A method for promoting the rapid oxidation of asphalt by cyclic extraction with a deep eutectic solvent

Abstract

The object of the present invention is to provide a method for promoting the rapid oxidation of pitch by eutectic solvent circulation extraction, belonging to the technical field of the preparation of pitch-based carbon materials. First, place the preformed workpiece of pitch-based carbon material in the extraction tower, and control the continuous inflow and outflow of the eutectic solvent through valves to ensure that the workpiece is always immersed below the liquid level. The extracted liquid flowing out enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out to complete the regeneration of the eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After cyclic extraction at a certain temperature and time, take out the desolvated preformed workpiece of pitch-based carbon material from the extraction tower. Place the desolvated preformed workpiece of pitch-based carbon material in an oxidation furnace for oxidation operation. The present invention uses eutectic solvents, which are green, environmentally friendly and pollution-free, and have the characteristics of simple operation and low cost, solving the problem that it is difficult to oxidize the preformed workpiece of pitch-based carbon materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of pitch-based carbon materials, and particularly relates to a method for promoting the rapid oxidation of pitch by low eutectic solvent circulation extraction. Background Art

[0002] Oxidation is a key process for the shaping and curing of pitch-based carbon materials and determines their properties. Air blowing is the most commonly used method for pitch oxidation, and its oxidation temperature is usually between 200 and 350 °C. Therefore, pitch molecules have a high aromaticity and few side chains, resulting in a very high activation energy for the oxidation reaction. In addition, the diffusion of oxidation in the pitch matrix is very slow. Therefore, the oxidation process usually takes a long time and consumes a lot of energy, and the uneven oxidation is extremely likely to produce a skin-core structure, significantly restricting the development of pitch-based carbon materials.

[0003] In order to shorten the pitch oxidation cycle and improve the homogeneity of the oxidation products, the commonly used pro-oxidation technologies mainly have the following two methods: (1) promoting the diffusion of gaseous oxygen in the pitch matrix; (2) adding additives during the pitch modulation process. Patent CN1156123A uses high softening point pitch with a softening point of 200-300 °C as a precursor, and by adding additives (such as sulfur elements), the reaction is promoted, thereby greatly shortening the oxidation stabilization time of the pitch product. Patent CN110317621A uses medium and low temperature pitch as a raw material, and by adding low temperature, high temperature, and mixed promoters, not only can the multi-bond synergistically and controllably promote the stabilization of medium and low temperature pitch, but also promote the high-value utilization of low-value raw materials. However, this patent has many problems: First, the process of adding and removing additives inevitably increases the equipment and process costs; second, the high softening point pitch is expensive, resulting in a significant increase in production costs; in addition, it may also cause environmental pollution.

[0004] In recent years, low eutectic solvents have been widely used as adjuvants in the process of extracting and separating pitch. Patent CN112852471A discloses a method for extracting pitch from oil sand assisted by a low eutectic solvent. The oil sand containing pitch, the low eutectic solvent, and petroleum ether are stirred at normal temperature and pressure, centrifuged, and divided into three layers. The upper layer mixture is taken and dried, so that the pitch can be cleanly separated and a high extraction rate can be obtained. The method for separating phenolic compounds in coal tar provided by Patent CN109593539A feeds the low eutectic solvent and the coal tar to be treated into a centrifugal extractor respectively, obtains de-phenolized coal tar and an extract, washes the extract, and separates it to obtain phenolic compounds. The above patents all involve the operation of extracting and separating pitch with low eutectic solvents, indicating that low eutectic solvents have the ability to dissolve the components of pitch, and all the obtained are soluble parts, and such methods have not been used for the treatment of pitch-based carbon materials. Summary of the Invention

[0005] The object of the present invention is to provide a method for promoting the rapid oxidation of pitch by eutectic solvent circulation extraction. For the first time, the present invention uses a eutectic solvent to treat the preformed workpiece of pitch-based carbon materials, forming pores on the surface or inside of the workpiece to change its structure. During the oxidation process, the diffusion of oxygen and the reaction between oxygen and the polycyclic aromatic molecules of pitch will be accelerated, enabling the rapid oxidation of the pitch workpiece and contributing to the energy conservation and consumption reduction in the preparation process of pitch-based carbon materials.

[0006] The present invention adopts the following technical solutions:

[0007] A method for promoting the rapid oxidation of pitch by eutectic solvent circulation extraction, comprising the following steps:

[0008] Place the preformed workpiece of pitch-based carbon materials in the extraction tower, and control the continuous inflow and outflow of the eutectic solvent through a valve to ensure that the workpiece is always submerged below the liquid level;

[0009] The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out to complete the regeneration of the eutectic solvent;

[0010] The regenerated eutectic solvent is mixed with the supplementary eutectic solvent and enters the extraction tower for use. After cyclic extraction, the desolvated preformed workpiece of pitch-based carbon materials is taken out from the extraction tower;

[0011] Place the desolvated preformed workpiece of pitch-based carbon materials in an oxidation furnace. Under different atmosphere conditions, heat it from room temperature to 200 - 350 °C at an oxidation heating rate of 20 - 100 °C / h, keep it at a constant temperature for 0 - 6 h, and then cool it and discharge the material to obtain the oxidized workpiece.

[0012] Further, the eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor. Among them, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor includes any one of urea, ethylene glycol, malonic acid, and phenol. The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(1 - 10), and the formation temperature is 40 - 100 °C.

[0013] Further, the preformed workpiece of pitch-based carbon materials includes one or any combination of carbon fibers, composite materials, spherical and amorphous particles.

[0014] Further, the treatment time of the cyclic extraction is 6 - 12 h.

[0015] Further, the treatment temperature of the cyclic extraction is 20 - 50 °C.

[0016] Further, in the water washing unit, the mass ratio of the eutectic solvent to water is 1:(1 - 5).

[0017] Further, the atmosphere includes any one of air or oxygen.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The reagent used for extraction in the present invention is a deep eutectic solvent, which has advantages such as high solubility, environmental friendliness, chemical tunability, simple preparation, and low cost compared with traditional oxidants.

[0020] 2. The preformed workpiece of the pitch-based carbon material is treated with a deep eutectic solvent to form pores on the surface or inside of the workpiece, thereby changing its structure. During the oxidation process, the diffusion of oxygen and the reaction between oxygen and the pitch polycyclic aromatic molecules will be accelerated, enabling the pitch workpiece to achieve rapid oxidation.

[0021] 3. The deep eutectic solvent can be recycled, which helps to save energy and reduce consumption in the preparation process of the pitch-based carbon material. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of a system for promoting rapid oxidation of pitch by circulating extraction with a deep eutectic solvent according to the present invention. Detailed Embodiments

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, specific embodiments of the present invention will be described in detail, but not limited thereto. Unless otherwise specified, the raw materials used in the embodiments are all ordinary commercially available products; unless otherwise specified, the methods used are all common methods in the art.

[0024] The promotion of rapid oxidation of pitch in the present invention is illustrated by means of oxidation time, oxidation weight gain, etc.

[0025] Example 1

[0026] First, place the pitch workpiece 1 # in the extraction tower, and control the continuous inflow and outflow of the deep eutectic solvent (molar ratio of choline chloride: urea = 1:1.5, T = 80 °C) through valves to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment (mass ratio of deep eutectic solvent: water = 1:1) are carried out to complete the regeneration of the deep eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and then enters the extraction tower for use. After 40 °C and 8 h of cyclic extraction, the preformed workpiece of the pitch-based carbon material after desolvation is taken out from the extraction tower. The preformed workpiece of the pitch-based carbon material after desolvation is placed in an oxidation furnace. Under the condition of an oxygen atmosphere, with an oxidation heating rate of 40 °C / h, it is heated from room temperature to 270 °C, kept at a constant temperature for 3 h, and then cooled and discharged to obtain the oxidized workpiece. The oxidation time is 9.75 h, and the oxidation weight gain is 7%.

[0027] Comparative Example 1

[0028] Using the same asphalt workpiece as in Example 1 as the raw material, without adding the eutectic solvent, keeping other processes unchanged, the oxidation time is 9.75 h, and the oxidation weight gain is 3.6%.

[0029] Example 2

[0030] A method for promoting rapid oxidation of asphalt by cyclic extraction of eutectic solvent, comprising the following steps:

[0031] First, place the asphalt workpiece 2 # in the extraction tower, control the continuous inflow and outflow of the eutectic solvent (choline chloride: phenol molar ratio = 1:3, T = 60 °C) through valves to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment (eutectic solvent: water mass ratio = 1:2.5) are carried out to complete the regeneration of the eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After 40 °C and 12 h of cyclic extraction, the desolvated preformed workpiece of asphalt-based carbon material is taken out from the extraction tower. The desolvated preformed workpiece of asphalt-based carbon material is placed in an oxidation furnace, and under the condition of air atmosphere, with an oxidation heating rate of 50 °C / h, it is heated from room temperature to 300 °C, held at a constant temperature for 4 h, cooled and discharged to obtain the oxidized workpiece. The oxidation time is 10 h, and the oxidation weight gain is 6.8%.

[0032] Comparative Example 2

[0033] Using the same asphalt workpiece as in Example 2 as the raw material, without adding the eutectic solvent, keeping other processes unchanged, the oxidation time is 10 h, and the oxidation weight gain is 4.1%.

[0034] Example 3

[0035] A method for promoting rapid oxidation of asphalt by cyclic extraction of eutectic solvent, comprising the following steps:

[0036] First, place the asphalt workpiece 3 # in the extraction tower, control the continuous inflow and outflow of the eutectic solvent (choline chloride: phenol molar ratio = 1:5, T = 80 °C) through valves to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment (eutectic solvent: water mass ratio = 1:3) are carried out to complete the regeneration of the eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After 30 °C and 9 h of cyclic extraction, the desolvated preformed workpiece of asphalt-based carbon material is taken out from the extraction tower. The desolvated preformed workpiece of asphalt-based carbon material is placed in an oxidation furnace, and under the condition of oxygen atmosphere, with an oxidation heating rate of 60 °C / h, it is heated from room temperature to 300 °C, held at a constant temperature for 2 h, cooled and discharged to obtain the oxidized workpiece. The oxidation time is 7 h, and the oxidation weight gain is 8.3%.

[0037] Comparative Example 3

[0038] Using the same asphalt workpiece as in Example 3 as the raw material, without adding the eutectic solvent, keeping other processes unchanged, the oxidation time is 7 h, and the oxidation weight gain is 4%.

[0039] Example 4

[0040] A method for promoting rapid oxidation of asphalt by eutectic solvent circulation extraction, comprising the following steps:

[0041] First, place the asphalt workpiece 4 # in the extraction tower, control the continuous entry and outflow of the eutectic solvent (choline chloride:ethylene glycol molar ratio = 1:1.5, T = 60 °C) through a valve to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out (eutectic solvent:water mass ratio = 1:5) to complete the regeneration of the eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and then used in the extraction tower. After 50 °C and 7 h of cyclic extraction, the desolvated preformed workpiece of asphalt-based carbon material is taken out from the extraction tower. The desolvated preformed workpiece of asphalt-based carbon material is placed in an oxidation furnace. Under an oxygen atmosphere condition, with an oxidation heating rate of 40 °C / h, it is heated from room temperature to 280 °C, kept at a constant temperature for 1 h, and then cooled and discharged to obtain the oxidized workpiece. The oxidation time is 8 h, and the oxidation weight gain is 5.5%.

[0042] Comparative Example 4

[0043] Using the same asphalt workpiece as in Example 4 as the raw material, without adding the eutectic solvent, keeping other processes unchanged, the oxidation time is 8 h, and the oxidation weight gain is 2.9%.

[0044] Example 5

[0045] A method for promoting rapid oxidation of asphalt by eutectic solvent circulation extraction, comprising the following steps:

[0046] First, place the asphalt workpiece 5 #It is placed in the extraction tower, and the continuous inflow and outflow of the deep eutectic solvent (choline chloride: malonic acid molar ratio = 1:8, T = 40 °C) are controlled by valves to ensure that the workpiece is always submerged below the liquid level. The extracted liquid flowing out enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out (deep eutectic solvent: water mass ratio = 1:4) to complete the regeneration of the deep eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After 35 °C and 10 h of cyclic extraction, the preformed workpiece of the de-solvation pitch-based carbon material is taken out from the extraction tower. The preformed workpiece of the de-solvation pitch-based carbon material is placed in an oxidation furnace. Under the condition of air atmosphere, with an oxidation heating rate of 30 °C / h, it is heated from room temperature to 270 °C, kept at a constant temperature for 2 h, and then cooled and discharged to obtain the oxidized workpiece. The oxidation time is 11 h, and the oxidation weight gain is 9%.

[0047] Comparative Example 5

[0048] Using the same pitch workpiece as in Example 5 as the raw material, without adding the deep eutectic solvent, keeping other processes unchanged, the oxidation time is 11 h, and the oxidation weight gain is 6.5%.

[0049] Example 6

[0050] A method for promoting the rapid oxidation of pitch by cyclic extraction of a deep eutectic solvent, comprising the following steps:

[0051] First, place the pitch workpiece 6 # It is placed in the extraction tower, and the continuous inflow and outflow of the deep eutectic solvent (choline chloride: malonic acid molar ratio = 1:6, T = 50 °C) are controlled by valves to ensure that the workpiece is always submerged below the liquid level. The extracted liquid flowing out enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out (deep eutectic solvent: water mass ratio = 1:4) to complete the regeneration of the deep eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After 25 °C and 9 h of cyclic extraction, the preformed workpiece of the de-solvation pitch-based carbon material is taken out from the extraction tower. The preformed workpiece of the de-solvation pitch-based carbon material is placed in an oxidation furnace. Under the condition of air atmosphere, with an oxidation heating rate of 20 °C / h, it is heated from room temperature to 200 °C, kept at a constant temperature for 0 h, and then cooled and discharged to obtain the oxidized workpiece. The oxidation time is 10 h, and the oxidation weight gain is 8.3%.

[0052] Comparative Example 6

[0053] Using the same pitch workpiece as in Example 6 as the raw material, without adding the deep eutectic solvent, keeping other processes unchanged, the oxidation time is 10 h, and the oxidation weight gain is 5.9%.

[0054] Example 7

[0055] A method for promoting the rapid oxidation of pitch by cyclic extraction of a deep eutectic solvent, comprising the following steps:

[0056] First, place the asphalt workpiece 7 # in the extraction tower. Control the continuous inflow and outflow of the deep eutectic solvent (choline chloride:phenol molar ratio = 1:6, T = 75 °C) through a valve to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out (deep eutectic solvent:water mass ratio = 1:5) to complete the regeneration of the deep eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After 20 °C and 11 h of cyclic extraction, the de-solvated preformed asphalt-based carbon material workpiece is taken out from the extraction tower. Place the de-solvated preformed asphalt-based carbon material workpiece in an oxidation furnace. Under an oxygen atmosphere condition, with an oxidation heating rate of 25 °C / h, heat up from room temperature to 260 °C, keep it at a constant temperature for 1 h, cool down and discharge to obtain the oxidized workpiece. The oxidation time is 11.4 h and the oxidation weight gain is 9.7%.

[0057] Comparative Example 7

[0058] Use the same asphalt workpiece as in Example 7 as the raw material, without adding the deep eutectic solvent, keep other processes unchanged. The oxidation time is 11.4 h and the oxidation weight gain is 7.4%.

[0059] Example 8

[0060] A method for promoting the rapid oxidation of asphalt by cyclic extraction with a deep eutectic solvent, comprising the following steps:

[0061] First, place the asphalt workpiece 8 # in the extraction tower. Control the continuous inflow and outflow of the deep eutectic solvent (choline chloride:urea molar ratio = 1:10, T = 100 °C) through a valve to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out (deep eutectic solvent:water mass ratio = 1:2) to complete the regeneration of the deep eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and enters the extraction tower for use. After 30 °C and 9 h of cyclic extraction, the de-solvated preformed asphalt-based carbon material workpiece is taken out from the extraction tower. Place the de-solvated preformed asphalt-based carbon material workpiece in an oxidation furnace. Under an oxygen atmosphere condition, with an oxidation heating rate of 40 °C / h, heat up from room temperature to 220 °C, keep it at a constant temperature for 3 h, cool down and discharge to obtain the oxidized workpiece. The oxidation time is 8.5 h and the oxidation weight gain is 6.2%.

[0062] Comparative Example 8

[0063] Use the same asphalt workpiece as in Example 8 as the raw material, without adding the deep eutectic solvent, keep other processes unchanged. The oxidation time is 8.5 h and the oxidation weight gain is 4.3%.

[0064] Example 9

[0065] A method for promoting the rapid oxidation of asphalt by eutectic solvent cyclic extraction, comprising the following steps:

[0066] First, place the asphalt workpiece 9 # in the extraction tower, and control the continuous inflow and outflow of the eutectic solvent (choline chloride:phenol molar ratio = 1:3, T = 75 °C) through a valve to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment (eutectic solvent:water mass ratio = 1:2) are carried out to complete the regeneration of the eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and then enters the extraction tower for use. After 30 °C and 9 h of cyclic extraction, the desolvated asphalt-based carbon material preformed workpiece is taken out from the extraction tower. Place the desolvated asphalt-based carbon material preformed workpiece in an oxidation furnace, under an oxygen atmosphere condition, with an oxidation heating rate of 30 °C / h, heat up from room temperature to 300 °C, keep the temperature constant for 2 h, cool down and discharge the material, and then the oxidized workpiece is obtained. The oxidation time is 12 h, and the oxidation weight gain is 8.1%.

[0067] Comparative Example 9

[0068] Using the same asphalt workpiece as in Example 9 as the raw material, without adding the eutectic solvent, keeping other processes unchanged, the oxidation time is 12 h, and the oxidation weight gain is 5.7%.

[0069] Example 10

[0070] A method for promoting the rapid oxidation of asphalt by eutectic solvent cyclic extraction, comprising the following steps:

[0071] First, place the asphalt workpiece 10 # in the extraction tower, and control the continuous inflow and outflow of the eutectic solvent (choline chloride:ethylene glycol molar ratio = 1:2, T = 40 °C) through a valve to ensure that the workpiece is always submerged below the liquid level. The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment (eutectic solvent:water mass ratio = 1:3) are carried out to complete the regeneration of the eutectic solvent. The regenerated liquid is mixed with the supplementary liquid and then enters the extraction tower for use. After 45 °C and 8 h of cyclic extraction, the desolvated asphalt-based carbon material preformed workpiece is taken out from the extraction tower. Place the desolvated asphalt-based carbon material preformed workpiece in an oxidation furnace, under an air atmosphere condition, with an oxidation heating rate of 50 °C / h, heat up from room temperature to 240 °C, keep the temperature constant for 3 h, cool down and discharge the material, and then the oxidized workpiece is obtained. The oxidation time is 7.8 h, and the oxidation weight gain is 7.7%.

[0072] Comparative Example 10

[0073] Using the same asphalt workpiece as in Example 10 as the raw material, without adding the eutectic solvent, keeping other processes unchanged, the oxidation time is 7.8 h, and the oxidation weight gain is 4.6%.

[0074] Table 1 Performance comparison results of Examples and Comparative Examples 1-10 with and without DES

[0075]

[0076] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. The above embodiments only represent several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for promoting the rapid oxidation of asphalt by eutectic solvent circulation extraction, characterized in that: It includes the following steps: Place the preformed workpiece of asphalt-based carbon material in the extraction tower, and control the continuous inflow and outflow of the deep eutectic solvent through a valve to ensure that the workpiece is always submerged below the liquid level; The outflowing extraction liquid enters the water washing unit, and then centrifugal separation and dehydration treatment are carried out to complete the regeneration of the deep eutectic solvent; The regenerated deep eutectic solvent is mixed with the supplementary deep eutectic solvent and enters the extraction tower for use. After cyclic extraction, the preformed workpiece of asphalt-based carbon material with desorbed solvent is taken out from the extraction tower; Place the preformed workpiece of asphalt-based carbon material with desorbed solvent in an oxidation furnace. Under different atmosphere conditions, with an oxidation heating rate of 20~100 °C / h, heat up from room temperature to 200~350 °C, keep the temperature constant for 0~6 h, and then cool down and discharge to obtain the oxidized workpiece; The deep eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor. Among them, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor includes any one of urea, ethylene glycol, malonic acid, and phenol. The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(1~10), and the formation temperature is 40~100 °C.

2. The method for promoting the rapid oxidation of asphalt by eutectic solvent circulation extraction according to claim 1, characterized in that: The preformed workpiece of asphalt-based carbon material includes one or any combination of carbon fiber, composite material, spherical and amorphous particles.

3. A method for promoting the rapid oxidation of asphalt by eutectic solvent cyclic extraction according to claim 1, characterized in that: The treatment time of the cyclic extraction is 6 - 12 h.

4. A method for promoting the rapid oxidation of asphalt by eutectic solvent circulation extraction according to claim 1, characterized in that: The treatment temperature of the cyclic extraction is 20 - 50 °C.

5. A method for promoting rapid oxidation of asphalt by eutectic solvent cyclic extraction according to claim 1, characterized in that: In the water washing unit, the mass ratio of the deep eutectic solvent to water is 1:(1 - 5).

6. A method for promoting the rapid oxidation of asphalt by eutectic solvent cyclic extraction according to claim 1, characterized in that: The atmosphere includes any one of air or oxygen.

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