An alkane hydroisomerization catalyst, its preparation method and application

Abstract

This invention discloses an alkane hydroisomerization catalyst, its preparation method, and its application. The catalyst comprises Pt / Al₂O₃, Pt-M / C₃N₄, and a molecular sieve, where M is a metal promoter. In Pt / Al₂O₃, Pt exists in the form of nanoclusters, while in Pt-M / C₃N₄, Pt exists in the form of single atoms. When used in alkane isomerization reactions, this catalyst significantly improves the utilization efficiency of Pt metal to obtain the optimal isomer yield and reduces the reaction temperature required to achieve the optimal yield.

Description

Technical Field

[0001] This invention belongs to the field of alkane isomerization reaction, specifically relating to an alkane hydroisomerization catalyst, its preparation method, and its application. Background Technology

[0002] Driven by economic and environmental protection principles, the selective, efficient, and high-quality isomerization of n-alkanes into oil blending components has become increasingly important. The isomerization process of n-alkanes follows a metal-acid dual-center synergistic catalytic reaction mechanism. First, n-alkanes undergo dehydrogenation at a metal site to form n-olefins. Subsequently, the n-olefins diffuse to acidic sites on a molecular sieve and undergo skeletal isomerization, generating isoolefin intermediates. These intermediates then return to the metal sites for hydrogenation to generate the target product, isoalkane. The active metal sites are generally provided by noble metals such as Pt and Pd, primarily used for hydrogen dissociation, alkane dehydrogenation, and subsequent hydrogenation of olefin intermediates. To improve the utilization efficiency of metal centers and reduce catalyst production costs, researchers generally focus on three aspects: improving the dispersion of noble metals, designing noble metal-non-noble metal alloy structures, and developing highly active non-noble metal systems.

[0003] In previous research (Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons. Nature. 2015, 528: 245-248), researchers developed a class of catalysts (Pt-on-Al2O3) where the Pt metal sites are located on alumina. The resulting olefin intermediates preferentially undergo "pore-mouth catalysis," inhibiting the enrichment of olefin intermediates on the Brønsted acid within the micropores of the molecular sieve. This avoids intracrystalline mass transfer of intermediates in deeper pores, achieving efficient synthesis of the target product isomers. However, in this type of catalyst, alumina is an inert matrix in the Pt / Al2O3 component, resulting in a uniform geometry and electronic properties of the Pt sites. This is not conducive to simultaneously achieving the two sub-reactions of alkane dehydrogenation and olefin hydrogenation. The Pt metal utilization efficiency also needs improvement. To obtain the optimal isomer yield, a higher Pt metal loading and a higher reaction temperature are still required, increasing economic and operating costs. Therefore, how to simultaneously optimize the Pt-centered hydrogenation and dehydrogenation mechanism in this system is an urgent problem to be solved. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides an alkane hydroisomerization catalyst, its preparation method, and its applications. When used in the hydroisomerization reaction of n-alkanes, the catalyst of this invention significantly reduces the reaction temperature at which the optimal yield of the desired isomer is obtained.

[0005] The first aspect of the present invention provides an alkane hydroisomerization catalyst, wherein the catalyst comprises Pt / Al2O3, Pt-M / C3N4 and a molecular sieve, M being a metal promoter, wherein Pt in Pt / Al2O3 exists in the form of nanoclusters, and Pt in Pt-M / C3N4 exists in the form of single atoms.

[0006] Furthermore, in the Pt-M / C3N4, Pt is dispersed in M ​​nanoparticles in the form of single atoms.

[0007] Furthermore, the Pt / Al2O3 refers to Pt-containing aluminum oxide, such as Pt-loaded aluminum oxide.

[0008] Furthermore, the Pt-M / C3N4 refers to C3N4 containing Pt and M, such as C3N4 loaded with Pt and M.

[0009] Further, in the catalyst, based on the catalyst mass, the content of Pt / Al2O3 is 5.0wt% to 50.0wt%; the content of Pt-M / C3N4 is 5.0wt% to 50.0wt%; the content of molecular sieve is 20.0wt% to 60.0wt%; the total Pt content is 0.01wt% to 0.1wt%, preferably 0.01wt% to 0.05wt%, wherein the mass ratio of Pt in Pt / Al2O3 to Pt in Pt-M / C3N4 is 0.2 to 20.0, preferably 1.0 to 10.0.

[0010] Further, preferably, in the catalyst, based on the mass of the catalyst, the content of Pt / Al2O3 is 20.0wt% to 45.0wt%; the content of Pt-M / C3N4 is 25.0wt% to 35.0wt%; and the content of molecular sieve is 20.0wt% to 50.0wt%.

[0011] Furthermore, in the Pt / Al2O3, the average particle size of the Pt grains is 0.50 nm to 1.50 nm.

[0012] Furthermore, in the Pt-M / C3N4, M is one or more of Cu, Zn, Mo, Co, W, Ce, Ir, and Re.

[0013] Furthermore, in the Pt-M / C3N4, the average particle size of the M nanoparticles is 1.5 nm to 10.0 nm, for example, but not limited to, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, 4.5 nm, 5.0 nm, 5.5 nm, 6.0 nm, 6.5 nm, 7.0 nm, 7.5 nm, 8.5 nm, 9.0 nm, 9.5 nm, 10.0 nm, and any value within the range formed by any two of these values.

[0014] Furthermore, in the Pt-M / C3N4, the mass ratio of Pt to M is 0.05 to 1.00, preferably 0.10 to 0.25.

[0015] Furthermore, in the Pt-M / C3N4, C3N4 has a multilayer nanosheet structure with a specific surface area of ​​20–500 m². 2 / g.

[0016] Further, the molecular sieve is selected from one or more of ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, Beta, MOR, Y, and MCM-22. Further, the SiO2 / Al2O3 molar ratio in the molecular sieve is 20–150, and the specific surface area is 200–800 m². 2 / g, pore volume is 0.12~0.30cm³ 3 / g.

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0018] Pt-M / C3N4, Pt / Al2O3, and molecular sieves were ball-milled to obtain the alkane hydroisomerization catalyst.

[0019] Furthermore, the preparation method of Pt-M / C3N4 includes: mixing Pt precursor, M precursor, C3N4 and modifier, adding precipitant dropwise, refluxing, and heat-treating in a hydrogen atmosphere to obtain Pt-M / C3N4.

[0020] Further, preferably, the preparation method of Pt-M / C3N4 includes: adding Pt precursor, M precursor and C3N4 to a mixture of alcohol (preferably ethanol), water and modifier for mixing.

[0021] Furthermore, in the preparation method of Pt-M / C3N4, the Pt precursor is one or more of chloroplatinic acid, tetraammineplatinum nitrate, tetraammineplatinum chloride, tetraammineplatinum acetate, or tetraammineplatinum sulfate, preferably tetraammineplatinum nitrate.

[0022] Furthermore, in the preparation method of Pt-M / C3N4, the M precursor is one or more of the nitrate, acetate and chloride salts of M.

[0023] Furthermore, in the preparation method of Pt-M / C3N4, the precipitant is one or more of ammonium carbonate, ammonium bicarbonate, and ammonia water, preferably ammonium carbonate or ammonium bicarbonate.

[0024] Furthermore, in the preparation method of Pt-M / C3N4, the modifier is one or more of lysine, glutamic acid, threonine, and phenylalanine, preferably lysine or glutamic acid.

[0025] Further, in the preparation method of Pt-M / C3N4, the mass ratio of Pt precursor (based on Pt), M precursor (based on M), C3N4, precipitant, modifier, ethanol, and water is Pt:M:C3N4:precipitant:modifier:ethanol:H2O = 0.01~0.5:0.05~1.00:50~100:0.15~0.65:0.15~0.40:200~1000:100~1000, preferably 0.05~0.5:0.2~1.00:50~100:0.15~0.3:0.15~0.20:200~1000:100~1000.

[0026] Furthermore, in the preparation method of Pt-M / C3N4, the reflux temperature is 50-200℃, preferably 50-100℃, and the reflux time is 0.5h-24h, preferably 4h-12h.

[0027] Furthermore, in the preparation method of Pt-M / C3N4, the hydrogen volume content in the hydrogen-containing atmosphere is 5% to 100%, and the inert gas used in the hydrogen-containing atmosphere is a balance gas, which is one or more of N2, Ar, and He.

[0028] Furthermore, in the preparation method of Pt-M / C3N4, the heat treatment temperature is 350-500℃, preferably 450-500℃, and the heat treatment time is 0.5h-24h, preferably 4h-12h.

[0029] Furthermore, in the preparation method of Pt-M / C3N4, after reflux, the material is first centrifuged, dried, and then heat-treated in a hydrogen atmosphere to obtain Pt-M / C3N4. The centrifugation and drying are performed using conventional methods in the art.

[0030] Further, preferably, the preparation method of Pt / Al2O3 includes: adding a Pt precursor solution dropwise to an aqueous suspension of alumina, mixing, drying, and heat treatment to obtain Pt / Al2O3;

[0031] Furthermore, the aqueous suspension of alumina is prepared by mixing alumina and water;

[0032] Furthermore, mixing is preferably carried out under stirring for 0.5 h to 12 h;

[0033] Furthermore, the preferred Pt precursor is chloroplatinic acid, and the Pt concentration in the Pt precursor solution is 0.001 mg. Pt / mL~2.50mg Pt / mL, preferably 0.1mg Pt / mL~1.5mg Pt / mL;

[0034] Furthermore, conventional operations such as filtration and washing are performed before drying. The drying temperature is 40–120°C; the drying time is 0.5 h–24 h. The heat treatment temperature is 350–600°C, preferably 450–500°C; the heat treatment time is 0.5 h–24 h, preferably 4 h–12 h.

[0035] Furthermore, in the preparation method of the catalyst, the ball milling is carried out using a planetary ball mill, the ball milling speed is 300-800 r / min, preferably 500-800 r / min, and the ball milling time is 20 min-12 h, preferably 30 min-2 h.

[0036] A third aspect of the invention also provides the application of the above-described catalyst in the catalytic isomerization reaction of alkane.

[0037] Furthermore, the alkane is at least one of the n-alkanes having 4 to 8 carbon atoms; preferably at least one of n-pentane, n-hexane, n-heptane, and n-octane.

[0038] Further, the reaction conditions are as follows: temperature 200–405 °C, pressure 1.0–4.0 MPa, molar ratio of hydrogen to alkane 0.5–10.0, and alkane mass hourly space velocity (HHSV) 1.0–8.0 h⁻¹. 1 .

[0039] Compared with the prior art, the present invention has the following superior effects:

[0040] This invention provides a novel alkane hydroisomerization catalyst comprising Pt / Al₂O₃, Pt-M / C₃N₄, and a molecular sieve, where M is a metal promoter. In Pt / Al₂O₃, Pt exists in nanoclusters, while in Pt-M / C₃N₄, Pt exists as single atoms. The components in this catalyst work synergistically to significantly improve the utilization efficiency of Pt metal at the optimal yield and reduce the reaction temperature required to achieve the optimal yield.

[0041] In particular, the catalyst of this invention possesses two types of metal active centers with different geometric and electronic properties: Pt single atoms and Pt nanoclusters. By controlling the ratio and properties of the two, the synergistic catalytic effect of Pt single atoms and Pt nanoclusters can be enhanced. At the same time, it can achieve high activation of CH bonds and rapid hydrogenation of olefin intermediates, significantly improve the utilization efficiency of Pt metal when obtaining the best structure yield, reduce the loading of precious metal Pt, and save operating costs.

[0042] The catalyst of this invention is used in the hydroisomerization reaction of low-carbon alkanes to achieve the optimal yield of isomers (Y). max The required reaction temperature (T) at 78.6% max It can be reduced to 240℃. Detailed Implementation

[0043] To more clearly illustrate the technical solution of the present invention, the following specific embodiments are listed. However, those skilled in the art will readily understand that the description of the embodiments is for illustrative purposes only and should not, and will not, limit the invention as described in detail in the claims.

[0044] In this invention, a high-angle annular dark-field scanning transmission electron microscope was used to observe the center of Pt, and the particle size of Pt grains and M nanoparticles in Pt-M / C3N4 were statistically analyzed. The instrument model was FEI Titan Cubed Themis G2300kV.

[0045] In the embodiments and comparative examples of this invention, the C3N4 used is a multilayer nanosheet structure with a specific surface area (S). BET ) = 500m 2 / g.

[0046] The relevant parameters of the ZSM-5 molecular sieve powder used in the embodiments and comparative examples of this invention are as follows: SiO2 / Al2O3 = 25 (molar ratio), specific surface area (S) BET ) = 425m 2 / g, pore volume = 0.12cm 3 / g.

[0047] The relevant parameters of the ZSM-22 molecular sieve powder used in the embodiments and comparative examples of this invention are as follows: SiO2 / Al2O3 = 40 (molar ratio), specific surface area (S) BET ) = 500m 2 / g, pore volume = 0.21cm 3 / g.

[0048] In this invention, the reaction products were analyzed using an Agilent 7890B gas chromatograph.

[0049] In this invention, the formulas for calculating conversion rate and isomer selectivity are as follows:

[0050] Conversion rate (%) = 1 - (mass of n-alkanes in the reaction product / mass of n-alkanes in the feed) × 100%;

[0051] Isomer selectivity (%) = (mass of isoalkanes in the product / total mass of the product) × 100%.

[0052] Yield (%) = Conversion rate × Isomer selectivity × 100%.

[0053] To facilitate understanding of the present invention, the following embodiments are provided. However, these embodiments are merely for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0054] Comparative Example 1

[0055] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 4 hours to obtain Pt / Al2O3-D1.

[0056] (2) Pt / Al2O3-D1 and ZSM-5 molecular sieve were ball-milled at a speed of 500 r / min for 2 h to obtain catalyst D1. The total Pt content, Pt / Al2O3-D1 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1.

[0057] Comparative Example 2

[0058] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 4 hours to obtain Pt / Al2O3-D2.

[0059] (2) Add chloroplatinic acid and C3N4 to a mixture of ethanol, water and lysine, and slowly add ammonium bicarbonate solution under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), C3N4, ammonium bicarbonate, lysine, ethanol and water is Pt:C3N4:ammonium bicarbonate:lysine:ethanol:H2O = 0.1:100:0.3:0.2:1000:1000;

[0060] (3) The mixture obtained in step (2) was refluxed at 100°C for 4 hours, centrifuged and dried, and then treated in 95% H2 / 5% He at 500°C for 6 hours to obtain Pt / C3N4-D2; wherein Pt exists in the form of nanoclusters and the particle size of Pt crystals is 1.0-2.5 nm.

[0061] (4) Pt / Al2O3-D2, Pt / C3N4-D2 and ZSM-5 molecular sieve were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst D2. The total Pt content, Pt / Al2O3-D2 content, Pt / C3N4-D2 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-D2 to Pt content in Pt / C3N4-D2 is shown in Table 2.

[0062] Comparative Example 3

[0063] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 4 hours to obtain Pt / Al2O3-D3.

[0064] (2) Add chloroplatinic acid, zinc nitrate, and C3N4 to a mixture of ethanol and water, and slowly add ammonium bicarbonate solution while stirring. The mass ratio of chloroplatinic acid (calculated as Pt), zinc nitrate (calculated as Zn), C3N4, ammonium bicarbonate, ethanol, and water is Pt:Zn:C3N4:ammonium bicarbonate:ethanol:H2O = 0.1:0.5:100:0.3:1000:1000;

[0065] (3) The mixture obtained in step (2) was refluxed at 100°C for 4 hours, centrifuged and dried, and then treated in 95% H2 / 5% He at 500°C for 6 hours to obtain Pt-Zn / C3N4-D3;

[0066] (4) Pt / Al2O3-D3, Pt / C3N4-D3 and ZSM-5 molecular sieve were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst D3. The total Pt content, Pt / Al2O3-D3 content, Pt-Zn / C3N4-D3 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-D3 to Pt-Zn / C3N4-D3 is shown in Table 2.

[0067]

Example 1

[0068] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 4 hours to obtain Pt / Al2O3-S1.

[0069] (2) Add chloroplatinic acid, zinc nitrate, and C3N4 to a mixture of ethanol, water, and lysine, and slowly add ammonium bicarbonate solution under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), zinc nitrate (calculated as Zn), C3N4, ammonium bicarbonate, lysine, ethanol, and water is Pt:Zn:C3N4:ammonium bicarbonate:lysine:ethanol:H2O = 0.1:0.5:100:0.3:0.2:1000:1000;

[0070] (3) The mixture obtained in step (2) was refluxed at 100°C for 4 hours, centrifuged and dried, and then treated in 95% H2 / 5% He at 500°C for 6 hours to obtain Pt-Zn / C3N4-S1.

[0071] (4) Pt / Al2O3-S1, Pt-Zn / C3N4-S1 and ZSM-5 molecular sieve were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst S1. The total Pt content, Pt / Al2O3-S1 content, Pt-Zn / C3N4-S1 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S1 to Pt-Zn / C3N4-S1 is shown in Table 2.

[0072]

Example 2

[0073] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 6 hours to obtain Pt / Al2O3-S2.

[0074] (2) Add chloroplatinic acid, cerium nitrate, and C3N4 to a mixture of ethanol, water, and lysine, and slowly add ammonium bicarbonate solution under stirring. The mass ratio of chloroplatinic acid (Pt), cerium nitrate (Ce), C3N4, ammonium bicarbonate, lysine, ethanol, and water is Pt:Ce:C3N4:ammonium bicarbonate:lysine:ethanol:H2O = 0.1:1.0:100:0.65:0.4:1000:1000;

[0075] (3) The mixture obtained in step (2) was refluxed at 100°C for 4 hours, centrifuged and dried, and then treated in 95% H2 / 5% He at 500°C for 6 hours to obtain Pt-Ce / C3N4-S2.

[0076] (4) Pt / Al2O3-S2, Pt-Ce / C3N4-S2 and ZSM-5 molecular sieve were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst S2. The total Pt content, Pt / Al2O3-S2 content, Pt-Ce / C3N4-S2 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S2 to Pt-Ce / C3N4-S2 is shown in Table 2.

[0077]

Example 3

[0078] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 550 °C for 10 hours to obtain Pt / Al2O3-S3.

[0079] (2) Add chloroplatinic acid, zinc nitrate, and C3N4 to a mixture of ethanol, water, and glutamic acid, and slowly add ammonium bicarbonate solution under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), cerium nitrate (calculated as Zn), C3N4, ammonium bicarbonate, lysine, ethanol, and water is Pt:Zn:C3N4:ammonium bicarbonate:glutamic acid:ethanol:H2O = 0.1:1.0:100:0.3:0.15:500:1000;

[0080] (3) The mixture obtained in step (2) was refluxed at 100°C for 4 hours, centrifuged and dried, and then treated in 60% H2 / 40% Ar at 500°C for 6 hours to obtain Pt-Zn / C3N4-S3.

[0081] (4) Pt / Al2O3-S3, Pt-Zn / C3N4-S3 and ZSM-22 molecular sieve were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst S3. The total Pt content, Pt / Al2O3-S3 content, Pt-Zn / C3N4-S3 content and ZSM-22 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S3 to Pt content in Pt-Zn / C3N4-S3 is shown in Table 2.

[0082]

Example 4

[0083] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 550 °C for 10 hours to obtain Pt / Al2O3-S4.

[0084] (2) Add chloroplatinic acid, zinc nitrate, and C3N4 to a mixture of ethanol, water, and lysine, and slowly add ammonia solution dropwise under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), cerium nitrate (calculated as Zn), C3N4, ammonia, lysine, ethanol, and water is Pt:Zn:C3N4:ammonia:lysine:ethanol:H2O = 0.01:0.2:100:0.3:0.15:800:1000.

[0085] (3) The mixture in step (2) was refluxed at 200°C for 0.5 h, centrifuged and dried, and then treated in 30% H2 / 70% Ar at 500°C for 6 h to obtain Pt-Zn / C3N4-S4;

[0086] (4) Pt / Al2O3-S4, Pt-Zn / C3N4-S4 and ZSM-5 molecular sieves were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst S4. The total Pt content, Pt / Al2O3-S4 content, Pt-Zn / C3N4-S4 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S4 to Pt-Zn / C3N4-S4 is shown in Table 2.

[0087]

Example 5

[0088] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. PA solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 600 °C for 10 hours to obtain Pt / Al2O3-S5.

[0089] (2) Add chloroplatinic acid, zinc nitrate, and C3N4 to a mixture of ethanol, water, and lysine, and slowly add ammonia solution dropwise under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), cerium nitrate (calculated as Zn), C3N4, ammonia, lysine, ethanol, and water is Pt:Zn:C3N4:ammonia:lysine:ethanol:H2O = 0.05:0.2:100:0.3:0.15:800:1000.

[0090] (3) The mixture obtained in step (2) was refluxed at 50°C for 12 h, centrifuged and dried, and then treated in pure H2 at 450°C for 6 h to obtain Pt-Zn / C3N4-S5.

[0091] (4) Pt / Al2O3-S5, Pt-Zn / C3N4-S5 and ZSM-5 molecular sieves were ball-milled and mixed at a speed of 800 r / min for 30 min to obtain catalyst S5. The total Pt content, Pt / Al2O3-S5 content, Pt-Zn / C3N4-S5 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S5 to Pt content in Pt-Zn / C3N4-S5 is shown in Table 2.

[0092]

Example 6

[0093] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 4 hours to obtain Pt / Al2O3-S6.

[0094] (2) Add chloroplatinic acid, copper nitrate, and C3N4 to a mixture of ethanol, water, and lysine, and slowly add ammonium bicarbonate solution under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), copper nitrate (calculated as Cu), C3N4, ammonium bicarbonate, lysine, ethanol, and water is Pt:Cu:C3N4:ammonium bicarbonate:lysine:ethanol:H2O = 0.1:0.5:100:0.3:0.2:1000:1000;

[0095] (3) The mixture obtained in step (2) was refluxed at 100℃ for 4h, centrifuged and dried, and then treated in 95% H2 / 5% He at 500℃ for 6h to obtain Pt-Cu / C3N4-S6.

[0096] (4) Pt / Al2O3-S6, Pt-Cu / C3N4-S6 and ZSM-5 molecular sieve were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst S6. The total Pt content, Pt / Al2O3-S6 content, Pt-Cu / C3N4-S6 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S6 to Pt-Cu / C3N4-S6 is shown in Table 2.

[0097]

Example 7

[0098] (1) Add 2g of Al2O3 carrier to 100g of deionized water and stir for 1.0h. During the stirring process, add 8mL of 0.5mg of [agent name missing] dropwise. P A solution of H2PtCl6·6H2O with a concentration of t / mL was stirred for 3 hours, filtered, and washed with 1.5 L of deionized water. The resulting filter cake was dried in an oven at 100 °C for 12 hours, and then air-treated at 500 °C for 4 hours to obtain Pt / Al2O3-S7.

[0099] (2) Add chloroplatinic acid, cobalt nitrate, and C3N4 to a mixture of ethanol, water, and lysine, and slowly add ammonium bicarbonate solution under stirring. The mass ratio of chloroplatinic acid (calculated as Pt), cobalt nitrate (calculated as Co), C3N4, ammonium bicarbonate, lysine, ethanol, and water is Pt:Co:C3N4:ammonium bicarbonate:lysine:ethanol:H2O = 0.1:0.5:100:0.3:0.2:1000:1000;

[0100] (3) The mixture obtained in step (2) was refluxed at 100°C for 4 hours, centrifuged and dried, and then treated in 95% H2 / 5% He at 500°C for 6 hours to obtain Pt-Co / C3N4-S7.

[0101] (4) Pt / Al2O3-S7, Pt-Co / C3N4-S7 and ZSM-5 molecular sieves were ball-milled and mixed at a speed of 500 r / min for 2 h to obtain catalyst S7. The total Pt content, Pt / Al2O3-S7 content, Pt-Co / C3N4-S7 content and ZSM-5 molecular sieve content in the catalyst by mass are shown in Table 1. The ratio of Pt content in Pt / Al2O3-S7 to Pt-Co / C3N4-S7 is shown in Table 2.

[0102]

Example 8

[0103] The catalysts prepared in Examples 1-7 and Comparative Examples 1-3 were pressed into tablets, sieved through a 20-40 mesh, and 0.3 g of each catalyst was placed in a fixed-bed reactor. Under a hydrogen atmosphere, the temperature was increased from room temperature to 450°C at a rate of 10°C / min. After reduction for 2 h, the temperature was lowered to the reaction temperature for catalyst evaluation. The catalyst evaluation conditions were as follows: temperature 200-450°C, pressure 1.0 MPa, hydrogen to hexane molar ratio 6.0, and hexane mass hourly space velocity (WHSV) 4.5 h⁻¹. -1 The evaluation results are shown in Table 3.

[0104] Table 1. Composition of the catalysts obtained in each example.

[0105]

[0106]

[0107] Table 2 shows the physicochemical properties of the catalysts obtained in each example.

[0108] Catalyst number X Y <![CDATA[S Pt (nm)]]> <![CDATA[S M (nm)]]> D1 -- -- 0.75 -- D2 1.0 -- 0.75 -- D3 1.0 0.20 0.75 12.6 S1 1.0 0.20 0.75 1.5 S2 0.2 0.10 1.00 1.8 S3 1.6 0.10 1.25 2.5 S4 18.0 0.05 1.50 2.6 S5 10.0 0.25 0.50 4.5 S6 1.0 0.20 0.75 4.0 S7 1.0 0.20 0.75 4.6

[0109] Note: X represents the mass ratio of Pt in Pt / Al2O3 to Pt in Pt-M / C3N4;

[0110] Y represents the mass ratio of Pt to M in Pt-M / C3N4;

[0111] S Pt The average grain size of Pt representing Pt / Al2O3;

[0112] S M The average particle size of M nanoparticles representing Pt-M / C3N4.

[0113] Table 3 shows the optimal catalyst yield (Y) for each example. max ) and the temperature required to achieve the optimal yield (T) max )

[0114] Catalyst number <![CDATA[Y max (%)]]> <![CDATA[T max (℃)]]> D1 47.5 305 D2 59.0 295 D3 60.0 295 S1 78.6 240 S2 70.1 265 S3 75.1 240 S4 70.1 255 S5 75.8 265 S6 74.6 250 S7 73.8 250

[0115] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for alkane hydroisomerization, characterized in that, The catalyst includes Pt / Al2O3, Pt-M / C3N4 and molecular sieve, where M is a metal additive. In Pt / Al2O3, Pt exists in the form of nanoclusters, and in Pt-M / C3N4, Pt exists in the form of single atoms.

2. The catalyst according to claim 1, characterized in that, In the Pt-M / C3N4, M is one or more of Cu, Zn, Mo, Co, W, Ce, Ir, and Re; And / or, the molecular sieve is selected from one or more of ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, Beta, MOR, Y, and MCM-22; preferably, the molecular sieve has a SiO2 / Al2O3 molar ratio of 20 to 150 and a specific surface area of ​​200 to 800 m². 2 / g, pore volume is 0.12~0.30cm³ 3 / g; And / or, in the Pt-M / C3N4, C3N4 has a multilayer nanosheet structure with a specific surface area of ​​20–500 m². 2 / g.

3. The catalyst according to claim 1, characterized in that, In the catalyst, based on catalyst mass, the content of Pt / Al2O3 is 5.0wt% to 50.0wt%; the content of Pt-M / C3N4 is 5.0wt% to 50.0wt%; the content of molecular sieve is 20.0wt% to 60.0wt%; the total Pt content is 0.01wt% to 0.1wt%, preferably 0.01wt% to 0.05wt%, wherein the mass ratio of Pt in Pt / Al2O3 to Pt in Pt-M / C3N4 is 0.2 to 20.0, preferably 1.0 to 10.

0.

4. The catalyst according to claim 1, characterized in that, In the Pt / Al2O3, the average grain size of Pt crystals is 0.50 nm to 1.50 nm.

5. The catalyst according to claim 1, characterized in that, In the Pt-M / C3N4, the average particle size of the M nanoparticles is 1.5 nm to 10.0 nm.

6. The catalyst according to claim 1 or 3, characterized in that, In the Pt-M / C3N4, the mass ratio of Pt to M is 0.05 to 1.00, preferably 0.10 to 0.

25.

7. A method for preparing the catalyst according to any one of claims 1-6, comprising the following steps: Pt-M / C3N4, Pt / Al2O3, and molecular sieves were ball-milled to obtain the alkane hydroisomerization catalyst.

8. The preparation method according to claim 7, characterized in that, The preparation method of Pt-M / C3N4 includes: mixing Pt precursor, M precursor, C3N4 and modifier, adding precipitant dropwise, refluxing, and heat-treating in a hydrogen atmosphere to obtain Pt-M / C3N4; preferably, the Pt precursor, M precursor and C3N4 are added to a mixture of alcohol, water and modifier for mixing.

9. The preparation method according to claim 8, characterized in that, In the preparation method of Pt-M / C3N4, the Pt precursor is one or more of chloroplatinic acid, tetraammineplatinum nitrate, tetraammineplatinum chloride, tetraammineplatinum acetate or tetraammineplatinum sulfate, preferably tetraammineplatinum nitrate. And / or, the M precursor is one or more of the nitrate, acetate and chloride salts of M; And / or, the modifier is one or more of lysine, glutamic acid, threonine, and phenylalanine, preferably lysine or glutamic acid; And / or, the precipitant is one or more of ammonium carbonate, ammonium bicarbonate, and ammonia water, preferably ammonium carbonate or ammonium bicarbonate.

10. The preparation method according to claim 8, characterized in that, In the preparation method of Pt-M / C3N4, the mass ratio of Pt precursor (based on Pt), M precursor (based on M), C3N4, precipitant, modifier, ethanol, and water is Pt:M:C3N4:precipitant:modifier:ethanol:H2O = 0.01~0.5:0.05~1.00:50~100:0.15~0.65:0.15~0.40:200~1000:100~1000, preferably 0.05~0.5:0.2~1.00:50~100:0.15~0.3:0.15~0.20:200~1000:100~1000.

11. The preparation method according to claim 8, characterized in that, In the preparation method of Pt-M / C3N4, the reflux temperature is 50-200℃, preferably 50-100℃; the reflux time is 0.5h-24h, preferably 4h-12h. And / or, in the preparation method of Pt-M / C3N4, the heat treatment temperature is 350-500℃, preferably 450-500℃, and the heat treatment time is 0.5h-24h, preferably 4h-12h; And / or, in the preparation method of Pt-M / C3N4, the hydrogen volume content in the hydrogen-containing atmosphere is 5% to 100%, and the inert gas used in the hydrogen-containing atmosphere is a balance gas, which is one or more of N2, Ar, and He.

12. The preparation method according to claim 7, characterized in that, The ball milling is carried out using a planetary ball mill, with a ball milling speed of 300-800 r / min, preferably 500-800 r / min; and a ball milling time of 20 min-12 h, preferably 30 min-2 h.

13. The use of any catalyst according to claims 1-6 or any catalyst prepared by any method according to claims 7-12 in the catalytic alkane isomerization reaction.

14. The application according to claim 13, characterized in that, The alkane is at least one of the n-alkanes having 4 to 8 carbon atoms; preferably at least one of n-pentane, n-hexane, n-heptane, and n-octane.

15. The application according to claim 13, characterized in that, The reaction conditions were as follows: temperature 200–405℃, pressure 1.0–4.0 MPa, molar ratio of hydrogen to alkanes 0.5–10.0, and mass hourly space velocity (HHSV) of the alkane 1.0–8.0 h⁻¹. -1 .

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