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EP-4393902-B1 - METHOD FOR PREPARING P-XYLENE

EP4393902B1EP 4393902 B1EP4393902 B1EP 4393902B1EP-4393902-B1

Inventors

  • LIU, ZHONGMIN
  • YU, Zhengxi
  • YANG, YUE

Dates

Publication Date
20260506
Application Date
20211210

Claims (20)

  1. A method for preparing p-xylene, comprising introducing raw materials containing methanol, naphtha, and CO 2 into a reactor filled with a catalyst for a reaction to produce the p-xylene; wherein conditions for the reaction are as follows: a reaction temperature is in a range from 450°C to 650°C, a reaction pressure is in a range from 0.1 MPa to 3.5 MPa, a weight hourly space velocity of the naphtha is in a range from 0.1 h -1 to 5 h -1 , a weight hourly space velocity of the CO 2 is in a range from 0.1 h -1 to 3 h -1 , and a weight hourly space velocity of the methanol is in a range from 0.1 h -1 to 5 h -1 ; wherein a mass ratio of the CO 2 , the naphtha, and the methanol is (0.3-2):1:(0.3-2).
  2. The method according to claim 1, wherein conditions for the reaction are as follows: a reaction temperature is in a range from 500°C to 600°C, a reaction pressure is in a range from 0.1 MPa to 3 MPa, a weight hourly space velocity of the naphtha is in a range from 0.5 h -1 to 2 h -1 , a weight hourly space velocity of the CO 2 is in a range from 0.5 h -1 to 2 h -1 , and a weight hourly space velocity of the methanol is in a range from 0.5 h -1 to 2 h -1 .
  3. The method according to claim 1, wherein the mass ratio of the CO 2 , the naphtha, and the methanol is (0.3-1.5):1:(0.3-1.5).
  4. The method according to claim 1, wherein components containing benzene and toluene in a mixture obtained after the reaction are separated from the mixture, the components are returned to a reaction system and co-fed with the raw materials for the reaction on the catalyst to produce the p-xylene.
  5. The method according to claim 1, wherein the catalyst is an acidic molecular sieve.
  6. The method according to claim 5, wherein the acidic molecular sieve is an HZSM-5 zeolite molecular sieve.
  7. The method according to claim 6, wherein the HZSM-5 zeolite molecular sieve has a silica-alumina ratio (Si/Al ratio) of 10-50.
  8. The method according to claim 6, wherein the HZSM-5 zeolite molecular sieve is a metal-modified HZSM-5 zeolite molecular sieve.
  9. The method according to claim 8, wherein a metal used for a metal modification is selected from at least one of La, Zn, Ga, Fe, Mo, and Cr.
  10. The method according to claim 6, wherein the HZSM-5 zeolite molecular sieve is an HZSM-5 zeolite molecular sieve modified by a metal modification and a silanization reagent modification.
  11. The method according to claim 10, wherein a silanization reagent used for the silanization reagent modification is selected from at least one of compounds with the following chemical formula: wherein R 1 , R 2 , R 3 , and R 4 are independently selected from C 1-10 alkyl and C 1-10 alkoxyl.
  12. The method according to claim 11, wherein at least one of the R 1 , the R 2 , the R 3 , and the R 4 is selected from the C 1-10 alkoxyl.
  13. The method according to claim 11, wherein the silanization reagent is selected from tetraethyl silicate and/or tetramethyl silicate.
  14. The method according to claim 1, wherein before the reaction, the method further comprises a step of preparing the catalyst: placing an HZSM-5 zeolite molecular sieve in a metal salt solution, and carrying out an impregnation, a drying, and a calcination to obtain a metal-modified HZSM-5 zeolite molecular sieve.
  15. The method according to claim 14, wherein conditions for the impregnation are as follows: an impregnation temperature is in a range from 60°C to 100°C, and an impregnation time is in a range from 2 to 10 hours.
  16. The method according to claim 14, wherein a solid-liquid ratio of the HZSM-5 zeolite molecular sieve to the metal salt solution is 1:20 to 1:1.
  17. The method according to claim 14, wherein a metal salt is a soluble metal salt corresponding to a metal used for a metal modification.
  18. The method according to claim 14, wherein before the reaction, a preparation of the catalyst further comprises the following steps: subjecting a material containing a silanization reagent and the metal-modified HZSM-5 zeolite molecular sieve to a contact treatment, and carrying out a purging with an inert gas, followed by the calcination to obtain an HZSM-5 zeolite molecular sieve modified by a metal modification and a silanization reagent modification.
  19. The method according to claim 18, wherein the contact treatment is carried out at a temperature of a range from 250°C to 450°C.
  20. The method according to claim 18, wherein a weight hourly space velocity of the silanization reagent is in a range from 0.02 h -1 to 0.5 h -1 .

Description

TECHNICAL FIELD The present application relates to a method for preparing p-xylene, in particular to a method for preparing p-xylene by coupling conversion of methanol, naphtha and CO2 on a zeolite molecular sieve-based catalyst, and belongs to the field of petrochemical industry. BACKGROUND With the development of modern industry, the concentration of carbon dioxide (CO2), as a main greenhouse gas in atmosphere, is constantly increasing, leading to an increasingly prominent greenhouse effect. In 2020, global CO2 emissions have reached 34 billion tons, and the CO2 emissions in China have exceeded 10 billion tons. In 2020, during the 75th session of the United Nations General Assembly, China proposed that the CO2 emissions should reach a peak value before 2030, and efforts should be made to achieve carbon neutrality before 2060. Therefore, recycling, fixation and resource utilization of the CO2 have become a close concern of countries in the world. From the perspective of resources, the CO2 is a cheapest one carbon resource in the world. Aromatic hydrocarbons represented by three benzene compounds (benzene, toluene and p-xylene) are basic chemical raw materials, in which the p-xylene, as a most concerned product in the aromatic hydrocarbons, has a large market scale and depends on import in large quantities. In 2019, the output of the p-xylene reached 13.46 million tons, the import volume reached 15.94 million tons, and the foreign-trade dependence was 52%. In industry, the p-xylene is mainly produced from naphtha by a catalytic reforming and aromatic hydrocarbon combination device. The technology has many steps, a complicated process and huge investment, and therefore, a large part of aromatic hydrocarbons are obtained by the technology of preparing aromatic hydrocarbons from the naphtha. The aromatic hydrocarbons produced by catalytic reforming of the naphtha account for 80% of the amount of petroleum-based aromatic hydrocarbons. Therefore, rapid development of CO2 utilization technologies, especially conversion of CO2 into aromatic hydrocarbons, has important economic and social significance. On the one hand, the problem of shortage of chemicals in China can be solved. On the other hand, due to a large market scale of aromatic hydrocarbon products, large-scale emission reduction of CO2 can be realized. CN108160104A discloses a catalyst for hydrogenation of carbon dioxide to produce aromatic hydrocarbons and a preparation method and application thereof. A nano-metal oxide&ZSM-5 molecular sieve catalyst obtained by mechanical mixing, grinding mixing or ball milling is used, the content of C5+ components in carbon dioxide hydrogenation products is up to 80%, and the selectivity of aromatic hydrocarbons is 70% or above. CN107840778A discloses a method for preparing aromatic hydrocarbons by hydrogenation of carbon dioxide under the action of a composite catalyst. The composite catalyst is obtained by mixing an iron-based catalyst for hydrogenation of carbon dioxide to produce low carbon olefins as a first component with a metal-modified or unmodified molecular sieve mainly having the effect of aromatization of olefins. Under the action of the composite catalyst, the conversion rate of CO2 is 33%, the selectivity of C5+ hydrocarbons can reach 65%, and aromatic hydrocarbons account for 63% of the C5+ hydrocarbons. Studies have shown that the CO2 is activated first under the action of a metal oxide, and then intermediate components produced by a reaction with hydrogen undergo carbon chain growth, transfer, ring formation and other processes under the action of a molecular sieve to produce aromatic hydrocarbons. All the above studies indicate that liquid hydrocarbons or aromatic hydrocarbons are produced by hydrogenation of CO2. In addition to technical indicators, sources of hydrogen are also a key problem limiting industrial application. CN111187141A discloses a method for preparing gasoline from methanol and/or dimethyl ether for the co-production of p-xylene by separating the components containing benzene and toluene in the conversion reaction product of methanol and/or dimethyl ether and returning them to the feed Continue the reaction in the process, effectively improving the selectivity and yield of p-xylene. CN102199446A discloses a method for preparing aromatic hydrocarbons using methanol, which can control the heat of the reaction process well and achieve a high conversion rate of aromatic hydrocarbons. By using methanol and Fischer-Tropsch synthetic naphtha components as reaction raw materials and performing thermal coupling, the reaction thermal effects of the two cancel each other out, reducing the thermal effect of the total reaction, which can well prevent the process of simply using methanol to prepare aromatics. The fly temperature of the reactor deactivates the catalyst and can effectively improve the conversion rate of aromatics. SUMMARY The present application provides a new technical route for