodium acetate and aqueous solution were mixed evenly at a ratio of 1:12 (g:ml) to obtain the electrolytic solution. The fine coke powder was then mixed evenly with the electrolytic solution at a ratio of 1:4.5 (g:ml). Electrolysis was carried out at 45℃ with a current of 3A for 8 hours and a stirring speed of 1100 r / min. The electrolyzed petroleum coke was washed multiple times with water and dried. The sulfur content of the electrolyzed petroleum coke was measured to be 6.11 wt.%, and the desulfurization rate was 6.29%.
[0056] Comparative Example 4
[0057] Add only bromide salt
[0058] Five grams of high-sulfur petroleum coke from a domestic factory were taken, containing 83.37 wt.% fixed carbon, 12.2 wt.% volatile matter, 0.2 wt.% ash, and 6.52 wt.% sulfur. The coke was crushed to below 75 μm (200 mesh) to obtain fine coke powder. Pressed graphite plates were used as the cathode and anode materials. Sodium bromide and aqueous solution were mixed evenly at a ratio of 1:12 (g:ml) to obtain the electrolytic solution. The fine coke powder was then mixed evenly with the electrolytic solution at a ratio of 1:4.5 (g:ml). Electrolysis was carried out at 45℃ with a current of 3A for 8 hours and a stirring speed of 1100 r / min. The electrolyzed petroleum coke was washed multiple times with water and dried. The sulfur content of the electrolyzed petroleum coke was measured to be 5.95 wt.%, and the desulfurization rate was 8.74%.
[0059] Example 2
[0060] Example 1 was repeated, except that sodium bromide and sodium acetate were mixed uniformly by mechanical grinding at ratios of 1:0.5, 1:1, 1:3, 1:5, 1:7, and 1:15 (g:g), respectively. Everything else was the same as in Example 1, and the results after desulfurization are shown in the table below.
[0061] Table 1. Effect of different ratios of sodium bromide and sodium acetate on desulfurization efficiency
[0062]
[0063] The higher the sodium bromide ratio, the more difficult it is to remove sulfur from high-sulfur petroleum coke, which is detrimental to the subsequent value-added utilization of petroleum coke.
[0064] Example 3
[0065] Example 1 was repeated, except that the mixed salt and aqueous solution were stirred evenly at ratios of 1:4, 1:8, 1:12, 1:16, and 1:20 (g:ml) to obtain an electrolyte solution. Everything else was the same as in Example 1, and the desulfurization results are shown in the table below.
[0066] Table 2. Effects of different solid-liquid ratios of salt and aqueous solution after mixing on desulfurization efficiency.
[0067]
[0068] The lower the concentration of the electrolyte, the less oxidant can be produced during electrolysis, which reduces the oxidation effect of structures such as thiophene and is not conducive to the subsequent value-added utilization of petroleum coke.
[0069] Example 4
[0070] Example 1 was repeated, except that the fine coke powder and the electrolytic solution were mixed evenly in ratios of 1:1, 1:2, 1:7, and 1:9.5 (g:ml). Everything else was the same as in Example 1. The results after desulfurization are shown in the table below.
[0071] Table 3. Effect of different ratios of fine coke to electrolytic solution on desulfurization efficiency
[0072]
[0073] Example 5
[0074] Example 1 is repeated, except that the electrolytic cell current is set to 1, 3, 5, and 7 A respectively.
[0075] Table 4. Effects of different currents on desulfurization efficiency
[0076] Desulfurization rate / % 77.46 91 92.03 92.85
[0077] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for electrochemical desulfurization of petroleum coke, characterized in that, Includes the following steps: S1. Mix petroleum coke and electrolytic solution at a solid-liquid ratio of 1g:1-9.5mL to obtain a slurry; S2. Using graphite as the anode and cathode, the slurry is electrolyzed at 5-80℃ for 4-20 hours to purify it and obtain desulfurized petroleum coke. The electrolyte solution includes bromide and acetate; The acetate is at least one of sodium acetate and potassium acetate; In the electrolytic solution, the solid-liquid ratio of solute to solvent is 1g:4-12ml; The electrolysis current is 0.1-7A; The bromide and acetate were mixed evenly in a mass ratio of 1:(5-15).
2. The petroleum coke electrochemical desulfurization method according to claim 1, characterized in that, The solid-liquid ratio of petroleum coke and electrolytic solution is 1g:4.5-9.5mL.
3. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that, Electrolysis temperature: 10-70℃; Electrolysis time: 7-14h.
4. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that, During electrolysis, the mixture is stirred at a speed of 1000-1500 r / min.
5. The method for electrochemical desulfurization of petroleum coke according to any one of claims 1-4, characterized in that, Purification involves washing the product with water, separating the solid and liquid phases, and drying.
6. The method for electrochemical desulfurization of petroleum coke according to claim 5, characterized in that, The solid-liquid separation is performed by vacuum filtration.