Method for preparing propylene through capture and in-situ conversion of carbon dioxide in high-temperature flue gas

Abstract

The invention belongs to the field of inorganic membranes and chemical engineering, and particularly relates to a method for preparing propylene through capture and in-situ conversion of carbon dioxide in high-temperature flue gas. The method comprises the following steps: introducing high-temperature flue gas into a supply side of a ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, introducing propane gas into a reaction side of the membrane reactor, permeating carbon dioxide from the supply side to the reaction side, and reacting with propane on the reaction side under the action of a catalyst to generate propylene. The ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor is utilized to simultaneously realize high-temperature capture and in-situ conversion of flue gas carbon dioxide, capture and utilization of carbon dioxide are realized, the separation and purification cost of carbon dioxide is reduced, oxide slowly permeates through the gas separation membrane, the reaction carbon deposition phenomenon can be slowed down, and the separation and purification efficiency of carbon dioxide is improved. The service life of the catalyst is prolonged and the propane oxidative dehydrogenation reaction efficiency is improved. The method can be applied to capture of carbon in coal-fired power plant tail gas or chemical plant combustion tail gas, and the carbon is converted into propylene with more added value in situ.

Description

Technical Field

[0001] The invention belongs to the field of inorganic membranes and chemical industry, and specifically relates to a method for capturing carbon dioxide in high-temperature flue gas and converting it in situ to produce propylene. Background Art

[0002] Propylene is one of the important basic chemical raw materials and the second largest chemical raw material after ethylene. In recent years, my country's demand and output of propylene have increased year by year. However, the traditional cracking method has high energy consumption and strong dependence on oil, and it is necessary to seek a more efficient new propylene preparation. Propane dehydrogenation to propylene is a clean and efficient propylene preparation technology, which has attracted widespread attention in recent years. At present, propane dehydrogenation is divided into oxidative dehydrogenation and direct dehydrogenation. Compared with direct dehydrogenation, oxidative dehydrogenation has a high conversion rate and is an exothermic reaction. It can be operated at a lower temperature, so the energy consumption is lower. In addition, the reaction has better resistance to carbon deposition in the presence of an oxidant. It is considered to be one of the more promising propylene preparation technologies. However, the propylene selectivity of this reaction is low, and the catalyst is easily deactivated. Therefore, how to efficiently realize the propane-to-propylene reaction, how to select an oxidant and extend the catalyst life have become the research focus in recent years.

[0003] Carbon dioxide is a mild oxidant. Using carbon dioxide to oxidize and dehydrogenate propane can inhibit its deep oxidation and improve the selectivity of propylene. Carbon dioxide is also a major greenhouse gas. Directly capturing high-temperature flue gas from industrial gas sources and reacting carbon dioxide in situ to produce value-added chemicals is one of the effective ways to achieve "carbon neutrality". Summary of the invention

[0004] The purpose of the present invention is to provide a method for capturing carbon dioxide in high-temperature flue gas and converting it in situ to produce propylene, which combines the capture of carbon dioxide in high-temperature flue gas with the process of producing propylene by propane dehydrogenation reaction using a ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, and completes the capture of flue gas carbon and in-situ conversion to produce propylene with added value in one step. This method not only improves the capture and conversion efficiency, but also the membrane reactor can effectively slow down the reaction carbon deposition phenomenon and improve the stability and life of the catalyst.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] The present invention provides a method for capturing carbon dioxide in high-temperature flue gas and converting it in situ to produce propylene. The high-temperature flue gas is introduced into the supply side of a ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, and propane gas is introduced into the reaction side of the membrane reactor. Carbon dioxide permeates from the supply side to the reaction side and reacts with propane on the reaction side under the action of a catalyst to produce propylene.

[0007] In the above technical solution, further, in the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, the membrane material is composed of a porous oxygen ion ceramic skeleton and a multi-component molten carbonate filled therein.

[0008] In the above technical solution, further, the porous oxygen ion ceramic skeleton includes one of samarium oxide doped cerium oxide material, gadolinium oxide doped cerium oxide material, and yttria stabilized zirconia.

[0009] In the above technical solution, further, the multi-component molten carbonate is composed of at least two of Li2CO3, Na2CO3, and K2CO3.

[0010] In the above technical solution, further, the porous oxygen ion ceramic skeleton has a porosity of 30-60% and a pore size of 1-20 μm.

[0011] In the above technical solution, further, in the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, the catalyst includes one of a vanadium-based catalyst, a chromium-based catalyst, and a molybdenum-based catalyst, wherein the carrier includes one of an oxide, a zeolite, a molecular sieve, and a metal-organic framework.

[0012] In the above technical solution, further, the operating temperature in the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor is 500-900°C.

[0013] In the above technical solution, further, the configuration of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor is a flat plate type or a tubular type.

[0014] The beneficial effects of the present invention are:

[0015] The present invention utilizes a ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor to simultaneously achieve high-temperature capture and in-situ conversion of flue gas carbon dioxide, as well as propane oxidative dehydrogenation to produce propylene, thereby achieving capture and utilization of carbon dioxide and reducing the cost of separation and purification of carbon dioxide. At the same time, the oxide slowly permeates through the gas separation membrane, which can slow down the reaction carbon deposition phenomenon, extend the life of the catalyst, and improve the efficiency of the propane oxidative dehydrogenation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a working principle diagram of the method for capturing carbon dioxide in high-temperature flue gas and converting it in situ to produce propylene in the present invention;

[0017] Figure 2 The microscopic morphology of the membrane material of Example 1, a is the cross-sectional microscopic morphology of the porous ceramic skeleton, and b is the cross-sectional microscopic morphology after being filled with multi-component molten salt;

[0018] Figure 3The performance test results of Example 1, a is the conversion rate of propane, the selectivity and yield of propylene, and b is the permeation flux of carbon dioxide. DETAILED DESCRIPTION

[0019] The present invention will be further described in the following examples, but the present invention is not limited thereto.

[0020] In the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor of the present invention, the membrane is in the form of a sheet or a tube.

[0021] In a specific embodiment, the catalyst of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor includes but is not limited to one of a vanadium-based catalyst, a chromium-based catalyst, and a molybdenum-based catalyst, wherein the carrier includes but is not limited to oxides (Al2O3, SiO2, TiO2, CeO2, ZrO2 and MgO), zeolite, molecular sieve, metal organic framework material; the preparation method of the catalyst includes but is not limited to impregnation method, precipitation method, ion exchange method, gas phase synthesis method, blending method, sol-gel method, combustion method and hydrothermal method; the loading method of the catalyst includes but is not limited to particle filling, membrane surface impregnation, coating or vapor deposition;

[0022] The membrane material of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor is composed of a porous oxygen ion ceramic skeleton and a multi-component molten carbonate filled therein, wherein the porous ceramic skeleton material includes but is not limited to one of samarium oxide-doped cerium oxide, gadolinium oxide-doped cerium oxide, yttria-stabilized zirconia, and scandium oxide-stabilized zirconia. Its preparation method includes but is not limited to solid phase synthesis, coprecipitation, sol-gel method, combustion method, and hydrothermal method. The pore-forming agent includes but is not limited to carbon black, spherical graphite, sodium bicarbonate, ammonium bicarbonate or starch; the molding process includes but is not limited to dry pressing and isostatic pressing; the preparation method of the multi-component molten carbonate includes but is not limited to mechanical mixing method and solid phase synthesis method.

[0023] The method for capturing carbon dioxide in high-temperature flue gas and converting it in situ to produce propylene using the above-mentioned ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor is as follows:

[0024] High-temperature flue gas is introduced into the supply side of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, and propane and argon carrier gas are introduced into the reaction side of the membrane reactor. At the same time, a heating furnace is used to heat the membrane reactor to the operating temperature. During the reaction, carbon dioxide permeates from the supply side to the reaction side driven by the carbon dioxide partial pressure on both sides, and undergoes oxidative dehydrogenation reaction with the propane on the reaction side to generate the main product propylene and by-products. All the outlet gases are dried and then enter the gas chromatograph for content analysis of each component.

[0025] In the following examples, a mixed gas of carbon dioxide and nitrogen (wherein carbon dioxide accounts for 40% by volume and nitrogen accounts for 60% by volume) is used as simulated flue gas.

[0026] Example 1

[0027] The membrane material of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor in this embodiment is Sm 0.2 Ce 0.8 O 1.9 The powder (particle size is about 2-4 μm) and the molar ratio of 52:48 Li2CO3 and Na2CO3 binary molten carbonate are composed. The film shape is a sheet film with an effective area of ​​1 cm 2 , with a thickness of 0.75 mm; Cr / SiO2 (about 0.42 g) catalyst was pelletized and placed in the membrane reactor near the membrane reaction side surface, and 50 mL min was passed through the membrane supply side. -1 Simulated flue gas, 30 mL min was introduced into the reaction side -1 A mixture of propane and argon (propane accounts for 3.5% by volume).

[0028] The carbon dioxide capture and conversion performance of Example 1 is as follows Figure 3 As shown in Figure 2, at 675 °C, the propane conversion rate was 49.93%, the propylene selectivity and yield were 61.99% and 30.95%, and the CO2 permeation flux was about 0.5 ml min -1 cm -2 .

[0029] Example 2

[0030] The membrane material of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor in this embodiment is Sm 0.2 Ce 0.8 O 1.9 The powder (particle size is about 2-4 μm) and the molar ratio of 52:48 Li2CO3 and Na2CO3 binary molten carbonate are composed. The film shape is a sheet film with an effective area of ​​1 cm 2 Cr / SiO2 (about 0.42 g) catalyst was pelletized and placed in the membrane reactor near the membrane reaction side surface; 50 mL min was passed into the membrane supply side. -1 Simulated flue gas, 30 mL min was introduced into the reaction side -1 A mixture of propane and argon (propane accounts for 2.5% by volume). At 675°C, the propane conversion rate is 28.94%, the propylene selectivity and yield are 48.93% and 14.16%, and the CO2 permeation flux is about 0.84 ml min -1 cm -2 .

[0031] Example 3

[0032] The membrane material of the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor in this embodiment is Sm 0.2 Ce 0.8 O 1.9 Powder (particle size about 2-4 μm) and ternary molten carbonate of Li2CO3, Na2CO3, K2CO3 with a molar ratio of 43.5:31.5:25. The film shape is a sheet film with an effective area of ​​1 cm 2 , with a thickness of about 0.75 mm; the Cr / SiO2 catalyst (about 0.42 g) was pelletized and placed in the membrane reactor near the membrane reaction side surface, and 50 mL min was passed into the membrane supply side. -1 Simulated flue gas, 30 mL min was introduced into the reaction side -1 A mixture of propane and argon (propane accounts for 5.5% by volume). At 675°C, the propane conversion rate is 69.2%, the propylene selectivity and yield are 20.56% and 14.23%, and the CO2 permeation flux is about 0.48 ml min -1 cm -2 .

[0033] Comparative Example 1

[0034] A quartz fixed bed reactor with a diameter of 6 mm was used for the oxidative dehydrogenation of propane with carbon dioxide as a comparative example. During the test of the fixed bed reactor, the reaction gas, the catalyst components and mass (Cr / SiO2, 0.42 g), and the reaction temperature (675°C) were the same as those in Examples 1-3. The difference was that the fixed bed reactor introduced carbon dioxide, propane, and argon simultaneously from the reactor inlet at a total flow rate of 30 ml min -1 The outlet gases of the fixed bed reactor and the membrane reactor were dried and then analyzed by the same gas chromatograph. The reactions were all carried out at normal pressure. The test results of Examples 1-3 and Comparative Example 1 are shown in Table 1. It can be seen that the selectivity and yield of propylene in the ceramic-molten salt two-phase carbon dioxide separation membrane reactor are higher than those in the fixed bed reactor.

[0035] Table 1 Performance comparison between Examples 1-3 and Comparative Example 1

[0036]

[0037] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for capturing carbon dioxide in high-temperature flue gas and converting it in situ to produce propylene, characterized in that: High-temperature flue gas is introduced into the supply side of a ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, and propane gas is introduced into the reaction side of the membrane reactor. Carbon dioxide permeates from the supply side to the reaction side and reacts with propane on the reaction side under the action of a catalyst to generate propylene.

2. The method according to claim 1, characterized in that In the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, the membrane material consists of a porous oxygen ion ceramic skeleton and multi-component molten carbonate filled therein.

3. The method according to claim 2, characterized in that The porous oxygen ion ceramic skeleton comprises one of samarium oxide doped cerium oxide material, gadolinium oxide doped cerium oxide material and yttria stabilized zirconia.

4. The method according to claim 2, characterized in that: The multi-component molten carbonate is composed of at least two of Li2CO3, Na2CO3, and K2CO3.

5. The method according to claim 2, characterized in that: The porous oxygen ion ceramic skeleton has a porosity of 30-60% and a pore size of 1-20 μm.

6. The method according to claim 1, characterized in that In the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor, the catalyst includes one of a vanadium-based catalyst, a chromium-based catalyst, and a molybdenum-based catalyst, wherein the carrier includes one of an oxide, a zeolite, a molecular sieve, and a metal organic framework.

7. The method according to claim 1, characterized in that The operating temperature in the ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor is 500-900°C.

8. The method according to claim 1, characterized in that: The ceramic-molten salt-based two-phase carbon dioxide separation membrane reactor has a flat plate type or a tubular type configuration.

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