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CN-122010665-A - Heat removal method and reaction furnace for preparing carbon dioxide by oxidative coupling of methane

CN122010665ACN 122010665 ACN122010665 ACN 122010665ACN-122010665-A

Abstract

The invention belongs to the technical field of ethylene preparation by oxidative coupling of methane, and relates to a heat removal method and a reaction furnace for preparing carbon dioxide by oxidative coupling of methane. The method comprises the steps of (1) introducing methane and oxygen into a catalyst bed layer to be in contact with a catalyst for catalytic reaction, wherein the methane is fed at a constant speed, the oxygen is fed gradually, the initial feeding amount is increased to keep the alkoxy ratio at 7-10:1, (2) removing heat when the temperature of a hot spot exceeds 750 ℃, reducing the temperature of the hot spot to a range of 700-730 ℃, stopping removing heat, and (3) continuously increasing the feeding amount of the oxygen, and removing heat when the temperature of the hot spot is higher than 730 ℃ to keep the temperature of the hot spot at a range of 700-730 ℃ until the reaction is finished. The heat removal method can effectively and quickly remove the reaction heat to reduce the temperature of a hot spot, and the heat removal method is adopted to remove the heat of the reaction furnace for oxidative coupling of methane, so that the method is suitable for the catalyst loading amount as large as more than 10 g.

Inventors

  • ZHAO QINGRUI
  • WANG XUE
  • LI WEI

Assignees

  • 中国石油化工股份有限公司
  • 中石化(北京)化工研究院有限公司

Dates

Publication Date
20260512
Application Date
20241112

Claims (11)

  1. 1. The heat removal method for preparing the carbon dioxide by oxidative coupling of methane is characterized by comprising the following steps of: (1) Introducing methane and oxygen into a catalyst bed layer to contact with a catalyst for catalytic reaction, wherein the methane is fed at a constant speed, the oxygen is fed in a gradually increasing manner, and the initial feeding amount is such that the alkoxy ratio is 7-10:1; (2) When the temperature of the hot spot exceeds 750 ℃, carrying out heat removal, reducing the temperature of the hot spot to the range of 700-730 ℃, and stopping heat removal; (3) And continuously increasing the oxygen feeding amount, and when the temperature of the hot spot is higher than 730 ℃, carrying out heat removal to ensure that the temperature of the hot spot is kept in the range of 700-730 ℃ until the reaction is finished.
  2. 2. The heat removal process of claim 1, wherein the loading of catalyst in the catalyst bed is greater than or equal to 10g.
  3. 3. The heat removal method according to claim 1, wherein in the step (2), after the temperature of the hot spot is reduced to a range of 700-730 ℃, the heat removal is stopped after stabilizing for 5-20 min.
  4. 4. A heat removal process according to claim 1, wherein the conditions for the catalytic reaction comprise a reaction temperature of 600-720 ℃, preferably 620-660 ℃, a reaction pressure of 0.001-0.05MPa and a reaction gas hourly space velocity in terms of methane and oxygen of 20000-100000 mL/(g.h).
  5. 5. A heat removal process according to claim 1 wherein in step (3) the final alkoxide ratio of methane to oxygen is from 2 to 4:1.
  6. 6. A heat removal process according to claim 1 wherein the carbon diolefms are ethane and/or ethylene.
  7. 7. A reaction furnace for preparing carbon dioxide by oxidative coupling of methane, which is used for executing the heat removal method for preparing carbon dioxide by oxidative coupling of methane according to any one of claims 1-6, and is characterized in that the reaction furnace comprises a furnace body, a reaction tube in the furnace body, a heat preservation layer between the furnace body and the reaction tube and a catalyst bed layer arranged in the reaction tube; wherein the furnace body is provided with an opening and closing part, and a section of freely detachable heat preservation section is arranged near the opening and closing part of the furnace body.
  8. 8. The reactor according to claim 7, wherein the freely detachable heat-insulating section has a thickness consistent with that of the heat-insulating layer of the other part of the reactor and is closely attached to the heat-insulating layer of the other part of the reactor.
  9. 9. The reactor according to claim 7, wherein the freely detachable insulation section covers 15-50%, preferably 25-40%, of the total length of the catalyst bed and has a width of 0.25-0.7, preferably 0.3-0.5 times the inner diameter of the reaction tube.
  10. 10. A heat removal method using the reaction furnace according to any one of claims 7 to 9, comprising the steps of: (1) Introducing methane and oxygen into a reaction cavity to contact with a catalyst for catalytic reaction, wherein the methane is fed at a constant speed, the oxygen is fed in a gradually increasing manner, and the initial feeding amount keeps the alkoxy ratio at 7-10:1; (2) When the temperature of the hot spot exceeds 750 ℃, opening the freely detachable heat preservation section, reducing the temperature of the hot spot to the range of 700-730 ℃, and closing the freely detachable heat preservation section; (3) And continuously increasing the oxygen feeding amount, and when the temperature of the hot spot is higher than 730 ℃, opening the freely detachable heat preservation section to remove heat, so that the temperature of the hot spot is kept in the range of 700-730 ℃ until the reaction is finished.
  11. 11. The heat removal method using a reaction furnace according to claim 10, wherein the hot spot temperature is reduced to a range of 700-730 ℃ for 10-20 min, and then the freely detachable heat preservation section is closed.

Description

Heat removal method and reaction furnace for preparing carbon dioxide by oxidative coupling of methane Technical Field The invention belongs to the technical field of ethylene preparation by oxidative coupling of methane, and particularly relates to a heat removal method and a reaction furnace for preparing carbon dioxide by oxidative coupling of methane. Background Natural gas is a widely accepted clean energy source in the world today, one of three fossil energy sources in the world is widely used as industrial and civil fuels, and is also a high-quality chemical raw material, about 95% of methane is contained in the natural gas, and along with the gradual reduction of petroleum resources, the natural gas is a main carbon source of basic chemicals in the future, so that the development and the utilization of the natural gas are increasingly and widely valued worldwide. The technology for preparing ethylene (Oxidative Coupling of Methane, abbreviated as OCM) by oxidative coupling of methane is an important development direction of comprehensive utilization research of natural gas. Since Keller et al first proposed a methane oxidative coupling technology in 1982, the technology has been the focus of attention in the catalytic world, the chemical industry, and the petroleum and natural gas fields. With the breakthrough of the united states in the shale gas field, a large amount of methane which is difficult to mine is mined, and chemical utilization of methane is highly paid attention to the industry, wherein research on oxidative coupling of methane which is considered to be the most promising is once again a research hotspot worldwide. Methane oxidative coupling reactions generally need to be carried out at relatively high temperatures (> 600 ℃) and are strongly exothermic, and hot spot effects generated during the reaction bring about a number of problems for the scale-up and process flow of the project. At present, OCM's studied in the laboratory are generally small in scale and the catalyst loading is usually 0.1-0.8g. When the catalyst loading is increased, the absolute amount of reaction is increased, and the heat release amount is correspondingly increased. Because of the strong exotherm, if no effective heat removal measures are available, most of the reaction heat is absorbed by the reaction mass, which can cause the catalyst bed temperature to rise too fast and the hot spot temperature to be too high, resulting in reaction runaway. Therefore, how to remove the heat generated by the reaction while maintaining the optimization of the C2 yield is the most urgent problem in the methane oxidative coupling process. Disclosure of Invention The invention aims to solve one of the technical problems in the related art to a certain extent, and provides a reaction process for preparing olefin by oxidative coupling of methane, wherein the catalyst loading amount of the reaction process is more than 10 g. The reaction process is different from the general reaction process in that the reaction is started, the methane feeding amount is fixed, the feeding amount is a final preset value, and the oxygen feeding amount is slowly increased. And when the temperature of the hot spot is higher than 750 ℃, carrying out heat removal to ensure that the temperature of the hot spot is kept at 700-730 ℃, continuing to add oxygen, and along with the increase of the oxygen inlet amount, carrying out heat removal to ensure that the temperature of the hot spot is kept at 700-730 ℃ when the temperature of the hot spot is not between 700-730 ℃, so that the final alkoxy ratio reaches 2-4:1, and the temperature of the hot spot is kept at 700-730 ℃. In order to achieve the above object, a first aspect of the present invention provides a heat removal method for preparing a carbon dioxide by oxidative coupling of methane, comprising the steps of: (1) Introducing methane and oxygen into a catalyst bed layer to contact with a catalyst for catalytic reaction, wherein the methane is fed at a constant speed, the oxygen is fed in a gradually increasing manner, and the initial feeding amount is such that the alkoxy ratio is 7-10:1; (2) When the temperature of the hot spot exceeds 750 ℃, carrying out heat removal, reducing the temperature of the hot spot to the range of 700-730 ℃, and stopping heat removal; (3) And continuously increasing the oxygen feeding amount, and when the temperature of the hot spot is higher than 730 ℃, carrying out heat removal to ensure that the temperature of the hot spot is kept in the range of 700-730 ℃ until the reaction is finished. The invention provides a reaction furnace for preparing carbon dioxide by oxidative coupling of methane, which is used for executing a heat removal method for preparing the carbon dioxide by oxidative coupling of methane, and comprises a furnace body, a reaction tube in the furnace body, an insulating layer between the furnace body and the reaction tube and a catalyst bed layer arranged