Petroleum coke electrochemical desulfurization method

Abstract

The invention belongs to the technical field of desulfurization, and relates to a petroleum coke electrochemical desulfurization method which comprises the following steps: S1, mixing petroleum coke and an electrolytic solution according to a solid-to-liquid ratio of 1g: (1-9.5) mL to obtain slurry; s2, graphite serves as a cathode and an anode, the slurry is electrolyzed for 4-20 h at the temperature of 5-80 DEG C, purification is conducted, and desulfurized petroleum coke is obtained; the electrolytic solution comprises bromide and acetate. The method comprises the following steps: uniformly mixing bromide, acetate and an aqueous solution to prepare a specific electrolytic solution, and carrying out electrolytic desulfurization on slurry obtained by mixing high-sulfur petroleum coke and the electrolytic solution to finally obtain a low-sulfur petroleum coke product. The invention provides an electrochemical efficient deep desulfurization method for high-sulfur petroleum coke. According to the method, the desulfurization efficiency is high, the technological process is green and clean, the production cost can be reduced to a great extent, and the application value of the high-sulfur petroleum coke is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurization and relates to a petroleum coke electrochemical desulfurization method. Background Art

[0002] Petroleum coke is a solid coke formed after the residual oil is cracked at a certain temperature. It is black and blocky and is a typical amorphous carbon structure. Among them, the C content is usually above 80%, and the rest is composed of S, N, O and a small amount of metal elements. According to the different sulfur content in petroleum coke, it can be divided into high-sulfur coke (>3wt%), medium-sulfur coke and low-sulfur coke (<1.5wt%). Its quality is mainly affected by factors such as crude oil quality and subsequent residual oil coking process. Low-sulfur coke is generally used to prepare graphite electrodes and graphite negative electrodes for lithium-ion batteries; medium-sulfur coke is often used to prepare prebaked anodes in aluminum electrolysis; high-sulfur coke is mostly used for fuel combustion in chemical plants. At present, the proportion of high-sulfur petroleum coke is increasing, and the resources of low-sulfur petroleum coke are tight. Direct use of high-sulfur petroleum coke will not only cause serious corrosion to the equipment, but also be accompanied by the emission of SO2 gas, polluting the atmospheric environment, thus limiting the utilization of high-sulfur coke. At present, S in high-sulfur petroleum coke mainly exists in organic sulfur and inorganic sulfur. Most of the sulfur in petroleum coke is attached to the surface in the form of sulfide, and a small amount of sulfur exists in the form of organic matter, connected to the carbon ring, and the structures formed are mainly divided into four categories: mercaptan, sulfide, disulfide and thiophene. Among them, CS / C=S, which exists stably in the form of organic sulfur, is difficult to remove, while inorganic sulfur can be discharged in the form of H2S gas at a certain temperature.

[0003] The desulfurization processes mainly include: high-temperature calcination desulfurization, oxidation desulfurization, metal compound desulfurization, medium gas desulfurization, etc. The temperature in calcination desulfurization is required to be above 1250℃ before desulfurization begins. The oxidation method is to mix the oxidant with high-sulfur petroleum coke, and under certain experimental conditions, reduce and remove the S in the petroleum coke. Metal compound desulfurization is to introduce metal compounds such as NaOH, KOH, FeCl3 into high-sulfur petroleum coke, and desulfurize the high-sulfur petroleum coke at a certain temperature and pressure. Medium gas desulfurization is to introduce medium gas (H2, O2 or N2, etc.) to react with S during the heating process of high-sulfur petroleum coke to achieve desulfurization.

[0004] Prior art CN2024100342055 discloses a desulfurization method for high-sulfur petroleum coke. The high-sulfur petroleum coke is crushed, and sodium carbonate powder is added thereto for mechanical ball milling (360-720r / min) to obtain a petroleum coke alkali agent mixture; the petroleum coke alkali agent mixture is placed in a high-temperature desulfurization reactor, an inert atmosphere is introduced to exclude air, and finally methane gas is introduced to heat to 700-1000°C, and the temperature is kept for 60-150min, and then the temperature is lowered, washed and dried, and finally low-sulfur high-carbon petroleum coke is obtained, and the desulfurization rate reaches 75.37%. However, the prior art requires the use of alkaline chemical reagents, which brings problems to subsequent sewage treatment. At the same time, the operating process temperature is high (700-1000°C), and the energy consumption is large; the presence of methane gas during the reaction process will also increase safety hazards.

[0005] Prior art 2020102561699 discloses a method for electrochemical desulfurization of petroleum coke, wherein the petroleum coke is crushed to less than 1 cm; the foamed nickel and tin oxide wrapped in the petroleum coke are used as the anode and cathode respectively, and electrolysis is performed in CaCl2 salt at 900°C under argon protection for 8 hours, and the desulfurization rate of the petroleum coke after electrolysis is measured to be 83.2%. However, this prior art needs to be carried out at a relatively high temperature, and the desulfurization effect will decrease as the temperature decreases, and the operation process will increase energy consumption. Summary of the invention

[0006] The purpose of the present invention is to provide a low-temperature petroleum coke electrochemical desulfurization method.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A petroleum coke electrochemical desulfurization method comprises the following steps:

[0009] S1. Mix petroleum coke and electrolytic solution at a solid-liquid ratio of 1 g:1-9.5 mL to obtain a slurry;

[0010] S2, using graphite as anode and cathode, electrolyzing the slurry at 5-80°C for 4-20h, purifying it, and obtaining desulfurized petroleum coke;

[0011] The electrolytic solution includes a bromide salt and an acetate salt.

[0012] Graphite plates have strong conductivity, are resistant to acids and alkalis, and are not easily introduced with impurities, so they are suitable as anodes and cathodes.

[0013] In one preferred embodiment, the petroleum coke is crushed into fine coke powder and then mixed with the electrolytic solution.

[0014] In a preferred embodiment, the particle size of the fine coke powder is less than 100 μm.

[0015] Too large a particle size is not conducive to the dispersion of petroleum coke in the solution, thus 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 a preferred embodiment, the acetate is at least one of sodium acetate and potassium acetate.

[0018] In one preferred embodiment, the bromide salt and the acetate salt are uniformly mixed 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 salt to acetate is too small, the desulfurization effect will be poor; if the ratio is too large, the desulfurization effect will not change much, but the reagent cost will increase significantly.

[0020] In one preferred embodiment, the bromide salt and the acetate salt are mixed by mechanical grinding and / or impregnation.

[0021] In one preferred embodiment, in the electrolytic solution, the solid-to-liquid ratio of solute to solvent is 1 g:4-20 ml, preferably 1 g:4-12 ml.

[0022] The solutes are bromide and acetate.

[0023] In one preferred embodiment, in the electrolytic solution, the solvent is water.

[0024] In one preferred embodiment, the solid-to-liquid ratio of petroleum coke to electrolytic solution is 1 g:4.5-9.5 mL.

[0025] Too low a solid-liquid ratio increases the desulfurization cost, while too high a solid-liquid ratio reduces the desulfurization effect.

[0026] In a preferred embodiment, the electrolysis current is 0.1-7A, preferably 3-7A.

[0027] Too small a current will result in low desulfurization effect, while too high a current will increase the desulfurization cost and the desulfurization effect will not increase significantly.

[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, stirring is performed at a rotation speed of 1000-1500 r / min, preferably 1000-1300 r / min during electrolysis.

[0031] In a preferred embodiment, the purification comprises washing the product with water, separating the solid from the liquid, and drying the product.

[0032] In a preferred embodiment, the solid-liquid separation is suction filtration.

[0033] The present invention will be further explained below:

[0034] The present invention prepares a specific electrolytic solution by uniformly mixing bromide salt, acetate and aqueous solution, and electrolytically desulfurizes the slurry mixed with high-sulfur petroleum coke and the electrolytic solution, and finally obtains a low-sulfur petroleum coke product. The principle of removing sulfur elements from high-sulfur petroleum coke in the present invention is: sulfur in petroleum coke usually exists in the form of sulfide, thiophene, thioether, etc., especially thiophene structure. Since sulfur and carbon in its molecular structure are combined 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, and their structure can only be destroyed under high temperature, specific catalysts or strong oxidation conditions. In order to completely remove sulfur elements from petroleum coke, a high temperature of more than 1600°C is usually required. Therefore, ordinary desulfurization methods cannot achieve a good desulfurization effect. By applying an external voltage, a current is passed through the electrolytic cell, thereby generating an oxidizing environment. During the electrolysis process, the added electrolyte can not only increase the conductivity of the solution, but also produce strong oxidizing substances (such as oxygen, ozone, hydroxyl radicals, etc.) through electrochemical reactions. These oxidants have strong oxidizing ability. When petroleum coke comes into contact with these substances, its sulfide bonds can be destroyed, and the sulfur element can be oxidized into soluble sulfate or other oxygen-containing sulfur compounds, so that sulfur is gradually removed from the petroleum coke. The desulfurization effect is improved by changing the electrolysis conditions (current, time, temperature). The present invention provides a method for electrochemical high-efficiency deep desulfurization of high-sulfur petroleum coke. The invention not only has high desulfurization efficiency, but also has a green and clean process, can greatly reduce production costs, and increases the application value of high-sulfur petroleum coke.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The equipment requirements of the present invention are simple, the process conditions are mild, the temperature is low, and the energy consumption is greatly reduced.

[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 retaining the physical and chemical properties of petroleum coke.

[0038] (3) The present invention does not generate harmful gases, and the desulfurization products are mostly water-soluble sulfate or sulfite, which is easy to collect and treat, and has good environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1These are SEM images of the high-sulfur petroleum coke raw material in Example 1; (a) 100 times; (b) 1000 times; (c) 5000 times;

[0040] Figure 2 These are SEM images of high-sulfur petroleum coke after electrolysis in Example 1; (a) 100 times; (b) 1000 times; (c) 5000 times;

[0041] Figure 3 These are the XRD patterns of high-sulfur petroleum coke before and after electrolysis in Example 1; (a) raw material; (b) petroleum coke after desulfurization. DETAILED DESCRIPTION

[0042] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0043] Example 1

[0044] Take 5g of high-sulfur petroleum coke from a domestic factory, of which the fixed carbon content is 83.37wt.%, the volatile matter is 12.2wt.%, the ash content is 0.2wt.%, and the sulfur content is 6.52wt.%. It is crushed to less than 75μm (200 mesh) to obtain fine powder coke. The pressed graphite plate is used as the cathode and anode materials. Sodium bromide and sodium acetate are mixed evenly by mechanical grinding in a ratio of 1:5 (g:g). The mixed salt and aqueous solution are stirred evenly in a ratio of 1:12 (g:ml) to obtain an electrolytic solution. The fine powder coke and the electrolytic solution are mixed evenly in a ratio of 1:4.5 (g:ml). Electrolysis is carried out under the condition of insulation at 45℃, the electrolytic cell current is set to 3A, the electrolysis time is 8h, and the stirring speed is 1100r / min. The electrolyzed petroleum coke is washed, filtered and dried with water for many times. The sulfur content of the electrolyzed petroleum coke is measured to be 0.59wt.%, and the desulfurization rate is 91%. The XRD spectra 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 no other impurity elements have been introduced into the structure of the petroleum coke after electrolysis.

[0045] Example 2

[0046] Take 5g of high-sulfur petroleum coke from a domestic factory, of which the fixed carbon content is 83.37wt.%, the volatile matter is 12.2wt.%, the ash content is 0.2wt.%, and the sulfur content is 6.52wt.%. It is crushed to less than 75μm (200 mesh) to obtain fine powder coke. The pressed graphite plate is used as the cathode and anode materials. Sodium bromide and potassium acetate are mixed evenly by mechanical grinding in a ratio of 1:6 (g:g). The mixed salt and aqueous solution are stirred evenly in a ratio of 1:12 (g:ml) to obtain an electrolytic solution. The fine powder coke and the electrolytic solution are mixed evenly in a ratio of 1:4.5 (g:ml). Electrolysis is carried out under the insulation condition of 45℃, the electrolytic cell current is set to 3A, the electrolysis time is 8h, and the stirring speed is 1100r / min. The electrolyzed petroleum coke is washed, filtered and dried with water for many times. The sulfur content of the electrolyzed petroleum coke is measured to be 0.88wt.%, and the desulfurization rate is 86.5%.

[0047] Comparative Example 1

[0048] Replacement of sodium acetate

[0049] Take 5g of high-sulfur petroleum coke from a domestic factory, of which the fixed carbon content is 83.37wt.%, the volatile matter is 12.2wt.%, the ash content is 0.2wt.%, and the sulfur content is 6.52wt.%. It is crushed to less than 75μm (200 mesh) to obtain fine powder coke. The pressed graphite plate is used as the cathode and anode materials. Sodium bromide and ammonium acetate are mixed evenly by mechanical grinding in a ratio of 1:5 (g:g). The mixed salt and aqueous solution are stirred evenly in a ratio of 1:12 (g:ml) to obtain an electrolytic solution. The fine powder coke and the electrolytic solution are mixed evenly in a ratio of 1:4.5 (g:ml). Electrolysis is carried out under the insulation condition of 45℃, the electrolytic cell current is set to 3A, the electrolysis time is 8h, and the stirring speed is 1100r / min. The electrolyzed petroleum coke is washed with water several times and dried. The sulfur content of the electrolyzed petroleum coke is measured to be 5.27wt.%, and the desulfurization rate is 19.17%.

[0050] Comparative Example 2

[0051] No electrolyte solution

[0052] Take 5g of high-sulfur petroleum coke from a domestic factory, of which the fixed carbon content is 83.37wt.%, the volatile matter is 12.2wt.%, the ash content is 0.2wt.%, and the sulfur content is 6.52wt.%. It is crushed to less than 75μm (200 mesh) to obtain fine powder coke. The pressed graphite plate is used as the cathode and anode material. The fine powder coke and the aqueous solution are mixed evenly in a ratio of 1:4.5 (g:ml). Electrolysis is carried out under insulation conditions of 45°C, the electrolytic cell current is set to 3A, the electrolysis time is 8h, and the stirring speed is 1100r / min. The electrolyzed petroleum coke is washed with water several times and dried. The sulfur content of the electrolyzed petroleum coke is measured to be 6.38wt.%, and the desulfurization rate is 2.15%.

[0053] Comparative Example 3

[0054] Only acetate

[0055] Take 5g of high-sulfur petroleum coke from a domestic factory, of which the fixed carbon content is 83.37wt.%, the volatile matter is 12.2wt.%, the ash content is 0.2wt.%, and the sulfur content is 6.52wt.%. It is crushed to less than 75um (200 mesh) to obtain fine powder coke. The pressed graphite plate is used as the cathode and anode material. Sodium acetate and aqueous solution are stirred evenly in a ratio of 1:12 (g:ml) to obtain an electrolytic solution, and the fine powder coke and the electrolytic solution are mixed evenly in a ratio of 1:4.5 (g:ml). Electrolysis is carried out under insulation conditions of 45°C, the electrolytic cell current is set to 3A, the electrolysis time is 8h, and the stirring speed is 1100r / min. The electrolyzed petroleum coke is washed with water several times and dried. The sulfur content of the electrolyzed petroleum coke is measured to be 6.11wt.%, and the desulfurization rate is 6.29%.

[0056] Comparative Example 4

[0057] Only bromide salt

[0058] Take 5g of high-sulfur petroleum coke from a domestic factory, of which the fixed carbon content is 83.37wt.%, the volatile matter is 12.2wt.%, the ash content is 0.2wt.%, and the sulfur content is 6.52wt.%. It is crushed to less than 75um (200 mesh) to obtain fine powder coke. The pressed graphite plate is used as the cathode and anode material. Sodium bromide and aqueous solution are stirred evenly in a ratio of 1:12 (g:ml) to obtain an electrolytic solution, and the fine powder coke and the electrolytic solution are mixed evenly in a ratio of 1:4.5 (g:ml). Electrolysis is carried out under insulation conditions of 45°C, the electrolytic cell current is set to 3A, the electrolysis time is 8h, and the stirring speed is 1100r / min. The electrolyzed petroleum coke is washed with water several times and dried. The sulfur content of the electrolyzed petroleum coke is measured to be 5.95wt.%, and the desulfurization rate is 8.74%.

[0059] Example 2

[0060] Example 1 was repeated, except that sodium bromide and sodium acetate were mixed uniformly by mechanical grinding in a ratio of 1:0.5, 1:1, 1:3, 1:5, 1:7, and 1:15 (g:g), respectively. Other conditions were the same as those in Example 1, and the results after desulfurization were shown in the following table.

[0061] Table 1 Effect of different ratios of sodium bromide and sodium acetate on desulfurization effect

[0062]

[0063] The more sodium bromide is added, the more difficult it is to remove the sulfur element in the high-sulfur petroleum coke, which is not conducive 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 in a ratio of 1:4, 1:8, 1:12, 1:16, and 1:20 (g:ml) to obtain an electrolytic solution. Other conditions were the same as those in Example 1, and the results after desulfurization were shown in the following table.

[0066] Table 2 Effect of different mixed salt and aqueous solution solid-liquid ratio on desulfurization effect

[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 a ratio of 1:1, 1:2, 1:7, and 1:9.5 (g:ml). Other conditions were the same as Example 1, and the results after desulfurization were shown in the following table.

[0071] Table 3 Effect of different ratios of fine coke to electrolytic solution on desulfurization effect

[0072]

[0073] Example 5

[0074] Repeat Example 1, except that the electrolytic cell current is set to 1, 3, 5, and 7 A respectively.

[0075] Table 4 Effect of different currents on desulfurization effect

[0076] Current / A 1 3 5 7 Desulfurization rate / % 77.46 91 92.03 92.85

[0077] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications 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: The following steps are involved: S1. Mix petroleum coke and electrolytic solution at a solid-liquid ratio of 1 g:1-9.5 mL to obtain a slurry; S2, using graphite as anode and cathode, electrolyzing the slurry at 5-80°C for 4-20h, purifying it, and obtaining desulfurized petroleum coke; The electrolytic solution includes a bromide salt and an acetate salt.

2. The petroleum coke electrochemical desulfurization method according to claim 1, characterized in that: The bromide salt is at least one of calcium bromide, lithium bromide, silver bromide and magnesium bromide; the acetate salt is at least one of sodium acetate and potassium acetate.

3. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that: The bromide salt and the acetate salt are mixed evenly in a mass ratio of 1:(0.5-15).

4. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that: In the electrolytic solution, the solid-liquid ratio of solute to solvent is 1g:4-20 ml.

5. 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:4.5-9.5 mL.

6. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that: The electrolysis current is 0.1-7A.

7. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that: Electrolysis temperature 10-70°C; electrolysis time 7-14h.

8. The method for electrochemical desulfurization of petroleum coke according to claim 1, characterized in that: During electrolysis, stirring is performed at a speed of 1000-1500 r / min.

9. The method for electrochemical desulfurization of petroleum coke according to any one of claims 1 to 8, characterized in that: The product is purified by washing with water, separating the solid from the liquid, and drying.

10. The method for electrochemical desulfurization of petroleum coke according to claim 9, characterized in that: The solid-liquid separation is suction filtration.

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