Process for the preparation of n-butane from isobutane

Abstract

The present application relates to the preparation of n-butane technical field, disclose a kind of from isobutane preparation n-butane method, the method comprises: under hydrogen condition, under normalizing reaction condition, isobutane raw material is contacted with catalyst;Wherein, the catalyst includes active matrix, and active metal component is supported on the active matrix;Wherein, the active matrix includes acidic active component SO4 2‑ / ZrO2, full-silica molecular sieve with MFI structure and alumina;The active metal component is selected from at least one of noble metal elements;Wherein, in the catalyst, the density of strong acid center is 0.1-1 μmol / m 2 The method is mild, environmentally friendly, and has high isobutane conversion rate and n-butane selectivity, which can increase the yield of n-butane from isobutane, provide high-quality raw materials for ethylene cracking device and butane oxidation method for preparing maleic anhydride, and realize the value-added utilization of butane resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of n-butane preparation, and particularly relates to a method for preparing n-butane from isobutane. BACKGROUND

[0002] N-butane is a high-quality ethylene cracking raw material and a raw material for preparing maleic anhydride by an oxidation method, and increasing n-butane production becomes an important option for making up for the shortage of ethylene cracking raw materials. In addition, since biodegradable plastics mainly use maleic anhydride as a raw material, the demand for maleic anhydride and its upstream n-butane has increased sharply. In China, n-butane mainly exists in mixed butane produced in the petroleum refining process such as catalytic cracking and hydrocracking, for example, the n-butane content in the butane produced by catalytic cracking is usually 40%, and the rest is isobutane. For chemical-type refineries without alkylation devices, isobutane is usually treated as a low-value-added product. Therefore, developing isobutane normalization technology to increase the production of market-needed n-butane has important significance for improving the economic benefits of refineries and helping oil refining enterprises to transform into chemical industry.

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

[0004] It can be seen that in the prior art, when the isobutane normalization catalyst takes chloride as the acid center, the normalizing reaction temperature is high, the dehydrogenation side reaction is difficult to avoid, and the reaction product contains more olefins, which need to be hydrogenated and saturated in a hydrogenation saturation unit, the process flow is complex, and the energy consumption is high. When the catalyst takes SO4 2- / ZrO2 as the acid center, although the normalizing reaction temperature is reduced, the single-pass conversion rate is low, the n-butane yield is low, a large amount of unconverted isobutane needs to be separated from the product, the separation energy consumption is high, and the hydrogen / hydrocarbon ratio is high. In the actual application process, hydrogen needs to be separated from the reaction product and recycled by a circulating hydrogen compressor, which further increases the energy consumption and operating cost. SUMMARY

[0005] The purpose of the present application 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, which has a high isobutane single-pass conversion rate and n-butane selectivity, a high n-butane yield and good stability.

[0006] In order to achieve the above-mentioned purpose, one aspect of the present application provides a method for preparing n-butane from isobutane, which comprises: contacting isobutane raw material with a catalyst under hydrogenation conditions and under normalizing reaction conditions;

[0007] The catalyst comprises an active substrate and an active metal component supported on the active substrate.

[0008] The active substrate comprises an acidic active component SO4 2- / ZrO2, a full-silica molecular sieve with MFI structure and alumina, and the active metal component is selected from at least one of noble metal elements.

[0009] The density of strong acid centers in the catalyst is 0.1-1 μmol / m 2 .

[0010] Preferably, the isobutane normalizing reaction conditions comprise: the reaction temperature is 150-250°C, preferably 180-230°C; the pressure is 1-4 MPa, preferably 1.5-3.5 MPa; the mass space velocity of isobutane raw material is 0.5-10 h -1 , preferably 1-5 h -1 , more preferably 1.2-4 h -1 ; the hydrogen / hydrocarbon molar ratio is 0.02-0.3, preferably 0.03-0.2.

[0011] The method for preparing normal butane from isobutane provided by the application uses sulfuric zirconia modified by a full-silicon MFI structure molecular sieve as an active matrix, so that the catalyst has a suitable density of strong acid centers, further cooperates with noble metals to provide strong acid centers and weak acid centers respectively, and the catalyst is used in isobutane normalization reaction, can efficiently convert isobutane into normal butane under reaction conditions of lower temperature, lower hydrogen to oil ratio and higher space velocity. The method has mild conditions, is environment-friendly, has higher isobutane single-pass conversion rate and normal butane selectivity, can use isobutane to increase the yield of normal butane, provides high-quality raw materials for ethylene cracking devices and butane oxidation method for preparing maleic anhydride devices, and realizes the value-added utilization of butane resources. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is the XRD spectrum of the full-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 application;

[0013] Figure 2 is the XRD spectrum of the active matrix prepared in preparation examples 1-3 and comparative preparation example 1 of the application;

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

[0015] BRIEF DESCRIPTION OF DRAWINGS

[0016] DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. Ranges include endpoints between the respective range endpoints, between the respective range endpoints and single values within ranges, and between single values. These ranges are to be understood to be inclusive.

[0018] The application provides a method for preparing normal butane from isobutane, the method comprising: under hydrogenation conditions, under normal butane reaction conditions, contacting isobutane raw material with a catalyst;

[0019] The catalyst comprises an active matrix and an active metal component supported on the active matrix.

[0020] The active matrix comprises an acidic active component SO4 2- / ZrO2, a full-silicon molecular sieve with an MFI structure and alumina; the active metal component is selected from at least one of noble metal elements.

[0021] wherein the density of strong acid sites in the catalyst is 0.1-1 μmol / m 2 .

[0022] In the present application, the phase analysis of the catalyst sample is performed by using a Japan Rigaku D / MAX-3A type diffractometer (XRD), and the analysis conditions are as follows: ray source Cu Kα target, Ni filter, scanning range 5°-70°, step width 0.02°.

[0023] In the solid acid catalyst system in the prior art, the molecular sieve is usually used as a carrier, and the molecular sieve used as a carrier occupies a high content in the catalyst; and the silicon-aluminum molecular sieve introduced into the catalyst is also usually used to provide additional acid active sites.

[0024] The catalyst used in the method for preparing n-butane from isobutane provided by the present application has a suitable density of strong acid sites, while the density of strong acid sites in the super strong solid acid zirconium sulfate in the prior art is relatively high, generally higher than 2 μmol / m 2 . The inventors of the present application found in the research that the density of strong acid sites that is too high is not conducive to the normal-isomerization selectivity of the catalyst.

[0025] According to the present application, a small amount of full-silica molecular sieve with MFI structure and alumina can play a role in adjusting the distribution of strong acid sites of the solid acid catalyst, so that the catalyst has high normal-isomerization activity and selectivity. Further, the synergistic effect of the noble metal component and the zirconium sulfate in the active matrix can improve the stability of the catalyst through the joint action of strong acid sites and weak acid sites. The reason is that the full-silica molecular sieve with MFI structure has a special pore structure, basically no acidity, and excellent thermal stability, which helps to optimize the distribution of strong acid sites in the zirconium sulfate, is conducive to the efficient activation and conversion of light hydrocarbon molecules through a single molecular path, and is conducive to the diffusion of reactants and products, thereby effectively avoiding the occurrence of secondary reactions.

[0026] According to some preferred embodiments of the present application, the density of strong acid sites 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 , and the like, typical but not limited values or ranges between them. In the above preferred cases, it is beneficial to further improve the activity and selectivity of the catalyst in the light hydrocarbon normal-isomerization reaction.

[0027] In the present application, the density of the strong acid center is the ratio of the amount of strong acid in the catalyst to the specific surface area. The testing method of the amount of acid in the catalyst comprises: using a Nicolet 6700 Fourier transform infrared spectrometer produced by the American Thermo Fisher Company, with a resolution of 4 cm -1 , and scanning 64 times. The sample is pressed into a self-supporting sheet with a diameter of 13 mm, then placed in a muffle furnace for high-temperature calcination, and after completion, directly cooled in a desiccator at high temperature, and after cooling to room temperature, placed in a self-made quartz infrared sample cell, first treated at 400℃ for 2h under normal pressure flowing air, then cooled to 200℃, vacuum purified for 4h, then cooled to -190℃ with liquid nitrogen, saturated adsorption of the purified CO probe molecule for 0.5h, and then desorption. The spectra before and after adsorption are subtracted to obtain the infrared spectrum of the sample adsorbed CO. The spectrum at a wave number of 2050-2250 cm -1 is peak-processed, and the spectrum can be divided into four absorption peaks with wave numbers of 2186 cm -1 , 2167 cm -1 , 2150 cm -1 and 2125 cm -1 , wherein the absorption peak at a wave number of 2167 cm -1 is a strong acid center directly related to the performance of the catalyst, and the absorption peak at a wave number of 2150 cm -1 is a weak acid center of the catalyst. The acid amount is calculated according to formula (1) N (unit: μmol / g)

[0028] N = A / ( pA 0), formula (1),

[0029] wherein A is the integral area of the absorption peak (unit: cm -1 ), p is the mass of the catalyst support sheet per square centimeter (unit: g / cm 2 ), A 0 is the molar extinction coefficient, and for the spectrum peaks at wave numbers of 2167 cm -1 and 2150 cm -1 , A 0=2.6 cm / μmol.

[0030] In the present application, the specific surface area of the catalyst is characterized by low-temperature nitrogen static volume adsorption method (BET method), and the instrument used is an ASAP2400 specific surface area tester produced by the Micromeritics instrument company, with pretreatment conditions of 250℃, 1.3Pa, and treatment for 4h, and the specific surface area (m 2 / g) is calculated by using the BET formula.

[0031] According to some preferred embodiments of the present application, the molar ratio of the amount of strong acid to the amount of weak acid in the catalyst is 4-8:1, such as 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, and the like, which are exemplary but not limiting molar ratios. Preferably, the molar ratio is 4.5-6.8:1. In the above preferred cases, the stability of the catalyst is further improved.

[0032] According to some preferred embodiments of the present application, the active metal component is selected from at least one of Pt, Pd, Ru and Rh, preferably Pt and / or Pd.

[0033] In the present application, the active metal component is present in the form of an oxide and / or in the metallic state, preferably at least part of the active metal component is present in the metallic state.

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

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

[0036] According to some preferred embodiments of the present application, the active matrix comprises zirconium element, silicon element, aluminum element and sulfur element, which are respectively in the form of zirconia, silica, alumina and SO3. The content of zirconia is 30-90wt%, the content of silica is 1-35wt%, the content of alumina is 5-50wt%, and the content of SO3 is 1-10wt%, based on the total mass of the active matrix. Preferably, the content of zirconia is 50-80wt%, the content of silica is 5-30wt%, the content of alumina is 5-30wt%, and the content of SO3 is 2-8wt%, based on the total mass of the active matrix. In the above preferred composition, the thermal stability of tetragonal zirconia and the specific surface area of the catalyst are improved, so that the catalyst has a suitable distribution of strong acid centers and accessibility of active centers, and the catalytic activity of the catalyst is further improved.

[0037] According to some preferred embodiments of the present application, the mass ratio of SO3 to ZrO2 is (0.02-0.12):1, preferably (0.03-0.08):1.

[0038] According to some preferred embodiments of the present application, the mass ratio of the acidic active component to the total siliceous molecular sieve in the active matrix, calculated as ZrO2 to SiO2, is 1:(0.1-1), preferably 1:(0.15-0.5).

[0039] In the present application, the composition of the active matrix is characterized by using a wavelength dispersive X-ray fluorescence spectrometer (XRF-1800). According to the intensity of the elements in the sample obtained by scanning and the sensitivity of the pure substances of these elements in the instrument, the content of each element in the sample is obtained by theoretical calculation and mathematical correction.

[0040] In the present application, the shape of the catalyst is not particularly limited and can be selected by those skilled in the art according to actual needs. For example, it can be in the form of a strip, a small ball, a sheet, a particle or a microsphere, so as to be suitable for a fixed bed, a moving bed or a fluidized bed reaction.

[0041] According to some preferred embodiments of the present application, the catalyst is prepared by a method comprising:

[0042] (1) mixing a total siliceous molecular sieve with MFI structure and zirconium hydroxide to obtain a mixture;

[0043] (2) contacting the mixture with a solution containing sulfate;

[0044] (3) mixing the product obtained in step (2), an alumina precursor and an optional peptizing agent, shaping, and calcining to obtain an active matrix;

[0045] (4) loading an active metal component on the active matrix.

[0046] According to the present application, the above preparation method can make the total siliceous molecular sieve with MFI structure uniformly distributed in the catalyst without blocking the pores of the catalyst, reduce the density of strong acid sites in zirconium sulfate oxide under the premise of not introducing new acid sites, and the existence of strong acid sites with appropriate density and uniform strength, thereby having high normal isomerization activity and selectivity.

[0047] The present application has a wide range of selection for the number and structure of the pores of the total siliceous molecular sieve, and the total siliceous molecular sieve with MFI structure can be applied to the present application.

[0048] In some preferred embodiments, the specific surface area of the total siliceous molecular sieve is 400-500 m 2 / g, preferably 420-460 m 2 / g. In the above preferred case, it is advantageous to further optimize the density of strong acid centers in zirconium sulfate oxide, to improve the uniformity of strong acid sites in the catalyst, thereby improving the normal-isomerization activity.

[0049] According to some preferred embodiments of the present application, the mass ratio of the zirconium hydroxide to the total silicon molecular sieve, in terms of the mass of ZrO2, is 1: (0.15-0.5).

[0050] In the present application, the contacting of the mixture with the solution containing sulfate in step (2) forms the acidic active component. The contacting can be performed in a manner conventional in the art, for example, the mixture can be impregnated with the solution containing sulfate.

[0051] The present application does not have particular limitations on the specific operating conditions of the contacting, as long as the catalyst composition range described above can be met, and the person skilled in the art can select according to actual needs.

[0052] According to some preferred embodiments of the present application, the temperature of the contacting is 20-80°C, preferably 25-60°C; the time is 1-10h, preferably 2-5h.

[0053] The present application has a wide range of selection for the specific type of the solution containing sulfate. Preferably, the solution containing sulfate is selected from the aqueous solution of at least one of sulfuric acid, ammonium sulfate and ammonium bisulfate.

[0054] Preferably, the concentration of sulfate in the solution containing sulfate is 1-10wt%, preferably 2-8wt%. The above preferred embodiments are advantageous for obtaining a suitable SO3 content and strong acid center density.

[0055] The present application does not have particular limitations on the amount of the solution containing sulfate, as long as the SO3 content range requirement in the catalyst of the first aspect can be met, and the person 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.

[0056] In the present application, the contacting in step (2) is followed by optional drying and grinding steps. The temperature of the drying can be 50-150°C, and the time of the drying can be 3-100h. The grinding is used to grind the dried solid into a powder of 100-300 mesh, which is advantageous for improving the crushing strength of the catalyst in the above preferred case.

[0057] In the present application, the alumina precursor refers to a substance which can be calcined to obtain alumina, and is well known to those skilled in the art. Preferably, the alumina precursor is pseudoboehmite and / or gibbsite, preferably pseudoboehmite. In the above preferred case, the thermal stability and crushing strength of the catalyst are improved.

[0058] In the present application, the shaping in step (3) can be performed by using any conventional method and condition, and the present application is not particularly limited thereto. The shaping method can be selected according to the actual application needs, for example, can be selected from any one of extrusion, granulation, rolling and spray drying, preferably extrusion. In the above preferred case, it is more suitable for a fixed bed reactor.

[0059] According to some preferred embodiments of the present application, the ratio of the peptizing agent to the total mass of the product obtained in step (2) and the alumina precursor is 0.3-1:1, preferably 0.4-0.8:1.

[0060] According to some preferred embodiments of the present application, the peptizing agent is an aqueous acid solution, preferably an aqueous solution of at least one acid selected from nitric acid, acetic acid, citric acid, oxalic acid and formic acid.

[0061] Preferably, the concentration of the acid in the peptizing agent is 2-10 wt%.

[0062] According to some preferred embodiments of the present application, in step (3), the calcination temperature is 600-850°C, preferably 650-850°C, and the calcination time is 1-20h, preferably 3-12h. In the above preferred calcination temperature conditions, it is beneficial to form strong acid centers with appropriate density, and thus beneficial to improve the activity and selectivity of the catalyst in the light hydrocarbon normal isomerization reaction.

[0063] In the present application, the calcination in step (3) can further include a drying process. Preferably, the drying temperature is 80-140°C, preferably 100-130°C, and the drying time is 5-30h, preferably 8-24h.

[0064] In the present application, the active metal component can be loaded on the active matrix by using any conventional method in the art. Preferably, the method for loading the active metal component on the active matrix includes: impregnating the active matrix with a solution containing a soluble compound of the active metal, and then drying and calcining.

[0065] The active metal-containing soluble compound 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 platinum bisnitrilo diaminate. When the active metal is Pd, the soluble compound of Pd can be, for example, palladium chloride.

[0066] In the present application, the solution containing the active metal-containing soluble compound is a solution obtained by dissolving the active metal-containing soluble compound in a solvent. The solvent is not particularly limited as long as it can dissolve the active metal-containing soluble compound, and can be, for example, water.

[0067] According to some preferred embodiments of the present application, in order to make the active metal-containing soluble compound more uniformly loaded on the active substrate and further improve the stability of the catalyst, the solution further contains a competitive adsorbent. The competitive adsorbent is preferably at least one of sulfuric acid, nitric acid, and acetic acid, and is more preferably nitric acid.

[0068] Preferably, the mass ratio of the competitive adsorbent to the active metal-containing soluble compound is 1-20:1, and is preferably 2-10:1. By using the above preferred embodiments, the active metal-containing soluble compound is uniformly dispersed in the active substrate, and at the same time, the competitive adsorbent is effectively prevented from damaging the structure of the active substrate, thereby further improving the activity stability of the catalyst.

[0069] The present application does not particularly limit the amount of the solution containing the active metal-containing soluble compound, as long as the amount of the active metal component satisfies the range described in the first aspect. Preferably, the mass ratio of the solution containing the active metal-containing soluble compound to the active substrate is 0.4-1:1, and is preferably 0.5-0.8:1.

[0070] According to the present application, the product after impregnation is dried and calcined. The present application does not particularly require the specific conditions for drying, and the drying can be performed using conventional drying conditions in the art. Preferably, the drying temperature is 80-140°C, and is preferably 100-130°C, and the drying time is 5-30h, and is preferably 8-24h.

[0071] According to the present application, preferably, the calcination temperature is 450-650°C, and is preferably 480-600°C, and the calcination time is 1-10h, and is preferably 3-5h.

[0072] According to some preferred embodiments of the present application, the preparation method further comprises: reducing the product obtained in step (4) in the presence of hydrogen.

[0073] According to some preferred embodiments of the present application, the conditions of the reduction treatment include: temperature of 200-300℃, preferably 220-260℃, time of 1-10h, preferably 3-5h; and volume ratio of gas to agent of 300-1500, preferably 500-1200.

[0074] The isobutane normalization reaction method provided by the present application can efficiently convert isobutane into n-butane under reaction conditions of lower temperature, lower hydrogen / oil ratio and higher space velocity, and has good reaction stability.

[0075] According to some preferred embodiments of the present application, the isobutane normalization reaction conditions include: reaction temperature of 150-250℃, preferably 180-230℃; 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 ; and hydrogen / hydrocarbon molar ratio of 0.02-0.3, preferably 0.03-0.2. The above preferred embodiments are conducive to greatly reducing the amount of hydrogen, which can reduce energy consumption and raw material cost, and is conducive to reducing the difficulty of post-treatment and separation, and has good reaction economy.

[0076] According to the present application, the source of the isobutane raw material is not particularly required, and can 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 above preferred content of isobutane, the yield of n-butane is improved.

[0077] Preferably, the impurity components are selected from at least one of C1-C3 alkanes, n-butane, C5+ alkanes, water and sulfur elements.

[0078] Preferably, the content of C1-C3 alkanes in the isobutane raw material is less than 1wt%, preferably less than 0.5wt%.

[0079] Preferably, the content of C5+ alkanes in the isobutane raw material is less than 1.5wt%, preferably less than 1wt%.

[0080] Preferably, the content of n-butane in the isobutane raw material is less than 2wt%, preferably less than 1wt%. In the present application, 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.

[0081] Preferably, the content of water in the isobutane raw material is less than 5ppmw, preferably less than 3ppmw.

[0082] Preferably, the sulfur content in the isobutane feedstock is less than 10 ppmw, preferably less than 5 ppmw.

[0083] According to the present application, preferably, the method further comprises: preheating the isobutane feedstock and hydrogen to the isobutane normalization reaction temperature before contacting with the catalyst. In the present application, the isobutane feedstock and hydrogen can be preheated respectively or preheated together after mixing. From the economic point of view, it is preferred that the isobutane feedstock and hydrogen are preheated together after mixing.

[0084] Preferably, the preheating comprises a first-stage preheating and a second-stage preheating, and the first-stage preheating comprises: exchanging heat between the product of the isobutane normalization reaction and the isobutane feedstock and / or hydrogen. The first-stage preheating can be carried out by using a heat exchanger commonly used in the art, for example, a shell-and-tube heat exchanger. The second-stage preheating can be carried out by using a gas-fired heater, an electric heater or a medium-pressure steam heater, and the person skilled in the art can select the temperature of the second-stage preheating according to the actual operation condition, as long as the preheating can heat the feedstock to the reaction temperature.

[0085] It can be understood that, when starting the reaction, the feedstock can be directly heated to the isobutane normalization reaction temperature by the second-stage preheating, and when continuously operating the reaction, the isobutane feedstock and / or hydrogen are exchanged heat with the product of the isobutane normalization reaction by the first-stage preheating, and then further heated to the isobutane normalization reaction temperature by the second-stage preheating. By using the preferred embodiment described above, the energy consumption of the reaction can be further reduced, and the economy of the isobutane normalization process can be improved.

[0086] According to the present application, preferably, the method further comprises: separating and purifying the product of the contacting. The separation and purification can be carried out by using any known method in the art, as long as the n-butane can be separated from the product. Preferably, the separation and purification comprises: separating the product of the contacting by distillation to obtain a light component and a heavy component, the light component comprising C1-C3 hydrocarbons and H2, and the heavy component comprising C4 + hydrocarbons; and separating isobutane from the heavy component by an isobutane removal column, and the separated isobutane can be reused as the isobutane feedstock. By using the preferred embodiment described above, the yield of n-butane can be further improved.

[0087] According to the present application, the method for preparing n-butane from isobutane is carried out in a normalization reaction system, as shown in Figure 3 The normalization reaction system comprises: a feeding unit, a preheating device, a reactor 4, a light component separation device 5 and an isobutane removal column 6.

[0088] The feeding unit is communicated with the feeding port of the preheating device, and the isobutane raw material and hydrogen are sent into the preheating device for preheating.

[0089] The outlet of the preheating device is communicated with the feeding port of the reactor 4, and the preheated raw material is sent into the reactor 4 to contact with the catalyst; the catalyst comprises an acidic active component SO4 2- / ZrO2, a full-silica molecular sieve with MFI structure, and alumina; the density of strong acid centers in the catalyst is 0.1-2 μmol / m 2 ;

[0090] The light component separation device 5 is used for separating the reaction product from the reactor 4, and the obtained light component is recycled, and the obtained heavy component is sent into the isobutane removal column 6; wherein the light component comprises C1-C3 hydrocarbon and H2, and the heavy component comprises C4 + hydrocarbon;

[0091] The isobutane removal column 6 is used for separating isobutane and n-butane products, and the separated isobutane is returned to the feeding unit.

[0092] According to some preferred embodiments of the present application, the feeding unit comprises an isobutane raw material supply device and a hydrogen supply device.

[0093] Preferably, the isobutane raw material supply device comprises a feeding pump 1, and the isobutane raw material is sent into the preheating device for preheating by the feeding pump 1.

[0094] Preferably, the preheating device comprises a heat exchanger 2 and a heater 3,

[0095] The heat exchanger 2 is used for exchanging heat between the reaction product from the reactor 4 and the isobutane raw material and hydrogen from the feeding unit, and the exchanged reaction product is sent into the light component separation device 5, and the isobutane raw material and hydrogen are sent into the heater 3.

[0096] The heater 3 is used for heating the isobutane raw material and hydrogen from the heat exchanger 2 to the isobutane normalization reaction temperature, and then sending them into the reactor 4.

[0097] The present application will be described in detail below through examples.

[0098] In the following examples, the bulk structure of the catalyst is analyzed and detected by using a Japan Rigaku D / MAX-3A diffractometer (XRD) to analyze and detect the phase of the catalyst sample, and the analysis conditions are as follows: the ray source is Cu Kα target, the Ni filter sheet, the scanning range is 5°-70°, and the step width is 0.02°.

[0099] The Pt content of the catalyst was determined by a Lambda 35 UV-Vis spectrophotometer. The sample was dissolved with hydrochloric acid, then complexed with stannous chloride, and the Pt content was determined by colorimetry.

[0100] The Pd content of the catalyst was determined by ICP-AES. The sample was nitrated with aqua regia, then diluted and fixed volume, and the Pd content was determined by atomic absorption spectrometry and compared with the standard curve.

[0101] The composition of the active matrix was characterized and analyzed by an XRF-1800 wavelength dispersive X-ray fluorescence spectrometer. According to 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, the content of each element in the sample was obtained by theoretical calculation and mathematical correction.

[0102] The zirconium hydroxide powder used was purchased from Changling Catalyst Co., Ltd., and the zirconium oxide content was 78.5% by weight.

[0103] The all-silicon MFI molecular sieve Si-1 used was purchased from Changling Catalyst Co., Ltd., and the silicon oxide content was 99.7% by mass, the specific surface area was 444.6 m 2 / g, and the XRD characterization is shown in Figure 1 .

[0104] The pseudo-boehmite powder was purchased from Germany Sasol Company, and the aluminum oxide content was 75% by mass.

[0105] The following preparation examples are used to illustrate the preparation of the catalyst in the present application.

[0106] Preparation Example 1

[0107] (1) 38.2g of zirconium hydroxide powder and 4.4g of all-silicon MFI molecular sieve Si-1 were mixed uniformly, 48.0g of 5% by mass sulfuric acid aqueous solution was added, and impregnated at 40℃ for 4h, and the impregnated solid was dried at 60℃ for 12h and 120℃ for 12h. The dried solid was ground into fine powder, passed through a 100-300 mesh sieve, and mixed uniformly with 10.6g of pseudo-boehmite powder, and gelatinized with 5.0% by mass nitric acid aqueous solution, the ratio of the nitric acid aqueous solution to the total mass of the fine powder and the aluminum oxide precursor was 0.6:1, and after kneading uniformly, it was extruded into strips, the wet strips were dried at 120℃ for 10h and calcined at 680℃ for 4h to obtain the active matrix SSiZA-1. The XRD characterization results of the active matrix SSiZA-1 are shown in Figure 2 , and the characteristic peaks of the all-silicon MFI molecular sieve can be seen in Figure 2 , and the composition is shown in Table 1.

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

[0109] Preparation Example 2

[0110] (1) Take 38.2 g of zirconium hydroxide powder and 7.8 g of a full-silica MFI molecular sieve, mix them uniformly, add 48.0 g of a 5 mass% sulfuric acid aqueous solution, immerse at 40 °C for 4 h, dry the immersed solid at 60 °C for 12 h and at 120 °C for 12 h. Grind the dried solid into fine powder, pass it through a 100-300 mesh sieve, mix it uniformly with 10.6 g of pseudo-boehmite powder, and gelatinize with a 5.0 mass% nitric acid aqueous solution, the ratio of the mass of the nitric acid aqueous solution to the total mass of the fine powder and the aluminum oxide precursor being 0.5:1, uniformly knead and extrude into strips, dry the wet strips at 120 °C for 10 h and calcine at 680 °C for 4 h to prepare the active matrix SSiZA-2. The XRD characterization results of the active matrix SSiZA-2 are shown in Figure 2 , and the composition is shown in Table 1.

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

[0112] Preparation Example 3

[0113] (1) Take 38.2 g of zirconium hydroxide powder and 14.3 g of a full-silica MFI molecular sieve Si-1, mix them uniformly, add 48.0 g of a 5 mass% sulfuric acid aqueous solution, immerse at 40 °C for 4 h, dry the immersed solid at 60 °C for 12 h and at 120 °C for 12 h. Grind the dried solid into fine powder, pass it through a 100-300 mesh sieve, mix it uniformly with 3.4 g of pseudo-boehmite powder, and gelatinize with a 5.0 mass% nitric acid aqueous solution, the ratio of the mass of the nitric acid aqueous solution to the total mass of the fine powder and the aluminum oxide precursor being 0.7:1, uniformly knead and extrude into strips, dry the wet strips at 120 °C for 10 h and calcine at 680 °C for 4 h to prepare the active matrix SSiZA-3. The XRD characterization results of the active matrix SSiZA-3 are shown in Figure 2 , and the composition is shown in Table 1. Figure 2 , and the composition is shown in Table 1.

[0114] (2) Take 10.0 g of the active matrix SSiZA-1 and add it to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, immerse at 25 °C for 3 h, dry the immersed solid at 120 °C for 10 h, and calcine at 550 °C for 4 h to obtain the catalyst CAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0115] Preparation Example 4

[0116] According to the method of Preparation Example 1, except that 10 g of the active matrix SSiZA-1 is added to 5.0 g of an aqueous solution containing 0.0416 g of palladium chloride and 0.1 g of nitric acid, immerse at 25 °C for 3 h, dry the immersed solid at 120 °C for 10 h, and calcine at 550 °C for 4 h to obtain the catalyst CAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0117] Preparation Example 5

[0118] (1) Take 38.2 g of zirconium hydroxide powder and add it to 48.0 g of an aqueous solution of sulfuric acid with a concentration of 5 mass%, immerse at 40 °C for 4 h, dry the immersed solid at 60 °C for 12 h, and at 120 °C for 12 h.

[0119] Grind the dried solid into fine powder, pass it through a 100-300 mesh sieve, add 4.4 g of a full-silica MFI molecular sieve and 10.6 g of a pseudo-boehmite powder to it, mix well, gelatinize with an aqueous solution of nitric acid with a concentration of 5.0 mass%, the ratio of the aqueous solution of nitric acid to the total mass of the fine powder, MFI molecular sieve and alumina precursor being 0.6:1, knead well, extrude into strips, dry the wet strips at 120 °C for 10 h, and calcine at 680 °C for 4 h to obtain the active matrix SSiZA-4. The composition is shown in Table 1.

[0120] (2) Take 10.0 g of the active matrix SSiZA-4 and add it to 5.0 g of an aqueous solution containing 0.0266 g of chloroplatinic acid and 0.1 g of nitric acid, immerse at 25 °C for 3 h, dry the immersed solid at 120 °C for 10 h, and calcine at 550 °C for 4 h to obtain the catalyst CAT-5. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0121] Preparation Example 6

[0122] According to the method of Preparation Example 2, except that the amount of chloroplatinic acid in step (2) is 0.0106 g.

[0123] Obtain the catalyst CAT-6. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0124] Preparation Example 7

[0125] According to the method of Preparation Example 2, except that no nitric acid is introduced as a competitive adsorbent in the immersion solution in step (2).

[0126] Catalyst CAT-7 was prepared. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0127] Comparative Preparation Example 1

[0128] (1) 38.2 g of zirconium hydroxide powder was taken and impregnated with 48.0 g of a 5 mass% sulfuric acid aqueous solution at 40°C for 4 h. The impregnated solid was dried at 60°C for 12 h and at 120°C for 12 h. The dried solid was ground into fine powder, sieved through a 100-300 mesh sieve, and mixed uniformly with 16.6 g of pseudo-boehmite powder. A 5.0 mass% nitric acid aqueous solution was added to the fine powder and alumina precursor, and the mixture was kneaded uniformly. The wet mixture was extruded into a strip, dried at 120°C for 10 h, and calcined at 680°C for 4 h to obtain an active matrix DSSiZA-1. The XRD characterization results of the active matrix DSSiZA-1 are shown in Table 1. Figure 2 As can be seen, the catalyst DA1 does not contain the characteristic peaks of the all-silica MFI molecular sieve Si-1, and the composition is shown in Table 1.

[0129] (2) 10.0 g of the active matrix DSSiZA-1 was taken and added to 5.0 g of an 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 a catalyst DCAT-1. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0130] Comparative Preparation Example 2

[0131] (1) 38.2 g of zirconium hydroxide powder and 10.2 g of an all-silica MFI molecular sieve were taken and mixed uniformly. The mixture was impregnated with 48.0 g of a 5 mass% sulfuric acid aqueous solution at 40°C for 4 h. The impregnated solid was dried at 60°C for 12 h and at 120°C for 12 h. The dried solid was ground into fine powder, sieved through a 100-300 mesh sieve, and mixed uniformly with 16.6 g of pseudo-boehmite powder. A 5.0 mass% nitric acid aqueous solution was added to the fine powder and alumina precursor, and the mixture was kneaded uniformly. The wet mixture was extruded into a strip, dried at 120°C for 10 h, and calcined at 680°C for 4 h to obtain an active matrix DSSiZA-2. The composition of the active matrix DSSiZA-2 is shown in Table 1.

[0132] (2) 10.0 g of the active matrix DSSiZA-2 was taken and added to 5.0 g of an 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 a catalyst DCAT-2. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0133] Comparative Preparation Example 3

[0134] The procedure of Preparation Example 2 was followed except that equal mass of ZSM-5 molecular sieve (denoted as Si-2, produced by Changling Catalyst Co., Ltd., molar ratio of silica to alumina is 65, XRD characterization is shown in Figure 2) was used to replace the all-silica MFI molecular sieve. Figure 1

[0135] The active matrix was denoted as DSSiZA-3. The composition of the active matrix DSSiZA-3 is shown in Table 1.

[0136] The active metal component was loaded according to the procedure of Preparation Example 1 to produce the catalyst DCAT-3. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0137] Comparative Preparation Example 4

[0138] The procedure of Preparation Example 2 was followed except that equal mass of MCM-41 molecular sieve (denoted as Si-3, produced by Changling Catalyst Co., Ltd., silica content is 99.7 mass%, XRD characterization is shown in Figure 3) was used to replace the all-silica MFI molecular sieve. The active matrix DSSiZA-4 was produced. The composition of the active matrix DSSiZA-4 is shown in Table 1. It can be seen from the results in Table 1 that due to the poor thermal stability of MCM-41, the structure collapses during high-temperature calcination, thereby leading to the loss of SO3 in the catalyst. Figure 1 The active matrix was denoted as DSSiZA-4. The composition of the active matrix DSSiZA-4 is shown in Table 1.

[0139] The active metal component was loaded according to the procedure of Preparation Example 1 to produce the catalyst DCAT-4. The composition and physicochemical properties of the catalyst are shown in Table 2.

[0140] Table 1

[0141]

[0142]

[0143] Table 2

[0144]

[0145] The following examples are used to illustrate the method for isobutane normalization provided by the present application

[0146] The isobutane raw material used in the following examples includes: 0.04 mass% of propane, 98.74 mass% of isobutane, 0.76 mass% of n-butane, and 0.46 mass% of pentane. The water content in the isobutane raw material is 0.5 ppmw.

[0147] The following examples were carried out using the isobutane normalization reaction system as shown in Figure 3 Figure 3 ​​​As shown, the reaction system includes: a feed unit, a preheating device, a reactor 4, a light component separation device 5 and a de-isobutane column 6; 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 reactor 4 is filled with a catalyst, and the filling and reaction conditions are shown in Tables 3 and 4.

[0148] First, the catalyst filled in the reactor 4 is reduced by passing hydrogen, and the reduction conditions are: 260°C, 0.1 MPa of gage pressure, and a gas agent volume ratio of 800, for 3h.

[0149] Then, the isobutane raw material is passed into the feed pipeline through the feed pump 1, mixed with hydrogen, heated to the reaction temperature through the heat exchanger 2 and the heater 3 in turn, and then sent into the reactor 4 to contact with the catalyst to perform isobutane normalization reaction. The obtained reaction product is sent into the heat exchanger 2 to exchange heat with the mixed raw material of isobutane and hydrogen, the heat-exchanged reaction product is sent into the light component separation device 5, the light components are separated at the top, which are C1-C3 hydrocarbons and a small amount of H2; the C4 + hydrocarbons separated at the bottom are sent into the de-isobutane column 6 for separation, isobutane is separated at the top and recycled back to the feed unit to be mixed with the isobutane raw material, and a small amount of C5 + heavy components are separated at the bottom and side-drawn as n-butane products.

[0150] Product sampling and analysis method: a bypass is provided on the main pipeline at the outlet of the reactor 4, and a sampling port is provided on the bypass; when sampling, a sampling steel bottle is connected to the sampling port through a quick connector, then the valves at the front and back of the sampling steel bottle are opened, the sampling steel bottle is replaced with the product, after replacement is completed, the outlet valve of the sampling steel bottle is closed, after a certain amount of material to be analyzed is filled, the inlet valve is closed, the quick connector is disconnected, and sampling is completed. The sample is sent to the laboratory for analysis of the product composition at the outlet of the reactor, and the analysis results are shown in Tables 3 and 4.

[0151] Among them, the isobutane conversion rate (%) = ((the mass of isobutane in the raw material-the mass of isobutane in the product) / the mass of isobutane in the raw material) x 100%;

[0152] The n-butane selectivity (%) = ((the mass of n-butane in the product-the mass of n-butane in the raw material) / (the mass of isobutane in the raw material-the mass of isobutane in the product)) x 100%.

[0153] The n-butane yield (%) = ((the mass of n-butane in the product-the mass of n-butane in the raw material) / the mass of isobutane in the raw material) x 100%.

[0154] Table 3

[0155]

[0156] Table 4

[0157]

[0158] It can be seen from the results of Tables 3 and 4 that the method for preparing n-butane from isobutane provided by the present application has high isobutane conversion rate and n-butane selectivity, and high n-butane yield; and it can be seen from the product analysis results of the reaction for 10 h and the reaction for 100 h that the method provided by the present application has good reaction stability, and is conducive to industrialization.

[0159] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A process for the preparation of n-butane from isobutane, characterized in that, The method comprises: contacting an isobutane raw material with a catalyst under hydrogenation conditions and under n-paraffinization reaction conditions; The catalyst comprises an active matrix and an active metal component supported on the active matrix; wherein the active matrix comprises an acidic active component SO4 2- ZrO2, an all-silica molecular sieve having MFI structure and alumina; the active metal component is Pt and / or Pd; In the catalyst, the density of strong acid sites is 0.1-1 μmol / m 2 .

2. The method of claim 1, wherein, The content of the active matrix is 99-99.95wt% based on the total mass of the catalyst; and the content of the active metal component is 0.05-1wt% based on elements.

3. The method of claim 2, wherein, The content of the active matrix is 99.5-99.9wt% based on the total mass of the catalyst; and the content of the active metal component is 0.1-0.5wt% based on elements.

4. The method of any of claims 1-3, wherein, The density of strong acid sites in the catalyst is 0.2-0.7 μmol / m 2 .

5. The method of claim 4, wherein, The molar ratio of the amount of strong acid to the amount of weak acid in the catalyst is 4-8:

1.

6. The method of any of claims 1-3, wherein, The active matrix comprises zirconium element, silicon element, aluminum element and sulfur element, and the content of zirconium oxide, silicon oxide, aluminum oxide and SO3 in the active matrix is 30-90wt%, 1-35wt%, 5-50wt% and 1-10wt% respectively based on the total mass of the active matrix.

7. The method of claim 6, wherein, The content of zirconium oxide, silicon oxide, aluminum oxide and SO3 in the active matrix is 50-80wt%, 5-30wt%, 5-30wt% and 2-8wt% respectively based on the total mass of the active matrix.

8. The method of any of claims 1-3, wherein, The mass ratio of SO3 to ZrO2 is (0.02-0.12):

1.

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

1.

10. The method of any of claims 1-3, wherein, The mass ratio of the mass of the acidic active component calculated based on ZrO2 to the mass of the all-silica molecular sieve calculated based on SiO2 in the active matrix is 1:(0.1-1).

11. The method of claim 10, wherein, The mass ratio of the mass of the acidic active component calculated based on ZrO2 to the mass of the all-silica molecular sieve calculated based on SiO2 in the active matrix is 1:(0.15-0.5).

12. The method of any of claims 1-3, wherein, The isobutane normalization reaction conditions include: reaction temperature is 150-250℃, pressure is 1-4 MPa, mass space velocity of isobutane raw material is 0.5-10 h -1 , hydrogen / hydrocarbon molar ratio is 0.02-0.

3.

13. The method of claim 12, wherein, The isobutane normalization reaction conditions include: reaction temperature is 180-230℃, pressure is 1.5-3.5MPa, mass space velocity of isobutane raw material is 1-5h -1 , hydrogen / hydrocarbon molar ratio is 0.03-0.

2.

14. The method of any one of claims 1-3, wherein, The isobutane raw material comprises isobutane and optional impurity components.

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

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

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

18. The method of claim 14, wherein, The impurity components are selected from at least one of C1-C3 alkanes, n-butane, C5+ alkanes, water and sulfur element.

19. The method of claim 18, wherein, The content of C1-C3 alkanes in the isobutane raw material is less than 1wt%.

20. The method of claim 19, wherein, The content of C1-C3 alkanes in the isobutane raw material is less than 0.5wt%.

21. The method of claim 18, wherein, The content of n-butane in the isobutane raw material is less than 2wt%.

22. The method of claim 21, wherein, The content of n-butane in the isobutane raw material is less than 1wt%.

23. The method of claim 18, wherein, The content of C5+ alkanes in the isobutane raw material is less than 1.5wt%.

24. The method of claim 23, wherein, The content of C5+ alkanes in the isobutane raw material is less than 1wt%.

25. The method of claim 18, wherein, The content of water in the isobutane raw material is less than 5ppmw.

26. The method of claim 25, wherein, The content of water in the isobutane raw material is less than 3ppmw.

27. The method of claim 18, wherein, The content of sulfur element in the isobutane raw material is less than 10ppmw.

28. The method of claim 27, wherein, The content of sulfur element in the isobutane raw material is less than 5ppmw.

29. The method of any one of claims 1-3, wherein, The method further comprises preheating the isobutane feedstock and hydrogen to the isobutane normalization reaction temperature prior to contacting with the catalyst.

30. The method of claim 29, wherein, The preheating comprises a first stage preheating and a second stage preheating, and the first stage preheating is performed by heat exchange between the product of the isobutane normalizing reaction and the isobutane feedstock and / or hydrogen.

31. The method of any one of claims 1-3, wherein, The method further comprises separating and purifying the product of the contacting, and using the separated isobutane to provide at least part of the isobutane feedstock.

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