Hydrophobically modified low-rank coal, and preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHAANXI UNIV OF SCI & TECH
- Filing Date
- 2022-11-29
- Publication Date
- 2026-06-26
AI Technical Summary
Low-rank coal has many oxygen-containing functional groups and large pores on its surface, resulting in high viscosity and low slurry concentration in the prepared coal-water slurry. Existing thermal modification and surface modification methods are costly and do not provide stable hydrophobicity.
After esterification with low-rank coal by 4-vinylbenzoic acid, it is then subjected to free radical polymerization with perfluoroacrylate to form a covalently bonded hydrophobic modification, thereby enhancing the hydrophobicity of low-rank coal.
It improves the hydrophobicity and coalification degree of low-rank coal, enhances the pulping performance, and the hydrophobic chains are firmly bonded to the surface of low-rank coal and are not easy to fall off.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of low-rank coal surface modification technology, specifically relating to a hydrophobically modified low-rank coal, its preparation method, and its application. Background Technology
[0002] Coal-water slurry is a high-concentration coal-water suspension that can be directly burned or used as a feedstock for coal gasification. It boasts advantages such as low pollution, high efficiency, and pipeline transportability, and is considered a crucial component of clean coal technology. An ideal coal-water slurry should possess low viscosity, high concentration, and good fluidity and stability. Coal quality is the decisive factor affecting the performance of coal-water slurry. High-grade bituminous coal produces better slurry, but it is more expensive and has limited reserves. Low-rank coal has abundant reserves and features low ash, low sulfur, high reactivity, and low cost, making it a major type of gasification coal. Using low-rank coal to prepare coal-water slurry is of significant practical importance for promoting the efficient utilization of low-rank coal and ensuring the development of coal gasification.
[0003] However, due to the low degree of coalification of low-rank coal, its surface contains a large number of hydrophilic oxygen-containing functional groups (carboxyl groups, hydroxyl groups, etc.), which easily form hydrogen bonds with adjacent water molecules. It also has a rich porous structure, resulting in poor pulping performance. Therefore, it needs to be upgraded to improve its pulping properties. Currently, thermal modification and surface modification can be used to upgrade low-rank coal. Thermal modification uses heating or adsorption methods to upgrade low-rank coal, increasing its surface hydrophobicity and degree of coalification, thereby increasing the pulping concentration. However, thermal modification usually requires additional equipment and consumes a large amount of energy, leading to high costs for industrial applications. Surface modification uses surfactants or other hydrophobic materials (diesel, asphalt, molasses, etc.) to adsorb onto the surface and pores of low-rank coal through electrostatic and hydrophobic interactions, forming a hydrophobic film that enhances the hydrophobicity and degree of coalification of low-rank coal. However, the interaction between surfactants and other hydrophobic materials and the coal surface is non-covalent, resulting in weak bonding and easy desorption under shearing, which is detrimental to subsequent pulping. Therefore, in order to improve the pulping performance of low-rank coal, it is urgent to develop other hydrophobic modification methods with stronger binding capacity. Summary of the Invention
[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a hydrophobically modified low-rank coal, its preparation method and application, and to solve the problem of high viscosity and low slurry concentration in the prepared coal-water slurry caused by the large number of oxygen-containing functional groups and large pores on the surface of low-rank coal through chemical modification.
[0005] To achieve the above objectives, the present invention employs the following technical solution:
[0006] This invention provides a method for preparing hydrophobically modified low-rank coal, comprising the following steps:
[0007] S1: Low-rank coal, 4-vinylbenzoic acid, catalyst and DMF are mixed evenly and subjected to esterification reaction. After the esterification reaction is completed, the mixture is filtered, washed and dried to obtain intermediate product I.
[0008] S2: Mix intermediate product I, hydrophobic modifier and DMF evenly, then add initiator and sonicate to carry out free radical polymerization reaction. After the free radical polymerization reaction is completed, filter, wash and dry to obtain hydrophobic modified low-rank coal.
[0009] In a further step of the present invention, in S1, the low-rank coal is one or more of lignite, long-flame coal, non-caking coal, and sub-bituminous coal; the catalyst is one or more of concentrated sulfuric acid, phosphoric acid, and benzenesulfonic acid.
[0010] In a further step of the present invention, in step S1, the mass ratio of the low-rank coal, 4-vinylbenzoic acid and DMF is 1:(0.5-1):(10-15); the mass of the catalyst is 2-8% of the sum of the masses of the low-rank coal and 4-vinylbenzoic acid.
[0011] In a further embodiment of the present invention, in S1, the reaction temperature of the esterification reaction is 60-70°C, and the reaction time of the esterification reaction is 5-7 hours.
[0012] In a further step of the present invention, in step S2, the hydrophobic modifier is one or more of perfluorodecyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, and 2-(perfluorohexyl)ethyl methacrylate; and the initiator is azobisisobutyronitrile.
[0013] In a further step of the present invention, in step S2, the mass ratio of the intermediate product I, the hydrophobic modifier, and DMF is 1:(0.8-1.2):(8-12); the mass of the initiator is 0.5-0.8% of the sum of the masses of the intermediate product I and the hydrophobic modifier.
[0014] In a further embodiment of the present invention, in S2, the reaction temperature of the free radical polymerization reaction is 75-85°C, and the reaction time of the free radical polymerization reaction is 24-36h.
[0015] This invention provides a method for preparing hydrophobically modified low-rank coal according to any one of the claims, resulting in hydrophobically modified low-rank coal.
[0016] The hydrophobic modified low-rank coal described in this invention is used in the preparation of coal-water slurry.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] This invention discloses a method for preparing hydrophobically modified low-rank coal. First, the hydroxyl groups on the surface of the low-rank coal undergo an esterification reaction with the carboxyl groups of 4-vinylbenzoic acid. Then, it is further polymerized with perfluoroacrylate via double bond polymerization to obtain hydrophobically modified low-rank coal. The esterification reaction between 4-vinylbenzoic acid and low-rank coal reduces the hydroxyl groups that affect the slurry-forming properties of the low-rank coal, while introducing double bonds to the surface of the low-rank coal. Subsequently, hydrophobic fluorocarbon chains are covalently grafted onto the surface of the low-rank coal through free radical polymerization, enhancing the hydrophobicity of the low-rank coal. Furthermore, the fluorocarbon chains reduce the entry of water into the pores, improving slurry-forming properties. Compared with other surface modification methods, the hydrophobic chains are firmly bonded to the surface of the low-rank coal and do not detach. The degree of coalification of the hydrophobically modified low-rank coal is improved, which is beneficial for improving the slurry-forming properties of the modified low-rank coal. Attached Figure Description
[0019] Figure 1 This is a diagram illustrating the preparation reaction mechanism of Example 1 of the present invention;
[0020] Figure 2 This is a comparison diagram of the water contact angle between the hydrophobically modified lignite obtained in Example 1 of the present invention and the original lignite. Detailed Implementation
[0021] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.
[0022] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.
[0023] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values (including integers and fractions) within those ranges.
[0024] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”
[0025] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.
[0026] This invention provides a hydrophobically modified low-rank coal, its preparation method, and its application.
[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0028] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.
[0029] This invention discloses a method for preparing hydrophobically modified low-rank coal, comprising the following steps:
[0030] S1: Low-rank coal, 4-vinylbenzoic acid, catalyst and DMF are added to a three-necked flask, mixed evenly, and stirred at 60-70°C for 5-7 hours. The reaction is an esterification reaction. After the reaction is completed, the mixture is filtered, washed with DMF and distilled water, and dried to obtain intermediate product I.
[0031] S2: Add intermediate product I, hydrophobic modifier and DMF to a three-necked flask, mix well, add initiator, sonicate for 1 hour, stir at 75-85℃ for 24-36 hours. The reaction is a free radical polymerization reaction. After filtration, washing with DMF and distilled water, and drying, hydrophobic modified low-rank coal is obtained.
[0032] Further, in S1, the low-rank coal is one or more of lignite, long-flame coal, non-caking coal, and sub-bituminous coal; the catalyst is one or more of concentrated sulfuric acid, phosphoric acid, and benzenesulfonic acid; the mass ratio of low-rank coal to 4-vinylbenzoic acid is 1:(0.5-1); the mass of the catalyst is 2-8% of the sum of the masses of low-rank coal and 4-vinylbenzoic acid; and the mass of DMF is 10-15 times that of low-rank coal.
[0033] Further, in S2, the hydrophobic modifier is one or more of perfluorodecyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, and 2-(perfluorohexyl)ethyl methacrylate; the initiator is azobisisobutyronitrile; the mass ratio of intermediate product I to hydrophobic modifier is 1:(0.8-1.2); the mass of initiator is 0.5-0.8% of the sum of the masses of intermediate product I and hydrophobic modifier; and the mass of DMF is 8-12 times that of intermediate product I.
[0034] The hydrophobically modified low-rank coal prepared by this invention is mainly used to prepare coal-water slurry and increase the slurry concentration of low-rank coal.
[0035] Example 1
[0036] S1: Add 10g of lignite, 5g of 4-vinylbenzoic acid, 0.3g of concentrated sulfuric acid and 100mL of DMF to a three-necked flask, mix well, stir and react at 60℃ for 5h, filter, wash with DMF and distilled water, and dry to obtain intermediate product I;
[0037] S2: Add 10g of intermediate product I, 8g of perfluorodecyl acrylate and 80mL of DMF to a three-necked flask, mix well, add 0.09g of azobisisobutyronitrile, sonicate for 1h, stir at 75℃ for 24h, filter, wash with DMF and distilled water, and dry to obtain hydrophobically modified lignite.
[0038] Example 2
[0039] S1: Add 10g of lignite, 6g of 4-vinylbenzoic acid, 0.48g of concentrated sulfuric acid and 110mL of DMF to a three-necked flask, mix well, stir and react at 60℃ for 5h, filter, wash with DMF and distilled water, and dry to obtain intermediate product I.
[0040] S2: Add 10g of intermediate product I, 9g of perfluorodecyl acrylate and 90mL of DMF to a three-necked flask, mix well, add 0.114g of azobisisobutyronitrile, sonicate for 1h, stir at 75℃ for 28h, filter, wash with DMF and distilled water, and dry to obtain hydrophobically modified lignite.
[0041] Example 3
[0042] S1: Add 10g of long-flame coal, 7g of 4-vinylbenzoic acid, 0.68g of benzenesulfonic acid and 120mL of DMF to a three-necked flask, mix well, stir and react at 65℃ for 6h, filter, wash with DMF and distilled water, and dry to obtain intermediate product I.
[0043] S2: Add 10g of intermediate product I, 10g of 2-(perfluorooctyl)ethyl methacrylate, and 100mL of DMF to a three-necked flask, mix well, and add 0.14...g Azobisisobutyronitrile (AIBN) was ultrasonicated for 1 hour, stirred at 80°C for 30 hours, filtered, washed with DMF and distilled water, and dried to obtain hydrophobically modified long-flame coal.
[0044] Example 4
[0045] S1: Add 10g of non-sticky coal, 8g of 4-vinylbenzoic acid, 1.08g of benzenesulfonic acid and 130mL of DMF to a three-necked flask, mix well, stir and react at 65℃ for 6h, filter, wash with DMF and distilled water, and dry to obtain intermediate product I.
[0046] S2: Add 10g of intermediate product I, 10g of 2-(perfluorooctyl)ethyl methacrylate, and 100mL of DMF to a three-necked flask, mix well, and add 0.14... g Azobisisobutyronitrile (AIBN) was ultrasonicated for 1 hour, stirred at 80°C for 30 hours, filtered, washed with DMF and distilled water, and dried to obtain hydrophobically modified non-caking coal.
[0047] Example 5
[0048] S1: Add 10g of bituminous coal, 9g of 4-vinylbenzoic acid, 1.33g of phosphoric acid and 140mL of DMF to a three-necked flask, mix well, stir and react at 70℃ for 7h, filter, wash with DMF and distilled water, and dry to obtain intermediate product I;
[0049] S2: 10g of intermediate product I, 11g of 2-(perfluorohexyl)ethyl methacrylate and 110mL of DMF were added to a three-necked flask and mixed evenly. 0.088g of azobisisobutyronitrile was added, and the mixture was sonicated for 1h and stirred at 85℃ for 34h. The mixture was then filtered, washed with DMF and distilled water, and dried to obtain hydrophobically modified bituminous coal.
[0050] Example 6
[0051] S1: Add 10g of bituminous coal, 10g of 4-vinylbenzoic acid, 1.6g of phosphoric acid and 150mL of DMF to a three-necked flask, mix well, stir and react at 70℃ for 7h, filter, wash with DMF and distilled water, and dry to obtain intermediate product I.
[0052] S2: 10g of intermediate product I, 12g of 2-(perfluorohexyl)ethyl methacrylate and 120mL of DMF were added to a three-necked flask and mixed evenly. 0.176g of azobisisobutyronitrile was added, and the mixture was sonicated for 1h. The mixture was stirred at 85℃ for 36h, filtered, washed with DMF and distilled water, and dried to obtain hydrophobically modified bituminous coal.
[0053] Application effect test:
[0054] Contact angle:
[0055] 0.5g of raw lignite powder and hydrophobically modified lignite powder (Example 1) were pressed into cylindrical tablets with a diameter of approximately 10mm and a thickness of approximately 2mm using a tablet press. Then, distilled water was dropped onto the coal tablets using a micro-syringe. The shape of the droplets on the coal tablets was observed and photographed using a JC2000D2G contact angle meter, and the contact angle was calculated. The test results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the contact angle of distilled water on raw lignite is 65.5°, exhibiting strong hydrophilicity. After hydrophobic modification, the contact angle increases to 100.5°, and the hydrophobicity of the coal surface is significantly improved.
[0056] Preparation and performance testing of coal-water slurry:
[0057] Naphthalenesulfonic acid formaldehyde condensate was used as a dispersant in the slurry preparation, with a fixed addition amount of 0.8% of the coal-based mass. The naphthalenesulfonic acid formaldehyde condensate was stirred evenly with distilled water in a beaker, and then ground coal particles were slowly added at a stirring speed of 1200 r / min. After all the coal particles were added, stirring was continued for 5 min until the coal-water mixture became a homogeneous and stable slurry.
[0058] The apparent viscosity of coal-water slurry was tested using the method specified in GB / T18856.4-2008, employing an SMJ-1 type coal-water slurry apparent viscosity meter manufactured by Shanghai Nirun Intelligent Technology Co., Ltd. (shear rate 100 s). -1 The maximum pulping concentration was determined by the pulp concentration at an apparent viscosity of 1000 mPa·s.
[0059] At room temperature, pour the prepared coal-water slurry into a beaker, let it stand for 5 minutes, and then slowly pour the coal-water slurry into another container. Visually inspect the flow pattern of the slurry and classify it into four technical index grades: A, B, C, and D. The corresponding judgment criteria are: linear fluid, thick liquid with slightly poor flowability, viscous liquid with poor flowability, and no slurry.
[0060] The slurry was sealed and placed in a 100mL graduated cylinder. The breakthrough rate and the presence of sediment were measured after 3 days. Generally, the higher the breakthrough rate of the slurry, the better its stability.
[0061] Table 1 compares the performance of coal-water slurry prepared from the original coal sample and the hydrophobically modified coal sample. As shown in the table, the slurry-making performance of low-rank coal is significantly improved after hydrophobic modification. The maximum slurry concentration of the original lignite was 56.23%, the flow pattern was D, and the breakthrough rate after 3 days was 70.11%, with slight hard sedimentation. After hydrophobic modification, the maximum slurry concentration of the coal-water slurry prepared in Example 1 increased to 65.72%, the flow pattern was B, and the breakthrough rate after 3 days was 79.68%, with only slight soft sedimentation.
[0062] Table 1 Comparison of the properties of coal-water slurry prepared from the original coal sample and the hydrophobically modified coal sample.
[0063]
[0064] The principle of this invention is that the esterification reaction between 4-vinylbenzoic acid and low-rank coal reduces the hydroxyl groups that affect the slurry-forming properties of low-rank coal, while introducing double bonds to the surface of the low-rank coal. Through free radical polymerization, hydrophobic fluorocarbon chains are covalently grafted onto the surface of the low-rank coal, enhancing its hydrophobicity. Compared with other surface modification methods, the hydrophobic chains are firmly bonded to the surface of low-rank coal and will not detach. The degree of coalification of the hydrophobically modified low-rank coal is improved, which is beneficial to improving the slurry-forming properties of the modified low-rank coal.
[0065] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A method for preparing hydrophobically modified low-rank coal, characterized in that, Includes the following steps: S1: Low-rank coal, 4-vinylbenzoic acid, catalyst and DMF are mixed evenly and subjected to esterification reaction. After the esterification reaction is completed, the mixture is filtered, washed and dried to obtain intermediate product I; the mass ratio of low-rank coal, 4-vinylbenzoic acid and DMF is 1:(0.5~1):(10~15). S2: Mix intermediate product I, hydrophobic modifier, and DMF evenly, then add initiator and sonicate to carry out free radical polymerization reaction. After the free radical polymerization reaction is completed, filter, wash, and dry to obtain hydrophobic modified low-rank coal; the mass ratio of intermediate product I, hydrophobic modifier, and DMF is 1:(0.8~1.2):(8~12); the mass of initiator is 0.5~0.8% of the sum of the mass of intermediate product I and hydrophobic modifier; the hydrophobic modifier is one or more of perfluorodecyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, and 2-(perfluorohexyl)ethyl methacrylate.
2. The method for preparing hydrophobically modified low-rank coal according to claim 1, characterized in that, In S1, the low-rank coal is one or more of lignite, long-flame coal, non-caking coal, and sub-bituminous coal; the catalyst is one or more of concentrated sulfuric acid, phosphoric acid, and benzenesulfonic acid.
3. The method for preparing hydrophobically modified low-rank coal according to claim 1, characterized in that, In S1, the mass of the catalyst is 2 to 8% of the sum of the masses of low-rank coal and 4-vinylbenzoic acid.
4. The method for preparing hydrophobically modified low-rank coal according to claim 1, characterized in that, In S1, the esterification reaction temperature is 60~70℃ and the esterification reaction time is 5~7 h.
5. The method for preparing hydrophobically modified low-rank coal according to claim 1, characterized in that, In S2, the initiator is azobisisobutyronitrile.
6. The method for preparing hydrophobically modified low-rank coal according to claim 1, characterized in that, In S2, the reaction temperature of the free radical polymerization reaction is 75~85℃, and the reaction time of the free radical polymerization reaction is 24~36 h.
7. A hydrophobically modified low-rank coal prepared by the method for preparing hydrophobically modified low-rank coal according to any one of claims 1 to 6.
8. The application of hydrophobically modified low-rank coal according to claim 7, characterized in that, The hydrophobically modified low-rank coal is used in the preparation of coal-water slurry.