Hydrogen transfer material for propane dehydrogenation reaction

Abstract

The invention belongs to the technical field of catalysts, and particularly discloses a hydrogen transfer material for propane dehydrogenation reaction. The hydrogen transfer material disclosed by the invention is a composite oxide with a Ruddlesden-Popper type layered perovskite structure, and the oxide has the characteristic of reacting with H2 in a temperature range of 400-550 DEG C without discharging water, so that the negative effect of water vapor on propane dehydrogenation is avoided. The special rock salt layered structure has rapid hydrogen intercalation-deintercalation capability, and can react with H2 to reduce the hydrogen partial pressure in the propane dehydrogenation process and break through the thermodynamic equilibrium limitation in the concerted catalysis process with a propane dehydrogenation catalyst, so that the propane dehydrogenation reaction at lower reaction temperature is realized. The energy consumption in the process is greatly reduced, and the selectivity of propane dehydrogenation is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a hydrogen transfer material for propane dehydrogenation reaction. Background Art

[0002] In recent years, driven by multiple factors, including the electrification of automobiles, the dual-carbon economy, and shale gas development, the propane dehydrogenation industry has experienced explosive growth. Currently, the propane dehydrogenation process consumes approximately 600 kg of standard coal per ton of propylene, emitting approximately 2.2 tons of carbon dioxide. Based on a 25 million ton propylene production capacity, this industry's carbon emissions exceed 50 million tons per year. Reducing reaction energy consumption is crucial to the healthy development of the industry.

[0003] Propane catalytic dehydrogenation is a volume-increasing and highly endothermic reaction. Due to thermodynamic equilibrium constraints, the reaction generally occurs at high temperatures of 550–600°C. High-temperature reactions present a series of problems: (1) Temperature increases are accompanied by high energy consumption; (2) Propane, propylene, and reaction intermediates are prone to coking and deactivation at high temperatures, reducing propylene selectivity and increasing carbon emissions, affecting process economics, increasing process difficulty, and enhancing process safety; (3) Catalysts are prone to loss and sintering at high temperatures, affecting catalyst activity and life. Therefore, achieving low-temperature propane dehydrogenation is the only way to reduce carbon emissions.

[0004] The equilibrium conversion rate of propane dehydrogenation can be expressed as k=(p C3H6▪ p H2 ) / p C3H8 By designing special catalysts or reaction processes to reduce the H2 partial pressure, the propylene partial pressure increases accordingly, corresponding to a higher propylene yield. This makes it possible to achieve a significant propylene single-pass yield at a lower reaction temperature. For example, Suljo Linic et al. reported that a 140% propylene yield was achieved at 580°C over a PtSn / SiO2 catalyst by selectively permeating H2 through a SiO2 / Al2O3 membrane (Science 383(2024)1325). Gong Jinlong et al. used the reaction of lattice oxygen in FeVO4 with H2 to achieve a chemical chain dehydrogenation process at 550°C. The FeVO4 can be regenerated during the regeneration process, but the propylene yield in this process did not exceed the thermodynamic limit (Science 381(2023)886).

[0005] At present, there are still significant barriers for these cutting-edge technologies in industrial applications. In terms of membrane materials, on the one hand, large-scale membrane synthesis is difficult, expensive, and has limited throughput, making it difficult to meet industrial demands. In terms of chemical looping dehydrogenation, the reaction of H2 with lattice oxygen can reduce the partial pressure of H2. However, the generated H2O brings serious negative effects. On the one hand, the adsorption of H2O molecules on the catalyst surface is often stronger than that of the raw material propane, reducing the adsorption of propane on the catalyst and thus seriously affecting the conversion rate. For example, when there is 0.3% water vapor in the feed gas, the Cr-based catalyst is significantly deactivated. On the other hand, H2O may damage the catalyst structure (such as converting the active center Lewis acid to Brønsted, and converting some alloys in the alloy catalyst to oxides). Therefore, there are still great difficulties in the low-temperature propane dehydrogenation reaction at present.

[0006] Therefore, aiming at the problems of high reaction temperature and large carbon emissions in the current propane dehydrogenation reaction, how to design a material that can break the limitation of thermodynamic equilibrium and achieve low-temperature propane dehydrogenation reaction is the technical problem to be solved by the present invention. Summary of the Invention

[0007] To solve the above technical problems, the object of the present invention is to provide a hydrogen transfer material for propane dehydrogenation reaction. The hydrogen transfer material of the present invention acts together with the propane dehydrogenation catalyst, can react with the generated H2 in the reaction conditions but does not release other substances, and is restored during the regeneration process. By transferring the generated H2 in the reaction, the limitation of thermodynamic equilibrium is broken, and the low-temperature propane dehydrogenation reaction is achieved.

[0008] The object of the present invention can be achieved by the following technical solutions: In the first aspect, the present invention provides a hydrogen transfer material for propane dehydrogenation reaction, and the chemical formula of the hydrogen transfer material is A n+1 B n O 3n+1 , where A is at least one of Ca, Sr, Ba, and La, B is at least one of Mn and Fe, and the crystal phase structure of the hydrogen transfer material is the Ruddlesden-Popper type layered perovskite.

[0009] Further, n in the chemical formula of the hydrogen transfer material is a positive integer.

[0010] Furthermore, n in the chemical formula of the hydrogen transfer material is 2.

[0011] Further, the preparation method of the hydrogen transfer material is one of co-precipitation method, sol-gel method, and solid-phase synthesis method.

[0012] The hydroxides of general metal ions will dehydrate to form oxides during the heating process, while the hydroxides of alkaline earth metal ions and rare earth metal ions dehydrate to form oxides at relatively high temperatures. For example, the temperature at which Ca(OH)2 dehydrates to form CaO is 580 °C, which provides the possibility of reacting with H2 at high temperatures without releasing H2O. Ruddlesden-Popper type layered perovskite A n+ 1B n O 3n+1 (where A is an alkaline earth or rare earth metal, and B is a transition metal). The reducible transition metal B is in the layer, and the interlayer is composed of AO rock salt layers with a relatively large ionic radius. During the reaction process, the reduction process of H2 is achieved by inserting hydrogen atoms into the interlayer AO to convert it into AOH, which remains unchanged due to its high thermal stability; during the regeneration process, hydrogen atoms transfer to the gas phase and react with O2 to form H2O. The reaction equations for its dehydrogenation reaction and the regeneration process are as follows:

[0013] This process is similar to the insertion and extraction of Li in a lithium-ion battery. The unique layered structure of the R-P type layered perovskite not only inhibits the dehydration of AOH but also facilitates the rapid insertion and extraction of hydrogen atoms. Different from conventional oxides, the release of H2O occurs during the regeneration process rather than the reaction process, thus avoiding the side effect of the formation of H2O during the reaction process on the propane dehydrogenation reaction.

[0014] The second aspect of the present invention provides an application of the above hydrogen transfer material in the propane dehydrogenation reaction. The hydrogen transfer material is used together with a propane dehydrogenation catalyst to promote the right shift of the equilibrium by transferring the H2 generated during the reaction and reduce the propane dehydrogenation reaction temperature.

[0015] Further, the propane dehydrogenation catalyst is one of Cr2O3 / Al2O3 or PtSn / Al2O3.

[0016] Further, the mass ratio of the hydrogen transfer material to the propane dehydrogenation catalyst is 0.1 - 2.

[0017] Further, the temperature of the propane dehydrogenation reaction is 420 - 550 °C, and the reaction space velocity is 0.1 - 10 h -1 .

[0018] The beneficial effects that this application can produce are as follows: The hydrogen transfer material described in the present invention is a composite oxide with a Ruddlesden-Popper type layered perovskite structure. This oxide has the characteristic of reacting with H2 without releasing water in the temperature range of 400~550°C, thus avoiding the negative effect of water vapor on propane dehydrogenation. Its special rock salt layered structure has fast hydrogen insertion and extraction capabilities. During the co-catalysis process with a propane dehydrogenation catalyst, it can react with H2 to reduce the hydrogen partial pressure in the propane dehydrogenation process, break through the thermodynamic equilibrium limit, and thus achieve propane dehydrogenation reaction at a lower reaction temperature. This will greatly reduce the energy consumption of this process and improve the selectivity of propane dehydrogenation. The specific technical effects are as follows: (1)The hydrogen transfer material of the present invention is an R-P layered perovskite material, which realizes the transfer of H2 during the reaction and regeneration processes through the insertion and extraction of hydrogen atoms. No water vapor is generated during the reaction process, avoiding the negative impact of water vapor on the reaction.

[0019] (2)The hydrogen transfer material of the present invention realizes the high-speed transfer of hydrogen, breaks through the thermodynamic equilibrium limit, and the propane dehydrogenation reaction temperature drops by 50~100°C compared with the conventional process. This will greatly reduce the energy consumption of this process and improve the selectivity of propane dehydrogenation. Description of the Drawings

[0020] Figure 1 It is the XRD pattern of the hydrogen transfer material B1 in Example 1.

[0021] Figure 2 It is the TEM image of the hydrogen transfer material B1 in Example 1. Among them, the four figures a, b, c, and d are images taken from different regions and different magnifications of the TEM, and the resolutions are: a: 20 nm, b: 2 nm, c: 5 nm, d: 5 nm.

[0022] Figure 3 It is the H2-TPR spectra of the hydrogen transfer materials B1 and B2.

[0023] Figure 4 It is the co-catalytic cycle stability change diagram of the propane dehydrogenation catalyst A1 and the hydrogen transfer material B1. Detailed Embodiments

[0024] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0025] Example 1: Preparation of the hydrogen transfer material B1 Dissolve 5.20 g of La(NO3)3·6H2O, 11.33 g of Ca(NO3)2·4H2O, and 14.32 g of 50 wt.% Mn((NO3)2 solution in 200 ml of deionized water and label it as solution A. Dissolve 10.20 (NH4)2CO3 in 200 ml of 0.2 mol / L ammonia water and label it as solution B. Under stirring in a 60°C water bath, add solution A dropwise to solution B. After the addition is complete, continue aging for 12 h. After filtration, washing, and drying, then calcine at 900°C for 5 h and at 1300°C for 24 h to obtain a hydrogen transfer material labeled as B1. The hydrogen transfer material B1 was characterized by XRD line scan and high-resolution transmission electron microscopy, as shown in Figure 1 and Figure 2 . It can be seen from Figure 1 that this material has typical diffraction peaks of perovskite-like materials. It can be seen from figures b, c, and d in Figure 2 that lattice fringes (100), (108), (110), and (003) of perovskite-like materials can be seen in this material at 2 nm and 5 nm. Figure 2 In figure a of Figure 2 , typical characteristic peaks on the C axis, such as (004) and (002), also exist at 20 nm, with interplanar spacings of 0.56 nm and 1.13 nm. The two characterization results confirm each other. This characteristic peak on the C axis corresponds to a layered rock salt structure, in which there are only alkaline earth and rare earth metals between the layers, and the perovskite structure oxide formed by alkaline earth, rare earth metals, and transition metals in the layer board. This interlayer structure provides a high-speed channel for the rapid insertion and extraction of hydrogen.

[0026] Comparative Example 1: Preparation of hydrogen transfer material B2 Dissolve 9.44 g of Ca(NO3)2·4H2O and 14.32 g of 50 wt.% Mn((NO3)2 solution in 200 ml of deionized water and label it as solution A. Dissolve 8.50 (NH4)2CO3 in 200 ml of 0.1 mol / L ammonia water and label it as solution B. Under stirring in a 60°C water bath, add solution A dropwise to solution B. After the addition is complete, continue aging for 12 h. After filtration, washing, and drying, then calcine at 1100°C for 5 h to obtain a hydrogen transfer material labeled as B2.

[0027] Example 2: Preparation of hydrogen transfer material B3 Dissolve 14.17 g of Ca(NO3)2·4H2O, 14.32 g of 50 wt.% Mn((NO3)2 solution, and 23.04 g of citric acid in 100 ml of deionized water. Rotate and evaporate this solution at 80°C to obtain a brown powder after foaming. Then calcine at 900°C for 5 h and at 1300°C for 48 h to obtain a hydrogen transfer material labeled as B3.

[0028] Example 3: Preparation of hydrogen transfer material B4 Mix 20 g of CaCO3 and 8.7 g of MnO2 by ball milling for 1 h, calcine at 900 °C for 5 h. After grinding the obtained powder, press it into a Φ15 mm wafer, calcine at 1350 °C for 24 h, then crush and grind it and press it into a Φ15 mm wafer again, and calcine at 1350 °C for 24 h. The obtained hydrogen transfer material is denoted as B4.

[0029] Example 4: Preparation of hydrogen transfer material B5 Mix 9.78 g of La2O3, 2.96 g of SrCO3, and 4.79 g of Fe2O3 by ball milling for 1 h, calcine at 900 °C for 5 h. After grinding the obtained powder, press it into a Φ15 mm wafer, calcine at 1400 °C for 24 h, then crush and grind it and press it into a Φ15 mm wafer again, and calcine at 1400 °C for 24 h. The obtained hydrogen transfer material is denoted as B5.

[0030] Example 5: Preparation of hydrogen transfer material B6 Dissolve 8.66 g of La(NO3)3·6H2O, 4.23 g of Sr(NO3)2, 4.72 g of Ca(NO3)2·4H2O, 7.16 g of 50 wt.% Mn((NO3)2 solution, 8.08 g of Fe(NO3)3·9H2O, and 23.04 g of citric acid in 100 ml of deionized water. Rotate and evaporate the solution to dryness at 80 °C, obtain a brown powder through foaming, then calcine at and 900 °C for 5 h and 1300 °C for 48 h. The obtained hydrogen transfer material is denoted as B6.

[0031] Example 6: Preparation of hydrogen transfer material B7 Dissolve 14.17 g of Ca(NO3)2·4H2O, 17.90 g of 50 wt.% Mn((NO3)2 solution, and 25.34 g of citric acid in 100 ml of deionized water. Rotate and evaporate the solution to dryness at 80 °C, obtain a brown powder through foaming, then calcine at 900 °C for 5 h and 1350 °C for 72 h. The obtained hydrogen transfer material is denoted as B7.

[0032] Example 7: Preparation of propane dehydrogenation catalyst A1 Dissolve 2.7 g of NaNO3 and 26.3 g of CrO3 in 4.7 g of deionized water, then impregnate it onto 79 g of γ-Al2O3 support with equal volume, dry at 100 °C for 12 h, and then calcine at 750 °C for 5 h. The obtained propane dehydrogenation catalyst Cr2O3 / Al2O3 is denoted as A1.

[0033] Example 8: Preparation of propane dehydrogenation catalyst A2 Dissolve 0.21 g of KNO3, 0.53 g of SnCl4·5H2O, and 0.26 g of H2PtCl6·6H2O in 19 ml of 0.1 mol / L HCl solution, and then impregnate it onto 32 g of γ-Al2O3 in equal volume. Dry it at 100 °C for 12 h, then calcine it at 500 °C for 5 h, and reduce it at 600 °C for 5 h in a 10% H2-Ar mixed gas. The obtained propane dehydrogenation catalyst PtSn / Al2O3 is denoted as A2.

[0034] Performance test 1. H2-TPR characterization of hydrogen transfer materials B1 and B2 In the present invention, whether water is released during the reduction process of the hydrogen transfer material in the propane dehydrogenation reaction is a key issue for this material. Use H2-TPR characterization technology to characterize and analyze B1 and B2, and use two detectors to detect the consumption of H2 and the generation of H2O respectively. Among them, the TCD detector mainly detects the consumption of H2 through the change of the thermal conductivity coefficient, and the MS detector mainly detects the signal of H2O in the mass spectrum to study the release temperature of H2O. The characterization results are shown in Figure 3 . As can be seen from the figure, for the hydrogen transfer material B2 in Comparative Example 1, the signals on the two detectors are similar, only the release of H2O is slightly lagged, which indicates that the reduction of the material and the release of H2O are basically synchronous. The reason is that stepwise calcination is not carried out during the preparation process; on the contrary, for material B1, the TCD detector shows an obvious reduction peak in the temperature range of 400-650 °C, while there is an obvious release peak of H2O on the MS detector only after 550 °C, and there is an obvious tailing phenomenon, which indicates that the release of H2O on this material is significantly lagged. Therefore, there is a phenomenon that only reacts with H2 without releasing H2O in the temperature window of 400-550 °C, which provides space for synergistic catalysis with the propane dehydrogenation catalyst.

[0035] 2. Synergistic effect test of hydrogen transfer material and propane dehydrogenation catalyst Respectively mix the propane dehydrogenation catalysts A1 and A2 with the hydrogen transfer materials B1-B7 obtained in Examples 1-6 and Comparative Example 1 in a certain proportion, grind and press them into tablets, and crush them into 20-40 mesh. Use 99.6% C3H8 raw material gas to evaluate the propane dehydrogenation performance on an atmospheric fixed-bed micro-reactor device, and the catalyst loading is 2 g. The evaluation results of different materials are shown in Table 1.

[0036] Table 1

[0037]

[0038]

[0039]

[0040] The equilibrium conversion is the inherent value calculated from the thermodynamic equilibrium equation for the pure propane dehydrogenation reaction at atmospheric pressure and different reaction temperatures. Changing the reaction pressure, introducing a diluent, or altering the product concentration can disrupt the reaction equilibrium.

[0041]

[0042] As shown in Table 1, conventional Cr-based (A1) and Pt-based (A2) catalysts require relatively high reaction temperatures to achieve satisfactory propane dehydrogenation yields. Their yield-to-equilibrium conversion ratios range from 86% to 97%, clearly constrained by thermodynamic equilibrium. The addition of a hydrogen transfer aid significantly increases propane conversion at various temperatures, with ratios to equilibrium conversion ranging from 140% to 300%, demonstrating a breakthrough in thermodynamic equilibrium. Compared to the catalysts without the addition of a hydrogen transfer aid, the dehydrogenation temperature decreases by 50-100°C for the same propylene yield. This temperature reduction offers a range of benefits, including reduced energy consumption, increased selectivity, catalyst stability, and improved carbon deposition resistance. In contrast, the catalytic activity of the hydrogen transfer material B2 in Comparative Example 1 decreases significantly due to the release of H₂O during use, with the decrease becoming more pronounced with increasing dosage. This demonstrates the inhibitory effect of H₂O on the propane dehydrogenation reaction. This demonstrates the necessity of the materials in this invention to react with H₂ without releasing water.

[0043] 3. Stability test of hydrogen transfer material B1 Another key to the material is whether the hydrogen transfer material can be stably circulated. Using the A1-B1 combination, where B1:A1=1 (mass ratio), the reaction temperature is 500℃, and the propane space velocity is 1h -1 The reaction was carried out for 0.5 h each time, followed by N2 purge-air regeneration-N2 purge regeneration, with a regeneration temperature of 400°C and a regeneration time of 0.5 h.

[0044] Figure 4 This is a graph showing the catalytic performance changes after 200 cycles of propane dehydrogenation catalyst A1 and hydrogen transfer material B1. Catalytic performance refers to a comprehensive index of propane conversion rate and propylene selectivity. If the long-term reaction fluctuation is less than 5%, the catalytic performance can be considered stable. Figure 4 It can be seen that within 200 cycle reactions, the propane conversion rate on the left vertical axis is between 31.5% and 33%, and the propylene selectivity on the right vertical axis is between 94% and 96%. The performance remains stable and has the characteristic of significantly improving the single-pass yield of propane dehydrogenation.

[0045] The above is a specific description of the preferred embodiment of the present invention. However, the present invention is not limited to the described embodiment. Those skilled in the art can make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A hydrogen transfer material for propane dehydrogenation reaction, characterized in that, The chemical formula of the hydrogen transfer material is A n+ 1B n O 3n+1 , where A is at least one of Ca, Sr, Ba, and La, B is at least one of Mn and Fe, and the crystal phase structure of the hydrogen transfer material is a Ruddlesden-Popper type layered perovskite.

2. The hydrogen transfer material for propane dehydrogenation reaction according to claim 1, characterized in that, n in the chemical formula of the hydrogen transfer material is a positive integer.

3. The hydrogen transfer material for propane dehydrogenation reaction according to claim 2, characterized in that, n in the chemical formula of the hydrogen transfer material is 2.

4. A hydrogen transfer material for propane dehydrogenation reaction according to claim 1, characterized in that, The preparation method of the hydrogen transfer material is one of co-precipitation method, sol-gel method and solid-phase synthesis method.

5. A hydrogen transfer material for propane dehydrogenation reaction according to claim 4, characterized in that, The co-precipitation method includes the following steps: Dissolve the nitrate containing element A and the nitrate containing element B in deionized water to obtain solution A, dissolve (NH4)2CO3 in ammonia water to obtain solution B, drop solution A into solution B under water bath heating, age, filter, wash, dry, and perform stepwise calcination to obtain the hydrogen transfer material.

6. The hydrogen transfer material for propane dehydrogenation reaction according to claim 4, characterized in that, The sol-gel method includes the following steps: Dissolve the nitrate containing element A, the nitrate containing element B and citric acid in deionized water, perform rotary evaporation, obtain powder through foaming, and perform stepwise calcination to obtain the hydrogen transfer material.

7. The hydrogen transfer material for propane dehydrogenation reaction according to claim 4, characterized in that, The solid-phase synthesis method includes the following steps: Mix and ball-mill the oxide containing element A and the oxide containing element B, calcine, grind and press into tablets, then perform the second calcination, crush and grind, and then press and calcine again to obtain the hydrogen transfer material.

8. Use of a hydrogen transfer material according to any one of claims 1 - 7 in a propane dehydrogenation reaction, characterized in that, The hydrogen transfer material is used together with a propane dehydrogenation catalyst, and the propane dehydrogenation catalyst is one of Cr2O3 / Al2O3 or PtSn / Al2O3.

9. Use of a hydrogen transfer material according to claim 8 in a propane dehydrogenation reaction, characterized in that, The mass ratio of the hydrogen transfer material to the propane dehydrogenation catalyst is 0.1 - 2.

10. Use of a hydrogen transfer material according to claim 8 in a propane dehydrogenation reaction, characterized in that, The temperature of the propane dehydrogenation reaction is 420 to 550 °C, and the reaction space velocity is 0.1 to 10 h -1 .

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