A method for directional dissociation of sulfur compounds in fat coal

Abstract

This invention discloses a method for the targeted dissociation of sulfur-containing compounds in coking coal, belonging to the field of coal chemical technology. The method includes: crushing, drying, and flotation / sinking the coking coal to obtain light components; then acid washing, drying, and grinding the light components to obtain clean coal to be processed; adding an extractant and performing a first-stage extraction at a set temperature of 35–105°C; after the first-stage extraction, adding a free radical initiator and performing a second-stage extraction; separating the extract and raffinate; drying the raffinate; and then performing rotary evaporation to separate the organic matter extract and the extractant. This invention combines solvent extraction with free radical initiator technology to achieve the idea and method of dissociating coking coal and the targeted dissociation of sulfur-containing compounds in it. This invention not only promotes the structural dissociation of coking coal under mild conditions but also allows for the targeted control of the composition of the extracted products, offering advantages such as low cost, simple steps, and good extraction effect.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical technology and relates to a coal dissociation technology, particularly a method for the directional dissociation of sulfur-containing compounds in coking coal. Background Technology

[0002] my country's resource characteristics of being rich in coal, poor in oil, and lacking in gas determine that coal's dominant position in my country's energy consumption structure is unlikely to change in the short term. In the past, large-scale development and irrational utilization of coal resources were the main reasons for my country's excessively high carbon emissions. However, the introduction of the "dual carbon" target has led to increasing emphasis on the efficient and clean utilization of coal. Therefore, achieving high-value and rational utilization of coal is an important direction and trend for the future development of coal resources.

[0003] Shanxi Province, a major coal producer and consumer, has approximately 60% of its coal resources dedicated to coking coal, based on its resource endowment. However, over the past few decades, extensive coking methods have led to the waste of a large amount of high-quality coking coal. With increasing mining depth, the quality of Shanxi's coking coal has shown a significant downward trend, with a marked increase in the proportion of high-sulfur coal resources. Furthermore, the sulfur in these high-sulfur coals is primarily in the form of organic sulfur, which is difficult to remove through washing and beneficiation. Due to their high sulfur content, the use of these relatively abundant high-sulfur coking coals, especially high-sulfur coking coal with a sulfur content greater than 3%, is severely limited. They can only be used as thermal coal, which not only results in a huge waste of resources but also causes serious environmental pollution problems.

[0004] Based on the structure and composition of coal, high-sulfur coking coal belongs to the medium-to-high volatile matter coal type. Its structure contains abundant condensed aromatic rings, and the high volatile matter content indicates that there are more fatty side chains and weak bond structures in the coal. To a certain extent, the spatial network structure units of coal can be broken down into soluble small molecule compounds. Based on the structural characteristics of coking coal, depolymerization can be carried out to produce certain high-value-added chemicals. This is an effective way to achieve clean, efficient, and high-value conversion and utilization of coking coal.

[0005] In recent years, technologies for depolymerizing, separating, and converting coal into different products under mild conditions have received increasing attention both domestically and internationally. Solvent extraction is considered an effective method for depolymerizing coal. While room-temperature extraction is simple to operate, its extraction yield is low, the soluble small-molecule compounds in the product have low added value, and the macromolecular structure of coal undergoes rearrangement during extraction. The removal of some small-molecule phases leads to stronger intermolecular forces between existing structures, making subsequent extraction and dissociation more difficult. Further increasing the degree of coal dissociation requires raising the temperature, but this makes the reaction uncontrollable, increases the variety of depolymerized products, raises subsequent separation costs, and makes the entire extraction process relatively dangerous. Therefore, improving the degree of coal chemical structure dissociation and the added value of soluble small-molecule compounds during solvent extraction has become an urgent problem to be solved. Thus, developing a new solvent extraction method that can improve the degree of coal chemical structure dissociation under mild conditions while enabling the controllable conversion of soluble small molecules in the extraction product into compounds with higher added value is a technical problem that researchers urgently need to solve.

[0006] To date, existing technologies have focused on improving extraction rates and product added value during solvent extraction. For example, Chinese patent CN110833704A involves pre-treating coal samples by freezing before extraction, resulting in an improved extraction rate compared to the untreated sample. However, the extracted products are mainly free compounds associated with the coal structure, primarily monobenzene ring compounds and long-chain alkanes, which have low added value. Chinese patent CN110129083A treats lignite in a low-temperature plasma atmosphere by simultaneously adding a free radical initiator and a solvent. This method breaks the bonds between aromatic rings, solving the structural rearrangement problem caused by the extraction of small molecular phases during solvent extraction, thus improving the lignite extraction yield. However, this process is uncontrolled, and the free radical initiator in a plasma atmosphere easily attacks the products indiscriminately. Although the extraction rate increases, the products are diverse and have extremely low added value, resulting in underutilization of coal resources. Chinese patent CN102134501A describes the depolymerization of coal using organic amines as solvents. The depolymerization products are then eluted and enriched with various organic solvents to obtain high-value-added compounds of different product components. Although the depolymerization products can be directly extended into various high-value-added organic compounds or important chemical raw materials, the elution process is complex and cumbersome. Other research focuses on improving the extraction rate and the separation and purification of the extracted products, but lacks: 1. Methods to reduce structural rearrangement during solvent extraction while directionally dissociating the products to increase their added value; 2. The diversity of coal structure and composition determines the highly complex composition of the extracted products. The complex composition of the product system and the low content of high-value-added compounds make the separation and purification schemes for these high-value-added compounds extremely complex, resulting in resource waste. Summary of the Invention

[0007] This invention discloses a method for the directional dissociation of sulfur-containing compounds in bituminous coal. It combines solvent extraction with free radical initiator technology to achieve the dissociation of bituminous coal and the directional dissociation of sulfur-containing compounds in bituminous coal. This invention can not only promote the dissociation of bituminous coal structure under mild conditions, but also directionally control the composition of the extraction product. It has the advantages of low cost, simple steps, and good extraction effect.

[0008] This invention is achieved through the following technical solution:

[0009] This invention discloses a method for the directional dissociation of sulfur-containing compounds in coking coal, comprising the following steps:

[0010] (1) Coal sample crushing: The coking coal is crushed and dried for later use. The coking coal is crushed to a particle size of 200-400 mesh and the sulfur content of the coking coal is 3.5-5.1 wt%.

[0011] (2) Demineralization treatment of coal sample: The coal sample crushed in step (1) is subjected to flotation and sedimentation to obtain light components, and then the light components are acid washed, dried and ground to obtain clean coal to be treated;

[0012] (3) Add extractant to the clean coal obtained in step (2) and carry out the first stage extraction at a set temperature;

[0013] (4) After the first stage of extraction, a free radical initiator is added to it, and then the second stage of extraction is carried out to separate the extract and the raffinate. The raffinate is dried and the extract is separated by rotary evaporation to obtain organic matter extract and extractant. The composition of the separated extract is detected by GC×GC-MS-FID.

[0014] In a preferred embodiment, the density of the light component obtained after floating and sinking in step (2) is less than 1.35 g / cm³. 3 The light components are pickled using a mixed solvent of hydrochloric acid, hydrofluoric acid, and water. Preferably, the ratio of hydrochloric acid to water is 1:(0.5-2), and the ratio of hydrofluoric acid to water is 1:(0-2).

[0015] In a preferred embodiment, in step (3), the extractant is a mixture of polysulfonic acid ionic liquid W and pyridine in a volume ratio of 1:3 to 3:1, the mass-volume ratio of coal to extractant is 1g:(50-100)ml, and the extraction temperature is 35-105℃.

[0016] In a preferred embodiment, the ionic liquid is a polysulfonic acid ionic liquid W, with the following structural formula:

[0017]

[0018] The preparation steps of the polysulfonate ionic liquid W are as follows:

[0019] 1) Mix hexamethylenetetramine and 1,4-butyryl lactone at room temperature for 30 min, then transfer it to a reaction vessel and continue stirring at 40-60℃ for 6-10 h under nitrogen protection to obtain substance M; the molar ratio of hexamethylenetetramine and 1,4-butyryl lactone is 1:6.

[0020] 2) After adding 98% concentrated sulfuric acid to substance M, continue stirring at room temperature for 1-2 hours. After washing and drying the product, the final polysulfate ionic liquid W is obtained; the molar ratio of concentrated sulfuric acid to substance M is 1.05:1.

[0021] In a preferred embodiment, in step (4), the free radical initiator is one of azobisisobutyronitrile, tert-butyl hydroperoxide, and benzoyl peroxide, and the amount of the free radical initiator added is 1.0-3.5% of the coal mass. Further, the extraction time for the first stage is 1-22 hours, and the total extraction time for the first and second stages is 2-24 hours.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The first stage of extraction was carried out using a mixture of pyridine and ionic liquid as the extractant, followed by the addition of a free radical initiator for the second stage of extraction, thereby achieving the directional dissociation of sulfur-containing compounds in coking coal.

[0024] In the first stage, a mixture of pyridine and polysulfonate ionic liquid is used as a composite extractant. On the one hand, it can promote the swelling effect of the solvent on coal and enhance the depolymerization of the coal sample. On the other hand, the heterocyclic structure on the polysulfonate ionic liquid can enhance the dissolution effect on coal. The abundant sulfonate groups can promote the breaking of CS bonds during the extraction process, which is beneficial to the directional control of sulfur-containing compounds in the coal sample.

[0025] In the second stage, by adding free radical initiators at different extraction time periods, the extraction of small molecule phases is enhanced by dissociating the coal structure. At the same time, it can also interact with the weak bonds (SO and CS) in the small molecule compounds extracted at different times to directionally regulate the dissociation and purification separation of sulfur-containing compounds. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] Coking coal with a sulfur content of 3.87 wt% was ground to a particle size of 200-400 mesh, then acid-washed and dried to obtain clean coal. 1 g of clean coal was weighed and placed in a filter paper tube, which was then placed in a Soxhlet extraction apparatus. 100 mL of a mixture of pyridine and polysulfonic acid ionic liquid W with a volume ratio of 1:1 was added to a three-necked flask. The extraction temperature was set to 50 °C and the mixture was extracted for 16 h. After extraction, 0.025 g of tert-butyl hydroperoxide free radical initiator was added to the mixture for back-extraction for 8 h. After extraction, the mixture was evaporated and separated. The obtained dissociation products were quantitatively analyzed by GC×GC-MS-FID. The results showed that the dibenzothiophene content in the product was 80 mg / L; the methyldibenzothiophene content was 48 mg / L; and the dimethyldibenzothiophene content was 39 mg / L.

[0029] Example 2

[0030] Coking coal with a sulfur content of 5.06 wt% was ground to a particle size of 200-400 mesh, then acid-washed and dried to obtain clean coal. 1 g of clean coal was weighed and placed in a filter paper tube, which was then placed in a Soxhlet extraction apparatus. 100 mL of a mixture of pyridine and polysulfonic acid ionic liquid W with a volume ratio of 1:3 was added to a three-necked flask. The extraction temperature was set to 105 °C and the mixture was extracted for 20 h. After extraction, 0.035 g of azobisisobutyronitrile free radical initiator was added to the mixture for back-extraction for 4 h. After extraction, the mixture was evaporated and separated. The obtained dissociation products were quantitatively analyzed by GC×GC-MS-FID. The results showed that the dibenzothiophene content in the product was 64 mg / L; the methyldibenzothiophene content was 45 mg / L; and the dimethyldibenzothiophene content was 53 mg / L.

[0031] Example 3

[0032] Coking coal with a sulfur content of 4.63 wt% was ground to a particle size of 200-400 mesh, then acid-washed and dried to obtain clean coal. 1 g of clean coal was weighed and placed in a filter paper tube, which was then placed in a Soxhlet extraction apparatus. 100 mL of a mixture of pyridine and polysulfonic acid ionic liquid W with a volume ratio of 3:1 was added to a three-necked flask. The extraction temperature was set to 35 °C and the mixture was extracted for 12 h. After extraction, 0.01 g of benzoyl peroxide free radical initiator was added to the mixture for back-extraction for 12 h. After extraction, the mixture was evaporated and separated. The obtained dissociation products were quantitatively analyzed by GC×GC-MS-FID. The results showed that the dibenzothiophene content in the product was 34 mg / L; the methyldibenzothiophene content was 35 mg / L; and the dimethyldibenzothiophene content was 46 mg / L.

[0033] Comparative Example 1

[0034] Coking coal with a sulfur content of 3.87 wt% was ground to a particle size of 200-400 mesh, then acid-washed and dried to obtain clean coal. 1 g of clean coal was weighed and placed in a filter paper tube, which was then placed in a Soxhlet extraction apparatus. 100 mL of pyridine was added to a three-necked flask, and the extraction temperature was set to 50 °C. After extraction for 16 h, 0.025 g of tert-butyl hydroperoxide free radical initiator was added to the mixture for back-extraction for 8 h. After extraction, the mixture was evaporated and separated. The obtained dissociation products were quantitatively analyzed by GC×GC-MS-FID. The results showed that the dibenzothiophene content in the product reached 54 mg / L; the methyldibenzothiophene content was 34 mg / L, and the dimethyldibenzothiophene content was 32 mg / L.

[0035] Comparative Example 2

[0036] Coking coal with a sulfur content of 3.87 wt% was ground to a particle size of 200-400 mesh, then acid-washed and dried to obtain clean coal. 1 g of clean coal was weighed and placed in a filter paper tube, which was then placed in a Soxhlet extraction apparatus. 100 mL of a mixture of pyridine and polysulfonic acid ionic liquid W with a volume ratio of 1:1 was added to a three-necked flask. The extraction temperature was set to 50 °C, and after extraction for 24 h, evaporation separation was performed. The obtained dissociation products were quantitatively analyzed by GC×GC-MS-FID. The results showed that the content of dibenzothiophene in the product was 63 mg / L; the content of methyldibenzothiophene was 38 mg / L, and the content of dimethyldibenzothiophene was 35 mg / L.

[0037] The above embodiments of the present invention do not describe all details exhaustively, nor do they limit the present invention to the embodiments described above. Various changes, modifications, substitutions, and variations made by those skilled in the art to these embodiments without departing from the principles and spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the directional dissociation of sulfur-containing compounds in coking coal, characterized in that, Includes the following steps: (1) Coal sample crushing: Crush and dry the coking coal for later use; (2) Demineralization treatment of coal samples: The coal sample crushed in step (1) is subjected to flotation and sedimentation to obtain light components, and then the light components are acid washed, dried and ground to obtain clean coal to be treated; (3) Add an extractant to the clean coal obtained in step (2) and carry out the first stage extraction at a set temperature of 35~105℃; the extractant is a mixture of polysulfonic acid ionic liquid W and pyridine in a volume ratio of 1:3~3:1, the mass-volume ratio of the clean coal to the extractant is 1 g: (50-100) mL, and the extraction temperature is 35~105℃. (4) After the first stage of extraction, a free radical initiator is added to it, and then the second stage of extraction is carried out to separate the extract and the raffinate. The raffinate is dried and the extract is separated by rotary evaporation to obtain organic matter extract and extractant. The free radical initiator is one of azobisisobutyronitrile, tert-butyl hydroperoxide, and benzoyl peroxide. The amount of free radical initiator added is 1.0~3.5% of the coal mass. The structural formula of the polysulfonate ionic liquid W is as follows: ； The preparation steps of the polysulfonate ionic liquid W are as follows: 1) Hexamethylenetetramine and 1,4-butyryl lactone were mixed and stirred at room temperature for 30 min, then transferred to a reaction vessel and stirred at 60 °C for 8 h under nitrogen protection to obtain substance M; the molar ratio of hexamethylenetetramine and 1,4-butyryl lactone was 1:

6. 2) After adding 98% concentrated sulfuric acid to substance M, the mixture was stirred for 2 h at room temperature. The resulting product was washed and dried to obtain the final polysulfate ionic liquid M. The molar ratio of concentrated sulfuric acid to substance M was 1.05:

1.

2. The method for directional dissociation of sulfur-containing compounds in coking coal according to claim 1, characterized in that: In step (2), the density of the light component after floating and sinking is less than 1.35 g / cm³. 3 The light components are acid-washed using a mixed solvent of hydrochloric acid, hydrofluoric acid, and water.

3. The method for directional dissociation of sulfur-containing compounds in coking coal according to claim 2, characterized in that: In step (2), the ratio of hydrochloric acid to water is 1:(0.5-2), and the ratio of hydrofluoric acid to water is 1:(0-2).

4. The method for directional dissociation of sulfur-containing compounds in coking coal according to claim 1, characterized in that: The extraction time for the first stage is 1 to 22 hours, and the total extraction time for the first and second stages is 2 to 24 hours.

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