Alkane hydroisomerization catalyst and preparation method and application thereof

Abstract

The invention discloses an alkane hydroisomerization catalyst as well as a preparation method and application thereof. The catalyst provided by the invention comprises a Pt active metal component and a molecular sieve carrier, wherein the number of Pt metal particles located near the aperture of the molecular sieve carrier accounts for 85%-100% of the total number of Pt metal particles. The catalyst disclosed by the invention is applied to alkane hydroisomerization reaction and shows excellent target product selectivity and conversion rate.

Description

Technical Field

[0001] The invention belongs to the field of alkane isomerization reaction, and specifically relates to an alkane hydroisomerization catalyst and a preparation method and application thereof. Background Art

[0002] With the worsening of environmental pollution and the enhancement of environmental awareness, there will be a great demand for high-quality isomerized oil blending components with low sulfur, low olefin and low aromatic content in the future. Isomerized oil mainly comes from the isomerization reaction process of normal low-carbon alkanes, which can selectively convert low-octane normal alkanes into high-octane isoalkanes. In industry, the alkane isomerization catalyst used is mainly a medium-temperature metal / molecular sieve bifunctional catalytic system, in which the metal active sites (Pt, Pd) mainly provide hydrogenation-dehydrogenation functions, while the molecular sieve system (including ZSM-5, MOR, Y, etc.) mainly provides acid sites and pore shape selection functions. Many documents point out (for example, GUISNET M. "Ideal" bifunctional catalysis over Pt-acid zeolites [J]. Catalysis Today, 2013, 218-219: 123-134.), that the process follows a typical bifunctional synergistic catalytic reaction mechanism. In an ideal isomerization reaction, n-alkanes are first dehydrogenated on metals to generate n-olefins, and then n-olefins diffuse to the acid sites of molecular sieves and undergo skeletal isomerization to generate isoolefin intermediates, which are then returned to the metal sites for hydrogenation to generate target product isoalkane. However, in the actual reaction process, the narrow microporous channels of molecular sieves will limit the rapid separation of olefin intermediates, resulting in excessive contact with too many strong B acid sites inside the microporous channels, cracking to generate small molecules such as C3 and C4, hindering the efficient synthesis of isomers. Therefore, it is urgently needed to develop a new metal-molecular sieve catalytic system to inhibit the cracking side reactions inside the microporous channels of molecular sieves.

[0003] In the process of catalyst preparation, adjusting the location of Pt metal is extremely critical. De Jong's research group (Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons. Nature. 2015, 528: 245-248) placed the metal site on the alumina binder, controlling the Pt and Y molecular sieve pores to be in nanoscale contact with the acid sites inside the channels. At this time, the olefin intermediates formed during the reaction will preferentially undergo "pore mouth catalysis", thereby maximally suppressing the cracking process of the intermediates inside the micropore channels of the molecular sieve. Similarly, CN111215131A discloses an isomerization catalyst and a preparation method using an MTW-type structural molecular sieve as a carrier. The carbon deposits generated in situ during the preparation process partially fill the micropore channels of the molecular sieve, shorten the channel depth, cover some of the strong B acid sites in the micropores, significantly improve the mass transfer of reactants and intermediates, and the prepared catalyst exhibits excellent isomerization performance. However, in the traditional preparation process of metal / molecular sieve bifunctional catalysts, including impregnation method, ion exchange method, etc., after subsequent calcination and other treatments, metal Pt will preferentially combine with the strong B acid sites inside the pores, resulting in most of the Pt in the final catalyst being located inside the microporous channels. Olefin intermediates will have to enter the microporous channels, and the narrow micropores inside the channels greatly limit the intermediate mass transfer process, and cracking side reactions are inevitable. Summary of the invention

[0004] In view of the serious cracking side reaction problem in the process of normal alkane isomerization hydrogenation reaction in the prior art, the present invention provides an alkane hydroisomerization catalyst and its preparation method and application. Compared with the metal / molecular sieve system obtained by the traditional preparation method, the alkane hydroisomerization catalyst of the present invention has a higher conversion rate and isomerization product selectivity in the normal alkane isomerization hydrogenation reaction.

[0005] The first aspect of the present invention provides an alkane hydroisomerization catalyst, comprising a Pt active metal component and a molecular sieve carrier component; wherein the number of Pt metal particles located at the pores of the molecular sieve carrier accounts for 85% to 100% of the total number of Pt metal particles.

[0006] Furthermore, the molecular sieve is selected from one or more of ZSM-5, ZSM-22, ZSM-35 or ZSM-11 having a ten-membered ring pore structure, preferably one or more of ZSM-22 and ZSM-11.

[0007] Furthermore, based on the mass of the catalyst, the content of the Pt active metal component in terms of Pt is 0.01 wt% to 10.0 wt%, preferably 0.1 wt% to 2.5 wt%.

[0008] Furthermore, the average particle size of the Pt metal particles is 0.2 to 2.0 nm.

[0009] The second aspect of the present invention provides a method for preparing an alkane hydroisomerization catalyst, comprising the following steps:

[0010] (1) The original powder of Na-type molecular sieve is post-treated with a modifier and calcined to obtain a modified molecular sieve;

[0011] (2) The modified molecular sieve obtained in step (1) is loaded with Pt to obtain the catalyst.

[0012] Furthermore, in step (1), the Na-type molecular sieve is selected from one or more of ZSM-5, ZSM-22, ZSM-35 or ZSM-11 having a ten-membered ring pore structure, preferably one or more of ZSM-22 and ZSM-11. The Si / Al molar ratio of the Na-type molecular sieve raw powder is 15 to 80, preferably 30 to 45.

[0013] Furthermore, in step (1), the Na-type molecular sieve raw powder has a Na content of 0.1wt% to 2.5wt%, preferably 1.0wt% to 2.5wt%, based on the mass of the Na-type molecular sieve.

[0014] Furthermore, in step (1), the specific surface area of ​​the Na-type molecular sieve raw powder is 220 to 630 m 2 / g, pore volume is 0.11~0.25cm 3 / g.

[0015] Furthermore, in step (1), the concentration of the modifying agent solution is 0.005 mol / L to 3.5 mol / L, preferably 0.1 mol / L to 3.0 mol / L.

[0016] Furthermore, in step (1), the mass ratio of the modifier to the Na-type molecular sieve raw powder is 5:95 to 60:40.

[0017] Furthermore, in step (1), the modifier is one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium bromide, hexadecylammonium hydroxide, and hexadecylammonium bromide; preferably, the modifier is one or more of tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0018] Furthermore, in step (1), the post-treatment is carried out under stirring, and the post-treatment conditions are: temperature of 25 to 90° C., preferably 25 to 60° C., and time of 5 min to 24 h, preferably 1 to 10 h.

[0019] Furthermore, in step (1), after the post-treatment is completed, the filtrate is first filtered, washed and dried. The filtering, washing and drying are all conventional techniques in the art. The calcination conditions are: a temperature of 450 to 650° C., preferably 500 to 600° C., and a time of 30 min to 24 h, preferably 1 to 6 h.

[0020] Furthermore, in step (2), the method of loading Pt is ion exchange. The modified molecular sieve and the Pt precursor solution (solid-liquid mass ratio 2:1 to 1:50) are stirred at 25 to 40°C for 0.5 to 48 hours, and then solid-liquid separation, drying, and roasting are performed to obtain the catalyst. Furthermore, the solid-liquid separation, drying, and roasting are conventional operations in the art. Among them, the drying conditions are as follows: temperature 40 to 120°C, time 2 to 15 hours; the roasting conditions are as follows: temperature 350 to 500°C, time 2 to 15 hours.

[0021] Furthermore, in step (2), the precursor of Pt is one or more of tetraamine platinum nitrate, tetraamine platinum chloride, tetraamine platinum acetate or tetraamine platinum sulfate, preferably tetraamine platinum nitrate.

[0022] Furthermore, the Pt concentration in the Pt precursor solution is 0.001 mg Pt / mL~10.50mg Pt / mL, preferably 1.0mg Pt / mL~5.0mg Pt / mL.

[0023] Furthermore, in the catalyst prepared by the method, the number of Pt metal particles located at the pores of the molecular sieve carrier accounts for 85% to 100% of the total number of Pt metal particles.

[0024] Furthermore, in the catalyst prepared by the method, the content of the Pt active metal component in terms of Pt is 0.01 wt% to 10.0 wt%, preferably 0.1 wt% to 2.5 wt%, based on the mass of the catalyst.

[0025] Furthermore, the average particle size of the Pt metal particles is 0.2 to 2.0 nm.

[0026] The third aspect of the present invention provides use of the above-mentioned alkane hydroisomerization catalyst in alkane hydroisomerization reaction.

[0027] Furthermore, the alkane is at least one of normal alkanes having 5 to 9 carbon atoms (such as at least one of n-pentane, n-hexane, n-heptane and n-octane).

[0028] Furthermore, the reaction conditions are: temperature of 200-405°C, pressure of 0.1-3.0 MPa, molar ratio of hydrogen to alkane of 1.0-10.0, mass space velocity of alkane of 1.0-8.0 h -1 .

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention provides a novel alkane hydroisomerization catalyst, comprising a Pt active metal component and a molecular sieve carrier component; wherein, under high-angle annular dark-field scanning transmission electron microscopy, the number of Pt metal particles located near the pores of the molecular sieve carrier accounts for 85% to 100% of the total number of Pt metal particles. The catalyst of the present invention is applied to the alkane isomerization reaction process, significantly improving the isomer selectivity and showing a lower cracking product selectivity.

[0031] (2) The present invention uses a specific modifier to post-treat the Na-type molecular sieve. Due to the large size of the specific modifier, it is only allowed to exchange the Na at the pore opening and the outer surface of the molecular sieve, so that most of the B acid centers are present near the pore opening of the molecular sieve. In the subsequent ion exchange method for loading the Pt component, the location of the metal center is optimized, and the proportion of metal Pt at the pore opening of the molecular sieve is significantly increased, resulting in an alkane hydroisomerization catalyst that exhibits excellent isomerization product selectivity in the alkane isomerization reaction. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solution of the present invention, the following specific implementation examples are listed. However, it is easy for those skilled in the art to understand that the contents described in the embodiments are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0033] In the present invention, a high-angle annular dark-field scanning transmission electron microscope was used to observe the catalyst and count the number of Pt near the pores of the molecular sieve (N M ), the instrument model is FEI Titan Cubed Themis G2300kV, and the total number of Pt particles counted is 400.

[0034] In the present invention, the parameters of the Na-type ZSM-5 molecular sieve raw powder used are as follows: SiO2 / Al2O3=35, specific surface area (S BET )=535m 2 / g, pore volume = 0.12cm 3 / g, based on mass, the Na content is 2.0wt%.

[0035] In the present invention, the parameters of the ZSM-22 molecular sieve raw powder used are as follows: SiO2 / Al2O3=45, specific surface area (S BET )=525m 2 / g, pore volume = 0.20cm 3 / g, based on mass, the Na content is 2.3wt%.

[0036] In the present invention, the parameters of the Na-type ZSM-35 molecular sieve raw powder used are as follows: SiO2 / Al2O3=40, specific surface area (S BET )=538m 2 / g, pore volume = 0.22cm 3 / g, based on mass, the Na content is 1.3wt%.

[0037] In the present invention, the parameters of the Na-type ZSM-11 molecular sieve raw powder used are as follows: SiO2 / Al2O3=32, specific surface area (S BET )=625m 2 / g, pore volume = 0.18 cm 3 / g, based on mass, the Na content is 1.9wt%.

[0038] In the present invention, the reaction product was analyzed by Agilent 7890B gas chromatograph.

[0039] In the present invention, the calculation formulas for conversion rate and isomer selectivity are as follows:

[0040] Conversion rate = 1-(mass of isohexane in reactant / mass of n-hexane in feed) × 100%;

[0041] Isomer selectivity = (mass of isohexane in the product / total mass of the product) × 100%.

[0042] In order to facilitate the understanding of the present invention, the present invention lists the following embodiments, but the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0043] [Comparative Example 1]

[0044] Use ion exchange method to load Pt on Na-type ZSM-5 molecular sieve raw powder. The specific method is as follows: measure 5mL4mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g Na-type ZSM-5 molecular sieve powder was added, and stirred at 30°C for 24h. After filtering and washing, it was placed in a 90°C oven for drying for 15h, and then treated in a 500°C muffle furnace for 5h to obtain the catalyst of comparative example 1, which was recorded as D1. The number of Pt near the molecular sieve pores in the catalyst (N M) and their proportions are shown in Table 1.

[0045] [Comparative Example 2]

[0046] The Na-type ZSM-5 molecular sieve raw powder was placed in a 1.0 mol / L ammonium nitrate solution, stirred at 80°C for 3 hours, filtered and washed, and repeated twice. The filter cake was placed in a 90°C oven and dried for 10 hours, and then treated in a 550°C muffle furnace for 6 hours to obtain the modified ZSM-5 molecular sieve.

[0047] Pt was loaded on the modified ZSM-5 molecular sieve using the ion exchange method. The specific method is as follows: 5 mL 4 mg Pt / mL of Pt(NH3)4(NO3)2 solution was diluted with 35mL of deionized water, and 2g of the modified ZSM-5 molecular sieve was added, and stirred at 30°C for 24h. After filtering and washing, it was placed in a 90°C oven for drying for 15h, and then treated in a 500°C muffle furnace for 5h to obtain the catalyst of comparative example 2, which was recorded as D2. The number of Pt near the pores of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0048] [Comparative Example 3]

[0049] The Na-type ZSM-22 molecular sieve powder was placed in a 1.0 mol / L ammonium nitrate solution, stirred at 80°C for 3 hours, filtered and washed, and repeated twice. The filter cake was placed in a 90°C oven for 10 hours, and then treated in a 550°C muffle furnace for 6 hours to obtain the modified ZSM-22 molecular sieve. The modified ZSM-22 molecular sieve was placed in a 1.5 mol / L tetrabutylammonium hydroxide solution, and the ratio of tetrabutylammonium hydroxide to the Na-type ZSM-22 molecular sieve powder was 50:50 by mass. Stirred at 25°C for 1.0 hour, filtered and washed, dried, and then treated in a 600°C muffle furnace for 5 hours to obtain the modified ZSM-22 molecular sieve.

[0050] Pt was loaded on the modified ZSM-22 molecular sieve using the impregnation method. The specific method is as follows: 10 mL 2 mg Pt / mL chloroplatinic acid solution, add 2g of modified ZSM-22 molecular sieve, let it stand for 8h, then put it into a 90℃ oven for drying for 15h, and then treat it in a 500℃ muffle furnace for 5h to obtain the catalyst of comparative example 3, which is recorded as D3. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0051] [Comparative Example 4]

[0052] The Na-type ZSM-35 molecular sieve raw powder was placed in a 1.0 mol / L ammonium nitrate solution and stirred at 60°C for 24 hours. After filtering and washing, the filter cake was placed in a 90°C oven for drying for 10 hours, and then treated in a 550°C muffle furnace for 6 hours to obtain the modified ZSM-35 molecular sieve.

[0053] Pt was loaded on the modified ZSM-35 molecular sieve using the impregnation method. The specific method is as follows: 10 mL 3 mg Pt / mL chloroplatinic acid solution, add 2g of modified ZSM-35 molecular sieve, let it stand for 8h, then put it into a 90℃ oven for drying for 15h, and then treat it in a 500℃ muffle furnace for 5h to obtain the catalyst of comparative example 4, which is recorded as D4. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0054] [Comparative Example 5]

[0055] The Na-type ZSM-11 molecular sieve raw powder was placed in a 1.0 mol / L ammonium chloride solution, stirred at 80°C for 3 hours, filtered and washed, and repeated twice. The filter cake was placed in a 90°C oven and dried for 10 hours, and then treated in a 550°C muffle furnace for 6 hours to obtain the modified ZSM-11 molecular sieve.

[0056] Pt was loaded on the modified ZSM-11 molecular sieve using the ion exchange method. The specific method is as follows: 10 mL 2 mg Pt / mL of Pt(NH3)4(NO3)2 solution was diluted with 35mL of deionized water, and 2g of modified ZSM-5-11 molecular sieve was added, and stirred at 50°C for 12h. After filtering and washing, it was placed in a 90°C oven for drying for 15h, and then treated in a 500°C muffle furnace for 6h to obtain the catalyst of comparative example 5, which was recorded as D5. The number of Pt near the pores of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0057] [Comparative Example 6]

[0058] Pt was loaded on the Na-type ZSM-11 molecular sieve powder by impregnation. The specific method is as follows: 10 mL of 2 mg Pt / mL chloroplatinic acid solution was measured, 2 g of Na-type ZSM-11 molecular sieve powder was added, and after standing for 8 hours, it was placed in a 90 ° C oven for drying for 15 hours, and then treated in a 500 ° C muffle furnace for 5 hours to obtain the catalyst of comparative example 6, which was recorded as D6. The number of Pt near the molecular sieve pores in the catalyst (N M ) and their proportions are shown in Table 1.

[0059] [Comparative Example 7]

[0060] The Na-type ZSM-5 molecular sieve raw powder was placed in a 1.0 mol / L tetrapropylammonium hydroxide solution, and the mass ratio of tetrapropylammonium hydroxide to the Na-type ZSM-5 molecular sieve raw powder was 20:80. Stir at 50°C for 15 hours, filter and wash, dry, and then treat in a muffle furnace at 550°C for 6 hours to obtain the modified ZSM-5 molecular sieve.

[0061] Pt was loaded on the modified ZSM-5 molecular sieve obtained in Comparative Example 7 by impregnation method. The specific method is as follows: 5 mL of 4 mg Pt / mL chloroplatinic acid solution was measured, 2 g of the modified ZSM-5 molecular sieve was added, and after standing for 8 hours, it was placed in a 90°C oven for drying for 15 hours, and then treated in a 500°C muffle furnace for 5 hours to obtain the catalyst of Comparative Example 7, which was recorded as D7. The number of Pt near the pores of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0062] [Comparative Example 8]

[0063] The Na-type ZSM-5 molecular sieve raw powder was placed in a 1.0 mol / L tetrapropylammonium hydroxide solution, with the mass ratio of tetrapropylammonium hydroxide to Na-type ZSM-5 molecular sieve raw powder being 20:80. After sufficient stirring, it was transferred to a crystallization reactor and placed at 170°C for crystallization reaction for 15 hours. After filtering and washing, it was dried and then treated in a muffle furnace at 550°C for 6 hours to obtain the modified ZSM-5 molecular sieve.

[0064] Pt was loaded on the modified ZSM-5 molecular sieve obtained in Comparative Example 8 by ion exchange method. The specific method is as follows: 5 mL 4 mg Pt / mL of Pt(NH3)4(NO3)2 solution was diluted with 35mL of deionized water, and 2g of the modified ZSM-5 molecular sieve was added, and stirred at 30°C for 24h. After filtering and washing, it was placed in a 90°C oven for drying for 15h, and then treated in a 500°C muffle furnace for 5h to obtain the catalyst of comparative example 8, which was recorded as D8. The number of Pt near the pores of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0065] [Example 1]

[0066] The Na-type ZSM-5 molecular sieve raw powder was placed in a 1.0 mol / L tetrapropylammonium hydroxide solution, and the mass ratio of tetrapropylammonium hydroxide to the Na-type ZSM-5 molecular sieve raw powder was 20:80. Stir at 50°C for 5 hours, filter and wash, dry, and then treat in a muffle furnace at 550°C for 6 hours to obtain the modified ZSM-5 molecular sieve.

[0067] Pt was loaded on the modified ZSM-5 molecular sieve obtained in Example 1 by ion exchange method. The specific method is as follows: 5 mL 4 mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g of modified ZSM-5 molecular sieve was added, and stirred at 30℃ for 24h. After filtering and washing, it was placed in a 90℃ oven for drying for 15h, and then treated in a 500℃ muffle furnace for 5h to obtain the catalyst of Example 1, which was recorded as S1. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0068] [Example 2]

[0069] The Na-type ZSM-5 molecular sieve raw powder was placed in a 2.0 mol / L hexadecyl ammonium bromide solution, and the mass ratio of hexadecyl ammonium bromide to the Na-type ZSM-5 molecular sieve raw powder was 10:90. After stirring at 40°C for 8 hours, filtering and washing, drying, and then treating in a 500°C muffle furnace for 6 hours, the modified ZSM-5 molecular sieve was obtained.

[0070] Pt was loaded on the modified ZSM-5 molecular sieve obtained in Example 2 by ion exchange method. The specific method is as follows: 10 mL 2 mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g of modified ZSM-5 molecular sieve was added, and stirred at 30℃ for 24h. After filtering and washing, it was placed in a 90℃ oven for drying for 15h, and then treated in a 500℃ muffle furnace for 5h to obtain the catalyst of Example 2, which was recorded as S2. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0071] [Example 3]

[0072] The Na-type ZSM-22 molecular sieve raw powder was placed in a 1.5 mol / L tetrabutylammonium hydroxide solution, and the mass ratio of tetrabutylammonium hydroxide to the Na-type ZSM-22 molecular sieve raw powder was 50:50. Stir at 25°C for 1.0 hour, filter and wash, dry, and then treat in a muffle furnace at 600°C for 5 hours to obtain the modified ZSM-22 molecular sieve.

[0073] Pt was loaded on the modified ZSM-22 molecular sieve obtained in Example 3 by ion exchange method. The specific method is as follows: 10 mL 2 mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g of modified ZSM-22 molecular sieve was added, and stirred at 30℃ for 24h. After filtering and washing, it was placed in a 90℃ oven for drying for 15h, and then treated in a 500℃ muffle furnace for 5h to obtain the catalyst of Example 3, which was recorded as S3. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0074] [Example 4]

[0075] The Na-type ZSM-35 molecular sieve raw powder was placed in a 0.5 mol / L tetrapropylammonium hydroxide solution, and the mass ratio of tetrapropylammonium hydroxide to the Na-type ZSM-35 molecular sieve raw powder was 60:40. After stirring at 40°C for 6 hours, filtering and washing, drying, and then treating in a muffle furnace at 600°C for 5 hours, the modified ZSM-35 molecular sieve was obtained.

[0076] Pt was loaded on the modified ZSM-35 molecular sieve obtained in Example 4 by ion exchange method. The specific method is as follows: 10 mL 3 mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g of modified ZSM-35 molecular sieve was added, and stirred at 30℃ for 24h. After filtering and washing, it was placed in a 90℃ oven for drying for 15h, and then treated in a 500℃ muffle furnace for 5h to obtain the catalyst of Example 4, which was recorded as S4. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0077] [Example 5]

[0078] The Na-type ZSM-11 molecular sieve raw powder was placed in a 3.0 mol / L tetrabutylammonium hydroxide solution, and the mass ratio of tetrabutylammonium hydroxide to the Na-type ZSM-11 molecular sieve raw powder was 15:85. After stirring at 45°C for 10 hours, filtering and washing, drying, and then treating in a muffle furnace at 600°C for 5 hours, the modified ZSM-11 molecular sieve was obtained.

[0079] Pt was loaded on the modified ZSM-11 molecular sieve obtained in Example 5 by ion exchange method. The specific method is as follows: 10 mL 2 mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g of modified ZSM-11 molecular sieve was added, and stirred at 30℃ for 24h. After filtering and washing, it was placed in a 90℃ oven for drying for 15h, and then treated in a 550℃ muffle furnace for 6h to obtain the catalyst of Example 5, which was recorded as S5. The number of Pt near the pore of the molecular sieve in the catalyst (N M) and their proportions are shown in Table 1.

[0080] [Example 6]

[0081] The Na-type ZSM-11 molecular sieve raw powder was placed in a 2.5 mol / L tetrapropylammonium bromide solution, and the mass ratio of tetrapropylammonium bromide to the Na-type ZSM-11 molecular sieve raw powder was 5:95. After stirring at 60°C for 4 hours, filtering and washing, drying, and then treating in a muffle furnace at 600°C for 5 hours, the modified ZSM-11 molecular sieve was obtained.

[0082] Pt was loaded on the modified ZSM-11 molecular sieve obtained in Example 6 by ion exchange method. The specific method is as follows: 10 mL 2 mg Pt / mL Pt(NH3)4(NO3)2 solution was diluted with 35mL deionized water, and 2g of modified ZSM-11 molecular sieve was added, and stirred at 30℃ for 24h. After filtering and washing, it was placed in a 90℃ oven for drying for 15h, and then treated in a 550℃ muffle furnace for 6h to obtain the catalyst of Example 6, which was recorded as S6. The number of Pt near the pore of the molecular sieve in the catalyst (N M ) and their proportions are shown in Table 1.

[0083] [Example 7]

[0084] The catalysts of Examples 1-6 and Comparative Examples 1-8 were pressed into tablets, sieved through 20-40 mesh, and 0.3 g of the catalyst was placed in a fixed bed reactor. The temperature was raised from room temperature to 450°C at a rate of 10°C / min under a hydrogen atmosphere. After reduction for 2 hours, the catalyst was cooled to the reaction temperature and then evaluated.

[0085] The catalyst evaluation conditions were as follows: temperature 240 °C, pressure 2.0 MPa, molar ratio of hydrogen to n-hexane 6.0, mass space velocity of n-hexane 4.5 h -1 The evaluation results of each catalyst are shown in Table 1.

[0086] Table 1 Properties of catalysts and their evaluation results

[0087]

[0088] In Table 1, N M represents the number of Pt metal particles at the pores of the molecular sieve support, and N represents the total number of Pt metal particles in the molecular sieve support.

[0089] Table 2 Average particle size of Pt metal particles in each catalyst

[0090]

[0091]

[0092] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An alkane hydroisomerization catalyst, characterized in that: The catalyst comprises a Pt active metal component and a molecular sieve carrier component; wherein the number of Pt metal particles located at the pores of the molecular sieve carrier accounts for 85% to 100% of the total number of Pt metal particles.

2. The catalyst according to claim 1, characterized in that The molecular sieve is one or more of ZSM-5, ZSM-22, ZSM-35 or ZSM-11 having a ten-membered ring pore structure, preferably one or more of ZSM-22 and ZSM-11.

3. The catalyst according to claim 1, characterized in that Based on the mass of the catalyst, the content of the Pt active metal component is 0.01wt% to 10.0wt%, preferably 0.1wt% to 2.5wt%.

4. A method for preparing an alkane hydroisomerization catalyst, comprising the following steps: (1) The original powder of Na-type molecular sieve is post-treated with a modifier and calcined to obtain a modified molecular sieve; (2) The modified molecular sieve obtained in step (1) is loaded with Pt to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that: In step (1), the Na-type molecular sieve is selected from one or more of ZSM-5, ZSM-22, ZSM-35 or ZSM-11 having a ten-membered ring pore structure, preferably one or more of ZSM-22 and ZSM-11; And / or, the Si / Al molar ratio of the Na-type molecular sieve is 15 to 80; And / or, the Na-type molecular sieve raw powder has a Na content of 0.1wt% to 2.5wt%, preferably 1.0wt% to 2.5wt%, based on the mass of the Na-type molecular sieve.

6. The preparation method according to claim 4, characterized in that: In step (1), the concentration of the modifying agent solution is 0.005 mol / L to 3.5 mol / L, preferably 0.1 mol / L to 3.0 mol / L.

7. The preparation method according to claim 4 or 6, characterized in that: In step (1), the mass ratio of the modifier to the original Na-type molecular sieve powder is 5:95 to 60:

40.

8. The preparation method according to claim 4, characterized in that: In step (1), the modifier is one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium bromide, hexadecylammonium hydroxide, and hexadecylammonium bromide; preferably, the modifier is one or more of tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

9. The preparation method according to claim 4, characterized in that: In step (1), the post-treatment is carried out under stirring, and the post-treatment conditions are: temperature of 25 to 90° C., preferably 25 to 60° C., time of 5 min to 24 h, preferably 1 to 10 h; And / or, the calcination conditions are: temperature of 450-650° C., preferably 500-600° C., time of 30 min-24 h, preferably 1-6 h.

10. The preparation method according to claim 4, characterized in that: In step (2), the method of loading Pt is an ion exchange method, and the Pt precursor used is one or more of tetraammine platinum nitrate, tetraammine platinum chloride, tetraammine platinum acetate or tetraammine platinum sulfate, preferably tetraammine platinum nitrate; and / or, the Pt concentration in the Pt precursor solution is 0.001 mg Pt / mL~10.50mg Pt / mL, preferably 1.0mg Pt / mL~5.0mgPt / mL.

11. Use of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by any one of claims 4 to 10 in the hydroisomerization reaction of alkanes.

12. The use according to claim 11, characterized in that: The reaction conditions are: temperature of 200-405°C, pressure of 0.1-3.0 MPa, molar ratio of hydrogen to alkane of 1.0-10.0, mass space velocity of alkane of 1.0-8.0 h -1 .

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