Catalysts for the normal isomerization of alkane, their preparation methods and applications

Abstract

This invention relates to the field of light alkane normal isomerization technology, and discloses an alkane normal isomerization catalyst, its preparation method, and its application. The catalyst includes an acidic active component, SO4. 2‑ The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; wherein the mass ratio of the acidic active component (calculated as ZrO2) to the mass ratio of the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1). This catalyst modulates the acid centers of the catalyst using an all-silica molecular sieve with an MFI structure, optimizing the distribution of acid centers without altering the active phase structure or acid strength. This results in the catalyst exhibiting good activity and selectivity in the normal isomerization reaction of light alkanes.

Description

Technical Field

[0001] This invention relates to the field of light alkane normal isomerization technology, specifically to an alkane normal isomerization catalyst, its preparation method, and its application. Background Technology

[0002] Light alkane isomerization mainly includes C5 / C6 isomerization, n-butane isomerization, and isobutane isomerization. C5 / C6 isomerization is used to produce C5 / C6 isomerized oil, which is essentially free of sulfur, olefins, and aromatics, making it an important component for clean gasoline blending. n-Butane isomerization converts n-butane to isobutane, providing isobutane feedstock for processes such as butane-butene alkylation, isobutane-propylene co-oxidation (PO / MTBE), C3 / iC4 alkane dehydrogenation, and isobutane dehydrogenation. Therefore, light alkane isomerization is a crucial supporting technology for upgrading oil quality, an important means of expanding feedstock sources for ethylene plants, and a key unit technology in processes such as n-butane oxidation to maleic anhydride, C3 / C4 alkane dehydrogenation, isobutane dehydrogenation, and PO / MTBE.

[0003] Solid superacid catalysts are a novel type of catalyst developed in recent years. Among them, zirconium-based solid superacid catalysts promoted by inorganic acids have shown good performance in the isomerization reaction of light hydrocarbons. CN1164509A discloses a molecular sieve-type superacid and its preparation method. The catalyst is a hydrogen-form ZSM-5, ZSM-11, or β molecular sieve containing Ti or Zr metal elements. When this catalyst is used in the isomerization reaction of n-butane, it achieves good performance at 100°C, atmospheric pressure, and a n-butane gas space velocity of 800 h⁻¹. -1 Under the specified conditions, the conversion rate of n-butane is 35%, and the selectivity of isobutane is 78%. CN101745407A discloses a solid superacid catalyst and its preparation method, in which zirconium hydroxide is reacted with SO42-. 2- The catalyst is prepared by impregnation with a solution, drying, mixing with silica sol, extruding and molding, calcining, and then impregnating with a group VIII metal. CN110385142A discloses a catalyst for the isobutane n-assembly reaction, which uses MCM-41 molecular sieve as support and Pt / SO4 as the substrate. 2- Although the reaction conditions were relatively mild, the conversion of isobutane was not ideal, even with a selectivity of over 90% for n-butane. The conversion rate of isobutane did not exceed 21%, and the yield of n-butane was below 22.1%.

[0004] Existing zirconium sulfate-type solid superacid catalysts are typically used solely for isomerization or normalization, with no reports of their simultaneous application in both reactions. Furthermore, when these catalysts are used for isomerization or normalization reactions, it is difficult to simultaneously achieve optimal reaction conversion and target product selectivity. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of existing technologies, such as the lack of bifunctional catalysts for normal isomerization, insufficient normal isomerization activity, and difficulty in achieving both conversion and selectivity. This invention provides an alkane normal isomerization catalyst, its preparation method, and its application. This catalyst exhibits good catalytic activity and selectivity in the normal isomerization reaction of light hydrocarbons.

[0006] To achieve the above objectives, the present invention provides an alkane normal isomerization catalyst, wherein the catalyst comprises an acidic active component SO4. 2- / ZrO2, all-silica molecular sieves with MFI structure and alumina;

[0007] The mass ratio of the acidic active component (calculated as ZrO2) to the mass ratio of the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1).

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned alkane normal isomerization catalyst, the method comprising:

[0009] (1) Mix all-silica molecular sieve with MFI structure and zirconium hydroxide to obtain a mixture;

[0010] The mass ratio of the zirconium hydroxide (calculated as ZrO2) to the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1).

[0011] (2) Contact the mixture with a solution containing sulfate ions;

[0012] (3) The product obtained in step (2), the alumina precursor and the optional adhesive solvent are mixed and then shaped and calcined.

[0013] A third aspect of the present invention provides the application of the above-mentioned alkane normal isomerization catalyst in the normal isomerization reaction of light alkane.

[0014] The catalyst provided by this invention includes the acidic active component SO4. 2- The catalyst uses ZrO2, an MFI-structured all-silica molecular sieve, and alumina to modulate the acid centers of the catalyst. Without changing the active phase structure and acid strength, the distribution of acid centers is optimized, increasing the proportion of unimolecular reactions and decreasing the proportion of bimolecular reactions during the normal isomerization reaction. This results in the catalyst exhibiting good activity and selectivity in the normal isomerization reaction of light alkanes. Attached Figure Description

[0015] Figure 1These are the XRD spectra of the all-silica MFI molecular sieve, silica, MCM-41 molecular sieve, and ZSM-5 molecular sieve used in the embodiments and comparative examples of this invention.

[0016] Figure 2 These are the XRD patterns of the catalysts prepared in Examples 1-3 and Comparative Example 1 of this invention. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of this invention provides an alkane normal isomerization catalyst, the catalyst comprising an acidic active component SO4. 2- / ZrO2, all-silica molecular sieves with MFI structure and alumina;

[0019] The mass ratio of the acidic active component (calculated as ZrO2) to the mass ratio of the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1).

[0020] Phase analysis of the catalyst samples was performed using a Rigaku D / MAX-3A XRD instrument. The analytical conditions were: CuKα target as the X-ray source, Ni filter, scanning range of 5°-70°, and step size of 0.02°.

[0021] In existing solid acid catalyst systems, molecular sieves are typically used as supports, and the molecular sieves used as supports account for a high content in the catalyst; at the same time, the silica-alumina molecular sieves introduced into the catalyst are also usually used to provide additional acidic active centers.

[0022] The inventors of this invention discovered that a small amount of all-silica molecular sieves with an MFI structure and alumina can modulate the distribution of strong acid centers in solid acid catalysts, thereby enabling the catalysts to exhibit both high activity and high selectivity in normal isomerization reactions. This is likely due, on the one hand, to the fact that the MFI-structured all-silica molecular sieves are essentially non-acidic and possess excellent thermal stability, preventing the introduction of new acid centers. Simultaneously, optimizing the distribution of strong acid centers in zirconium sulfate facilitates the efficient activation and conversion of alkane molecules via a single-molecule pathway. On the other hand, the unique pore structure of the MFI-structured all-silica molecular sieves promotes the diffusion of reactants and products, effectively preventing secondary reactions.

[0023] According to some preferred embodiments of the present invention, in the catalyst, the mass ratio of the acidic active component (calculated as ZrO2) to the mass ratio of the all-silica molecular sieve (calculated as SiO2) is 1:(0.15-0.5), for example, it can be a typical but not limited mass ratio such as 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, etc.

[0024] According to some preferred embodiments of the present invention, the catalyst comprises zirconium, silicon, aluminum, and sulfur, respectively calculated as zirconium oxide, silicon oxide, aluminum oxide, and SO3. Based on the total mass of the catalyst, the content of zirconium oxide is 30-90 wt%, the content of silicon oxide is 1-35 wt%, the content of aluminum oxide is 5-50 wt%, and the content of SO3 is 1-10 wt%. Preferably, based on the total mass of the catalyst, the content of zirconium oxide is 50-80 wt%, the content of silicon oxide is 5-30 wt%, the content of aluminum oxide is 5-30 wt%, and the content of SO3 is 2-8 wt%. With the above preferred composition, it is beneficial to improve the thermal stability and specific surface area of ​​tetragonal zirconium oxide, thereby giving the catalyst a suitable distribution of strong acid centers and accessibility of active centers, further improving the catalytic activity of the catalyst.

[0025] Preferably, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, more preferably (0.03-0.08):1.

[0026] In this invention, the catalyst composition is characterized and analyzed using an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer. Based on the intensity of the elements present in the sample obtained by scanning and the pure substance sensitivity of these elements in the instrument, the content of each element in the sample is obtained through theoretical calculation and mathematical correction.

[0027] In this invention, the specific surface area of ​​the catalyst was characterized by the low-temperature nitrogen static capacity adsorption method (BET method). The instrument used was an ASAP2400 specific surface area analyzer manufactured by Micromeritics Instruments. The pretreatment conditions were: 250℃, 1.3Pa, treatment for 4h. The specific surface area was calculated using the BET formula.

[0028] In this invention, the density of the strong acid centers is the ratio of the amount of strong acid in the catalyst to its specific surface area. The method for testing the amount of strong acid in the catalyst includes using a Nicolet 6700 Fourier transform infrared spectrometer (4 cm⁻¹) manufactured by Thermo Fisher Scientific, USA. -1The sample was scanned 64 times. The sample was pressed into a self-supporting sheet with a diameter of 13 mm and then calcined at high temperature in a muffle furnace. After calcination, it was directly transferred to a desiccator for cooling at high temperature. After cooling to room temperature, it was placed in a self-made quartz infrared sample cell. It was first treated at 400℃ for 2 hours under normal pressure and flowing air, then cooled to 200℃ and vacuum purified for 4 hours. Finally, it was cooled to -190℃ with liquid nitrogen and saturated with purified CO probe molecules for 0.5 hours before desorption. The infrared spectrum of CO adsorption was obtained by subtracting the spectra before and after adsorption. The wavelength range was 2050-2250 cm⁻¹. -1 The spectrum at that location was processed to separate peaks, resulting in four absorption peaks with wavenumbers of 2186 cm⁻¹. -1 2167cm -1 2150cm -1 and 2125cm -1 The wave number is 2167 cm⁻¹. -1 The absorption peak at that point is the strong acid center, which is directly related to the catalyst performance. The amount of strong acid N (in μmol / g) can be calculated according to equation (1).

[0029] N = A / (ρA0), Equation (1),

[0030] Where A is the integral area of ​​the absorption peak (in cm²). -1 ρ is the mass of the catalyst support per square centimeter (in g / cm³). 2 A0 is the molar extinction coefficient for a wavenumber of 2167 cm⁻¹. -1 The spectral peak, A0 = 2.6 cm / μmol.

[0031] The catalyst provided by this invention has a suitable density of strong acid centers, while the density of strong acid centers in the super-strong solid acid zirconium sulfate in the prior art is relatively high, generally higher than 2 μmol / m³. 2 The inventors of this invention discovered in their research that an excessively high density of strong acid centers may affect the selectivity of the normal isomerization catalyst.

[0032] The inventors of this invention discovered in their research that the presence of strong acid sites with suitable density and uniform strength in the catalyst is beneficial for reactant molecules to be efficiently activated and transformed through a single molecular pathway, thereby enabling the catalyst to exhibit both high activity and high selectivity in the normal isomerization reaction.

[0033] According to some preferred embodiments of the present invention, the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 Preferably, it is 0.5-1.5 μmol / m 2 For example, it can be 0.5 μmol / m 2 0.6 μmol / m 2 0.7 μmol / m2 0.8 μmol / m 2 0.9 μmol / m 2 1 μmol / m 2 1.1 μmol / m 2 1.2 μmol / m 2 1.3 μmol / m 2 1.4 μmol / m 2 1.5 μmol / m 2 Typical, but not limiting, density values ​​are used. Under the preferred conditions described above, it is beneficial to further improve the activity and selectivity of the catalyst in the normal isomerization reaction.

[0034] According to some preferred embodiments of the present invention, the catalyst has a specific surface area of ​​80-180 m². 2 / g, preferably 90-160m 2 / g, more preferably 100-150m 2 / g.

[0035] According to some preferred embodiments of the present invention, the alumina is γ-Al₂O₃. In the above preferred embodiments, it is beneficial to improve the thermal stability and specific surface area of ​​the catalyst, thereby improving the catalytic activity of the catalyst.

[0036] In this invention, there is no particular limitation on the shape of the catalyst, and those skilled in the art can select it according to actual needs. For example, it can be in the form of strips, small spheres, flakes, particles, or microspheres to suit fixed bed, moving bed, or fluidized bed reactions.

[0037] A second aspect of the present invention provides a method for preparing the above-mentioned alkane normal isomerization catalyst, the method comprising:

[0038] (1) Mix all-silica molecular sieve with MFI structure and zirconium hydroxide to obtain a mixture;

[0039] The mass ratio of the zirconium hydroxide (calculated as ZrO2) to the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1).

[0040] (2) Contact the mixture with a solution containing sulfate ions;

[0041] (3) The product obtained in step (2), the alumina precursor and the optional adhesive solvent are mixed and then shaped and calcined.

[0042] According to the present invention, the above preparation method enables the all-silica molecular sieve with MFI structure to be uniformly distributed in the catalyst without clogging the catalyst pores. Without introducing new acid centers, the density of strong acid centers in zirconium sulfate is reduced. The presence of strong acid sites with suitable density and uniform strength is conducive to the efficient activation and transformation of reactant molecules through a single molecular pathway, thereby enabling the catalyst to exhibit both high activity and high selectivity in the normal isomerization reaction.

[0043] The present invention offers a wide range of options for the number and structure of pores in the all-silica molecular sieve. Any all-silica molecular sieve with an MFI structure can be applied to the present invention.

[0044] In some preferred embodiments, the specific surface area of ​​the all-silica molecular sieve is 400-500 m². 2 / g, preferably 420-460m 2 / g. Under the above-mentioned preferred conditions, it is beneficial to further optimize the density of strong acid centers in zirconium sulfate, improve the uniformity of strong acid sites, and thus enhance the positive isomerization activity.

[0045] According to some preferred embodiments of the present invention, the mass ratio of the zirconium hydroxide, based on the mass of ZrO2, to the all-silica molecular sieve, based on the mass of SiO2, is 1:(0.15-0.5).

[0046] In this invention, an acidic active component is formed by contacting the mixture with a sulfate-containing solution in step (2). This contact can be performed in a manner conventional in the art, for example, by impregnating the mixture with a sulfate-containing solution.

[0047] The present invention does not impose any particular limitation on the specific operating conditions of the contact, as long as the catalyst composition range described above can be met. Those skilled in the art can make selections according to actual needs.

[0048] According to some preferred embodiments of the present invention, the contact temperature is 20-80°C, preferably 25-60°C; the contact time is 1-10h, preferably 2-5h.

[0049] The present invention has a wide range of choices for the specific types of solutions containing sulfate ions. Preferably, the solutions containing sulfate ions are selected from aqueous solutions of at least one of sulfuric acid, ammonium sulfate, and ammonium bisulfate.

[0050] Preferably, the sulfate concentration in the sulfate-containing solution is 1-10 wt%, more preferably 2-8 wt%. Using the above-mentioned preferred embodiments is beneficial for obtaining suitable SO3 content and strong acid center density.

[0051] The present invention does not impose a particular limitation on the amount of the sulfate-containing solution used, as long as it meets the SO3 content range requirement of the catalyst described in the first aspect. Those skilled in the art can select the appropriate amount based on actual needs. Preferably, the mass ratio of the sulfate-containing solution to the mixture is 0.3-5:1, more preferably 0.5-3:1.

[0052] In this invention, step (2) includes, optionally, a drying and grinding step after the contact. The drying temperature can be 50-150°C, and the drying time can be 3-100 hours. The grinding is used to grind the dried solid into a powder of 100-300 mesh, which, in the preferred embodiment described above, helps to improve the crushing strength of the catalyst.

[0053] In this invention, the alumina precursor refers to a substance that can be calcined to obtain alumina, as is well known to those skilled in the art. Preferably, the alumina precursor is boehmite and / or gibbsite, with boehmite being more preferred. Using the above-mentioned preferred alumina precursor, calcination can form γ-Al₂O₃, which is beneficial for improving the thermal stability and crushing strength of the catalyst.

[0054] In this invention, the molding process described in step (3) can be carried out using conventional methods and conditions in the art. This invention does not impose any particular limitation on this process. The molding method can be selected according to actual application needs, for example, it can be selected from any one of extrusion molding, granulation molding, ball forming, and spray drying to form balls, with extrusion molding being preferred. Under the above preferred conditions, it is more suitable for fixed-bed reactors.

[0055] According to some preferred embodiments of the present invention, the ratio of the total mass of the adhesive solvent to the product obtained in step (2) and the alumina precursor is 0.3-1:1, preferably 0.4-0.8:1.

[0056] According to some preferred embodiments of the present invention, the colloidal solvent is an aqueous solution of an acid, preferably an aqueous solution selected from at least one of nitric acid, acetic acid, citric acid, oxalic acid and formic acid.

[0057] Preferably, the concentration of acid in the adhesive solvent is 2-10 wt%.

[0058] According to some preferred embodiments of the present invention, in step (3), the calcination temperature is 600-850℃, preferably 650-850℃, and the calcination time is 1-20h, preferably 3-12h. Under the above-mentioned preferred calcination temperature conditions, it is beneficial to form strong acid centers with suitable density, which in turn is beneficial to improve the activity and selectivity of the catalyst in the butane normal isomerization reaction.

[0059] In this invention, a drying process may be included before the roasting in step (3). Preferably, the drying temperature is 80-140℃, more preferably 100-130℃, and the drying time is 5-30h, more preferably 8-24h.

[0060] A third aspect of the present invention provides the application of the above-mentioned alkane normal isomerization catalyst in the normal isomerization reaction of light alkane.

[0061] Preferably, the light alkane isomerization reaction includes C5 / C6 isomerization, n-butane isomerization, and isobutane isomerization.

[0062] Preferably, the light alkane normal isomerization reaction is carried out in a fixed-bed reactor.

[0063] The present invention will be described in detail below through embodiments.

[0064] The bulk structure of the molecular sieve and catalyst was analyzed and detected using a Rigaku D / MAX-3A XRD instrument. The analysis conditions were: CuKα target as the X-ray source, Ni filter, scanning range of 5°-70°, and step width of 0.02°.

[0065] The molecular sieve and catalyst composition were characterized and analyzed using an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer. Based on the intensity of the elements present in the sample obtained from the scanning and the pure substance sensitivity of these elements in the instrument, the content of each element in the sample was obtained through theoretical calculation and mathematical correction.

[0066] The zirconium hydroxide powder used was purchased from Changling Catalyst Company, with a zirconium oxide content of 78.5% by weight.

[0067] The all-silica MFI molecular sieve Si-1 used was purchased from Changling Catalyst Co., Ltd., with a silica content of 99.7% by mass and a specific surface area of ​​444.6 m². 2 / g, XRD characterization as follows Figure 1 As shown.

[0068] The boehmite powder was purchased from Sasol GmbH, Germany, with an alumina content of 75% by mass.

[0069] Example 1

[0070] Take 38.2g of zirconium hydroxide powder and 4.4g of all-silica MFI molecular sieve Si-1 and mix them evenly. Add 48.0g of sulfuric acid aqueous solution with a concentration of 5% by mass and impregnate at 40℃ for 4h. Then dry the impregnated solid at 60℃ for 12h and at 120℃ for 12h.

[0071] The dried solid was ground into a fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 14.4 g of pseudoboehmite powder. A 5.0% (w / w) nitric acid aqueous solution was added for peptization, with the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1. After thorough mixing, the mixture was extruded into strips, and the wet strips were dried at 120℃ for 10 h and calcined at 680℃ for 4 h to obtain catalyst A1. The XRD characterization results of catalyst A1 are shown below. Figure 2 ,Depend on Figure 2 Characteristic peaks of all-silica MFI molecular sieves are visible in the image; the composition and physicochemical properties of the catalyst are shown in Table 1 and Table 1 (continued).

[0072] Example 2

[0073] Take 38.2g of zirconium hydroxide powder and 7.8g of all-silica MFI molecular sieve, mix them evenly, add 48.0g of sulfuric acid aqueous solution with a concentration of 5% by mass, and impregnate at 40℃ for 4h. Then, dry the impregnated solid at 60℃ for 12h and at 120℃ for 12h.

[0074] The dried solid was ground into a fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 10.6 g of pseudoboehmite powder. A 5.0% (w / w) nitric acid aqueous solution was added for peptization, with the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.5:1. After thorough mixing, the mixture was extruded into strips, and the wet strips were dried at 120℃ for 10 h and calcined at 680℃ for 4 h to obtain catalyst A2. The XRD characterization results of catalyst A2 are shown below. Figure 2 The composition and physicochemical properties are shown in Table 1 and Table 1 (continued).

[0075] Example 3

[0076] Take 38.2g of zirconium hydroxide powder and 14.3g of all-silica MFI molecular sieve, mix them evenly, add 48.0g of sulfuric acid aqueous solution with a concentration of 5% by mass, and impregnate at 40℃ for 4h. Then, dry the impregnated solid at 60℃ for 12h and at 120℃ for 12h.

[0077] The dried solid was ground into a fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 3.4 g of pseudoboehmite powder. A 5.0% (w / w) nitric acid aqueous solution was added for peptization, with the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.7:1. After thorough mixing, the mixture was extruded into strips, and the wet strips were dried at 120℃ for 10 h and calcined at 680℃ for 4 h to obtain catalyst A3. The XRD characterization results of catalyst A3 are shown below. Figure 2 The composition and physicochemical properties are shown in Table 1 and Table 1 (continued).

[0078] Example 4

[0079] The method was followed in Example 2, except that 21 g of the all-silica MFI molecular sieve Si-1 was used. The resulting catalyst was designated A4, and its composition and physicochemical properties are shown in Table 1 and Table 1 (continued).

[0080] Example 5

[0081] Take 38.2g of zirconium hydroxide powder, add 48.0g of 5% sulfuric acid aqueous solution, and impregnate at 40℃ for 4h. Then, dry the impregnated solid at 60℃ for 12h and at 120℃ for 12h.

[0082] The dried solid was ground into a fine powder and passed through a 100-300 mesh sieve. 7.8 g of all-silica MFI molecular sieve and 10.6 g of pseudoboehmite powder were added and mixed thoroughly. A 5.0% by mass nitric acid aqueous solution was then added to dissolve the mixture. The mass ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor was 0.6:1. After thorough mixing, the mixture was extruded into strips. The wet strips were dried at 120℃ for 10 h and calcined at 680℃ for 4 h to obtain catalyst A5. The composition and physicochemical properties of A5 are shown in Table 1 and Table 1 (continued).

[0083] Example 6

[0084] Take 38.2g of zirconium hydroxide powder and 6.0g of all-silica MFI molecular sieve Si-1, mix them evenly, add 48.0g of sulfuric acid aqueous solution with a concentration of 3% by mass, impregnate at 40℃ for 4h, and dry the impregnated solid at 60℃ for 12h and 120℃ for 12h.

[0085] The dried solid was ground into a fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 38.3g of pseudoboehmite powder. A 5.0% by mass nitric acid aqueous solution was added for gelation, with the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1. After thorough mixing, the mixture was extruded into strips, and the wet strips were dried at 120℃ for 10h and calcined at 630℃ for 4h to obtain catalyst A6. The composition and physicochemical properties of catalyst A6 are shown in Table 1 and Table 1 (continued).

[0086] Comparative Example 1

[0087] Take 38.2g of zirconium hydroxide powder, add 48.0g of 5% sulfuric acid aqueous solution, and impregnate at 40℃ for 4h. Then, dry the impregnated solid at 60℃ for 12h and at 120℃ for 12h.

[0088] The dried solid was ground into a fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 16.6 g of pseudoboehmite powder. A 5.0% (w / w) nitric acid aqueous solution was added for peptization, with the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1. After thorough mixing, the mixture was extruded into strips, and the wet strips were dried at 120℃ for 10 h and calcined at 680℃ for 4 h to obtain catalyst DA1. The XRD characterization results of catalyst DA1 are shown below. Figure 2 As can be seen, catalyst DA1 does not contain the characteristic peaks of Si-1 in the all-silica MFI molecular sieve. The composition and physicochemical properties of catalyst DA1 are shown in Table 1 and Table 1 (continued).

[0089] Comparative Example 2

[0090] Take 38.2g of zirconium hydroxide powder and 18.0g of all-silica MFI molecular sieve, mix them evenly, add 48.0g of sulfuric acid aqueous solution with a concentration of 5% by mass, and impregnate at 40℃ for 4h. Then, dry the impregnated solid at 60℃ for 12h and at 120℃ for 12h.

[0091] The dried solid was ground into a fine powder, passed through a 100-300 mesh sieve, and dissolved in a 5.0% by mass nitric acid aqueous solution. The mass ratio of the nitric acid aqueous solution to the fine powder was 0.6:1. After mixing evenly, the mixture was extruded into strips. The wet strips were dried at 120℃ for 10 h and calcined at 680℃ for 4 h to obtain catalyst DA2. The composition and physicochemical properties of catalyst DA2 are shown in Table 1 and Table 1 (continued).

[0092] Comparative Example 3

[0093] The method was followed in Example 2, except that an equal mass of silica Si-2 (produced by Changling Catalyst Co., Ltd., with a silica content of 99.9% by mass) was used; XRD characterization is shown in [reference needed]. Figure 1 Replace the all-silicon MFI molecular sieve Si-1.

[0094] The obtained catalyst is designated as catalyst DA3. The composition and physicochemical properties of catalyst DA3 are shown in Table 1 and Table 1 (continued).

[0095] Comparative Example 4

[0096] The method was followed in Example 2, except that an equal mass of MCM-41 molecular sieve (denoted as Si-3, produced by Changling Catalyst Co., Ltd., with a silica content of 99.7% by mass) was used; XRD characterization is shown below. Figure 1 Replace the all-silica MFI molecular sieve.

[0097] The composition and physicochemical properties of the prepared catalyst, denoted as catalyst DA4, are shown in Table 1 and Table 1 (continued).

[0098] Comparative Example 5

[0099] The method was the same as in Example 2, except that an equal mass of ZSM-5 molecular sieve (denoted as Si-4, produced by Changling Catalyst Co., Ltd., with a silica / alumina molar ratio of 65) was used. XRD characterization is shown in [reference needed]. Figure 1 Replace the all-silicon MFI molecular sieve Si-1.

[0100] The composition and physicochemical properties of the prepared catalyst, denoted as catalyst DA5, are shown in Table 1 and Table 1 (continued).

[0101] Table 1

[0102]

[0103] Continued from Table 1

[0104]

[0105] Test Example 1

[0106] The following test examples are used to examine the isomerization reaction performance of the catalyst.

[0107] Using n-butane with a purity >99.8% by mass as the reactant, the catalysts prepared in the above examples and comparative examples were evaluated for activity in a small fixed-bed reactor. The evaluation conditions were: 245°C, 1.8 MPa, and a feed mass hourly space velocity of 2.5 hr. -1 The hydrogen / hydrocarbon molar ratio was 1.0, and the evaluation results after 10 h of reaction are listed in Table 2.

[0108] n-Butane conversion rate (%) = ((mass of n-butane in feed - mass of n-butane in product) / mass of n-butane in feed) × 100%;

[0109] Isobutane selectivity (%) = (mass of isobutane in product / (mass of n-butane in feed - mass of n-butane in product)) × 100%.

[0110] Table 2

[0111] Catalyst number n-Butane conversion, mass % Isobutane selectivity, mass % A1 41.91 82.91 A2 40.96 84.04 A3 40.64 84.45 A4 39.98 83.41 A5 42.32 79.65 A6 38.98 82.00 DA1 40.45 77.81 DA2 28.67 80.00 DA3 34.89 79.63 DA4 34.46 80.44 DA5 40.89 71.30

[0112] Test Example 2

[0113] This test example is used to examine the ortho-configuration reaction performance of the catalyst.

[0114] Using isobutane with a purity >99.8% by mass as the reactant, the activity of the catalyst of this invention and the comparative catalyst was evaluated in a small fixed-bed reactor. The evaluation conditions were: 255°C, 1.8 MPa, and a feed mass hourly space velocity of 2.5 hr. -1 The hydrogen / hydrocarbon molar ratio was 1.0, and the evaluation results after 10 h of reaction are listed in Table 3.

[0115] Wherein, isobutane conversion rate (%) = ((mass of isobutane in feed - mass of isobutane in product) / mass of isobutane in feed) × 100%;

[0116] n-Butane selectivity (%) = (mass of n-butane in product / (mass of isobutane in feed - mass of isobutane in product)) × 100%.

[0117] Table 3

[0118]

[0119]

[0120] As can be seen from Tables 2 and 3, the catalyst provided by the present invention has a suitable density of strong acid centers compared with the comparative catalyst, and can take into account both excellent activity and selectivity in the normal isomerization reaction of light alkanes.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An alkane normal isomerization catalyst, characterized in that, The catalyst includes the acidic active component SO4. 2- / ZrO2, all-silica molecular sieves with MFI structure and alumina; The mass ratio of the acidic active component (calculated as ZrO2) to the mass ratio of the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1). The catalyst comprises zirconium, silicon, aluminum, and sulfur, respectively, calculated as zirconium oxide, silicon oxide, aluminum oxide, and SO3. Based on the total mass of the catalyst, the content of zirconium oxide is 30-90 wt%, the content of silicon oxide is 1-35 wt%, the content of aluminum oxide is 5-50 wt%, and the content of SO3 is 1-10 wt%. In the catalyst, the density of strong acid centers is 0.29-1.71 μmol / m³. 2 .

2. The catalyst according to claim 1, wherein, In the catalyst, the mass ratio of the acidic active component (calculated as ZrO2) to the mass ratio of the all-silica molecular sieve (calculated as SiO2) is 1:(0.15-0.5).

3. The catalyst according to claim 1, wherein, Based on the total mass of the catalyst, the content of zirconium oxide is 50-80 wt%, the content of silicon oxide is 5-30 wt%, the content of aluminum oxide is 5-30 wt%, and the content of SO3 is 2-8 wt%.

4. The catalyst according to claim 1, wherein, The mass ratio of SO3 to ZrO2 is (0.02-0.12):

1.

5. The catalyst according to claim 4, wherein, The mass ratio of SO3 to ZrO2 is (0.03-0.08):

1.

6. The catalyst according to any one of claims 1-5, wherein, The catalyst has a specific surface area of ​​80-180 m². 2 / g.

7. The catalyst according to any one of claims 1-5, wherein, The alumina is γ-Al2O3.

8. A method for preparing the alkane normal isomerization catalyst according to any one of claims 1-7, the preparation method comprising: (1) Mix all-silica molecular sieves with MFI structure and zirconium hydroxide to obtain a mixture; The mass ratio of the zirconium hydroxide (calculated as ZrO2) to the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1). (2) Contact the mixture with a solution containing sulfate ions; (3) The product obtained in step (2), the alumina precursor and the optional adhesive solvent are mixed and then shaped and calcined.

9. The preparation method according to claim 8, wherein, The specific surface area of ​​the all-silica molecular sieve is 400-500 m². 2 / g.

10. The preparation method according to claim 8, wherein, The mass ratio of the zirconium hydroxide, calculated as ZrO2, to the all-silica molecular sieve, calculated as SiO2, is 1:(0.15-0.5).

11. The preparation method according to claim 8, wherein, The contact temperature is 20-80℃; the contact time is 1-10h.

12. The preparation method according to claim 11, wherein, The contact temperature is 25-60℃; the contact time is 2-5 hours.

13. The preparation method according to claim 8, wherein, The sulfate-containing solution is selected from an aqueous solution of at least one of sulfuric acid, ammonium sulfate, and ammonium bisulfate.

14. The preparation method according to claim 8, wherein, The sulfate concentration in the solution containing sulfate is 1-10 wt%.

15. The preparation method according to claim 14, wherein, The sulfate concentration in the solution containing sulfate is 2-8 wt%.

16. The preparation method according to claim 8, wherein, The mass ratio of the sulfate-containing solution to the mixture is 0.3-5:

1.

17. The preparation method according to claim 16, wherein, The mass ratio of the sulfate-containing solution to the mixture is 0.5-3:

1.

18. The preparation method according to any one of claims 8-17, wherein, The alumina precursor is boehmite and / or gibbsite.

19. The preparation method according to claim 18, wherein, The alumina precursor is boehmite.

20. The preparation method according to any one of claims 8-17, wherein, The ratio of the total mass of the adhesive solvent to the product obtained in step (2) and the alumina precursor is 0.3-1:

1.

21. The preparation method according to any one of claims 8-17, wherein, The solvent is an aqueous solution of acid.

22. The preparation method according to claim 21, wherein, The colloidal solvent is selected from an aqueous solution of at least one of nitric acid, acetic acid, citric acid, oxalic acid and formic acid.

23. The preparation method according to any one of claims 8-17, wherein, The forming method is selected from any one of extrusion forming, granulation forming, ball forming, and spray drying forming.

24. The preparation method according to claim 23, wherein, The forming method is extrusion forming.

25. The preparation method according to any one of claims 8-17, wherein, In step (3), the roasting temperature is 600-850℃ and the roasting time is 1-20h.

26. The preparation method according to claim 25, wherein, In step (3), the roasting temperature is 650-850℃ and the roasting time is 3-12h.

27. The application of the alkane normal isomerization catalyst according to any one of claims 1-7 in the normal isomerization reaction of light alkane.

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