Application of PtZn / s-S-1 catalyst in non-hydrogen dehydrogenation of propane

Abstract

The invention relates to an application of a PtZn bimetallic catalyst loaded on a flaky S-1 molecular sieve in a non-hydrogen dehydrogenation reaction of propane. The preparation method of the catalyst comprises the following steps: firstly, obtaining a flaky S-1 carrier by utilizing a hydrothermal method, and then loading Pt and Zn onto the carrier by utilizing an impregnation method. In the high-temperature H2 reduction process, the interaction between Pt and the carrier is weak, so that a Pt1Zn1 intermetallic compound is formed. The PtZn bimetallic catalyst loaded on the sheet-shaped S-1 molecular sieve is excellent in stability and good in regeneration performance under the condition of propane non-hydrogen dehydrogenation reaction. The PtZn / s-S-1 catalyst is simple in preparation process, excellent in catalytic performance, high in propylene selectivity and high in catalytic stability, and has wide application value in the aspect of improving the catalytic stability and regeneration stability.

Description

Technical Field

[0001] The present invention belongs to the field of industrial applications, and relates to the preparation of a catalyst and the study of its performance in propane non-hydrogen dehydrogenation. Specifically, it relates to the application research of the PtZn / s-S-1 catalyst in propane non-hydrogen dehydrogenation reaction. Background Art

[0002] Propylene is the second largest petrochemical product after ethylene and is widely used in the preparation of acrolein, acetone, polypropylene, polyacrylonitrile, propylene oxide and other chemical products. For a long time, propylene has mainly been sourced from catalytic cracking and steam cracking of petroleum. With the expansion and development of the global chemical industry, the demand for these downstream products in the chemical industry has increased significantly, thus continuously raising the production capacity requirements for its main upstream product, propylene. In recent years, the development and utilization of shale gas have made propane an important economic raw material for the industrial production of propylene. Among them, the propane direct dehydrogenation process provides 11-13% of the global propylene supply every year, and has received increasing attention and research due to its characteristics of producing only propylene, high selectivity and raw material economy.

[0003] In the propane dehydrogenation reaction, when propane is introduced as a single feed gas, it is prone to cracking and carbon deposition. Industrially, in order to inhibit the carbon deposition deactivation of noble metal Pt-based catalysts and improve catalytic stability, hydrogen is introduced into the reactor simultaneously with propane. However, although the introduction of hydrogen will increase the dehydrogenation activity of the Pt-based catalyst and inhibit the generation of carbon deposition, thermodynamically speaking, the introduction of hydrogen will inhibit the propane dehydrogenation reaction and reduce the propane equilibrium conversion rate. Therefore, achieving a propane non-hydrogen dehydrogenation reaction with high activity, high selectivity and high stability helps to break the thermodynamic equilibrium limitation under hydrogenation conditions, improve the propane single-pass conversion rate, and thus increase economic benefits, but it also poses certain challenges. Currently, most of the research on the propane dehydrogenation reaction focuses on the hydrogenation conditions, while relatively less attention has been paid to the direct dehydrogenation of propane under non-hydrogen conditions.

[0004] In PtZn bimetallic catalysts, molecular sieves have been developed as supports for propane dehydrogenation catalysts due to their adjustable acid-base properties and selectable pore structures, such as S-1, TS-1, beta, ZSM-5, MCM, SBA-15, etc. Molecular sieves also exhibit a unique effect of promoting Pt dispersion due to their confinement effect on metal components and weak interactions. S-1 molecular sieve is a pure silica MFI-type molecular sieve with a pore size of just slightly larger than the propane molecular size (about ) Therefore, many researchers have prepared PtZn@S-1 encapsulated catalysts by the hydrothermal one-pot method. The PtZn bimetal is encapsulated in the pores by the confinement effect of S-1 zeolite, thereby inhibiting its aggregation and sintering during the reaction process and regeneration process. Zhang et al. reported a PtZn bimetal catalyst encapsulated in S-1 zeolite. The single-site Zn in the MFI framework and the confinement effect work together to enhance the catalytic stability and thermal stability of the catalyst. Zhang et al., Wang et al., and Sun et al. all encapsulated PtZn bimetal nanoparticles in S-1 zeolite by the hydrothermal one-pot method. Compared with simple supported catalysts, the encapsulated catalysts showed excellent catalytic stability. However, this method causes the loss of precious metal Pt during the preparation process, and the Pt loading is generally high. Therefore, preparing a PtZn / S-1 catalyst with excellent stability by a simple impregnation method can simplify the preparation process and avoid the loss of precious metals, which has important practical application significance. Summary of the Invention

[0005] The object of the present invention is to provide a PtZn / s-S-1 catalyst for propane non-hydrogen dehydrogenation reaction in view of the above-mentioned prior art situation. This catalyst has characteristics such as high selectivity and high stability for propane non-hydrogen dehydrogenation reaction.

[0006] To achieve the above object, in the present invention, a flaky S-1 support is prepared by the hydrothermal method, and then impregnated with a precursor solution of Pt and a precursor solution of Zn to obtain a PtZn / s-S-1 catalyst. After the catalyst is reduced, a strong interaction occurs between Pt and Zn, forming a Pt1Zn1 intermetallic compound. A PtZn / s-S-1 catalyst with excellent stability is prepared by a simple impregnation method, avoiding the loss of precious metals.

[0007] The preparation method of the PtZn / s-S-1 catalyst described in the present invention is as follows: Weigh 10-50 g of TPAOH (mass percentage is 40%) and 20-100 g of ultrapure water, mix and stir for 20-40 min, add 10-50 g of TEOS and 3-10 g of urea, and continue to stir for 6-18 h. Transfer to a hydrothermal autoclave and carry out hydrothermal reaction at 160-200 °C for 1-3 days, then filter and wash with water until neutral, dry at 60-120 °C for 12-30 h, grind and calcine at 500-600 °C for 2-5 h; Immerse the metal precursor solution containing Pt and the metal precursor solution containing Zn onto the support, and then dry at 60-120 °C for 6-30 h and calcine at 500-600 °C for 2-5 h; The Pt precursor solution is an aqueous solution of H2PtCl6·6H2O, and the Zn precursor solution is an aqueous solution of Zn(NO3)2·6H2O. The drying condition is to dry at 60-120 °C for 6-30 h, and the calcination condition is to calcine at 500-600 °C for 2-5 h.

[0008] The PtZn / s-S-1 catalyst prepared by any of the above methods is used in the non-hydrogen dehydrogenation reaction of propane. The characteristic reaction conditions are 500 - 600 °C, the volume ratio of the raw material gas: 3 - 8% C3H8, the balance is He, the gas flow rate is 10 - 100 mL / min, and the WHSV is 1 - 40 h -1 .

[0009] During the high-temperature H2 reduction process, due to the weak interaction between Pt and the support, Pt1Zn1 intermetallic compound is formed. The PtZn bimetallic catalyst supported on the flaky S-1 zeolite in the present invention has excellent stability and good regeneration performance under the conditions of propane non-hydrogen dehydrogenation reaction. This PtZn / s-S-1 catalyst preparation process is simple, with excellent catalytic performance, high propylene selectivity, and strong catalytic stability, and has wide application value in improving catalytic stability and regeneration stability.

[0010] The present invention has the following advantages compared with the prior art:

[0011] 1. In the present invention, the PtZn / s-S-1 catalyst with excellent stability can be obtained by simple impregnation method, which simplifies the preparation process and effectively avoids the loss of precious metals. Due to the application of the flaky S-1 zeolite, the catalyst shows high conversion rate in the non-hydrogen dehydrogenation reaction of propane, approaching the equilibrium conversion rate.

[0012] 2. The PtZn / s-S-1 catalyst prepared in the present invention forms Pt1Zn1 intermetallic compound after reduction. Due to the formation of Pt1Zn1 intermetallic compound, the catalyst has excellent propylene selectivity, reaction stability and regeneration stability: the catalyst has a propylene selectivity of more than 99% at 550 °C, has strong stability within 120 hours of continuous reaction, and the catalyst shows no obvious deactivation after 3 cycles of regeneration tests.

[0013] The present invention will be described in detail below through specific examples. It should be noted that these examples are only for illustration and do not constitute any limitation to the essence and scope of the present invention. The present invention can be realized as long as the conditions described in the content part of the present invention are met. Therefore, the protection scope of the present invention is subject to the claims of the application. Description of the Drawings

[0014] Figure 1 For the performance evaluation of the catalysts in Comparative Example 4, Examples 5, 6, 7, 8 and the relationship between Zn loading and the initial conversion rate of propane and the initial selectivity of propylene.

[0015] Figure 2 For the stability evaluation of the catalysts in Examples 9 and 10.

[0016] Figure 3 It is for the regeneration stability evaluation of the catalysts in Examples 11 and 12.

[0017] Figure 4 It is the XRD patterns of the reduced catalysts in Comparative Example 1, Example 1, and Example 3.

[0018] Figure 5 It is the HAADF-STEM images, EDS mapping, particle size distribution statistics of metal particles below 10 nm, and HRTEM images of the reduced catalysts in Example 1 and Example 3.

[0019] Figure 6 It is the transmission electron microscope images of the reduced catalysts in Example 1 and Example 3.

[0020] Figure 7 It is the NH3-TPD spectra and NH3 desorption amounts of the catalysts in Example 1, Example 3, and Comparative Example 2.

[0021] Figure 8 It is the C3H6-TPD spectra of the catalysts in Example 1, Example 3, and Comparative Example 2. Detailed implementation mode

[0022] Example 1.

[0023] Preparation of 0.5Pt2.5Zn / s-S-1 catalyst:

[0024] Weigh 25 g of TPAOH (mass percentage is 40%) and 66 g of ultrapure water, mix and stir for 30 min, add 28 g of TEOS and 6.5 g of urea, and continue to stir for 12 h. Transfer to a 200 mL autoclave, carry out hydrothermal reaction at 180 °C for 2 days, filter, wash with water until neutral, dry at 120 °C for 24 h, grind, and then calcine at 500 °C for 4 h to obtain the s-S-1 support. The lamellar thickness is 50 - 150 nm, and the area is 300 - 350 m 2 ·g -1 . Weigh 1 g of the s-S-1 support in a 25 mL beaker, transfer 169 μL of an aqueous solution of chloroplatinic acid H2PtCl6·6H2O (29.6 mg Pt / mL) and 845 μL of an aqueous solution of Zn(NO3)2·6H2O (29.6 mg Zn / mL) into a centrifuge tube, then add 480 μL of ultrapure water, mix evenly, and dropwise add and impregnate on the support, and stir well. Let the obtained paste solid stand overnight at room temperature, dry at 60 °C for 6 h, grind, and then calcine at 500 °C for 4 h to obtain the 0.5Pt2.5Zn / s-S-1 catalyst (the values before the metal represent their mass percentage on the support, where the mass percentage of Pt is 0.5 wt%, and the mass percentage of Zn is 2.5 wt%).

[0025] Example 2.

[0026] Preparation of 0.5Pt0.5Zn / s-S-1 catalyst:

[0027] Weigh 25 g of TPAOH (mass percentage 40%) and 66 g of ultrapure water, mix and stir for 30 min. Add 28 g of TEOS and 6.5 g of urea, and continue stirring for 12 h. Transfer to a 200 mL autoclave, carry out hydrothermal reaction at 180 °C for 2 days, filter, wash with water until neutral, dry at 120 °C for 24 h, grind, and then calcine at 500 °C for 4 h to obtain the s-S-1 support. Weigh 1 g of the s-S-1 support in a 25 mL beaker, pipette 169 μL of chloroplatinic acid aqueous solution (29.6 mg Pt / mL) and 169 μL of Zn(NO3)2 aqueous solution (29.6 mg Zn / mL) into a centrifuge tube, then add 480 μL of ultrapure water, mix evenly, and impregnate drop by drop on the support in batches, stirring well. Let the obtained paste-like solid stand overnight at room temperature, dry at 60 °C for 6 h, grind, and then calcine at 500 °C for 4 h to obtain the 0.5Pt0.5Zn / s-S-1 catalyst.

[0028] Example 3.

[0029] Preparation of 0.5Pt1Zn / s-S-1 catalyst:

[0030] Weigh 25 g of TPAOH (mass percentage 40%) and 66 g of ultrapure water, mix and stir for 30 min. Add 28 g of TEOS and 6.5 g of urea, and continue stirring for 12 h. Transfer to a 200 mL autoclave, carry out hydrothermal reaction at 180 °C for 2 days, filter, wash with water until neutral, dry at 120 °C for 24 h, grind, and then calcine at 500 °C for 4 h to obtain the s-S-1 support. Weigh 1 g of the s-S-1 support in a 25 mL beaker, pipette 169 μL of chloroplatinic acid aqueous solution (29.6 mg Pt / mL) and 338 μL of Zn(NO3)2 aqueous solution (29.6 mg Zn / mL) into a centrifuge tube, then add 480 μL of ultrapure water, mix evenly, and impregnate drop by drop on the support in batches, stirring well. Let the obtained paste-like solid stand overnight at room temperature, dry at 60 °C for 6 h, grind, and then calcine at 500 °C for 4 h to obtain the 0.5Pt1Zn / s-S-1 catalyst.

[0031] Example 4.

[0032] Preparation of 0.5Pt5Zn / s-S-1 catalyst:

[0033] Weigh 25 g of TPAOH (mass percentage is 40%) and 66 g of ultrapure water, mix and stir for 30 min, add 28 g of TEOS and 6.5 g of urea, and continue stirring for 12 h. Transfer to a 200 mL autoclave, carry out hydrothermal reaction at 180 °C for 2 days, filter, wash with water until neutral, dry at 120 °C for 24 h, grind, and calcine at 500 °C for 4 h to obtain the s-S-1 support. Weigh 1 g of the s-S-1 support in a 25 mL beaker, pipette 169 μL of chloroplatinic acid aqueous solution (29.6 mg Pt / mL) and 1690 μL of Zn(NO3)2 aqueous solution (29.6 mg Zn / mL) into a centrifuge tube, then add 480 μL of ultrapure water, mix evenly, impregnate dropwise on the support in batches, and stir well. Let the obtained paste-like solid stand overnight at room temperature, dry at 60 °C for 6 h, grind, and calcine at 500 °C for 4 h to obtain the 0.5Pt5Zn / s-S-1 catalyst.

[0034] Example 5.

[0035] Activity evaluation of 0.5Pt2.5Zn / s-S-1 catalyst:

[0036] Pretreatment conditions: 600 °C, pure H2, space velocity of 18,000 mL·h -1 ·g -1 , treat for 1 hour.

[0037] Catalytic reaction conditions: Fixed-bed inner diameter 10 mm quartz reaction tube, the volume ratio of the raw material gas composition is 5% C3H8, 95% He, and the space velocity of the raw material gas is 18,000 mL·h -1 ·g -1 . The reaction temperature is 550 °C, the reaction pressure is atmospheric pressure, and the reaction time is 20 h.

[0038] Example 6.

[0039] Activity evaluation of 0.5Pt0.5Zn / s-S-1 catalyst: The conditions are the same as those in Example 5.

[0040] Example 7.

[0041] Activity evaluation of 0.5Pt1Zn / s-S-1 catalyst: The conditions are the same as those in Example 5.

[0042] Example 8.

[0043] Activity evaluation of 0.5Pt5Zn / s-S-1 catalyst: The conditions are the same as those in Example 5.

[0044] Example 9.

[0045] Stability evaluation of 0.5Pt2.5Zn / s-S-1 catalyst:

[0046] Pretreatment conditions: 600 °C, pure H2, space velocity of 18,000 mL·h -1 ·g -1 , treated for 1 hour.

[0047] Catalytic reaction conditions: A quartz reaction tube with an inner diameter of 10 mm in a fixed bed, the volume ratio of the raw material gas composition is 5% C3H8 and 95% He, and the space velocity of the raw material gas is 18,000 mL·h -1 ·g -1 . The reaction temperature is 550 °C, the reaction pressure is atmospheric pressure, and the reaction time is 120 h.

[0048] Example 10.

[0049] Stability evaluation of 0.5Pt1Zn / s-S-1 catalyst: The process and conditions are the same as those in Example 9, and the reaction time is 100 h.

[0050] Example 11.

[0051] Regeneration test of 0.5Pt2.5Zn / s-S-1 catalyst:

[0052] Pretreatment conditions: 600 °C, pure H2, space velocity of 18,000 mL·h -1 ·g -1 , treated for 1 hour.

[0053] Catalytic reaction conditions: A quartz reaction tube with an inner diameter of 10 mm in a fixed bed, the volume ratio of the raw material gas composition is 5% C3H8 and 95% He, and the space velocity of the raw material gas is 18,000 mL·h -1 ·g -1 . The reaction temperature is 550 °C, and the reaction pressure is atmospheric pressure.

[0054] Regeneration conditions: A mixture of 20% O2 and He by volume fraction, space velocity of 18,000 mL·h -1 ·g -1 , treated for 2 hours.

[0055] Then, pretreatment, catalytic reaction (each reaction lasts for 5 h), and regeneration are carried out in sequence, and this process is repeated.

[0056] Example 12.

[0057] Regeneration test of 0.5Pt1Zn / s-S-1 catalyst: The process and conditions are the same as those in Example 11.

[0058] Example 13.

[0059] XRD Characterization of s-S-1, 0.5Pt / s-S-1, 0.5Pt1Zn / s-S-1, and 0.5Pt2.5Zn / s-S-1 Catalysts

[0060] After loading the metal components, the diffraction peaks of the molecular sieve did not change. After loading the metal and calcination treatment, the molecular sieve framework remained intact and was not damaged. In the 0.5Pt / s-S-1 catalyst, a Pt diffraction peak (PDF#04-0802) appeared at 2θ = 39.8°, indicating that Pt aggregated to form larger particles in the single Pt catalyst. In the 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / s-S-1 catalysts, no diffraction peaks of Pt or ZnO or PtZn intermetallic compounds were observed, indicating that the metal components were highly dispersed and no obvious aggregation occurred.

[0061] Example 14.

[0062] XRD Characterization of 0.5Pt / s-S-1 (Comparative Example 1), 0.5Pt1Zn / s-S-1, and 0.5Pt2.5Zn / s-S-1 Catalysts after Reduction (Pretreatment Process of Example 5):

[0063] Diffraction peaks of the Pt1Zn1 intermetallic compound appeared in both the reduced 0.5Pt1Zn and 0.5Pt2.5Zn catalysts, indicating that the Pt1Zn1 intermetallic compound was formed after the reduction of the two catalysts.

[0064] Example 15.

[0065] Physical Adsorption Characterization of 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 Catalysts:

[0066] The N2 adsorption-desorption isotherms of the two catalysts were mainly type-IV curves, indicating that the catalysts mainly had mesoporous structures.

[0067] Example 16.

[0068] HAADF-STEM Characterization of 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 Catalysts after Reduction (Pretreatment Process of Example 5):

[0069] The HAADF-STEM images showed that there were highly uniformly dispersed PtZn sub-nanoparticles in the 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 catalysts. The addition of the Zn promoter could effectively disperse Pt, and the molecular sieve pores had a confinement effect on the PtZn nanoparticles.

[0070] Example 17.

[0071] EDS characterization of 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 after reduction (pretreatment process of Example 5):

[0072] Most of Pt and Zn are dispersed on the surface of the support, and the elemental distributions of Pt and Zn highly overlap, indicating the formation of Pt1Zn1 intermetallic compounds in the catalyst.

[0073] Example 18.

[0074] NH3-TPD characterization of 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / s-S-1 catalysts:

[0075] There are mainly two NH3 desorption peaks on the catalysts: 100 - 250 °C and 250 - 500 °C, which can be attributed to the NH3 desorption peaks on weak acid sites and medium strong acid sites respectively. Among them, the acid amount, especially the medium strong acid amount, of the 0.5Pt1Zn / s-S-1 catalyst is more than that of the 0.5Pt2.5Zn / s-S-1 catalyst.

[0076] Example 19.

[0077] C3H6-TPD characterization of 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / s-S-1 catalysts:

[0078] The order of magnitude of the propylene desorption mass spectrometry signal on each catalyst is around 10 -12 The application of the S-1 support greatly weakens the adsorption intensity and adsorption amount of the catalyst for propylene, which is beneficial to propylene desorption and thus improves the catalytic stability.

[0079] Comparative Example 1.

[0080] Preparation of 0.5Pt / s-S-1 catalyst:

[0081] Weigh 25 g of TPAOH (mass percentage is 40%) and 66 g of ultrapure water, mix and stir for 30 min, add 28 g of TEOS and 6.5 g of urea, and continue to stir for 12 h. Transfer to a 200 mL autoclave, carry out hydrothermal reaction at 180 °C for 2 days, filter, wash with water until neutral, dry at 120 °C for 24 h, grind, and then calcine at 500 °C for 4 h to obtain the s-S-1 support. Weigh 1 g of the s-S-1 support in a 25 mL beaker, transfer 169 μL of chloroplatinic acid aqueous solution (29.6 mg Pt / mL) into a centrifuge tube, add 480 μL of ultrapure water and mix evenly, impregnate dropwise on the support in batches, and stir well. Place the obtained paste solid at room temperature overnight, dry at 60 °C for 6 h, grind, and then calcine at 500 °C for 4 h to obtain the 0.5Pt5Zn / s-S-1 catalyst.

[0082] Comparative Example 2.

[0083] Preparation of 0.5Pt2.5Zn / n-S-1 catalyst:

[0084] Weigh 19.8 g of TPAOH (mass percentage is 40%) and 67.7 g of ultrapure water, mix and stir for 30 min, add 21 g of TEOS and continue stirring for 12 h. Transfer to a 200 mL autoclave, carry out hydrothermal reaction at 180 °C for 2 days, centrifuge, wash with water until neutral, dry at 120 °C for 24 h, grind and then calcine at 500 °C for 4 h to obtain a conventional S-1 support (denoted as n-S-1 support). The n-S-1 support is spherical (particle size range is 15 - 30 μm), with an obvious shape difference from the flaky S-1 support. Weigh 1 g of the n-S-1 support in a 25 mL beaker, transfer 169 μL of chloroplatinic acid aqueous solution (29.6 mg Pt / mL) and 845 μL of Zn(NO3)2 aqueous solution (29.6 mg Zn / mL) into a centrifuge tube, then add 480 μL of ultrapure water and mix evenly. Immerse drop by drop on the support in batches and stir well. Let the obtained paste-like solid stand overnight at room temperature, dry at 60 °C for 6 h, grind and then calcine at 500 °C for 4 h to obtain the 0.5Pt2.5Zn / n-S-1 catalyst.

[0085] Comparative Example 3.

[0086] Preparation of 0.5Pt2.5Zn / c-S-1 catalyst:

[0087] Weigh 1 g of commercial S-1 support (denoted as c-S-1 support, crystal size 5 - 10 μm) in a 25 mL beaker, transfer 169 μL of chloroplatinic acid aqueous solution (29.6 mg Pt / mL) and 845 μL of Zn(NO3)2 aqueous solution (29.6 mg Zn / mL) into a centrifuge tube, then add 480 μL of ultrapure water and mix evenly. Immerse drop by drop on the support in batches and stir well. Let the obtained paste-like solid stand overnight at room temperature, dry at 60 °C for 6 h, grind and then calcine at 500 °C for 4 h to obtain the 0.5Pt2.5Zn / c-S-1 catalyst.

[0088] Comparative Example 4.

[0089] Activity evaluation of 0.5Pt / s-S-1 catalyst:

[0090] Pretreatment conditions: 600 °C, pure H2, space velocity is 18,000 mL·h -1 ·g -1 , treat for 1 hour.

[0091] Catalytic reaction conditions: A quartz reaction tube with an inner diameter of 10 mm in a fixed bed. The volume ratio of the raw material gas composition is 5% C3H8 and 95% He, and the space velocity of the raw material gas is 18,000 mL·h -1 ·g -1 . The reaction temperature is 550 °C, and the reaction pressure is atmospheric pressure.

[0092] Comparative Example 5.

[0093] Activity evaluation of 0.5Pt2.5Zn / n-S-1 catalyst: The conditions are the same as those in Comparative Example 4.

[0094] Comparative Example 6.

[0095] Activity evaluation of 0.5Pt2.5Zn / c-S-1 catalyst: The conditions are the same as those in Comparative Example 4.

[0096] The corresponding conversion rate and selectivity results are shown in the following table:

[0097]

[0098] Deactivation rate constant k d =(ln(((1 - X final ) / X final ) - ln(((1 - X initial ) / X initial )) / t, where X is the propane conversion rate, X initial is the initial conversion rate, X final is the final conversion rate, t is the reaction time (h), and the smaller k d , the better the stability of the catalyst. The reaction temperature and space velocity in the table are both 550 °C and 18,000 mL·h -1 ·g -1 .

[0099] Comparing Comparative Examples 5 and 6 with Example 5, the loadings of Pt and Zn are the same, and there is no obvious difference in the selectivity of the catalyst, indicating that when S-1 molecular sieve is used as the support of the propane dehydrogenation catalyst, it can effectively inhibit the occurrence of side reactions and improve the propylene selectivity. However, in Comparative Examples 5 and 6, the propane conversion rate and its deactivation trend are almost the same. In Example 5, although the activity decreases at the beginning of the reaction, the overall propane conversion rate increases significantly, getting closer to the equilibrium conversion rate, and remains relatively stable within 20 h of reaction time without obvious deactivation, indicating that the flaky S-1 molecular sieve can effectively improve the propane conversion rate when used as the support of the PtZn bimetallic catalyst. Comparing Example 6 with Comparative Example 4, the single Pt catalyst has almost no catalytic effect on propane dehydrogenation or cracking reaction, and the conversion rate is only about 5%. When a small amount of Zn is added, the initial propane conversion rate jumps significantly, but the catalyst stability is poor. Comparing Example 7 with Example 6, the content of Zn increases from 0.5 wt% to 1 wt%, the initial activity of the reaction further increases, and the stability is improved to some extent, but the initial propylene selectivity is relatively low. Comparing Example 5 with Examples 6 and 7, when the Zn loading increases to 2.5 wt%, the initial activity of the reaction decreases slightly, but the catalyst stability is still good, and the initial propylene selectivity also recovers to over 99%. Comparing Example 8 with Example 5, when the Zn loading further increases to 5 wt%, the propane conversion rate drops significantly, and the catalyst deactivates within the first 8 h of reaction time.

[0100] The above results fully demonstrate that excellent conversion rate, selectivity and stability are simultaneously exhibited when the Zn loading is 1 wt% and 2.5 wt%.

[0101] Appendix Figure 1 is the performance evaluation of the 0.5PtxZn / s-S-1 (x = 0, 0.5, 1, 2.5, 5) catalysts and the relationship between the Zn loading and the initial propane conversion rate and the initial propylene selectivity. With the increase of the Zn content, the change of the initial propane conversion rate shows a volcano-shaped curve, while the initial propylene selectivity shows an inverted volcano-shaped curve. Excellent conversion rate, selectivity and stability are simultaneously exhibited when the Zn loading is 1 wt% and 2.5 wt%.

[0102] Appendix Figure 2 is the stability evaluation of the 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / s-S-1 catalysts. Both of them show excellent catalytic stability and propylene selectivity.

[0103] Appendix Figure 3 is the regeneration stability evaluation of the 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / s-S-1 catalysts. Among them, the 0.5Pt2.5Zn / s-S-1 catalyst shows no obvious deactivation after being regenerated three times.

[0104] Appendix Figure 4 XRD patterns of the reduced 0.5Pt / s-S-1, 0.5Pt1Zn / s-S-1, and 0.5Pt2.5Zn / s-S-1 catalysts. In the reduced PtZn / s-S-1 catalyst, characteristic peaks of the Pt1Zn1 intermetallic compound appear. This is because the interaction between Pt and the support is weak, forming the Pt1Zn1 intermetallic compound, which may be one of the reasons for the excellent stability of the catalyst.

[0105] Appendix Figure 5 HAADF-STEM images, EDS mapping, particle size distribution statistics of metal particles below 10 nm, and HRTEM images of the reduced 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 catalysts. In the 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 catalysts, there are both highly uniformly dispersed PtZn sub-nanoparticles and larger particles distributed outside the zeolite pores, with average particle sizes of 0.85 nm and 0.97 nm, respectively, indicating that the addition of Zn promoter can effectively disperse Pt, and the zeolite pores have a confinement effect on PtZn nanoparticles. Most of Pt and Zn are dispersed on the surface of the support, and the elemental distributions of Pt and Zn highly overlap, further confirming the formation of the Pt1Zn1 intermetallic compound in the reduced 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 catalysts.

[0106] Appendix Figure 6 TEM images of the 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / s-S-1 catalysts. By measuring, the thickness of the flaky S-1 zeolite is 50 - 150 nm.

[0107] Appendix Figure 7 NH3-TPD spectra and NH3 desorption amounts of the 0.5Pt2.5Zn / n-S-1, 0.5Pt1Zn / s-S-1, and 0.5Pt2.5Zn / s-S-1 catalysts. The acid amount, especially the medium-strong acid amount, of the 0.5Pt1Zn / s-S-1 catalyst is more than that of the 0.5Pt2.5Zn / s-S-1 catalyst, which may be the reason for the lower initial selectivity and poorer stability of the 0.5Pt1Zn / s-S-1 catalyst for propylene.

[0108] Appendix Figure 8C3H6-TPD spectra of 0.5Pt2.5Zn / n-S-1, 0.5Pt1Zn / s-S-1, and 0.5Pt2.5Zn / s-S-1 catalysts, with mass numbers being a. 42 (propylene); b. 16 (methane). In the 0.5Pt2.5Zn / s-S-1 catalyst, the desorption amount of propylene is significantly more than that of other catalysts. This may be because at low temperatures, both the 0.5Pt1Zn / s-S-1 and 0.5Pt2.5Zn / n-S-1 catalysts catalyze a certain degree of cracking reaction of propylene to produce by-products such as methane, resulting in a decrease in the desorption amount of propylene, while almost no cracking products are formed on the 0.5Pt2.5Zn / s-S-1 catalyst. This may be one of the reasons for the high selectivity of the 0.5Pt2.5Zn / s-S-1 catalyst.

[0109] In summary, in the propane non-hydrogen dehydrogenation reaction, the PtZn / s-S-1 catalysts supported on flaky S-1, namely 0.5Pt2.5Zn / s-S-1 and 0.5Pt1Zn / s-S-1 catalysts, exhibit excellent propane conversion, propylene selectivity, and catalytic stability. The Zn loading affects the acidity of the catalyst. Increasing the Zn loading can effectively reduce the content of medium-strong acids in the catalyst, reduce the occurrence of side reactions, and improve propylene selectivity. This PtZn bimetallic catalyst prepared by a simple impregnation method for highly efficient catalytic propane dehydrogenation has broad application prospects in industry.

Claims

1. Application of PtZn / s-S-1 catalyst in non-hydrogen dehydrogenation of propane, characterized in that: The catalyst is prepared by hydrothermal method to prepare molecular sieve S-1 support (denoted as s-S-1), and after impregnating soluble compounds of Pt and Zn, it is reduced in pure hydrogen at 400 - 700 °C (preferably 550 - 650 °C) for 1 - 5 h.

2. The application according to claim 1, characterized in that: After reduction in pure hydrogen, Pt and Zn in the catalyst interact to form Pt1Zn1 intermetallic compound.

3. The application according to claim 1 or 2, characterized in that: In the catalytic non-hydrogen dehydrogenation reaction of propane, Pt in the catalyst exists in the form of Pt1Zn1 intermetallic compound and is dispersed on the surface of the support.

4. The application according to claim 1 or 3, characterized in that: For Pt and Zn in the catalyst, the mass percentage of Pt on the support is 0.2 - 1 wt%, and the mass ratio of Pt to Zn is 1:1 - 1:10, and the most preferred mass ratio of Pt to Zn is 1:2 - 1:

5.

5. The application according to claim 1, characterized in that: The preparation process of the catalyst is as follows: Weigh 10 - 50 g (preferably 20 - 30 g) of TPAOH (tetrapropylammonium hydroxide with a mass percentage of 40%) and 20 - 100 g of water, mix and stir for 20 - 40 min, add 10 - 50 g (preferably 20 - 35 g) of TEOS (tetraethyl orthosilicate) and 3 - 10 g (preferably 5 - 7 g) of urea, and continue to stir for 6 - 18 h; transfer to a hydrothermal autoclave and carry out hydrothermal reaction at 160 - 200 °C for 1 - 3 days, then filter and wash with water until neutral, dry at 60 - 120 °C for 12 - 30 h, grind and calcine at 400 - 600 °C (preferably 450 - 550 °C) for 2 - 5 h (preferably 3.5 - 4.5 h) to obtain a flaky S-1 support; impregnate the support with a metal precursor solution containing Pt and / or a metal precursor solution containing Zn, then dry at 60 - 120 °C for 6 - 30 h and calcine at 400 - 600 °C (preferably 450 - 550 °C) for 2 - 5 h (preferably 3.5 - 4.5 h); the Pt precursor solution is an aqueous solution of H2PtCl6, and the Zn precursor solution is an aqueous solution of Zn(NO3)2.

6. Application of the catalyst according to any one of claims 1 - 5 in the non-hydrogen dehydrogenation reaction of propane.

7. The application according to claim 6, characterized in that: The reaction conditions are 400 - 600 °C, preferably 500 - 600 °C. The volume ratio of the raw material gases is: 3 - 8% (preferably 4 - 6%) C3H8, with the balance being He, and the space velocity is 8,000 - 20,000 mL·h -1 ·g -1 (preferably 16,000 - 19,000 mL·h -1 ·g -1 ).

8. The application according to claim 7, characterized in that: The catalyst dosage is 20 - 200 mg, and the gas flow rate is 10 - 100 mL / min; The most preferred catalyst exhibits excellent continuous catalytic stability: the inactivation rate constant is 0.0046 h within 120 h -1 ; and excellent catalytic selectivity: >99%; and at the same time has good regeneration stability: the catalyst shows no obvious inactivation after being regenerated three times.

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