Use of a monatomic ruthenium-based catalyst for the dehydrogenation of propane to propylene
By preparing single-atom ruthenium-based catalysts on nitrogen-doped carbon materials, the problems of low catalyst activity, poor selectivity, and poor stability in existing technologies have been solved, achieving high selectivity and stability, making them suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2022-10-08
- Publication Date
- 2026-06-23
Smart Images
Figure BDA0003878931880000091 
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Abstract
Description
Technical Field
[0001] This invention relates to the application of a single-atom ruthenium-based catalyst in the dehydrogenation of propane to propylene. The catalyst is a single-atom ruthenium supported on a nitrogen-doped carbon material, with the single atom coordinated with nitrogen, which can achieve highly active and selective conversion of propane to propylene. Technical Background
[0002] Propylene is one of the most important raw materials in the petrochemical industry, widely used in the preparation of various chemicals such as polypropylene, polyacrylonitrile, acrolein, acrylic acid, propylene oxide, isopropanol, cumene, and propylene oligomers. With the increasing demand for downstream chemical products, the amount of propylene produced by traditional methods is insufficient to meet market demand. Naphtha steam cracking, catalytic cracking of light diesel oil, and other petroleum byproducts are the main production methods for propylene [Petroleum Refining & Chemicals, 2019, 12, 102-108]. With technological advancements and process optimization, the propylene yield of steam cracking and catalytic cracking units has decreased. Propane catalytic dehydrogenation (PDH) to propylene and methanol-to-olefins have become important pathways to increase propylene production.
[0003] In recent years, shale gas has been extensively extracted and utilized. Besides abundant methane (80-90%), ethane and propane are the main associated gases in shale gas [Ind. Eng. Chem. Res. 2012, 51, 10571-10585]. The abundant and inexpensive propane has spurred the rapid development of propane-to-propylene processes. Compared to propane oxidative dehydrogenation to propylene, direct propane dehydrogenation offers a higher overall yield and lower equipment costs. This technology was industrialized in the 1990s, primarily through the Oleflex process of UOP in the United States and the Catofin process of ABB Lummus [Modern Chemical Industry, 2019, 48, 1806-1815]. The Catofin process was the earliest developed, employing a Cr2O3 / Al2O3 catalyst system. This catalyst has high dehydrogenation activity but a short lifespan, requiring regeneration every 8-15 minutes. UOP's Oleflex process uses a PtSn / Al2O3 catalyst, which offers advantages such as stable propylene yield and low catalyst consumption. However, its drawbacks include the need for large amounts of H2 as a diluent and frequent regeneration. Furthermore, Pt-based metals are expensive, resulting in high catalyst costs. Compared to industrially used Pt-based and Cr-based catalysts, developing a lower-cost, non-toxic, and highly active, selective, and stable propane dehydrogenation catalyst for propylene production is of significant importance. Summary of the Invention
[0004] To address the problems existing in the prior art, this invention provides an application of a single-atom ruthenium-based catalyst in the dehydrogenation of propane to propylene. The single-atom ruthenium-based catalyst of this invention is low in cost, non-toxic, harmless, and exhibits high activity, high selectivity, and high stability.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows:
[0006] An application of a single-atom ruthenium-based catalyst in the dehydrogenation of propane to propylene, wherein the active component of the single-atom ruthenium-based catalyst is ruthenium, which is dispersed in single-atom form and coordinated with nitrogen species, and the support is a nitrogen-doped carbon material; the mass content of ruthenium is 0.1-2.0% of the support mass, and the mass content of nitrogen is 6-15% of the support mass.
[0007] Furthermore, the ruthenium content is preferably 0.5-1.5% of the carrier mass, and the nitrogen content is preferably 12-15% of the carrier mass.
[0008] Further, the process includes the following steps: controlling the volume content of propane in the feed gas to be 1-50%, the volume ratio of propane to H2 in the feed gas to be 0.25-4, using one or two of He or N2 as the balance gas, and ensuring the total pressure of the gas introduced into the reactor is atmospheric pressure, with a total space velocity of 10-200 L / g. cat The reaction proceeds at a rate of 500–650°C per hour through a reactor containing a catalyst.
[0009] Furthermore, the reactor comprises a continuous fixed-bed reactor; the pressure of the propane feed gas is 20–50 kPa, the volume ratio of propane to H2 in the propane feed gas is 0.5–2, and the total space velocity is 10–100 L / g. cat / h, the reaction temperature is 550~600℃.
[0010] Furthermore, the catalyst operates continuously for more than 100 hours, and the catalyst conversion rate decreases by less than 10%. After the reaction, the catalyst is calcined in air at 300-400°C to remove carbon deposits, and then regenerated and reused after being treated with H2 at 500-600°C.
[0011] Furthermore, the preparation method of the single-atom ruthenium-based catalyst includes: grinding and uniformly mixing a ruthenium precursor and a nitrogen-containing precursor, and then pyrolyzing the mixture at high temperature to obtain the single-atom ruthenium-based catalyst; the ruthenium precursor includes one or more of ruthenium acetylacetonate, carbon-based ruthenium, ruthenium chloride, and ruthenium nitrate; the nitrogen-containing precursor includes any two or more of dicyandiamine, alanine, cysteine, and o-phenanthroline.
[0012] Furthermore, the ruthenium precursor is ruthenium acetylacetonate; the nitrogen-containing precursor is dicyandiamine and alanine.
[0013] Furthermore, the high-temperature pyrolysis includes: in a N2 atmosphere, first heating to 600℃ at a rate of 5-10℃ / min for 1-3 hours, and then heating to 700-900℃ for 1-3 hours.
[0014] The nitrogen-doped carbon-supported Ru catalyst involved in this invention has the characteristics of Ru metal being dispersed in single atoms and a nitrogen-rich coordination environment. When applied to the direct dehydrogenation process of propane, it has advantages such as high yield of propylene per unit and propylene selectivity of up to 95%. It can be activated and regenerated in the high-concentration propane dehydrogenation process.
[0015] Compared with the prior art, the essential features of this invention are:
[0016] 1. The catalyst prepared by this invention can convert propane into propylene with high selectivity up to ~95%, and the propylene yield per unit mass can be comparable to that of industrial PtSn / Al2O3. The catalyst has excellent stability and performs stably in the propane dehydrogenation reaction. It only undergoes slight deactivation after 100 hours of continuous operation. After decarbonization by air calcination and re-reduction, the catalyst can be regenerated and reused.
[0017] 2. The Ru-based catalyst of this invention is significantly different from the currently used industrial PtSn / Al2O3 and Cr-based catalysts. Ru metal is cheaper than Pt metal, has no toxicity compared to Cr-based catalysts, and the nitrogen-doped carbon support is inexpensive and readily available, making it suitable for industrial applications;
[0018] 3. The preparation process of the present invention is simple. The active metal precursor and the support precursor are directly ball-milled and mixed, and the active metal Ru is dispersed in the form of single atoms and coordinated with nitrogen species by high-temperature pyrolysis. Compared with the traditional impregnation method, the active metal of the catalyst of the present invention is more firmly bonded to the support, the catalytic active sites are not easily lost, and it is easy to regenerate and reuse. Attached Figure Description
[0019] Figure 1 The figures show electron microscope (EM) images of 1Ru / NC prepared in Example 3 and 1RuNP / NC prepared in Comparative Example 2. In the figures, a is an EEM image of 1Ru / NC prepared in Example 3; b is a magnified view of a; c is an EEM image of 1RuNP / NC prepared in Comparative Example 2; and d is a particle size distribution diagram of 1RuNP / NC.
[0020] Figure 2 The diagram shows the reactivity and selectivity of 1Ru / NC prepared in Example 3 of this invention.
[0021] Figure 3 The reaction stability diagram is shown for 1Ru / NC prepared in Example 3 of this invention.
[0022] Figure 4 a is an electron microscope image of the 1Ru / NC prepared in Example 3 of this invention after reaction; b is a magnified view of a.
[0023] Figure 5 This is a diagram showing the regeneration of the 1Ru / NC catalyst at high concentrations.
[0024] Figure 6 The graph shows a performance comparison between 0.1Ru / AC and 0.1Ru / NC.
[0025] Figure 7 The graph shows a comparison of deactivation rates and propylene yields between 1Ru / NC and commercial PtSn / Al2O3 catalysts. Detailed Implementation
[0026] The following embodiments will help to understand the present invention, but the scope of protection of the present invention is not limited to these embodiments.
[0027] The present invention will now be described in detail with reference to embodiments.
[0028] Example 1: Preparation and Performance Testing of 0.1Ru / NC Catalyst
[0029] 4 mg of ruthenium acetylacetone (RuPc), 12 g of dicyandiamine, and 3 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalyst, denoted as 0.1Ru / NC. (The number 0.1 in 0.1Ru / NC means that the Ru content is 0.1% of the support mass). Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 520–600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h. The stability test temperature was 600℃, while other reaction conditions remained unchanged.
[0030] Example 2: Preparation and Performance Testing of 0.5Ru / NC Catalyst
[0031] 20 mg of ruthenium acetylacetone (RuPc), 12 g of dicyandiamine, and 3 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalyst, denoted as 0.5Ru / NC. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0032] Example 3: Preparation and Performance Testing of 1Ru / NC Catalyst
[0033] 40 mg of ruthenium acetylacetone (RuPc), 12 g of dicyandiamine, and 3 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalyst, denoted as 1Ru / NC. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0034] Example 4: Preparation and Performance Testing of 2Ru / NC Catalyst
[0035] 80 mg of ruthenium acetylacetone (RuPc), 12 g of dicyandiamine, and 3 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalyst, denoted as 2Ru / NC. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0036] Example 5: Preparation and performance testing of 1Ru / NC-2 (adjusted support N content) catalyst
[0037] 40 mg of ruthenium acetylacetone (RuPc), 11 g of dicyandiamine, and 4 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalyst, denoted as 1Ru / NC-2. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0038] Example 6: Preparation and performance testing of 1Ru / NC-3 (adjusted support N content) catalyst
[0039] 40 mg of ruthenium acetylacetone (RuPc), 10 g of dicyandiamine, and 5 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalyst, denoted as 1Ru / NC-3. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0040] Example 7: Preparation and Performance Testing of 1Ru / NC-800 (Adjusted Pyrolysis Temperature) Catalyst
[0041] 40 mg of ruthenium acetylacetone (RuPc), 12 g of dicyandiamine, and 3 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 800 °C for 1 h to obtain the target catalyst, denoted as 1Ru / NC-800. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0042] Example 8: Preparation and performance testing of 1Ru / NC-700 (adjusted pyrolysis temperature) catalyst
[0043] 40 mg of ruthenium acetylacetone (RuPc), 12 g of dicyandiamine, and 3 g of alanine were weighed and mixed thoroughly, and ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 700 °C for 1 h to obtain the target catalyst, denoted as 1Ru / NC-700. Before testing, the catalyst was treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0044] Example 9: Preparation and performance testing of 1Ru / NC catalysts (different Ru precursors)
[0045] 63 mg of ruthenium carbonyl or 21 mg of ruthenium trichloride (Ru net content 10 mg each) were weighed out and mixed thoroughly with 12 g of dicyandiamine and 3 g of alanine. The mixture was ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere by increasing the temperature at 10 °C / min, followed by pyrolysis at 900 °C for 1 h to obtain the target catalysts, denoted as 1Ru / NC-t (ruthenium carbonyl precursor) and 1Ru / NC-s (ruthenium trichloride precursor), respectively. Before testing, the catalysts were treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0046] Example 10: Preparation and performance testing of 1Ru / NC catalysts (different nitrogen-containing precursors)
[0047] 40 mg of ruthenium acetylacetone (RuPc) was weighed and mixed thoroughly with 15 g of cysteine or 15 g of o-phenanthroline. The mixture was ball-milled at 400 rpm for 3 h. The mixture was then placed in a tube furnace and pyrolyzed at 600 °C for 1 h under a N2 atmosphere, with the temperature increased at 10 °C / min. The temperature was then further increased to 900 °C for 1 h to obtain the target catalysts, denoted as 1Ru / NC-b (cysteine precursor) and 1Ru / NC-l (o-phenanthroline precursor), respectively. Before testing, the catalysts were treated with H2 at 600 °C for 1 h and reacted in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h.
[0048] Comparative Example 1: Preparation and Performance Testing of 0.1Ru / AC Catalyst
[0049] Ruthenium acetylacetone was loaded onto an activated carbon support via impregnation and treated with H2 at 600 °C for 1 h to obtain the target catalyst, denoted as 0.1Ru / AC, where the Ru content was 1% of the support mass. The reaction was carried out in a continuous fixed-bed reactor packed with the catalyst under the following conditions: reaction temperature 600 °C, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18 L / g. cat / h. Comparative Example 2:1 RuNP / NC catalyst preparation and performance testing.
[0050] 12g of dicyandiamine and 3g of alanine were weighed and mixed evenly, and ball-milled at 400rpm for 3h. The mixture was placed in a tube furnace and pyrolyzed at 600℃ for 1h under N2 atmosphere by heating at 10℃ / min, followed by heating at 900℃ for 1h to obtain nitrogen-doped carbon support (NC). 40mg of ruthenium acetylacetone was loaded onto 1g of NC support by impregnation, and treated with H2 at 600℃ for 1h to obtain the target catalyst, denoted as 1RuNP / NC, where the Ru mass content accounted for 1% of the support mass. The reaction was carried out in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600℃, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18L / g. cat / h.
[0051] Comparative Example 3: Preparation and Performance Testing of 6RuNP / NC Catalyst
[0052] 12g of dicyandiamine and 3g of alanine were weighed and mixed evenly, and ball-milled at 400rpm for 3h. The mixture was placed in a tube furnace and pyrolyzed at 600℃ for 1h under N2 atmosphere by heating at 10℃ / min, followed by heating at 2℃ / min to 900℃ for 1h to obtain nitrogen-doped carbon support (NC). 240mg of ruthenium acetylacetone was loaded onto 1g of NC support by impregnation, and treated with H2 at 600℃ for 1h to obtain the target catalyst, denoted as 6RuNP / NC, where Ru content accounted for 6% of the support mass. The reaction was carried out in a continuous fixed-bed reactor containing the catalyst. The test conditions were: reaction temperature 600℃, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure in the fixed-bed reactor was atmospheric pressure, and total space velocity was 18L / g. cat / h.
[0053] Comparative Example 4: Performance Testing of Commercial PtSn / Al2O3
[0054] The commercial PtSn / Al2O3 composition is 0.5 wt% Pt, 1.5 wt% Sn, and Al2O3 support. The reaction was carried out in a continuous fixed-bed reactor packed with catalyst under the following conditions: reaction temperature 600℃, C3H8:H2:He = 1:1:3 (volume ratio), total gas pressure introduced into the fixed-bed reactor at atmospheric pressure, and total space velocity 18 L / g. cat / h.
[0055] result:
[0056] The formulas for calculating all ethane conversion rates and ethylene selectivity in this invention are as follows:
[0057] C3H8 conversion=(C3H8(in)–C3H8(out)) / C3H8(in)
[0058] C3H6 selectivity=C3H6(out) / (C3H8(in)–C3H8(out))
[0059] Where C3H8(in) represents the amount of propane in the reaction gas; C3H8(out) represents the amount of propane in the product; and C3H6(out) represents the amount of propylene in the product.
[0060] like Figure 1 The transmission electron microscope (TEM) images of the catalysts prepared in Example 3 and Comparative Example 2 of this invention show that Ru in the 1Ru / NC catalyst is dispersed as single atoms, while Ru in the 1RuNP / NC catalyst is mainly composed of nanoparticles with a particle size of approximately 1.1 nm.
[0061] like Figure 2 As shown in the test graph of propane dehydrogenation performance of the 1Ru / NC catalyst prepared in Example 3 of the present invention, the conversion rate of propane increases from 14% to 33% as the reaction temperature increases from 520℃ to 600℃, and the selectivity of propylene is always greater than 94%, indicating that the 1Ru / NC catalyst has good activity and selectivity in propane dehydrogenation reaction.
[0062] like Figure 3 As shown in the figures, the propane dehydrogenation stability test results of the catalysts prepared in Examples 3, 2, and 3 of this invention are as follows: The results show that after 100 h of reaction, the activity of the 1Ru / NC catalyst decreased from 30% to 26%, while the selectivity remained above 90%. In contrast, after 34 h of reaction, the activity of the 6RuNP / NC catalyst decreased from 15% to 7%, a reduction of nearly 50%, with a selectivity less than 80%; and after 34 h of reaction, the activity of the 1RuNP / NC catalyst decreased from 12% to 6%, with a selectivity less than 83%. These results indicate that, compared to nanoparticle Ru catalysts, the single-atom 1Ru / NC catalyst exhibits superior propane dehydrogenation stability.
[0063] like Figure 4 As shown in the electron microscope image of the 1Ru / NC catalyst prepared in Example 3 of this invention after stability testing, it can be seen that Ru in 1Ru / NC still maintains single-atom dispersion after the reaction, indicating that 1Ru / NC has excellent stability.
[0064] like Figure 5 As shown in the figure, the 1Ru / NC catalyst prepared in Example 3 of the present invention was tested in a regeneration experiment. The results show that after the 1Ru / NC catalyst was deactivated under a high concentration reaction atmosphere (C3H8 / H2 / N2=4:4:2), the catalyst activity was significantly restored after being treated at 400℃ for 1 hour in an air atmosphere, indicating that the catalyst has good regeneration performance.
[0065] like Figure 6 The diagram shows the reaction test results of the 0.1Ru / NC catalyst prepared in Example 1 and the 0.1Ru / AC catalyst in Comparative Example 1. The results show that the propylene selectivity of 0.1Ru / NC is 95%, significantly higher than that of 0.1Ru / AC (79%). Compared to activated carbon supports, 0.1Ru / NC exhibits higher propylene selectivity when the support is nitrogen-doped carbon, indicating that nitrogen in the support is beneficial for improving propylene selectivity.
[0066] like Figure 7 The figure shows the test results of 1Ru / NC and industrial PtSn / Al2O3 catalysts in Example 3 of this invention. It can be seen that under the conditions of 560℃ and C3H8 / H2 / N2 = 1:1:3, the deactivation rate of 1Ru / NC is 0.0042 h⁻¹. -1 , with PtSn / Al2O3 at 0.0035h -1 The yields are similar. The propylene yield at 1 Ru / NC is 0.63 g. C3H8 g cat -1 h -1 0.64g of PtSn / Al2O3 C3H8 g cat - 1 h -1 These results indicate that 1Ru / NC exhibits activity and stability similar to those of industrial PtSn / Al2O3 catalysts.
[0067] Table 1. Propane dehydrogenation performance of different catalysts at 600℃
[0068]
[0069] Table 1 shows the performance results of the catalysts prepared in Examples 1-8 and Comparative Examples 1-4 in propane dehydrogenation to propylene at 600°C. As can be seen from sequences 1 to 4, the propane conversion gradually increases with the increase of Ru content (0.1-2.0%) in the catalyst, and the propylene selectivity is greater than 93%, indicating that Ru is the active center for propane dehydrogenation.
[0070] Sequences 3, 5, and 6 show that the nitrogen content of the support can be adjusted by regulating the proportion of nitrogen-containing precursors. XPS analysis shows that the N / Ru mass ratios in 1Ru / NC, 1Ru / NC-2, and 1Ru / NC-3 are 15.0, 13.2, and 12.0, respectively. Reaction performance analysis indicates that propylene selectivity decreases with decreasing N / Ru ratio, suggesting that nitrogen in the support is beneficial for improving propylene selectivity.
[0071] As can be seen from sequences 3, 6, and 7, the propane conversion rate decreases with decreasing pyrolysis temperature, indicating that 1Ru / NC-900 prepared by pyrolysis at 900 degrees has the best propane dehydrogenation performance.
[0072] From sequences 1 and 8, when the support is activated carbon (nitrogen-free), the propylene selectivity of 0.1Ru / AC is 79%, which is significantly lower than the 95% of 0.1Ru / NC, indicating that nitrogen in the support is beneficial to improving the selectivity of propane dehydrogenation.
[0073] As can be seen from sequences 3, 9, and 10, when Ru is in nanoparticle form, the conversion rate of propane and the selectivity of propylene are significantly reduced compared to 1Ru / NC, indicating that 1Ru / NC with Ru in single-atom dispersion has better propane dehydrogenation performance.
[0074] Sequences 3, 12, and 13 show that the 1Ru / NC-t catalyst, obtained using carbon-based ruthenium as a precursor, exhibits a propylene selectivity of 90%, slightly lower than the 94% of 1Ru / NC. The 1Ru / NC-s catalyst, obtained using ruthenium trichloride as a precursor, shows a propane conversion of 26%, lower than the 32% of 1Ru / NC. This indicates that the catalyst obtained using ruthenium acetylacetonate as a precursor has superior propane dehydrogenation performance.
[0075] Sequences 3, 14, and 15 show that the 1Ru / NC-b catalyst obtained using cysteine as a precursor has a propylene selectivity of 89%, while the 1Ru / NC-l catalyst obtained using o-phenanthroline as a precursor has a propylene selectivity of 90%, which is lower than the 94% of 1Ru / NC. This indicates that the catalysts obtained using dicyandiamine and alanine as nitrogen source precursors have better propane dehydrogenation performance.
[0076] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. The application of a single-atom ruthenium-based catalyst in the dehydrogenation of propane to propylene, characterized in that: The active component of the single-atom ruthenium-based catalyst is ruthenium, which is dispersed in single-atom form and coordinated with nitrogen species. The support is a nitrogen-doped carbon material. The mass content of ruthenium is 0.1-2.0% of the support mass, and the mass content of nitrogen is 6-15% of the support mass. The process includes the following steps: controlling the propane volume content of the feed gas to 1-50%, the volume ratio of propane to H2 to be 0.25-4, using one or two of He or N2 as the balance gas, and ensuring the total gas pressure introduced into the reactor is atmospheric pressure, with a total space velocity of 10-200 L / g. cat / h, through a reactor containing a catalyst, at a reaction temperature of 500~650°C; The catalyst operates continuously for more than 100 hours, and the catalyst conversion rate decreases by less than 10%. After the reaction, the catalyst is calcined in air at 300~400°C to remove carbon deposits, and then regenerated and reused after being treated with H2 at 500~600°C. The method for preparing the single-atom ruthenium-based catalyst includes: grinding and uniformly mixing a ruthenium precursor and a nitrogen-containing precursor, and then pyrolyzing the mixture at high temperature to obtain the single-atom ruthenium-based catalyst; the ruthenium precursor includes one or more of ruthenium acetylacetonate, carbon-based ruthenium, ruthenium chloride, and ruthenium nitrate; the nitrogen-containing precursor includes any two or more of dicyandiamine, alanine, cysteine, and o-phenanthroline.
2. The application according to claim 1, characterized in that: The ruthenium content is 0.5-1.5% of the carrier mass, and the nitrogen content is 12-15% of the carrier mass.
3. The application according to claim 1, characterized in that: The reactor includes a continuous fixed-bed reactor; the pressure of the propane feed gas is 20-50 kPa, the volume ratio of propane to H2 in the feed gas is 0.5-2, and the total space velocity is 10-100 L / g. cat / h, the reaction temperature is 550~600°C.
4. The application according to claim 1, characterized in that: The ruthenium precursor is ruthenium acetylacetonate; the nitrogen-containing precursor is dicyandiamine and alanine.
5. The application according to claim 1, characterized in that: The high-temperature pyrolysis includes: in a N2 atmosphere, first heating at 5~10°C / min to 600°C for 1~3 h, then heating to 700~900°C for 1~3 h.