Methane oxidative coupling method and method for improving conversion rate and selectivity of methane oxidative coupling reaction
By introducing a feed gas containing a lanthanum catalyst, including methane, water, and CO2, into the methane oxidative coupling reactor, the problems of catalyst bed temperature rise and poor initial performance were solved, thereby improving catalyst stability and reaction efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-04
- Publication Date
- 2026-05-08
AI Technical Summary
In the oxidative coupling reaction of methane, the temperature rise in the catalyst bed leads to reaction instability, poor initial catalyst performance, and affects plant efficiency.
Feed gas, including methane, water, CO2 and oxygen-containing gas, is introduced into the reactor containing lanthanum catalyst. The CO2 molar concentration is above 1 mol%, preferably 1-5 mol%, to reduce the hot spot temperature of the catalyst bed and improve the initial reaction activity and conversion rate.
Extend catalyst lifespan, improve initial methane conversion and selectivity for C2 and above hydrocarbons, and further enhance conversion and selectivity during stable operation.
Smart Images
Figure BDA0005118532710000071 
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Abstract
Description
Technical Field
[0001] This invention relates to the field of methane oxidative coupling technology, specifically to a method for methane oxidative coupling and a method for improving the conversion rate and selectivity of the methane oxidative coupling reaction. Background Technology
[0002] The oxidative coupling of methane to ethylene and ethane is one of the most challenging and closely watched research topics in the field of catalysis due to its academic significance and potential for enormous economic value. Since its initial report in 1982 by Keller and Bhasin, it has been a focus of attention in catalysis, the chemical industry, and the oil and gas sector. Methane oxidative coupling is an exothermic reaction, and the main products are ethylene, ethane, and water. This technology is characterized by good atom economy and environmental friendliness, making it a target of intense research by scientific researchers and major corporations for the past four decades.
[0003] Because the oxidative coupling reaction of methane involves high temperatures, the catalyst bed experiences a significant temperature rise during the reaction. Furthermore, the initial performance of the catalyst is poor, requiring a considerable reaction time to reach a stable state. Therefore, in the industrialization of methane oxidative coupling, the high catalyst bed temperature leads to reaction instability, and the poor initial catalyst performance results in poor plant efficiency. Summary of the Invention
[0004] The purpose of this invention is to overcome the problems of catalyst bed temperature rise and poor initial catalyst performance in the prior art. This invention provides a method for methane oxidative coupling and a method for improving the conversion rate and selectivity of the methane oxidative coupling reaction.
[0005] To achieve the above objectives, a first aspect of the present invention provides a method for methane oxidative coupling, the method comprising: introducing a feed gas into a reactor packed with a lanthanum-containing catalyst to carry out a methane oxidative coupling reaction, wherein the feed gas includes methane, water, CO2 and an oxygen-containing gas, and the molar concentration of CO2 introduced is above 1 mol%, preferably 1-5 mol%, based on the total molar concentration of the feed gas.
[0006] A second aspect of the present invention provides a method for improving the conversion rate and selectivity of methane oxidative coupling reaction, the method comprising: introducing a feed gas into a reactor packed with a lanthanum-containing catalyst to carry out a methane oxidative coupling reaction, wherein the feed gas includes methane, water, CO2 and an oxygen-containing gas, and the molar concentration of CO2 introduced is above 1 mol%, preferably 1-5 mol%, based on the total molar concentration of the feed gas.
[0007] Through the above technical solution, the present invention achieves the following beneficial effects:
[0008] The method of this invention can reduce the hot spot temperature of the catalyst bed and extend the catalyst's lifespan. It can also improve the initial reactivity of the methane coupling reaction, increasing the initial conversion of methane and the initial selectivity for C2 and higher hydrocarbons. Preferably, the method of this invention can also improve the conversion of methane and the selectivity for C2 and higher hydrocarbons during stable operation. Detailed Implementation
[0009] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0010] The first aspect of the present invention provides a method for methane oxidative coupling, the method comprising: introducing a feed gas into a reactor packed with a lanthanum-containing catalyst to carry out a methane oxidative coupling reaction, wherein the feed gas includes methane, water, CO2 and an oxygen-containing gas, and the molar concentration of CO2 introduced is above 1 mol%, preferably 1-5 mol%, based on the total molar concentration of the feed gas.
[0011] The inventors of this invention discovered that simultaneously introducing water and CO2 at the start of the methane oxidative coupling reaction can reduce the hot spot temperature of the catalyst bed, extend the catalyst's lifespan, and facilitate industrial scale-up. It can also improve the initial reactivity of the methane coupling reaction, increase the initial conversion rate of methane and the initial selectivity for C2 and higher hydrocarbons, and prevent deep oxidation of the product ethylene.
[0012] According to the present invention, preferably, when the difference between the molar concentration of CO2 in the reactor and the amount of CO2 introduced into the feed gas is 0.01-5 mol% (the difference can be 0.01 mol, 0.1 mol, 0.2 mol, 0.3 mol, 0.4 mol, 0.5 mol, 1 mol, 2 mol, 3 mol, 4 mol, 5 mol, or any two of the above), the introduction of CO2 is stopped.
[0013] According to the present invention, preferably, the lanthanum-containing catalyst comprises at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum oxycarbonate.
[0014] According to the present invention, preferably, the molar ratio of methane to water is 1:1-5, more preferably 1:2-5.
[0015] According to the present invention, preferably, the molar ratio of methane to oxygen-containing gas is 2-10:1, more preferably 2-8:1.
[0016] According to the present invention, preferably, in the oxidative coupling reaction, the reaction space velocity, based on methane, is 5000-200000 ml / gh.
[0017] According to the present invention, preferably, the temperature of the reaction is 500-750°C, more preferably 500-700°C.
[0018] According to the present invention, preferably, the upper end of the reactor containing the lanthanum catalyst is filled with quartz wool. In this invention, the feed gas is introduced from the end filled with quartz wool.
[0019] According to the present invention, preferably, the filling height of the quartz wool in the reactor is 1-5 mm.
[0020] According to the present invention, preferably, the water is introduced into the reactor in liquid form. The water is injected at a location aligned with the airflow direction, approximately 1-2 mm from the top of the quartz wool.
[0021] A second aspect of the present invention provides a method for improving the conversion rate and selectivity of methane oxidative coupling reaction, the method comprising: introducing a feed gas into a reactor packed with a lanthanum-containing catalyst to carry out a methane oxidative coupling reaction, wherein the feed gas includes methane, water, CO2 and an oxygen-containing gas, and the molar concentration of CO2 introduced is above 1 mol%, preferably 1-5 mol%, based on the total molar concentration of the feed gas.
[0022] According to a particularly preferred embodiment of the present invention, the method includes: loading a catalyst (lanthanum oxycarbonate) into a quartz tube reactor, with quartz wool filling the upper end of the catalyst, the catalyst filling height being 20-22 mm, and the quartz wool filling height being 2.5-3 mm. At the start of the reaction, methane, deionized water, CO2, and oxygen are introduced into the quartz tube reactor, wherein the reaction space velocity (USV) based on methane is 45000-50000 ml / gh, the molar ratio of methane to oxygen is 4-5:1, deionized water is injected 1-1.2 mm above the quartz wool, the molar ratio of methane to deionized water is 1:2-2.2, and the amount of CO2 introduced is such that the initial molar concentration of CO2 in the quartz tube reactor is 1-1.2 mol%. When the reaction reaches a steady state, i.e., when the molar concentration of CO2 in the reactor is above 2.1-2.3 mol%, the introduction of CO2 is stopped.
[0023] The present invention will be described in detail below through embodiments. In the following embodiments,
[0024] The method for calculating methane conversion rate is as follows:
[0025] Methane conversion rate = Amount of methane consumed in the reaction / Initial amount of methane × 100%.
[0026] The method for calculating ethylene selectivity is as follows:
[0027] Ethylene selectivity = Amount of methane consumed to produce ethylene / Total methane consumption × 100%.
[0028] The method for calculating ethane selectivity is as follows:
[0029] Ethane selectivity = Amount of methane consumed to produce ethane / Total methane consumption × 100%.
[0030] The selectivity of C2 and above hydrocarbons includes ethylene, ethane, propylene, propane, and the sum of higher carbon hydrocarbons.
[0031] Example 1
[0032] A quartz tube reactor (8 mm inner diameter) was filled with 1 g of catalyst (lanthanum oxycarbonate). Quartz wool was packed at the top of the catalyst to a height of 20 mm, and the quartz wool to a height of 3 mm. At the start of the reaction, methane, deionized water, CO2, and oxygen were introduced into the reactor. The reaction space velocity (USV) for methane was 50,000 ml / gh, and the molar ratio of methane to oxygen was 5:1. Deionized water was injected 1 mm above the quartz wool, and the molar ratio of methane to deionized water was 1:2. The amount of CO2 introduced resulted in an initial molar concentration of 1 mol% in the reactor. When the reaction reached a steady state, i.e., when the molar concentration of CO2 in the reactor was above 2.1 mol%, the introduction of CO2 was stopped. The time t from the start of the reaction to the cessation of CO2 introduction was recorded. The hot spot temperature of the catalyst bed, the set reaction temperature, the initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons, and the methane conversion rate and the selectivity of C2 and above hydrocarbons after 4 hours of reaction are shown in Table 1. The initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons represent the methane conversion rate and the selectivity of C2 and above hydrocarbons, respectively, from the start of the reaction until the CO2 introduction is stopped.
[0033] Example 2
[0034] A quartz tube reactor (8 mm inner diameter) was filled with 1 g of catalyst (lanthanum oxycarbonate). Quartz wool was packed at the top of the catalyst to a height of 20 mm, and the quartz wool to a height of 5 mm. At the start of the reaction, methane, deionized water, CO2, and oxygen were introduced into the reactor. The reaction space velocity (USV) for methane was 100,000 ml / gh, and the molar ratio of methane to oxygen was 6:1. Deionized water was injected 2 mm above the quartz wool, and the molar ratio of methane to deionized water was 1:3. The amount of CO2 introduced ensured an initial CO2 concentration of 1 mol% in the reactor. When the reaction reached a steady state, i.e., when the CO2 concentration in the reactor exceeded 2.5 mol%, the introduction of CO2 was stopped. The time t from the start of the reaction to the cessation of CO2 introduction was recorded. The hot spot temperature of the catalyst bed, the set reaction temperature, the initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons, and the methane conversion rate and the selectivity of C2 and above hydrocarbons after 4 hours of reaction are shown in Table 1. The initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons represent the methane conversion rate and the selectivity of C2 and above hydrocarbons, respectively, from the start of the reaction until the CO2 introduction is stopped.
[0035] Example 3
[0036] A quartz tube reactor (8 mm inner diameter) was filled with 1 g of catalyst (lanthanum oxycarbonate). Quartz wool was packed at the top of the catalyst to a height of 20 mm, and the quartz wool to a height of 4 mm. At the start of the reaction, methane, deionized water, CO2, and oxygen were introduced into the reactor. The reaction space velocity (USV) for methane was 120,000 ml / gh, and the molar ratio of methane to oxygen was 8:1. Deionized water was injected 1.5 mm above the quartz wool, and the molar ratio of methane to deionized water was 1:2.5. The amount of CO2 introduced resulted in an initial CO2 concentration of 2 mol% in the reactor. When the reaction reached a steady state, i.e., when the CO2 concentration in the reactor exceeded 3.5 mol%, the introduction of CO2 was stopped. The time t from the start of the reaction to the cessation of CO2 introduction was recorded. The hot spot temperature of the catalyst bed, the set reaction temperature, the initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons, and the methane conversion rate and the selectivity of C2 and above hydrocarbons after 4 hours of reaction are shown in Table 1. The initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons represent the methane conversion rate and the selectivity of C2 and above hydrocarbons, respectively, from the start of the reaction until the CO2 introduction is stopped.
[0037] Example 4
[0038] A quartz tube reactor (8 mm inner diameter) was filled with 1 g of catalyst (lanthanum oxycarbonate). Quartz wool was packed at the top of the catalyst to a height of 20 mm, and the quartz wool to a height of 5 mm. At the start of the reaction, methane, deionized water, CO2, and oxygen were introduced into the reactor. The reaction space velocity (USV) for methane was 40,000 ml / gh, and the molar ratio of methane to oxygen was 7:1. Deionized water was injected 2 mm above the quartz wool, and the molar ratio of methane to deionized water was 1:4. The amount of CO2 introduced resulted in an initial CO2 molar concentration of 2 mol% in the reactor. When the reaction reached a steady state, i.e., when the CO2 concentration in the reactor exceeded 4.1 mol%, the introduction of CO2 was stopped. The time t from the start of the reaction to the cessation of CO2 introduction was recorded. The hot spot temperature of the catalyst bed, the set reaction temperature, the initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons, and the methane conversion rate and the selectivity of C2 and above hydrocarbons after 4 hours of reaction are shown in Table 1. The initial methane conversion rate and the initial selectivity of C2 and above hydrocarbons represent the methane conversion rate and the selectivity of C2 and above hydrocarbons, respectively, from the start of the reaction until the CO2 introduction is stopped.
[0039] Example 5
[0040] The procedure was carried out according to Example 1, except that the lanthanum oxycarbonate catalyst was replaced with lanthanum oxide.
[0041] Example 6
[0042] The method was carried out according to Example 1, except that the amount of CO2 introduced was such that the initial concentration of CO2 in the quartz tube reactor was 10 mol%; when the reaction reached a steady state, that is, when the molar concentration of CO2 in the reactor was above 15 mol%, the introduction of CO2 was stopped.
[0043] Example 7
[0044] The procedure was carried out according to Example 1, except that the molar ratio of methane to deionized water was 1:1.
[0045] Comparative Example 1
[0046] The procedure was carried out according to Example 1, except that deionized water was not introduced.
[0047] Comparative Example 2
[0048] The procedure was carried out according to Example 1, except that CO2 was not introduced.
[0049] Comparative Example 3
[0050] The procedure was carried out according to Example 1, except that deionized water and CO2 were not introduced.
[0051] Comparative Example 4
[0052] The method of Example 1 was followed, except that the lanthanum oxycarbonate catalyst was replaced with a Li-MgO catalyst, wherein the Li content was 6% by weight based on MgO.
[0053] Table 1
[0054]
[0055]
[0056] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for oxidative coupling of methane, characterized in that, The method includes: introducing a feed gas into a reactor packed with a lanthanum-containing catalyst to carry out a methane oxidative coupling reaction, wherein the feed gas includes methane, water, CO2 and an oxygen-containing gas, and the CO2 molar concentration introduced is above 1 mol%, preferably 1-5 mol%, based on the total molar concentration of the feed gas.
2. The method according to claim 1, wherein, When the difference between the molar concentration of CO2 in the reactor and the amount of CO2 introduced into the feed gas is 0.01-5 mol%, the introduction of CO2 should be stopped.
3. The method according to claim 1, wherein, The lanthanum-containing catalyst includes at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum oxycarbonate.
4. The method according to claim 1, wherein, The molar ratio of methane to water is 1:1-5, preferably 1:2-5.
5. The method according to claim 1, wherein, The water is introduced into the reactor in liquid form.
6. The method according to claim 1, wherein, The molar ratio of methane to oxygen-containing gas is 2-10:1, preferably 2-8:
1.
7. The method according to claim 1, wherein, In oxidative coupling reactions, the reaction space velocity (USV) based on methane is 5000-200000 ml / gh.
8. The method according to claim 1, wherein, The reaction temperature is 500-750℃, preferably 500-700℃.
9. The method according to claim 1, wherein, In the reactor, the upper end of the lanthanum-containing catalyst is filled with quartz wool; More preferably, the filling height of the quartz wool is 1-5mm.
10. A method for improving the conversion rate and selectivity of methane oxidative coupling reaction, characterized in that, The method includes: introducing a feed gas into a reactor packed with a lanthanum-containing catalyst to carry out a methane oxidative coupling reaction, wherein the feed gas includes methane, water, CO2 and an oxygen-containing gas, and the CO2 molar concentration introduced is above 1 mol%, preferably 1-5 mol%, based on the total molar concentration of the feed gas.