Normal isomerization catalyst, process for its preparation and use

Abstract

The application relates to the technical field of catalysts, and discloses a normal-isomerization catalyst as well as a preparation method and application thereof; the catalyst comprises an active substrate and an active metal component loaded on the active substrate; the active substrate comprises an acid active component SO4 2‑ / ZrO2, a full-silica molecular sieve with an MFI structure and aluminum oxide; the active metal component is selected from at least one of noble metal elements; in the catalyst, the density of strong acid centers is 0.1-1 mu mol / m 2 The catalyst has a suitable density of strong acid centers, high isomerization activity and normal isomerization activity, can be applied to light hydrocarbon isomerization or normal isomerization of C4-C6, has high conversion rate and selectivity, and has good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a normal isomerization catalyst and a preparation method and application thereof. Background Art

[0002] Light alkane normal isomerization primarily includes C5 / C6 isomerization, n-butane isomerization, and isobutane normalization. C5 / C6 isomerization is used to produce C5 / C6 isomerized oil, which is essentially free of sulfur, olefins, and aromatics and is an important clean gasoline blending component. N-butane isomerization converts n-butane to isobutane, providing feedstock for processes such as butane-butene alkylation, isobutane-propylene co-oxidation (PO / MTBE), C3 / iC4 alkane dehydrogenation, and isobutane dehydrogenation. Isobutane normalization converts isobutane to n-butane, providing feedstock for processes such as steam cracking to produce ethylene and butane oxidation to produce maleic anhydride. Therefore, light alkane normal isomerization is a crucial supporting technology for upgrading oil quality, a key means of expanding feedstock sources for ethylene plants, and a key unit technology for processes such as n-butane oxidation to produce maleic anhydride, C3 / C4 alkane dehydrogenation, isobutane dehydrogenation, and PO / MTBE. Efficient catalysts for the normal isomerization of light alkanes are at the heart of normal isomerization technology. Traditional catalysts for the normal isomerization of light alkanes fall into two categories: Pt-containing chlorided alumina (Pt / Al2O3-Cl) and Pt- or Pd-loaded zeolite molecular sieves (Pt(Pd) / zeolite). Pt / Al2O3-Cl catalysts offer the advantages of low reaction temperature and high single-pass conversion, but they are sensitive to feedstock impurities, requiring rigorous raw material purification to remove impurities such as sulfur and water. During the isomerization reaction, continuous chlorine injection is required to maintain catalyst activity, and the catalyst is non-regenerative, further limiting the application of this technology. Pt(Pd) / zeolite catalysts have more relaxed requirements for feedstock impurities, but exhibit lower isomerization activity and selectivity.

[0003] Solid superacid catalysts are a new type of catalyst developed in recent years. Prior art reports have reported the use of inorganic acid-promoted zirconium-based solid superacid catalysts in light hydrocarbon isomerization reactions. CN107051420A discloses an n-butane isomerization catalyst and its preparation method. The catalyst uses nano-sized tetragonal zirconium oxide as a carrier, loaded with sulfate, molybdate, and precious metals. When used in the n-butane isomerization reaction, the catalyst reacts at 220°C, 2.0 MPa, and a feed mass space velocity of 2.0 h / min. -1Under the conditions of 1.2 hydrogen / hydrocarbon molecular ratio, the isomerization rate of n-butane is up to 39.7%. CN1164509A discloses a molecular sieve type super acid and its preparation method. The catalyst is a hydrogen-type ZSM-5, ZSM-11 or β molecular sieve containing Ti or Zr metal elements. When the catalyst is used for the n-butane isomerization reaction, at 100°C, normal pressure, and a n-butane gas space velocity of 800h -1 Under the conditions of , the conversion rate of n-butane is 35% and the selectivity of isobutane is 78%. CN101745407A discloses a solid super acid catalyst and its preparation method. The catalyst is zirconium hydroxide with SO4 2- The solid catalyst is prepared by impregnating a solution of 1% 2% 2% 3% 4% 5% 1% 2% 5% 1% 2% 3 ...

[0004] CN110385142A discloses a catalyst for isobutane normalization reaction, which uses MCM-41 molecular sieve as a carrier and Pt / SO4 2- / ZrO2 is the active component. Although the reaction conditions are relatively mild, the isobutane conversion effect is not ideal. Under the condition that the n-butane selectivity is higher than 90%, the isobutane conversion rate does not exceed 21%, and the n-butane yield is lower than 22.1%.

[0005] Sulfated zirconium oxide-based solid superacid catalysts disclosed in prior art are typically used solely for isomerization or normalization of light hydrocarbons, with no reports of their simultaneous application in both reactions. Furthermore, when used in either isomerization or normalization reactions, these catalysts struggle to achieve both high conversion and target product selectivity, and their stability is insufficient. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of insufficient activity and poor stability of normal isomerization catalysts in the prior art and to provide a normal isomerization catalyst having high light hydrocarbon normal isomerization activity and good stability.

[0007] In order to achieve the above object, the present invention provides a normal isomerization catalyst in one aspect, the catalyst comprising an active matrix and an active metal component supported on the active matrix;

[0008] Wherein, the active matrix includes the acidic active component SO4 2- / ZrO2, an all-silicon molecular sieve having an MFI structure, and alumina; the active metal component is selected from at least one of the noble metal elements;

[0009] Wherein, the density of the strong acid center in the catalyst is 0.1-1 μmol / m 2 .

[0010] Preferably, in the catalyst, the molar ratio of the strong acid to the weak acid is 4-8:1.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned n-isomerization catalyst, the preparation method comprising:

[0012] (1) mixing an all-silicon molecular sieve having an MFI structure and zirconium hydroxide to obtain a mixture;

[0013] (2) contacting the mixture with a solution containing sulfate;

[0014] (3) mixing the product obtained in step (2), an alumina precursor, and an optional peptizing agent, forming and calcining the mixture to obtain an active matrix;

[0015] (4) Loading active metal components on the active matrix.

[0016] The third aspect of the present invention provides use of the n-isomerization catalyst described in the first aspect or the n-isomerization catalyst prepared by the preparation method described in the second aspect in an isomerization reaction or a normalization reaction of C4-C6 light hydrocarbons.

[0017] The catalyst provided by the present invention comprises an active matrix and an active metal component, and the active component SO4 2- The catalyst utilizes a synergistic effect between the MFI-structured all-silicon molecular sieve and alumina to modulate the density of strong acid centers. This catalyst exhibits an optimal density of strong acid centers, along with high isomerization and normalization activities. Applications in the isomerization and normalization of C4-C6 light hydrocarbons demonstrate both high conversion and selectivity, with excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : XRD spectra of all-silicon MFI molecular sieve, white carbon black, MCM-41 molecular sieve and ZSM-5 molecular sieve used in the examples and comparative examples of the present invention;

[0019] Figure 2 1 is the XRD spectrum of the active matrix prepared in Examples 1-3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0020] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0021] A first aspect of the present invention provides a normal isomerization catalyst, comprising an active matrix and an active metal component supported on the active matrix;

[0022] Wherein, the active matrix includes the acidic active component SO4 2- / ZrO2, an all-silicon molecular sieve having an MFI structure, and alumina; the active metal component is selected from at least one of the noble metal elements;

[0023] Wherein, the density of the strong acid center in the catalyst is 0.1-1 μmol / m 2 .

[0024] The phase analysis of the catalyst samples was carried out using a Japanese Rigaku D / MAX-3A diffractometer (XRD) under the following analysis conditions: a CuKα target as the radiation source, a Ni filter, a scanning range of 5°-70°, and a step width of 0.02°.

[0025] In the solid acid catalyst system in the prior art, molecular sieves are usually used as carriers, and the molecular sieves used as carriers occupy a relatively 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.

[0026] The catalyst provided by the present invention has a suitable density of strong acid centers, while the density of strong acid centers in the super strong solid acid sulfate zirconium oxide in the prior art is relatively high, generally higher than 2 μmol / m 2 The inventors of the present invention have found in their research that an excessively high density of strong acid centers may be detrimental to the normal isomerization selectivity of the catalyst.

[0027] According to the present invention, a small amount of all-silicon molecular sieves and alumina having an MFI structure can play a role in modulating the distribution of strong acid centers of the solid acid catalyst, thereby making the catalyst have higher positive isomerization activity and selectivity. Furthermore, the noble metal component and the sulfated zirconium oxide in the active matrix act synergistically, and the stability of the catalyst can be improved through the combined action of strong acid centers and weak acid centers. The reason for this is that the all-silicon molecular sieves with an MFI structure have a special pore structure, are essentially acidic, and have excellent thermal stability, which helps to optimize the distribution of strong acid centers in the sulfated zirconium oxide, facilitates the efficient activation and conversion of light hydrocarbon molecules through a single molecule pathway, facilitates the diffusion of reactants and products, and effectively avoids the occurrence of secondary reactions.

[0028] According to some preferred embodiments of the present invention, the density of the strong acid center in the catalyst is 0.2-0.7 μmol / m 2 For example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 μmol / m 2 In the above preferred case, it is beneficial to further improve the activity and selectivity of the catalyst in the normal isomerization reaction of light hydrocarbons.

[0029] In the present invention, the density of the strong acid center is the ratio of the amount of strong acid in the catalyst to the specific surface area. The method for testing the amount of acid in the catalyst includes: using a Nicolet 6700 Fourier transform infrared spectrometer produced by Thermo Fisher, USA, with a resolution of 4 cm -1 , scanned 64 times. The sample was pressed into a self-supporting sheet with a diameter of 13 mm, and then placed in a muffle furnace for high-temperature calcination. After completion, it was directly transferred to a dryer for cooling at high temperature. After cooling to room temperature, it was placed in a homemade quartz infrared sample cell, first treated at 400 ° C for 2 hours under normal pressure flowing air, then cooled to 200 ° C, vacuum purified for 4 hours, and then cooled to -190 ° C with liquid nitrogen. The purified CO probe molecules were saturated and adsorbed for 0.5 hours before desorption. The spectra before and after adsorption were subtracted to obtain the infrared spectrum of CO adsorbed by the sample. For the wave number of 2050-2250cm -1 The spectrum at 2186cm is processed by peak separation. The spectrum can be divided into four absorption peaks with wave numbers of 2186cm -1 、2167cm -1 , 2150cm -1 and 2125cm -1 , where the wave number is 2167 cm -1 The absorption peak at 2150 cm is a strong acid center directly related to the catalyst performance. -1 The absorption peak at is the weak acid center of the catalyst. The acid amount N (in μmol / g) is calculated according to formula (1).

[0030] N=A / (ρA0), formula (1),

[0031] Where A is the integrated area of ​​the absorption peak (in cm -1 ), ρ is the mass of the catalyst support per square centimeter (in g / cm 2 ), A0 is the molar extinction coefficient, for a wave number of 2167 cm -1 and 2150cm -1 The spectral peak is A0=2.6cm / μmol.

[0032] In the present invention, the specific surface area of ​​the catalyst is characterized by the low-temperature nitrogen static volume adsorption method (BET method). The instrument used is the ASAP2400 specific surface meter produced by Micromeritics Instruments. The pretreatment conditions are: 250°C, 1.3 Pa, and treatment for 4 hours. The specific surface area (m 2 / g).

[0033] According to some preferred embodiments of the present invention, the molar ratio of the strong acid to the weak acid in the catalyst is 4-8:1, for example, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, and other typical but non-limiting molar ratios. Preferably, the ratio is 4.5-6.8:1. These preferred ratios further enhance the stability of the catalyst.

[0034] According to some preferred embodiments of the present invention, based on the total mass of the catalyst, the content of the active matrix is ​​99-99.95wt%, preferably 99.5-99.9wt%; calculated as an element, the content of the active metal component is 0.05-1wt%, preferably 0.1-0.5wt%.

[0035] In the present invention, the content of the active metal component in the catalyst is determined using a Lambda 35 UV-Vis spectrophotometer or ICP-AES. When the catalyst contains only the active matrix and the active metal component, the sum of the active matrix and the active metal component is 100%.

[0036] According to some preferred embodiments of the present invention, the active metal component is selected from at least one of Pt, Pd, Ru and Rh, preferably Pt and / or Pd.

[0037] In the present invention, the active metal component exists in the form of oxide and / or metal. Preferably, at least part of the active metal component exists in the form of metal.

[0038] According to some preferred embodiments of the present application, the active matrix comprises zirconium element, silicon element, aluminum element and sulfur element, in terms of zirconia, silica, alumina and SO3, respectively, wherein the content of zirconia is 30-90wt%, the content of silica is 1-35wt%, the content of alumina is 5-50wt%, and the content of SO3 is 1-10wt%, based on the total mass of the active matrix; preferably, the content of zirconia is 50-80wt%, the content of silica is 5-30wt%, the content of alumina is 5-30wt%, and the content of SO3 is 2-8wt%, based on the total mass of the active matrix. With the above preferred composition, the thermal stability of tetragonal zirconia and the specific surface area of the catalyst can be improved, so that the catalyst has a suitable distribution of strong acid centers and accessible active centers, and the catalytic activity of the catalyst is further improved.

[0039] According to some preferred embodiments of the present application, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, preferably (0.03-0.08):1.

[0040] In the present application, the composition of the active matrix is characterized and analyzed by using an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer, and the content of each element in the sample is obtained by theoretical calculation and mathematical correction according to the intensity of the elements existing in the sample obtained by scanning and the sensitivity of the pure substances of these elements in the instrument.

[0041] According to some preferred embodiments of the present application, in the active matrix, the mass of the acidic active component calculated based on ZrO2 and the mass of the all-silica molecular sieve calculated based on SiO2 are in a ratio of 1:(0.1-1), preferably 1:(0.15-0.5).

[0042] In the present application, the shape of the catalyst is not particularly limited, and a person skilled in the art can select it according to actual needs. For example, it can be in the form of a strip, a small ball, a sheet, a particle or a microsphere, so as to be suitable for a fixed bed, a moving bed or a fluidized bed reaction.

[0043] The second aspect of the present application provides a preparation method of the above-mentioned normal-isomerization catalyst, which comprises:

[0044] (1) mixing an all-silica molecular sieve with MFI structure and zirconium hydroxide to obtain a mixture;

[0045] (2) contacting the mixture with a solution containing sulfate;

[0046] (3) mixing the product obtained in step (2), an alumina precursor and an optional peptizing agent, shaping, and calcining to obtain an active matrix;

[0047] (4) Loading active metal components on the active matrix.

[0048] According to the present invention, the preparation method can make the all-silicon molecular sieve with MFI structure uniformly distributed in the catalyst without blocking the catalyst pores. Without introducing new acid centers, the density of strong acid centers in sulfated zirconium oxide is reduced, and the presence of strong acid sites with appropriate density and uniform strength leads to higher normal isomerization activity and selectivity.

[0049] The present invention has a wide range of selection for the number of pores and the pore structure of the all-silicon molecular sieve, and any all-silicon molecular sieve having an MFI structure can be applied to the present invention.

[0050] In some preferred embodiments, the specific surface area of ​​the all-silicon molecular sieve is 400-500m 2 / g, preferably 420-460m 2 In the above preferred case, it is beneficial to further optimize the density of strong acid centers in sulfated zirconium oxide, improve the uniformity of strong acid sites in the catalyst, and thus improve the normal isomerization activity.

[0051] According to some preferred embodiments of the present invention, the mass ratio of the zirconium hydroxide calculated by the mass of ZrO2 to the all-silicon molecular sieve calculated by the mass of SiO2 is 1:(0.15-0.5).

[0052] In the present invention, the acidic active component is formed by contacting the mixture with a solution containing sulfate in step (2). The contact can be carried out in a conventional manner in the art, for example, the mixture can be impregnated with a solution containing sulfate.

[0053] The present invention does not particularly limit the specific operating conditions of the contact, as long as they can meet the catalyst composition range described above, and those skilled in the art can make selections based on actual needs.

[0054] According to some preferred embodiments of the present invention, the contact temperature is 20-80°C, preferably 25-60°C; and the contact time is 1-10 hours, preferably 2-5 hours.

[0055] The present invention has a wide range of selection for the specific type of the solution containing sulfate radicals. Preferably, the solution containing sulfate radicals is an aqueous solution selected from at least one of sulfuric acid, ammonium sulfate and ammonium bisulfate.

[0056] Preferably, the concentration of sulfate in the sulfate-containing solution is 1-10 wt %, preferably 2-8 wt %. The above preferred embodiment is advantageous for obtaining an appropriate SO 3 content and strong acid center density.

[0057] The present invention does not particularly limit the amount of the sulfate-containing solution used, as long as it meets the SO3 content range requirements of the catalyst described in the first aspect. Those skilled in the art can select the amount based on actual needs. Preferably, the mass ratio of the sulfate-containing solution to the mixture is 0.3-5:1, preferably 0.5-3:1.

[0058] In the present invention, step (2) further includes optional drying and grinding steps after the contacting. The drying temperature may be 50-150°C, and the drying time may be 3-100 hours. The grinding is used to grind the dried solid into a powder of 100-300 mesh. In the above preferred embodiment, this helps to improve the crushing strength of the catalyst.

[0059] In the present invention, the alumina precursor refers to a substance that can be calcined to produce alumina, and is well known to those skilled in the art. Preferably, the alumina precursor is pseudo-boehmite and / or gibbsite, preferably pseudo-boehmite. In this preferred embodiment, the thermal stability and crushing strength of the catalyst are improved.

[0060] In the present invention, the molding in step (3) can be performed using conventional methods and conditions in the art, and the present invention is not particularly limited thereto. The molding method can be selected according to actual application needs, for example, any one of extrusion molding, granulation molding, ball molding, and spray drying spherical molding can be selected, with extrusion molding being preferred. In the above preferred case, a fixed bed reactor is more suitable.

[0061] According to some preferred embodiments of the present invention, the total mass ratio of the peptizing agent to the product obtained in step (2) to the alumina precursor is 0.3-1:1, preferably 0.4-0.8:1.

[0062] According to some preferred embodiments of the present invention, the peptizing agent is an aqueous solution of an acid, preferably an aqueous solution of at least one selected from nitric acid, acetic acid, citric acid, oxalic acid and formic acid.

[0063] Preferably, the concentration of the acid in the peptizing agent is 2-10 wt %.

[0064] According to some preferred embodiments of the present invention, in step (3), the calcination temperature is 600-850°C, preferably 650-850°C, and the calcination time is 1-20 hours, preferably 3-12 hours. Under these preferred calcination temperature conditions, strong acid centers with an appropriate density are formed, thereby improving the activity and selectivity of the catalyst in the normal isomerization reaction of light hydrocarbons.

[0065] In the present invention, step (3) may further include a drying process before the calcination. Preferably, the drying temperature is 80-140°C, preferably 100-130°C, and the drying time is 5-30 hours, preferably 8-24 hours.

[0066] In the present invention, the active metal component can be loaded onto the active matrix using any conventional method in the art. Preferably, the method for loading the active metal component onto the active matrix comprises: impregnating the active matrix with a solution containing a soluble compound of the active metal, followed by drying and calcining.

[0067] The present invention allows for a wide range of choices for the soluble compound of the active metal, which may be an inorganic or organic salt of the active metal. When the active metal is Pt, the soluble compound of Pt is preferably at least one of chloroplatinic acid, platinum tetrachloride, ammonium chloroplatinate, and dinitrosodiamine platinum. When the active metal is Pd, the soluble compound of Pd may be, for example, palladium chloride.

[0068] In the present invention, the solution containing the soluble compound of the active metal is a solution obtained by dissolving the soluble compound of the active metal in a solvent. The present invention has no particular limitation on the type of solvent, as long as it can dissolve the soluble compound of the active metal, and can be, for example, water.

[0069] According to some preferred embodiments of the present invention, in order to more evenly load the soluble compound containing the active metal on the active matrix and further improve the stability of the catalyst, the solution further contains a competitive adsorbent. The competitive adsorbent is preferably at least one of sulfuric acid, nitric acid, and acetic acid, and more preferably nitric acid.

[0070] Preferably, the mass ratio of the competitive adsorbent to the soluble compound of the active metal is 1-20:1, preferably 2-10:1. This preferred embodiment facilitates uniform dispersion of the soluble compound containing the active metal within the active matrix, while effectively preventing the competitive adsorbent from damaging the structure of the active matrix, further improving the activity and stability of the catalyst.

[0071] The present invention does not particularly limit the amount of the solution containing the soluble active metal compound, as long as the amount of the active metal component meets the range described in the first aspect. Preferably, the mass ratio of the solution containing the soluble active metal compound to the active matrix is ​​0.4-1:1, preferably 0.5-0.8:1.

[0072] According to the present application, the product after impregnation is dried and calcined. The present application does not have special requirements for the specific conditions of the drying, and the drying conditions in the art can be used. Preferably, the temperature of the drying is 80-140℃, preferably 100-130℃, and the time of the drying is 5-30h, preferably 8-24h.

[0073] According to the present application, preferably, the temperature of the calcination is 450-650℃, preferably 480-600℃, and the time of the calcination is 1-10h, preferably 3-5h.

[0074] According to some preferred embodiments of the present application, the preparation method further comprises: reducing the product obtained in step (4) in the presence of hydrogen.

[0075] According to some preferred embodiments of the present application, the conditions of the reduction treatment comprise: temperature of 200-300℃, preferably 220-260℃, time of 1-10h, preferably 3-5h; and volume ratio of gas agent of 300-1500, preferably 500-1200.

[0076] The third aspect of the present application provides the use of the n-isomerization catalyst of the first aspect or the n-isomerization catalyst prepared by the preparation method of the second aspect in the isomerization reaction or n-formation reaction of C4-C6 light hydrocarbon.

[0077] The present application will be described in detail below through examples.

[0078] In the following examples, the bulk structure of the catalyst is analyzed and detected by a Japan Rigaku D / MAX-3A diffractometer (XRD) for the phase of the catalyst sample, and the analysis conditions are: ray source CuKα target, Ni filter, scanning range 5°-70°, step width 0.02°.

[0079] The Pt content of the catalyst is determined by a Lambda 35 ultraviolet-visible spectrophotometer, the sample is first dissolved with hydrochloric acid, then complexed with stannous chloride, and the Pt content is determined by colorimetry.

[0080] The Pd content of the catalyst is determined by ICP-AES, the sample is first nitrated with aqua regia, then diluted and constant volume, determined by atomic absorption spectrometry, and compared with the standard curve to determine the Pd content.

[0081] The composition of the active matrix is characterized and analyzed by an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer, according to the intensity of the elements existing in the sample obtained by scanning and the sensitivity of the pure substances of these elements in the instrument, the content of each element in the sample is obtained by theoretical calculation and mathematical correction.

[0082] The zirconium hydroxide powder used was purchased from Changling Catalyst Company, and the zirconium oxide content was 78.5% by weight.

[0083] The all-silicon MFI molecular sieve Si-1 was purchased from Changling Catalyst Company, with a silicon oxide content of 99.7% by mass and a specific surface area of ​​444.6 m 2 / g, XRD characterization Figure 1 shown.

[0084] Pseudo-boehmite powder was purchased from Sasol, Germany, with an alumina content of 75% by mass.

[0085] Example 1

[0086] (1) Take 38.2g of zirconium hydroxide powder and 4.4g of all-silicon MFI molecular sieve Si-1 and mix them evenly. Add 48.0g of 5% by mass sulfuric acid aqueous solution and soak at 40℃ for 4h. Dry the soaked solid at 60℃ for 12h and 120℃ for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 10.6g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution to dissolve it. The ratio of the total mass of nitric acid aqueous solution to the fine powder and alumina precursor is 0.6:1. After kneading evenly, extrude into strips. Dry the wet strips at 120℃ for 10h and calcine at 680℃ for 4h to obtain the active matrix SSiZA-1. The XRD characterization results of the active matrix SSiZA-1 are shown in Figure 2 ,Depend on Figure 2 The characteristic peaks of all-silicon MFI molecular sieve can be seen in the figure, and the composition is shown in Table 1.

[0087] (2) 10.0 g of the active matrix SSiZA-1 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid. The mixture was immersed at 25°C for 3 h. The immersed solid was dried at 120°C for 10 h and calcined at 550°C for 4 h to produce catalyst CAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0088] Example 2

[0089] (1) Take 38.2g of zirconium hydroxide powder and 7.8g of all-silicon MFI molecular sieve, mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40℃ for 4h, dry the impregnated solid at 60℃ for 12h and 120℃ for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 10.6g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution to dissolve, the ratio of the total mass of nitric acid aqueous solution to the fine powder and alumina precursor is 0.5:1, mix evenly and extrude into strips, dry the wet strips at 120℃ for 10h and calcine at 680℃ for 4h to obtain the active matrix SSiZA-2. XRD characterization results of active matrix SSiZA-2 are shown in Figure 2 The composition is shown in Table 1.

[0090] (2) 10.0 g of the active matrix SSiZA-2 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, impregnated at 25 °C for 3 h, and the impregnated solid was dried at 120 °C for 10 h and calcined at 550 °C for 4 h to prepare a catalyst CAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0091] Example 3

[0092] (1) 38.2 g of zirconium hydroxide powder and 14.3 g of the all-silica MFI molecular sieve Si-1 were mixed uniformly, 48.0 g of a 5 mass% sulfuric acid aqueous solution was added, impregnated at 40 °C for 4 h, and the impregnated solid was dried at 60 °C for 12 h and at 120 °C for 12 h. The dried solid was ground into fine powder, 3.4 g of pseudo-boehmite powder was mixed uniformly, a 5.0 mass% nitric acid aqueous solution was added for peptization, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the aluminum oxide precursor was 0.7:1, uniformly kneaded, and then extruded into a strip, the wet strip was dried at 120 °C for 10 h and calcined at 680 °C for 4 h to prepare an active matrix SSiZA-3. The XRD characterization results of the active matrix SSiZA-3 are shown in Table 1. Figure 2 The characteristic peaks of the all-silica MFI molecular sieve can be seen in Table 1. Figure 2

[0093] (2) 10.0 g of the active matrix SSiZA-1 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, impregnated at 25 °C for 3 h, and the impregnated solid was dried at 120 °C for 10 h and calcined at 550 °C for 4 h to prepare a catalyst CAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0094] Example 4

[0095] According to the method of Example 1, except that 10 g of the active matrix SSiZA-1 was added to 5.0 g of an aqueous solution containing 0.0416 g of palladium chloride and 0.1 g of nitric acid, impregnated at 25 °C for 3 h, and the impregnated solid was dried at 120 °C for 10 h and calcined at 550 °C for 4 h to prepare a catalyst CAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0096] Example 5

[0097] (1) 38.2 g of zirconium hydroxide powder was added to 48.0 g of a 5 mass% sulfuric acid aqueous solution, impregnated at 40 °C for 4 h, and the impregnated solid was dried at 60 °C for 12 h and at 120 °C for 12 h.

[0098] ​The dried solid was ground into a fine powder and passed through a 100-300 mesh sieve. 4.4 g of all-silicon MFI molecular sieve and 10.6 g of pseudo-boehmite powder were added thereto and mixed evenly. A 5.0 mass% nitric acid aqueous solution was added for peptization. The ratio of the nitric acid aqueous solution to the total mass of the fine powder, MFI molecular sieve and alumina precursor was 0.6:1. After kneading evenly, the mixture was extruded into strips. The wet strips were dried at 120°C for 10 h and calcined at 680°C for 4 h to obtain the active matrix SSiZA-4. The composition is shown in Table 1.

[0099] (2) 10.0 g of the active matrix SSiZA-4 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid. The mixture was immersed at 25°C for 3 h. The immersed solid was dried at 120°C for 10 h and calcined at 550°C for 4 h to produce catalyst CAT-5. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0100] Example 6

[0101] The method of Example 2 was followed, except that the amount of chloroplatinic acid used in step (2) was 0.0106 g.

[0102] Catalyst CAT-6 was obtained. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0103] Example 7

[0104] The method of Example 2 is followed, except that nitric acid is not introduced into the impregnation solution in step (2) as a competitive adsorbent.

[0105] Catalyst CAT-7 was obtained. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0106] Comparative Example 1

[0107] (1) Take 38.2g of zirconium hydroxide powder, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40℃ for 4h, dry the soaked solid at 60℃ for 12h and 120℃ for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 16.6g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution to peptize, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor is 0.6:1, mix evenly and extrude into strips, dry the wet strips at 120℃ for 10h and calcine at 680℃ for 4h to obtain the active matrix DSSiZA-1. XRD characterization results of the active matrix DSSiZA-1 are shown in Figure 2 It can be seen that the catalyst DA1 does not contain the characteristic peak of all-silicon MFI molecular sieve Si-1. The composition is shown in Table 1.

[0108] (2) Take 10.0 g of the active matrix DSSiZA-1 above, add to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, immerse at 25 °C for 3 h, dry the immersed solid at 120 °C for 10 h, and calcine at 550 °C for 4 h to prepare a catalyst DCAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0109] Comparative Example 2

[0110] (1) Take 38.2 g of zirconium hydroxide powder and 10.2 g of the all-silica MFI molecular sieve, mix well, add 48.0 g of a 5 mass% sulfuric acid aqueous solution, immerse at 40 °C for 4 h, dry the immersed solid at 60 °C for 12 h and at 120 °C for 12 h. Grind the dried solid to a fine powder, pass through a 100-300 mesh sieve, and gelatinize with a 5.0 mass% nitric acid aqueous solution at a mass ratio of the nitric acid aqueous solution to the fine powder of 0.6:1. After kneading well, extrude into strips, dry the wet strips at 120 °C for 10 h, and calcine at 680 °C for 4 h to prepare an active matrix DSSiZA-2. The composition of the active matrix DSSiZA-2 is shown in Table 1.

[0111] (2) Take 10.0 g of the active matrix DSSiZA-2, add to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, immerse at 25 °C for 3 h, dry the immersed solid at 120 °C for 10 h, and calcine at 550 °C for 4 h to prepare a catalyst DCAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0112] Comparative Example 3

[0113] Prepare the active matrix DSSiZA-3 according to the method of Example 2, except that an equal mass of fumed silica Si-2 (produced by Changling Catalyst Co., Ltd., with a silicon oxide content of 99.9 mass%, and XRD characterization shown in Figure 1 ) is used instead of the all-silica MFI molecular sieve Si-1. The composition of the active matrix DSSiZA-3 is shown in Table 1.

[0114] Prepare a catalyst DCAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0115] Comparative Example 4

[0116] Prepare the active matrix DSSiZA-4 according to the method of Example 2, except that an equal mass of MCM-41 molecular sieve (denoted as Si-3, produced by Changling Catalyst Co., Ltd., with a silicon oxide content of 99.7 mass%, and XRD characterization shown in Figure 1 ) is used instead of the all-silica MFI molecular sieve. The composition of the active matrix DSSiZA-4 is shown in Table 1. It can be seen from the results in Table 1 that due to the poor thermal stability of MCM-41, the structure collapses at high temperature calcination, resulting in loss of SO3 in the catalyst.

[0117] Catalyst DCAT-4 was prepared. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0118] Comparative Example 5

[0119] The method of Example 2 was followed, except that an equal mass of ZSM-5 molecular sieve (denoted as Si-4, produced by Changling Catalyst Company, with a silicon oxide / aluminum oxide molar ratio of 65, as shown in XRD characterization) was used. Figure 1 ) replaces the all-silicon MFI molecular sieve.

[0120] The obtained active matrix was designated as DSSiZA-5. The composition of the active matrix DSSiZA-5 is shown in Table 1.

[0121] Catalyst DCAT-5 was prepared. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0122] Table 1

[0123]

[0124] Table 2

[0125]

[0126]

[0127] Test Example 1

[0128] The following test examples are used to investigate the isomerization reaction performance of the catalyst.

[0129] The catalysts prepared in the above examples and comparative examples were first subjected to hydrogen reduction in a small fixed-bed reactor using n-butane with a purity of >99.8% by mass as the reaction raw material, and then their activity was evaluated. The hydrogen reduction conditions were: 260°C, 0.1 MPa gauge pressure, a gas-to-catalyst volume ratio of 800, and reduction for 3 hours.

[0130] Evaluation conditions: 250°C, 1.8 MPa, feed mass space velocity of 1.5 hr -1 , the hydrogen / hydrocarbon molar ratio was 1.5, and the evaluation results after 10h and 100h of reaction were recorded and listed in Table 3.

[0131] n-Butane conversion (%) = ((mass of n-butane in the feedstock - mass of n-butane in the product) / mass of n-butane in the feedstock) × 100%;

[0132] Isobutane selectivity (%) = (mass of isobutane in the product / (mass of n-butane in the feedstock - mass of n-butane in the product)) x 100%.

[0133] Table 3

[0134]

[0135]

[0136] Test Example 2

[0137] The following test examples are used to investigate the stability of the catalyst in normalization reactions.

[0138] Using isobutane with a purity of >99.8% by mass as the reaction raw material, the above catalysts and a comparative catalyst were first subjected to hydrogen reduction in a small fixed-bed reactor, and then their activity was evaluated. The hydrogen reduction conditions were: 260°C, 0.1 MPa gauge pressure, gas-to-catalyst volume ratio of 800, and reduction for 3 hours.

[0139] Evaluation conditions: 260°C, 1.8 MPa, feed mass space velocity of 2.0 hr -1 , the hydrogen / hydrocarbon molar ratio was 2.0, and the evaluation results after 10h and 100h of reaction were recorded and listed in Table 4.

[0140] Wherein, isobutane conversion (%) = ((mass of isobutane in the feedstock - mass of isobutane in the product) / mass of isobutane in the feedstock) × 100%;

[0141] Normal butane selectivity (%) = (mass of normal butane in the product / (mass of isobutane in the feedstock - mass of isobutane in the product)) x 100%.

[0142] Table 4

[0143]

[0144]

[0145] The results in Tables 3 and 4 demonstrate that the catalysts prepared in the examples of the present invention exhibit both high n-isomerization activity and selectivity. The MFI-structured all-silicon molecular sieve and alumina modulate the distribution of strong acid centers in the solid acid catalyst, resulting in excellent n-isomerization activity and selectivity. Furthermore, the n-isomerization selectivity retention rate of the catalysts remained above 99% after 100 hours of reaction, demonstrating the catalyst's excellent activity and stability.

[0146] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A normal isomerization catalyst, characterized in that The catalyst includes an active matrix and an active metal component supported on the active matrix; Wherein, the active matrix includes the acidic active component SO4 2- / ZrO2, an all-silicon molecular sieve having an MFI structure, and alumina; the active metal component is selected from at least one of the noble metal elements; Wherein, the density of the strong acid center in the catalyst is 0.1-1 μmol / m 2 ; In the catalyst, the molar ratio of the strong acid to the weak acid is 4-8:1; Based on the total mass of the catalyst, the content of the active matrix is ​​99-99.95 wt%; calculated as an element, the content of the active metal component is 0.05-1 wt%; The active matrix includes zirconium, silicon, aluminum and sulfur, calculated as zirconium oxide, silicon oxide, aluminum oxide and SO3 respectively. Based on the total mass of the active matrix, the content of zirconium oxide is 30-90wt%, the content of silicon oxide is 1-35wt%, the content of aluminum oxide is 5-50wt% and the content of SO3 is 1-10wt%.

2. The catalyst according to claim 1, wherein The density of the strong acid center in the catalyst is 0.2-0.7 μmol / m 2 .

3. The catalyst according to claim 1, wherein Based on the total mass of the catalyst, the content of the active matrix is ​​99.5-99.9wt%; Calculated on the basis of elements, the content of the active metal component is 0.1-0.5 wt %.

4. The catalyst according to claim 1, wherein The active metal component is selected from Pt and / or Pd.

5. The catalyst according to claim 1, wherein Based on the total mass of the active matrix, 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 SO 3 is 2-8 wt %.

6. The catalyst according to any one of claims 1 to 5, wherein The mass ratio of SO3 to ZrO2 is (0.02-0.12):

1.

7. The catalyst according to claim 6, wherein The mass ratio of SO3 to ZrO2 is (0.03-0.08):

1.

8. The catalyst according to any one of claims 1 to 5, wherein In the active matrix, the mass ratio of the acidic active component calculated as ZrO2 to the mass ratio of the all-silicon molecular sieve calculated as SiO2 is 1:(0.1-1).

9. The catalyst according to claim 8, wherein In the active matrix, the mass ratio of the acidic active component calculated as ZrO2 to the mass ratio of the all-silicon molecular sieve calculated as SiO2 is 1:(0.15-0.5).

10. A method for preparing the n-isomerization catalyst according to any one of claims 1 to 9, comprising: (1) Mixing an all-silicon molecular sieve having an MFI structure and zirconium hydroxide to obtain a mixture; (2) contacting the mixture with a solution containing sulfate; (3) mixing the product obtained in step (2), an alumina precursor, and an optional peptizing agent, forming and calcining the mixture to obtain an active matrix; (4) Loading the active metal component on the active matrix.

11. The preparation method according to claim 10, wherein The specific surface area of ​​the all-silicon molecular sieve is 400-500m 2 / g.

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

13. The preparation method according to claim 10, wherein The contact temperature is 20-80° C. and the contact time is 1-10 h.

14. The preparation method according to claim 13, wherein The contact temperature is 25-60° C. and the contact time is 2-5 hours.

15. The preparation method according to claim 10, wherein The solution containing sulfate radicals is selected from an aqueous solution of at least one of sulfuric acid, ammonium sulfate and ammonium bisulfate.

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

17. The preparation method according to claim 16, wherein The concentration of sulfate in the solution containing sulfate is 2-8 wt %.

18. The preparation method according to claim 10, wherein The mass ratio of the solution containing sulfate radical to the mixture is 0.3-5:

1.

19. The preparation method according to claim 18, wherein The mass ratio of the solution containing sulfate radical to the mixture is 0.5-3:

1.

20. The preparation method according to claim 10, wherein The alumina precursor is pseudo-boehmite and / or gibbsite.

21. The preparation method according to claim 20, wherein The alumina precursor is pseudo-boehmite.

22. The preparation method according to claim 10, wherein The total mass ratio of the peptizing agent to the product obtained in step (2) to the alumina precursor is 0.3-1:

1.

23. The preparation method according to claim 10, wherein The peptizing agent is an aqueous solution of acid.

24. The preparation method according to claim 23, wherein The peptizing agent is selected from an aqueous solution of at least one of nitric acid, acetic acid, citric acid, oxalic acid and formic acid.

25. The preparation method according to any one of claims 10 to 24, wherein: The forming method is selected from any one of extrusion forming, granulation forming, ball forming and spray drying into balls.

26. The preparation method according to claim 25, wherein The forming method is extrusion forming.

27. The preparation method according to any one of claims 10 to 24, wherein: In step (3), the calcination temperature is 600-850°C and the calcination time is 1-20h.

28. The preparation method according to claim 27, wherein In step (3), the calcination temperature is 650-850°C and the calcination time is 3-12h.

29. The preparation method according to any one of claims 10 to 24, wherein: The method of loading the active metal component on the active matrix includes: impregnating the active matrix with a solution containing a soluble compound of the active metal, followed by drying and calcining.

30. The preparation method according to claim 29, wherein The solution also contains a competitive adsorbent.

31. The preparation method according to claim 30, wherein The competitive adsorbent is at least one of sulfuric acid, nitric acid and acetic acid.

32. The preparation method according to claim 30, wherein The mass ratio of the competitive adsorbent to the soluble compound of the active metal is 1-20:

1.

33. The preparation method according to any one of claims 10 to 24, wherein: The preparation method further comprises: subjecting the product obtained in step (4) to a reduction treatment in the presence of hydrogen.

34. The preparation method according to claim 33, wherein The reduction treatment conditions include: temperature of 200-300° C., time of 1-10 h, and gas-to-agent volume ratio of 300-1500.

35. The preparation method according to claim 34, wherein The reduction treatment conditions include: temperature of 220-260° C., time of 3-5 hours, and gas volume ratio of 500-1200.

36. Use of the n-isomerization catalyst according to any one of claims 1 to 9 or the n-isomerization catalyst prepared by the preparation method according to any one of claims 10 to 35 in an isomerization reaction or a normalization reaction of C4-C6 light hydrocarbons.

Images