Process for the isomerization of n-butane

Abstract

The application relates to the technical field of n-butane isomerization, and discloses a method for n-butane isomerization reaction, which comprises the following steps: under hydrogen conditions, n-butane raw material is contacted with a catalyst under isomerization reaction conditions; wherein the catalyst comprises an acidic active component SO4 2‑ / ZrO2, a full-silica molecular sieve with an MFI structure and alumina; the mass ratio of the acidic active component to the full-silica molecular sieve is 1:(0.1-1) in the form of ZrO2 to SiO2. The method is moderate in conditions, friendly to the environment, and has high n-butane single-pass conversion rate and isobutane selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of n-butane isomerization, in particular to a method for n-butane isomerization reaction. BACKGROUND

[0002] Isobutane is an important light hydrocarbon resource. In recent years, with the construction of isobutane-butene alkylation, isobutane dehydrogenation, and isobutane-propylene co-oxidation devices in China, isobutane resources are increasingly in short supply. With the continuous upgrading of China's gasoline standards, isobutane-butene alkylation, as one of the indispensable technologies for gasoline upgrading, its production capacity will further increase. N-butane isomerization is a technology that can efficiently convert n-butane in C4 resources into isobutane. Therefore, the development of n-butane isomerization technology has important practical significance for increasing isobutane production and optimizing the use of C4 resources.

[0003] An efficient n-butane isomerization catalyst is the core of n-butane isomerization technology. There are two types of traditional n-butane isomerization catalysts, one is Pt-containing chlorinated alumina (Pt / Al2O3-Cl) catalyst, and the other is Pt or Pd-loaded zeolite molecular sieve (Pt(Pd) / zeolite) catalyst. Pt / Al2O3-Cl catalyst has the advantages of low reaction temperature and high single-pass conversion rate, but the disadvantages are that the catalyst is sensitive to impurities in the raw material, which requires strict refining of the raw material to remove impurities such as sulfur and water, and that the catalyst needs to be continuously injected with chlorine to maintain its activity during the isomerization reaction, and the catalyst cannot be regenerated, which further limits the application of this type of technology. Pt(Pd) / zeolite catalyst has a relatively loose requirement for impurities in the raw material, but the n-butane isomerization activity and selectivity are low.

[0004] Solid superacid catalyst is a new type of catalyst developed in recent years. CN109265308A discloses a production method for n-butane isomerization using a solid acid bifunctional catalyst, at least one of CuGa-SO4 2- / ZrO2, NiGa-SO4 2- / ZrO2, PtGa-SO4 2- / ZrO2, PbGa-SO4 2- / ZrO2 is used as the catalyst, under the conditions of pressure 1.5-3.0 MPa, reactor inlet temperature 200-250℃, hydrogen / hydrocarbon volume ratio 1-5, and n-butane mass space velocity 0.2-1.0, the n-butane single-pass conversion rate is 50-55%, and the isobutane selectivity is 80-85%. CN107051420A discloses a lanthanum and molybdenum modified zirconium sulfate type n-butane isomerization catalyst and its use method. When the catalyst is used for n-butane isomerization reaction, under the conditions of 220℃, 2.0 MPa, feed mass space velocity 2.0 h -1The isomerization rate of n-butane is 39.7% at most under the condition that the hydrogen / hydrocarbon molecular ratio is 1.2.

[0005] The prior art discloses a n-butane isomerization method based on a solid superacid catalyst of zirconium sulfate oxide type, and air speed and conversion rate are difficult to be considered together, resulting in low n-butane conversion efficiency. In addition, the reaction hydrogen / hydrocarbon ratio is high, and in the actual application process, hydrogen needs to be separated from the reaction product and recycled by using a circulating hydrogen compressor, and the process flow is complex, the equipment investment is high, and energy consumption and operating cost are significantly increased. SUMMARY

[0006] The present application aims to overcome the problems of the prior art n-butane isomerization method, such as high air speed and high conversion rate being difficult to be considered together, complex process flow, and high cost, and provides a n-butane isomerization reaction method, which has high n-butane conversion efficiency and high isobutane yield.

[0007] In order to achieve the above-mentioned purpose, the present application provides a n-butane isomerization reaction method, which comprises: contacting n-butane raw material with a catalyst under hydrogenation condition and isomerization reaction condition.

[0008] The catalyst comprises an acidic active component SO4 2- / ZrO2, a full-silica molecular sieve with MFI structure, and alumina; the mass ratio of the acidic active component to the full-silica molecular sieve is 1:(0.1-1) in terms of ZrO2 and SiO2.

[0009] Preferably, the isomerization reaction condition comprises: the reaction temperature is 165-240℃, preferably 175-225℃; the pressure is 1-4 MPa, preferably 1.5-3.5 MPa; the mass air speed of the n-butane raw material is 0.5-10 h -1 , preferably 1-5 h -1 , more preferably 1.2-4 h -1 ; the hydrogen / hydrocarbon molar ratio is 0.02-0.3, preferably 0.03-0.2.

[0010] The n-butane isomerization method provided by the present application uses full-silica MFI structure molecular sieve modified zirconium sulfate oxide as a catalyst, and has mild reaction conditions, is environment-friendly, has high n-butane single-pass conversion rate and isobutane selectivity, can utilize n-butane to produce isobutane, and can provide raw materials for alkylation, isobutane dehydrogenation, C3 / C4 mixed dehydrogenation, PO / MTBE, etc., and realize the value-added utilization of butane resources. Preferably, the method can efficiently isomerize n-butane to isobutane under the reaction condition of low temperature, low hydrogen / oil ratio, and high air speed, which is beneficial to reduce energy consumption and process cost. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 are XRD patterns of the all-silica MFI molecular sieve (Si-1) and ZSM-5 molecular sieve (Si-2) used in the preparation examples of the present application;

[0012] Figure 2 are XRD patterns of the catalysts prepared in Preparation Examples 1-3 and Comparative Preparation Example 1 of the present application;

[0013] Figure 3 is a schematic diagram of a n-butane isomerization reaction system in one embodiment of the present application.

[0014] BRIEF DESCRIPTION OF DRAWINGS

[0015] 1 feed pump 2 heat exchanger 3 heater

[0016] 4 reactor 5 light ends separation device 6 isobutane removal column DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are provided as approximate descriptions of the ranges and are understood to be open-ended. Each range disclosed herein is to be understood to be inclusive of the endpoints, and also to include any other ranges which can be derived from the stated endpoints by simply combining the lower value of the stated endpoints with the upper value of other endpoints. Any range of values which has a value disclosed as the lower or upper limit of that range is also disclosed. Any individual value disclosed herein can also be added to any disclosed range of values, whether or not also recited.

[0018] The present application provides a method for n-butane isomerization reaction, which comprises: contacting a n-butane raw material with a catalyst under hydrogen-approaching conditions and under isomerization reaction conditions;

[0019] wherein the catalyst comprises an acidic active component SO4 2- / ZrO2, an all-silica molecular sieve with MFI structure, and alumina; the mass ratio of the acidic active component to the all-silica molecular sieve is 1:(0.1-1) in terms of ZrO2 and SiO2.

[0020] According to the present application, the catalyst used in the method for n-butane isomerization contains an acidic active component SO4 2-ZrO2, a full-silica molecular sieve with MFI structure and alumina, the inventors of the present application have found in their research that a small amount of the full-silica molecular sieve with MFI structure and alumina can play a role in adjusting the distribution of strong acid centers of the solid acid catalyst, thus making the catalyst have high activity and high selectivity. The reason is that, on the one hand, the full-silica molecular sieve with MFI structure has no acidity and excellent thermal stability, which can avoid introducing new acid centers, and at the same time optimize the distribution of strong acid centers in zirconium sulfate, which is conducive to the efficient activation and conversion of butane molecules through a single molecule path. On the other hand, the full-silica molecular sieve with MFI structure has a special pore structure, which is conducive to the diffusion of reactants and products, thus effectively avoiding secondary reactions.

[0021] In the prior art solid acid catalyst system, the molecular sieve is usually used as a carrier, and the molecular sieve used as a carrier accounts for a high content in the catalyst; and the silicon-aluminum molecular sieve introduced into the catalyst is also usually used to provide additional acid active centers.

[0022] According to some preferred embodiments of the present application, the mass ratio of the acid active component to the full-silica molecular sieve in the catalyst, calculated based on ZrO2 and SiO2, is 1:(0.1-1), for example, it can be 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, and the like, which are typical but not limiting mass ratios or ranges therebetween. Preferably, the mass ratio of the acid active component to the full-silica molecular sieve in the catalyst, calculated based on ZrO2 and SiO2, is 1:(0.15-0.5). Under the above preferred mass ratio conditions, the catalyst has a suitable strong acid center density.

[0023] Preferably, the density of strong acid centers in the catalyst is 0.1-2 μmol / m 2 , preferably 0.5-1.5 μmol / m 2 , for example, it can be 0.5 μmol / m 2 , 0.6 μmol / m 2 , 0.7 μmol / 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 2and the like, and ranges between the values are also intended to be included in the disclosure. Within the above preferred ranges, it is advantageous to further improve the activity of the isomerization reaction and increase the isobutane yield.

[0024] In the present application, 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 testing method of the amount of strong acid in the catalyst comprises: using a Nicolet 6700 Fourier transform infrared spectrometer produced by Thermo Fisher Company of the United States, with a resolution of 4 cm -1 -1, and scanning 64 times. The sample is pressed into a self-supporting sheet with a diameter of 13 mm, then placed in a muffle furnace for high-temperature calcination, and after completion, directly cooled in a desiccator at high temperature, and after cooling to room temperature, placed in a self-made quartz infrared sample cell, first treated at 400℃ for 2h under normal pressure flowing air, then cooled to 200℃, vacuum purified for 4h, then cooled to -190℃ with liquid nitrogen, saturated adsorption of the purified CO probe molecule for 0.5h, and then desorption. The spectra before and after adsorption are subtracted to obtain the infrared spectrum of the sample adsorbed CO. The spectrum at a wave number of 2050-2250 cm -1 is subjected to peak separation processing, and the spectrum can be divided into four absorption peaks with wave numbers of 2186 cm -1 , 2167 cm -1 , 2150 cm -1 and 2125 cm -1 , wherein the absorption peak at a wave number of 2167 cm -1 is a strong acid center directly related to the performance of the catalyst, and the amount of strong acid N (unit: μmol / g) is calculated according to formula (1),

[0025] N = A / (ρA0), formula (1),

[0026] wherein A is the integral area of the absorption peak (unit: cm -1 ), ρ is the mass of the catalyst support sheet per square centimeter (unit: g / cm 2 ), and A0 is the molar extinction coefficient, and for the spectrum peak at a wave number of 2167 cm -1 , A0 = 2.6 cm / μmol.

[0027] In the present application, the specific surface area of the catalyst is characterized by low-temperature nitrogen static volume adsorption method (BET method), and the instrument used is an ASAP2400 specific surface area tester produced by Micromeritics Instrument Company, with pretreatment conditions of 250℃, 1.3 Pa, and treatment for 4h, and the specific surface area (m 2 / g) is calculated by using the BET formula.

[0028] In the present application, the phase analysis of the catalyst sample is performed by using a Japan Rigaku D / MAX-3A diffractometer (XRD) under the following conditions: CuKα target, Ni filter, scanning range 5°-70°, and step width 0.02°.

[0029] Preferably, the isomerization reaction method provided by the present application can efficiently convert n-butane into isobutane under the reaction conditions of lower temperature, lower hydrogen / oil ratio and higher space velocity. According to some preferred embodiments of the present application, the isomerization reaction conditions include: reaction temperature 165-240°C, preferably 175-225°C; pressure 1-4 MPa, preferably 1.5-3.5 MPa; mass space velocity of the n-butane raw material 0.5-10 h -1 , preferably 1-5 h -1 ; hydrogen / hydrocarbon molar ratio 0.02-0.3, preferably 0.03-0.2. The use of the above preferred embodiments is advantageous for greatly reducing the hydrogen consumption, which can reduce the energy consumption and raw material cost, and is also advantageous for reducing the difficulty of post-treatment and separation, and has good reaction economy. In the prior art, when the isomerization reaction is performed by using a catalyst with SO4 2- / ZrO2 as the acid center, the hydrogen / hydrocarbon molar ratio is usually not less than 1.

[0030] According to some preferred embodiments of the present application, the catalyst comprises zirconium element, silicon element, aluminum element and sulfur element, and the content of zirconium oxide, silicon oxide, aluminum oxide and SO3 is 30-90 wt%, 1-35 wt%, 5-50 wt% and 1-10 wt% respectively, based on the total mass of the catalyst; preferably, the content of zirconium oxide, silicon oxide, aluminum oxide and SO3 is 50-80 wt%, 5-30 wt%, 5-30 wt% and 2-8 wt% respectively, based on the total mass of the catalyst. Under the above preferred composition, the thermal stability of tetragonal zirconium oxide and the specific surface area of the catalyst can be improved, so that the catalyst has a suitable strong acid center distribution and activity center accessibility, and the conversion rate of n-butane and the selectivity of isobutane are further improved.

[0031] Preferably, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, preferably (0.03-0.08):1.

[0032] In the present application, the catalyst composition is characterized and analyzed by using 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 pure substance sensitivity of these elements in the instrument, the content of each element in the sample is obtained by theoretical calculation and mathematical correction.

[0033] According to the present application, the specific surface area of the catalyst is 80-180 m 2 / g, preferably 90-160 m 2 / g, and further preferably 100-150 m 2 / g.

[0034] According to some preferred embodiments of the present application, the alumina is γ-Al2O3. In the above preferred case, the thermal stability and specific surface area of the catalyst are improved.

[0035] In the present application, the shape of the catalyst is not particularly limited, and can be selected by those skilled in the art according to actual needs. For example, it can be in the form of a strip, a pellet, a sheet, a particle or a microsphere, so as to be suitable for a fixed bed, a moving bed or a fluidized bed reaction.

[0036] According to some preferred embodiments of the present application, the preparation method of the catalyst comprises:

[0037] (1) mixing a full-silica molecular sieve with MFI structure and zirconium hydroxide to obtain a mixture;

[0038] wherein the mass ratio of the zirconium hydroxide to the full-silica molecular sieve is 1:(0.1-1) in terms of the mass of ZrO2 and the mass of SiO2, respectively;

[0039] (2) contacting the mixture with a solution containing sulfate;

[0040] (3) mixing the product obtained in step (2), an alumina precursor and an optional peptizing agent, and then performing molding and calcination.

[0041] According to the present application, by the above preparation method, the full-silica molecular sieve with MFI structure can be uniformly distributed in the catalyst without blocking the pores of the catalyst, the density of the strong acid centers in the zirconium sulfate oxide is reduced without introducing new acid centers, and the existence of the strong acid sites with appropriate density and uniform strength is beneficial to the efficient activation and conversion of butane molecules through a single molecular path, so that the catalyst exhibits high activity and high selectivity in the n-butane isomerization reaction.

[0042] The present application has a wide range of selection for the number and structure of the pores of the full-silica molecular sieve, and the full-silica molecular sieve with MFI structure can be applied to the present application.

[0043] In some preferred embodiments, the specific surface area of the full-silica molecular sieve is 400-500 m 2 / g, and preferably 420-460 m 2 / g. In the above preferred case, the density of the strong acid centers in the zirconium sulfate oxide is further optimized, the uniformity of the strong acid sites is improved, and thus the n-isomerization activity is improved.

[0044] According to some preferred embodiments of the present application, the mass ratio of the zirconium hydroxide to the total siliceous molecular sieve, calculated as ZrO2 to SiO2, is 1:(0.15-0.5).

[0045] In the present application, the contacting of the mixture with the solution containing sulfate in step (2) forms the acidic active component. The contacting can be carried out in a manner conventional in the art, for example, the mixture can be impregnated with the solution containing sulfate.

[0046] The present application does not have particular limitations on the specific operating conditions of the contacting, as long as the catalyst composition range described above can be met, which can be selected by those skilled in the art according to actual needs.

[0047] According to some preferred embodiments of the present application, the temperature of the contacting is 20-80°C, preferably 25-60°C; and the time is 1-10h, preferably 2-5h.

[0048] The present application has a wide range of selection for the specific type of the solution containing sulfate. Preferably, the solution containing sulfate is selected from an aqueous solution of at least one of sulfuric acid, ammonium sulfate and ammonium bisulfate.

[0049] Preferably, the concentration of sulfate in the solution containing sulfate is 1-10wt%, preferably 2-8wt%. The use of the above preferred embodiments is advantageous for obtaining a suitable SO3 content and strong acid center density.

[0050] The present application does not have particular limitations on the amount of the solution containing sulfate, as long as the SO3 content range requirement in the catalyst described in the first aspect can be met, which can be selected by those skilled in the art according to actual needs. Preferably, the mass ratio of the solution containing sulfate to the mixture is 0.3-5:1, preferably 0.5-3:1.

[0051] In the present application, the contacting in step (2) is followed by optional drying and grinding steps. The temperature of the drying can be 50-150°C, and the time of the drying can be 3-100h. The grinding is used to grind the dried solid into a powder of 100-300 mesh, which is advantageous for improving the crushing strength of the catalyst in the above preferred cases.

[0052] In the present application, the alumina precursor refers to a substance that can obtain alumina by calcination, which is well known to those skilled in the art. Preferably, the alumina precursor is pseudoboehmite and / or gibbsite, preferably pseudoboehmite. The use of the above preferred cases is advantageous for improving the thermal stability and crushing strength of the catalyst.

[0053] In the present application, the molding in step (3) can be carried out by using the methods and conditions conventional in the art, and the present application is not particularly limited thereto, and the molding method can be selected as required according to the actual application, for example, can be selected from any one of extrusion molding, granulation molding, rolling ball molding and spray drying into a ball, and preferably is extrusion molding. In the above preferred case, it is more suitable for a fixed bed reactor.

[0054] According to some preferred embodiments of the present application, the ratio of the total mass of the peptizing agent and the product obtained in step (2) to the alumina precursor is 0.3-1:1, preferably 0.4-0.8:1.

[0055] According to some preferred embodiments of the present application, 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.

[0056] Preferably, the concentration of the acid in the peptizing agent is 2-10wt%.

[0057] According to some preferred embodiments of the present application, in step (3), the temperature of the calcination is 600-850°C, preferably 650-850°C, and the calcination time is 1-20h, preferably 3-12h. Under the above preferred calcination temperature conditions, it is advantageous to form strong acid centers with suitable density, and thus to improve the activity and selectivity of the catalyst in the n-butane normal isomerization reaction.

[0058] In the present application, the calcination in step (3) can further include a drying process before the calcination. Preferably, the temperature of the drying is 80-140°C, preferably 100-130°C, and the drying time is 5-30h, preferably 8-24h.

[0059] The present application is not particularly limited to the source of the n-butane raw material, and the n-butane raw material includes n-butane and can also include impurity components. Preferably, in the n-butane raw material, the content of n-butane is not less than 80wt%, preferably not less than 90wt%, and more preferably 95-100wt%.

[0060] Preferably, the impurity components are at least one selected from C1-C3 alkanes, isobutane, C5+ alkanes, water and sulfur elements.

[0061] Preferably, in the n-butane raw material, the content of C1-C3 alkanes is less than 1wt%, preferably less than 0.5wt%.

[0062] Preferably, in the n-butane raw material, the content of C5+ alkanes is less than 1.5wt%, preferably less than 1wt%.

[0063] Preferably, the content of isobutane in the n-butane feedstock is less than 2wt%, preferably less than 1wt%. In the present application, the content of hydrocarbons in the n-butane feedstock is tested by gas chromatography, and then normalized to obtain the content of each component.

[0064] Preferably, the content of water in the n-butane feedstock is less than 5ppmw, preferably less than 3ppmw.

[0065] Preferably, the content of sulfur in the n-butane feedstock is less than 10ppmw, preferably less than 5ppmw.

[0066] According to some preferred embodiments of the present application, the method further comprises: preheating the n-butane feedstock and hydrogen to the isomerization reaction temperature before contacting with the catalyst. In the present application, the n-butane feedstock and hydrogen can be preheated respectively, or the n-butane feedstock and hydrogen can be mixed together and then preheated together. From the economic point of view, it is preferred that the n-butane feedstock and hydrogen are mixed together and then preheated together.

[0067] Preferably, the preheating comprises a first-stage preheating and a second-stage preheating, and the first-stage preheating comprises: exchanging heat between the product of the isomerization reaction and the n-butane feedstock and / or hydrogen. The first-stage preheating can be carried out by using a conventional heat exchanger in the art, for example, a shell-and-tube heat exchanger.

[0068] It can be understood that, when the reaction is initially started, the feedstock can be directly heated to the isomerization reaction temperature by the second-stage preheating, and when the reaction is continuously operated, the n-butane feedstock and hydrogen are exchanged with the product of the isomerization reaction by the first-stage preheating, and then the n-butane feedstock and hydrogen are further heated to the isomerization reaction temperature by the second-stage preheating. By using the above preferred embodiments, it is beneficial to further reduce the energy consumption of the reaction and reduce the process cost.

[0069] According to the present application, preferably, the method further comprises: separating and purifying the product of the contacting to obtain n-butane, and using the n-butane to provide at least part of the n-butane feedstock. The separation and purification can be carried out by using any known method in the art, as long as the isobutane product can be separated from the product. Preferably, the separation and purification comprises: separating the product of the contacting by distillation to obtain light components and heavy components, the light components comprising C1-C3 hydrocarbons and H2, and the heavy components comprising C4 + hydrocarbons; and separating the isobutane product from the heavy components by a de-isobutanizer.

[0070] According to some preferred embodiments of the present application, the n-butane isomerization reaction is carried out in a normalization reaction system, and the reaction system comprises: a feed unit, a preheating device, a reactor 4, a light component separation device 5, and a de-isobutanizer 6.

[0071] The feeding unit is in communication with the feeding port of the preheating device, and the n-butane raw material and hydrogen are fed into the preheating device for preheating.

[0072] The outlet of the preheating device is in communication with the feeding port of the reactor 4, and the preheated raw material is fed into the reactor 4 to contact with the catalyst.

[0073] The light component separation device 5 is used to separate the reaction product from the reactor 4, and the obtained light component is recycled, and the obtained heavy component is fed into the de-isobutane column 6; wherein the light component includes C1-C3 hydrocarbon and H2, and the heavy component includes C4 + hydrocarbon;

[0074] The de-isobutane column 6 is used to separate the isobutane product.

[0075] According to some preferred embodiments of the present application, the feeding unit includes n-butane raw material feeding device and hydrogen feeding device.

[0076] Preferably, the n-butane raw material feeding device includes a feeding pump 1, and the n-butane raw material is transported into the preheating device by the feeding pump 1 for preheating.

[0077] Preferably, the preheating device includes a heat exchanger 2 and a heater 3,

[0078] The heat exchanger 2 is used to exchange heat between the reaction product from the reactor 4 and the n-butane raw material and hydrogen from the feeding unit, and the heat-exchanged reaction product is fed into the light component separation device 5, and the n-butane raw material and hydrogen are fed into the heater 3.

[0079] The heater 3 is used to heat the n-butane raw material and hydrogen from the heat exchanger 2 to the isomerization reaction temperature, and then fed into the reactor 4.

[0080] The present application will be described in detail below by way of examples.

[0081] The bulk structure of the molecular sieve and the catalyst is analyzed and detected by a Japan Rigaku D / MAX-3A diffractometer (XRD), and the analysis conditions are as follows: ray source CuKα target, Ni filter, scanning range 5°-70°, step width 0.02°.

[0082] The composition of the molecular sieve and the catalyst is characterized and analyzed by an XRF-1800 wavelength dispersion X-ray fluorescence spectrometer, and according to the intensity of the elements existing 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 by theoretical calculation and mathematical correction.

[0083] The zirconium hydroxide powder used is purchased from Changling Catalyst Company, and the zirconium oxide content is 78.5% by weight.

[0084] The all-silica MFI molecular sieve Si-1 used is purchased from Changling Catalyst Co., Ltd., with a silica content of 99.7 mass%, a specific surface area of 444.6 m 2 / g, and XRD characterization as shown in Figure 1 .

[0085] The pseudo-boehmite powder is purchased from Sasol Co., Germany, with an alumina content of 75 mass%.

[0086] The following preparation examples are used to illustrate the preparation of the catalyst in the present application

[0087] Preparation Example 1

[0088] Take 38.2 g of zirconium hydroxide powder and 4.4 g of all-silica MFI molecular sieve Si-1, mix uniformly, add 48.0 g of 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.

[0089] Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix uniformly with 14.4 g of pseudo-boehmite powder, gelatinize with 5.0 mass% nitric acid aqueous solution, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1, uniformly knead and extrude into strips, dry the wet strips at 120°C for 10 h and calcine at 680°C for 4 h to obtain catalyst A1. The XRD characterization results of catalyst A1 are shown in Figure 2 , and the characteristic peaks of the all-silica MFI molecular sieve can be seen in Figure 2 ; the composition and physicochemical properties of the catalyst are shown in Table 1 and Table 1-continued.

[0090] Preparation Example 2

[0091] Take 38.2 g of zirconium hydroxide powder and 7.8 g of all-silica MFI molecular sieve, mix uniformly, add 48.0 g of 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.

[0092] Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix uniformly with 10.6 g of pseudo-boehmite powder, gelatinize with 5.0 mass% nitric acid aqueous solution, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.5:1, uniformly knead and extrude into strips, dry the wet strips at 120°C for 10 h and calcine at 680°C for 4 h to obtain catalyst A2. The XRD characterization results of catalyst A2 are shown in Figure 2 , and the composition and physicochemical properties are shown in Table 1 and Table 1-continued.

[0093] Preparation Example 3

[0094] Take 38.2 g of zirconium hydroxide powder and 14.3 g of all-silica MFI molecular sieve, mix uniformly, add 48.0 g of 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.

[0095] Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix uniformly with 3.4 g of pseudoboehmite powder, gelatinize with 5.0 mass% nitric acid aqueous solution, the ratio of the mass of the nitric acid aqueous solution to the total mass of the fine powder and the aluminum oxide precursor being 0.7:1, uniformly knead and then extrude into strips, dry the wet strips at 120°C for 10 h and calcine at 680°C for 4 h to obtain catalyst A3. The XRD characterization results of catalyst A3 are shown in Figure 2 , and the composition and physicochemical properties are shown in Table 1 and Table 1-Continued.

[0096] Preparation Example 4

[0097] According to the method of Preparation Example 2, except that the amount of all-silica MFI molecular sieve Si-1 is 21 g. The obtained catalyst is recorded as A4, and the composition and physicochemical properties are shown in Table 1 and Table 1-Continued.

[0098] Preparation Example 5

[0099] Take 38.2 g of zirconium hydroxide powder, add 48.0 g of 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.

[0100] Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, add 7.8 g of all-silica MFI molecular sieve and 10.6 g of pseudoboehmite powder to it, mix uniformly, gelatinize with 5.0 mass% nitric acid aqueous solution, the ratio of the mass of the nitric acid aqueous solution to the total mass of the fine powder and the aluminum oxide precursor being 0.6:1, uniformly knead and then extrude into strips, dry the wet strips at 120°C for 10 h and calcine at 680°C for 4 h to obtain catalyst A5. The composition and physicochemical properties of A5 are shown in Table 1 and Table 1-Continued.

[0101] Preparation Example 6

[0102] Take 38.2 g of zirconium hydroxide powder and 6.0 g of all-silica MFI molecular sieve Si-1, mix uniformly, add 48.0 g of 3 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.

[0103] The dried solid was ground into fine powder, which was mixed with 16.6 g of pseudo-boehmite powder, and then was added with nitric acid aqueous solution with a concentration of 5.0% by mass to peptize, the mass ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1, and then was uniformly kneaded and extruded into a wet strip, which was dried at 120 ℃ for 10 h and calcined at 680 ℃ for 4 h to prepare catalyst DA1. The XRD characterization results of catalyst DA1 are shown in FIG. 2.

[0104] Comparative Preparation Example 1

[0105] 38.2 g of zirconium hydroxide powder was taken and was impregnated with 48.0 g of sulfuric acid aqueous solution with a concentration of 5% by mass at 40 ℃ for 4 h, and then the impregnated solid was dried at 60 ℃ for 12 h and at 120 ℃ for 12 h.

[0106] The dried solid was ground into fine powder, which was mixed with 16.6 g of pseudo-boehmite powder, and then was added with nitric acid aqueous solution with a concentration of 5.0% by mass to peptize, the mass ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1, and then was uniformly kneaded and extruded into a wet strip, which was dried at 120 ℃ for 10 h and calcined at 680 ℃ for 4 h to prepare catalyst DA1. The XRD characterization results of catalyst DA1 are shown in FIG. 2. Figure 2 As can be seen, catalyst DA1 does not contain the characteristic peaks of the all-silica MFI molecular sieve Si-1. The composition and physicochemical properties of catalyst DA1 are shown in Table 1 and Table 1-Continued.

[0107] Comparative Preparation Example 2

[0108] 38.2 g of zirconium hydroxide powder and 18.0 g of all-silica MFI molecular sieve were uniformly mixed, and then were impregnated with 48.0 g of sulfuric acid aqueous solution with a concentration of 5% by mass at 40 ℃ for 4 h, and then the impregnated solid was dried at 60 ℃ for 12 h and at 120 ℃ for 12 h.

[0109] The dried solid was ground into fine powder, which was mixed with 16.6 g of pseudo-boehmite powder, and then was added with nitric acid aqueous solution with a concentration of 5.0% by mass to peptize, the mass ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1, and then was uniformly kneaded and extruded into a wet strip, which was dried at 120 ℃ for 10 h and calcined at 680 ℃ for 4 h to prepare catalyst DA1. The XRD characterization results of catalyst DA1 are shown in FIG. 2.

[0110] Comparative Preparation Example 3

[0111] According to the method of Preparation Example 2, except that an equal mass of ZSM-5 molecular sieve (denoted as Si-2, produced by Changling Catalyst Co., Ltd., with a molar ratio of silicon oxide / alumina of 65, and the XRD characterization results are shown in FIG. 3) was used to replace the all-silica MFI molecular sieve. Figure 1

[0112] ​The catalyst prepared is designated as catalyst DA3, and its composition and physicochemical properties are shown in Table 1 and Table 1-Continued.

[0113] Table 1

[0114]

[0115] Table 1-Continued

[0116]

[0117]

[0118] The following examples are used to illustrate the method for n-butane isomerization reaction provided by the present application

[0119] The n-butane raw material used in the following examples includes 0.02% by mass of propane, 0.66% by mass of isobutane, 98.72% by mass of n-butane, and 0.60% by mass of pentane. The water content is 0.5 ppmw.

[0120] The following examples are carried out using an isomerization reaction system as shown in Figure 3 The reaction system includes a feed unit, a preheating device, a reactor 4, a light component separation device 5, and a de-isobutane column 6, as shown in Figure 3 The feed unit includes a n-butane raw material supply device and a hydrogen supply device, the n-butane raw material supply device includes a feed pump 1, and the preheating device includes a heat exchanger 2 and a heater 3. The reactor 4 is packed with catalyst, and the packing and reaction conditions are shown in Table 2 and Table 3.

[0121] The n-butane raw material is fed into the feed pipeline through the feed pump 1, mixed with hydrogen, heated to the reaction temperature in sequence through the heat exchanger 2 and the heater 3, and then fed into the reactor 4 to contact with the catalyst for isomerization reaction. The obtained reaction product is fed into the heat exchanger 2 to exchange heat with the mixed raw material of isobutane raw material and hydrogen, and the heat-exchanged reaction product is fed into the light component separation device 5. The light components, which are C1-C3 hydrocarbons and a small amount of H2, are separated at the top, and the C4 + hydrocarbons separated at the bottom are fed into the de-isobutane column 6 for separation. The isobutane product is separated at the top, and a small amount of C5 + heavy components are separated at the bottom, and the n-butane is extracted through a side line and recycled back to the feed unit. The product sampling and analysis method: a bypass is provided on the main pipeline at the outlet of the reactor 4, and a sampling port is provided on the bypass. When sampling, a sampling cylinder is connected to the sampling port through a quick connector, then the valves before and after the sampling cylinder are opened, the sampling cylinder is replaced with the product, after replacement is completed, the outlet valve of the sampling cylinder is closed, after a certain amount of material to be analyzed is filled, the inlet valve is closed, the quick connector is disconnected, and the sampling is completed. The sample is sent to the laboratory for analysis of the composition of the reactor outlet product, and the analysis results after 10 hours of reaction are shown in Table 2 and Table 3.

[0122] wherein the n-butane conversion rate (%) = ((mass of n-butane in raw material - mass of n-butane in product) / mass of n-butane in raw material) x 100%;

[0123] the isobutane selectivity (%) = ((mass of isobutane in product - mass of isobutane in raw material) / (mass of n-butane in raw material - mass of n-butane in product)) x 100%;

[0124] the isobutane yield (%) = ((mass of isobutane in product - mass of isobutane in raw material) / mass of n-butane in raw material) x 100%.

[0125] Table 2

[0126]

[0127] Table 3

[0128]

[0129]

[0130] As can be seen from the results in Table 2 and Table 3, the method for n-butane isomerization reaction provided by the present application has both high n-butane conversion rate and isobutane selectivity; preferably, the method has even more excellent isobutane yield under the condition of low temperature and low hydrogen hydrocarbon ratio.

[0131] The above describes preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A method for the isomerization reaction of n-butane, characterized in that, The method includes: contacting n-butane feedstock with a catalyst under hydrogen-exposed conditions and under isomerization reaction conditions; The catalyst includes the acidic active component SO4. 2- / ZrO2, an all-silica molecular sieve with an MFI structure, and alumina; the mass ratio of the acidic active component, calculated as ZrO2, to the mass ratio of the all-silica molecular sieve, calculated as SiO2, is 1:(0.1-1). In the catalyst, the density of strong acid centers is 0.5-1.5 μmol / m³. 2 .

2. The method according to claim 1, wherein, The isomerization reaction conditions include: a reaction temperature of 165-240℃; a pressure of 1-4 MPa; and a mass hourly space velocity (HHSV) of 0.5-10 h⁻¹ for the n-butane feedstock. -1 The hydrogen / hydrocarbon molar ratio is 0.02-0.

3.

3. The method according to claim 2, wherein, The isomerization reaction conditions include: a reaction temperature of 175-225℃; a pressure of 1.5-3.5 MPa; and a mass hourly space velocity (HHSV) of 1-5 h⁻¹ for the n-butane feedstock. -1 The hydrogen / hydrocarbon molar ratio is 0.03-0.

2.

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

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

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 n-butane feedstock includes n-butane and optional impurity components.

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

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

17. The method according to claim 16, wherein, The n-butane raw material contains 95-100 wt% n-butane.

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

19. The method according to claim 18, wherein, The content of C1-C3 alkanes in the n-butane feedstock is less than 1 wt%.

20. The method according to claim 19, wherein, The content of C1-C3 alkanes in the n-butane feedstock is less than 0.5 wt%.

21. The method according to claim 18, wherein, The isobutane content in the n-butane feedstock is less than 2 wt%.

22. The method according to claim 21, wherein, The isobutane content in the n-butane feedstock is less than 1 wt%.

23. The method according to claim 18, wherein, The content of C5+ alkanes in the n-butane feedstock is less than 1.5 wt%.

24. The method according to claim 23, wherein, The content of C5+ alkanes in the n-butane feedstock is less than 1 wt%.

25. The method according to claim 18, wherein, The water content in the n-butane feedstock is less than 5 ppmw.

26. The method of claim 25, wherein, The water content in the n-butane feedstock is less than 3 ppmw.

27. The method according to claim 18, wherein, The sulfur content in the n-butane feedstock is less than 10 ppmw.

28. The method according to claim 27, wherein, The sulfur content in the n-butane feedstock is less than 5 ppmw.

29. The method according to claim 1, wherein, The method further includes: preheating the n-butane feedstock and hydrogen to the isomerization reaction temperature before contacting them with the catalyst.

30. The method according to claim 29, wherein, The preheating includes primary preheating and secondary preheating. The primary preheating method includes exchanging heat between the product of the isomerization reaction and the n-butane feedstock and / or hydrogen.

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

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