Method for isomerization reaction of n-butane

Abstract

The present invention relates to the technical field of n-butane isomerization, and discloses an n-butane isomerization reaction method, which comprises: contacting an n-butane raw material with a catalyst under a hydrogen condition and an isomerization reaction condition, wherein the catalyst comprises an acidic active component SO4 < 2-> / ZrO2, an all-silicon molecular sieve with an MFI structure and aluminum oxide; the ratio of the mass of the acidic active component in terms of ZrO2 to the mass of the all-silicon molecular sieve in terms of SiO2 is 1: (0.1-1). The method is mild in condition and environment-friendly, and has relatively high n-butane one-way conversion rate and isobutane selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of n-butane isomerization, and in particular to a method for n-butane isomerization reaction. Background Art

[0002] Isobutane is an important light hydrocarbon resource. In recent years, with the construction of domestic isobutane-butene alkylation, isobutane dehydrogenation, and isobutane-propylene co-oxidation units, isobutane resources have become increasingly scarce. With the continuous upgrading of my country's gasoline standards, isobutane-butene alkylation, as one of the indispensable technologies for gasoline upgrading, will further increase its production capacity. N-butane isomerization is a technology dedicated to the production of isobutane, which can efficiently convert n-butane in C4 resources into isobutane. Therefore, the development of n-butane isomerization technology is of great practical significance for increasing the production of isobutane and achieving the optimal utilization of C4 resources.

[0003] 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 / Al 2 O 3 -Cl) catalyst, and the other is a Pt or Pd-loaded zeolite molecular sieve (Pt(Pd) / zeolite) catalyst. 2 O 3 -Cl catalyst has the advantages of low reaction temperature and high single-pass conversion rate, but the disadvantage is that the catalyst is sensitive to raw material impurities, and the raw materials need to be strictly refined to remove impurities such as sulfur and water. During the isomerization reaction, chlorine needs to be continuously injected to maintain the activity of the catalyst, and the catalyst cannot be regenerated, which further limits the application of this technology. Pt (Pd) / zeolite catalyst has relatively loose requirements on impurities in the raw materials, but the isomerization activity and selectivity of n-butane are relatively low.

[0004] Solid superacid catalyst is a new type of catalyst developed in recent years. CN109265308A discloses a production method of n-butane isomerization using a solid acid bifunctional catalyst, CuGa-SO 4 2- / ZrO 2 ,NiGa-SO 4 2- / ZrO 2 、PtGa-SO 4 2- / ZrO 2 、PbGa-SO 4 2- / ZrO 2At least one of the catalysts is used. Under the conditions of pressure of 1.5-3.0 MPa, reactor inlet temperature of 200-250°C, hydrogen-to-hydrocarbon volume ratio of 1-5, and n-butane mass space velocity of 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 sulfated zirconium oxide type n-butane isomerization catalyst and its use method. When the catalyst is used for n-butane isomerization reaction, at 220°C, 2.0 MPa, and feed mass space velocity of 2.0 h -1 Under the conditions of 37.8% to 11.7% hydrogen / hydrocarbon molecular ratio, the isomerization rate of n-butane is as high as 39.7%.

[0005] The n-butane isomerization method based on sulfated zirconium oxide type solid superacid catalyst disclosed in the prior art is difficult to balance the space velocity and conversion rate, resulting in low n-butane conversion efficiency. In addition, the reaction hydrogen-hydrocarbon ratio is relatively high. In actual application, hydrogen needs to be separated from the reaction product and circulated using a circulating hydrogen compressor, which has a complicated process flow, high equipment investment, and significantly increased energy consumption and operating costs. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of the prior art n-butane isomerization method, such as difficulty in taking both high space velocity and high conversion rate into account, complicated process flow and high cost, and to provide a method for n-butane isomerization reaction, which has high n-butane conversion efficiency and high isobutane yield.

[0007] In order to achieve the above object, the present invention provides a method for isomerization of n-butane, the method comprising: contacting n-butane raw material with a catalyst under hydrogen conditions and under isomerization reaction conditions;

[0008] Wherein, the catalyst comprises an acidic active component SO 4 2- / ZrO 2 , all-silicon molecular sieves with MFI structure and alumina; ZrO 2 The mass of the acidic active component measured in terms of SiO 2 The mass ratio of the all-silicon molecular sieve is 1:(0.1-1).

[0009] Preferably, the isomerization reaction conditions include: reaction temperature of 165-240°C, preferably 175-225°C; pressure of 1-4MPa, preferably 1.5-3.5MPa; mass space velocity of n-butane raw material of 0.5-10h -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.

[0010] The n-butane isomerization method provided by the present invention uses sulfated zirconium oxide modified with all-silicon MFI structure molecular sieve as a catalyst. The method has mild conditions, is environmentally friendly, and has a high n-butane single-pass conversion rate and isobutane selectivity. The n-butane can be used to increase the production of isobutane, provide raw materials for alkylation, isobutane dehydrogenation, C3 / C4 mixed dehydrogenation, PO / MTBE and other devices, and realize the value-added utilization of butane resources. Preferably, the method can efficiently isomerize n-butane to isobutane under the reaction conditions of lower temperature, lower hydrogen-to-oil ratio and higher space velocity, which is conducive to reducing energy consumption and reducing process costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is the XRD spectra of the all-silicon MFI molecular sieve (Si-1) and the ZSM-5 molecular sieve (Si-2) used in the preparation examples of the present invention;

[0012] Figure 2 is the XRD spectra of the catalysts prepared in Preparation Examples 1-3 of the present invention and Comparative Preparation Example 1;

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

[0014] Description of Reference Numerals

[0015] 1 Feed pump 2 Heat exchanger 3 Heater

[0016] 4 Reactor 5 Light component separation unit 6 Deisobutanizer DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

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

[0019] Wherein, the catalyst comprises an acidic active component SO 4 2- / ZrO 2 , all-silicon molecular sieves with MFI structure and alumina; ZrO 2 The mass of the acidic active component measured in terms of SiO 2The mass ratio of the all-silicon molecular sieve is 1:(0.1-1).

[0020] According to the present invention, the catalyst used in the method for isomerization of n-butane contains an acidic active component SO 4 2- / ZrO 2 , all-silicon molecular sieves with MFI structure and alumina. The inventors of the present invention have found in their research that a small amount of all-silicon molecular sieves and alumina with MFI structure can play a role in adjusting the distribution of strong acid centers of solid acid catalysts, thereby making the catalyst highly active and highly selective. The reason for this is that, on the one hand, the all-silicon molecular sieve with MFI structure has basically no acidity and excellent thermal stability, which can avoid the introduction of new acid centers and optimize the distribution of strong acid centers in zirconium sulfate oxide, which is conducive to the efficient activation and conversion of butane molecules through a single molecule path. On the other hand, the special pore structure of the all-silicon molecular sieve with MFI structure is conducive to the diffusion of reactants and products, thereby effectively avoiding the occurrence of secondary reactions.

[0021] In the solid acid catalyst system in the prior art, molecular sieves are usually used as carriers, and the molecular sieves used as carriers occupy a relatively high content in the catalyst; at the same time, the silicon-aluminum molecular sieve introduced into the catalyst is also usually used to provide additional acidic active centers.

[0022] According to some preferred embodiments of the present invention, the catalyst is ZrO 2 The mass of the acidic active component measured in terms of SiO 2 The mass ratio of the all-silicon molecular sieve 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, etc., which are typical but not limiting mass ratios or ranges therebetween. Preferably, in the catalyst, ZrO 2 The mass of the acidic active component measured in terms of SiO 2 The mass ratio of the all-silicon molecular sieve is 1:(0.15-0.5). Under the above preferred mass ratio conditions, it is beneficial for the catalyst to have a suitable strong acid center density.

[0023] Preferably, in the catalyst, the density of the strong acid center is 0.1-2 μmol / m 2 , preferably 0.5-1.5 μmol / m 2 , for example, 0.5 μmol / m 2 , 0.6μmol / m 2 , 0.7 μmol / m 2 , 0.8 μmol / m 2 , 0.9 μmol / m2 , 1μmol / 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 The above preferred range is conducive to further improving the activity of the isomerization reaction and increasing the isobutane yield.

[0024] In the present invention, the density of the strong acid center is the ratio of the amount of strong acid in the catalyst to the specific surface area. The method for testing the amount of strong acid in the catalyst includes: using a Nicolet 6700 Fourier transform infrared spectrometer produced by Thermo Fisher, USA, with a resolution of 4 cm -1 , scanned 64 times. The sample was pressed into a self-supporting sheet with a diameter of 13 mm, and then placed in a muffle furnace for high-temperature calcination. After completion, it was directly transferred to a dryer for cooling at high temperature. After cooling to room temperature, it was placed in a homemade quartz infrared sample cell, first treated at 400°C for 2 hours under normal pressure flowing air, then cooled to 200°C, vacuum purified for 4 hours, and then cooled to -190°C with liquid nitrogen. The purified CO probe molecules were saturated and adsorbed for 0.5 hours before desorption. The spectra before and after adsorption were subtracted to obtain the infrared spectrum of the sample adsorbed CO. For the wave number of 2050-2250cm -1 The spectrum at 2186cm is processed by peak separation. The spectrum can be divided into four absorption peaks with wave numbers of 2186cm -1 、2167cm -1 、2150cm -1 and 2125cm -1 , where the wave number is 2167cm -1 The absorption peak at is the strong acid center which is directly related to the catalyst performance. The strong acid amount N (in μmol / g) is calculated according to formula (1).

[0025] N=A / (ρA 0 ), formula (1),

[0026] Where A is the integrated area of ​​the absorption peak (in cm -1 ), ρ is the mass of the catalyst support per square centimeter (in g / cm 2 ), A 0 is the molar extinction coefficient for a wave number of 2167 cm -1 The peak of the spectrum, A 0 =2.6cm / μmol.

[0027] In the present invention, the catalyst specific surface area is characterized by low temperature nitrogen static volume adsorption method (BET method), the instrument used is ASAP2400 specific surface measuring instrument produced by Micromeritics Instrument Company, the pretreatment conditions are: 250 ° C, 1.3 Pa, treatment for 4 hours, and the specific surface area (m 2 / g).

[0028] In the present invention, the phase analysis of the catalyst sample is carried out using a Japanese Rigaku D / MAX-3A diffractometer (XRD), and the analysis conditions are: ray source CuKα target, Ni filter, scanning range 5°-70°, step width 0.02°.

[0029] Preferably, the isomerization reaction method provided by the present invention can efficiently convert n-butane into isobutane under the reaction conditions of lower temperature, lower hydrogen-to-oil ratio and higher space velocity. According to some preferred embodiments of the present invention, the isomerization reaction conditions include: reaction temperature of 165-240°C, preferably 175-225°C; pressure of 1-4MPa, preferably 1.5-3.5MPa; mass space velocity of n-butane raw material of 0.5-10h -1 , preferably 1-5h -1 ; The hydrogen / hydrocarbon molar ratio is 0.02-0.3, preferably 0.03-0.2. The above preferred embodiment is conducive to significantly reducing the amount of hydrogen used, which can not only reduce energy consumption and raw material costs, but also reduce the difficulty of post-processing and separation, and the reaction economy is good. 4 2- / ZrO 2 When the isomerization reaction is carried out using an acid-centered catalyst, the hydrogen-to-hydrocarbon molar ratio is usually not less than 1.

[0030] According to some preferred embodiments of the present invention, the catalyst comprises zirconium, silicon, aluminum and sulfur, in the form of zirconium oxide, silicon oxide, aluminum oxide and SO 3 Based on the total mass of the catalyst, the content of zirconium oxide is 30-90wt%, the content of silicon oxide is 1-35wt%, the content of aluminum oxide is 5-50wt%, and the content of SO 3 The content of is 1-10wt%; preferably, based on the total mass of the catalyst, the content of zirconium oxide is 50-80wt%, the content of silicon oxide is 5-30wt%, the content of aluminum oxide is 5-30wt%, SO 3 The content is 2-8wt%. Under the above preferred composition, it is beneficial to improve the thermal stability of tetragonal zirconium oxide and the specific surface area of ​​the catalyst, so that the catalyst has a suitable strong acid center distribution and active center accessibility, and further improves the conversion rate of n-butane and the selectivity of isobutane.

[0031] Preferably, SO 3 With ZrO 2 The mass ratio is (0.02-0.12):1, preferably (0.03-0.08):1.

[0032] In the present invention, the catalyst composition is characterized and analyzed using an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer, and the content of each element in the sample is obtained through theoretical calculation and mathematical correction 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.

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

[0034] According to some preferred embodiments of the present invention, the aluminum oxide is γ-Al 2 O 3 In the above preferred case, it is beneficial to improve the thermal stability and specific surface area of ​​the catalyst.

[0035] In the present 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, pellets, sheets, particles or microspheres, suitable for fixed bed, moving bed or fluidized bed reactions.

[0036] According to some preferred embodiments of the present invention, the method for preparing the catalyst comprises:

[0037] (1) mixing an all-silicon molecular sieve having an MFI structure and zirconium hydroxide to obtain a mixture;

[0038] Among them, ZrO 2 The zirconium hydroxide and SiO 2 The mass ratio of the all-silicon molecular sieve is 1:(0.1-1);

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

[0040] (3) The product obtained in step (2), an alumina precursor and an optional peptizing agent are mixed, and then molded and calcined.

[0041] According to the present invention, the above-mentioned preparation method can make the all-silicon molecular sieve with MFI structure evenly distributed in the catalyst without blocking the catalyst pores, and the density of the strong acid center in the sulfated zirconium oxide is reduced without introducing new acid centers. 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 molecule path, so that the catalyst simultaneously exhibits high activity and high selectivity in the butane isomerization reaction.

[0042] The present invention has a wide selection range for the number of pores and the pore structure of the all-silicon molecular sieve, and any all-silicon molecular sieve with an MFI structure can be applied to the present invention.

[0043] In some preferred embodiments, the specific surface area of ​​the all-silicon molecular sieve is 400-500m 2 / g, preferably 420-460m 2 In the above preferred case, it is beneficial to further optimize the density of the strong acid center in the sulfated zirconium oxide, improve the uniformity of the strong acid site, and thus improve the normal isomerization activity.

[0044] According to some preferred embodiments of the present invention, ZrO 2 The zirconium hydroxide and SiO 2 The mass ratio of the all-silicon molecular sieve is 1:(0.15-0.5).

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

[0046] The present invention has no particular limitation on the specific operating conditions of the contact, as long as the catalyst composition range described above is met, and those skilled in the art can make the selection according to actual needs.

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

[0048] The present invention has a wide range of selection for the specific type of the solution containing sulfate radicals. Preferably, the solution containing sulfate radicals is 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 above preferred embodiment is conducive to obtaining a suitable SO 3 content and strong acid center density.

[0050] The present invention has no particular limitation on the amount of the solution containing sulfate, as long as the SO in the catalyst described in the first aspect is met. 3 The content range requirement is sufficient, and those skilled in the art can select 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 invention, after the contacting in step (2), an optional drying and grinding step is further included. The drying temperature may be 50-150° C., and the drying time may be 3-100 hours. The grinding is used to grind the dried solid into a powder of 100-300 meshes, which is beneficial to improve the crushing strength of the catalyst in the above preferred case.

[0052] In the present invention, 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 pseudo-boehmite and / or gibbsite, preferably pseudo-boehmite. In the above preferred case, it is beneficial to improve the thermal stability and crushing strength of the catalyst.

[0053] In the present invention, the molding in step (3) can be carried out by conventional methods and conditions in the art, and the present invention has no particular limitation thereto. The molding method can be selected according to the actual application needs, for example, it can be selected from any one of extrusion molding, granulation molding, ball rolling molding and spray drying spheronization, preferably 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 invention, the total mass ratio of the peptizing agent to the product obtained in step (2) to the alumina precursor is 0.3-1:1, preferably 0.4-0.8:1.

[0055] According to some preferred embodiments of the present invention, the peptizing agent is an aqueous solution of an acid, preferably an aqueous solution of at least one selected from nitric acid, acetic acid, citric acid, oxalic acid and formic acid.

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

[0057] According to some preferred embodiments of the present invention, in step (3), the calcination temperature is 600-850° C., preferably 650-850° C., and the calcination time is 1-20 hours, preferably 3-12 hours. Under the above preferred calcination temperature conditions, it is beneficial to form a strong acid center with a suitable density, which is beneficial to improve the activity and selectivity of the catalyst in the butane isomerization reaction.

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

[0059] The present invention has no particular limitation on the source of the n-butane raw material, which includes n-butane and may also include impurity components. Preferably, the content of n-butane in the n-butane raw material is not less than 80wt%, preferably not less than 90wt%, and more preferably 95-100wt%.

[0060] Preferably, the impurity component is selected from at least one of C1-C3 alkanes, isobutane, C5+ alkanes, water and sulfur.

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

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

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

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

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

[0066] According to some preferred embodiments of the present invention, the method further comprises: preheating the n-butane raw material and hydrogen to the isomerization reaction temperature, and then contacting with the catalyst. In the present invention, the n-butane raw material and hydrogen can be preheated separately, or the n-butane raw material and hydrogen can be mixed and then preheated together. From the perspective of economy, it is preferred to mix the n-butane raw material and hydrogen and then preheat them together.

[0067] Preferably, the preheating includes primary preheating and secondary preheating, and the primary preheating includes: exchanging heat between the product of the isomerization reaction and the n-butane feedstock and / or hydrogen. The primary preheating can be performed using a conventional heat exchange device in the art, such as a shell and tube heat exchanger.

[0068] It is understandable that, when the reaction is initially started, the raw material can be directly heated to the isomerization reaction temperature by secondary preheating, and when the reaction is continuously operated, the n-butane raw material and hydrogen are heat exchanged with the isomerization reaction product by primary preheating, and then the n-butane raw material and hydrogen are further heated to the isomerization reaction temperature by secondary preheating. The above preferred embodiment is conducive to further reducing reaction energy consumption and reducing process costs.

[0069] According to the present invention, preferably, the method further comprises: separating and purifying the contact product, and using the separated n-butane to provide at least part of the n-butane raw material. The separation and purification can be carried out in any manner known in the art, as long as the isobutane product can be separated from the product. Preferably, the separation and purification comprises: separating the contact product by distillation to obtain light components and heavy components, wherein the light components include C1-C3 hydrocarbons and H 2 , the recombinant components include C 4 + hydrocarbons; and then separating the isobutane product from the heavy components through a deisobutanizer.

[0070] According to some preferred embodiments of the present invention, 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 deisobutanizer 6;

[0071] The feed unit is connected to the feed 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 connected to the feed port of the reactor 4, and the preheated raw materials are fed into the reactor 4 to contact with the catalyst;

[0073] 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 deisobutanizer 6; wherein the light components include C1-C3 hydrocarbons and H 2 , the recombinant components include C 4 + hydrocarbon;

[0074] The deisobutanizer 6 is used to separate the isobutane product.

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

[0076] Preferably, the n-butane raw material supply device comprises a feed pump 1, and the n-butane raw material is transported to the preheating device through the feed pump 1 for preheating.

[0077] Preferably, the preheating device comprises 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 feed unit. The reaction product after heat exchange is sent to the light component separation device 5, and the n-butane raw material and hydrogen are sent to 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 send them into the reactor 4.

[0080] The present invention will be described in detail below through examples.

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

[0082] The composition of molecular sieve and catalyst was characterized and analyzed by XRF-1800 wavelength dispersive X-ray fluorescence spectrometer. The content of each element in the sample was obtained through theoretical calculation and mathematical correction based on the intensity of the elements present in the sample obtained by scanning and the sensitivity of the pure substances of these elements in the instrument.

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

[0084] The all-silicon MFI molecular sieve Si-1 used was purchased from Changling Catalyst Company, with a silicon oxide content of 99.7% by mass and a specific surface area of ​​444.6 m 2 / g, XRD characterization Figure 1 shown.

[0085] Pseudo-boehmite powder was purchased from Sasol, Germany, with an alumina content of 75% by mass.

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

[0087] Preparation Example 1

[0088] Take 38.2g of zirconium hydroxide powder and 4.4g of all-silicon MFI molecular sieve Si-1 and mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40°C for 4h, and dry the impregnated solid at 60°C for 12h and 120°C for 12h.

[0089] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 14.4 g of pseudo-boehmite powder. A nitric acid aqueous solution with a concentration of 5.0 mass % was added for peptization. The ratio of the total mass of the nitric acid aqueous solution to the fine powder and the alumina precursor was 0.6:1. After kneading evenly, the wet strips were extruded into strips. The wet strips were dried at 120°C for 10 hours and calcined at 680°C for 4 hours to obtain catalyst A1. The XRD characterization results of catalyst A1 are shown in Figure 2 ,Depend on Figure 2 The characteristic peaks of all-silicon MFI molecular sieve can be seen in the catalyst; the composition and physicochemical properties of the catalyst are shown in Table 1 and Table 1.

[0090] Preparation Example 2

[0091] Take 38.2g of zirconium hydroxide powder and 7.8g of all-silicon MFI molecular sieve, mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40°C for 4h, and dry the soaked solid at 60°C for 12h and 120°C for 12h.

[0092] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 10.6 g of pseudo-boehmite powder. A nitric acid aqueous solution with a concentration of 5.0 mass % was added for peptization. The ratio of the total mass of the nitric acid aqueous solution to the fine powder and the alumina precursor was 0.5:1. After kneading evenly, the wet strips were extruded into strips. The wet strips were dried at 120°C for 10 hours and calcined at 680°C for 4 hours to obtain catalyst A2. The XRD characterization results of catalyst A2 are shown in Figure 2 The composition and physicochemical properties are shown in Table 1 and Table 1.

[0093] Preparation Example 3

[0094] Take 38.2g of zirconium hydroxide powder and 14.3g of all-silicon MFI molecular sieve, mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40°C for 4h, and dry the soaked solid at 60°C for 12h and 120°C for 12h.

[0095] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 3.4 g of pseudo-boehmite powder. A nitric acid aqueous solution with a concentration of 5.0 mass % was added for peptization. The ratio of the total mass of the nitric acid aqueous solution to the fine powder and the alumina precursor was 0.7:1. After kneading evenly, the wet strips were extruded into strips. The wet strips were dried at 120°C for 10 hours and calcined at 680°C for 4 hours to obtain catalyst A3. The XRD characterization results of catalyst A3 are shown in Figure 2 The composition and physicochemical properties are shown in Table 1 and Table 1.

[0096] Preparation Example 4

[0097] The method of Preparation Example 2 was followed, except that the amount of all-silicon MFI molecular sieve Si-1 used was 21 g. The prepared catalyst was denoted as A4, and the composition and physicochemical properties are shown in Table 1 and Table 1.

[0098] Preparation Example 5

[0099] 38.2 g of zirconium hydroxide powder was taken, 48.0 g of a 5 mass % sulfuric acid aqueous solution was added, and the mixture was immersed at 40° C. for 4 h. The immersed solid was dried at 60° C. for 12 h and 120° C. for 12 h.

[0100] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, 7.8 g of all-silicon MFI molecular sieve and 10.6 g of pseudo-boehmite powder were added thereto, mixed evenly, and 5.0 mass % nitric acid aqueous solution was added for peptization, the ratio of the total mass of the nitric acid aqueous solution to the fine powder and the alumina precursor was 0.6:1, and after kneading evenly, the strips were extruded, and the wet strips were dried at 120°C for 10 hours and calcined at 680°C for 4 hours to obtain catalyst A5. The composition and physicochemical properties of A5 are shown in Table 1 and Table 1.

[0101] Preparation Example 6

[0102] Take 38.2g of zirconium hydroxide powder and 6.0g of all-silicon MFI molecular sieve Si-1, mix them evenly, add 48.0g of 3% by mass sulfuric acid aqueous solution, soak at 40°C for 4h, and dry the impregnated solid at 60°C for 12h and 120°C for 12h.

[0103] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 38.3 g of pseudo-boehmite powder, and peptized by adding a nitric acid aqueous solution with a concentration of 5.0 mass %, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1, and after kneading evenly, extruded into strips, and the wet strips were dried at 120° C. for 10 h and calcined at 630° C. for 4 h to obtain catalyst A6. The composition and physicochemical properties of catalyst A6 are shown in Table 1 and Table 1.

[0104] Comparative Preparation Example 1

[0105] 38.2 g of zirconium hydroxide powder was taken, 48.0 g of a 5 mass % sulfuric acid aqueous solution was added, and the mixture was immersed at 40° C. for 4 h. The immersed solid was dried at 60° C. for 12 h and 120° C. for 12 h.

[0106] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and mixed evenly with 16.6 g of pseudo-boehmite powder. A nitric acid aqueous solution with a concentration of 5.0 mass % was added for peptization. The ratio of the total mass of the nitric acid aqueous solution to the fine powder and the alumina precursor was 0.6:1. After kneading evenly, the wet strips were extruded into strips. The wet strips were dried at 120°C for 10 hours and calcined at 680°C for 4 hours to obtain catalyst DA1. The XRD characterization results of catalyst DA1 are shown in Figure 2 It can be seen that the catalyst DA1 does not contain the characteristic peak of the all-silicon MFI molecular sieve Si-1. The composition and physicochemical properties of the catalyst DA1 are shown in Table 1 and Table 1.

[0107] Comparative Preparation Example 2

[0108] Take 38.2g of zirconium hydroxide powder and 18.0g of all-silicon MFI molecular sieve, mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40°C for 4h, and dry the soaked solid at 60°C for 12h and 120°C for 12h.

[0109] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and peptized with a nitric acid aqueous solution having a concentration of 5.0 mass %, the mass ratio of the nitric acid aqueous solution to the fine powder being 0.6:1, and kneaded evenly to form a strip, and the wet strip was dried at 120° C. for 10 h and calcined at 680° C. for 4 h to obtain catalyst DA2. The composition and physicochemical properties of catalyst DA2 are shown in Table 1 and Table 1.

[0110] Comparative Preparation Example 3

[0111] The method of Preparation Example 2 was followed, except that an equal mass of ZSM-5 molecular sieve (denoted as Si-2, produced by Changling Catalyst Company, with a silicon oxide / aluminum oxide molar ratio of 65, XRD characterization see Figure 1 ) replaces the all-silica MFI molecular sieve.

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

[0113] Table 1

[0114]

[0115] Table 1

[0116]

[0117]

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

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

[0120] The following examples adopt Figure 3 The isomerization reaction system shown is carried out. Figure 3As shown, the reaction system includes: a feed unit, a preheating device, a reactor 4, a light component separation device 5 and a deisobutanizer 6; the feed unit includes a normal butane raw material supply device and a hydrogen supply device, the normal butane raw material supply device includes a feed pump 1, and the preheating device includes a heat exchanger 2 and a heater 3. The catalyst is loaded in the reactor 4, and the loading and reaction conditions are shown in Tables 2 and 3.

[0121] The n-butane raw material is introduced into the feed pipeline through the feed pump 1, mixed with hydrogen, and then heated to the reaction temperature through the heat exchanger 2 and the heater 3 in sequence, and then sent to the reactor 4 to contact with the catalyst for isomerization reaction. The obtained reaction product is sent to the heat exchanger 2 for heat exchange with the mixed raw material of the isobutane raw material and hydrogen. The reaction product after heat exchange is sent to the light component separation device 5, and the light component is separated from the top of the tower, which is C1-C3 hydrocarbons and a small amount of H 2 ; C separated at the bottom of the tower 4 + The hydrocarbons are sent to the deisobutanizer 6 for separation. The isobutane product is separated from the top of the tower, and a small amount of C 5 + Heavy components, side line draw n-butane to circulate back to the feed unit. Product sampling and analysis method: A bypass is provided on the outlet main line of reactor 4, and a sampling port is provided on the bypass. When sampling, the sampling cylinder is connected to the sampling port through a quick connector, and then the valves before and after the sampling cylinder are opened, and the sampling cylinder is replaced with the product. After the replacement is completed, the outlet valve of the sampling cylinder is closed, and after a certain amount of material to be analyzed is filled, the inlet valve is closed, and the quick connector is disconnected, and the sampling is completed. The sample is sent to the laboratory for analysis of the composition of the product at the outlet of the reactor. The analysis results of the reaction for 10 hours are listed in Tables 2 and 3.

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

[0123] Isobutane selectivity (%) = ((mass of isobutane in the product - mass of isobutane in the feed) / (mass of normal butane in the feed - mass of normal butane in the product)) × 100%;

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

[0125] Table 2

[0126]

[0127] Table 3

[0128]

[0129]

[0130] It can be seen from the results of Table 2 and Table 3 that the method for isomerization reaction of n-butane provided by the present invention has both high n-butane conversion rate and isobutane selectivity; preferably, the method has a better isobutane yield under the conditions of low temperature and low hydrogen-to-hydrocarbon ratio.

[0131] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for isomerization of n-butane, characterized in that: The method comprises: contacting a normal butane raw material with a catalyst under hydrogenation conditions and under isomerization reaction conditions; Wherein, the catalyst includes an acidic active component SO4 2- / ZrO2, an all-silicon 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-silicon molecular sieve calculated as SiO2 is 1:(0.1-1).

2. The method according to claim 1, wherein: The isomerization reaction conditions include: reaction temperature of 165-240°C, preferably 175-225°C; pressure of 1-4MPa, preferably 1.5-3.5MPa; mass space velocity of n-butane raw material of 0.5-10h -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.

3. The method according to claim 1 or 2, wherein: In the catalyst, the density of the strong acid center is 0.1-2 μmol / m 2 , preferably 0.5-1.5 μmol / m 2 .

4. The method according to any one of claims 1 to 3, wherein: In the catalyst, the mass ratio of the acidic active component calculated as ZrO2 to the mass ratio of the all-silicon molecular sieve calculated as SiO2 is 1:(0.15-0.5).

5. The method according to any one of claims 1 to 4, wherein: The catalyst includes zirconium, silicon, aluminum and sulfur, calculated as zirconium oxide, silicon oxide, aluminum oxide and SO3 respectively. Based on the total mass of the catalyst, the content of zirconium oxide is 30-90wt%, the content of silicon oxide is 1-35wt%, the content of aluminum oxide is 5-50wt%, and the content of SO3 is 1-10wt%; preferably, based on the total mass of the catalyst, the content of zirconium oxide is 50-80wt%, the content of silicon oxide is 5-30wt%, the content of aluminum oxide is 5-30wt%, and the content of SO3 is 2-8wt%.

6. The method according to claim 5, wherein: The mass ratio of SO3 to ZrO2 is (0.02-0.12):1, preferably (0.03-0.08):

1.

7. The method according to any one of claims 1 to 6, wherein: The specific surface area of ​​the catalyst is 80-180m 2 / g, preferably 90-160m 2 / g, more preferably 100-150m 2 / g; Preferably, the aluminum oxide is γ-Al2O3.

8. The method according to any one of claims 1 to 7, wherein: The n-butane raw material includes n-butane and optional impurity components; Preferably, the content of n-butane in the n-butane raw material is not less than 80wt%, preferably not less than 90wt%, more preferably 95-100wt%; Preferably, the impurity component is selected from at least one of C1-C3 alkanes, isobutane, C5+ alkanes, water and sulfur; Preferably, the content of C1-C3 alkanes in the n-butane raw material is less than 1wt%, preferably less than 0.5wt%; Preferably, the content of isobutane in the n-butane raw material is less than 2 wt%, preferably less than 1 wt%; Preferably, the content of C5+ alkanes in the n-butane raw material is less than 1.5wt%, preferably less than 1wt%; Preferably, the water content in the n-butane feedstock is less than 5 ppmw, preferably less than 3 ppmw; Preferably, the sulfur content in the n-butane raw material is less than 10 ppmw, preferably less than 5 ppmw.

9. The method according to any one of claims 1 to 8, wherein: The method further comprises: preheating the n-butane raw material and hydrogen to an isomerization reaction temperature, and then contacting with the catalyst; Preferably, the preheating includes primary preheating and secondary preheating, and the primary preheating includes: exchanging heat between the product of the isomerization reaction and the n-butane feedstock and / or hydrogen.

10. The method according to any one of claims 1 to 9, wherein: The method further comprises: separating and purifying the contact product, and using the separated n-butane to provide at least part of the n-butane raw material.

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