Method for improving yield of coal direct liquefaction oil by adding alkane

Abstract

The application provides a method for improving the yield of coal direct liquefaction oil by adding alkanes, and belongs to the technical field of coal direct liquefaction.The application provides a method for improving the yield of coal direct liquefaction oil by adding alkanes, which comprises the following steps: mixing coal samples, hydrogen-donor solvents, catalysts, catalyst auxiliaries and alkanes, and then performing a liquefaction reaction to obtain coal direct liquefaction oil.The application adjusts the hydrogen-donating capacity of the solvent by adding alkanes on the basis of the original hydrogen-donor solvent, so that the purpose of improving the yield of liquefaction oil is achieved; the method improves the solubility of hydrogen in the oil coal slurry on the one hand, and effectively inhibits the polycondensation reaction of coal pyrolysis free radicals by utilizing the cracking behavior of alkanes in the reaction process, so that the yield of liquefaction oil is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of direct coal liquefaction technology, specifically relating to a method for increasing the yield of direct coal liquefaction oil by adding alkanes. Background Technology

[0002] Direct coal liquefaction (DCL) technology primarily involves breaking down the molecular structure of coal under high temperature and pressure, followed by hydrogenation to further convert it into small-molecule liquid fuels. Generally, DCL involves first mixing coal, a catalyst, and a hydrogen-donating solvent to prepare an oil-coal slurry. This slurry is then fed into a reactor for pyrolysis, where the broken coal free radical fragments are continuously stabilized by active hydrogen from the gas phase and the hydrogen-donating solvent, thereby generating small-molecule products. However, existing DCL processes have low oil yields. Therefore, improving the process to increase oil yield has become a pressing technical challenge in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a method for increasing the yield of direct coal liquefaction oil by adding alkanes. The method provided by this invention can significantly increase the yield of direct coal liquefaction oil.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for increasing the yield of direct coal liquefaction oil by adding alkanes, comprising: Coal samples, hydrogen-donating solvents, catalysts, catalyst additives, and alkanes are mixed and then subjected to a liquefaction reaction to obtain direct coal liquefaction oil.

[0005] Preferably, the alkane comprises alkanes having 5 to 30 carbon atoms or mixtures thereof.

[0006] Preferably, the mass of the alkane is 5-60% of the mass of the coal sample.

[0007] Preferably, the mass of the alkane is 10-50% of the mass of the coal sample.

[0008] Preferably, the temperature of the liquefaction reaction is 350~550℃.

[0009] Preferably, the temperature of the liquefaction reaction is 400~500℃.

[0010] Preferably, the hydrogen-donating solvent is at least one of tetrahydronaphthalene, 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, 4,5-dihydropyrene, and industrial recycled solvents.

[0011] Preferably, the catalyst is at least one selected from Fe-based catalysts, Ni-based catalysts, Mo-based catalysts, and Co-based catalysts.

[0012] Preferably, the initial hydrogen pressure during the liquefaction reaction is 1~12 MPa.

[0013] Preferably, the initial hydrogen pressure during the liquefaction reaction is 2~12 MPa.

[0014] This invention provides a method for increasing the yield of direct coal liquefaction oil by adding alkanes, comprising: mixing a coal sample, a hydrogen-donating solvent, a catalyst, a catalyst promoter, and alkanes, and then carrying out a liquefaction reaction to obtain direct coal liquefaction oil. This invention, based on the existing hydrogen-donating solvent, adjusts the hydrogen-donating capacity of the solvent by adding alkanes, ultimately achieving the goal of increasing the liquefaction oil yield. This method, on the one hand, increases the solubility of hydrogen in the coal-oil slurry; on the other hand, it utilizes the cracking behavior of alkanes during the reaction process to effectively inhibit the condensation reaction of free radicals from coal pyrolysis, thereby significantly increasing the liquefaction oil yield. The results of the examples show that the oil yield of the method provided by this invention is 56.83%~76.03%. Detailed Implementation

[0015] This invention provides a method for increasing the yield of direct coal liquefaction oil by adding alkanes, comprising: Coal samples, hydrogen-donating solvents, catalysts, catalyst additives, and alkanes are mixed and then subjected to a liquefaction reaction to obtain direct coal liquefaction oil.

[0016] The present invention does not have any special limitations on the source of the raw materials, and commercially available products known to those skilled in the art can be used.

[0017] In this invention, the coal sample is preferably pretreated before use; the pretreatment preferably includes drying, grinding and sieving in sequence.

[0018] The present invention does not impose any special limitations on the drying operation; drying to a constant weight is sufficient.

[0019] The present invention does not impose any special limitations on the grinding operation; any operation known to those skilled in the art can be used.

[0020] The present invention does not impose any special limitations on the screening operation, as long as the particle size of the coal sample is less than 80 mesh.

[0021] In this invention, the hydrogen-donating solvent is preferably at least one selected from tetrahydronaphthalene, 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, 4,5-dihydropyrene, and an industrial recycled solvent. This invention does not impose any specific limitation on the type of industrial recycled solvent; any industrial recycled solvent well-known to those skilled in the art can be used.

[0022] In this invention, the mass ratio of the coal sample to the hydrogen-supplying solvent is preferably 1:(1~3), more preferably 1:2.

[0023] In this invention, the catalyst is preferably at least one selected from Fe-based, Ni-based, Mo-based, and Co-based catalysts; the mass of the catalyst is 0.1-2.0% of the coal sample mass. As one embodiment, the mass of the catalyst is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.67%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, or 1.9% of the coal sample mass.

[0024] The present invention does not specifically limit the type of catalyst; any catalyst well known to those skilled in the art can be used.

[0025] This invention does not specifically limit the type of catalyst promoter; any catalyst promoter well-known to those skilled in the art can be used. As one embodiment, the catalyst promoter can be elemental sulfur.

[0026] The present invention does not impose any particular limitation on the amount of the catalyst additive; any amount well known to those skilled in the art can be used. As one embodiment, the mass of the catalyst additive can be 1.13% of the coal sample mass.

[0027] In this invention, the alkane preferably comprises alkanes or mixtures thereof having 5 to 30 carbon atoms. As one embodiment, the alkane may be n-hexane, n-tetrazane, n-hexadecane, n-nonadecane, n-eicosane, or n-tetracosane. The addition of alkane in this invention can increase the solubility of hydrogen in coal-oil slurry, effectively inhibit the condensation reaction of free radicals from coal pyrolysis, thereby significantly improving the yield of liquefied oil.

[0028] In this invention, when the alkane is n-hexadecane and n-tetracosane, the mass ratio of n-hexadecane to n-tetracosane is preferably 1:1.

[0029] In this invention, the mass of the alkane is preferably 5-60% of the mass of the coal sample. As one embodiment, the mass of the alkane can be 10%, 20%, 30%, 40%, or 50% of the mass of the coal sample. Limiting the mass of the alkane to the above range in this invention can further improve oil yield.

[0030] The present invention does not impose any special limitations on the operation of mixing the coal sample, hydrogen-donating solvent, catalyst, catalyst aid and alkane, and any technical solution for preparing the mixture well known to those skilled in the art can be used.

[0031] In this invention, the preferred temperature for the liquefaction reaction is 350-550°C; the preferred time for the liquefaction reaction is 30-120 min. As one embodiment, the temperature for the liquefaction reaction can be 400°C, 450°C, or 500°C; the preferred time for the liquefaction reaction can be 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, or 110 min. Limiting the temperature and time of the liquefaction reaction to the above ranges in this invention can further improve oil yield.

[0032] This invention does not impose a specific limitation on the rate of heating to the liquefaction reaction temperature; any heating rate well known to those skilled in the art can be used. As one embodiment, the rate of heating to the liquefaction reaction temperature can be 50°C / min.

[0033] In this invention, the liquefaction reaction is preferably carried out under sealed conditions; the initial hydrogen pressure during the liquefaction reaction is preferably 1~12 MPa. As one embodiment, the initial hydrogen pressure can be 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa or 11 MPa.

[0034] After liquefaction is completed, the present invention preferably separates the products of the liquefaction reaction to obtain direct coal liquefaction oil.

[0035] The present invention does not impose any special limitations on the separation operation; any separation operation known to those skilled in the art can be used.

[0036] As one implementation method, the separation can be Soxhlet extraction; the solvent for Soxhlet extraction can be n-hexane.

[0037] This invention involves adding specific alkanes as additives to a direct coal liquefaction reaction system in the presence of a catalyst and a hydrogen-donating solvent. By optimizing key process parameters such as the alkane addition ratio and reaction pressure, the yield of liquefied oil can be significantly improved, effectively enhancing the energy conversion efficiency and economy of the direct coal liquefaction process, thereby solving the problem of low oil yield in existing technologies.

[0038] Considering that the direct coal liquefaction process mainly relies on hydrogen-donating solvents to promote coal conversion, this invention introduces alkanes to improve oil yield, especially in the presence of a catalyst in a tubular bomb reactor. Based on the existing hydrogen-donating solvent, the addition of alkanes adjusts the solvent's hydrogen-donating capacity, ultimately increasing the liquefied oil yield. This method improves the solubility of hydrogen in the coal-oil slurry and, by utilizing the cracking behavior of alkanes during the reaction, effectively inhibits the condensation reaction of coal pyrolysis free radicals, thus significantly increasing the liquefied oil yield. After the reaction, the product is subjected to Soxhlet extraction using n-hexane as the extraction solvent. This invention has determined the optimal alkanes addition ratio for different pressure conditions, effectively improving the conversion efficiency and economy of the direct coal liquefaction process.

[0039] Compared with the prior art, the method of the present invention can achieve the following significant benefits: compared with the process without adding the alkane additive under the same conditions, the present invention can significantly improve the final oil yield, thereby effectively improving the energy conversion efficiency and economy of the direct coal liquefaction process.

[0040] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] The Fe-based catalysts used in the examples and comparative examples were all FeOOH from China Shenhua Coal-to-Oil Chemical Co., Ltd. The preparation methods of the Ni-based catalysts used in the examples and comparative examples are as follows: ① 50g of Al2O3 was impregnated in 50mL of 0.8mol / L Ni(NO3)2 aqueous solution and stirred at room temperature for 24h. ② The impregnated sample was transferred to a rotary evaporator, and the water was removed at 80℃. The sample was then dried and ground. ③ The resulting solid product was calcined at 600℃ for 4h. ④ The calcined sample was placed at 550℃ and reduced in a mixed atmosphere of 20mL / min H2 and 80mL / min N2 for 2h to obtain the Ni-based catalyst.

[0042] Example 1 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: (1) Dry, grind, and sieve the Xinjiang coal to be used for liquefaction to a particle size of less than 80 mesh; (2) Place 1.5g of treated coal sample, 3g of tetrahydronaphthalene, 0.3g of n-hexadecane, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur in a tube bomb type high pressure reactor, seal it and fill it with 5MPa of hydrogen gas; (3) Place the above reaction vessel in a sand bath furnace and heat it to 450°C at a heating rate of 50°C / min, and keep it at this temperature for 60 min. (4) After the reaction is completed, the solid and liquid phase products in the reactor are separated by Soxhlet extraction with n-hexane.

[0043] The calculated oil yield of Example 1 was 70.66 wt%.

[0044] Example 2 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.45g of n-hexadecane, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed, and then filled with 7MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reactor was then kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0045] The calculated oil yield of Example 2 was 76.03 wt%.

[0046] Example 3 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.3g of n-tetracosane, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed, and then filled with 4MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reactor was then kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0047] The calculated oil yield of Example 3 was 69.67 wt%.

[0048] Example 4 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.3g of n-hexadecane, 0.01g of Ni-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed, and then filled with 4MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reactor was then kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0049] The calculated oil yield of Example 4 was 66.35 wt%.

[0050] Example 5 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of industrial circulating solvent provided by China Shenhua Coal-to-Oil Chemical Co., Ltd., 0.3g of n-hexadecane, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular bomb-type high-pressure reactor, sealed and filled with 4MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min, and kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0051] The calculated oil yield of Example 5 was 56.83 wt%.

[0052] Example 6 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.15g of n-hexadecane, 0.15g of n-tetracosane, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular bomb-type high-pressure reactor, sealed, and then filled with 4MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to the target temperature of 450℃ at a programmed heating rate of 50℃ / min. The reactor was then kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0053] The calculated oil yield of Example 6 was 68.54 wt%.

[0054] Example 7 Based on Example 1, n-hexadecane was replaced with n-tridecane, while other conditions remained unchanged.

[0055] The calculated oil yield of Example 7 was 68.90 wt%.

[0056] Example 8 Based on Example 1, n-hexadecane was replaced with n-hexane, while other conditions remained unchanged.

[0057] The calculated oil yield of Example 8 was 67.72 wt%.

[0058] Example 9 Based on Example 1, n-hexadecane was replaced with n-nonadecane, while other conditions remained unchanged.

[0059] The calculated oil yield of Example 9 was 69.42 wt%.

[0060] Example 10 Based on Example 1, n-hexadecane was replaced with n-eicosane, while other conditions remained unchanged.

[0061] The calculated oil yield of Example 10 was 69.92 wt%.

[0062] Comparative Example 1 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed, and then filled with 5MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reactor was then kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0063] The calculated oil yield of Comparative Example 1 was 64.27 wt%.

[0064] Comparative Example 2 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed, and then filled with 7MPa of hydrogen gas. The reactor was placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reaction was then held at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0065] The calculated oil yield of Comparative Example 2 was 74.12 wt%.

[0066] Comparative Example 3 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed, and then filled with 4MPa of hydrogen gas. The reactor was placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reaction was then held at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0067] The calculated oil yield of Comparative Example 3 was 65.3 wt%.

[0068] Comparative Example 4 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of tetrahydronaphthalene, 0.01g of Ni-based catalyst and 0.017g of elemental sulfur were placed in a tubular high-pressure reactor, sealed and filled with 4MPa of hydrogen gas. The reactor was then placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min. The reactor was then kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0069] The calculated oil yield of Comparative Example 4 was 59.31 wt%.

[0070] Comparative Example 5 One method for increasing the yield of direct coal liquefaction oil by adding alkanes is as follows: 1.5g of Xinjiang coal, 3g of industrial circulating solvent provided by China Shenhua Coal-to-Oil Chemical Co., Ltd., 0.024g of Fe-based catalyst and 0.017g of elemental sulfur were placed in a tubular bomb-type high-pressure reactor, sealed, and then filled with 4MPa of hydrogen gas. The reactor was placed in a sand bath furnace and heated to 450℃ at a programmed heating rate of 50℃ / min, and the reaction was kept at this temperature for 60min. After the reaction was completed, the solid and liquid phase products in the reactor were separated by Soxhlet extraction with n-hexane.

[0071] The calculated oil yield of Comparative Example 5 was 53.74 wt%.

[0072] It is evident that, under the same reaction conditions, the addition of alkanes can effectively increase the oil yield of direct coal liquefaction. This method helps to enhance the energy conversion efficiency and economy of the entire liquefaction process.

[0073] As can be seen from the above embodiments and comparative examples, the method provided by the present invention can significantly improve the yield of direct coal liquefaction oil.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for increasing the yield of direct coal liquefaction oil by adding alkanes, comprising: Coal samples, hydrogen-donating solvents, catalysts, catalyst additives, and alkanes are mixed and then subjected to a liquefaction reaction to obtain direct coal liquefaction oil.

2. The method according to claim 1, characterized in that, The alkanes include alkanes with 5 to 30 carbon atoms or mixtures thereof.

3. The method according to claim 1, characterized in that, The mass of the alkane is 5-60% of the mass of the coal sample.

4. The method according to claim 3, characterized in that, The mass of the alkane is 10-50% of the mass of the coal sample.

5. The method according to claim 1, characterized in that, The liquefaction reaction occurs at a temperature of 350~550℃.

6. The method according to claim 5, characterized in that, The liquefaction reaction occurs at a temperature of 400~500℃.

7. The method according to claim 1, characterized in that, The hydrogen-donating solvent is at least one of tetrahydronaphthalene, 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, 4,5-dihydropyrene, and industrial recycled solvents.

8. The method according to claim 1, characterized in that, The catalyst is at least one of Fe-based catalysts, Ni-based catalysts, Mo-based catalysts, and Co-based catalysts.

9. The method according to claim 1, characterized in that, The initial hydrogen pressure during the liquefaction reaction is 1~12 MPa.

10. The method according to claim 9, characterized in that, The initial hydrogen pressure during the liquefaction reaction is 2~12 MPa.