An improved process for preparing fine chemicals from lignite catalytic pyrolysis
By combining hydrothermal modification of lignite with catalytic reforming of pyrolysis volatiles, the problems of catalyst deactivation due to carbon deposition and low aromatic yield were solved, achieving long-term stable operation of the catalyst and improving the yield of light aromatics, thus promoting the industrial application of lignite catalytic pyrolysis technology.
Patent Information
- Application Number
- CN202310701615.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-14
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2043-06-14
AI Technical Summary
In the existing technology for preparing light aromatics by catalytic pyrolysis of lignite, the catalyst is prone to carbon deposition and deactivation, and the yield of aromatics is low, which hinders the industrial application of this technology. Furthermore, the high water content and oxygen content of lignite are obstacles to its clean utilization.
A method combining hydrothermal modification of lignite with catalytic reforming of pyrolysis volatiles was adopted to remove oxygen-containing functional groups from lignite, optimize the problem of catalyst carbon deposition and deactivation, and improve the selectivity and yield of light aromatics.
It effectively improved the yield of light aromatics, alleviated the problem of catalyst carbon deposition and deactivation, achieved long-term stable operation of the catalyst, and promoted the industrialization process of lignite-based light aromatics preparation technology.
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Figure CN116676093B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lignite catalytic pyrolysis in coal chemical industry, and specifically relates to an improved process for preparing fine chemicals from lignite catalytic pyrolysis. Background Technology
[0002] Catalytic reforming of lignite pyrolysis volatiles to produce light aromatics such as benzene (B), toluene (T), xylene (X), ethylbenzene (E), and naphthalene (N) is considered one of the preferred technologies for the high-value-added clean utilization of lignite and is an important guarantee for achieving clean and efficient utilization of lignite. Furthermore, light aromatics are a crucial foundation of the chemical industry and occupy an important position in the national economy. However, approximately 97% of my country's aromatics originate from petrochemicals, while my country's dependence on imported crude oil exceeds 70%. Given the insufficient supply of raw materials and continuously increasing demand, it is necessary to develop other pathways to obtain aromatics. my country has abundant lignite reserves, high reactivity, and high volatile matter content, making it an excellent raw material for the production of light aromatics. However, in the process of catalytic pyrolysis of lignite to produce light aromatics, catalyst deactivation due to carbon buildup and low aromatic yield are the biggest obstacles to the industrial application of this technology. Currently, to improve the aromatic selectivity and anti-carbon buildup ability of catalysts, research focuses mainly on catalyst modification, including the construction of microporous composite pore structures, modification of acidic sites, and modification with loaded active metals. These methods have improved catalyst deactivation and increased aromatic yields to some extent, but they are still far from commercialization. Maximizing the yield of light aromatics and ensuring long-term stable operation of the catalyst remain the ultimate goals for the promotion of lignite catalytic pyrolysis technology. How to further optimize and improve this challenge to drive the industrialization of lignite-based light aromatics preparation technology is an important issue. Summary of the Invention
[0003] To address the problems existing in the prior art, this invention proposes an improved process for preparing fine chemicals from lignite catalytic pyrolysis. This invention organically combines hydrothermal modification of lignite with catalytic reforming of pyrolysis volatiles to prepare light aromatics. The hydrothermal modification removes oxygen-containing functional groups from lignite and regulates the volatile matter content during lignite pyrolysis, improving catalyst deactivation due to carbon buildup during catalytic reforming and enhancing the selectivity and yield of light aromatics. Effective deoxygenation of lignite can increase the yield of light aromatics and alleviate catalyst deactivation due to carbon buildup. Therefore, this invention organically couples hydrothermal dehydration and deoxygenation of lignite with the preparation of light aromatics from coal-based catalytic pyrolysis, solving the problem of high moisture content in lignite and effectively optimizing the issues of catalyst deactivation and low aromatic yield in lignite-based light aromatics.
[0004] The technical solution adopted in this invention includes the following steps:
[0005] (1) The raw lignite is crushed, and then the raw lignite is mixed with deionized water evenly and subjected to hydrothermal reaction to obtain a solid-liquid mixture.
[0006] (2) Separate the solid-liquid mixture in step (1) and vacuum dry the separated solid product to obtain the raw material;
[0007] (3) The molecular sieve catalyst is calcined in air and then crushed;
[0008] (4) Place the crushed molecular sieve catalyst from step (3) into a pyrolysis reactor, introduce argon gas and raise the temperature. After the temperature stabilizes, send the raw material from step (2) into the pyrolysis reactor for catalytic pyrolysis. Light aromatics are obtained, and the light aromatics are collected using two-stage dichloromethane condensation hydrazine.
[0009] The lignite raw coal mentioned in step 1 is crushed to 0.1-0.6 mm; the mass ratio of the raw coal to deionized water is (0.5-1):1;
[0010] The hydrothermal reaction described in step 1 is as follows: N2 is introduced under normal pressure at a flow rate of 100-180 ml / min for 4-12 min; then, under closed conditions, the temperature is increased to 150-320℃ at a programmed heating rate of 5-20℃ / min and held for 30-60 min.
[0011] The vacuum drying temperature in step 2 is 100-110℃, and the drying time is 8-12 hours.
[0012] The molecular sieve catalyst mentioned in step 3 is HZSM-5;
[0013] The calcination temperature in step 3 is 600℃, and the calcination time is 4 to 6 hours; the crushing is to crush the particles to a size of less than 75 μm.
[0014] The flow rate of argon gas introduced in step (4) is 100-120 ml / min, and the argon gas introduction time is 20-30 min;
[0015] The heating in step (4) is to raise the temperature to 500-700℃, and the heating rate is 5-10℃ / min;
[0016] In step (4), the feed rate of the raw material into the pyrolysis reactor is 0.1 to 0.5 g / min; the catalytic pyrolysis reaction is carried out for 20 to 40 min after all the raw material has entered the pyrolysis reactor.
[0017] The mass ratio of the raw material and the molecular sieve catalyst in step (4) is 5:1.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] Lignite-based light aromatics are of significant strategic importance to the sustainable development of my country's coal and chemical industries. Maximizing the yield of light aromatics and ensuring long-term stable operation of catalysts are crucial for the industrial application of lignite catalytic pyrolysis. However, existing technologies mainly focus on catalyst modification, lacking research on how pretreatment of raw materials can improve catalyst deactivation due to carbon buildup and increase the yield of light aromatics. Furthermore, my country has abundant lignite reserves, high reactivity, and high volatile matter content, making it an excellent raw material for aromatics production. However, high moisture and oxygen content remain obstacles to the clean utilization of lignite; dehydration and deoxygenation are fundamental and key to clean utilization. The organic coupling of lignite hydrothermal dehydration and deoxygenation with coal-based aromatics production not only solves the problem of high moisture content in lignite but also effectively optimizes the issues of catalyst deactivation and low aromatics yield in lignite-based light aromatics production. Attached Figure Description
[0020] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention, particularly the type of molecular sieve catalyst.
[0022] Example 1
[0023] Process flow diagram as follows Figure 1 As shown, the specific steps include:
[0024] (1) Using lignite from Luxin Coal Mine in Xilingol League, Inner Mongolia as raw material, the lignite was crushed to 0.15 mm. Its elemental analysis is shown in Table 1.
[0025] (2) Dry the lignite in a vacuum drying oven at 105°C for 12 hours and store it in a self-sealing bag for later use;
[0026] (3) The molecular sieve catalyst HZSM-5 was calcined in a muffle furnace under air atmosphere for 5 hours, and the 75μm fragment was taken out;
[0027] (4) Place 2g of catalyst on the quartz wool in the pyrolysis reactor in advance. Take raw lignite according to the mass ratio of lignite to catalyst of 5:1 for catalytic pyrolysis reaction. The specific pyrolysis process conditions are as follows: introduce 120ml / min into the pyrolysis reaction system to replace the air in the pyrolysis reaction system. After the replacement is completed, start to raise the temperature to 600℃ at a program of 10℃ / min. After the system temperature stabilizes, start to feed at a rate of 0.2g / min. After all the materials have entered the reaction system, maintain the system for 30min and the reaction ends.
[0028] (5) The yield of light aromatic hydrocarbons was tested by gas chromatography, and the results are shown in Table 1.
[0029] (6) The amount of carbon deposited on the catalyst was tested using a micro fixed-bed reactor and a gas chromatograph. The results are shown in Table 1.
[0030] Table 1. Analysis of Light Aromatic Hydrocarbon Yield and Carbon Deposition in Lignite Raw Coal
[0031]
[0032] Example 2
[0033] (1) Using lignite from Luxin Coal Mine in Xilingol League, Inner Mongolia as raw material, the lignite was crushed to 0.15 mm;
[0034] (2) Dry the lignite in a vacuum drying oven at 105℃ for 12 hours and store it in a self-sealing bag;
[0035] (3) Mix lignite and distilled water in a beaker at a mass ratio of 1:1 and carry out a hydrothermal reaction. The mixture is introduced into the reactor at a flow rate of 120 ml / min to replace the air in the reactor. Then, the temperature is increased according to the program, starting at 5℃ / min. The final temperature of the reaction is 200℃. After reaching the final temperature, the temperature is maintained for 40 min, and the reaction ends.
[0036] (3) After the reaction vessel temperature is cooled to room temperature, the reactants are removed and solid-liquid separation is achieved using a vacuum filtration device, a Buchner funnel, and qualitative filter paper. The separated solids are then placed in a vacuum drying oven at 105°C for 8 hours.
[0037] (4) The molecular sieve catalyst HZSM-5 was calcined in a muffle furnace under air atmosphere for 4 hours, and the 75μm fragment was taken out.
[0038] (5) Take 2g of catalyst and place it on the quartz wool in the pyrolysis reactor in advance. Take lignite hydrothermal upgraded coal according to the mass ratio of lignite to catalyst of 5:1 and place it in the micro screw feeder.
[0039] (6) Further start the lignite catalytic pyrolysis reaction. The specific parameters of the reaction are as follows: 120 ml / min is introduced into the pyrolysis reaction system to replace the air in the pyrolysis reaction system. After the replacement is completed, the temperature is increased to 600℃ at a programmed rate of 10℃ / min. After the system temperature is stable, the feed rate is increased to 0.2 g / min. After all the materials have entered the reaction system, the system is maintained for 30 min, and the reaction ends.
[0040] (7) The yield of light aromatic hydrocarbons after the reaction was tested by gas chromatography, and the amount of CO2 in the catalyst was tested by micro fixed-bed reactor-gas chromatography. The amount of carbon deposited in the catalyst was obtained as shown in Table 2.
[0041] Table 2. Analysis of light aromatic hydrocarbon yield and carbon deposition from catalytic pyrolysis of lignite at -200℃.
[0042]
[0043] Example 3
[0044] In step (3), lignite and distilled water are mixed in a beaker at a mass ratio of 1:1 and subjected to hydrothermal reaction. The mixture is introduced into the reactor at a flow rate of 120 ml / min to replace the air in the reactor. Then, the temperature is increased according to the program, starting at 5 °C / min. The final reaction temperature is 250 °C. After reaching the final temperature, the temperature is maintained for 40 min, and the reaction ends.
[0045] In this embodiment, apart from the above operation settings, the other operations are the same as in embodiment (2).
[0046] Table 3. Analysis of light aromatic hydrocarbon yield and carbon deposition from catalytic pyrolysis of lignite at -250℃.
[0047]
[0048] Example 4
[0049] In step (3), lignite and distilled water are mixed in a beaker at a mass ratio of 1:1 for hydrothermal reaction. The mixture is introduced into the reactor at a flow rate of 120 ml / min to replace the air in the reactor. Then, the temperature is increased according to the program, starting at 5℃ / min. The final reaction temperature is 310℃. After reaching the final temperature, the temperature is maintained for 40 min, and the reaction ends.
[0050] In this embodiment, apart from the above operation settings, the other operations are the same as in embodiment (2).
[0051] Table 4. Analysis of light aromatic hydrocarbon yield and carbon deposition from catalytic pyrolysis of lignite at -250℃.
[0052]
[0053] This invention provides a process method aimed at improving the yield of light aromatics from lignite pyrolysis volatile matter catalytic reforming and alleviating catalyst deactivation due to carbon buildup. Lignite hydrothermal modification is a non-evaporative dehydration technology that also regulates free radicals and oxygen-containing functional groups, altering the distribution characteristics of pyrolysis products. Therefore, it improves the yield of light aromatics from lignite catalytic pyrolysis and alleviates the problem of catalyst deactivation due to carbon buildup. This invention will have significant practical implications for the preparation of light aromatics from lignite pyrolysis catalytic reforming.
[0054] The above technical solutions illustrate the technical concept of the present invention, but should not be construed as limiting the scope of protection of the present invention. Any modifications or alterations made to the above technical solutions based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.
Claims
1. An improved process for preparing fine chemicals from lignite catalytic pyrolysis, characterized in that, Includes the following steps: (1) The raw lignite is crushed, and then the raw lignite is mixed with deionized water evenly and subjected to hydrothermal reaction to obtain a solid-liquid mixture. The hydrothermal reaction is specifically as follows: N2 is introduced under normal pressure at a flow rate of 100-180 ml / min for 4-12 min. Then, under sealed conditions, the temperature is increased to 150-320℃ at a programmed heating rate of 5-20℃ / min and held for 30-60 min. (2) Separate the solid-liquid mixture in step (1) and vacuum dry the separated solid product to obtain the raw material; (3) The molecular sieve catalyst is calcined in air and then crushed; The molecular sieve catalyst is HZSM-5; (4) Place the molecular sieve catalyst crushed in step (3) into a pyrolysis reactor, introduce argon gas and raise the temperature. After the temperature stabilizes, send the raw material in step (2) into the pyrolysis reactor to carry out catalytic pyrolysis reaction to obtain light aromatics. Use two-stage dichloromethane condensation hydrazine to collect the light aromatics.
2. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, The lignite raw coal mentioned in step (1) is crushed to 0.1-0.6 mm; the mass ratio of the raw coal to deionized water is (0.5-1):
1.
3. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, The vacuum drying temperature in step 2 is 100-110℃, and the drying time is 8-12 hours.
4. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, The calcination temperature in step 3 is 600℃, and the calcination time is 4 to 6 hours; the crushing is to crush the particles to a size of less than 75μm.
5. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, In step (4), the flow rate of argon gas introduced is 100-120 ml / min, and the time for introducing argon gas is 20-30 min.
6. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, The heating in step (4) is to raise the temperature to 500-700℃, and the heating rate is 5-10℃ / min.
7. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, In step (4), the feed rate of the raw material into the pyrolysis reactor is 0.1 to 0.5 g / min; the catalytic pyrolysis reaction is carried out for 20 to 40 min after all the raw material has entered the pyrolysis reactor.
8. The improved process for preparing fine chemicals from lignite catalytic pyrolysis according to claim 1, characterized in that, The mass ratio of the raw material and the molecular sieve catalyst in step (4) is 5:1.