Process and isobutane normalization reaction system for isobutane normalization

Abstract

The present application relates to the technical field of isobutane normalization, and discloses an isobutane normalization method and an isobutane normalization reaction system, the method comprising: under hydrogen conditions, under isobutane normalization reaction conditions, contacting isobutane raw material with a catalyst; wherein the catalyst comprises an acidic active component SO4 2‑ / ZrO2, a full-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m 2 The method has high isobutane single-pass conversion rate and n-butane selectivity, and high n-butane yield.

Description

Technical Field

[0001] This invention relates to the field of isobutane normalization technology, and more specifically to a method and system for isobutane normalization reaction. Background Technology

[0002] n-Butane is a high-quality feedstock for ethylene cracking. Compared to isobutane, it has higher triene yields and lower methane byproducts. n-Butane is also a feedstock for the oxidative process to produce maleic anhydride. In recent years, many new ethylene cracking units have been built in China. To save energy, reduce consumption, and improve market competitiveness, there is a clear trend towards larger units and lighter feedstocks, leading to a significant shortage of ethylene cracking feedstock. Increasing n-Butane production has become an important option to compensate for this shortage. Furthermore, the market for fully biodegradable plastics has ushered in unprecedented development opportunities. Since biodegradable plastics mainly use maleic anhydride as a feedstock, the demand for maleic anhydride and its upstream n-butane has surged. In my country, n-Butane is mainly found in mixed butane byproducts of petroleum refining processes such as catalytic cracking and hydrocracking. For example, the n-butane content in butane byproducts of catalytic cracking is typically 40%, with the remainder being isobutane. For chemical refineries without alkylation units, isobutane is usually treated as a low-value-added product. Therefore, developing isobutane n-assembly technology to increase the production of n-butane, which is in high demand in the market, is of great significance for improving the economic efficiency of refineries and helping oil refining enterprises transform into chemical enterprises.

[0003] The isobutane normalization is an acid-catalyzed reaction. Existing methods for isobutane normalization primarily utilize catalysts with two types of acid centers: chlorides and SO4. 2- / ZrO2. CN104892339A discloses a method for preparing n-butane from isobutane. The method involves feeding a C4 hydrocarbon rich in isobutane into a normalization reaction zone, where isobutane is converted to n-butane under the action of a catalyst. The reaction product is then fed into a hydrogenation saturation zone for hydrogenation, where the olefins in the reaction product are hydrogenated to saturation. The hydrogenated stream is then sent to a separation unit to separate n-butane, a light component, and isobutane. The isobutane is recycled back to the normalization zone for further reaction. The normalization reaction temperature described in this invention is 200–700°C, the operating pressure is 2–5 MPa, and the molar ratio of total hydrogen content to isobutane in the feed is 1–3:1. The catalyst used comprises a support, an active component, and an acidic component. The active component consists of one or more Group VIII transition elements, and the acidic component is a chloride. CN110385142A discloses a catalyst for the normalization reaction of isobutane and its preparation method. The catalyst uses MCM-41 molecular sieve as support and Pt / SO4 as the substrate. 2- ZrO2 is the active component, and the temperature for the isobutane normalization reaction is 150-350℃, the pressure is 1.5-4.5 MPa, and the mass hourly space velocity (HHSV) of isobutane is 0.5-3.0 h⁻¹. -1The volume ratio of hydrogen to isobutane feed is 200:1. The yield of n-butane using this method is less than 22.1%.

[0004] Therefore, in existing technologies, when the isobutane n-assembly catalyst uses chloride as the acid center, the n-assembly reaction temperature is high, dehydrogenation side reactions are difficult to avoid, and the reaction products contain a large amount of olefins. A hydrogenation saturation unit is required to hydrogenate and saturate the olefins in the reaction products, resulting in a complex process and high energy consumption. When the catalyst uses SO4... 2- When ZrO2 is the acid center, although the normalization reaction temperature is reduced, the single-pass conversion rate is low and the yield of n-butane is low. A large amount of unconverted isobutane needs to be separated from the product, which consumes a lot of energy. In addition, the hydrogen content of the reaction is relatively high. In practical applications, hydrogen needs to be separated from the reaction product and recycled using a circulating hydrogen compressor, which further increases energy consumption and operating costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of low isobutane conversion and low n-butane yield in the existing isobutane normalization reaction, and to provide a method and system for isobutane normalization reaction. This method has a high single-pass conversion rate of isobutane and high n-butane selectivity, and a high n-butane yield.

[0006] To achieve the above objectives, the present invention provides a method for isobutane normalization, the method comprising: contacting an isobutane feedstock with a catalyst under hydrogen-exposed conditions and under isobutane normalization reaction conditions;

[0007] The catalyst includes the acidic active component SO4. 2- The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 .

[0008] Preferably, the isobutane normalization reaction conditions include: a reaction temperature of 170-250℃, preferably 180-230℃; a pressure of 0.5-3.5 MPa, preferably 1-3 MPa; and a mass hourly space velocity (HHSV) of 0.5-10 h⁻¹ for the isobutane feedstock. -1 Preferably 1-5h -1 More preferably 1.2-4h -1 The hydrogen / hydrocarbon molar ratio is 0.02-0.3, preferably 0.03-0.2.

[0009] Another aspect of the present invention provides an isobutane normalization reaction system, the reaction system comprising: a feeding unit, a preheating device, a reactor 4, a light component separation device 5, and an isobutane removal tower 6;

[0010] The feeding unit is connected to the feed inlet of the preheating device, and the isobutane raw material and hydrogen are fed into the preheating device for preheating.

[0011] The outlet of the preheating device is connected to the inlet of reactor 4, and the preheated raw material is fed into reactor 4 to contact the catalyst; the catalyst includes the acidic active component SO4. 2- The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 ;

[0012] The light component separation device 5 is used to separate the reaction products from reactor 4, recover the obtained light components, and send the obtained heavy components to the isobutane removal tower 6; wherein, the light components include C1-C3 hydrocarbons and H2, and the heavy components include C4 hydrocarbons. + hydrocarbon;

[0013] The isobutane removal tower 6 is used to separate isobutane and n-butane products, and the separated isobutane is returned to the feed unit.

[0014] The isobutane n-assembly method provided by this invention uses a catalyst comprising the acidic active component SO4. 2- The method utilizes ZrO2, a fully silica molecular sieve with an MFI structure, and alumina. The acid centers of the catalyst are modulated by the fully silica molecular sieve with an MFI structure, optimizing the distribution of acid centers without altering the active phase structure or acid strength. Using this catalyst for the isobutane n-assembly reaction results in high isobutane single-pass conversion and n-butane selectivity. It can utilize isobutane to increase n-butane production, providing high-quality feedstock for ethylene cracking units and butane oxidation to maleic anhydride units, thus realizing the value-added utilization of butane resources. Preferably, the isobutane n-assembly reaction method provided by this invention can efficiently convert isobutane to n-butane under reaction conditions of lower temperature, lower hydrogen-to-oil ratio, and higher space velocity, significantly reducing hydrogen consumption. This reduces energy consumption and feedstock costs, and also facilitates easier post-processing and separation, resulting in good reaction economics. Attached Figure Description

[0015] Figure 1 These are the XRD patterns of the all-silica MFI molecular sieve (Si-1), ZSM-5 molecular sieve (Si-2), and MCM-41 (Si-3) used in the preparation examples of this invention.

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

[0017] Figure 3 This is a schematic diagram of the isobutane ortho-configuration reaction system in one embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures

[0019] 1. Feed pump 2. Heat exchanger 3. Heater

[0020] 4 Reactor; 5 Light component separation unit; 6 Isobutane removal tower Detailed Implementation

[0021] 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.

[0022] The present invention provides a method for isobutane normalization, the method comprising: contacting an isobutane feedstock with a catalyst under hydrogen-exposed conditions and under isobutane normalization reaction conditions;

[0023] The catalyst includes the acidic active component SO4. 2- The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 .

[0024] According to the present invention, the catalyst used in the method for isobutane n-assembly contains the acidic active component SO4. 2- ZrO2, all-silica molecular sieves with MFI structures, and alumina possess suitable densities of strong acid centers. In contrast, the density of strong acid centers in the super-strong solid acid zirconium sulfate in existing technologies is relatively high, generally exceeding 2 μmol / m³. 2 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 high activity and selectivity. This is because, on the one hand, the all-silica molecular sieves with MFI structures are essentially non-acidic and possess excellent thermal stability, thus avoiding the introduction of new acid centers. Simultaneously, optimizing the distribution of strong acid centers in zirconium sulfate facilitates the efficient activation and conversion of butane molecules via a single-molecule pathway. On the other hand, the unique pore structure of the all-silica molecular sieves with MFI structures promotes the diffusion of reactants and products, effectively preventing secondary reactions.

[0025] In existing solid acid catalyst systems, molecular sieves are usually 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.

[0026] Preferably, the density of strong acid centers in the catalyst is 0.5-1.5 μmol / m³. 2 For example, it can be 0.5 μmol / m 2 0.6 μmol / m 2 0.7 μmol / m 2 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, values ​​or ranges between them. Within the above preferred ranges, it is beneficial to further improve the isobutane conversion and n-butane selectivity of the isobutane n-assembly reaction, and increase the n-butane yield.

[0027] 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. -1 The 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) is calculated according to equation (1), N=A / (ρA0), equation (1),

[0028] Where A is the integral area of ​​the absorption peak (in cm²). -1), where ρ is the mass of the catalyst support sheet per square centimeter (unit: g / cm²). 2 A0 is the molar extinction coefficient for a wavenumber of 2167 cm⁻¹. -1 The spectral peak, A0 = 2.6 cm / μmol.

[0029] In this invention, the specific surface area of ​​the catalyst was characterized using 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℃, 1.3 Pa, and treatment for 4 hours. The specific surface area (m²) was calculated using the BET formula. 2 / g).

[0030] In this invention, the phase analysis of the catalyst sample was performed 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°.

[0031] In a preferred embodiment, the isobutane n-assembly reaction method provided by the present invention can efficiently convert isobutane to n-butane under reaction conditions of lower temperature, lower hydrogen-to-oil ratio, and higher space velocity. Preferably, the isobutane n-assembly reaction conditions include: a reaction temperature of 170-250℃, preferably 180-230℃; a pressure of 0.5-3.5 MPa, preferably 1-3 MPa; and a mass hourly space velocity (HHSV) of 0.5-10 h⁻¹ for the isobutane feedstock. -1 Preferably 1-5h -1 The hydrogen / hydrocarbon molar ratio is 0.02-0.3, preferably 0.03-0.2. Adopting the above-mentioned preferred embodiment significantly reduces hydrogen consumption, thereby reducing energy consumption and raw material costs, and also simplifies post-processing and separation, resulting in good reaction economics. In contrast, existing technologies use SO4... 2- When isobutane normalization is carried out using a catalyst with / ZrO2 as the acid center, the hydrogen-hydrocarbon molar ratio is usually not less than 1.

[0032] 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:(0.1-1), for example, it can be a typical but not limiting mass ratio or a range between the two 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. Preferably, 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). Under the above-mentioned preferred mass ratio conditions, it is beneficial for the catalyst to have a suitable density of strong acid centers.

[0033] According to some preferred embodiments of the present invention, the catalyst comprises zirconium, silicon, aluminum, and sulfur, respectively, based on zirconium oxide, silicon oxide, aluminum oxide, and SO3. The zirconium oxide content is 30-90 wt%, the silicon oxide content is 1-35 wt%, the aluminum oxide content is 5-50 wt%, and the SO3 content is 1-10 wt%, based on the total mass of the catalyst. Preferably, based on the total mass of the catalyst, the zirconium oxide content is 50-80 wt%, the silicon oxide content is 5-30 wt%, the aluminum oxide content is 5-30 wt%, and the SO3 content is 2-8 wt%. With the above preferred composition, it is beneficial to improve the thermal stability of tetragonal zirconium oxide and the specific surface area of ​​the catalyst, thereby giving the catalyst a suitable distribution of strong acid centers and accessibility of active centers, further improving the conversion rate of isobutane and the selectivity of n-butane.

[0034] Preferably, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, and more preferably (0.03-0.08):1.

[0035] 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.

[0036] According to 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.

[0037] 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.

[0038] 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.

[0039] According to some preferred embodiments of the present invention, the method for preparing the catalyst includes:

[0040] (1) Mix all-silica molecular sieve with MFI structure and zirconium hydroxide to obtain a mixture;

[0041] The mass ratio of the zirconium hydroxide (calculated as ZrO2) to the all-silica molecular sieve (calculated as SiO2) is 1:(0.1-1).

[0042] (2) Contact the mixture with a solution containing sulfate ions;

[0043] (3) The product obtained in step (2), the alumina precursor and the optional adhesive solvent are mixed and then shaped and calcined.

[0044] 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 conversion of butane molecules through a single molecular pathway, thereby enabling the catalyst to exhibit both high activity and high selectivity in the butane normal isomerization reaction.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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, is beneficial for improving the crushing strength of the catalyst.

[0055] 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. In the above-mentioned preferred cases, it is beneficial to improve the thermal stability and crushing strength of the catalyst.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Preferably, the concentration of acid in the adhesive solvent is 2-10 wt%.

[0060] 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.

[0061] 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.

[0062] According to the present invention, the source of the isobutane feedstock is not particularly required and may include isobutane and optional impurity components. Preferably, the isobutane content in the isobutane feedstock is not less than 80 wt%, more preferably not less than 90 wt%, and more preferably 95-100 wt%. Under the above-mentioned preferred isobutane content, it is beneficial to improve the yield of n-butane.

[0063] Preferably, the impurity component is selected from at least one of C1-C3 alkanes, n-butane, C5+ alkanes, water, and sulfur.

[0064] Preferably, the content of C1-C3 alkanes in the isobutane feedstock is less than 1 wt%, and more preferably less than 0.5 wt%.

[0065] Preferably, the content of C5+ alkanes in the isobutane raw material is less than 1.5 wt%, and more preferably less than 1 wt%.

[0066] Preferably, the content of n-butane in the isobutane raw material is less than 2 wt%, and more preferably less than 1 wt%. In this invention, the hydrocarbon content in the isobutane raw material is obtained by gas chromatography, and then normalized to obtain the content of each component.

[0067] Preferably, the water content in the isobutane feedstock is less than 5 ppmw, and more preferably less than 3 ppmw.

[0068] Preferably, the sulfur content in the isobutane feedstock is less than 10 ppmw, and more preferably less than 5 ppmw.

[0069] According to some preferred embodiments of the present invention, the method further includes: preheating the isobutane feedstock and hydrogen to the isobutane normalization reaction temperature before contacting them with the catalyst. According to the present invention, the isobutane feedstock and hydrogen can be preheated separately, or they can be mixed and preheated together. From an economic perspective, it is preferable to mix the isobutane feedstock and hydrogen and preheat them together.

[0070] Preferably, the preheating includes primary preheating and secondary preheating. The primary preheating method includes exchanging heat between the product of the isobutane n-assembly reaction and the isobutane feedstock and / or hydrogen. The primary preheating can be carried out using conventional heat exchange devices in the art, such as shell-and-tube heat exchangers. The secondary preheating can be carried out using a gas-fired furnace, an electric heater, or a medium-pressure steam heater. Those skilled in the art can select the temperature of the secondary preheating according to the actual operating conditions, as long as the feedstock after primary preheating can be heated to the reaction temperature.

[0071] It is understandable that, during the initial start-up phase of the reaction, the feedstock can be directly heated to the isobutane normalization reaction temperature via secondary preheating. During continuous reaction operation, primary preheating is used to exchange heat between the isobutane feedstock and / or hydrogen and the products of the isobutane normalization reaction, followed by secondary preheating to further heat the feedstock to the isobutane normalization reaction temperature. Adopting this preferred embodiment helps to further reduce reaction energy consumption and improve the economic efficiency of the isobutane normalization process.

[0072] According to the present invention, preferably, the method further includes: separating and purifying the contacted product. The separation and purification can be carried out using any method known in the art, as long as n-butane can be separated from the product. Preferably, the separation and purification includes: separating the contacted product by distillation to obtain light components and heavy components, wherein the light components include C1-C3 hydrocarbons and H2, and the heavy components include C4 hydrocarbons. + Hydrocarbons; then isobutane is separated from the heavy components by an isobutane removal tower, and the separated isobutane can be reused as isobutane feedstock.

[0073] A second aspect of the present invention provides an isobutane normalization reaction system, the reaction system comprising: a feeding unit, a preheating device, a reactor 4, a light component separation device 5, and an isobutane removal tower 6;

[0074] The feeding unit is connected to the feed inlet of the preheating device, and sends isobutane raw material and hydrogen into the preheating device for preheating.

[0075] The outlet of the preheating device is connected to the inlet of reactor 4, and the preheated raw material is fed into reactor 4 to contact the catalyst; the catalyst includes the acidic active component SO4. 2- The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 ;

[0076] The light component separation device 5 is used to separate the reaction products from reactor 4, recover the obtained light components, and send the obtained heavy components to the isobutane removal tower 6; wherein, the light components include C1-C3 hydrocarbons and H2, and the heavy components include C4 hydrocarbons. + hydrocarbon;

[0077] The isobutane removal tower 6 is used to separate isobutane and n-butane products, and the separated isobutane is returned to the feed unit.

[0078] The catalyst in the isobutane normalization reaction system of the present invention has the same definition as the catalyst described in the first aspect, and will not be repeated here.

[0079] According to some preferred embodiments of the present invention, the feeding unit includes an isobutane feedstock supply device and a hydrogen supply device.

[0080] Preferably, the isobutane feedstock supply device includes a feed pump 1, through which the isobutane feedstock is transported to a preheating device for preheating.

[0081] Preferably, the preheating device includes a heat exchanger 2 and a heater 3.

[0082] The heat exchanger 2 is used to exchange heat between the reaction product from the reactor 4 and the isobutane feedstock and hydrogen from the feed unit. The reaction product after heat exchange is sent to the light component separation device 5, and the isobutane feedstock and hydrogen are sent to the heater 3.

[0083] The heater 3 is used to heat the isobutane feedstock and hydrogen from the heat exchanger 2 to the isobutane normalization reaction temperature, and then send them into the reactor 4.

[0084] The present invention will be described in detail below through embodiments.

[0085] 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°.

[0086] 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.

[0087] The zirconium hydroxide powder used was purchased from Changling Catalyst Company, with a zirconium oxide content of 78.5% by weight.

[0088] 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.

[0089] The boehmite powder was purchased from Sasol GmbH, Germany, with an alumina content of 75% by mass.

[0090] The following preparation examples illustrate the preparation of the catalyst in this invention.

[0091] Preparation Example 1

[0092] 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.

[0093] 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).

[0094] Preparation Example 2

[0095] 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.

[0096] 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).

[0097] Preparation Example 3

[0098] 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.

[0099] 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).

[0100] Preparation Example 4

[0101] The method of preparation Example 2 was followed, except that the amount of all-silica MFI molecular sieve Si-1 used was 21 g. The resulting catalyst was designated A4, and its composition and physicochemical properties are shown in Table 1 and Table 1 (continued).

[0102] Preparation Example 5

[0103] 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.

[0104] 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).

[0105] Preparation Example 6

[0106] 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.

[0107] 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).

[0108] Comparative Preparation Example 1

[0109] 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.

[0110] 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).

[0111] Comparative Preparation Example 2

[0112] 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.

[0113] 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).

[0114] Comparative preparation example 3

[0115] The method was the same as in Example 2, except that an equal mass of ZSM-5 molecular sieve (denoted as Si-2, manufactured by Changling Catalyst Co., Ltd., with a silica / alumina molar ratio of 65) was used. XRD characterization is shown in [reference needed]. Figure 1 )

[0116] The composition and physicochemical properties of the prepared catalyst, denoted as catalyst DA3, are shown in Table 1 and Table 1 (continued).

[0117] Comparative preparation example 4

[0118] The method was the same as 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 in [reference needed]. Figure 1 Replace the all-silica MFI molecular sieve.

[0119] The composition and physicochemical properties of the prepared catalyst, denoted as catalyst DA4, are shown in Table 1 and Table 1 (continued).

[0120] Table 1

[0121]

[0122]

[0123] Continued from Table 1

[0124]

[0125] The following examples illustrate the isobutane n-assembly method provided by the present invention.

[0126] The isobutane feedstock used in the following examples includes: 0.04% propane, 98.74% isobutane, 0.76% n-butane, and 0.46% pentane.

[0127] The following embodiments employ the following methods: Figure 3 The isobutane n-assembly reaction system shown is carried out. For example... Figure 3 As shown, the reaction system includes: a feeding unit, a preheating device, a reactor 4, a light component separation device 5, and an isobutane removal tower 6; the feeding unit includes an isobutane feedstock supply device and a hydrogen supply device, the isobutane feedstock supply device including a feed pump 1, and the preheating device including a heat exchanger 2 and a heater 3. The reactor 4 is loaded with catalyst, and the loading and reaction conditions are shown in Tables 2 and 3.

[0128] At startup, isobutane feedstock is introduced into the feed line via feed pump 1, mixed with hydrogen, and then heated to the reaction temperature via heat exchanger 2 and heater 3. It is then fed into reactor 4 to contact the catalyst for isobutane n-assembly. The resulting reaction product is fed into heat exchanger 2 for heat exchange with the isobutane and hydrogen mixture. The heat-exchanged reaction product is then fed into light component separation unit 5. Light components, consisting of C1-C3 hydrocarbons and a small amount of H2, are separated at the top of the unit; C4 hydrocarbons are separated at the bottom. + Hydrocarbons are fed into isobutane removal column 6 for separation. Isobutane is separated at the top of the column and recycled back to the feed unit to mix with the isobutane feedstock. A small amount of C5 is separated at the bottom of the column.+ The heavy components were extracted via a side stream, yielding n-butane. Product sampling and analysis method: A bypass with a sampling port was installed on the main outlet line of reactor 4. During sampling, the sampling cylinder was connected to the sampling port via a quick connector. Then, the valves before and after the sampling cylinder were opened, and the cylinder was purged with the product. After purging, the outlet valve of the sampling cylinder was closed. After a certain amount of the material to be analyzed was introduced, the inlet valve was closed, and the quick connector was disconnected. Sampling was then complete. The sample was sent to the laboratory for analysis of the reactor outlet product composition. The analysis results are listed in Tables 2 and 3.

[0129] Wherein, isobutane conversion rate (%) = ((mass of isobutane in feed - mass of isobutane in product) / mass of isobutane in feed) × 100%;

[0130] n-Butane selectivity (%) = ((mass of n-butane in product - mass of n-butane in feed) / (mass of isobutane in feed - mass of isobutane in product)) × 100%;

[0131] n-Butane yield (%) = ((mass of n-butane in product - mass of n-butane in feed) / mass of isobutane in feed) × 100%.

[0132] Table 2

[0133]

[0134]

[0135] Table 3

[0136]

[0137] As can be seen from the results in Tables 2 and 3, the method for isobutane n-assembly provided by this invention exhibits both high isobutane conversion and n-butane selectivity, resulting in a high n-butane yield. In the preferred embodiment, by combining the reaction conditions of low temperature and low hydrogen-to-hydrogen ratio, this method achieves an even higher n-butane yield while simultaneously reducing hydrogen consumption. This reduces energy consumption and raw material costs, and also simplifies post-processing and separation, resulting in good reaction economy.

[0138] 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. A method for the n-assembly of isobutane, characterized in that, The method includes: contacting an isobutane feedstock with a catalyst under hydrogen-exposed conditions and under isobutane normalization reaction conditions; The catalyst includes the acidic active component SO4. 2- The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 ; 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).

2. The method according to claim 1, wherein, The isobutane normalization reaction conditions include: a reaction temperature of 170-250℃; a pressure of 0.5-3.5 MPa; and a mass hourly space velocity (HHSV) of 0.5-10 h⁻¹ for the isobutane feedstock. -1 The hydrogen / hydrocarbon molar ratio is 0.02-0.

3.

3. The method according to claim 2, wherein, The isobutane n-assembly reaction conditions include: a reaction temperature of 180-230℃; a pressure of 1-3 MPa; and a mass hourly space velocity (H₂S) of the isobutane feedstock of 1-5 h⁻¹. -1 The hydrogen / hydrocarbon molar ratio is 0.03-0.

2.

4. The method according to claim 3, wherein, The isobutane normalization reaction conditions include: a mass hourly space velocity (MSV) of 1.2-4 h⁻¹ for the isobutane feedstock. -1 .

5. The method according to claim 1, wherein, In the catalyst, the density of strong acid centers is 0.5-1.5 μmol / m³. 2 .

6. The method according to claim 1, wherein, 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%.

7. The method according to claim 6, 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%.

8. The method according to claim 6, wherein, The mass ratio of SO3 to ZrO2 is (0.02-0.12):

1.

9. The method according to claim 8, wherein, The mass ratio of SO3 to ZrO2 is (0.03-0.08):

1.

10. The method according to claim 1, wherein, The catalyst has a specific surface area of ​​80-180 m². 2 / g.

11. The method according to claim 10, wherein, The catalyst has a specific surface area of ​​90-160 m². 2 / g.

12. The method according to claim 11, wherein, The catalyst has a specific surface area of ​​100-150 m². 2 / g.

13. The method according to claim 1, wherein, The alumina is γ-Al2O3.

14. The method according to claim 1, wherein, The isobutane feedstock includes isobutane and optional impurity components.

15. The method according to claim 14, wherein, The isobutane content in the isobutane raw material is not less than 80 wt%.

16. The method according to claim 15, wherein, The isobutane content in the isobutane raw material is not less than 90 wt%.

17. The method according to claim 16, wherein, The isobutane content in the isobutane raw material is 95-100 wt%.

18. The method according to claim 14, wherein, The impurity component is selected from at least one of C1-C3 alkanes, n-butane, C5+ alkanes, water, and sulfur.

19. The method according to claim 18, wherein, The isobutane feedstock contains less than 1 wt% of C1-C3 alkanes.

20. The method according to claim 19, wherein, The isobutane feedstock contains less than 0.5 wt% of C1-C3 alkanes.

21. The method according to claim 18, wherein, The isobutane raw material contains less than 2 wt% n-butane.

22. The method according to claim 21, wherein, The isobutane raw material contains less than 1 wt% n-butane.

23. The method according to claim 18, wherein, The isobutane feedstock has a water content of less than 5 ppmw.

24. The method according to claim 23, wherein, The isobutane feedstock has a water content of less than 3 ppmw.

25. The method according to claim 18, wherein, The sulfur content in the isobutane feedstock is less than 10 ppmw.

26. The method of claim 25, wherein, The sulfur content in the isobutane feedstock is less than 5 ppmw.

27. The method according to claim 1, wherein, The method further includes: preheating the isobutane feedstock and hydrogen to the isobutane normalization reaction temperature before contacting them with the catalyst.

28. The method according to claim 27, wherein, The preheating includes primary preheating and secondary preheating. The primary preheating method includes exchanging heat between the product of the isobutane ortho-formation reaction and the isobutane feedstock and / or hydrogen.

29. The method according to claim 1, wherein, The method further includes: separating and purifying the product of the contact, wherein the separated isobutane is used to provide at least a portion of the isobutane raw material.

30. An isobutane n-assembly reaction system, characterized in that, The reaction system includes: a feeding unit, a preheating device, a reactor (4), a light component separation device (5), and an isobutane removal tower (6). The feeding unit is connected to the feed inlet of the preheating device, and the isobutane raw material and hydrogen are fed into the preheating device for preheating. The outlet of the preheating device is connected to the feed inlet of the reactor (4), and the preheated raw material is fed into the reactor (4) to contact the catalyst; the catalyst includes the acidic active component SO4. 2- The catalyst comprises ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m³. 2 ; The light component separation device (5) is used to separate the reaction products from the reactor (4), recover the obtained light components, and send the obtained heavy components to the isobutane removal tower (6); wherein, the light components include C1-C3 hydrocarbons and H2, and the heavy components include C4 hydrocarbons. + hydrocarbon; The isobutane removal tower (6) is used to separate isobutane and n-butane products, and the separated isobutane is returned to the feed unit.

31. The reaction system according to claim 30, wherein, The feeding unit includes an isobutane feedstock supply device and a hydrogen supply device.

32. The reaction system according to claim 31, wherein, The isobutane feedstock supply device includes a feed pump (1), through which the isobutane feedstock is transported to a preheating device for preheating.

33. The reaction system according to claim 32, wherein, The preheating device includes a heat exchanger (2) and a heater (3). The heat exchanger (2) is used to exchange heat between the reaction product from the reactor (4) and the isobutane feedstock and hydrogen from the feed unit. The reaction product after heat exchange is sent to the light component separation device (5), and the isobutane feedstock and hydrogen are sent to the heater (3). The heater (3) is used to heat the isobutane feedstock and hydrogen from the heat exchanger (2) to the isobutane normalization reaction temperature, and then send them into the reactor (4).

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