Method for preparing n-butane from iso-butane

Abstract

The invention relates to the technical field of preparation of n-butane, and discloses a method for preparing n-butane from iso-butane, and the method comprises the following steps: contacting an iso-butane raw material with a catalyst under a hydrogen condition and a normalizing reaction condition, wherein the catalyst comprises an active substrate and an active metal component loaded on the active substrate; wherein the active matrix comprises an acidic active component SO4 < 2-> / ZrO2, an all-silicon molecular sieve with an MFI structure and aluminum oxide; the active metal component is selected from at least one of noble metal elements; wherein in the catalyst, the density of the strong acid center is 0.1-1 [mu] mol / m < 2 >. The method is mild in condition and environment-friendly, has higher isobutane conversion per pass and n-butane selectivity, can increase the yield of n-butane by using isobutane, provides high-quality raw materials for an ethylene cracking device and a device for preparing maleic anhydride by using a butane oxidation method, and realizes value-added utilization of butane resources.

Description

Technical Field

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

[0002] n-Butane is a high-quality raw material for ethylene cracking and a raw material for the production of maleic anhydride by oxidation. Increasing the production of n-butane has become an important option to make up for the shortage of raw materials for ethylene cracking. In addition, since biodegradable plastics mainly use maleic anhydride as a raw material, the demand for maleic anhydride and its upstream n-butane has surged. In my country, n-butane is mainly found in mixed butanes produced as by-products of petroleum refining processes such as catalytic cracking and hydrocracking. For example, the n-butane content in catalytic cracking by-product butane is usually 40%, and the rest is isobutane. For chemical refineries without alkylation units, isobutane is usually treated as a low value-added product. Therefore, the development of isobutane normalization technology and the increase in the production of n-butane, which is urgently needed in the market, are of great significance for improving the economic benefits of refineries and helping refineries transform to the chemical industry.

[0003] Normalization of isobutane is an acid-catalyzed reaction. The normalization methods of isobutane disclosed in the prior art use normalization catalysts with two main types of acid centers: one is chloride and the other is SO4 2- / ZrO2. CN104892339A discloses a method for preparing normal butane from isobutane, wherein isobutane-rich carbon four hydrocarbons are fed into a normalization reaction zone, isobutane is converted into normal butane under the action of a catalyst, and then the reaction product is fed into a hydrogenation saturation zone for hydrogenation reaction, the olefins in the reaction product are hydrogenated and saturated, and the hydrogenated logistics is fed into a separation unit to be separated into normal butane products, light components and isobutane, and the isobutane is recycled back to the normalization zone for reaction. The normalization reaction temperature described in the invention is 200-700°C, the operating pressure is 2-5MPa, the molar ratio of the total hydrogen content to the isobutane in the feed is 1-3:1, and the catalyst used comprises a carrier, an active component and an acidic component, the active component is composed of one or more transition group VIII elements, and the acidic component is a chloride. CN110385142A discloses a catalyst for normalization reaction of isobutane and a preparation method thereof. The catalyst uses MCM-41 molecular sieve as carrier and Pt / SO4 2- / ZrO2 is the active component, and the temperature for the normalization reaction of isobutane is 150-350℃, the pressure is 1.5-4.5MPa, and the mass space velocity of isobutane is 0.5-3.0h -1 The volume ratio of hydrogen to isobutane feed is 200: 1. The yield of n-butane in this method is less than 22.1%.

[0004] It can be seen that in the prior art, when the isobutane normalization catalyst uses chloride as the acid center, the normalization reaction temperature is high, the dehydrogenation side reaction is difficult to avoid, the reaction product contains more olefins, and a hydrogenation saturation unit is required to hydrogenate and saturate the olefins in the reaction product, the process flow is complicated, and the energy consumption is high. 2- When / ZrO2 is the acid center, although the normalization reaction temperature is reduced, the single-pass conversion rate of the reaction is low, and the yield of n-butane is low. It is necessary to separate a large amount of unconverted isobutane in the product, and the separation energy consumption is high. In addition, the reaction hydrogen-hydrocarbon ratio is relatively high. In actual application, it is necessary to separate hydrogen from the reaction product and circulate it using a circulating hydrogen compressor, which further increases energy consumption and operating costs. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of low isobutane conversion rate, low n-butane yield and poor stability in the isobutane normalization reaction in the prior art, and to provide a method for preparing n-butane from isobutane. The method has high isobutane single-pass conversion rate and n-butane selectivity, high n-butane yield and good stability.

[0006] In order to achieve the above object, the present invention provides a method for preparing normal butane from isobutane, the method comprising: contacting the isobutane raw material with a catalyst under hydrogenation conditions and normalization reaction conditions;

[0007] Wherein, the catalyst comprises an active matrix and an active metal component supported on the active matrix;

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

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

[0010] Preferably, the reaction conditions for normalization of isobutane include: reaction temperature of 150-250°C, preferably 180-230°C; pressure of 1-4MPa, preferably 1.5-3.5MPa; mass space velocity of isobutane 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.

[0011] The method for preparing normal butane from isobutane provided by the present invention uses sulfated zirconium oxide modified with all-silicon MFI structure molecular sieve as an active matrix, so that the catalyst has a suitable density of strong acid centers, and further cooperates with precious metals to provide strong acid centers and weak acid centers respectively. The catalyst is used in the normalization reaction of isobutane, and can efficiently convert isobutane into normal butane under the reaction conditions of lower temperature, lower hydrogen-to-oil ratio and higher space velocity. The method has mild conditions, is environmentally friendly, and has a high isobutane single-pass conversion rate and normal butane selectivity. Isobutane can be used to increase the production of normal butane, provide high-quality raw materials for ethylene cracking devices and butane oxidation process maleic anhydride devices, and realize the value-added utilization of butane resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 1 is the XRD spectra of the all-silicon MFI molecular sieve (Si-1), ZSM-5 molecular sieve (Si-2) and MCM-41 (Si-3) used in the examples and comparative examples of the present invention;

[0013] Figure 2 is the XRD spectra of the active matrix prepared in Preparation Examples 1-3 of the present invention and Comparative Preparation Example 1;

[0014] Figure 3 It is a schematic diagram of an isobutane normalization reaction system in one embodiment of the present invention.

[0015] Description of Reference Numerals

[0016] 1 Feed pump 2 Heat exchanger 3 Heater

[0017] 4 Reactor 5 Light component separation unit 6 Deisobutanizer DETAILED DESCRIPTION

[0018] 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.

[0019] The present invention provides a method for preparing normal butane from isobutane, the method comprising: contacting the isobutane raw material with a catalyst under hydrogenation conditions and normalization reaction conditions;

[0020] Wherein, the catalyst comprises an active matrix and an active metal component supported on the active matrix;

[0021] Wherein, the active matrix includes the acidic active component SO4 2- / ZrO2, an all-silicon molecular sieve having an MFI structure, and alumina; the active metal component is selected from at least one of the noble metal elements;

[0022] Wherein, in the catalyst, the density of the strong acid center is 0.1-1 μmol / m 2 .

[0023] 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°.

[0024] 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.

[0025] The catalyst used in the method for preparing normal butane from isobutane provided by the present invention has a suitable density of strong acid centers, while the density of strong acid centers in the super strong solid acid sulfate zirconium oxide in the prior art is relatively high, generally higher than 2 μmol / m 2 The inventors of the present invention have found in their research that a high density of strong acid centers is detrimental to the normal isomerization selectivity of the catalyst.

[0026] According to the present invention, a small amount of all-silicon molecular sieve and alumina with an MFI structure can play a role in adjusting the distribution of strong acid centers of the solid acid catalyst, so that the catalyst has higher positive isomerization activity and selectivity. Furthermore, the noble metal component and the sulfated zirconium oxide in the active matrix act synergistically, and the stability of the catalyst can be improved through the joint action of the strong acid center and the weak acid center. The reason is that the all-silicon molecular sieve with an MFI structure has a special pore structure, is basically free of acidity, and has excellent thermal stability, which helps to optimize the distribution of strong acid centers in the sulfated zirconium oxide, is conducive to the efficient activation and conversion of light hydrocarbon molecules through a single molecule path, is conducive to the diffusion of reactants and products, and thus effectively avoids the occurrence of secondary reactions.

[0027] According to some preferred embodiments of the present invention, the density of the strong acid center in the catalyst is 0.2-0.7 μmol / m 2 For example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 μmol / m 2 In the above preferred case, it is beneficial to further improve the activity and selectivity of the catalyst in the normal isomerization reaction of light hydrocarbons.

[0028] In the present invention, the density of the strong acid center is the ratio of the amount of strong acid in the catalyst to the specific surface area. The method for testing the amount of acid in the catalyst includes: using a Nicolet 6700 Fourier transform infrared spectrometer produced by Thermo Fisher, USA, with a resolution of 4 cm -1 , scanned 64 times. The sample was pressed into a self-supporting sheet with a diameter of 13 mm, and then placed in a muffle furnace for high-temperature calcination. After completion, it was directly transferred to a dryer for cooling at high temperature. After cooling to room temperature, it was placed in a homemade quartz infrared sample cell, first treated at 400°C for 2 hours under normal pressure flowing air, then cooled to 200°C, vacuum purified for 4 hours, and then cooled to -190°C with liquid nitrogen. The purified CO probe molecules were saturated and adsorbed for 0.5 hours before desorption. The spectra before and after adsorption were subtracted to obtain the infrared spectrum of 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 2150 cm is a strong acid center directly related to the catalyst performance. -1 The absorption peak at is the weak acid center of the catalyst. The acid amount N (in μmol / g) is calculated according to formula (1).

[0029] N=A / (ρA0), formula (1),

[0030] Where A is the integrated area of ​​the absorption peak (in cm -1 ), ρ is the mass of the catalyst support per square centimeter (in g / cm 2 ), A0 is the molar extinction coefficient, for a wave number of 2167 cm -1 and 2150cm -1 The spectral peak is A0=2.6cm / μmol.

[0031] 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).

[0032] According to some preferred embodiments of the present invention, in the catalyst, the molar ratio of the strong acid to the weak acid is 4-8:1, for example, it can be 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1 and other typical but non-limiting molar ratios. Preferably, it is 4.5-6.8:1. In the above preferred case, it is conducive to further improving the stability of the catalyst.

[0033] According to some preferred embodiments of the present invention, the active metal component is selected from at least one of Pt, Pd, Ru and Rh, preferably Pt and / or Pd.

[0034] In the present invention, the active metal component exists in the form of oxide and / or metal. Preferably, at least part of the active metal component exists in the form of metal.

[0035] According to some preferred embodiments of the present invention, based on the total mass of the catalyst, the content of the active matrix is ​​99-99.95wt%, preferably 99.5-99.9wt%; calculated as an element, the content of the active metal component is 0.05-1wt%, preferably 0.1-0.5wt%.

[0036] In the present invention, the content of active metal components in the catalyst is determined by Lambda 35 UV-Vis spectrophotometer or ICP-AES. When the catalyst contains only active matrix and active metal components, the sum of the content of active matrix and active metal components is 100%.

[0037] According to some preferred embodiments of the present invention, the active matrix includes zirconium, silicon, aluminum and sulfur, and the content of zirconium oxide, silicon oxide, aluminum oxide and SO3 is 30-90wt% based on the total mass of the active matrix, 1-35wt% based on the total mass of the active matrix, 5-50wt% based on the total mass of the active matrix, 50-80wt% based on the total mass of the active matrix, 5-30wt% based on the total mass of the active matrix, 5-30wt% based on the total mass of the active matrix, 5-30wt% based on the total mass of the active matrix, 2-8wt% based on the total mass of the active matrix. 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 distribution of strong acid centers and accessibility of active centers, and further improves the catalytic activity of the catalyst.

[0038] According to some preferred embodiments of the present invention, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, preferably (0.03-0.08):1.

[0039] According to some preferred embodiments of the present invention, in the active matrix, the mass ratio of the acidic active component calculated as ZrO2 to the mass ratio of the all-silicon molecular sieve calculated as SiO2 is 1:(0.1-1), preferably 1:(0.15-0.5).

[0040] In the present invention, the composition of the active matrix 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.

[0041] 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.

[0042] According to some preferred embodiments of the present invention, the catalyst is prepared by the following method, which comprises:

[0043] (1) mixing an all-silicon molecular sieve having an MFI structure and zirconium hydroxide to obtain a mixture;

[0044] (2) contacting the mixture with a solution containing sulfate;

[0045] (3) mixing the product obtained in step (2), an alumina precursor and an optional peptizing agent, forming and calcining the mixture to obtain an active matrix;

[0046] (4) The active metal component is loaded on the active matrix.

[0047] 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, and the existence of strong acid sites with suitable density and uniform strength has higher normal isomerization activity and selectivity.

[0048] 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.

[0049] 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 in the catalyst, and thus improve the normal isomerization activity.

[0050] According to some preferred embodiments of the present invention, the mass ratio of the zirconium hydroxide calculated by the mass of ZrO2 to the all-silicon molecular sieve calculated by the mass of SiO2 is 1:(0.15-0.5).

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 SO3 content and strong acid center density.

[0056] The present invention has no particular limitation on the amount of the solution containing sulfate, as long as it meets the requirements of the SO3 content range in the catalyst described in the first aspect, and those skilled in the art can select it 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] Preferably, the concentration of the acid in the peptizing agent is 2-10 wt %.

[0063] 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 normal isomerization reaction of light hydrocarbons.

[0064] 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.

[0065] In the present invention, the active metal component can be loaded on the active matrix by any conventional method in the art. Preferably, the method of loading the active metal component on the active matrix comprises: impregnating the active matrix with a solution containing a soluble compound of the active metal, followed by drying and calcining.

[0066] The present invention has a wide selection range for the soluble compound of the active metal, which can be an inorganic salt or an organic salt of the active metal. When the active metal is Pt, the soluble compound of Pt is preferably at least one of chloroplatinic acid, platinum tetrachloride, ammonium chloroplatinate and dinitrosodiamine platinum. When the active metal is Pd, the soluble compound of Pd can be, for example, palladium chloride.

[0067] In the present invention, the solution containing the soluble compound of the active metal is a solution obtained by dissolving the soluble compound of the active metal in a solvent. The present invention has no particular limitation on the type of solvent, as long as it can dissolve the soluble compound of the active metal, for example, it can be water.

[0068] According to some preferred embodiments of the present invention, in order to make the soluble compound containing active metal more evenly loaded on the active matrix and further improve the stability of the catalyst, the solution also contains a competitive adsorbent. The competitive adsorbent is preferably at least one of sulfuric acid, nitric acid and acetic acid, more preferably nitric acid.

[0069] Preferably, the mass ratio of the competitive adsorbent to the soluble compound of the active metal is 1-20: 1, preferably 2-10: 1. The above preferred embodiment is conducive to the uniform dispersion of the soluble compound containing the active metal in the active matrix, while effectively preventing the competitive adsorbent from damaging the structure of the active matrix, further improving the activity stability of the catalyst.

[0070] The present invention has no particular limitation on the amount of the solution containing the soluble compound of the active metal, as long as the amount of the active metal component meets the range described in the first aspect. Preferably, the mass ratio of the amount of the solution containing the soluble compound of the active metal to the active matrix is ​​0.4-1:1, preferably 0.5-0.8:1.

[0071] According to the present invention, the impregnated product is dried and calcined. The present invention has no particular requirements for the specific conditions of the drying, and the drying conditions conventional in the art can be used. Preferably, the drying temperature is 80-140°C, preferably 100-130°C, and the drying time is 5-30h, preferably 8-24h.

[0072] According to the present invention, preferably, the calcination temperature is 450-650° C., preferably 480-600° C., and the calcination time is 1-10 h, preferably 3-5 h.

[0073] According to some preferred embodiments of the present invention, the preparation method further comprises: subjecting the product obtained in step (4) to a reduction treatment in the presence of hydrogen.

[0074] According to some preferred embodiments of the present invention, the reduction treatment conditions include: temperature of 200-300°C, preferably 220-260°C, time of 1-10h, preferably 3-5h; gas volume ratio of 300-1500, preferably 500-1200.

[0075] The isobutane normalization reaction method provided by the present invention can efficiently convert isobutane into normal butane under the reaction conditions of lower temperature, lower hydrogen-to-oil ratio and higher space velocity, and has good reaction stability.

[0076] According to some preferred embodiments of the present invention, the normalization reaction conditions of isobutane include: reaction temperature of 150-250°C, preferably 180-230°C; pressure of 1-4MPa, preferably 1.5-3.5MPa; mass space velocity of isobutane 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 reduce energy consumption and raw material costs, and is conducive to reducing the difficulty of post-processing and separation, and has good reaction economy.

[0077] According to the present invention, there is no particular requirement for the source of the isobutane raw material, and it may include isobutane and optional impurity components. Preferably, the content of isobutane in the isobutane raw material is not less than 80wt%, preferably not less than 90wt%, and more preferably 95-100wt%. In the case of the above preferred isobutane content, it is beneficial to improve the yield of normal butane.

[0078] Preferably, the impurity component is selected from at least one of C1-C3 alkanes, n-butane, C5+ alkanes, water and sulfur.

[0079] Preferably, the content of C1-C3 alkanes in the isobutane raw material is less than 1 wt%, preferably less than 0.5 wt%.

[0080] Preferably, the content of C5+ alkanes in the isobutane raw material is less than 1.5 wt%, preferably less than 1 wt%.

[0081] Preferably, the content of n-butane in the isobutane raw material is less than 2wt%, preferably less than 1wt%. In the present invention, the content of hydrocarbons in the isobutane raw material is obtained by gas chromatography test and then normalized to obtain the content of each component.

[0082] Preferably, the water content in the isobutane feedstock is less than 5 ppmw, preferably less than 3 ppmw.

[0083] Preferably, the sulfur content in the isobutane raw material is less than 10 ppmw, preferably less than 5 ppmw.

[0084] According to the present invention, preferably, the method further comprises: preheating the isobutane raw material and hydrogen to the isobutane normalization reaction temperature, and then contacting with the catalyst. In the present invention, the isobutane raw material and hydrogen can be preheated separately, or the isobutane raw material and hydrogen can be mixed and then preheated together. From the perspective of economy, it is preferred to mix the isobutane raw material and hydrogen and then preheat them together.

[0085] Preferably, the preheating includes primary preheating and secondary preheating, and the primary preheating includes: exchanging heat between the product of the normalization reaction of isobutane and the isobutane raw material 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. The secondary preheating can be performed using a gas heating furnace, an electric heater or a medium-pressure steam heater. Those skilled in the art can select the temperature of the secondary preheating according to the actual operating conditions, as long as the raw material after the primary preheating can be heated to the reaction temperature.

[0086] It is understandable that, when the reaction is initially started, the raw material can be directly heated to the isobutane normalization reaction temperature by secondary preheating. When the reaction is continuously running, the isobutane raw material and / or hydrogen are heat exchanged with the product of the isobutane normalization reaction by primary preheating, and then further heated to the isobutane normalization reaction temperature by secondary preheating. The above preferred embodiment is conducive to further reducing the reaction energy consumption and improving the economy of the isobutane normalization process.

[0087] According to the present invention, preferably, the method further comprises: separating and purifying the contacted product. The separation and purification can be carried out in any manner known in the art, as long as n-butane can be separated from the product. Preferably, the separation and purification comprises: separating the contacted product by distillation to obtain a light component and a heavy component, wherein the light component comprises C1-C3 hydrocarbons and H2, and the heavy component comprises C4 + hydrocarbons; and then separating isobutane from the heavy components through a deisobutanizer, and the separated isobutane can be reused as an isobutane raw material. The above preferred embodiment is conducive to further improving the yield of normal butane.

[0088] According to the present invention, the method for preparing normal butane from isobutane is carried out in a normalization reaction system, such as Figure 3 As shown, the normalization reaction system includes: a feed unit, a preheating device, a reactor 4, a light component separation device 5 and a deisobutanizer 6;

[0089] The feed unit is connected to the feed port of the preheating device to feed the isobutane raw material and hydrogen into the preheating device for preheating;

[0090] 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; the catalyst includes an acidic active component SO4 2- / ZrO2, all-silicon molecular sieve with MFI structure and alumina; the density of the strong acid center in the catalyst is 0.1-2 μmol / m 2 ;

[0091] 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 H2, and the heavy components include C4 + hydrocarbon;

[0092] The deisobutanizer 6 is used to separate isobutane and normal butane products, and the separated isobutane is returned to the feed unit.

[0093] According to some preferred embodiments of the present invention, the feeding unit includes an isobutane raw material supply device and a hydrogen supply device.

[0094] Preferably, the isobutane raw material supply device comprises a feed pump 1, and the isobutane raw material is transported to the preheating device through the feed pump 1 for preheating.

[0095] Preferably, the preheating device comprises a heat exchanger 2 and a heater 3.

[0096] The heat exchanger 2 is used to exchange heat between the reaction product from the reactor 4 and the isobutane 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 isobutane raw material and hydrogen are sent to the heater 3;

[0097] The heater 3 is used to heat the isobutane raw material and hydrogen from the heat exchanger 2 to the isobutane normalization reaction temperature, and then send them into the reactor 4.

[0098] The present invention will be described in detail below through examples.

[0099] The bulk structure of the catalysts in the following examples was analyzed and detected using a Rigaku D / MAX-3A diffractometer (XRD) of Japan. The analysis conditions were: radiation source CuKα target, Ni filter, scanning range 5°-70°, step width 0.02°.

[0100] The Pt content of the catalyst was determined using a Lambda 35 UV-Vis spectrophotometer. The sample was first dissolved in hydrochloric acid and then complexed with stannous chloride. The Pt content was determined by colorimetry.

[0101] ICP-AES was used to determine the Pd content of the catalyst. The sample was first nitrolyzed with aqua regia, then diluted and fixed to volume, and determined by atomic absorption spectrometry and compared with the standard curve to determine the Pd content.

[0102] The composition of the active matrix was characterized and analyzed using an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer. Based on the intensity of the elements present in the scanned samples and the sensitivity of the instrument to the pure substances of these elements, the content of each element in the sample was obtained through theoretical calculation and mathematical correction.

[0103] The zirconium hydroxide powder used was purchased from Changling Catalyst Company, and the zirconium oxide content was 78.5% by weight.

[0104] 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.

[0105] Pseudo-boehmite powder was purchased from Sasol, Germany, with an alumina content of 75% by mass.

[0106] The following preparation examples are used to illustrate the preparation of the catalysts of the present invention.

[0107] Preparation Example 1

[0108] (1) Take 38.2g of zirconium hydroxide powder and 4.4g of all-silicon MFI molecular sieve Si-1 and mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, immerse at 40°C for 4h, and dry the impregnated solid at 60°C for 12h and 120°C for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 10.6g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution for peptization, the ratio of the total mass of nitric acid aqueous solution to the fine powder and alumina precursor is 0.6:1, mix evenly and extrude into strips, dry the wet strips at 120°C for 10h, and calcine at 680°C for 4h to obtain the active matrix SSiZA-1. The XRD characterization results of the active matrix SSiZA-1 are shown in Figure 2 ,Depend on Figure 2 The characteristic peaks of all-silicon MFI molecular sieve can be seen in the figure, and the composition is shown in Table 1.

[0109] (2) 10.0 g of active matrix SSiZA-1 was added to 5.0 g of aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, and impregnated at 25°C for 3 h. The impregnated solid was dried at 120°C for 10 h and calcined at 550°C for 4 h to obtain catalyst CAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0110] Preparation Example 2

[0111] (1) Take 38.2g of zirconium hydroxide powder and 7.8g of all-silicon MFI molecular sieve, mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, soak at 40°C for 4h, and dry the impregnated solid at 60°C for 12h and 120°C for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 10.6g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution for peptization, the ratio of the total mass of nitric acid aqueous solution to the fine powder and alumina precursor is 0.5:1, knead evenly and extrude into strips, dry the wet strips at 120°C for 10h, and calcine at 680°C for 4h to obtain the active matrix SSiZA-2. The XRD characterization results of the active matrix SSiZA-2 are shown in Figure 2 , the composition is shown in Table 1.

[0112] (2) 10.0 g of the active matrix SSiZA-2 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, and the mixture was immersed at 25° C. for 3 h. The immersed solid was dried at 120° C. for 10 h and calcined at 550° C. for 4 h to obtain catalyst CAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0113] Preparation Example 3

[0114] (1) Take 38.2g of zirconium hydroxide powder and 14.3g of all-silicon MFI molecular sieve Si-1 and mix them evenly, add 48.0g of 5% by mass sulfuric acid aqueous solution, immerse at 40°C for 4h, and dry the impregnated solid at 60°C for 12h and 120°C for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 3.4g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution for peptization, the ratio of the total mass of nitric acid aqueous solution to the fine powder and alumina precursor is 0.7:1, mix evenly and extrude into strips, dry the wet strips at 120°C for 10h, and calcine at 680°C for 4h to obtain the active matrix SSiZA-3. The XRD characterization results of the active matrix SSiZA-3 are shown in Figure 2 ,Depend on Figure 2 The characteristic peaks of all-silicon MFI molecular sieve can be seen in the figure, and the composition is shown in Table 1.

[0115] (2) 10.0 g of active matrix SSiZA-1 was added to 5.0 g of aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, and impregnated at 25°C for 3 h. The impregnated solid was dried at 120°C for 10 h and calcined at 550°C for 4 h to obtain catalyst CAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0116] Preparation Example 4

[0117] The method of Preparation Example 1 was followed, except that 10 g of the active matrix SSiZA-1 was added to 5.0 g of an aqueous solution containing 0.0416 g of palladium chloride and 0.1 g of nitric acid, and the mixture was immersed at 25°C for 3 h. The immersed solid was dried at 120°C for 10 h and calcined at 550°C for 4 h to obtain catalyst CAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0118] Preparation Example 5

[0119] (1) 38.2 g of zirconium hydroxide powder was added with 48.0 g of a 5% by mass sulfuric acid aqueous solution, and the mixture was immersed at 40° C. for 4 h. The immersed solid was dried at 60° C. for 12 h and at 120° C. for 12 h.

[0120] The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, 4.4 g of all-silicon MFI molecular sieve and 10.6 g of pseudo-boehmite powder were added thereto, mixed evenly, and a 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, the MFI molecular sieve and the alumina precursor was 0.6:1, and after kneading evenly, the mixture was extruded into strips, and the wet strips were dried at 120°C for 10 h and calcined at 680°C for 4 h to obtain the active matrix SSiZA-4, the composition of which is shown in Table 1.

[0121] (2) 10.0 g of active matrix SSiZA-4 was added to 5.0 g of aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, and impregnated at 25°C for 3 h. The impregnated solid was dried at 120°C for 10 h and calcined at 550°C for 4 h to obtain catalyst CAT-5. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0122] Preparation Example 6

[0123] The method of Preparation Example 2 is followed, except that the amount of chloroplatinic acid used in step (2) is 0.0106 g.

[0124] Catalyst CAT-6 was obtained. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0125] Preparation Example 7

[0126] The method of Preparation Example 2 is followed, except that nitric acid is not introduced into the impregnation solution in step (2) as a competitive adsorbent.

[0127] Catalyst CAT-7 was obtained. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0128] Comparative Preparation Example 1

[0129] (1) Take 38.2g of zirconium hydroxide powder, add 48.0g of 5% by mass sulfuric acid aqueous solution, immerse at 40°C for 4h, and dry the impregnated solid at 60°C for 12h and 120°C for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, mix evenly with 16.6g of pseudo-boehmite powder, add 5.0% by mass nitric acid aqueous solution for peptization, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the alumina precursor being 0.6:1, knead evenly and extrude into strips, dry the wet strips at 120°C for 10h, and calcine at 680°C for 4h to obtain the active matrix DSSiZA-1. The XRD characterization results of the active matrix DSSiZA-1 are shown in Figure 2 It can be seen that the catalyst DA1 does not contain the characteristic peak of all-silicon MFI molecular sieve Si-1. The composition is shown in Table 1.

[0130] (2) 10.0 g of the above-mentioned active matrix DSSiZA-1 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, and the mixture was immersed at 25° C. for 3 h. The immersed solid was dried at 120° C. for 10 h and calcined at 550° C. for 4 h to obtain the catalyst DCAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0131] Comparative Preparation Example 2

[0132] (1) Take 38.2g zirconium hydroxide powder and 10.2g all-silicon MFI molecular sieve, mix them evenly, add 48.0g sulfuric acid aqueous solution with a concentration of 5% by mass, and soak at 40°C for 4h. Dry the soaked solid at 60°C for 12h and 120°C for 12h. Grind the dried solid into fine powder, pass through a 100-300 mesh sieve, add nitric acid aqueous solution with a concentration of 5.0% by mass to peptize, the total mass ratio of nitric acid aqueous solution to the fine powder is 0.6:1, mix and knead evenly, extrude into strips, dry the wet strips at 120°C for 10h, and calcine at 680°C for 4h to obtain the active matrix DSSiZA-2. The composition of the active matrix DSSiZA-2 is shown in Table 1.

[0133] (2) 10.0 g of the active matrix DSSiZA-2 was added to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, and the mixture was immersed at 25° C. for 3 h. The immersed solid was dried at 120° C. for 10 h and calcined at 550° C. for 4 h to obtain the catalyst DCAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0134] Comparative Preparation Example 3

[0135] 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.

[0136] The obtained active matrix is ​​recorded as DSSiZA-3. The composition of the active matrix DSSiZA-3 is shown in Table 1.

[0137] The active metal components were loaded according to the method of Preparation Example 1 to prepare catalyst DCAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0138] Comparative Preparation Example 4

[0139] The method of Preparation Example 2 was followed, except that an equal mass of MCM-41 molecular sieve (denoted as Si-3, produced by Changling Catalyst Company, with a silicon oxide content of 99.7% by mass, XRD characterization see Figure 1 ) replaced the all-silicon MFI molecular sieve. The active matrix DSSiZA-4 was prepared. The composition of the active matrix DSSiZA-4 is shown in Table 1. From the results in Table 1, it can be seen that due to the poor thermal stability of MCM-41, the structure collapsed during high-temperature calcination, resulting in the loss of SO3 in the catalyst.

[0140] The obtained active matrix is ​​recorded as DSSiZA-4. The composition of the active matrix DSSiZA-4 is shown in Table 1.

[0141] Active metal components were loaded according to the method of Preparation Example 1 to prepare catalyst DCAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0142] Table 1

[0143]

[0144]

[0145] Table 2

[0146]

[0147] The following examples are used to illustrate the isobutane normalization method provided by the present invention.

[0148] The isobutane raw material used in the following examples includes: 0.04 mass % propane, 98.74 mass % isobutane, 0.76 mass % n-butane, and 0.46 mass % pentane. The water content in the isobutane raw material is 0.5 ppmw.

[0149] The following examples adopt Figure 3 The isobutane normalization reaction system shown in FIG. 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 an isobutane raw material supply device and a hydrogen supply device, the isobutane 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 3 and 4.

[0150] First, hydrogen was introduced to reduce the catalyst loaded in the reactor 4. The reduction conditions were: 260° C., gauge pressure 0.1 MPa, gas-to-agent volume ratio 800, and reduction for 3 h.

[0151] Then the isobutane raw material is introduced into the feed pipeline through the feed pump 1, mixed with hydrogen, and 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 isobutane normalization 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 components are separated from the top of the tower, which are C1-C3 hydrocarbons and a small amount of H2; the C4 separated from the bottom of the tower + The hydrocarbons are sent to the deisobutanizer 6 for separation. Isobutane is separated from the top of the tower and recycled back to the feed unit to mix with the isobutane raw material. A small amount of C5 + The heavy components are side-drawn with n-butane product.

[0152] 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 reactor outlet product, and the analysis results are listed in Tables 3 and 4.

[0153] Wherein, isobutane conversion rate (%) = ((mass of isobutane in the feedstock - mass of isobutane in the product) / mass of isobutane in the feedstock) × 100%;

[0154] Normal butane selectivity (%) = ((mass of normal butane in the product - mass of normal butane in the feed) / (mass of isobutane in the feed - mass of isobutane in the product)) × 100%.

[0155] Yield of normal butane (%) = ((mass of normal butane in the product - mass of normal butane in the raw material) / mass of isobutane in the raw material) × 100%.

[0156] Table 3

[0157]

[0158] Table 4

[0159]

[0160]

[0161]

[0162] It can be seen from the results in Tables 3 and 4 that the method for preparing normal butane from isobutane provided by the present invention has both high isobutane conversion rate and normal butane selectivity, and high normal butane yield; and, it can be seen from the product analysis results of the reaction for 10 hours and 100 hours that the method provided by the present invention has good reaction stability and is conducive to industrialization.

[0163] 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 preparing normal butane from isobutane, characterized in that: The method comprises: contacting an isobutane raw material with a catalyst under hydrogenation conditions and normalization reaction conditions; Wherein, the catalyst comprises an active matrix and an active metal component supported on the active matrix; Wherein, the active matrix includes the acidic active component SO4 2- / ZrO2, an all-silicon molecular sieve having an MFI structure, and alumina; the active metal component is selected from at least one of the noble metal elements; Wherein, in the catalyst, the density of the strong acid center is 0.1-1 μmol / m 2 .

2. The method according to claim 1, wherein: Based on the total mass of the catalyst, the content of the active matrix is ​​99-99.95wt%, preferably 99.5-99.9wt%; based on the element, the content of the active metal component is 0.05-1wt%, preferably 0.1-0.5wt%.

3. The method according to claim 1 or 2, wherein: The active metal component is selected from Pt and / or Pd.

4. The method according to any one of claims 1 to 3, wherein: In the catalyst, the density of the strong acid center is 0.2-0.7 μmol / m 2 ; Preferably, in the catalyst, the molar ratio of the strong acid to the weak acid is 4-8:

1.

5. The method according to any one of claims 1 to 4, wherein: The active matrix includes zirconium, silicon, aluminum and sulfur, respectively calculated as zirconium oxide, silicon oxide, aluminum oxide and SO3, based on the total mass of the active matrix, the content of zirconium oxide is 30-90wt%, the content of silicon oxide is 1-35wt%, the content of aluminum oxide is 5-50wt%, and the content of SO3 is 1-10wt%; Preferably, based on the total mass of the active matrix, 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%; Preferably, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, preferably (0.03-0.08):

1.

6. The method according to any one of claims 1 to 5, wherein: In the active matrix, the mass ratio of the acidic active component calculated as ZrO2 to the mass ratio of the all-silicon molecular sieve calculated as SiO2 is 1:(0.1-1), preferably 1:(0.15-0.5).

7. The method according to any one of claims 1 to 6, wherein: The isobutane normalization reaction conditions include: reaction temperature of 150-250°C, preferably 180-230°C; pressure of 1-4MPa, preferably 1.5-3.5MPa; mass space velocity of isobutane 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.

8. The method according to any one of claims 1 to 7, wherein: The isobutane raw material includes isobutane and optional impurity components; Preferably, the isobutane content in the isobutane 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, n-butane, C5+ alkanes, water and sulfur; Preferably, the content of C1-C3 alkanes in the isobutane raw material is less than 1wt%, preferably less than 0.5wt%; Preferably, the content of n-butane in the isobutane raw material is less than 2 wt%, preferably less than 1 wt%; Preferably, the content of C5+ alkanes in the isobutane raw material is less than 1.5wt%, preferably less than 1wt%; Preferably, the water content in the isobutane feedstock is less than 5 ppmw, preferably less than 3 ppmw; Preferably, the sulfur content in the isobutane 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 isobutane raw material and hydrogen to the isobutane normalization 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 normalization reaction of isobutane and the isobutane 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 isobutane to provide at least part of the isobutane raw material.

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