A dehydrogenation catalyst, a method for preparing the same, and use thereof

Abstract

The application discloses a dehydrogenation catalyst and a preparation method and application thereof. The dehydrogenation catalyst comprises a carrier, an active component and a single-atom acidic site supported on the surface of the carrier; the active component is selected from Pt; the single-atom acidic site is selected from at least one of Nb, Ti, Al, Zr and W; the content of the active component is 0.1-3 wt%; and the content of the single-atom acidic site is 0.1-2 wt%. The acidity of the carrier is regulated by synthesizing the single-atom acidic site, so that the catalyst with high catalytic activity and stability is obtained. The preparation method is simple in operation and convenient for industrial amplification production. Through simple air oxidation regeneration, the activity of the catalyst can be recovered.

Description

Technical Field

[0001] This application relates to a dehydrogenation catalyst, its preparation method, and its application, and belongs to the field of catalysts. Background Technology

[0002] Propylene is a crucial raw material for the production of chemical products such as polypropylene, propylene oxide, and acrylonitrile. Traditional propylene production processes include catalytic cracking and steam cracking of light diesel oil and naphtha. However, due to the rapid depletion of fossil fuels, low selectivity for olefins, and insufficient market supply, traditional propylene production methods can no longer meet the growing demand for propylene. With the discovery of shale gas, direct propane dehydrogenation (PDH) is considered one of the most promising methods for propylene production.

[0003] Propane dehydrogenation is thermodynamically balanced, typically requiring temperatures around 550°C to achieve high propane conversion. However, increasing the temperature increases the rates of CH4 cracking and competing CC4 cracking side reactions. Therefore, reaction conditions should be adjusted to suppress side reactions and improve propylene selectivity and yield. Currently, the most commonly used catalysts in propane dehydrogenation are Pt-based and CrO2-based catalysts. X Basic catalyst. CrO X Pt-based catalysts are widely used due to their low cost. However, severe side reactions lead to their rapid deactivation, and they are toxic and environmentally unfriendly. Pt-based catalysts exhibit good propane dehydrogenation activity due to their affinity for the CH bond of propane, but they are prone to coking and sintering at high temperatures, thus limiting their further development in propane dehydrogenation.

[0004] Therefore, further research is needed on the deactivation of Pt-based catalysts to improve catalyst stability and propylene yield. Deactivation of Pt-based catalysts is generally due to the formation of coke on the active site surface at high temperatures, leading to active site poisoning or restricting reactant access to the active sites, resulting in rapid catalyst deactivation; or the active components slowly sinter and accumulate, reducing the number of exposed active sites on the catalyst surface. Studies have shown that coking can be suppressed by adjusting the acidity of the support. Selecting a support with high specific surface area and suitable acidity is preferred; further control of the support acidity can lead to higher olefin selectivity and activity stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a propane dehydrogenation catalyst promoted by a single-atom acidic site and its preparation method. The catalyst prepared by this method can achieve regulation of the acidity of the support and has good catalytic activity, high selectivity and stability.

[0006] According to one aspect of this application, a dehydrogenation catalyst is provided, the dehydrogenation catalyst comprising a support and an active component and a single-atom acidic site supported on the surface of the support;

[0007] The active component is selected from Pt;

[0008] The single-atom acidic site is selected from at least one of Nb, Ti, Al, Zr, and W;

[0009] In the dehydrogenation catalyst, the content of the active component is 0.1–3 wt%.

[0010] In the dehydrogenation catalyst, the content of the single-atom acidic site is 0.1–2 wt%.

[0011] The carrier is selected from microporous materials;

[0012] Optionally, the carrier is selected from at least one of silicon-based SiO2, MCM-41, SBA-15, and Silicate-1.

[0013] The active ingredient also contains auxiliary elements;

[0014] The auxiliary element is selected from at least one of Zn, Sn, Ga, In, and Co;

[0015] In the dehydrogenation catalyst, the content of the auxiliary element is 0.1-5 wt%.

[0016] According to another aspect of this application, a method for preparing the above-mentioned dehydrogenation catalyst is provided, comprising the following steps:

[0017] (1) The support is mixed with an aqueous solution containing a precursor with a single-atom acidic site, dried (I), and calcined (I) to obtain product (I);

[0018] (2) The product I obtained in (1) is immersed in an aqueous solution containing the active component precursor, dried and calcined to obtain the dehydrogenation catalyst.

[0019] The single-atom acidic site precursor is selected from at least one of TiCl4, ammonium metatitanate, titanium oxysulfate, aluminum isopropoxide, aluminum nitrate, aluminum chloride, niobium oxalate, ammonium niobium oxalate, zirconium oxychloride, zirconium nitrate, zirconium acetate, zirconium sulfate, zirconium chloride, ammonium metatungstate, and ammonium paratungstate.

[0020] The aqueous solution containing the precursor with a single acidic site has a content of 0.1 to 2 wt%.

[0021] The mixing process includes impregnation or precipitation.

[0022] The precipitant used for precipitation is at least one of ammonia water, sodium hydroxide aqueous solution, and sodium carbonate aqueous solution, with a pH value of 9 to 12.

[0023] The active component precursor is selected from at least one of H2PtCl6, Zn(NO3)2, SnCl4, Ga(NO3)3, In(NO3)3, and Co(NO3)2;

[0024] The active component precursor is selected from H2PtCl6;

[0025] Preferably, the aqueous solution containing the active component precursor further contains at least one of Zn(NO3)2, SnCl4, Ga(NO3)3, In(NO3)3, and Co(NO3)2;

[0026] The temperature of the drying process I is 60–120°C;

[0027] The drying time for step I is 8–16 hours;

[0028] The drying process described in section I is vacuum drying;

[0029] The temperature of the calcination I is 500–900°C;

[0030] The roasting time for the first roasting step is 2 to 12 hours.

[0031] The temperature of the drying II process is 80–120°C;

[0032] The drying time for step II is 0.05–3 hours;

[0033] The temperature of calcination II is 500–900°C;

[0034] The roasting time for the second stage is 2 to 12 hours.

[0035] The dehydrogenation catalyst is also subjected to grinding, tableting, and particle screening.

[0036] According to another aspect of this application, a method for dehydrogenating low-carbon alkanes is provided, wherein the low-carbon alkanes are selected from at least one of propane and ethane;

[0037] Includes the following steps:

[0038] A raw material containing low-carbon alkanes is contacted with a catalyst and reacted to obtain a product containing low-carbon olefins.

[0039] The catalyst is selected from the dehydrogenation catalysts according to any one of claims 1 to 3.

[0040] The reaction temperature is 300–700°C;

[0041] The mass hourly space velocity of the raw material is 4–12 h. -1 .

[0042] The dehydrogenation catalyst can be regenerated;

[0043] The regeneration is carried out in an air atmosphere at 500–600°C and a gas space velocity of 1000–5000 h⁻¹. -1 Regeneration takes 2-20 hours.

[0044] The beneficial effects that this application can produce include:

[0045] (1) The present invention regulates the acidity of the support by synthesizing single-atom acidic sites, thereby obtaining a catalyst with high catalytic activity and stability.

[0046] (2) The catalyst preparation method of the present invention is simple to operate and easy to scale up for industrial production.

[0047] (3) The catalyst activity can be restored by simple air oxidation regeneration. Attached Figure Description

[0048] Figure 1 This is a stability test diagram of the propane dehydrogenation reaction of the catalyst in Example 1.

[0049] Figure 2 This is a stability test diagram of the propane dehydrogenation reaction after the catalyst in Example 3 underwent continuous regeneration five times. Detailed Implementation

[0050] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0051] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0052] Example 1

[0053] A certain amount of aluminum isopropoxide was weighed and dissolved in isopropanol. Then, a certain amount of MCM-41 support was impregnated with the aluminum isopropoxide solution. The solid product was placed in a vacuum oven and heated at 80°C for 12 hours; then calcined at 500°C for 2 hours to obtain an acid-controlled support. Next, certain amounts of H₂PtCl₆·6H₂O and Zn(NO₃)₂·6H₂O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H₂PtCl₆·6H₂O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600°C for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0054] Example 2

[0055] A certain amount of aluminum isopropoxide was weighed and dissolved in isopropanol. Then, a certain amount of SBA-15 support was impregnated with the aluminum isopropoxide solution. The solid product was placed in a vacuum oven and heated at 80°C for 12 hours; then calcined at 500°C for 2 hours to obtain an acid-controlled support. Next, certain amounts of H₂PtCl₆·6H₂O and Zn(NO₃)₂·6H₂O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H₂PtCl₆·6H₂O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled SBA-15 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600°C for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0056] Example 3

[0057] A certain amount of aluminum isopropoxide was weighed and dissolved in isopropanol. Then, a certain amount of SiO2 support was impregnated with the aluminum isopropoxide solution. The solid product was placed in a vacuum oven and heated at 80℃ for 12 hours; then calcined at 500℃ for 2 hours to obtain an acid-controlled support. Next, certain amounts of H2PtCl6·6H2O and Zn(NO3)2·6H2O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H2PtCl6·6H2O and Zn(NO3)2·6H2O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled SiO2 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600℃ for 2 hours, then ground, pressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0058] Example 4

[0059] A certain amount of aluminum isopropoxide was weighed and dissolved in isopropanol. Then, a certain amount of MCM-41 support was impregnated with the aluminum isopropoxide solution. The solid product was placed in a vacuum oven and heated at 80°C for 12 hours; then calcined at 500°C for 2 hours to obtain an acid-controlled support. Next, certain amounts of H₂PtCl₆·6H₂O and SnCl₄·5H₂O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H₂PtCl₆·6H₂O solution was pipetted to prepare a PtSn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Sn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600°C for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0060] Example 5

[0061] A certain amount of aluminum isopropoxide was weighed and dissolved in isopropanol. Then, a certain amount of MCM-41 support was impregnated with the aluminum isopropoxide solution. The solid product was placed in a vacuum oven and heated at 80°C for 12 hours; then calcined at 500°C for 2 hours to obtain an acid-controlled support. Next, certain amounts of H₂PtCl₆·6H₂O and Ga(NO₃)₃·xH₂O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H₂PtCl₆·6H₂O solution was pipetted to prepare a PtGa mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Ga loading of 1.7 wt%. The impregnated sample was dried, calcined at 600°C for 2 hours, then ground, pressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0062] Example 6

[0063] A certain amount of aluminum isopropoxide was weighed and dissolved in isopropanol. Then, a certain amount of MCM-41 support was impregnated with the aluminum isopropoxide solution. The solid product was placed in a vacuum oven and heated at 80°C for 12 hours; then calcined at 500°C for 2 hours to obtain an acid-controlled support. Next, a certain amount of H₂PtCl₆·6H₂O and In(NO₃)₃ were weighed and dissolved in deionized water to prepare a solution. A certain volume of the H₂PtCl₆·6H₂O and In(NO₃)₃ solutions were measured using a pipette to prepare a PtIn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and an In loading of 1.7 wt%. The impregnated sample was dried, calcined at 600°C for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0064] Example 7

[0065] A certain amount of Zr(NO3)4·5H2O was weighed and dissolved in deionized water. Then, a certain amount of MCM-41 support was impregnated with zirconium nitrate solution. The solid product was placed in a vacuum oven and heated at 80℃ for 12 hours; then calcined at 500℃ for 2 hours to obtain an acid-controlled support. Next, certain amounts of H2PtCl6·6H2O and Zn(NO3)2·6H2O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H2PtCl6·6H2O and Zn(NO3)2·6H2O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600℃ for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0066] Example 8

[0067] A certain amount of ammonium metatungstate was weighed and dissolved in deionized water. Then, a certain amount of MCM-41 support was impregnated with the ammonium metatungstate solution. The solid product was placed in a vacuum oven and heated at 80°C for 12 hours; then calcined at 500°C for 2 hours to obtain an acid-controlled support. Next, certain amounts of H₂PtCl₆·6H₂O and Zn(NO₃)₂·6H₂O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H₂PtCl₆·6H₂O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600°C for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0068] Example 9

[0069] A certain amount of Nb(HC2O4)5 was weighed and dissolved in deionized water. Then, a certain amount of MCM-41 support was impregnated with niobium oxalate solution. The solid product was placed in a vacuum oven and heated at 80℃ for 12 hours; then calcined at 500℃ for 2 hours to obtain an acid-controlled support. Next, certain amounts of H2PtCl6·6H2O and Zn(NO3)2·6H2O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H2PtCl6·6H2O and Zn(NO3)2·6H2O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600℃ for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0070] Example 10

[0071] A certain amount of TiCl4 was weighed and dissolved in deionized water. Then, a certain amount of MCM-41 support was impregnated with titanium tetrachloride solution. The solid product was placed in a vacuum oven and heated at 80℃ for 12 hours; then calcined at 500℃ for 2 hours to obtain an acid-controlled support. Next, certain amounts of H2PtCl6·6H2O and Zn(NO3)2·6H2O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H2PtCl6·6H2O and Zn(NO3)2·6H2O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600℃ for 2 hours, then ground, pressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0072] Comparative Example 1

[0073] A certain amount of Ce(NO3)3·6H2O was weighed and dissolved in deionized water. Then, a certain amount of MCM-41 support was impregnated with niobium oxalate solution. The solid product was placed in a vacuum oven and heated at 80℃ for 12 hours; then calcined at 500℃ for 2 hours to obtain the support. Next, certain amounts of H2PtCl6·6H2O and Zn(NO3)2·6H2O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H2PtCl6·6H2O and Zn(NO3)2·6H2O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600℃ for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0074] Comparative Example 2

[0075] A certain amount of Mn(NO3)2 was weighed and dissolved in deionized water. Then, a certain amount of MCM-41 support was impregnated with titanium tetrachloride solution. The solid product was placed in a vacuum oven and heated at 80℃ for 12 hours; then calcined at 500℃ for 2 hours to obtain the support. Next, certain amounts of H2PtCl6·6H2O and Zn(NO3)2·6H2O were weighed and dissolved in deionized water to prepare solutions. A certain volume of each H2PtCl6·6H2O and Zn(NO3)2·6H2O solution was pipetted to prepare a PtZn mixed solution, which was then used to impregnate the acid-controlled MCM-41 support, resulting in a Pt loading of 1 wt% and a Zn loading of 1.7 wt%. The impregnated sample was dried, calcined at 600℃ for 2 hours, then ground, compressed into tablets at 20 MPa, crushed, and sieved to obtain 40-60 mesh particles for later use.

[0076] The samples obtained in Examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and Comparative Examples 1 and 2 were used as catalysts for performance testing. The specific test conditions were as follows: catalyst dosage was 0.25 g, reaction stability test temperature was 600 °C, and propane mass hourly space velocity was 4 h⁻¹. -1 The ratio of propane to hydrogen and nitrogen was 64 vol%:16 vol%:16 vol%. The reactor outlet gas was analyzed online by gas chromatography. The propane dehydrogenation performance results of the above catalysts are shown in Table 1.

[0077] Table 1. Performance results of propane dehydrogenation reaction with different catalysts

[0078]

[0079] Figure 1The graph shows the stability test of the catalyst in the propane dehydrogenation reaction of Example 1. As can be seen from the graph, after 10 hours of reaction, the propane conversion and propylene selectivity of the catalyst did not decrease significantly, indicating that the catalyst has good stability.

[0080] Figure 2 This is a stability test diagram of the propane dehydrogenation reaction after the catalyst in Example 3 underwent continuous regeneration five times.

[0081] The figure shows that the catalyst still has good reaction performance after being regenerated 5 times and running for nearly 900 hours, indicating that the catalyst can be restored to its activity through simple air oxidation regeneration.

[0082] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A dehydrogenation catalyst, characterized in that, The dehydrogenation catalyst includes a support and an active component and a single-atom acidic site supported on the surface of the support; The active component is selected from Pt; The single-atom acidic site is selected from at least one of Nb, Ti, Zr, and W; In the dehydrogenation catalyst, the content of the active component is 0.1~3 wt%; In the dehydrogenation catalyst, the content of the single-atom acidic site is 0.1~2wt%; The active ingredient also contains auxiliary elements; The auxiliary element is selected from at least one of Zn, Sn, Ga, In, and Co; In the dehydrogenation catalyst, the content of the auxiliary element is 0.1~5wt%.

2. The dehydrogenation catalyst according to claim 1, characterized in that, The carrier is selected from microporous materials; The carrier is selected from at least one of silicon-based SiO2, MCM-41, SBA-15, and Silicate-1.

3. A method for preparing the dehydrogenation catalyst according to any one of claims 1 to 2, Its features are, Includes the following steps: (1) The support is mixed with an aqueous solution containing a precursor with a single-atom acidic site, dried (I), and calcined (I) to obtain product (I); (2) The product I obtained in (1) is immersed in an aqueous solution containing the active component precursor, dried and calcined to obtain the dehydrogenation catalyst.

4. The preparation method according to claim 3, characterized in that, The single-atom acidic site precursor is selected from at least one of TiCl4, ammonium metatitanate, titanium oxysulfate, aluminum isopropoxide, aluminum nitrate, aluminum chloride, niobium oxalate, ammonium niobium oxalate, zirconium oxychloride, zirconium nitrate, zirconium acetate, zirconium sulfate, zirconium chloride, ammonium metatungstate, and ammonium paratungstate. In the aqueous solution containing the precursor with a single-atom acidic site, the content of the precursor with the single-atom acidic site is 0.1~2wt%.

5. The preparation method according to claim 3, characterized in that, The active component precursor is selected from H2PtCl6; The aqueous solution containing the active component precursor also contains at least one of Zn(NO3)2, SnCl4, Ga(NO3)3, In(NO3)3, and Co(NO3)2; The aqueous solution containing the active component precursor has an active component precursor content of 0.1~3 wt%.

6. The preparation method according to claim 3, characterized in that, The temperature of the drying process I is 60~120℃; The drying time for step I is 8-16 hours; The drying process described in section I is vacuum drying; The temperature of the calcination I is 500~900℃; The roasting time for the first roasting step is 2 to 12 hours.

7. The preparation method according to claim 3, characterized in that, In step (2), the drying temperature is 80~120℃; The drying time is 0.05~3 hours; The roasting temperature is 500~900℃; The roasting time is 2 to 12 hours.

8. A method for dehydrogenating low-carbon alkanes, characterized in that, The low-carbon alkane is selected from at least one of propane and ethane; Includes the following steps: A raw material containing low-carbon alkanes is contacted with a catalyst and reacted to obtain a product containing low-carbon olefins. The catalyst is selected from the dehydrogenation catalysts according to any one of claims 1 to 2.

9. The method according to claim 8, characterized in that, The reaction temperature is 300~700℃; The mass hourly space velocity of the raw material is 4-12 h. -1 .

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