Method for preparing olefins and n-alkanes through catalytic dehydrogenation of alkanes

Abstract

The invention relates to the field of alkane dehydrogenation, and discloses a method for preparing olefin and n-alkane through catalytic dehydrogenation of alkane, which comprises the following steps: (1) carrying out n-isomerization separation on an alkane raw material flow to obtain a first isoalkane flow, and carrying out catalytic dehydrogenation reaction on the first isoalkane flow to obtain a dehydrogenation reaction flow; (2) separating the dehydrogenation reaction material flow to obtain an isoolefin product material flow, a second isoparaffin material flow and a light component material flow; (3) carrying out a normalizing reaction on the second isoparaffin material flow to obtain a normalizing reaction product material flow; and (4) carrying out normal isomerization separation on the normalizing reaction product flow. According to the method, on the premise that the dehydrogenation reaction load is not changed, the low-carbon alkane circulation amount is reduced, and the energy consumption of the device is reduced; in addition, a new product n-alkane is obtained, and the product structure is optimized.

Description

Technical Field

[0001] The present invention relates to the field of alkane dehydrogenation, and in particular to a method for preparing olefins and normal alkanes by catalytic dehydrogenation of alkanes. Background Art

[0002] Light olefins, particularly C2-C4 olefins, are essential raw materials for organic synthesis. Driven by growing demand for downstream olefin derivatives, global demand for C2-C4 olefins continues to grow, and the market outlook remains positive. However, with the rapid development of shale gas, the feedstock for steam cracking to produce olefins has become lighter, leading to a continuous decline in the production of C3-C4 olefins produced through steam cracking. This has directly resulted in traditional processes, such as steam cracking, being unable to meet the growing demand for C3-C4 olefins. Against this backdrop, light alkane dehydrogenation technology, with its high selectivity and high yield, has emerged as a key method for C3-C4 olefin production. Isobutylene, in particular, is a key intermediate in the synthesis of various petrochemical products and a crucial raw material for producing high-value-added products such as methyl methacrylate (MMA), butyl rubber, polyisobutylene, MTBE, and alkylated gasoline.

[0003] Furthermore, low-carbon n-alkanes have garnered significant attention in recent years. This is partly due to their importance as a steam cracking feedstock, effectively increasing ethylene and propylene yields, and partly due to rising demand for downstream products, particularly maleic anhydride (hereinafter referred to as "maleic anhydride"). Maleic anhydride, a commonly used chemical raw material, is used in the production of a range of chemical products, including calcium carbonate modification additives, foaming soap detergents, water-based lubricant rust inhibitors, and polymer resins. In the domestic market, over 80% of maleic anhydride is produced via the n-butane oxidation process.

[0004] Because the dehydrogenation of light alkanes is a reversible, endothermic reaction constrained by thermodynamic equilibrium, the single-pass conversion rate of alkanes during the catalytic dehydrogenation process is low. Consequently, a large amount of unconverted light alkanes must be recycled to the dehydrogenation reactor, significantly increasing the unit's energy consumption. Therefore, feeding this unconverted light alkanes into the normalization reactor not only yields normal alkanes, an important chemical raw material, but also reduces the unit's recycling volume, significantly lowering the unit's energy consumption.

[0005] CN201410124540.0 discloses a method for preparing MTBE or isobutylene from mixed C4 alkanes, comprising the following steps: (1) a first stage hydrogenation to remove unsaturated hydrocarbons in the mixed C4 alkanes; (2) a second stage hydrogenation to remove sulfur and / or nitrogen as impurities in the mixed C4 raw material; (3) dehydrogenation to convert the mixed C4 into n-butene and isobutylene; (4) isomerization to pass the dehydrogenation product into an isomerization unit to isomerize the n-butene therein into isobutylene; and (5) etherification to pass the isomerization product into an etherification unit to react the isobutylene therein with methanol to generate the MTBE. This method can improve the comprehensive utilization rate of C4 alkanes and the yield of MTBE.

[0006] CN201210189762.1 relates to a method for preparing butadiene from normal alkanes, comprising the following steps: (1) subjecting normal alkanes to a dehydrogenation reaction in the presence of a dehydrogenation catalyst to obtain a hydrocarbon mixture containing olefins; (2) subjecting the hydrocarbon mixture containing olefins to a cyclization reaction in the presence of a cyclization catalyst to obtain a hydrocarbon mixture containing six-membered cyclic hydrocarbons; (3) subjecting the hydrocarbon mixture containing six-membered cyclic hydrocarbons to a hydrogenation reaction in the presence of a hydrogenation catalyst to obtain a hydrocarbon mixture containing cyclohexane and / or alkylcyclohexanes; and (4) subjecting the hydrocarbon mixture containing cyclohexane and / or alkylcyclohexanes to a steam cracking reaction as at least a portion of the cracking feedstock. The method for preparing butadiene from normal alkanes described in this method can achieve a higher butadiene yield and a lower methane yield, thereby reducing the cold box energy consumption during the cracking gas separation process.

[0007] US14 / 278040 discloses a method for producing butadiene by dehydrogenating n-butane, comprising the following steps: (1) conveying a stream containing n-butane to a dehydrogenation reactor to produce a dehydrogenated product stream containing n-butane and butenes; (2) separating olefins and alkanes in the dehydrogenated product stream; (3) conveying the olefin stream to an oxidative dehydrogenation reactor to produce a product stream containing butadiene; and (4) returning the alkanes stream to the dehydrogenation reactor.

[0008] CN201210118253.X provides an embodiment of a method for preparing propylene from paraffins, the method comprising the following steps: (1) combining an effluent containing propylene and propane from a paraffin dehydrogenation reactor with a waste gas stream containing propane to form a combined effluent stream; (2) separating the combined effluent stream into a propylene product stream and a propane-rich recycle stream; and (3) introducing the propane-rich recycle stream into a paraffin dehydrogenation reactor operated under dehydrogenation conditions to convert the propane in the propane-rich recycle stream into propylene.

[0009] CN201910833923.8 discloses a normalization technology, a method for preparing butene-2 ​​from isobutylene, comprising: (1) feeding isobutylene into a normalization unit to contact with a normalization catalyst to obtain a reaction product rich in normal butenes; (2) feeding the normalization reaction product of step (1) into a butene double bond isomerization unit to contact with a double bond isomerization catalyst to cause a double bond isomerization reaction of butene-1, thereby converting butene-1 into butene-2; and (3) feeding the butene double bond isomerization reaction product into a fractionation tower, discharging butene-2 ​​product from the side of the tower, discharging C5+ heavy components from the bottom of the tower, and returning the mixture of isobutylene and butene-1 discharged from the top of the tower to the normalization unit. This method can prepare butene-2 ​​from isobutylene for use in preparing high-octane alkylate oil, providing an effective way to increase the value of isobutylene and MTBE.

[0010] Therefore, a new process method that combines the dehydrogenation and normalization technologies of low-carbon alkanes is needed to improve the efficiency of the existing process flow for producing olefins and normal alkanes and optimize the product structure. Summary of the Invention

[0011] The present invention aims to overcome the problems of low single-pass conversion of alkanes and increased energy consumption of the device in the prior art catalytic dehydrogenation process for olefins, and to provide a method for catalytic dehydrogenation of alkanes to produce olefins and normal alkanes. The method can reduce the circulation amount of low-carbon alkanes and reduce the energy consumption of the device without changing the dehydrogenation reaction load. In addition, a new product, normal alkanes, is obtained, thereby optimizing the product structure.

[0012] In order to achieve the above object, the present invention provides a method for catalytic dehydrogenation of alkanes to produce olefins and normal alkanes, which comprises the following steps:

[0013] (1) performing normal isomerization separation on an alkane feed stream to obtain a first isoalkane stream, and performing a catalytic dehydrogenation reaction on the first isoalkane stream to obtain a dehydrogenation reaction stream;

[0014] (2) separating the dehydrogenation reaction stream to obtain an isomerized olefin product stream, a second isomerized alkane stream, and a light component stream;

[0015] (3) subjecting the second isoparaffin stream to a normalization reaction to obtain a normalization reaction product stream;

[0016] (4) subjecting the normalization reaction product stream to normal isomerization separation.

[0017] Preferably, the olefin content in the normalization reaction feed stream is less than 1000 wppm, preferably 0-600 wppm.

[0018] Preferably, the content of heavy components in the normalization reaction feed stream is less than 2% by mass, preferably 0-1% by mass.

[0019] Preferably, the water content in the normalization reaction feed stream is ≤5 ppm.

[0020] The above technical solution has the following beneficial effects: the method provided by the present invention combines the dehydrogenation of low-carbon alkanes with normalization technology, and utilizes the normalization technology to convert unreacted low-carbon alkanes into high-value normal alkane products, thereby optimizing the product structure while reducing the energy consumption of the device, greatly increasing the efficiency of the device, and helping to improve the competitiveness of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic process flow diagram of an embodiment of the present invention;

[0022] Figure 2 It is a schematic process flow diagram of existing alkane dehydrogenation;

[0023] Figure 3 It is a schematic process flow chart of the existing normalization reaction.

[0024] Description of Reference Numerals

[0025] Figure 1 and Figure 2

[0026] 1-Normal isomer separation unit 2-Catalytic dehydrogenation reaction unit 3-Compression drying unit

[0027] 4-Cooling separation unit 5-Distillation separation unit 6-Hydrogenation treatment unit

[0028] 7-Normalization reaction unit 10-Alkane feed stream 11-First isoparaffin stream 12-Heavy component stream 13-Dehydrogenation reaction stream 15-Compression and drying post-processing stream 16-Hydrogen stream 17-Liquefied component stream 19-Light component stream

[0029] 21-Isoolefin product stream 22-Second isoalkane stream 23-Normalization reaction feed stream 24-Dry hydrogen stream 25-Normalization reaction product stream 26-Normal alkane product stream

[0030] Figure 3

[0031] 8-Normalization unit Normalization unit 9-Normalization unit Normal isomerization 31-Isoparaffin feedstock

[0032] Meta-unit

[0033] 33-Mixed isoparaffin feedstock 35-Normalization unit reaction effluent 36-Isoparaffin recycle stream

[0034] 37-Normalization unit normal alkanes

[0035] Product Logistics DETAILED DESCRIPTION

[0036] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[0037] In one aspect, the present invention provides a method for catalytic dehydrogenation of alkanes to produce olefins and normal alkanes, which comprises the following steps:

[0038] (1) performing normal isomerization separation on an alkane feed stream to obtain a first isoalkane stream, and performing a catalytic dehydrogenation reaction on the first isoalkane stream to obtain a dehydrogenation reaction stream;

[0039] (2) separating the dehydrogenation reaction stream to obtain an isomerized olefin product stream, a second isomerized alkane stream, and a light component stream;

[0040] (3) subjecting the second isoparaffin stream to a normalization reaction to obtain a normalization reaction product stream;

[0041] (4) subjecting the normalization reaction product stream to normal isomerization separation.

[0042] In the present invention, the dehydrogenation and normalization technologies of light alkanes are combined, and a set of circulation and separation systems can be adopted. The normalization technology is used to convert unreacted light alkanes into high-value normal alkane products. Without changing the dehydrogenation reaction load, the circulation amount of light alkanes is reduced, thereby reducing the energy consumption of the device.

[0043] According to the present invention, preferably, the alkane feed stream is selected from at least one of light alkanes having 4 to 6 carbon atoms. More preferably, the alkane feed stream is a mixture of isobutane and n-butane. The technical solution provided by the present invention relates to the entire field of light alkane dehydrogenation and is applicable to the field of butane / isobutane dehydrogenation. It can increase the output of n-butane product and reduce the amount of isobutane recycle without changing the butane / isobutane dehydrogenation reaction load.

[0044] According to the present invention, preferably, the normal isomerization separation in step (1) and the normal isomerization separation in step (4) are carried out in the same normal isomerization separation unit; in this case, the alkane feed stream and the normalization reaction product stream are subjected to normal isomerization separation to obtain a first isoparaffin stream, a normal alkane product stream and a heavy component stream.

[0045] In the present invention, preferably, the first isoparaffin stream obtained by normal isomer separation in the same normal isomerization unit is subjected to a catalytic dehydrogenation reaction. By recycling the first isoparaffin stream, the utilization rate of the device can be improved and the energy consumption of the device can be reduced.

[0046] In the present invention, the normal isomerization separation conditions are not particularly limited, as long as the first isoparaffin stream, the normal alkane product stream and the heavy component stream can be obtained.

[0047] In the present invention, preferably, the feed mass ratio of the normalization reaction product stream to the alkane feed stream can be adaptively adjusted by those skilled in the art.

[0048] In the present invention, preferably, the catalytic dehydrogenation reaction is carried out in a catalytic dehydrogenation reaction unit in the presence of a dehydrogenation catalyst. The dehydrogenation catalyst can be any conventional dehydrogenation catalyst that can achieve a catalytic dehydrogenation effect, and is preferably selected from the Pt series and / or Cr series.

[0049] In the present invention, the catalytic dehydrogenation reaction unit is a conventional catalytic dehydrogenation reaction unit in the art. Preferably, the catalytic dehydrogenation reaction unit is composed of 2-6 dehydrogenation reactors operated in series, and a heating furnace is provided between each reactor; wherein the dehydrogenation reactor is selected from a combination of one or more reactors selected from moving bed, fixed bed and fluidized bed.

[0050] According to the present invention, preferably, the reaction conditions of the catalytic dehydrogenation reaction include: reaction temperature of 450-550°C, reactor inlet pressure of 0.01-1 MPa, hydrogen-to-hydrocarbon molar ratio of 0.1-10, weight hourly space velocity of 1-12 h -1 Preferably, the reaction temperature is 470-510°C, the reactor inlet pressure is 0.01-0.1 MPa, the hydrogen-to-hydrocarbon molar ratio is 0.3-0.6, and the weight hourly space velocity is 2-4 h -1 .

[0051] According to the present invention, preferably, the separation in step (2) comprises the following steps:

[0052] (2-1) compressing, drying, and cooling the dehydrogenation reaction stream to obtain a hydrogen stream and a liquefied component stream;

[0053] (2-2) The liquefied component stream is subjected to distillation separation to obtain an isoolefin product stream, a second isoparaffin stream, and a light component stream.

[0054] In the present invention, preferably, the compression drying is carried out in a compression drying unit, and the dehydrogenation reaction flow is compressed and dried to obtain a compression dried logistics, which is further cooled and separated in a cooling and separation unit to obtain a hydrogen logistics and a liquefied component logistics.

[0055] In the present invention, the cooling separation is mainly for separating hydrogen and methane.

[0056] In the present invention, the liquefied component stream comprises isoparaffins and isoolefins and a small amount of side reaction products, wherein the total mass fraction of isoparaffins and isoolefins is greater than 95%. The side reaction products are mainly C2-C6 hydrocarbons.

[0057] In the present invention, there is no particular limitation on the conditions of compression drying and cooling separation, and those skilled in the art can make adaptive adjustments as needed.

[0058] According to the present invention, preferably, the liquefied component stream is subjected to distillation separation in a distillation separation unit. Those skilled in the art can adapt the distillation separation conditions to achieve distillation separation to obtain an isoolefin product stream, a second isoparaffin stream, and a light component stream. Those skilled in the art can adapt the distillation separation conditions to ensure that the mass fraction of isoolefins in the isoolefin product stream is greater than 99.5%, and the mass fraction of light components in the second isoparaffin stream is less than 1%.

[0059] In the present invention, light components have the conventional meaning in the art. The light component stream is a low-carbon alkane stream with a carbon number less than that of the alkane feed stream. For example, the alkane feed stream is a C4 alkane stream, corresponding to C3 - The alkane is a light component stream, and the alkane raw material stream is a C5 alkane stream, corresponding to C4 - Alkanes are the light component stream.

[0060] In the present invention, the heavy component has the conventional meaning in the art. The heavy component stream is a low-carbon alkane stream with a carbon number greater than that of the alkane feed stream. For example, the alkane feed stream is a C4 alkane stream, corresponding to C5 + The alkane is a heavy component stream, and the alkane raw material stream is a C5 alkane stream, corresponding to C6 + Alkanes are the heavy component stream.

[0061] According to the present invention, preferably, the heavies content in the normalization reaction feed stream is less than 2% by mass, preferably 0-1% by mass. A low heavies content in the normalization reaction feed stream helps to improve the isoparaffin conversion rate and normal paraffin selectivity in the normalization reaction.

[0062] According to the present invention, preferably, the method further comprises: subjecting the second isoparaffin stream to hydrogenation treatment to obtain a normalization reaction feed stream, and subjecting the normalization reaction feed stream to the normalization reaction described in step (3).

[0063] According to the present invention, preferably, the hydrotreatment is carried out in a hydrotreatment unit, and the conditions of the hydrotreatment include: a reaction temperature of 20-150°C, a reaction pressure of 3-4.5 MPa, a volume space velocity of 1-20 h -1 The reaction temperature is preferably 30-80°C, the reaction pressure is 3-4 MPa, and the volume space velocity is 6-15 h -1 .

[0064] According to the present invention, the olefin content in the normalization reaction feed stream is preferably less than 1000 wppm, preferably 0-600 wppm. Hydrotreating the normalization reaction feed stream to remove olefins and alkynes can reduce the impact of olefins and alkynes on the normalization reaction and increase the yield of normal paraffins.

[0065] According to the present invention, preferably, the normalization reaction is carried out in a normalization reaction unit in the presence of a normalization catalyst.

[0066] In the present invention, the normalization reaction further comprises being carried out under the condition of introducing a dry hydrogen flow. The amount of the dry hydrogen flow introduced can be adjusted by those skilled in the art according to the actual reaction situation.

[0067] According to the present invention, preferably, the normalization reaction conditions include: reaction temperature 150-250 ° C, reaction pressure 1-4 MPa, hydrogen-to-hydrocarbon molar ratio 0.01-1, weight hourly space velocity 0.1-6h -1 More preferably, the reaction temperature is 150-200°C, the reaction pressure is 2-4 MPa, the hydrogen-to-hydrocarbon molar ratio is 0.01-0.5, and the weight hourly space velocity is 0.1-3 h -1 .

[0068] According to the present invention, preferably, the normalization catalyst comprises a composite support and a Group VIII metal in an amount of 0.001-2% by mass based on the support.

[0069] According to the present invention, preferably, the composite carrier contains zirconium, silicon, aluminum and sulfur. Calculated as zirconium oxide, silicon oxide, aluminum oxide and SO3, the composite carrier includes 30-60 mass% of zirconium oxide, 0.01-5 mass% of silicon oxide, 35-60 mass% of aluminum oxide and 1-5 mass% of SO3.

[0070] According to the present invention, preferably, the composite support comprises 40-57 mass % of zirconium oxide, 0.01-2 mass % of silicon oxide, 40-55 mass % of aluminum oxide and 2-4 mass % of SO 3 .

[0071] According to the present invention, preferably, the Group VIII metal is selected from at least one of palladium, platinum and nickel.

[0072] The present invention has no particular limitation on the preparation method of the normalization catalyst, and the preparation method can be carried out according to conventional techniques in the art.

[0073] In the present invention, the reaction pressure refers to the gauge pressure.

[0074] In the present invention, preferably, the normalization catalyst is SO4 2- / ZrO2-Al2O3 system catalyst, using the above catalyst for normalization reaction, it is necessary to ensure that there is no water during the reaction process, and further combined with the reaction conditions of the present invention, can significantly improve the normalization reaction efficiency and reduce the energy consumption of the device.

[0075] In some embodiments of the present invention, according to Figure 1 In the process flow shown, the alkane feedstock stream 10 passes through a pretreatment unit (not shown) to remove impurities such as sulfur, nitrogen, and metals in the feedstock, and then enters the normal isomerization separation unit 1 for normal isomerization separation to obtain a first isoalkane stream 11; wherein, the first isoalkane stream 11 enters the catalytic dehydrogenation reaction unit 2, contacts with the dehydrogenation catalyst, and obtains a dehydrogenation reaction stream 13; the dehydrogenation reaction stream 13 is sent to the compression and drying unit 3 to obtain a compression and drying treated stream 15, and the compression and drying treated stream 15 is sent to the cooling and separation unit 4 for cooling and separation to obtain a hydrogen stream 16 and a liquefied component stream 17.

[0076] The liquefied component stream 17 enters the distillation separation unit 5, where it is subjected to distillation separation to obtain a light component stream 19, an isoolefin product stream 21, and a second isoparaffin stream 22. The second isoparaffin stream 22 is fed to the hydrotreating unit 6 to obtain a normalization reaction feed stream 23. The normalization reaction feed stream 23 is fed to the normalization reaction unit 7, where it contacts a normalization catalyst and undergoes a normalization reaction with a dry hydrogen stream 24 to obtain a normalization reaction product stream 25. The normalization reaction product stream 25 is then returned to the normal-isomerization separation unit 1, where it undergoes normal-isomerization separation together with the alkane feed stream 10 to obtain a normal-paraffin product stream 26, a first isoparaffin stream 11, and a heavy component stream 12.

[0077] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, the reagents and materials used can be obtained commercially;

[0078] Solid superacid isomerization catalyst RISO-C was purchased from Sinopec;

[0079] Catalytic dehydrogenation catalyst PST-100 was purchased from Sinopec;

[0080] The contents of heavy components and olefins in the normalization reaction feed stream are measured by gas chromatography PONA method;

[0081] The water content in the normalization reaction feed stream is measured by an online water content analyzer.

[0082] Preparation example of normalization catalyst

[0083] (a) Preparation of SO4 2- / ZrO2-Al2O3 support

[0084] Take 31.8g of zirconium hydroxide powder (zirconium oxide content 78.5% by mass, containing a small amount of silicon), grind it thoroughly and set aside. Add 50mL of 0.5mol / L sulfuric acid aqueous solution to a beaker, and then add 15mL of deionized water to form a solution. Pour the zirconium hydroxide powder into the solution and stir it continuously to mix it evenly. Let it stand at room temperature for 3h, then place it in an oven and dry it at 60℃ for 12h and 120℃ for 12h. Grind the dried solid into a fine powder, then mix it evenly with 33.1g of SB powder (aluminum oxide content 75% by mass), and then add 19.2mL of 5.0% by mass nitric acid aqueous solution to dissolve it. After kneading evenly, extrude it into strips. Dry the wet strips at 120℃ for 10h and calcine them at 680℃ for 4h to obtain SO4 2- / ZrO2-Al2O3 carrier.

[0085] (b) Preparation of Pt-SO4 2- / ZrO2-Al2O3 catalyst

[0086] Take 20.0g of SO4 prepared in step (a) 2- / ZrO2-Al2O3 carrier was added to 10.0g of aqueous solution containing 0.04g of chloroplatinic acid and 0.1g of nitric acid, and immersed at 25℃ for 3h. The impregnated solid was dried at 120℃ for 10h and calcined at 550℃ for 4h to obtain catalyst Pt-SO4 2- / ZrO2-Al2O3, denoted as catalyst A.

[0087] XRF data of normalized catalyst w / %

[0088]

[0089] Example 1

[0090] The reaction was carried out according to the following process flow

[0091] (1) The alkane feedstock stream 10 (a fresh mixed C4 feedstock stream, comprising: C4 normal alkane and C4 isoalkane, with a mass ratio of 0.25:1) is fed to a pretreatment unit (not shown in the figure), and after removing impurities such as sulfur, nitrogen and metals from the feedstock, it is fed to a normal isomerization separation unit 1 for normal isomerization separation to obtain a first isoalkane stream 11 (isobutane). The first isoalkane stream 11 is fed to a catalytic dehydrogenation reaction unit 2, and is contacted with a dehydrogenation catalyst PST-100, and a catalytic dehydrogenation reaction is carried out in a dehydrogenation reactor. The catalytic dehydrogenation reaction unit comprises four fixed-bed reactors connected in series. The catalytic dehydrogenation reaction conditions are as follows: a reaction temperature of 520°C, a reactor inlet pressure of 0.1 MPa, a hydrogen-to-hydrocarbon molar ratio of 0.5, and a weight hourly space velocity of 2.5 h -1 , obtaining a dehydrogenation reaction stream 13;

[0092] (2) The dehydrogenation reaction stream 13 is fed into the compression and drying unit 3 for compression and drying to obtain a compression and drying treated stream 15. The compression and drying treated stream 15 is fed into the cooling and separation unit 4 for cooling and separation to obtain a hydrogen stream 16 and a liquefied component stream 17 (rich in isobutylene and isobutane). The liquefied component stream 17 is fed into the distillation and separation unit 5 for distillation and separation to obtain a light component stream 19, an isoolefin product stream 21 (isobutylene), and a second isoparaffin stream 22 (isobutane).

[0093] (3) The second isoparaffin stream 22 is fed to the hydrotreating unit 6 for hydrotreating to obtain a normalization reaction feed stream 23. The conditions for the hydrotreating are: a reaction temperature of 45°C, a reactor inlet pressure of 3.8 MPa, a hydrogen-to-hydrocarbon molar ratio of 0.5, and a weight hourly space velocity of 8 h -1 The olefin content in the normalization reaction feed stream 23 is 350wppm, the water content is 4.2wppm, and the heavy component content is 0.7% by mass. The normalization reaction feed stream 23 is fed to the normalization reaction unit 7, contacts with the catalyst A, and undergoes normalization reaction with the dry hydrogen stream 24. The normalization reaction conditions are: reaction temperature of 180°C, reaction pressure of 3.5MPa, hydrogen-to-hydrocarbon molar ratio of 0.5, and weight hourly space velocity of 1.5h -1 , obtaining a normalization reaction product stream 25 (rich in n-butane and isobutane);

[0094] (4) The normalization reaction product stream 25 is sent to the normal isomerization separation unit 1 for normal isomerization separation with the alkane feed stream 10 to obtain a normal alkane product stream 26, a first isoalkane stream 11 and a heavy component stream 12.

[0095] Example 2

[0096] The reaction was carried out according to the process flow of Example 1, except that the water content in the normalization reaction feed stream 23 was 12 wppm.

[0097] Example 3

[0098] The reaction was carried out according to the process flow of Example 1, except that the water content in the normalization reaction feed stream 23 was 50 wppm.

[0099] Example 4

[0100] The reaction was carried out according to the process flow of Example 1, except that the olefin content in the normalization reaction feed stream 23 was 2200 wppm.

[0101] Example 5

[0102] The reaction was carried out according to the process flow of Example 1, except that the olefin content in the normalization reaction feed stream 23 was 4800 wppm.

[0103] Example 6

[0104] The reaction was carried out according to the process flow of Example 1, except that the content of heavy components in the normalization reaction feed stream 23 was 2.7 wt%.

[0105] Example 7

[0106] The reaction was carried out according to the process flow of Example 1, except that the content of heavy components in the normalization reaction feed stream 23 was 4.5 wt%.

[0107] Comparative Example 1

[0108] according to Figure 2 The existing process flow of alkane dehydrogenation is shown in FIG. Figure 3 The existing normalization process is to dehydrogenate isobutylene and n-butane, and the reaction conditions of each unit are the same as those in Example 1.

[0109] (1) An alkane feed stream 10 (with the same composition as in Example 1) is subjected to a pretreatment unit (not shown) to remove impurities such as sulfur, nitrogen, and metals from the feed, and then fed to a normal isomerization separation unit 1 for normal isomerization separation to produce a first isoalkane stream 11 (isobutane). The first isoalkane stream 11 is fed to a catalytic dehydrogenation reaction unit 2, where it contacts a dehydrogenation catalyst for catalytic dehydrogenation to produce a dehydrogenation reaction stream 13.

[0110] (2) The dehydrogenation reaction stream 13 is fed into the compression and drying unit 3 for compression and drying to obtain a compressed and dried stream 15. The compressed and dried stream 15 is fed into the cooling and separation unit 4 for cooling and separation to obtain a hydrogen stream 16 and a liquefied component stream 17 (rich in isobutylene and isobutane). The liquefied component stream 17 is fed into the distillation separation unit 5 to obtain a light component stream 19, an isoolefin product stream 21 (isobutylene), and a second isoparaffin stream 22 (isobutane).

[0111] (3) The second isoparaffin stream 22 is fed to the hydrotreating unit 6 for hydrotreating to obtain a normalization reaction feed stream 23, which is then fed to the normal isomerization separation unit 1 for normal isomerization separation with the supplemented alkane feed stream 10 to obtain a first isoparaffin stream 11 and a heavy component stream 12.

[0112] (4) An isoparaffin feedstock 31 (isobutane) having the same composition as the normalization reaction feed stream 23 is mixed with an isoparaffin recycle stream 36 to produce a mixed isoparaffin feedstock 33. The mixed isoparaffin feedstock 33 is fed to the normalization unit 8 of the normalization device and contacted with the catalyst RISO-C for a normalization reaction. The normalization reaction conditions are the same as those in Example 1, yielding a normalization device reaction effluent 35 containing isoparaffins and normal paraffins. The normalization device reaction effluent 35 is fed to the normalization device normal isomerization separation unit 9 to yield an isoparaffin recycle stream 36 and a normalization device normal paraffin product stream 37 (n-butane).

[0113] The reaction conditions of each unit of the process flow of the embodiment and the comparative example are shown in Table 1.

[0114] Isoparaffin conversion rate = (isoparaffin content in the second isoparaffin stream - isoparaffin content in the normal paraffin product stream) / isoparaffin content in the second isoparaffin stream × 100%;

[0115] Normal alkane yield = normal alkane production in the normal alkane product stream / mass of the second isoalkane stream × 100%.

[0116] Table 1

[0117]

[0118]

[0119] The results in Table 1 show that the process flow for catalytic dehydrogenation to produce isoolefins and normalization reaction using the method of the embodiment of the present invention has a significantly higher n-butane yield and isobutane conversion rate than the process flow of the comparative example. Based on the total energy consumption of the process flow of comparative example 1, the method of the embodiment reduces the cycle energy consumption of the device.

[0120] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing olefins and normal alkanes by catalytic dehydrogenation of alkanes, characterized in that: The following steps are involved: (1) subjecting an alkane feed stream to normal isomerization separation to obtain a first isoalkane stream, and subjecting the first isoalkane stream to a catalytic dehydrogenation reaction to obtain a dehydrogenation reaction stream; (2) separating the dehydrogenation reaction stream to obtain an isoolefin product stream, a second isoalkane stream, and a light component stream; (3) subjecting the second isoparaffin stream to a normalization reaction to obtain a normalization reaction product stream; (4) subjecting the normalization reaction product stream to normal-isomerization separation.

2. The method according to claim 1, wherein: The separation in step (2) comprises the following steps: (2-1) compressing, drying and cooling the dehydrogenation reaction stream to obtain a hydrogen stream and a liquefied component stream; (2-2) The liquefied component stream is separated by distillation to obtain an isoolefin product stream, a second isoalkane stream and a light component stream.

3. The method according to claim 1 or 2, wherein: The method further comprises: subjecting the second isoparaffin stream to hydrogenation treatment to obtain a normalization reaction feed stream, and subjecting the normalization reaction feed stream to the normalization reaction described in step (3); Preferably, the hydroprocessing conditions include: reaction temperature of 20-150°C, reaction pressure of 3-4.5 MPa, volume space velocity of 1-20 h -1 .

4. A method according to any one of claims 1 to 3, wherein: The normal isomerization separation in step (1) and the normal isomerization separation in step (4) are carried out in the same normal isomerization separation unit; in this case, the alkane feedstock stream and the normalization reaction product stream are subjected to normal isomerization separation to obtain a first isoalkane stream, a normal alkane product stream and a heavy component stream.

5. The method according to claim 4, wherein: The content of heavy components in the normalization reaction feed stream is less than 2% by mass, preferably 0-1% by mass; and / or, the olefin content in the normalization reaction feed stream is less than 1000wppm, preferably 0-600wppm; And / or, the water content in the normalization reaction feed stream is ≤5wppm.

6. The method according to any one of claims 1 to 5, wherein: The reaction conditions of the normalization reaction include: The reaction temperature is 150-250℃, the reaction pressure is 1-4MPa, the hydrogen-to-hydrocarbon molar ratio is 0.01-1, and the weight hourly space velocity is 0.1-6h -1 ; Preferably, the reaction temperature is 150-200°C, the reaction pressure is 2-4 MPa, the hydrogen-to-hydrocarbon molar ratio is 0.01-0.5, and the weight hourly space velocity is 0.1-3 h -1 .

7. The method according to any one of claims 1 to 6, wherein: The alkane feedstock stream is selected from at least one of low-carbon alkanes having 4 to 6 carbon atoms.

8. The method according to any one of claims 1 to 7, wherein: The reaction conditions of the catalytic dehydrogenation reaction include: The reaction temperature is 450-550°C, the reactor inlet pressure is 0.01-1MPa, the hydrogen-to-hydrocarbon molar ratio is 0.1-10, and the weight hourly space velocity is 1-12h -1 ; Preferably, the reaction temperature is 470-510°C, the reactor inlet pressure is 0.01-0.1 MPa, the hydrogen-to-hydrocarbon molar ratio is 0.3-0.6, and the weight hourly space velocity is 2-4 h -1 .

9. The method according to any one of claims 1 to 8, wherein: The normalization reaction is carried out in the presence of a normalization catalyst; Preferably, the normalization catalyst comprises a composite support and a Group VIII metal in an amount of 0.001-2 mass % based on the composite support.

10. The method according to claim 9, wherein: The composite carrier contains zirconium, silicon, aluminum and sulfur. Calculated by zirconium oxide, silicon oxide, aluminum oxide and SO3, the composite carrier includes 30-60 mass% of zirconium oxide, 0.01-5 mass% of silicon oxide, 35-60 mass% of aluminum oxide and 1-5 mass% of SO3; Further preferably, the composite support comprises 40-57 mass % of zirconium oxide, 0.01-2 mass % of silicon oxide, 40-55 mass % of aluminum oxide and 2-4 mass % of SO3; Preferably, the Group VIII metal is selected from at least one of palladium, platinum and nickel.

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