CN-116987523-B - Method for preparing monocyclic aromatic hydrocarbon and naphtha by pyrolysis and decarbonization of medium-low temperature coal tar

CN116987523BCN 116987523 BCN116987523 BCN 116987523BCN-116987523-B

Abstract

The invention belongs to the technical field of coal chemical industry, and relates to a method for preparing monocyclic aromatic hydrocarbon and naphtha by utilizing pyrolysis decarburization of medium-low temperature coal tar, which comprises the steps of 1) distilling the medium-low temperature coal tar under normal and reduced pressure to cut out asphalt with a fraction of 350 ℃, 2) extracting and refining the cut asphalt by utilizing a solvent to obtain polycyclic aromatic hydrocarbon-rich refined asphalt, 3) compounding the polycyclic aromatic hydrocarbon-rich refined asphalt with a functional solvent to obtain a compound mixed raw material, wherein the functional solvent is a shrinkage cracking stabilizer, a dissolution assisting hydrogen donor and polycyclic aromatic hydrocarbon oil, and 4) blowing and replacing the compound mixed raw material with nitrogen, and obtaining a product containing monocyclic aromatic hydrocarbon and naphtha by adopting a three-stage variable-temperature pyrolysis decarburization process under a hydrogen condition. The method provided by the invention has the advantages of low energy consumption, high yield of monocyclic aromatic hydrocarbon and naphtha, high BTX (benzene, toluene and xylene) content in the monocyclic aromatic hydrocarbon, low sulfur, nitrogen and olefin content in the naphtha product and high aromatic potential, fully utilizes aromatic hydrocarbon resources in medium-low temperature coal tar, and has high raw material utilization rate.

Inventors

LI DONG
HE TING
CUI LOUWEI
LIU JIAOJIAO
JIN ZHE
XU XIAN
SHI JUNHE
LIU TAO
Yu Fushuai

Assignees

西北大学

Dates

Publication Date: 20260508
Application Date: 20230728

Claims (3)

1. The method for preparing the monocyclic aromatic hydrocarbon and the naphtha by utilizing the pyrolysis and decarbonization of the medium-low temperature coal tar is characterized by comprising the following steps: 1) Cut of fractions Using medium-low temperature coal tar as a raw material, and adopting atmospheric and vacuum distillation to cut out fraction section asphalt with the temperature of more than 350 ℃; 2) Asphalt refining Extracting and refining the asphalt with the cut fraction section at the temperature of more than 350 ℃ in the step 1) by using a solvent to obtain refined asphalt rich in polycyclic aromatic hydrocarbon; In the step 2), the mass ratio of the solvent to the asphalt of the fraction section at the temperature of more than 350 ℃ is 1.5-3.5:1, and the conditions of extraction and refining are that the temperature is 160-220 ℃, the extraction time is 1-3 h, and the sedimentation time is 2-5 h; In the step 2), the solvent is a mixture of aromatic hydrocarbon and alkane, and the mass ratio of the aromatic hydrocarbon to the alkane in the solvent is 1:1-3:1; the aromatic hydrocarbon is one or more of toluene, xylene, durene, furfural and N-methyl pyrrolidone, and the alkane is one or more of N-hexane, N-heptane, cyclohexane, IP80 solvent oil and IP60 alkane solvent oil; 3) Refined asphalt compounding Compounding the polycyclic aromatic hydrocarbon-rich refined asphalt obtained in the step 2) with a functional solvent to obtain a compound mixed raw material, wherein the functional solvent is a shrinkage cracking stabilizer, a dissolution assisting hydrogen donor and polycyclic aromatic hydrocarbon oil; in the compound mixed raw material of the step 3), the content of the polycyclic aromatic hydrocarbon-rich refined asphalt is 40-60 wt%, and the mass ratio of the shrinkage cracking stabilizer, the dissolution assisting hydrogen donor and the polycyclic aromatic hydrocarbon oil is 2-4:1-2.5:3-6; In the step 3), the shrinkage cracking stabilizer, the dissolution assisting hydrogen donor and the polycyclic aromatic hydrocarbon oil are respectively cut into 210-230 ℃ fraction pitch, 230-300 ℃ fraction pitch and 300-350 ℃ fraction pitch by atmospheric and vacuum distillation by taking high-temperature coal tar as a raw material; The content of 2-ring aromatic hydrocarbon in the shrinkage cracking stabilizer is 75-80 wt%, the content of 2-ring aromatic hydrocarbon in the dissolution assisting hydrogen donor is 78-89 wt%, and the content of 3-ring aromatic hydrocarbon in the polycyclic aromatic hydrocarbon oil is 85-93 wt%; the compounding process of the step 3) is as follows: 3.1 Firstly, stirring the shrinkage cracking stabilizer, the dissolution assisting hydrogen donor and the polycyclic aromatic hydrocarbon oil according to a proportion to obtain a mixed functional solvent, wherein the stirring temperature is 70-110 ℃, the rotating speed is 80 r-100 r/min, and the stirring time is 0.5-1.5 h; 3.2 Mixing and stirring the polycyclic aromatic hydrocarbon-rich refined asphalt and the mixed functional solvent in proportion to obtain a compound mixed raw material, wherein the stirring temperature is 80-120 ℃, the rotating speed is 70-90 r/min, and the stirring time is 1-2 h; in the step 3.2), an amino-chasing dione stabilizer is also added into the mixed functional solvent, wherein the addition mass of the amino-chasing dione is 1-3% of the mass of the compound mixed raw materials; 4) Pyrolysis decarbonization Placing the compound mixed raw material in the step 3) into a reaction kettle, and blowing and replacing the compound mixed raw material by nitrogen, and obtaining a product containing monocyclic aromatic hydrocarbon and naphtha by adopting a three-stage variable-temperature pyrolysis decarburization process under the condition of hydrogen; in the step 4), hydrogen is filled into the reaction kettle to 2MPa before the three-stage variable temperature pyrolysis decarburization reaction, and the pressure is kept unchanged; The pyrolysis decarburization process is carried out under a three-stage variable-temperature constant-pressure program, and the specific process comprises the steps of heating to 380-410 ℃ in one stage, keeping the temperature for 2-4 hours, heating to 3-520 ℃ in the second stage, keeping the temperature for 3-6 hours, heating to 0.5-520 ℃ in the second stage, heating to 530-560 ℃ in the third stage, and keeping the temperature for 0.5-2 hours, wherein the heating rate is 2.5- -1 ~3.5℃﹒min -1 in the second stage.
2. The method for preparing monocyclic aromatic hydrocarbon and naphtha by pyrolysis decarburization of medium and low temperature coal tar according to claim 1, wherein in the polycyclic aromatic hydrocarbon-rich refined asphalt obtained in the step 2), the content of 2-4 cyclic aromatic hydrocarbon is 50-60 wt%, the content of >4 cyclic aromatic hydrocarbon is 8-10 wt%, the content of alkane is 14-20 wt%, the content of O is 4.8-6.2 wt%, the content of S is <0.2wt%, the content of N is <0.32wt%, and the content of QI is <0.1wt%.
3. The method for preparing monocyclic aromatic hydrocarbon and naphtha by utilizing pyrolysis decarbonization of medium and low temperature coal tar according to claim 2, wherein the content of monocyclic aromatic hydrocarbon in the product of the step 4) is 45-60%, and the content of naphtha is 20-30%.

Description

Method for preparing monocyclic aromatic hydrocarbon and naphtha by pyrolysis and decarbonization of medium-low temperature coal tar Technical Field The invention belongs to the technical field of coal chemical industry, and relates to a method for preparing monocyclic aromatic hydrocarbon and naphtha by utilizing pyrolysis decarburization of medium-low temperature coal tar. Background One of the important petrochemical energy sources in China is coal, and the proportion of the coal is high in primary energy consumption in China. In the future, clean, environment-friendly and efficient utilization of coal resources will become the trend of the development of the coal industry in China. Therefore, in recent years, china is greatly advocated for the classified utilization of coal, and the classified utilization of coal is taken as a development direction. Along with the gradual development of low-rank coal pyrolysis coke (semi-coke) industry, a large amount of medium-low temperature coal tar resources are produced as byproducts, and due to the limitation of the existing deep processing means, the application and consumption channels of heavy components of the medium-low temperature coal tar, especially coal pitch, are narrow, and the method is mainly used for producing low-added-value products such as medium-temperature pitch, modified pitch and fuel oil, so that precious hydrocarbon resources are wasted greatly and serious environmental pollution is caused. The processing and utilization of medium and low temperature coal tar pitch become the important point of upgrading and improving the energy industry structure in China. With the rapid development of economy, the demands of people for various chemical raw materials are increasingly rising. Monocyclic aromatic hydrocarbon such as BTX is taken as a basic chemical raw material and has long been a product which is prepared and touted in the market. In industry, aromatics are obtained mainly by naphtha catalytic reforming and naphtha steam cracking processes of petroleum-based routes. However, the process is quite complicated and the product yield is low. In the face of special situations of energy structures in China, if the existing raw material route is still used for preparing aromatic hydrocarbon, the petroleum raw material supply is tense. At the same time, downstream product prices remain high, which also exacerbates the complexity of the problem. Therefore, the technology for preparing aromatic hydrocarbon by using coal as raw material is particularly necessary. CN101538482B discloses a deep processing method of medium-low temperature coal tar, which comprises the steps of pre-treating the medium-low temperature coal tar, and then fractionating to obtain light fraction, phenol oil and heavy fraction. The heavy fraction is coked to obtain coked gasoline and diesel oil, the coked gasoline and diesel oil is mixed with light fraction to be used as raw materials for hydrofining and hydrocracking, and then catalytic reforming-aromatic extraction is carried out on naphtha obtained by hydrocracking to obtain chemical raw materials such as BTX. Although the method has potential, the process is complex and heavy fractions in coal tar cannot be fully utilized, so that the process is poor in economy. CN103436288a discloses a method for preparing aromatic hydrocarbon from coal tar, which comprises pretreating coal tar, performing atmospheric and vacuum distillation to obtain straight-run naphtha fraction, coking, cracking or hydrotreating the rest fraction to obtain naphtha fraction, and performing pre-hydrotreating to obtain reformed raw material after desulfurization and denitrification. The light aromatic hydrocarbon mixture is obtained through reforming, benzene and toluene are obtained through separating the light aromatic hydrocarbon mixture, and then benzene or benzene and paraxylene are obtained through further isomerism of aromatic hydrocarbon C8 and C8+ components, wherein the aromatic hydrocarbon yield is higher, but the pretreatment process of reforming raw materials is complex, and the energy consumption is higher. CN101280207a discloses a method for directly liquefying and comprehensively utilizing low-quality coal, which comprises the steps of carrying out a series of liquefaction reactions on pulverized coal and hydrogen-supplying solvent under a pressurized and heated state, carrying out gasification hydrogen production reaction on residues obtained after three-phase separation, condensing and separating liquefied generated gas, distilling and separating liquefied generated oil, thus obtaining products rich in aromatic hydrocarbon gasoline, diesel oil and the like. However, since the liquefaction reaction products are complex, the proportion of liquid products is not high, so that the yield of aromatic hydrocarbon oil is low, and the aim of preparing a large amount of aromatic hydrocarbons from coal is difficult to achieve. Naphtha is an important