A method for catalytic coke removal of MOFs precursor perovskite oxide
The catalytic conversion of coke under the action of water vapor through the MOFs precursor perovskite oxide catalyst, which solves the problem of coke removal difficulties during ethylene cracking, and improves the stability and economic benefits of ethylene production.
Patent Information
- Application Number
- CN202311627407.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-30
- Publication Date
- 2025-07-08
- Estimated Expiration
- 2043-11-30
AI Technical Summary
It is difficult to remove coke during ethylene cracking, and existing catalysts are prone to volatilization at high temperatures, causing corrosion of the furnace tube, affecting the production cycle and benefits of ethylene.
The MOFs precursor perovskite oxide is used as a catalyst to perform catalytic conversion by mixing it with coke under the action of water vapor. The preparation process does not require strong acids, alkalis and high pressures, and regulates the morphology and pore structure to achieve high-efficiency coking clearing.
It achieves efficient conversion rate of coke (≥95%), extends the ethylene production cycle, reduces production costs, is environmentally friendly, and has low equipment requirements.
Abstract
Description
Technical Field
[0001] The present invention relates to catalytic coke cleaning in the field of petrochemical industry, and specifically to a method for catalytic coke cleaning using a perovskite oxide of a MOFs precursor. Background Art
[0002] Ethylene is the most important raw material in industrial production, the basis for the production of organic and three major synthetic materials, and also the most important monomer in the petrochemical industry. Therefore, the production of ethylene is the most important link in the petrochemical industry, which not only relates to the efficiency of the petrochemical industry but also represents the development level of a country's chemical industry.
[0003] The common method for producing ethylene is the steam cracking process, with raw materials mainly being naphtha, light diesel, etc. Dehydrogenation or chain-breaking reactions occur in the pyrolysis furnace tubes under high-temperature conditions, and are further converted into products such as ethylene, propylene, and fuel gas. During this process, the process in which coke formed by the cracking of hydrocarbon raw materials accumulates in the furnace tubes is called coking. With the formation of coke, it will lead to a reduction in the cross-sectional area of the ethylene cracking furnace, an increase in the thermal resistance of the furnace tubes, and a decrease in the heat transfer coefficient. At the same pyrolysis furnace tube outlet temperature, a higher wall temperature will be required, the fuel consumption will increase, and phenomena such as furnace tube carburization and local overheating will occur, seriously shortening the service life of the furnace tubes and thus affecting the long-term stable operation of ethylene production.
[0004] The ethylene cracking process is always accompanied by coking and coke cleaning. How to effectively achieve in-situ conversion of coke, and by regulating the reaction between coke and water vapor, catalytically convert coke into carbon oxides and hydrogen is the focus of research. Catalytic conversion does not require air, is convenient to switch, and has simple operation. When reacting with water vapor alone, the coke conversion rate is relatively low, and developing an efficient catalyst is very important for improving coke conversion.
[0005] K2CO3 can be used for catalytic coke cleaning, which improves the coke conversion rate. However, under high-temperature steam cracking, potassium ions are prone to volatilization, causing corrosion of the furnace tubes. Therefore, it is necessary to develop a catalyst with better high-temperature stability.
[0006] It is relatively difficult to remove the coke generated during the ethylene cracking process, and it is necessary to shut down for operation, and the energy consumption during the coke burning process is relatively high. Therefore, in response to the need for coke removal during the ethylene cracking process, the present invention proposes a method for in-situ catalytic coke cleaning using a perovskite oxide of a MOFs precursor, which is of great significance for improving the ethylene production cycle. Summary of the Invention
[0007] The purpose of the present invention is to provide a method for catalytic coke cleaning using a perovskite oxide of a MOFs precursor, which is used to solve the problem that it is relatively difficult to remove the coke generated during the current ethylene cracking process.
[0008] The technical solution adopted by the present invention to solve its technical problems is as follows: This method for catalytic coking removal of MOFs precursor perovskite oxide includes the following steps:
[0009] Step 1: Dissolve alkaline earth metal nitrate A and rare earth metal nitrate R in a certain volume of ethanol solution. Dissolve transition metal potassium cyanide T in a certain volume of ethanol solution. Mix the two solutions and stir evenly. Adjust the pH value of the solution by adding ammonia water. After aging at room temperature, perform vacuum filtration and freeze-drying to obtain a ternary metal MOFs precursor; the molar ratio of the three metal salts is R:A:T = (0.9 - x ): x :1 (0.05 ≤ x ≤ 0.90);
[0010] Step 2: Calcinate the ternary metal MOFs precursor obtained in Step 1 to prepare a perovskite oxide with adjustable morphology, specific surface area, and pore structure. The perovskite oxide is the MOFs precursor perovskite oxide;
[0011] Step 3: Use the MOFs precursor perovskite oxide for the catalytic conversion of coke and steam to achieve efficient coking removal. Add a mixture of the MOFs precursor perovskite oxide and coke to a tubular furnace, introduce steam for reaction, and the equilibrium pressure gas is an inert gas. The addition amount of the MOFs precursor perovskite oxide is 1.0% - 10.0% of the mass of coke, the mass ratio of coke to steam is 1:30 - 1:120, and the coke conversion rate ≥ 95%.
[0012] In the above solution, the alkaline earth metal nitrate A is one of calcium nitrate, magnesium nitrate, and barium nitrate; the rare earth metal nitrate R is one of praseodymium nitrate, neodymium nitrate, and samarium nitrate; the transition metal potassium cyanide T is one of manganese potassium cyanide, cobalt potassium cyanide, and nickel potassium cyanide.
[0013] In Step 1 of the above solution, the concentrations of the alkaline earth metal nitrate A, rare earth metal nitrate R, and transition metal potassium cyanide T solutions are 2.5 mmol / L - 12.5 mmol / L, the mass fraction of ethanol in the solution is 33wt.% - 67wt.%, the pH value of the solution is adjusted to 6 - 9, and aging is carried out at room temperature for 6h - 36h.
[0014] In the above solution, the calcination conditions are as follows: in an air atmosphere, the heating rate is 0.5°C / min - 10°C / min, the calcination temperature is 500°C - 700°C, and the calcination time is 0.5 h - 6h.
[0015] In Step 3 of the above solution, the steam partial pressure is 1.0×10 4 Pa - 4.0×10 4Pa, the mass flow rate of water vapor is 0.025 g / min - 0.267 g / min; the reaction temperature is 700 °C - 1000 °C, and the reaction time is 40 min - 160 min.
[0016] The present invention has the following beneficial effects:
[0017] 1. The present invention utilizes MOFs precursors to prepare perovskite oxides for catalyzing the reaction of coke with water vapor, realizing the efficient conversion of coke, solving the bottleneck problems of easy coking and difficult removal in the current ethylene cracking process, and is of great significance for improving the ethylene production cycle.
[0018] 2. The perovskite oxides prepared by the present invention have good high-temperature stability and high purity; the morphology, specific surface area, and pore structure can be regulated.
[0019] 3. The process does not involve toxic substances, is environmentally friendly and pollution-free; strong acids and bases are not used during the reaction process, high-pressure operation is not required, the reaction conditions are mild, and the requirements for equipment are low; the raw materials are widely available, the catalyst regeneration process is simple, the service life is long, the production cost is low, and the economic benefits are good. Embodiment
[0020] The following further describes the present invention: Example
[0021] Weigh 0.0653 g of Pr(NO3)3•6H2O and 0.1231 g of Ca(NO3)2 and dissolve them in 80 mL of an ethanol solution with a mass fraction of 40 wt.%, and stir until dissolved. Weigh 0.3323 g of K3Co(CN)6 and dissolve it in 80 mL of an ethanol solution with a mass fraction of 40 wt.%, and stir until dissolved. Mix the two solutions evenly, adjust the pH value of the solution to 8.0 by adding ammonia water, age it at room temperature for 12 h, then perform vacuum filtration and freeze-drying to prepare the MOFs precursor; put the MOFs precursor into a muffle furnace, heat it to 600 °C at a rate of 8 °C / min by passing air, and calcine for 6 h; after the sample is cooled to room temperature, Pr 0.15 Ca 0.75 CoO3 is obtained and ground with a ball mill.
[0022] Weigh 0.20 g of coke and 0.01 g of Pr 0.15 Ca 0.75 CoO3 and put them into a mortar and grind until uniform. The Pr prepared in this example 0.15 Ca 0.75A homogeneous mixture of 0.21 g of CoO3 and coke was added to a fixed-bed tubular furnace reactor for reaction. Under an inert atmosphere, the temperature was programmed to rise to 900 °C, the mass flow rate of the introduced steam was 0.167 g / min, the reaction time was 120 min, the solid after the reaction was 0.019 g, and the coke conversion rate was 95.5%.
[0023] Perovskite-type (ABO3) oxides have good ability to transfer O 2- and electrons, and at the same time have high chemical stability and low cost. By doping metal cations at the A site, the valence state of the metal at the B site can be modulated, and then a large number of oxygen vacancies are generated to form an O 2- transfer path to promote the transfer of O 2- . Example
[0024] Weighed 0.1523 g of Pr(NO3)3•6H2O and 0.0902 g of Ca(NO3)2 were dissolved in 80 mL of an ethanol solution with a mass fraction of 50 wt.%, and stirred until dissolved. Weighed 0.3323 g of K3Co(CN)6 was dissolved in 80 mL of an ethanol solution with a mass fraction of 50 wt.%, and stirred until dissolved. The two solutions were mixed evenly, and the pH value of the solution was adjusted to 8.0 by adding ammonia water. It was aged at room temperature for 12 h, then subjected to vacuum filtration and freeze-drying to prepare the MOFs precursor; the MOFs precursor was put into a muffle furnace, and air was introduced and heated to 600 °C at a rate of 6 °C / min and calcined for 6 h; after the sample was cooled to room temperature, Pr 0.35 Ca 0.55 CoO3 was obtained and pulverized with a ball mill.
[0025] Weighed 0.20 g of ethylene cracking furnace coke and 0.01 g of Pr 0.35 Ca 0.55 CoO3 were put into a mortar and ground until homogeneous. The homogeneous mixture of 0.21 g of Pr 0.35 Ca 0.55 CoO3 and coke prepared in this example was added to a fixed-bed tubular furnace reactor for reaction. Under an inert atmosphere, the temperature was programmed to rise to 900 °C, the mass flow rate of the introduced steam was 0.167 g / min, the reaction time was 120 min, the solid after the reaction was 0.018 g, and the coke conversion rate was 96%. Example
[0026] Weigh 0.2393 g of Pr(NO3)3•6H2O and 0.0574 g of Ca(NO3)2, dissolve them in 80 mL of ethanol solution with a mass fraction of 50 wt.%, and stir until dissolved. Weigh 0.3323 g of K3Co(CN)6 and dissolve it in 80 mL of ethanol solution with a mass fraction of 50 wt.%, and stir until dissolved. Mix the two solutions evenly, adjust the pH value of the solution to 8.5 by adding ammonia water, age it at room temperature for 12 h, then carry out vacuum filtration and freeze-drying to prepare the MOFs precursor; put the MOFs precursor into a muffle furnace, heat it to 600 °C at a rate of 4 °C / min while passing air, and calcine for 6 h; after the sample is cooled to room temperature, Pr 0.55 Ca 0.35 CoO3 is obtained and crushed by a ball mill.
[0027] Weigh 0.20 g of ethylene cracking furnace coke and 0.01 g of Pr 0.55 Ca 0.35 CoO3 and put them into a mortar and grind until uniform. Take 0.21 g of the uniform mixture of Pr 0.55 Ca 0.35 CoO3 and coke prepared in this example, add them to a fixed-bed tubular furnace reactor for reaction, program the temperature to 900 °C under an inert atmosphere, pass in steam with a mass flow rate of 0.167 g / min, and the reaction time is 120 min. After the reaction, the solid is 0.016 g, and the coke conversion rate is 97%. Example
[0028] Weigh 0.3263 g of Pr(NO3)3•6H2O and 0.0246 g of Ca(NO3)2, dissolve them in 80 mL of ethanol solution with a mass fraction of 40 wt.%, and stir until dissolved. Weigh 0.3323 g of K3Co(CN)6 and dissolve it in 80 mL of ethanol solution with a mass fraction of 40 wt.%, and stir until dissolved. Mix the two solutions evenly, adjust the pH value of the solution to 8.5 by adding ammonia water, age it at room temperature for 12 h, then carry out vacuum filtration and freeze-drying to prepare the MOFs precursor; put the MOFs precursor into a muffle furnace, heat it to 600 °C at a rate of 4 °C / min while passing air, and calcine for 6 h; after the sample is cooled to room temperature, Pr 0.75 Ca 0.15 CoO3 is obtained and crushed by a ball mill.
[0029] Weigh 0.20 g of ethylene cracking furnace coke and 0.01 g of Pr 0.75 Ca 0.15 CoO3 and put them into a mortar and grind until uniform. Take the Pr 0.75 Ca 0.150.21 g of a homogeneous mixture of CoO3 and coke was added to a fixed-bed tubular furnace reactor for reaction. Under an inert atmosphere, the temperature was programmed to rise to 900 °C, and steam with a mass flow rate of 0.167 g / min was introduced. The reaction time was 120 min. After the reaction, the solid was 0.017 g, and the coke conversion rate was 96.5%. Example
[0030] 0.3263 g of Pr(NO3)3•6H2O and 0.0392 g of Ba(NO3)2 were weighed and dissolved in 80 mL of an ethanol solution with a mass fraction of 50 wt.%. The solution was stirred until dissolved to obtain solution S1; 0.3323 g of K2Co(CN)6 was dissolved in 80 mL of an ethanol solution with a mass fraction of 50 wt.%, and the solution was stirred until dissolved to obtain solution S2. Solution S2 was added to solution S1 under rapid stirring, and the solution was mixed evenly. The pH value of the solution was adjusted to 7.5 by adding ammonia water, and it was aged at room temperature for 12 h, then subjected to vacuum filtration and freeze-drying to prepare the MOFs precursor; the MOFs precursor was placed in a muffle furnace, and air was introduced to heat it to 600 °C at a rate of 4 °C / min and calcined for 6 h; after the sample was cooled to room temperature, Pr 0.75 Ba 0.15 CoO3 was obtained and pulverized with a ball mill.
[0031] 0.20 g of ethylene cracking furnace coke and 0.01 g of Pr 0.75 Ba 0.15 CoO3 were placed in a mortar and ground until homogeneous. The Pr 0.75 Ba 0.15 CoO3 and 0.21 g of a homogeneous mixture of coke were added to a fixed-bed tubular furnace reactor for reaction. Under an inert atmosphere, the temperature was programmed to rise to 900 °C, and steam with a mass flow rate of 0.167 g / min was introduced. The reaction time was 120 min. After the reaction, the solid was 0.013 g, and the coke conversion rate was 98.5%.
[0032] In view of the characteristics of easy coking in the ethylene production process, the present invention proposes a method for using MOFs precursor perovskite oxide in the catalytic conversion reaction of coke and steam, which can in-situ realize the catalytic conversion of the generated coke and achieve efficient coke cleaning.
Claims
1. A method for catalytic coke cleaning of MOFs precursor perovskite oxides, characterized in that It includes the following steps: Weigh 0.3263 g of Pr(NO3)3•6H2O and 0.0392 g of Ba(NO3)2, dissolve them in 80 mL of ethanol solution with a mass fraction of 50 wt.%, stir until dissolved, and obtain solution S1; weigh 0.3323 g of K2Co(CN)6 and dissolve it in 80 mL of ethanol solution with a mass fraction of 50 wt.%, stir until dissolved, and obtain solution S2; add solution S2 to solution S1, mix the solutions evenly, adjust the pH value of the solution to 7.5 by adding ammonia water, age at room temperature for 12 h, then carry out vacuum filtration and freeze-drying to prepare the MOFs precursor; put the MOFs precursor into a muffle furnace, introduce air, heat it to 600 °C at a rate of 4 °C / min, and calcine for 6 h; after the sample is cooled to room temperature, obtain Pr 0.75 Ba 0.15 CoO3, and crush it with a ball mill; Weigh 0.20 g of ethylene cracking furnace coke and 0.01 g of Pr 0.75 Ba 0.15 CoO3 into a mortar, grind until uniform, add it to a fixed-bed tubular furnace reactor for reaction, program the temperature to 900 °C under an inert atmosphere, introduce steam with a mass flow rate of 0.167 g / min, the reaction time is 120 min, the solid after the reaction is 0.013 g, and the coke conversion rate is 98.5%.