A process for preparing high carbon internal olefins from a feed of fischer-tropsch oil

Abstract

The application discloses a process for preparing high-carbon internal olefins from Fischer-Tropsch oil, which comprises the following steps: a, Fischer-Tropsch oil enters a first vacuum tower for vacuum rectification, a fraction with carbon number greater than or equal to 16 enters a second vacuum tower for vacuum rectification, and enters an extraction tower for extraction; b, a first mixture containing the fraction with carbon number of 16-18, an extractant and an oxygen-containing compound enters a first rectification tower for rectification; c, a second mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compound enters an adsorption tower for adsorption; d, a third mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compound is output from the top of the adsorption tower and enters an isomerization reactor for reaction to obtain a target product. The process for preparing high-carbon internal olefins from Fischer-Tropsch oil provided by the application effectively avoids the loss of alpha-olefins in Fischer-Tropsch oil, has the advantages of low energy consumption, low cost and good economy, and the content of the oxygen-containing compound in the target product is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a process for preparing high-carbon internal olefins from Fischer-Tropsch oil. BACKGROUND

[0002] Fischer-Tropsch synthesis oil is a mixture of hydrocarbons generated by synthesis gas under the action of a catalyst, widely used in the field of petroleum chemical industry to replace traditional petroleum resources. However, due to the possible introduction of oxygen-containing compounds such as alcohols, aldehydes, ketones and esters during the Fischer-Tropsch synthesis reaction process, the presence of these oxygen-containing compounds will reduce the stability and combustion performance of the final product, and affect its quality as a fuel or chemical raw material.

[0003] In order to improve the quality of Fischer-Tropsch synthesis oil and meet the needs of different uses, especially as high-quality fuel or fine chemical raw material, an effective deoxygenation refining process must be carried out. However, the existing deoxygenation refining process has problems such as high energy consumption, high cost and low deoxygenation rate. SUMMARY

[0004] The present application provides a process for preparing high-carbon internal olefins from Fischer-Tropsch oil.

[0005] The present application provides a process for preparing high-carbon internal olefins from Fischer-Tropsch oil, comprising the following steps:

[0006] Step a: Fischer-Tropsch oil enters the first vacuum tower for vacuum rectification, and the fraction with carbon number greater than or equal to 16 is output from the bottom of the first vacuum tower and enters the second vacuum tower for vacuum rectification, and the fraction with carbon number of 16-18 is output from the top of the second vacuum tower and enters the extraction tower for extraction;

[0007] Step b: After the extraction treatment in step a, the first mixture containing the fraction with carbon number of 16-18, the extractant and the oxygen-containing compounds is output from the top of the extraction tower and enters the first rectification tower for rectification;

[0008] Step c: After the rectification treatment in step b, the second mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compounds is output from the bottom of the first rectification tower and enters the adsorption tower for adsorption, wherein the concentration of the oxygen-containing compounds in the second mixture is less than or equal to 500 ppm;

[0009] Step d: After the adsorption treatment in step c, the third mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compounds is output from the top of the adsorption tower and enters the isomerization reactor for reaction to obtain the target product, wherein the concentration of the oxygen-containing compounds in the third mixture is less than or equal to 10 ppm.

[0010] In one embodiment of the present application, the fraction with carbon number less than 16 is outputted from the top of the first reduced pressure first distillation column after being treated by the first reduced pressure distillation column;

[0011] The fourth mixture containing the fraction with carbon number greater than 18 and oxygen-containing compounds is outputted from the bottom of the second reduced pressure column after being treated by the second reduced pressure distillation column.

[0012] In one embodiment of the present application, the fraction with carbon number of 16-18 is outputted from the top of the second reduced pressure column and enters the extraction column for extraction, which includes:

[0013] The extractant enters the extraction column from the middle upper part of the extraction column and moves to the bottom of the extraction column, the fraction with carbon number of 16-18 is outputted from the top of the second reduced pressure column, the fraction with carbon number of 16-18 enters the extraction column from the middle lower part of the extraction column and moves to the top of the extraction column and is mixed with the extractant for extraction.

[0014] In one embodiment of the present application, the extractant is aqueous methanol or aqueous ethanol, and the water content of the extractant is 0-25%wt.

[0015] In one embodiment of the present application, the step c further includes:

[0016] The fifth mixture containing the extractant is outputted from the top of the first distillation column and is configured to be recycled into the extraction column.

[0017] In one embodiment of the present application, the Fischer-Tropsch oil contains a fraction with carbon number of 4-30.

[0018] In one embodiment of the present application, the content of oxygen-containing compounds in the Fischer-Tropsch oil is 0-5%.

[0019] In one embodiment of the present application, the adsorption column includes a first adsorption column and a second adsorption column which are sequentially communicated, a drying agent is arranged in the first adsorption column, and the second mixture is configured to be dried by the first adsorption column; an adsorbent is arranged in the second adsorption column, and the dried second mixture is configured to be deoxidized by the second adsorption column.

[0020] In one embodiment of the present application, the drying agent is one or more of 3A, 5AH, and silica gel, and the adsorbent is one or more of activated alumina, 13X, and white clay.

[0021] In one embodiment of the present application, the third mixture contains C16-C18 alpha-olefins and alkanes, and the third mixture is configured to be reacted in an isomerization reactor to generate C16-C18 internal olefins.

[0022] The process for preparing high-carbon internal olefins from Fischer-Tropsch oil as raw material effectively avoids the loss of alpha-olefins in Fischer-Tropsch oil, has the advantages of low energy consumption, low cost and good economy, and the content of oxygen-containing compounds in the target product is low.

[0023] Other features of the present application, and its advantages, will become apparent in the description of the exemplary embodiments of the present application that follows. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0025] Figure 1 is a process flow diagram for preparing high-carbon internal olefins from Fischer-Tropsch oil as raw material provided by an embodiment of the present disclosure;

[0026] Figure 2 is a process structure diagram for preparing high-carbon internal olefins from Fischer-Tropsch oil as raw material provided by an embodiment of the present disclosure.

[0027] 1-First vacuum column; 2-Second vacuum column; 3-Extraction column; 4-First rectification column; 5-Adsorption column; 51-First adsorption column; 52-Second adsorption column; 6-Isomerization reactor; 7-Heater; 8-Flash tank; 9-Second rectification column. DETAILED DESCRIPTION

[0028] In order to make the purposes, technical solutions and beneficial technical effects of the present application clearer, the present application will be described in detail below in combination with specific embodiments. It should be understood that the embodiments described in the specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0029] For the sake of simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range that is not explicitly recited; and any lower limit can be combined with other lower limits to form a range that is not explicitly recited, as can any upper limit be combined with any other upper limit to form a range that is not explicitly recited. Furthermore, although not explicitly recited, every point or individual number within a range is included in the range. Thus, every point or individual number can serve as its own lower limit or upper limit to combine with any other point or individual number or to combine with other lower limits or upper limits to form a range that is not explicitly recited.

[0030] In the description herein, it should be noted that, unless otherwise specified, "above", "below" include the number itself, and "several" means two or more.

[0031] The above summary of the application is not intended to describe each disclosed embodiment or implementation in the application. The following description more specifically illustrates example embodiments. Throughout this application, guidance is provided by a series of examples, which can be used in various combinations. In each instance, the recited combination is presented only as a representative group and should not be construed as exhaustive.

[0032] The present disclosure provides a process for preparing high carbon internal olefins from Fischer-Tropsch oil, comprising the following steps: step a: the Fischer-Tropsch oil enters a first vacuum tower for vacuum rectification, a fraction with carbon number greater than or equal to 16 is output from the bottom of the first vacuum tower and enters a second vacuum tower 2 for vacuum rectification, a fraction with carbon number of 16-18 is output from the top of the second vacuum tower 2 and enters an extraction tower 3 for extraction; step b: after the extraction treatment in step a, a first mixture containing the fraction with carbon number of 16-18, an extractant and an oxygen-containing compound is output from the top of the extraction tower 3 and enters a first rectification tower 4 for rectification; step c: after the rectification treatment in step b, a second mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compound is output from the bottom of the first rectification tower 4 and enters an adsorption tower 5 for adsorption, wherein the concentration of the oxygen-containing compound in the second mixture is less than or equal to 500 ppm; step d: after the adsorption treatment in step c, a third mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compound is output from the top of the adsorption tower 5 and enters an isomerization reactor 6 for reaction to obtain a target product, wherein the concentration of the oxygen-containing compound in the third mixture is less than or equal to 10 ppm.

[0033] The process for preparing high carbon internal olefins from Fischer-Tropsch oil provided by the present disclosure effectively avoids the loss of α-olefins in Fischer-Tropsch oil, has the advantages of low energy consumption, low cost and good economy, and the content of oxygen-containing compounds in the target product is low.

[0034] The specific embodiments of the present disclosure are described below in conjunction with the accompanying drawings.

[0035] As shown in Figures 1 to 2 The present disclosure provides a process for preparing high carbon internal olefins from Fischer-Tropsch oil, comprising the following steps:

[0036] Step a: the Fischer-Tropsch oil enters a first vacuum tower 1 for vacuum rectification, a fraction with carbon number greater than or equal to 16 is output from the bottom of the first vacuum tower 1 and enters a second vacuum tower 2 for vacuum rectification, a fraction with carbon number of 16-18 is output from the top of the second vacuum tower 2 and enters an extraction tower 3 for extraction.

[0037] Specifically, the Fischer-Tropsch oil is first sent into the first vacuum tower 1 for vacuum rectification, and the fraction with carbon number greater than or equal to 16 is separated to the bottom of the first vacuum tower 1 due to its high boiling point. This fraction then continues to enter the second vacuum tower 2 for further vacuum rectification. In the second vacuum tower 2, the fraction with carbon number between 16 and 18 is mainly rectified, and due to its relatively low boiling point under specific pressure and temperature conditions, it is output from the top of the second vacuum tower 2. Finally, the obtained fraction with carbon number 16-18 is sent into the extraction tower 3 for extraction treatment.

[0038] In one embodiment of the present disclosure, the Fischer-Tropsch oil contains a fraction with carbon number 4-30.

[0039] In one embodiment of the present disclosure, the content of oxygen-containing compounds in the Fischer-Tropsch oil is 0-5%.

[0040] Specifically, in the present embodiment, the content of oxygen-containing compounds in the Fischer-Tropsch oil is 0-5%, mainly including organic acids, alcohols, ketones, aldehydes, esters and alkyl acids, etc.

[0041] In one embodiment of the present disclosure, after the vacuum rectification treatment by the first vacuum tower 1, the fraction with carbon number less than 16 is output from the top of the first vacuum tower 1; after the vacuum rectification treatment by the second vacuum tower 2, the fourth mixture containing the fraction with carbon number greater than 18 and oxygen-containing compounds is output from the bottom of the second vacuum tower 2.

[0042] Specifically, after the vacuum rectification treatment by the first vacuum tower 1, the fraction with carbon number less than 16 is output from the top of the first vacuum tower 1, and the fraction with carbon number greater than or equal to 16 and oxygen-containing compounds are output from the bottom of the first vacuum tower 1 and enter the second vacuum tower 2 for vacuum rectification treatment. In the second vacuum tower 2, the fraction with carbon number greater than or equal to 19 and oxygen-containing compounds are output from the bottom of the second vacuum tower 2, and the fraction with carbon number ranging from 16 to 18 and part of the oxygen-containing compounds are output from the top of the second vacuum tower 2.

[0043] In one embodiment of the present disclosure, the fraction with carbon number 16-18 is output from the top of the second vacuum tower 2 and enters the extraction tower 3 for extraction, which includes that the extractant enters the extraction tower 3 from the upper middle part of the extraction tower 3 and moves to the bottom of the extraction tower 3, the fraction with carbon number 16-18 is output from the top of the second vacuum tower 2, and the fraction with carbon number 16-18 enters the extraction tower 3 from the lower middle part of the extraction tower 3 and moves to the top of the extraction tower 3 and mixes with the extractant for extraction.

[0044] Specifically, the extractant enters the extraction column 3 from the middle upper part of the extraction column 3 and moves to the bottom of the extraction column 3, thus allowing the extractant to contact the carbon number 16-18 fraction countercurrently, which can improve the extraction efficiency. Due to its good solubility, the extractant can gradually enrich the target compound during the downward flow, forming azeotrope or partial mutual solubility, thereby achieving effective separation of the target fraction. The carbon number 16-18 fraction is fed from the middle lower part of the extraction column 3. Since the density of the extractant is greater than that of the carbon number 16-18 fraction, the carbon number 16-18 fraction will meet the extractant from above and undergo sufficient contact and dissolution reaction during the upward flow of the carbon number 16-18 fraction in the extraction column 3. Based on the solubility of the extractant to the fraction, the carbon number 16-18 fraction can be effectively extracted.

[0045] In one embodiment of the present disclosure, the extractant is aqueous methanol or aqueous ethanol, and the water content of the extractant is 0-25%wt.

[0046] Specifically, in the rectification and extraction process of Fischer-Tropsch oil, the selection of the extractant is crucial to the separation effect. In this embodiment, the extractant used is aqueous methanol or aqueous ethanol, both of which are common organic solvents with good solubility and selectivity, and can effectively dissolve and separate hydrocarbon compounds in a specific carbon number range.

[0047] The aqueous methanol or aqueous ethanol in this embodiment can have a water content of 0%-25%wt when used as an extractant. By adjusting the water-alcohol ratio, the extraction effect can be optimized to some extent, achieving efficient separation of fractions in a specific carbon number range.

[0048] Step b: After the extraction treatment in step a, the first mixture containing the carbon number 16-18 fraction, the extractant and the oxygen-containing compound is output from the top of the extraction column 3 and enters the first rectification column 4 for rectification.

[0049] Specifically, after the extraction treatment stage in step a, a first mixture containing the carbon number 16-18 fraction is obtained. The first mixture mainly includes the carbon number 16-18 fraction, the extractant and the oxygen-containing compound. The first mixture is then sent to the first rectification column 4 for rectification. The mixed oil containing the extractant and the oxygen-containing compound is output from the bottom of the extraction column 3 and heated by the heater 7 before entering the flash tank 8 for flash treatment. After the flash treatment, the mixed oil containing the extractant and the oxygen-containing compound is output from the bottom of the flash tank 8 and enters the second rectification column 9 for rectification. The mixed gas containing the extractant in the flash tank 8 and the second rectification column 9 is output from the top of the flash tank 8 and the second rectification column 9, respectively, and enters the extraction column 3 for recycling.

[0050] Step c: After the rectification treatment in step b, a second mixture containing the fraction with carbon number of 16-18 and oxygen-containing compounds is output from the bottom of the first rectification column 4 and enters the adsorption column 5 for adsorption, wherein the concentration of the oxygen-containing compounds in the second mixture is less than or equal to 500 ppm.

[0051] Specifically, after the rectification treatment in step b, the second mixture mainly containing the fraction with carbon number of 16-18 and a small amount of residual oxygen-containing compounds is output from the bottom of the first rectification column 4. The concentration of the oxygen-containing compounds in the second mixture after rectification is reduced, and the concentration is less than or equal to 500 ppm. To further improve the product quality and remove the residual trace amount of oxygen-containing compounds, the second mixture is then sent to the adsorption column 5 for adsorption treatment.

[0052] In an embodiment of the present disclosure, the adsorption column 5 includes a first adsorption column 51 and a second adsorption column 52 connected in sequence, the first adsorption column 51 is provided with a drying agent, and the second mixture is configured to be dried in the first adsorption column 51; the second adsorption column 52 is provided with an adsorbent, and the dried second mixture is configured to be deoxidized and adsorbed in the second adsorption column 52.

[0053] Specifically, the adsorption column 5 in the present embodiment includes a first adsorption column 51 and a second adsorption column 52 connected in sequence, the first adsorption column 51 is provided with a drying agent, mainly used for adsorbing the moisture in the second mixture. After the drying treatment in the first adsorption column 51, the second mixture enters the second adsorption column 52 for adsorption treatment, and the second adsorption column 52 is provided with an adsorbent, mainly used for adsorbing the oxygen-containing compounds, i.e. deoxidizing and adsorbing the second mixture. After the deoxidizing and adsorbing treatment in the first adsorption column 51 and the second adsorption column 52, the oxygen-containing compounds in the second mixture are further removed, ensuring the purity of the target product and improving the quality of the target product.

[0054] In an embodiment of the present disclosure, the drying agent is one or more of 3A, 5AH, and silica gel, and the adsorbent is one or more of activated alumina, 13X, and white clay.

[0055] In an embodiment of the present disclosure, step c further includes: a fifth mixture containing an extractant is output from the top of the first rectification column 4 and is configured to be recycled to the extraction column 3.

[0056] Specifically, in order to improve the economic and environmental performance of the whole process, in the present embodiment, the fifth mixture containing the extractant is output from the top of the first rectification column 4 and then enters the extraction column 3 for reuse.

[0057] Step d: After the adsorption treatment in step c, the third mixture containing the fraction with carbon number of 16-18 and oxygenates is output from the top of the adsorption tower 5 to the isomerization reactor 6 for reaction to obtain the target product, wherein the concentration of oxygenates in the third mixture is less than or equal to 10 ppm.

[0058] Specifically, after the adsorption treatment in step c, the third mixture output from the top of the adsorption tower 5 mainly contains the fraction with carbon number of 16-18, and the concentration of oxygenates is further greatly reduced to a level of less than or equal to 10 ppm. The removal rate of oxygenates in the third mixture after the adsorption treatment is high, which ensures the high quality and purity of the final target product. Then, the fraction with carbon number of 16-18 is sent to the isomerization reactor 6 for reaction to obtain the target product.

[0059] In one embodiment of the present disclosure, the third mixture contains C16-C18 alpha-olefins and alkanes, and the third mixture is configured to generate C16-C18 internal olefins in the isomerization reactor 6.

[0060] The process for preparing high-carbon internal olefins from Fischer-Tropsch oil provided by the present application effectively avoids the loss of alpha-olefins in Fischer-Tropsch oil, has the advantages of low energy consumption, low cost and good economy, and the content of oxygenates in the target product is low.

[0061] Test Example 1

[0062] Fischer-Tropsch oil with carbon number of C4-C30 is subjected to vacuum rectification in the first vacuum tower 1, the overhead product is ≤C15, and the bottom product C16-C30 is subjected to vacuum rectification in the second vacuum tower 2, the overhead product is C16-C18 (containing odd carbon), and the bottom product is C19-C30.

[0063] The C16-C18 Fischer-Tropsch oil is mixed with water-containing methanol in the extraction tower 3, extracted, and subjected to rough removal of oxygenates.

[0064] The extraction phase is heated to superheat by the heater 7, then enters the flash tank 8, part of the methanol from the top of the flash tank 8 is recycled back to the extraction tower 3, and the remaining material enters the second rectification tower 9 for rectification, part of the methanol from the top of the second rectification tower 9 is recycled back to the extraction tower 3, and the bottom product is oxygenates and a small amount of vented methanol.

[0065] The raffinate phase enters the first rectification tower 4, methanol from the top of the first rectification tower 4 is recycled back to the extraction tower 3, and the bottom product enters the first adsorption tower 51 for adsorption drying and dehydration; after dehydration, the material continues to enter the second adsorption tower 52 for fine removal of oxygenates, and the material after fine removal enters the isomerization reactor 6 to generate a mixed product of high-carbon internal olefins and alkanes.

[0066] (1) The operating conditions of each device are as follows:

[0067]

[0068]

[0069] (2) The Fischer-Tropsch oil feedstock composition is as follows:

[0070]

[0071] (3) The olefin to alkane mass ratio is 3:1

[0072] (4) The methanol water content is 1% wt

[0073] (5) The product composition is as follows:

[0074] First rectifier overhead light component oil

[0075] No. Composition Content %wt 1 ≤C15 97 2 C16-C18 3

[0076] Second rectifier bottom heavy component oil

[0077] Oxygenates and purge methanol

[0078] No. Composition Content %wt 1 Water 7 2 Methanol 3 3 Oxygenates 90

[0079] Internal olefins and alkane mixed product (carbonyls < 10 ppm)

[0080] No. Composition Content %wt 1 C16-C18 alkanes 26 2 C16-C18 alpha olefins 2.25 3 C16-C18 internal olefins 71.75

[0081] Test Example 2

[0082] The Fischer-Tropsch oil having a carbon number of C4-C30 is fed to a first vacuum column 1 for vacuum rectification, the overhead product is < C15, and the column bottom C16-C30 is fed to a second vacuum column 2 for vacuum rectification, the column bottom product is C19-C30, and the overhead product is C16-C18 (including odd carbon numbers).

[0083] The C16-C18 Fischer-Tropsch oil is fed to an extraction column 3, mixed with water-containing methanol, extracted, and subjected to rough oxygenate removal.

[0084] The extraction phase is heated to superheat by a heater 7, then fed to a flash tank 8, and part of the methanol is returned to the extraction column 3 from the top of the flash tank 8, and the remaining material is fed to a second rectifier 9 for rectification, part of the methanol is returned to the extraction column 3 from the overhead, and the column bottom is oxygenates and a small amount of purge methanol.

[0085] The raffinate phase enters the first rectification column 4, from which the overhead methanol is recycled to the extraction column 3, and the column bottoms enter the first adsorption column 51 for adsorption drying and dehydration; the dehydrated material continues to enter the second adsorption column 52 for fine removal of oxygen-containing compounds, and the fine-removed material enters the isomerization reactor 6 to produce a mixed product of high-carbon internal olefins and alkanes.

[0086] (1) The operating conditions of each device are as follows:

[0087]

[0088]

[0089] (2) The composition of the Fischer-Tropsch oil feedstock is as follows:

[0090]

[0091] (3) The olefin / alkane mass ratio is 3:1

[0092] (4) The methanol water content is 5% wt

[0093] (5) The product composition is as follows:

[0094] First rectification column overhead light component oil

[0095] No. Composition Content %wt 1 ≤C15 99 2 C16-C18 1

[0096] Second rectification column bottoms heavy component oil

[0097] Oxygen-containing compounds and purge methanol

[0098] No. Composition Content %wt 1 Water 6 2 Methanol 2 3 Oxygenates 92

[0099] Internal olefin and alkane mixed product (carbonyl <10 ppm)

[0100] No. Composition Content %wt 1 C16-C18 alkanes 25 2 C16-C18 alpha olefins 1.25 3 C16-C18 internal olefins 73.75

[0101] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein. The scope of the present application is defined by the appended claims.

Claims

1. A process for the production of high carbon internal olefins from Fischer-Tropsch oil, characterized in that, The method comprises the following steps: Step a: the Fischer-Tropsch oil enters a first vacuum column (1) for vacuum rectification, and a fraction with carbon number greater than or equal to 16 is output from the bottom of the first vacuum column (1) and enters a second vacuum column (2) for vacuum rectification, and a fraction with carbon number of 16-18 is output from the top of the second vacuum column (2) and enters an extraction column (3) for extraction; Step b: after the extraction treatment in the step a, a first mixture containing the fraction with carbon number of 16-18, an extractant and an oxygen-containing compound is output from the top of the extraction column (3) and enters a first rectification column (4) for rectification; Step c: after the rectification treatment in the step b, a second mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compound is output from the bottom of the first rectification column (4) and enters an adsorption column (5) for adsorption, wherein the concentration of the oxygen-containing compound in the second mixture is less than or equal to 500 ppm; Step d: after the adsorption treatment in the step c, a third mixture containing the fraction with carbon number of 16-18 and the oxygen-containing compound is output from the top of the adsorption column (5) and enters an isomerization reactor (6) for reaction to obtain a target product, wherein the concentration of the oxygen-containing compound in the third mixture is less than or equal to 10 ppm; The adsorption column (5) comprises a first adsorption column (51) and a second adsorption column (52) which are sequentially communicated, a drying agent is arranged in the first adsorption column (51), and the second mixture is configured to be dried in the first adsorption column (51); an adsorbent is arranged in the second adsorption column (52), and the dried second mixture is configured to be deoxidized and adsorbed in the second adsorption column (52).

2. The process for preparing high carbon internal olefins from Fischer-Tropsch oil according to claim 1, characterized in that, After the vacuum rectification treatment in the first vacuum column (1), a fraction with carbon number less than 16 is output from the top of the first vacuum column (1); After the vacuum rectification treatment in the second vacuum column (2), a fourth mixture containing a fraction with carbon number greater than 18 and the oxygen-containing compound is output from the bottom of the second vacuum column (2).

3. The process for preparing high carbon internal olefins from Fischer-Tropsch oil according to claim 1, characterized in that, The output of the fraction with carbon number of 16-18 from the top of the second vacuum column (2) and into the extraction column (3) for extraction comprises: The extractant enters the extraction column (3) from the middle upper part of the extraction column (3) and moves to the bottom of the extraction column (3), the fraction with carbon number of 16-18 is output from the top of the second vacuum column (2), the fraction with carbon number of 16-18 enters the extraction column (3) from the middle lower part of the extraction column (3) and moves to the top of the extraction column (3) and is mixed with the extractant for extraction.

4. The process for preparing high carbon internal olefins from Fischer-Tropsch oil according to claim 3, characterized in that, The extractant is aqueous methanol or aqueous ethanol.

5. The process for preparing high carbon internal olefins from Fischer-Tropsch oil according to claim 1, characterized in that, The step c further comprises: A fifth mixture containing the extractant is output from the top of the first rectification column (4) and is configured to be recycled into the extraction column (3).

6. The process for making higher internal olefins from Fischer-Tropsch oil according to claim 1, wherein, The Fischer-Tropsch oil contains a fraction with carbon number of 4-30.

7. The process for making higher internal olefins from Fischer-Tropsch oil according to claim 6, characterized in that, The drying agent is one or both of 3A molecular sieve and silica gel, and the adsorbent is one or more of active alumina, 13X molecular sieve and white clay. The drying agent is one or both of 3A molecular sieve and silica gel, and the adsorbent is one or more of active alumina, 13X molecular sieve and white clay.

8. The process for making higher internal olefins from Fischer-Tropsch oil according to claim 1, wherein, The third mixture comprises C16-C18 alpha-olefins, alkanes, the third mixture being configured to react in an isomerization reactor (6) to produce C16-C18 internal olefins.

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