A granular catalyst containing L molecular sieve and its preparation method and application

Abstract

The present disclosure relates to a granular catalyst containing L molecular sieve and a preparation method and application thereof, wherein the catalyst comprises an L molecular sieve carrier and a metal; based on the total weight of the L molecular sieve carrier, the content of the metal is 0.1 to 20 weight %; wherein the metal comprises a first metal and a second metal; the first metal comprises at least one of the metals of Group VIIIB; and the second metal comprises a metal of Group IA and / or a metal of Group IIA. The catalyst disclosed in the present disclosure has high reaction activity, selectivity and stability, and can effectively catalyze the aromatization of chain alkanes.

Description

Technical Field

[0001] The present disclosure relates to a catalyst and a preparation method thereof, and more specifically, to a granular catalyst containing L molecular sieve and a preparation method and application thereof. Background Art

[0002] Pt / L molecular sieve catalyst is a basic monofunctional catalyst with a special pore structure. Compared with traditional bifunctional reforming catalysts, Pt / L catalyst has better reaction activity, aromatization selectivity and catalyst life for normal straight-chain alkanes. The catalyst prepared by L molecular sieve can be used in industry after molding. After molding, due to the increase in the size of the molding carrier, the diffusion effect is limited and the alkaline characteristics of the L molecular sieve itself will affect the diffusion and distribution of the Pt precursor in the carrier.

[0003] U.S. Patent US20200010384 discloses a method for preparing a Pt / L catalyst. An L molecular sieve is formed with a binder having a binder content of 10% to 30%. The carrier is then subjected to the steps of calcination, washing, impregnation with an organic amine halide, and then calcination. The carrier is then impregnated with tetraammineplatinum dichloride and an organic amine halide to obtain a Pt / L catalyst, which catalyzes the aromatization reaction of fatty alkanes, improves the selectivity of aromatics, and reduces cracking reactions. However, after the carrier is impregnated with an organic amine halide, its specific surface area and pore volume are greatly reduced.

[0004] CN108236964 discloses a LTL molecular sieve exchanged with lanthanide metal ions, a bimetallic catalytic reforming catalyst loaded with VIIIB group metals and Sn or Re, wherein the lanthanide metal ion content is greater than or equal to 10 mol% of the total number of cations, and the VIIIB group metal content accounts for 0.1-3% of the carrier.

[0005] US Patent No. 6207042B1 discloses a halogenated reforming catalyst, wherein L molecular sieve and a binder are extruded into strips, the L molecular sieve content is 50-85%, and the Pt content is 0.3%-1.5%. After the L molecular sieve is formed, it is washed, impregnated with a Pt source and ammonium halide, and then dried and calcined to obtain the catalyst.

[0006] In the above-mentioned prior art, the platinum content inside the catalyst particles is significantly lower than that on the outer surface, and is distributed in an eggshell shape, resulting in low catalytic efficiency of the catalyst. Therefore, it is necessary to improve the distribution uniformity of Pt on the catalyst carrier. Summary of the invention

[0007] The purpose of the present disclosure is to provide a granular catalyst containing L molecular sieve and its preparation method and application, in which platinum is evenly distributed on a larger granular carrier, thereby improving the reforming reaction activity, selectivity and stability of the catalyst.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a granular catalyst containing L molecular sieve, which comprises an L molecular sieve carrier and a metal; based on the total weight of the L molecular sieve carrier, the content of the metal is 0.1 to 20 weight %; wherein the metal comprises a first metal and a second metal; the first metal comprises at least one of Group VIIIB metals; and the second metal comprises a Group IA metal and / or a Group IIA metal.

[0009] Optionally, the first metal includes metallic platinum; based on the total weight of the L molecular sieve carrier, the content of the metallic platinum is 0.1 to 3 weight %.

[0010] Optionally, based on the total weight of the L molecular sieve carrier, the content of the second metal is 0.1 to 15 weight %.

[0011] Optionally, the Group IA metal includes one or more of K, Rb and Cs; and the Group IIA metal includes Ca and / or Ba.

[0012] Optionally, the shape of the L molecular sieve carrier is cylindrical, spherical or irregular granular, and the minimum size of the L molecular sieve carrier is 1 to 10 mm, preferably 5 to 7 mm.

[0013] Optionally, the strength of the L molecular sieve carrier is above 80N / grain.

[0014] Optionally, the L molecular sieve carrier comprises L molecular sieve and a molding aid; based on the total weight of the L molecular sieve carrier, the content of the L molecular sieve is 10 to 100% by weight, and the content of the molding aid is 0 to 90% by weight;

[0015] The molding aid is selected from one or more of sesbania powder, methyl cellulose, kaolin and white carbon black.

[0016] Optionally, the catalyst has the following X-ray spectrum characteristics:

[0017] The value of I defined by the following formula (1) is any value between 0 and 0.9;

[0018] I=(I max -I min ) / I max Formula (1);

[0019] Among them I max represents the maximum value of the peak intensity in the cross-sectional X-ray spectrum of the catalyst, I min It represents the minimum value of the peak intensity in the cross-sectional X-ray spectrum of the catalyst.

[0020] A second aspect of the present disclosure provides a method for preparing the catalyst described in the first aspect of the present disclosure, the method comprising:

[0021] (1) exchanging the L molecular sieve carrier with a second metal ion, and drying to obtain a prefabricated molecular sieve carrier;

[0022] (2) The prefabricated molecular sieve carrier is placed in an impregnation solution for impregnation treatment, and then dried and calcined; the impregnation solution contains a first metal source and the second metal ion.

[0023] Optionally, in step (1), the second metal ion is used in the form of a dispersion containing a second metal compound; the second metal ion is K + , Rb + , Cs + , Ca 2+ Or Ba 2+ , the anion in the second metal compound is F - , Cl - Br - 、NO3 - and OH - One or more of the .

[0024] Optionally, in step (2), the first metal source is a salt solution of metal platinum.

[0025] Optionally, the conditions for the ion exchange include: an exchange temperature of 20 to 90° C., and an exchange time of 2 to 4 hours; the conditions for the immersion treatment include: an immersion temperature of 20 to 90° C., and an immersion time of 0.5 to 8 hours.

[0026] Optionally, in step (2), the volume of the impregnation solution is 1 to 10 times, preferably 3 to 8 times, the total pore volume of the prefabricated molecular sieve carrier; the molar ratio of the second metal ion to the platinum ion in the impregnation solution is 1 to 10, preferably 3 to 8; the molar concentration of the platinum ion in the impregnation solution is 0.003 to 0.09 mol / L.

[0027] The third aspect of the present disclosure provides a use of the granular L-containing molecular sieve catalyst described in the first aspect of the present disclosure in catalyzing aromatization of chain alkanes.

[0028] Through the above technical scheme, the present invention promotes the diffusion of metallic platinum into the interior of the granular L molecular sieve carrier through ion exchange and impregnation treatment, so that the platinum content on the interior and exterior surfaces of the catalyst is basically consistent, which can effectively catalyze the aromatization of chain alkanes and has high reaction activity, selectivity and stability; the method of the present invention is simple to operate and can prepare a granular L molecular sieve-containing catalyst with high aromatization reaction activity.

[0029] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0031] Figure 1 is a TEM-EDX image of a cross section of the catalyst 1 disclosed herein;

[0032] Figure 2 is a TEM-EDX image of a cross section of the catalyst 2 disclosed herein;

[0033] Figure 3 This is a TEM-EDX image of the cross section of Comparative Example 2. DETAILED DESCRIPTION

[0034] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0035] The first aspect of the present disclosure provides a granular catalyst containing L molecular sieve, the catalyst comprising an L molecular sieve carrier and a metal; based on the total weight of the L molecular sieve carrier, the content of the metal is 0.1 to 20 weight %; wherein the metal comprises a first metal and a second metal; the first metal comprises at least one of Group VIIIB metals; the second metal comprises a Group IA metal and / or a Group IIA metal;

[0036] In one embodiment of the present disclosure, based on the total weight of the L molecular sieve carrier, the content of the metal is 0.1 to 15 wt %; more preferably, the content of the metal is 2 to 13 wt %.

[0037] The granular L molecular sieve-containing catalyst disclosed in the present invention can effectively catalyze the aromatization of chain alkanes and has good reaction activity, selectivity and stability.

[0038] In one embodiment of the present disclosure, the first metal includes metallic platinum; based on the total weight of the L molecular sieve carrier, the content of the metallic platinum is 0.1 to 3 weight %, preferably 0.25 to 2 weight %.

[0039] In one embodiment of the present disclosure, based on the total weight of the L molecular sieve carrier, the content of the second metal is 0.1 to 15 wt %, preferably 2 to 10 wt %.

[0040] In one embodiment of the present disclosure, the Group IA metal includes one or more of K, Rb and Cs; and the Group IIA metal includes Ca and / or Ba.

[0041] In the above embodiment, by adjusting the ratio and content of metal platinum, Group IA metal and / or Group IIA metal, the uniform distribution of metal platinum inside the catalyst can be further promoted, thereby improving the reaction activity of the catalyst in the aromatization of chain alkanes.

[0042] In one embodiment of the present disclosure, the shape of the L molecular sieve carrier is cylindrical, spherical or irregular granular, and the minimum size of the L molecular sieve carrier is 1 to 10 mm. Wherein "minimum size" refers to the minimum effective size of the L molecular sieve carrier. For a cylindrical L molecular sieve carrier, the minimum size of the L molecular sieve carrier refers to the smaller value of the cylinder diameter and the column height; for a spherical or quasi-spherical L molecular sieve carrier, the minimum size of the L molecular sieve carrier refers to the diameter of the sphere or the minimum diameter of the quasi-sphere; for an irregular granular L molecular sieve carrier, the minimum size of the L molecular sieve carrier refers to the minimum value of all particle sizes of the particles. In a preferred specific embodiment, the minimum size of the L molecular sieve carrier is 5 to 7 mm.

[0043] In a specific embodiment, the strength of the L molecular sieve carrier is above 80 N / particle, for example, 80 to 200 N / particle.

[0044] In a specific embodiment, the L molecular sieve carrier comprises L molecular sieve and a molding aid; based on the total weight of the L molecular sieve carrier, the content of the L molecular sieve is 10 to 100 weight %, and the content of the molding aid is 0 to 90 weight %;

[0045] The molding aid is selected from one or more of sesbania powder, methyl cellulose, kaolin and white carbon black.

[0046] In one embodiment of the present disclosure, the catalyst has the following X-ray spectrum characteristics:

[0047] The value of I defined by the following formula (1) is any value between 0 and 0.9, preferably any value between 0 and 0.5;

[0048] I=(I max -I min ) / I max Formula (1);

[0049] Among them I max represents the maximum value of the peak intensity in the cross-sectional X-ray spectrum of the catalyst, I min It represents the minimum value of the peak intensity in the cross-sectional X-ray spectrum of the catalyst.

[0050] In the above embodiment, the L molecular sieve carrier includes an L molecular sieve and a molding aid. The L molecular sieve carrier has a porous structure, which can further promote the diffusion of metal platinum into the interior of the L molecular sieve carrier and improve the catalytic efficiency of the catalyst.

[0051] A second aspect of the present disclosure provides a method for preparing the catalyst described in the first aspect of the present disclosure, the method comprising:

[0052] (1) exchanging the L molecular sieve carrier with a second metal ion, and drying to obtain a prefabricated molecular sieve carrier;

[0053] (2) The prefabricated molecular sieve carrier is placed in an impregnation solution for impregnation treatment, and then dried and calcined; the impregnation solution contains a first metal source and the second metal ion.

[0054] In the above embodiment, a granular catalyst containing L molecular sieve with uniform distribution of metal platinum is prepared, which can effectively catalyze the aromatization of chain alkanes and has high reaction activity, selectivity and stability.

[0055] In one embodiment, in step (1), the second metal ion is used in the form of a dispersion containing a second metal compound, such as a solution containing the second metal compound or a suspension containing the second metal compound, wherein the second metal compound can be a salt of the second metal or a base of the second metal. In one embodiment of the present disclosure, the second metal ion is K + , Rb + , Cs + , Ca 2+ Or Ba 2+ , the anion in the second metal compound is F - , Cl - Br - 、NO3 - and OH - Further, the second metal compound may be one or more of CsCl, KNO3, RbNO3, Ca(OH)2, Ba(OH)2 and Ba(NO3)2.

[0056] In one embodiment of the present disclosure, the first metal source in step (2) is a salt solution of metal platinum.

[0057] In one embodiment of the present disclosure, the conditions of the ion exchange include: an exchange temperature of 20 to 90° C., and an exchange time of 2 to 4 h;

[0058] The conditions of the immersion treatment include: an immersion temperature of 20 to 90° C. and an immersion time of 0.5 to 8 hours.

[0059] In one embodiment of the present disclosure, the volume of the impregnation solution in step (2) is 1 to 10 times, preferably 3 to 8 times, the total pore volume of the prefabricated molecular sieve carrier; the molar ratio of the second metal ion to the platinum ion in the impregnation solution is 1 to 10, preferably 3 to 8; the molar concentration of the platinum ion in the impregnation solution is 0.003 to 0.09 mol / L.

[0060] In the above embodiment, by adjusting the impregnation solution and the impregnation method, the diffusion of platinum into the interior of the L molecular sieve carrier during the impregnation process is promoted, so that the platinum is evenly distributed on the carrier.

[0061] The third aspect of the present disclosure provides a use of the granular L-containing molecular sieve catalyst described in the first aspect of the present disclosure in catalyzing aromatization of chain alkanes.

[0062] The present invention adds a metal salt solution by an impregnation method, which is beneficial to the adsorption of metal platinum on the L molecular sieve, so that the platinum is evenly dispersed on the large particle carrier, and the reforming reaction activity of the catalyst is improved.

[0063] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0064] In the following examples, unless otherwise specified, the raw materials used are commercially available products.

[0065] In the following examples, the specific testing methods are as follows:

[0066] The radial distribution of Pt on the catalyst cross section was analyzed using a Japanese JEOL JXA8800R electron probe analyzer and a British Oxford ISIS300 X-ray energy dispersive spectrometer.

[0067] The diameter and height of the carrier particles were measured using a vernier caliper;

[0068] The carrier strength was tested using a KC-3 automatic particle strength tester;

[0069] The specific surface area, pore volume and pore distribution of the catalyst were determined by BET method on ASAP2400 static nitrogen adsorption instrument produced by Micromerities Company of the United States.

[0070] Carrier Preparation Example 1

[0071] (1) Preparation of L molecular sieve powder:

[0072] Take a certain amount of Al(OH)3 and dissolve it in deionized water. After stirring evenly, add silica sol solution (containing 25% SiO2, pH 9) to the mixture and continue stirring to form a uniform mixture. Transfer the mixture into a stainless steel reactor and crystallize it at 150°C for 36 hours. After washing and drying, the product is obtained as a crystallized product, i.e., L molecular sieve, with a relative crystallinity of 95% and a specific surface area of ​​310 m 2 / g, and the silicon-aluminum ratio is 5.

[0073] (2) Carrier preparation:

[0074] 10 kg of the L molecular sieve powder prepared above was mixed with 1 kg of methyl cellulose, water was added, and the mixture was formed in a ball rolling machine to obtain a spherical carrier with a diameter of about 6 mm, thereby obtaining a carrier 1.

[0075] Carrier Preparation Example 2

[0076] The preparation process is the same as that of carrier 1, except that 1 kg of methyl cellulose is replaced with 0.5 kg of kaolin to obtain a spherical carrier with a diameter of about 6 mm, namely carrier 2.

[0077] Example 1

[0078] Take 10g of carrier 1, add 0.3M CsCl solution (50ml / g catalyst), stir for 2h at 70℃, perform ion exchange, repeat twice, wash the carrier with deionized water, filter, and dry at 120℃ for 12h to obtain Cs-L molecular sieve carrier. Dissolve 0.17g dichlorotetraammineplatinum and 0.259g CsCl in 7ml deionized water, stir well to obtain impregnation solution, slowly pour the impregnation solution into 10g Cs-L carrier, impregnate at 80℃ for 6h, filter, dry at 120℃ for 12h, and calcine at 350℃ for 2h to obtain catalyst 1.

[0079] Example 2

[0080] Take 10g of carrier 1, add 0.3M KNO3 solution (50ml / g catalyst), stir for 2h at 70℃, perform ion exchange, repeat twice, wash the carrier with deionized water, filter, and dry at 120℃ for 12h to obtain KL molecular sieve carrier. Dissolve 0.17g dichlorotetraammineplatinum and 0.258g KNO3 in 8.6ml deionized water, stir well to obtain impregnation solution, slowly pour the impregnation solution into 10g KL carrier, impregnate at 60℃ for 3h, filter, dry at 120℃ for 12h, and calcine at 350℃ for 2h to obtain catalyst 2.

[0081] Example 3

[0082] Take 10g of carrier 1, add 0.3M Ca(OH)2 solution (50ml / g catalyst), stir for 2h at 70℃, perform ion exchange, repeat twice, wash the carrier with deionized water, filter, and dry at 120℃ for 12h to obtain Ca-L molecular sieve carrier. Dissolve 0.17g dichlorotetraammineplatinum and 0.305g CaBr2 in 6.5ml deionized water, stir well to obtain impregnation solution, slowly pour the impregnation solution into 10g Ca-L carrier, impregnate at 50℃ for 7h, filter, dry at 120℃ for 12h, and calcine at 350℃ for 2h to obtain catalyst 3.

[0083] Example 4

[0084] Take 10g of carrier 1, add 0.2M Ba(OH)2 solution (50ml / g catalyst), stir for 2h at 90℃, perform ion exchange, repeat twice, wash the carrier with deionized water, filter, and dry at 120℃ for 12h to obtain Ba-L molecular sieve carrier. Dissolve 0.13g dichlorotetraammineplatinum and 0.267g Ba(OH)2 in 13ml deionized water, stir well to obtain impregnation solution, slowly pour the impregnation solution into 10g Ba-L carrier, impregnate at 30℃ for 6h, filter, dry at 120℃ for 12h, and calcine at 350℃ for 2h to obtain catalyst 4.

[0085] Example 5

[0086] Catalyst 5 was obtained by using the preparation method and raw materials of Example 1, except that carrier 1 was replaced by carrier 2.

[0087] Comparative Example 1

[0088] 0.17 g of dichlorotetraammineplatinum and 0.259 g of CsCl were dissolved in 7 ml of deionized water, and after sufficient stirring, the solution was slowly poured into 10 g of L molecular sieve carrier that had not been exchanged with Cs. After immersion at 80°C for 6 h, the solvent was evaporated, dried at 120°C for 12 h, and calcined at 350°C for 2 h to obtain contrast agent 1.

[0089] Comparative Example 2

[0090] Take 10 g of the Cs-L carrier obtained by Cs exchange in Example 1, 0.17 g of tetraammine dichloroplatinum and 0.258 g of KNO3, dissolve them in 8.6 ml of deionized water, stir them thoroughly to dissolve, slowly pour the above solution into the Cs-L molecular sieve carrier, soak at 80°C for 6 h, evaporate the solvent, dry at 120°C for 12 h, and calcine at 350°C for 2 h to obtain contrast agent 2.

[0091] Comparative Example 3

[0092] Take 10 g of the KL carrier obtained by K exchange in Example 2, 0.17 g of dichlorotetraammineplatinum and 0.217 g of NaNO3, dissolve them in 8.6 ml of deionized water, stir them thoroughly to dissolve, slowly pour the above solution into the KL molecular sieve carrier, soak at 80°C for 6 hours, evaporate the solvent, dry at 120°C for 12 hours, and calcine at 350°C for 2 hours to obtain contrast agent 3.

[0093] Comparative Example 4

[0094] Dissolve 0.17 g of tetraammine dichloroplatinum in 7 ml of deionized water, stir thoroughly to dissolve, and slowly pour the solution into 10 g of unexchanged L molecular sieve carrier. After immersion at 80°C for 6 hours, evaporate the solvent, dry at 120°C for 12 hours, and calcine at 350°C for 2 hours to obtain contrast agent 4.

[0095] Test Example 1

[0096] The radial distribution of Pt on the cross-section of the catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 4 was tested, wherein the results of Catalyst 1 are as follows: Figure 1 The results of catalyst 2 are shown in Figure 2 As shown, the results of contrast agent 2 are as follows Figure 3 shown.

[0097] The I value of each catalyst was calculated according to formula (1) and the results are listed in Table 1.

[0098] Table 1

[0099]

[0100]

[0101] Test Example 2

[0102] The catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were first reduced in hydrogen at 480° C. for 2 h, and then aromatized using a mixture of n-hexane, 2-methylpentane and 3-methylpentane as a raw material at a temperature of 450° C. and a pressure of 0.5 MPa. The product results after reaction for 3 h and 20 h are shown in Table 2.

[0103] n-C6 conversion rate = 100% × [w(n-C6) 反应物 -w(n-C6) 产物 ] / w(n-C6) 反应物

[0104] Benzene yield = 100% x w (benzene) 产物 / 1

[0105] Among them, w(n-C6) 反应物Indicates the mass fraction of n-hexane in the reactant, w(n-C6) 产物 Indicates the mass fraction of n-hexane in the product, w(benzene) 产物 Indicates the mass fraction of benzene in the product;

[0106] n-C6 conversion rate retention rate = 100% × 20h reaction conversion rate / 3h reaction conversion rate

[0107] Benzene yield retention rate = 100% × Benzene yield after 20 hours of reaction / Benzene yield after 3 hours of reaction

[0108] Table 2:

[0109]

[0110]

[0111] From the above data, it can be seen that Examples 1 to 5 adopt the preparation method disclosed in the present invention to obtain a granular catalyst containing L molecular sieve with uniform platinum dispersion, which has high catalytic activity when used for aromatization of chain alkane, high conversion rate of chain C6 alkane, high benzene selectivity, good catalyst stability, and can maintain catalytic activity for a long time. However, Comparative Examples 1 to 4 adopt a conventional impregnation method, and the n-C6 conversion rate and benzene yield are low, and the catalytic activity is poor.

[0112] Furthermore, from the comparison of the data of Example 1 with that of Comparative Example 1, it can be seen that the catalyst prepared by first performing ion exchange on the L molecular sieve carrier and the second metal ion and then performing impregnation treatment using the method of the present invention has better catalytic performance; from the comparison of the data of Example 1 with Comparative Examples 2 to 3, it can be seen that the catalyst prepared by first performing ion exchange and then performing impregnation treatment using an impregnation solution containing a first metal source and the second metal ion identical to that in the ion exchange step using the method of the present invention has better catalytic performance; from the comparison of the data of Example 1 with Comparative Example 4, it can be seen that the catalyst prepared by the preparation method of the present invention has better catalytic effect.

[0113] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0114] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0115] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A granular catalyst containing L molecular sieve, characterized in that: The catalyst comprises an L molecular sieve carrier and a metal; based on the total weight of the L molecular sieve carrier, the content of the metal is 0.1 to 20 weight %; wherein the L molecular sieve carrier comprises an L molecular sieve and a molding aid, and the molding aid is selected from methyl cellulose; the metal comprises a first metal and a second metal; the first metal comprises platinum; the second metal comprises a Group IA metal and / or a Group IIA metal, the Group IA metal is K or Cs, and the Group IIA metal is Ca; The catalyst has the following X-ray spectrum characteristics: The value of I defined by the following formula (1) is any value between 0 and 0.455; I = (I max -I min ) / I max Formula (1); Among them I max represents the maximum value of the peak intensity in the cross-sectional X-ray spectrum of the catalyst, I min It represents the minimum value of the peak intensity in the cross-sectional X-ray spectrum of the catalyst.

2. The catalyst according to claim 1, characterized in that Based on the total weight of the L molecular sieve carrier, the content of the metal platinum is 0.1 to 3 weight %.

3. The catalyst according to claim 1, characterized in that Based on the total weight of the L molecular sieve carrier, the content of the second metal is 0.1 to 15 weight %.

4. The catalyst according to claim 1, characterized in that The shape of the L molecular sieve carrier is cylindrical, spherical or irregular granular, and the minimum size of the L molecular sieve carrier is 1 to 10 mm.

5. The catalyst according to claim 4, characterized in that The minimum size of the L molecular sieve carrier is 5 to 7 mm.

6. The catalyst according to claim 1, characterized in that The strength of the L molecular sieve carrier is above 80N / grain.

7. The catalyst according to claim 1, characterized in that Based on the total weight of the L molecular sieve carrier, the content of the L molecular sieve is 10 to 100 weight %, and the content of the molding aid is 0 to 90 weight %.

8. A method for preparing the catalyst according to any one of claims 1 to 7, characterized in that: The method includes: (1) exchanging the L molecular sieve carrier with a second metal ion, and drying to obtain a prefabricated molecular sieve carrier; (2) The prefabricated molecular sieve carrier is placed in an impregnation solution for impregnation treatment, and then dried and calcined; the impregnation solution contains a first metal source and the second metal ion.

9. The method according to claim 8, wherein: In step (1), the second metal ion is used in the form of a dispersion containing a second metal compound; the second metal ion is K + , Cs + or Ca 2+ , the anion in the second metal compound is F - , Cl - Br - 、NO3 - and OH - One or more of the .

10. The method according to claim 8, characterized in that In step (2), the first metal source is a salt solution of metal platinum.

11. The method according to claim 8, characterized in that The ion exchange conditions include: an exchange temperature of 20 to 90° C. and an exchange time of 2 to 4 hours; The conditions of the immersion treatment include: an immersion temperature of 20 to 90° C. and an immersion time of 0.5 to 8 hours.

12. The method according to claim 8, characterized in that In step (2), the volume of the impregnation solution is 1 to 10 times the total pore volume of the prefabricated molecular sieve carrier, the molar ratio of the second metal ion to the platinum ion in the impregnation solution is 1 to 10, and the molar concentration of the platinum ion in the impregnation solution is 0.003 to 0.09 mol / L.

13. The method according to claim 12, characterized in that In step (2), the volume of the impregnation solution is 3 to 8 times the total pore volume of the prefabricated molecular sieve carrier, and the molar ratio of the second metal ion to the platinum ion in the impregnation solution is 3 to 8.

14. Use of the granular catalyst containing L molecular sieve according to any one of claims 1 to 7 in catalyzing aromatization of chain alkanes.

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