Oxygen carrier, preparation method and application of oxygen carrier in preparation of ethylene from ethane by chemical looping

Abstract

The invention belongs to the technical field of oxygen carriers for preparing ethylene through ethane chemical looping, and particularly relates to an oxygen carrier, a preparation method and application of the oxygen carrier in preparing ethylene through ethane chemical looping. The oxygen carrier takes LaCoO3 as a carrier, Co2O3 as an active component and ZnO as an auxiliary agent, the mass content of the active component Co2O3 in the oxygen carrier is 3-30%, and the mass content of the auxiliary agent ZnO is 1-5%. The oxygen carrier is prepared by an in-situ one-step method. According to the application of the oxygen carrier in preparation of ethylene from ethane through chemical looping, the reaction temperature in a fuel reactor is 600-1000 DEG C, the reaction temperature in an air reactor is 600-1000 DEG C, and the reaction pressure is 0.1-1 MPa. The oxygen carrier disclosed by the invention has a perovskite structure, the active components are uniformly dispersed, the preparation method is simple, and the oxygen carrier has the advantages of high ethylene selectivity and good stability in a reaction for preparing ethylene by using an ethane chemical chain.

Description

Technical Field

[0001] This invention belongs to the technical field of oxygen carriers for the chemical chain production of ethylene from ethane, specifically relating to an oxygen carrier, its preparation method, and its application in the chemical chain production of ethylene from ethane. Background Technology

[0002] Ethylene is both a hydrocarbon cracking product and an important basic feedstock for petrochemicals. The ethylene industry is the leading sector of the petrochemical industry, accounting for over 75% of petrochemical products and holding a vital position in the national economy. Globally, ethylene production is considered a key indicator of a country's petrochemical development level. China and the United States, the two largest petrochemical producers and consumers, are leading the rapid growth of global ethylene production capacity. In 2022, China surpassed the United States to become the world's largest ethylene producer. In the future, global oil demand growth will slow, while demand for chemical products will grow steadily, leading to steady investment in the ethylene industry. Ethylene feedstocks are becoming more diversified and lighter, and plants are becoming larger-scale. Production technologies are becoming more diversified and low-carbon, widening the regional gap in ethylene industry development and intensifying competition. As of the end of 2021, my country had 61 ethylene production enterprises with 79 operational ethylene plants, totaling a capacity of 41.68 million tons per year, accounting for approximately 18% of global capacity. Among them, there are 41 steam cracking ethylene production units with a production capacity of 29.48 million tons / year; 27 coal / methanol to olefins units with an ethylene production capacity of 7.15 million tons / year; and 6 ethane cracking ethylene production units with a production capacity of 4.9 million tons / year. In terms of the yield of ethylene from various feedstocks, the average yield of ethylene from ethane cracking is around 80%, while the yield from naphtha is around 35%, and the yield from liquefied petroleum gas feedstock is 42%.

[0003] In recent years, researchers have conducted extensive work in various aspects, including the utilization of inexpensive raw materials, catalyst innovation, and the development of low-energy, short-process technologies, exploring a variety of new ethylene production technologies and achieving significant progress. The methane oxidative coupling technology for ethylene production suffers from problems such as high reaction temperature, large heat release, and high investment costs. The ethane direct oxidative dehydrogenation technology for ethylene production requires large amounts of inert gas for dilution to keep the reaction mixture away from flammable areas, increasing safety risks and significantly raising equipment investment and operating costs. While the ethane carbon dioxide oxidative dehydrogenation technology for ethylene production avoids the use of large amounts of inert gas, it also faces practical challenges. On the one hand, due to the limitations of the counter-current gas reaction equilibrium, the carbon dioxide conversion rate is usually low, and the large amount of carbon monoxide generated in this process increases downstream separation costs. On the other hand, the high endothermic nature of this reaction also increases operating costs. The direct syngas-to-ethylene technology has completed pilot-scale testing and achieved significant results. Further in-depth research and development are needed to better balance catalyst reaction performance and process operating conditions. Simultaneously, the research and development of efficient reactors and supporting engineering technologies are crucial for its industrial application.

[0004] Chemical chaining technology is a process intensification technique. The chemical chaining of ethane to ethylene utilizes the lattice oxygen of a metal oxide-based oxygen carrier to promote ethane conversion. Because the reaction process does not require oxygen or inert gas dilution, it greatly improves the safety environment of the reaction process and reduces process investment and operating costs. The process consists of two steps: first, ethane is oxidized by the oxygen carrier to produce ethylene and water, while the oxygen carrier is simultaneously reduced by ethane; then, air is introduced to oxidize the oxygen carrier and release heat, completing one cycle. Typically, the oxygen carrier in this technology undergoes multiple redox cycles. This technology features low-cost oxygen carriers, self-heating continuous operation, and breaking the thermodynamic equilibrium of alkane dehydrogenation, which can significantly increase olefin yields. Furthermore, the process flow is short, saving investment and operating costs, thus showing good development and application prospects. Currently, this technology has not yet been industrially applied, mainly because the oxygen carrier still suffers from low activity, poor selectivity, and poor stability. Elvadawi AH et al. investigated a series of VO2+ reactions in a circulating fluidized bed reactor. x -MoO x / γ-Al2O3 oxygen carriers can still achieve 55%–85% ethylene selectivity after multiple reaction-regeneration cycles in the temperature range of 500–650℃, but the ethane conversion rate is relatively low. Khadzhiev SN et al. tested a series of VO2+ loaded on γ-Al2O3. x and MoO x Oxygen carrier, the results showed that MoO z The ethane conversion rate on the Al2O3 oxygen carrier was 66.5%, and the ethylene selectivity was 94.5%. Currently, international research mainly focuses on oxygen carrier screening and performance optimization through simulations and laboratory settings; there are no reports of domestic researchers conducting research on this technology. This technology has certain forward-looking potential; only by solving the problem of poor oxygen carrier activity can it further advance towards industrial applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an oxygen carrier, its preparation method, and its application in the chemical chain reaction of ethane to ethylene. This oxygen carrier possesses a perovskite structure, high lattice oxygen content, and uniform dispersion, exhibiting high ethylene selectivity and stability in the ethane chemical chain reaction to ethylene.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows: An oxygen carrier includes: a LaCoO3 support having a perovskite structure; a Co2O3 active component loaded on the support; and ZnO as an auxiliary agent; wherein, based on the total mass of the oxygen carrier, the mass content of Co2O3 is 3-30%, and the mass content of ZnO is 1-5%.

[0007] Furthermore, the mass content of Co2O3 in this invention is 8-20%; and the mass content of ZnO is 3-5%.

[0008] Furthermore, the oxygen carrier described in this invention is spherical, strip-shaped, or microsphere-shaped.

[0009] Furthermore, the particle size of the oxygen carrier described in this invention is 10–2000 µm.

[0010] A method for preparing the above-mentioned oxygen carrier includes the following steps: (1) Provide a mixed salt solution containing lanthanum source, cobalt source and zinc source; (2) The mixed salt solution is mixed with the complexing agent solution and stirred at 20-80°C for 2-8 hours to form a gel; (3) Dry the gel obtained in step (2) at 90-120°C for 8-14 hours to obtain the dried precursor; (4) The dried precursor obtained in step (3) is calcined at 600-1000℃ for 3-6 hours to obtain the target product, which is used as an oxygen carrier for the chemical chain synthesis of ethylene from ethane.

[0011] Furthermore, in step (1) of the present invention, the lanthanum source, cobalt source and zinc source are lanthanum nitrate, cobalt nitrate and zinc nitrate, respectively.

[0012] Furthermore, in step (2) of the present invention, the complexing agent is citric acid.

[0013] Furthermore, in step (2) of the present invention, the stirring speed is 50-200 r / min; in step (4), the calcination temperature is 800℃.

[0014] An application of the above-mentioned oxygen carrier in the chemical chain reaction of ethane to ethylene, wherein the application is carried out in a chemical chain reaction system, the system comprising a fuel reactor and an air reactor; wherein, in the fuel reactor, the reaction temperature is 600-1000°C and the reaction pressure is 0.1-1 MPa; and in the air reactor, the regeneration temperature is 600-1000°C.

[0015] Furthermore, the reaction temperature in the fuel reactor is 650°C; the oxygen carrier is recycled between the fuel reactor and the air reactor.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The ZnO-Co2O3 / LaCoO3 oxygen carrier of the present invention is prepared by an in-situ one-step method. The preparation method is simple and convenient to operate, which is conducive to large-scale industrial preparation.

[0017] (2) The ZnO-Co2O3 / LaCoO3 oxygen carrier of the present invention has a perovskite structure, which is stable at high temperature and will not decompose. LaCoO3 contains abundant lattice oxygen, which is easy to release when reacting with ethane to oxidize ethane. After adding the additive ZnO, ZnO enters the Co2O3 lattice. Due to the different radii of zinc ions and cobalt ions, the lattice oxygen is unstable and is more likely to be released and absorbed under an oxidation-reduction atmosphere, thereby improving the ethylene selectivity and the stability of the oxygen carrier. Therefore, the oxygen carrier has a stronger oxygen release and oxygen absorption capacity, which is beneficial to the oxidation of ethane and the generation of ethylene.

[0018] (3) In the present invention, Co2O3 is used as the active component and ZnO is used as the auxiliary agent in the ZnO-Co2O3 / LaCoO3 oxygen carrier. It is prepared by in-situ one-step method, which has the advantages of small particle size and high dispersion, which is beneficial to improving ethylene selectivity. Attached Figure Description

[0019] Figure 1 The image shows the XRD pattern of the ZnO-Co2O3 / LaCoO3 oxygen carrier prepared in Example 1 of this invention. Detailed Implementation

[0020] The present invention will now be described in detail through specific embodiments. These embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended and are interpreted as "comprising but not limited to". The following description is a preferred embodiment for carrying out the invention; however, this description is intended to illustrate the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the present invention is determined by the appended claims. Example 1

[0021] Weigh 7.65g of cobalt nitrate, 8.58g of lanthanum nitrate, and 0.63g of zinc nitrate, and dissolve them in 150ml of distilled water. Then weigh 9.96g of citric acid and dissolve it in 50ml of distilled water. Slowly pour the citric acid solution into the mixed solution, and then place the beaker containing the mixed solution in a water bath. Stir the mixed solution with an electric stir bar at a speed of 100r / min, maintaining the water bath temperature at 50℃. After stirring for 3-4 hours, the solution will reach a gel state, at which point stirring should be stopped. After removal, dry in a drying oven at 110℃ for 12 hours, and calcine in a muffle furnace at 800℃ for 4 hours to obtain the oxygen carrier ZnO-Co2O3 / LaCoO3, wherein the mass content of Co2O3 is 15%, the mass content of ZnO is 3%, and the mass content of LaCoO3 is 82%.

[0022] The performance evaluation of the oxygen carriers prepared in the above examples and comparative examples was carried out as follows. The prepared oxygen carriers were sieved, and 0.4 g of oxygen carrier with a particle size of 40-60 mesh was taken and its performance was tested in a fixed-bed quartz tube reactor. The quartz tube specifications were f8×2 mm, and the feed gas composition was: 10% C2H6, 90% N2. The sample was heated from room temperature to 650°C under nitrogen protection, and then the feed gas was introduced for reaction at a flow rate of 50 ml / min. After reacting for 1-5 minutes, nitrogen was purged for 10 minutes, and then air was switched for oxidation at a flow rate of 30 ml / min. After 10 minutes, nitrogen was purged again, thus completing one oxidation-reduction cycle. Online gas chromatography with TCD detection was used, employing a 5A molecular sieve column and a 502 column. The C2H6 conversion rate was 95%, and the C2H4 selectivity was 73%.

[0023] Example 2

[0024] Following the preparation steps in Example 1, the calcination temperature was changed to 650°C. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion rate was 89%, and the C2H4 selectivity was 58%.

[0025] Example 3

[0026] Following the preparation steps in Example 1, the calcination temperature was changed to 900°C. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion rate was 91%, and the C2H4 selectivity was 63%.

[0027] Example 4

[0028] Following the preparation steps in Example 1, the mass of cobalt nitrate was changed to achieve a cobalt oxide loading of 8 wt%. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion was 87%, and the C2H4 selectivity was 55%.

[0029] Example 5

[0030] Following the preparation steps in Example 1, the mass of cobalt nitrate was changed to achieve a cobalt oxide loading of 20 wt%. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion was 98%, and the C2H4 selectivity was 75%.

[0031] Example 6

[0032] Following the preparation steps in Example 1, the mass of zinc nitrate was changed to achieve a zinc oxide loading of 1 wt%. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion was 85%, and the C2H4 selectivity was 67%.

[0033] Example 7

[0034] Following the preparation steps in Example 1, the mass of zinc nitrate was changed to achieve a zinc oxide loading of 5 wt%. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion was 96%, and the C2H4 selectivity was 78%.

[0035] Example 8

[0036] Following the preparation steps in Example 1, the reaction temperature was changed to 1000°C. The performance of the ethane chemical chain reaction to ethylene was tested using this oxygen carrier under the same conditions as in Example 1. The C2H6 conversion was 100%, and the C2H4 selectivity was 69%.

[0037] Comparative Example 1 Co₂O₃ / MgO particles were prepared using a conventional co-precipitation method, with calcination and performance testing conditions identical to those in Example 1. The C₂H₆ conversion rate was 64%, and the C₂H₄ selectivity was 25%.

[0038] Comparative Example 2 Following the preparation steps in Example 1, the ZnO mass fraction was 0, and the calcination and performance testing conditions were the same as in Example 1. The C2H6 conversion rate was 82%, and the C2H4 selectivity was 48%.

[0039] The content of this invention is not limited to the embodiments listed. Any equivalent modifications made by those skilled in the art to the technical solutions of this invention by reading this specification are covered by the claims of this invention.

Claims

1. An oxygen carrier, characterized in that, include: LaCoO3 support with perovskite structure; The active component of Co2O3 loaded on the carrier; And ZnO as an auxiliary agent; wherein, based on the total mass of the oxygen carrier, the mass content of Co2O3 is 3-30% and the mass content of ZnO is 1-5%.

2. The oxygen carrier according to claim 1, characterized in that, The Co2O3 content is 8-20% by mass; the ZnO content is 3-5% by mass.

3. The oxygen carrier according to claim 2, characterized in that, The oxygen carrier is spherical, strip-shaped, or microsphere-shaped.

4. The oxygen carrier according to claim 3, characterized in that, The particle size of the oxygen carrier is 10–2000 µm.

5. A method for preparing the oxygen carrier as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Provide a mixed salt solution containing lanthanum source, cobalt source and zinc source; (2) The mixed salt solution is mixed with the complexing agent solution and stirred at 20-80°C for 2-8 hours to form a gel; (3) Dry the gel obtained in step (2) at 90-120°C for 8-14 hours to obtain the dried precursor; (4) The dried precursor obtained in step (3) is calcined at 600-1000℃ for 3-6 hours to obtain the target product, which is used as an oxygen carrier for the chemical chain synthesis of ethylene from ethane.

6. The method according to claim 5, characterized in that, In step (1), the lanthanum source, cobalt source and zinc source are lanthanum nitrate, cobalt nitrate and zinc nitrate, respectively.

7. The method according to claim 6, characterized in that, In step (2), the complexing agent is citric acid.

8. The method according to claim 7, characterized in that, In step (2), the stirring speed is 50-200 r / min; in step (4), the calcination temperature is 800℃.

9. The application of the oxygen carrier as described in any one of claims 1 to 4 in the chemical chain production of ethylene from ethane, characterized in that, The reaction is carried out in a chemical looping reaction system, which includes a fuel reactor and an air reactor; wherein, in the fuel reactor, the reaction temperature is 600–1000°C and the reaction pressure is 0.1–1 MPa; and in the air reactor, the regeneration temperature is 600–1000°C.

10. The application of the oxygen carrier according to claim 9 in the chemical chain production of ethylene from ethane, characterized in that, The reaction temperature in the fuel reactor is 650°C; the oxygen carrier is recycled between the fuel reactor and the air reactor.

Images