A linear alpha-olefin and its preparation method

Abstract

The present invention provides a linear alpha-olefin and a preparation method thereof. The preparation method comprises the following steps: step S1, using Fischer-Tropsch wax as a raw material, gasifying the Fischer-Tropsch wax and water, and then performing a catalytic cracking reaction under the action of a catalyst to obtain a cracking product; step S2, separating and purifying the cracking product to obtain a linear alpha-olefin; the catalyst is a molecular sieve loaded with an active metal. The present application uses Fischer-Tropsch wax mainly containing straight-chain saturated high-carbon alkanes as a raw material, and performs a catalytic cracking reaction under the action of a catalyst to obtain a linear alpha-olefin (LAO) product with high selectivity and narrow distribution. The carbon number range of the LAO product is mainly concentrated in C7 to C 15 The linear α-olefins prepared by the above method not only have a concentrated carbon number distribution, high selectivity, and are easy to separate, but also have single-carbon LAOs, which enrich downstream products and enhance product performance.

Description

Technical Field

[0001] The invention relates to the application field of wax in coal chemical industry / petrochemical industry, and in particular to a linear alpha-olefin and a preparation method thereof. Background Art

[0002] As an important intermediate product and chemical raw material, linear alpha olefin (LAO) is widely used in many fields such as petrochemicals and fine chemicals. α-olefins with different carbon number ranges have different applications. For example, C4-C8 α-olefins can be used as α-olefin monomers to polymerize with ethylene to prepare linear polyethylene; C6-C 10 The α-olefins and hydroxyl groups can be used to synthesize straight-chain plasticizer alcohols; C8~C 12 α-olefins are often used in the polymerization to produce PAO; C 14 ~C 18 α-olefins can be used to synthesize alkylbenzene salts as lubricating oil additives; C 12 ~C 18 α-olefin sulfonate is prepared by sulfonation and neutralization of α-olefin, which is a widely used anionic detergent.

[0003] The earliest industrial production of α-olefins adopted the paraffin thermal cracking process. The raw wax is heated and melted and mixed with water vapor. After being gasified and preheated in a preheating furnace, it enters a cracking furnace for cracking at high temperature. The liquid phase product obtained after the cracking product is quenched is separated by oil and water to separate the uncracked wax and olefin products. It is well known that the quality of α-olefins obtained by my country's paraffin thermal cracking olefin industry needs to be improved. The LAO raw materials used for the downstream of α-olefins are mostly imported, which seriously restricts the development and application of downstream fine chemicals. Compared with paraffin, the wax produced by the 4 million tons of coal-to-oil Fischer-Tropsch process in Ningdong, Ningxia (referred to as Fischer-Tropsch wax) has the characteristics of low oil content and high content of linear normal alkanes, which is more conducive to the cracking preparation of LAO, and not only produces even-carbon LAO products, but also has a wider range of applications. Although Fischer-Tropsch wax can also refer to the thermal cracking process to prepare α-olefins, it is difficult to control the product distribution due to thermal cracking, and the carbon number distribution of LAO is wide, which increases the cost of downstream applications of the product.

[0004] Patent CN104250559 discloses a production method for preparing α-olefins by thermal cracking of coal wax, using water vapor as diluent gas, under the conditions of temperature of 600-900°C, pressure of 0.1-0.5MPa, weight ratio of water vapor to coal wax of 0.1-5, residence time of 0.1-5 seconds, coal wax is thermally cracked to generate a stream containing α-olefins, and the stream containing α-olefins is separated by gas-liquid separation and distilled to obtain α-olefins. The yield of liquid olefins is 40-50%, and the content of α-olefins in liquid olefins can reach 63%. The process adopted in this patent is similar to traditional paraffin thermal cracking, with a high cracking temperature, and the carbon number distribution of the obtained liquid olefins and the carbon number distribution and structure of α-olefins are not disclosed.

[0005] Most of my country's high-quality α-olefins and α-olefin downstream high-end lubricants are imported, and the market demand is still expanding. Therefore, based on the high-quality Fischer-Tropsch wax produced by my country's coal chemical industry, in view of the high reaction temperature and wide product distribution of the traditional thermal cracking process, the development of new processes and methods to produce high-quality LAO is of great significance for the domestic independent production of high-quality LAO products, alleviating my country's long-term dependence on imports of α-olefins, and breaking the foreign technology monopoly and market monopoly of LAO. Summary of the invention

[0006] The main purpose of the present invention is to provide a linear α-olefin and a preparation method thereof, so as to solve the problems of wide carbon number distribution and poor quality of linear α-olefin in the prior art.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing linear α-olefins is provided, and the preparation method comprises the following steps: step S1, using Fischer-Tropsch wax as raw materials, gasifying Fischer-Tropsch wax and water, and then subjecting the Fischer-Tropsch wax to a catalytic cracking reaction under the action of a catalyst to obtain a cracking product; step S2, separating and purifying the cracking product to obtain a linear α-olefin; the catalyst is a molecular sieve loaded with an active metal.

[0008] Furthermore, the Fischer-Tropsch wax includes liquid wax or solid wax obtained from the refining process from the conventional line to the bottom oil reduction stage.

[0009] Furthermore, the active metal includes any one or a combination of Pt, Fe, Cr, and Zn. Preferably, the active metal includes Pt and Fe.

[0010] Further, the molecular sieve includes any one or more of MFI microporous molecular sieve, FAU microporous molecular sieve, MCM mesoporous molecular sieve and SBA mesoporous molecular sieve. Preferably, the molecular sieve includes any one or more of ZSM-5, Si-1, Y, MCM-41 and SBA-15.

[0011] Furthermore, the content of active metal in the catalyst is 0.1-2.0% of the weight of the carrier. Preferably, the content of platinum in the catalyst is 0.50-1.0%, and the content of iron in the catalyst is 1.0-2.0%.

[0012] Further, the catalyst is obtained by the following preparation method, which comprises: step S01, drying the molecular sieve and evacuating the vacuum to obtain a pretreated supported molecular sieve; preferably, the drying temperature is 80-150° C. and the time is 2-8 hours; preferably, the vacuum degree of the evacuation is 1-200 Pa and the time is 3-5 hours; step S02, adding an active metal salt into water to prepare a complex impregnation solution, mixing it with the supported molecular sieve, and drying it to obtain a catalyst;

[0013] Preferably, in step S02, under ultrasonic conditions, the complex impregnation solution is mixed with the loaded molecular sieve, and the mixed solution is subjected to the ultrasonic-vacuum-standing step for more than 2 times; preferably, the ultrasonic, vacuum and standing step are each performed for no less than 1 hour, and the vacuum degree of the vacuum step is 1 to 200 Pa.

[0014] Furthermore, the temperature of catalytic cracking is 450-600° C.; preferably, the pressure of catalytic cracking is 0-0.8 MPa; more preferably, the reaction time of catalytic cracking is 2-8 seconds.

[0015] Furthermore, step S1 includes the following steps: step S11, liquefying the Fischer-Tropsch wax raw material, and gasifying the liquefied Fischer-Tropsch wax and water to obtain gaseous Fischer-Tropsch wax and water; step S12, passing the gaseous Fischer-Tropsch wax and water into a reactor equipped with a catalyst to carry out a catalytic cracking reaction to obtain a catalytic cracking product; preferably, in step S12, the weight ratio of the gaseous Fischer-Tropsch wax and water is 4 to 8:1; preferably, the reactor is a fixed bed reactor.

[0016] Furthermore, step S2 includes the following steps: step S21, quenching the cracking product and passing it into a separation device to separate linear α-olefins and unreacted raw materials; step S22, returning the unreacted raw materials to the reactor for reaction.

[0017] According to another aspect of the present invention, a linear α-olefin is provided. The linear α-olefin is prepared by any one of the above preparation methods.

[0018] By using the technical scheme of the present invention, Fischer-Tropsch wax mainly containing straight-chain saturated high-carbon alkanes is used as a raw material, and a catalytic cracking reaction is carried out under the action of a catalyst to obtain a linear α-olefin (LAO) product with high selectivity and narrow distribution. The carbon number range of the LAO product is mainly concentrated in C7~C 15The linear α-olefins prepared by the above method not only have a concentrated carbon number distribution, high selectivity, and are easy to separate, but also have single-carbon LAO, which enriches downstream products, enhances product performance, and solves the problems of high reaction temperature and wide product carbon number range in the traditional paraffin thermal cracking process for LAO. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 The figure shows the XRD test result of Si-1 molecular sieve prepared according to the preparation example of the present invention. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] As analyzed in the background technology of this application, the prior art has the problem of wide carbon number distribution and poor quality of linear α-olefins. In order to solve this problem, this application provides a linear α-olefin and a preparation method thereof.

[0023] According to a typical embodiment of the present application, a method for preparing linear α-olefins is provided, and the preparation method comprises the following steps: step S1, using Fischer-Tropsch wax as raw materials, gasifying the Fischer-Tropsch wax and water, and then subjecting the Fischer-Tropsch wax to a catalytic cracking reaction under the action of a catalyst to obtain a cracking product; step S2, separating and purifying the cracking product to obtain a linear α-olefin; wherein the catalyst is a molecular sieve loaded with an active metal.

[0024] The present invention uses Fischer-Tropsch wax mainly containing straight-chain saturated high-carbon alkanes as raw material, and undergoes catalytic cracking reaction under the action of a catalyst to obtain linear α-olefin (LAO) products with high selectivity and narrow distribution. The carbon number range of the LAO products is mainly concentrated in the range of C7 to C 15 The linear α-olefins prepared by the above method not only have a concentrated carbon number distribution, high selectivity, and are easy to separate, but also have single-carbon LAO, which enriches downstream products, enhances product performance, and solves the problems of high reaction temperature and wide product carbon number range in the traditional paraffin thermal cracking process for LAO.

[0025] The Fischer-Tropsch wax as a raw material is a straight-chain, saturated high-carbon alkane produced by a synthesis reaction using synthesis gas under the action of a catalyst using the Fischer-Tropsch synthesis process. In some embodiments of the present application, the Fischer-Tropsch wax includes liquid wax or solid wax obtained from the refining process to the bottom oil reduction stage, that is, a wax with a carbon number distribution of C7 to C 40+ , wherein the saturated alkane content is more than 90wt%. The above-mentioned Fischer-Tropsch wax is used to prepare linear α-olefins through the preparation method of the present application, which has better quality and realizes the high-value application of the above-mentioned Fischer-Tropsch wax.

[0026] The active metal loaded in the above catalyst can be selected from the prior art. In some typical embodiments of the present application, the active metal in the catalyst includes any one or more of Pt, Fe, Cr, and Zn, which can further improve the selectivity of catalytic cracking and make the carbon number distribution of linear α-olefins more concentrated. In some embodiments, the active metal in the catalyst is selected from any one or two of Pt and Fe, and the linear α-olefins obtained by catalytic cracking are of better quality.

[0027] The above molecular sieves can be selected from the prior art. In some embodiments of the present application, the molecular sieves are selected from any one or more of MFI microporous molecular sieves, FAU microporous molecular sieves, MCM mesoporous molecular sieves and SBA mesoporous molecular sieves. These molecular sieves have a large specific surface area, and their special pore size is more favorable for catalytic reactions, especially with the above-mentioned active metals, such as Pt and Fe. After combining, they can play a synergistic role, the catalytic effect is better, and the long-chain straight-chain alkanes are cracked and converted into short-chain LAOs with better selectivity. Preferably, the molecular sieves include any one or more of ZSM-5, Si-1, Y, MCM-41, and SBA-15.

[0028] In some preferred embodiments, the Si-1 molecular sieve is prepared by the following steps: coarse pore silica gel is mixed with TPAOH, ammonia water and ethanol, the raw material mass ratio is controlled to be 1:1-0.3:0.5-0.2:1.5-0.5, and then crystallized at 170-200°C for 6-24 hours, and then dried and calcined at 500-550°C in a muffle furnace for 4-6 hours to obtain the Si-1 molecular sieve. After the Si-1 molecular sieve prepared by the above preparation method is loaded with active metals, the effect of catalytic cracking to prepare linear α-olefins is more significantly improved.

[0029] In some preferred embodiments of the present application, the content of active metal in the catalyst is 0.1-2.0wt%, which can further improve the catalytic effect of the catalyst. In some preferred embodiments, the content of platinum in the catalyst is 0.50-1.0% and the content of iron is 1.0-2.0% relative to the mass of the molecular sieve carrier.

[0030] In some embodiments of the present application, the above catalyst is prepared according to the following steps: Step S01, the molecular sieve is dried and vacuumed to obtain a pretreated loaded molecular sieve; preferably, the drying temperature is 80-150°C and the time is 2-8 hours; preferably, the vacuum degree of vacuuming is 1-200Pa and the time is 3-5 hours; before impregnation, the carrier is first in a vacuum state, and most of the air and moisture in the pores of the molecular sieve carrier are removed. The impregnation liquid diffuses rapidly after contacting the carrier, which is conducive to the uniform distribution of the metal components. Step S02, the active metal salt is added to water to prepare a complex impregnation liquid, mixed with the loaded molecular sieve, and dried to obtain a catalyst. Preferably, in step S02, under ultrasonic conditions, the complex impregnation liquid is mixed with the loaded molecular sieve, and the ultrasonic-vacuum-standing steps are repeatedly performed, and the impregnation effect is better. Preferably, each link of ultrasonic, vacuuming, and standing is performed for no less than 1 hour, and preferably, the vacuum degree of the vacuum step is 1-200Pa.

[0031] In some embodiments of the present application, in the above step S1, the temperature of catalytic cracking is 450-600°C, such as 450°C, 470°C, 490°C, 510°C, 530°C, 550°C, 570°C, 580°C, 600°C, and a better conversion rate can be obtained at the above lower temperature; in some embodiments, the pressure of catalytic cracking is 0-0.8MPa; preferably, the catalytic cracking reaction time is 2-8 seconds, and the reaction selectivity is higher.

[0032] In some embodiments of the present application, step S1 includes the following steps: step S11, liquefying the Fischer-Tropsch wax raw material, gasifying the liquefied Fischer-Tropsch wax and water to obtain gaseous Fischer-Tropsch wax and water; step S12, passing the gaseous Fischer-Tropsch wax and water into a reactor equipped with a catalyst to perform a catalytic cracking reaction to obtain a catalytic cracking product; preferably, in step S12, the weight ratio of the gaseous Fischer-Tropsch wax to water is 4 to 8:1. In some embodiments, the above-mentioned reactor is a fixed bed reactor, and a continuous reaction is performed, the contact area between the catalyst and the material is large, the catalytic efficiency is higher, and the safety is good.

[0033] The above-mentioned cracking products can be separated and purified by methods in the prior art, which are not limited in this application. In some embodiments of the present application, the above-mentioned step S2 includes the following steps: step S21, quenching the cracking products and passing them into a separation device to separate linear α-olefins and unreacted raw materials; step S22, returning the unreacted raw materials to the reactor for reaction. Through the above steps, the unreacted raw materials in the cracking products are fully recovered and reacted again, which improves the utilization rate of the raw materials and further reduces the production cost.

[0034] According to another typical embodiment of the present application, a linear α-olefin is provided, and the linear α-olefin is prepared by any one of the above preparation methods.

[0035] The above linear α-olefins are obtained by catalytic cracking reaction of Fischer-Tropsch wax containing mainly straight-chain saturated high-carbon alkanes as raw materials under the action of catalysts. The carbon number range is mainly concentrated in C7~C 12 The content reaches more than 85%, and the quality has been significantly improved.

[0036] The beneficial effects that can be achieved by the present application will be further illustrated below in combination with embodiments and comparative examples.

[0037] Catalyst preparation

[0038] Preparation Example 1

[0039] Preparation of Pt-Fe / ZSM-5 supported catalyst

[0040] The ZSM-5 molecular sieve was first dried in an oven at 120°C for 8 hours, and then placed in a closed environment and vacuumed for 2 hours. According to the required load and the weight of the carrier, the required mass of Pt and Fe was calculated, and an appropriate amount of deionized water was added to the Pt source dinitrosodiammonium platinum and the Fe source ferric nitrate to prepare the complex impregnation solution. After the impregnation solution and the carrier were fully mixed under ultrasonic conditions, the ultrasonic-vacuum-standing steps were repeated three times, wherein the vacuum degree during vacuuming was 100Pa, and finally the catalyst was prepared by drying. The obtained catalyst composition is: 0.54% platinum, 1.2% iron (relative to the carrier mass).

[0041] Preparation Example 2

[0042] Preparation of Pt-Fe / Si-1 supported catalyst

[0043] The difference from Preparation Example 1 is that the ZSM-5 molecular sieve is replaced by Si-1 molecular sieve, and the catalyst composition obtained is: 0.5% platinum and 1.0% iron (relative to the carrier mass). The preparation method of Si-1 molecular sieve is as follows:

[0044] Take a certain amount of coarse-pore silica gel, add TPAOH, ammonia water and ethanol in turn, control the raw material mass ratio to be 3:2:1:3, mix evenly, crystallize at 180°C for 12 hours, dry and place in a muffle furnace for calcination at 550°C for 6 hours to obtain Si-1 molecular sieve. The prepared Si-1 molecular sieve is subjected to XRD diffraction test, and its X-ray diffraction results are as follows: Figure 1 As shown in the figure, it can be seen that its XRD has a typical MFI topological structure diffraction peak, a flat baseline, clear and obvious diffraction peaks, and no impure crystal diffraction peaks, indicating that the obtained Si-1 molecular sieve has good purity and crystallinity.

[0045] Preparation Example 3

[0046] Preparation of Pt-Fe / Y supported catalyst

[0047] The difference from Preparation Example 1 is that the ZSM-5 molecular sieve is replaced by the Y-type molecular sieve.

[0048] Preparation Example 4

[0049] Preparation of Pt-Fe / MCM-41 supported catalyst

[0050] The difference from Preparation Example 1 is that the ZSM-5 molecular sieve is replaced by the MCM-41 molecular sieve.

[0051] Preparation Example 5

[0052] Preparation of Pt-Fe / SBA-15 supported catalyst

[0053] The difference from Preparation Example 1 is that the ZSM-5 molecular sieve is replaced by the SBA-15 molecular sieve.

[0054] Preparation Example 6

[0055] Preparation of Cr-Fe / Si-1 supported catalyst

[0056] The difference from Preparation Example 2 is that Pt is replaced by Cr in the same content, and the Cr source used is basic chromium acetate.

[0057] Preparation Example 7

[0058] Preparation of Cr-Zn / Si-1 supported catalyst

[0059] The difference from Preparation Example 6 is that Fe is replaced by the same content of Zn. The Zn source used is zinc nitrate hexahydrate.

[0060] Preparation Example 8

[0061] Preparation of Fe / Si-1 supported catalyst

[0062] The difference from Preparation Example 2 is that the catalyst does not contain Pt, and the iron content used is 1.5% (relative to the carrier mass).

[0063] Examples 1 to 12

[0064] 15 mL of catalyst was loaded into a tubular reactor (inner diameter 10 mm, height 60 mm). The types of catalysts and Fischer-Tropsch wax raw materials in each example are shown in Table 1 below. Among them, the carbon number distribution of the first-line refined wax is C7-C 17 , the normal alkane content is 95.6wt%, and the carbon number distribution of the three-line refined wax is C 13 ~C 35, the normal alkane content reaches 95.1wt%. After the raw material Fischer-Tropsch wax is liquefied, it is gasified together with an appropriate amount of water (the water-to-wax weight ratio is 0.15) and then flows through the catalyst bed to produce a catalytic cracking reaction. The pressure and temperature conditions of the reaction are shown in Table 1. The residence time in the reactor is 5 seconds to obtain a cracking product.

[0065] The generated cracking products are rapidly cooled at the reactor outlet and then enter the gas-liquid separation equipment to separate the gas, liquid olefin products and unreacted raw materials. The cracked cracking products are transported to the tail condenser by pipeline for cooling to achieve gas-liquid separation. The insulation temperature of the pipeline and tee at the inlet of the condenser is set at 80°C to prevent secondary reactions and gas-liquid miscibility. After condensation, the liquid hydrocarbons are collected by the bottom liquid phase product collector, and the gas phase products are collected by the top gas phase product collector. The unreacted raw materials are circulated back to the top of the reactor to feed and react again.

[0066] The separated liquid olefin product is qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography.

[0067] Comparative Example 1

[0068] The difference from Example 3 is that no catalyst is loaded in the reactor, and the reaction conditions are shown in Table 1 below.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that no catalyst is loaded in the reactor, and the reaction conditions are shown in Table 1 below.

[0071] Table 1

[0072]

[0073] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the above linear α-olefins are prepared by catalytic cracking reaction of Fischer-Tropsch wax mainly containing straight-chain saturated high-carbon alkanes as raw materials under the action of catalysts, and not only the LAO yield can reach about 50%, but also the carbon number range is mainly concentrated in C7~C 12 , the content is high and the quality has been significantly improved.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing linear α-olefins, characterized in that: The following steps are involved: Step S1, using Fischer-Tropsch wax as a raw material, gasifying the Fischer-Tropsch wax and water, and then subjecting the Fischer-Tropsch wax to a catalytic cracking reaction under the action of a catalyst to obtain a cracking product; Step S2, separating and purifying the cracking product to obtain linear α-olefins; The catalyst is a molecular sieve loaded with active metals, wherein the active metals are any one or a combination of Pt, Fe, Cr, and Zn, and the molecular sieves are any one or more of ZSM-5, Si-1, Y, and SBA-15; the content of active metals in the catalyst is 0.1 to 2.0% of the weight of the carrier.

2. The preparation method according to claim 1, characterized in that: The Fischer-Tropsch wax includes liquid wax or solid wax obtained from the refining process from the conventional line to the bottom oil reduction section.

3. The preparation method according to claim 1, characterized in that: The active metals are Pt and Fe.

4. The preparation method according to claim 1, characterized in that: The content of platinum in the catalyst is 0.50-1.0%, and the content of iron is 1.0-2.0%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The catalyst is obtained by the following preparation method, which comprises: Step S01, drying the molecular sieve and evacuating the vacuum to obtain a pretreated supported molecular sieve; Step S02, adding active metal salt into water to prepare a complex impregnation solution, mixing it with the supported molecular sieve, and drying to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that: In the step S01, the drying temperature is 80-150° C. and the drying time is 2-8 hours.

7. The preparation method according to claim 5, characterized in that: The vacuum degree of the vacuum pumping is 1-200 Pa, and the time is 3-5 hours.

8. The preparation method according to claim 5, characterized in that: In the step S02, the complex impregnation solution is mixed with the supported molecular sieve under ultrasonic conditions, and the mixed solution is subjected to the ultrasonic-vacuum-standing step for more than 2 times.

9. The preparation method according to claim 8, characterized in that: The ultrasonication, vacuuming and standing are each performed for no less than 1 hour, and the vacuum degree of the vacuuming step is 1-200 Pa.

10. The preparation method according to claim 1, characterized in that: The temperature of the catalytic cracking is 450-600°C.

11. The preparation method according to claim 10, characterized in that: The pressure of the catalytic cracking is 0-0.8 MPa.

12. The preparation method according to claim 10, characterized in that: The catalytic cracking reaction time is 2 to 8 seconds.

13. The preparation method according to claim 1, characterized in that: The step S1 comprises the following steps: Step S11, liquefying the Fischer-Tropsch wax raw material, and gasifying the liquefied Fischer-Tropsch wax and water to obtain gaseous Fischer-Tropsch wax and water; Step S12, introducing the gaseous Fischer-Tropsch wax and water into a reactor containing a catalyst to carry out a catalytic cracking reaction to obtain a catalytic cracking product.

14. The preparation method according to claim 13, characterized in that: In the step S12, the weight ratio of the gaseous Fischer-Tropsch wax to water is 4-8:

1.

15. The preparation method according to claim 13, characterized in that: The reactor is a fixed bed reactor.

16. The preparation method according to claim 1, characterized in that: The step S2 comprises the following steps: Step S21, quenching the pyrolysis product and passing it into a separation device to separate the linear α-olefin and unreacted raw materials; Step S22, returning the unreacted raw materials to the reactor for reaction.

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