CN112079683A

CN112079683A - Method and apparatus for purifying 1-hexene

Info

Publication number: CN112079683A
Application number: CN202011155949.0A
Authority: CN
Inventors: 李文涛; 汪丹峰; 唐志永
Original assignee: Shanghai Ruicheng Carbon Energy Technology Co ltd
Current assignee: Shanghai Ruicheng Carbon Energy Technology Co ltd
Priority date: 2020-10-26
Filing date: 2020-10-26
Publication date: 2020-12-15

Abstract

A method of purifying 1-hexene, comprising: (i) providing a stream comprising 1-hexene; (ii) pre-cutting and fractionating; (iii) performing azeotropic distillation; (iv) carrying out reactive distillation; (v) extracting and removing the entrainer by using a first extracting agent; (vi) removing heavy components; (vii) carrying out extractive distillation by using a second extractant; (viii) the cycloolefin component is removed with a third extractant. The invention also provides an apparatus for purifying 1-hexene.

Description

Method and apparatus for purifying 1-hexene

Technical Field

This application relates generally to a process and apparatus for purifying 1-hexene, and more particularly to a process and apparatus for purifying a 1-hexene fraction from an olefin product produced from synthesis gas.

Background

1-hexene is an important comonomer for producing high density polyethylene and linear low density polyethylene, and is also an important raw material for manufacturing fine chemical products such as surfactants, synthetic lubricating oil base oils and the like. The market demand of the 1-hexene is rapidly increased, and the 1-hexene has high economic value. The current synthesis of 1-hexene is based mainly on the direct production of synthesis gas, 1-hexene being present in the light fraction. Although this preparation method is relatively low cost and has few impurities, obtaining very high purity 1-hexene from this synthesis method remains a very difficult challenge. With the wider and wider application of the 1-hexene, the yield of the 1-hexene in China can not meet the domestic requirements, and the 1-hexene above the domestic polymerization level almost completely depends on import.

Therefore, a purification method and equipment for further improving the purity of 1-hexene are urgently needed to relieve the contradiction between supply and demand and improve the added value of products.

Disclosure of Invention

The present inventors have conducted extensive and intensive studies to achieve the above-mentioned object in a low-cost and convenient manner by improving process conditions and purification equipment, thereby completing the present invention. In one aspect of the present invention, the present invention provides a method of purifying 1-hexene, the method comprising:

step (i): providing a stream comprising 1-hexene;

step (ii): (iii) subjecting said stream comprising 1-hexene to a pre-cut fractionation in which step (ii) a stream of fractions below C5 and a stream of fractions above C7 are at least partially removed to obtain a C6-enriched fraction stream, said C6-enriched fraction stream comprising C6 hydrocarbons;

step (iii): (iii) adding an entrainer selected from a C1-C4 alcohol to the C6 rich fraction stream obtained from step (ii) and performing azeotropic distillation to at least partially remove oxygenates, thereby obtaining a first mixture stream comprising said C1-C4 alcohol with a C6 hydrocarbon;

step (iv): (iv) subjecting the first mixture stream obtained in step (iii) to reactive distillation with said C1-C4 alcohol to at least partially remove tertiary carbon olefins, thereby obtaining a second mixture stream comprising C1-C4 alcohols and C6 hydrocarbons;

step (v): (iii) removing the C1-C4 alcohol from the second mixture stream obtained from step (iv) with a first extractant to obtain a refined C6 hydrocarbon stream;

step (vi): (vi) subjecting the refined C6 hydrocarbon stream obtained in step (v) to de-heaving to remove heavier hydrocarbons boiling above 1-hexene to obtain a 1-hexene rich stream, said 1-hexene rich stream comprising 1-hexene and C6 hydrocarbons boiling below 1-hexene other than 1-hexene;

step (vii): subjecting the 1-hexene rich stream to extractive rectification with a second extractant to remove C6 hydrocarbons boiling lower than 1-hexene other than 1-hexene to obtain a third mixture stream comprising the second extractant and 1-hexene;

step (viii): (viii) extracting the third mixture stream obtained from step (vii) with a third extractant to remove the cycloalkene and to obtain a product stream comprising 1-hexene.

According to an embodiment of this first aspect, the method further comprises at least one of the following steps (a) and (b):

step (a) of recovering said C1-C4 alcohol after step (v);

step (b) of recovering the first extractant and the second extractant separately after step (viii).

According to another embodiment of this first aspect, step (ii) is carried out in a pre-cut tower provided with vertical partitions therein to divide the pre-cut tower into 4 sections: one side of the baffle for feeding is a pre-fractionating area, one side of the baffle for taking out is a side-line rectifying area, a public rectifying area is arranged above the baffle, and a public stripping area is arranged below the baffle; the number of theoretical plates in the pre-distillation zone is 5-15, the number of theoretical plates in the lateral line distillation zone is 5-15, the number of theoretical plates in the public distillation zone is 5-15, and the number of theoretical plates in the public stripping zone is 5-15. According to another embodiment of the first aspect, the stream comprising 1-hexene from step (i) is fed from between the 2 nd and 15 th trays from the top of the prefractionation section, the C6 rich fraction stream is withdrawn at a point between the 2 nd and 15 th trays from the top of the sidetrack rectification section at a reflux ratio of 1 to 10, an overhead temperature of 20 to 40 ℃ and a still temperature of 100 to 150 ℃.

According to another embodiment of the first aspect, the azeotroping agent in step (iii) comprises at least one C1-C4 alcohol selected from the group consisting of: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 2-methyl-1, 3-propanediol, 3-methyl-1, 2-propanediol, 1,2, 3-propanetriol, 1,2, 3-butanetriol, 1,2, 4-butanetriol, 2-methyl-1, 2, 3-propanetriol, 1,2,3, 4-butanetetraol, or any mixture thereof. According to another embodiment of the first aspect, the step (iii) is performed in an azeotropic distillation column, the number of theoretical plates of the azeotropic distillation column is 20 to 40, the feed position of the C6-rich fraction stream is 3 to 35 from the top, the feed position of the C1-C4 alcohol is 1 to 10 from the top, the reflux ratio is 1 to 10, the overhead temperature is 40 to 60 ℃, and the bottom temperature is 50 to 100 ℃. According to another embodiment of the first aspect, the volumetric flow ratio of the C1-C4 alcohol to the C6 fraction stream is from 0.1:1 to 1.5: 1.

According to another embodiment of the first aspect, the step (iv) is performed in a reactive distillation column, the number of theoretical plates of the reactive distillation column is 20 to 40, the reflux ratio is 1 to 10, the feeding position of the first mixture material flow is 10 to 35 plates from top, the temperature of the top of the column is 40 to 70 ℃, and the temperature of the bottom of the column is 80 to 120 ℃. According to another embodiment of this first aspect, step (iv) is carried out in the presence of an etherification catalyst, which is a strongly acidic cationic resin. According to another embodiment of this first aspect, the C1-C4 alcohol used in step (iv) is selected from at least one of the following: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 2-methyl-1, 3-propanediol, 3-methyl-1, 2-propanediol, 1,2, 3-propanetriol, 1,2, 3-butanetriol, 1,2, 4-butanetriol, 2-methyl-1, 2, 3-propanetriol, 1,2,3, 4-butanetetraol, or any mixture thereof. According to another embodiment of this first aspect, step (v) is carried out in an extraction column, preferably the first extractant is water. According to another embodiment of this first aspect, step (v) is carried out in an extraction column having a theoretical plate number of 3 to 10, a water feed position being the first plate from the top of the extraction column, a fine C6 hydrocarbon stream feed position being the last plate from the top of the extraction column, a water to oil ratio of 0.4 to 4, and an operating temperature of 5 to 45 ℃. According to another embodiment of this first aspect, step (vi) is carried out in a fine heavies removal column, which is an atmospheric distillation column having a theoretical plate number of 60 to 160, a reflux ratio of 10 to 40, a feed position of a refined C6 hydrocarbon stream of 10 to 50 plates from the top, an overhead temperature of 58 to 68 ℃, and a column bottom temperature of 60 to 90 ℃. According to another embodiment of the first aspect, the step (vii) is performed in an extractive distillation light component removal tower, wherein the extractive distillation light component removal tower is an atmospheric distillation tower, the theoretical plate number of the atmospheric distillation tower is 20-80, the reflux ratio is 1-20, the feeding position of the 1-hexene-rich material flow is 5-75 from top, the feeding position of the second extractant is 2-10 from top, the tower top temperature is 55-65 ℃, and the tower kettle temperature is 60-160 ℃. According to another embodiment of this first aspect, the second extractant is selected from at least one of the following: n-methylpyrrolidone, N-formylmorpholine and N, N-dimethylformamide. According to another embodiment of this first aspect, the feed volume ratio of the second extractant to the 1-hexene rich stream is from 1:1 to 20: 1.

According to another embodiment of the first aspect, step (viii) is carried out in a purification column which is an atmospheric distillation column having a theoretical plate number of 20 to 80, a reflux ratio of 1 to 20, a feed position of the third mixture stream of 5 to 75 from above, and a feed position of the third extractant of 2 to 10 from above, according to another embodiment of the first aspect, a feed volume ratio of the second extractant to the third mixture stream of 0.5:1 to 1.5:1, an overhead temperature of 58 to 68 ℃, and a kettle temperature of 120 to 200 ℃. According to another embodiment of this first aspect, the third extractant is selected from at least one of the following: n-methylpyrrolidone, N-formylmorpholine and N, N-dimethylformamide.

A second aspect of the present invention provides an apparatus for separating and purifying 1-hexene, comprising, in order from upstream to downstream: the device comprises a pre-cutting tower, an azeotropic distillation tower, a reactive distillation tower, an extraction tower, a component heavy component removal tower, an extractive distillation light component removal tower and a 1-hexene purification tower.

According to an embodiment of this second aspect, the apparatus further comprises:

an alcohol recovery column disposed downstream of the extraction column, at least one outlet of the alcohol recovery column being connected to an azeotropic distillation column; and

an extractant recovery column located downstream of the 1-hexene purification column.

According to another embodiment of this second aspect, the apparatus further comprises: an alcohol recovery column disposed downstream of the extraction column, at least one inlet of the alcohol recovery column being connected to an outlet of the extraction column, and at least one outlet of the alcohol recovery column being connected to an inlet of the azeotropic distillation column.

According to another embodiment of this second aspect, the apparatus further comprises: and the extractant recovery tower is positioned at the downstream of the 1-hexene purification tower, at least one inlet of the extractant recovery tower is connected with an outlet of the 1-hexene purification tower, at least one outlet of the extractant recovery tower is connected with an inlet of the extractive distillation light component removal tower, and at least one outlet of the extractant recovery tower is connected with an inlet of the 1-hexene purification tower.

According to another embodiment of this second aspect, the pre-cut tower is provided with vertical partitions therein to divide the pre-cut tower into 4 sections: one side of the baffle for feeding is a pre-fractionating area, one side of the baffle for taking out is a side-line rectifying area, a public rectifying area is arranged above the baffle, and a public stripping area is arranged below the baffle; the number of theoretical plates in the pre-distillation zone is 5-15, the number of theoretical plates in the lateral line distillation zone is 5-15, the number of theoretical plates in the public distillation zone is 5-15, and the number of theoretical plates in the public stripping zone is 5-15. According to another embodiment of the second aspect, the at least one inlet of the pre-cut column is located between the 2 nd to 15 th plates from the top of the pre-fractionation zone, and the at least one outlet of the pre-cut column is located between the 2 nd to 15 th plates from the top of the side rectification zone.

According to another embodiment of the second aspect, the number of theoretical plates of the azeotropic distillation column is 20 to 40, and the azeotropic distillation column includes an inlet located at 3 to 35 th plates from the top and an inlet located at 1 to 10 th plates from the top.

According to another embodiment of the second aspect, the number of theoretical plates of the reactive distillation column is 20 to 40, and the inlet position is 10 to 35 from the top.

According to another embodiment of this second aspect, the number of theoretical plates of the extraction column is 3 to 10, and the at least one inlet of the extraction column is located at the first plate from the top of the extraction column and the at least one inlet is located at the last plate from the top of the extraction column.

According to another embodiment of the second aspect, the number of theoretical plates of the fine heavies removal column is 60 to 160, and at least one inlet is located at 10 to 50 th plates from the top.

According to another embodiment of the second aspect, the number of theoretical plates of the extractive distillation light component removal column is 20 to 80, at least one inlet is positioned at 5 to 75 plates from the top, and at least one inlet is positioned at 2 to 10 plates from the top.

According to another embodiment of the second aspect, the number of theoretical plates of the purification column is 20 to 80, at least one inlet thereof is located at 5 to 75 th plates from the top, and at least one inlet thereof is located at 2 to 10 th plates from the top.

Some embodiments of the present application will be described below with reference to the accompanying drawings.

Drawings

An illustration of the method and apparatus of the present invention is shown in the drawings, in which:

figure 1 shows a schematic diagram of the apparatus of the present invention for separating and purifying a stream comprising 1-hexene.

In the drawings, the names of the components corresponding to the respective reference numerals are as follows:

d1-precut tower; d2-azeotropic distillation column; r1-reactive rectification column; d3-extraction column (water wash column); d4-alcohol recovery column; d5-fine component heavy component removing tower; d6-extracting, rectifying and removing light components tower; d7-1-hexene purification tower, D8-extractant recovery tower;

1 is a stream comprising 1-hexene, 2 is a stream of fractions below C5, 3 is a stream of fractions rich in C6, 4 is a stream of fractions above C7, 5 is an entrainer stream, 6 is a first mixture stream comprising C1-C4 alcohols and C6 hydrocarbons, 7 is an oxygenate stream, 8 is a second mixture stream comprising C1-C4 alcohols and C6 hydrocarbons from which tertiary carbon olefins have been removed, 9 is an etherification product, 10 is a first extractant stream (water stream), 11 is a solution stream of entrainer in first extractant (water), 12 is a refined C6 hydrocarbon stream, 13 is a fresh entrainer stream, 14 is a fresh first extractant (water) stream, 15 is a stream rich in-1-hexene, 16 is a heavy component stream boiling above 1-hexene, 17 is an isomeric hydrocarbon stream boiling below 1-hexene, 18 is a third mixture stream, 19 is the 1-hexene product stream, 20 is the fourth mixture stream comprising the second extractant, the third extractant and the cycloalkene, 21 is the cycloalkene stream, 22 is the regenerated extractant stream, 23 is the fresh extractant stream, 24 is the second extractant stream, and 25 is the third extractant stream.

Detailed Description

The "ranges" disclosed herein are expressed in terms of lower and upper limits. There may be one or more lower limits, and one or more upper limits, respectively. The given range is defined by the selection of a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this manner are inclusive and combinable with each other, i.e., any lower limit can be combined with any upper limit to form a range. For example, ranges of 60-120 and 80-110 are listed for particular parameters, with the understanding that ranges of 60-110 and 80-120 are also contemplated. Further, if the minimum range values listed are 1 and 2, and the maximum range values are 3,4, and 5, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers.

In this application, the word "above" or "below" following a number includes the word. For example, "5 or less" means 5 or less, and "7 or more" means 7 or more.

In the present application, all embodiments and preferred embodiments mentioned herein may be combined with each other to form new solutions, if not specifically stated.

In the present application, all the technical features mentioned herein as well as preferred features may be combined with each other to form new technical solutions, if not specifically stated.

In the present application, all steps mentioned herein may be performed sequentially or randomly, if not specifically stated, but preferably sequentially. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.

In the present application, the term "comprising" as used herein means open or closed unless otherwise specified. For example, the term "comprising" may mean that other components not listed may also be included, or that only listed components may be included.

In this application, the terms "upstream" and "downstream" describe the relative positions of various components with respect to the flow of material, i.e., the flow of material passes "upstream" and then "downstream".

In the present application, the term "stream" means any flowable material fluid used or processed in the methods and apparatus of the present application, having objectively present material properties and flowable properties, which may include a gas, a liquid, a mixture of a gas and a liquid, a mixture of a liquid and a liquid, a solution of a gas in a liquid, a solution of a liquid in a liquid, a solution or suspension of a solid in a liquid, or a combination of one or more of the foregoing. For example, in the present application, a 1-hexene containing product (e.g., a 1-hexene containing product obtained from the fischer-tropsch reaction or any other process) as the initial feedstock, any portion that is split from the initial feedstock, and any reagents added to or recovered from it during processing, may be referred to as "streams".

In this application, "fractionation section," "distillate stream," "fraction," and the like are used interchangeably.

The term "light ends" is a mixture comprising mainly hydrocarbons of C1-C20, such as C5-C12, and oxygenates of alcohols, aldehydes, ketones, acids of C1-C20, such as C1-C8, possibly also in lower proportions with other unavoidable impurities, depending on the specific source, preparation process and separation technique of the light ends, but in very low amounts, which are substantially simultaneously removed during the separation and purification process of the present application, in the final 1-hexene product stream at an acceptable level, and therefore the separation of these impurities is not of particular interest in the technical solution of the present application. Wherein, the hydrocarbon compounds with the same carbon number include normal paraffin, isoparaffin, linear 1-olefin, branched olefin, internal olefin (i.e. olefin with double-bond alkenyl not at the end), diene, triene, arene, cyclane and cycloalkene, and the oxygen-containing compounds with the same carbon number include alcohol, aldehyde, ketone, acid and isomers thereof. According to one embodiment of the invention, the process and apparatus of the present application is used to treat a "stream comprising 1-hexene". For example, the "stream comprising 1-hexene" may be a syngas direct to olefins (FTO) product or a light hydrocarbon fraction obtained from a syngas direct to olefins (FTO) product via preliminary separation. The process for preparing olefin (FTO) directly from synthesis gas is a process for synthesizing hydrocarbon mixtures with various carbon numbers by using synthesis gas (mixed gas of carbon monoxide and hydrogen) as a raw material under a catalyst and proper conditions, wherein the product comprises the 1-hexene serving as a target product. It is emphasized here that while the present invention is primarily described in the context of the separation and purification of 1-hexene using a syngas direct to olefins (FTO) product or product light hydrocarbon fraction section, the method and apparatus of the present invention is applicable to any mixed hydrocarbon stream containing 1-hexene, such as may be used to treat a 1-hexene containing product stream obtained from one or more of the following processes, and as such achieves the benefits of the present application in the separation and purification of 1-hexene: Fischer-Tropsch synthetic oil, petroleum fractionation, coal rectification, alcohol dehydration, alkane oxidative dehydrogenation, a biological fermentation process, hydrocarbon catalytic reforming, hydrocarbon catalytic cracking, biological oil catalytic oxidation and the like. According to a preferred embodiment of the present invention, the 1-hexene containing feed as the initial feedstock is the light hydrocarbon cut fraction of the olefin product from a syngas direct to olefins (FTO) process.

In addition, using Cn hydrocarbons (or C6 fractions) to refer to collections or mixtures of hydrocarbons having n carbon atoms, for example C6 hydrocarbons to refer to collections or mixtures of hydrocarbons having 6 carbon atoms, in one embodiment herein C6 hydrocarbons can include alkanes having six carbon atoms, alkenes having six carbon atoms, alkynes having six carbon atoms, where alkanes having six carbon atoms can include all straight, branched, or cyclic alkanes having six carbon atoms, such as n-hexane, 2-methylpentane, 3-methylpentane, 2-dimethylbutane, 2, 3-dimethylbutane, cyclohexane, 1-methylcyclopentane, 1-ethylcyclobutane, 1-dimethylcyclobutane, 1, 2-dimethylcyclobutane, and the like; the olefin having six carbon atoms may include all linear, branched or cyclic olefins having six carbon atoms, or aromatic hydrocarbons such as 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, 3-methyl-1-pentene, 3-methyl-2-pentene, 4-methyl-1-pentene, 4-methyl-2-pentene, 2-dimethylbutane, 3-dimethyl-1-butene, cyclohexene, 1-methylcyclopentene, 3-methylcyclopentene, 1, 2-dimethylcyclobutene, benzene and the like; alkynes having six carbon atoms may include all straight, branched or cyclic alkynes having six carbon atoms, such as 1-hexyne and any isomers thereof. By Cn + hydrocarbons is meant herein a collection or mixture of hydrocarbons having n or more carbon atoms, for example C7+ hydrocarbons refers to a collection or mixture of hydrocarbons having 7 or more carbon atoms; by Cn-hydrocarbons is meant herein an aggregate or mixture of hydrocarbons having n or fewer carbon atoms, for example C5-hydrocarbons refers to an aggregate or mixture of hydrocarbons having 5 or fewer carbon atoms.

In this application, Cn-olefin is taken to mean a collection or mixture of olefins having n carbon atoms, for example C6-olefin is taken to mean a collection or mixture of hydrocarbons having 6 carbon atoms, and olefins having six carbon atoms may include all linear, branched or cyclic olefins having six carbon atoms, or aromatic hydrocarbons, for example 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, 3-methyl-1-pentene, 3-methyl-2-pentene, 4-methyl-1-pentene, 4-methyl-2-pentene, 2-dimethylbutane, 3-dimethyl-1-butene, cyclohexene, 1-methylcyclopentene, 3-methylcyclopentene, 1, 2-dimethylcyclobutene, benzene, etc. By Cn + alkene (hydrocarbon) is meant herein a collection or mixture of alkenes having n or more carbon atoms, for example C7+ alkene refers to a collection or mixture of alkenes having 7 or more carbon atoms; in this application Cn-ene is used to denote an aggregate or mixture of olefins having n or fewer carbon atoms, for example C5-ene denotes an aggregate or mixture of olefins having 5 or fewer carbon atoms. The above expressions are also expressions conventionally employed in the art. It is emphasized here that the embodiments shown in the figures and described below are merely exemplary embodiments of the invention, to which the scope of protection of the invention is not limited. The scope of the invention is defined by the claims and may include any embodiments within the scope of the claims, including but not limited to further modifications and alterations to these embodiments.

The method and apparatus of the present invention will now be described in detail with reference to figure 1. In one embodiment, the present invention provides a method of purifying 1-hexene, the method of purification being carried out using the apparatus shown in figure 1. The method comprises steps (i) to (viii) described below.

Step (i): a stream 1 comprising 1-hexene is provided, said stream 1 can have various compositions depending on the origin of said stream 1. For example, the stream may comprise, in addition to 1-hexene, the following components: normal paraffins in the range of C4 to C100, isoparaffins, cycloalkanes, linear 1-olefins other than 1-hexene, branched olefins, aromatic hydrocarbons, oxygenates. Preferably, the stream comprising 1-hexene is a product obtained from a syngas direct to olefins (FTO) process or a light ends stream obtained from a preliminary fractionation of a syngas direct to olefins (FTO) product. According to a preferred embodiment, the synthesis gas direct to olefins (FTO) product or the light fraction of the synthesis gas direct to olefins (FTO) product has a weight percent oxygenate content of 5 to 20%, the linear 1-hexene content may be greater than 2%, or greater than 3%, or greater than 5%, or 8% or 10%, and the upper limit of the linear 1-olefin weight percentage may be, for example, 80 wt% or 70 wt% or 60 wt% or 50 wt% or 48 wt% or 45 wt%. In this step (i), the above stream 1 comprising 1-hexene is sent to a precut column D1 for the subsequent step (ii).

Step (ii): stream 1 comprising 1-hexene is subjected to a pre-cut fractionation in pre-cut column D1, in which step a C5 lower fraction stream 2 and a C7 upper fraction stream 4 are at least partially removed to obtain a C6 enriched fraction stream 3, said C6 fraction stream comprising C6 hydrocarbons. In the present application, the expression "C6-rich fraction stream" means that the relative content of the six carbon atoms-containing fraction in this stream 3 is higher than in said stream 1. According to one embodiment, the C6 fraction content of the C6-rich fraction stream 3 is increased by at least 10%, such as at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 35%, or at least 40%, or at least 45%, or at least 50%, or at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 100%, or at least 110%, or at least 120%, or at least 130%, based on the weight percent of the C6 fraction in stream 1, or at least 140%, or at least 150%, or at least 160%, or at least 170%, or at least 180%, or at least 190%, or at least 200%, or at least 220%, or at least 240%, or at least 250%, or at least 280%, or at least 300%, or at least 330%, or at least 350%, or at least 370%, or at least 400%, or at least 430%, or at least 450%, or at least 470%, or at least 500%. According to another embodiment of the present application, the 1-hexene content in stream 1 is between 10 wt% and 50 wt%, while the weight percentage of 1-hexene in the C6 rich fraction stream 3 is higher than 1-hexene in stream 1 after the pre-cut fractionation, e.g. the weight percentage of 1-hexene in the C6 rich fraction stream 3 is increased to between 20 wt% and 80 wt%, e.g. between 30 wt% and 75 wt%, e.g. between 40 wt% and 72 wt%, e.g. between 50 wt% and 70 wt%, e.g. between 60 wt% and 79 wt%. The "C6-rich fraction stream 3" may comprise, in addition to the target product 1-hexene and various other linear alkanes and olefins in the synthesis gas direct olefin (FTO) product, other oxygenates, such as alcohols, aldehydes, ketones, including acetone, butanone, ethanol, isopropanol, n-propanol, n-butanol, 2-butanol, isobutanol, propionaldehyde, butyraldehyde, isobutyraldehyde, and other C2 to C5 alkanes, including 2-methylpentane, 3-methylpentane, various C6 isoparaffins including 3-methylcyclopentene, 4-methylcyclopentene, cyclohexene, 1-methylcyclopentene, various C6 cycloolefins including 2-methyl-1-pentene and 2-ethyl-1-butene, and the like, and C6 tertiary olefins.

According to one embodiment of the present application, the C6-rich fraction stream 3 comprises mainly 1-hexene, other C6 olefins, other C6 alkanes, oxygenates and minor amounts of C5-and C7+ hydrocarbon fractions, and the like.

In one embodiment, said step (ii) is carried out in a pre-cut tower provided with vertical partitions therein to divide the pre-cut tower into 4 sections: the side feeding side of the partition is a pre-distillation area, the side drawing side of the partition is a side-distillation area, a public distillation area is arranged above the partition, and a public stripping area is arranged below the partition, wherein the number of theoretical plates in the pre-distillation area is 5-15, the number of theoretical plates in the side-distillation area is 5-15, the number of theoretical plates in the public distillation area is 5-15, and the number of theoretical plates in the public stripping area is 5-15. Wherein stream 1 from step (i) comprising 1-hexene is fed from the 2 nd to 15 th trays from the top of the pre-fractionation zone and the withdrawal of the C6 rich fraction stream is carried out at the 2 nd to 15 th trays from the top of the side-stream rectification zone. In one embodiment, the reflux ratio in the precut tower can be 1-10, for example, 2-10, 3-10, 4-10, 5-10, 6-10, 7-10, 8-10, or even 9-10, the temperature at the top of the tower is 20-40 ℃, and the temperature at the bottom of the tower is 100-150 ℃. According to a preferred embodiment, the pressure in the pre-cut tower is between 0.01 and 1.0MPa, such as between 0.1 and 0.5MPa, or between 0.5 and 0.8MPa, or between 0.8 and 1.0MPa, for example the pre-cut tower is operated at atmospheric pressure. The C6-rich fraction stream 3 obtained in step (ii) is further sent to step (iii) for azeotropic distillation operation.

Step (iii) is an azeotropic distillation step in which the C6-rich fraction stream 3 obtained from step (ii) and an entrainer 5 are fed to an azeotropic distillation column D2 where azeotropic distillation is carried out to remove an oxygenate stream 7, thereby obtaining a first mixture stream 6, which first mixture stream 6 comprises mainly said entrainer and C6 hydrocarbons. According to one embodiment of the present application, the entrainer may be one or more C1-C4 alcohols used to azeotropes with C6 hydrocarbons to remove oxygenates from the C6 distillate stream by rectification. According to one embodiment of the invention, the C1-C4 alcohol is selected from at least one of the following: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 2-methyl-1, 3-propanediol, 3-methyl-1, 2-propanediol, 1,2, 3-propanetriol, 1,2, 3-butanetriol, 1,2, 4-butanetriol, 2-methyl-1, 2, 3-propanetriol, 1,2,3, 4-butanetetraol, or any mixture thereof; preferably methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol; more preferably methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol; more preferably methanol and ethanol; methanol is most preferred.

In one embodiment, step (iii) is carried out in azeotropic distillation column D2, the number of theoretical plates in the azeotropic distillation column is 20 to 40, the C6-rich fraction stream 3 is fed at the 3 rd to 35 th plates from the top, and the entrainer C1-C4 alcohol is fed at the 1 st to 10 th plates from the top. According to a preferred embodiment, the feeding position of the entrainer 5 is higher than the feeding position of the C6 rich fraction stream 3. In the present invention, the reflux ratio can be 1-10, for example, 2-10, 3-10, 4-10, 5-10, 6-10, 7-10, 8-10, even 9-10.

In one embodiment, the volumetric flow ratio of entrainer 5 (preferably a C1-C4 alcohol) to C6-rich fraction stream 3 in step (iii) is from 0.1:1 to 1.5:1, e.g., from 0.2:1 to 1.5:1, from 0.3:1 to 1.5:1, from 0.4:1 to 1.5:1, from 0.5:1 to 1.5:1, from 0.6:1 to 1.5:1, from 0.7:1 to 1.5:1, from 0.8:1 to 1.5:1, from 0.9:1 to 1.5:1, from 1.0:1 to 1.5:1, from 1.1:1 to 1.5:1, from 1.2:1 to 1.5:1, from 1.3:1 to 1.5:1, from 1.4:1 to 1.5:1, from 0.1:1 to 1.4:1, from 1:1 to 1.5:1, from 0:1, from 1.1:1 to 1.5:1, from 0: 1.1:1 to 1, from 1.4:1, from 1.5:1, from 1:1 to 1.5:1, from 1.1, from 1:1, from 1.1: 1.1.1, from 1 to 1, from 1.4:1, from 1:1 to 1.5:1, from 1.4:1, from 1: 1.4:1, from 1.1.1, from 1 to 1, from 1.1.5: 1.1, from 1, from 1.1.1, 0.1:1 to 1.3:1, 0.2:1 to 1.3:1, 0.3:1 to 1.3:1, 0.4:1 to 1.3:1, 0.5:1 to 1.3:1, 0.6:1 to 1.3:1, 0.7:1 to 1.3:1, 0.8:1 to 1.3:1, 0.9:1 to 1.3:1, 1.0:1 to 1.3:1, 1.1:1 to 1.3:1, 1.2:1 to 1.3:1, 0.1:1 to 1.2:1, 0.2:1 to 1.2:1, 0.3:1 to 1.2:1, 0.4:1 to 1.2:1, 0.5:1 to 1.2:1, 0.6:1 to 1.2:1, 0.7:1 to 1.1:1, 1.1 to 1.1.1: 1, 1.1:1, 1:1, 0.1:1, 1: 1.1:1, 0.1:1, 0.1:1, 0.1: 1: 1.1:1, 0.1: 1.1: 1: 1.1:1, 0.1:1, 0.1:1 to 1.0:1, 0.2:1 to 1.0:1, 0.3:1 to 1.0:1, 0.4:1 to 1.0:1, 0.5:1 to 1.0:1, 0.6:1 to 1.0:1, 0.7:1 to 1.0:1, 0.8:1 to 1.0:1, 0.9:1 to 1.0:1, 0.1:1 to 0.9:1, 0.2:1 to 0.9:1, 0.3:1 to 0.9:1, 0.4:1 to 0.9:1, 0.5:1 to 0.9:1, 0.6:1 to 0.9:1, 0.7:1 to 0.9:1, 0.8:1 to 0.9:1, 0.1 to 0.8:1, 0.1:1 to 0.8:1, 0.1 to 1.1, 0.1 to 0.1, 0.1 to 1.1, 0.6:1, 0.1 to 0.1, 0.1:1 to 0.0.1, 0.7:1, 0.8:1, 0.1 to 1:1, 0.1:1 to 0.1, 0.1.1, 0.1 to 0.0.0.0.1 to 0.0.0.0.0.0.0.1: 1, 0.1:1 to 0.0.0.0.0.0.0.0.1: 1, 0.0 to 0.1, 0.0.1 to 1 to 0.0.1, 0.8:1, 0.1 to 0, 0.4:1 to 0.6:1, 0.5:1 to 0.6:1, 0.1:1 to 0.5:1, 0.2:1 to 0.5:1, 0.3:1 to 0.5:1, 0.4:1 to 0.5:1, 0.1:1 to 0.4:1, 0.2:1 to 0.4:1, 0.3:1 to 0.4:1, 0.1:1 to 0.3:1, 0.2:1 to 0.3:1 or 0.1:1 to 0.2:1, for example, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, preferably 0.3:1 to 1.0: 1. According to an embodiment of the present invention, the weight ratio of entrainer and 1-hexene in the first mixture stream 6 obtained from step (iii) may be from 0.1:1 to 1.5:1, e.g. from 0.2:1 to 1.5:1, from 0.3:1 to 1.5:1, from 0.4:1 to 1.5:1, from 0.5:1 to 1.5:1, from 0.6:1 to 1.5:1, from 0.7:1 to 1.5:1, from 0.8:1 to 1.5:1, from 0.9:1 to 1.5:1, from 1.0:1 to 1.5:1, from 1.1:1 to 1.5:1, from 1.2:1 to 1.5:1, from 1.3:1 to 1.5:1, from 1.4:1 to 1.5:1, from 0.1:1 to 1.4:1, from 0:1 to 1.4:1, from 1.1:1 to 1, from 0:1, from 1.4:1, from 1 to 1, from 1.5:1, from 1: 1.4:1, from 1 to 1, from 1.4:1, from 1: 1.1.1.5: 1, from 1 to 1, from 1.4:1, from 1.1:1, from 1: 1.1: 1: 1.4:1, from 1 1.3:1 to 1.4:1, 0.1:1 to 1.3:1, 0.2:1 to 1.3:1, 0.3:1 to 1.3:1, 0.4:1 to 1.3:1, 0.5:1 to 1.3:1, 0.6:1 to 1.3:1, 0.7:1 to 1.3:1, 0.8:1 to 1.3:1, 0.9:1 to 1.3:1, 1.0:1 to 1.3:1, 1.1:1 to 1.3:1, 1.2:1 to 1.3:1, 0.1:1 to 1.2:1, 0.2:1 to 1.2:1, 0.3:1 to 1.2:1, 0.4:1 to 1.2:1, 0.5:1 to 1.2:1, 0.1 to 1.1:1, 1:1 to 1.1, 1.1:1, 0.1:1 to 1.1.1: 1, 1: 1.1:1, 0.1:1 to 1.1, 0.1: 1.1:1, 0.1:1, 1: 1.1:1, 0.1: 1: 1.1:1, 0.1:1, 0.1: 1.1:1, 0.1:1, 0.1: 1: 1.1: 1: 1.1.1: 1, 0.1: 1.1:1, 0.1:1, 0.1, 1.0:1 to 1.1:1, 0.1:1 to 1.0:1, 0.2:1 to 1.0:1, 0.3:1 to 1.0:1, 0.4:1 to 1.0:1, 0.5:1 to 1.0:1, 0.6:1 to 1.0:1, 0.7:1 to 1.0:1, 0.8:1 to 1.0:1, 0.9:1 to 1.0:1, 0.1:1 to 0.9:1, 0.2:1 to 0.9:1, 0.3:1 to 0.9:1, 0.4:1 to 0.9:1, 0.5:1 to 0.9:1, 0.6:1 to 0.9:1, 0.7:1 to 0.9:1, 0.8:1 to 0.9:1, 0.1 to 1.1, 0.1 to 1.8: 1, 0.1 to 1.1, 0.1 to 1.0.1, 0.1 to 1.0.0.0.1: 1, 0.6:1, 0.1 to 0.1, 0.1:1, 0.7:1 to 0.1, 0.1:1, 0.8:1 to 1, 0.1 to 1.0.0.0.0.0.0.1: 1, 0.0.1, 0.1 to 1:1, 0.8:1, 0.0.0.0.0.0.1 to 1, 0.0.0.0.0.0.0: 1, 0.0.1, 0.1, 0.0.0.0.0.0, 0.3:1 to 0.6:1, 0.4:1 to 0.6:1, 0.5:1 to 0.6:1, 0.1:1 to 0.5:1, 0.2:1 to 0.5:1, 0.3:1 to 0.5:1, 0.4:1 to 0.5:1, 0.1:1 to 0.4:1, 0.2:1 to 0.4:1, 0.3:1 to 0.4:1, 0.1:1 to 0.3:1, 0.2:1 to 0.3:1, or 0.1:1 to 0.2: 1. In one embodiment, the azeotropic distillation column D2 used in step (iii) has a top temperature of 40 to 60 ℃ and a bottom temperature of 50 to 100 ℃. According to a preferred embodiment, the pressure in the azeotropic distillation column D2 is in the range of 0.01 to 1.0MPa, such as in the range of 0.1 to 0.5MPa, or in the range of 0.5 to 0.8MPa, or in the range of 0.8 to 1.0MPa, for example the azeotropic distillation column D2 is operated at atmospheric pressure. According to one embodiment of the invention, the total amount of oxygenates in the C6-rich fraction stream 3 may be in the range of from 0.5 to 20 wt.%, such as from 1 to 18 wt.%, or from 2 to 15 wt.%, or from 3 to 12 wt.%, or from 5 to 10 wt.%, or from 8 to 10 wt.%, prior to the azeotropic distillation step (iii). After the azeotropic distillation step (iii), the majority of the oxygenates are removed as oxygenate stream 7. According to a preferred embodiment of the present invention, after the azeotropic distillation step (iii), the removal ratio of the oxygenates in the C6-rich fraction stream 3 is more than 80%, alternatively more than 85%, alternatively more than 90%, alternatively more than 95%, alternatively more than 99%, alternatively more than 99.9%, alternatively more than 99.99%. In the present invention, the oxygenate originally contained in the C6-rich fraction stream 3 and the entrainer added in step (iii) are not of the same nature. According to a particularly preferred embodiment, after removal of the oxygenates by azeotropic distillation in step (iii), the first mixture stream 6 obtained is not detectable for any other oxygenates than alcohols as entrainers, i.e. the oxygenates in stream 6 are present in an amount below the lower limit of detection of conventional laboratory or industrial scale detection techniques. The first mixture stream obtained after oxygenate removal in step (iii) is sent to step (iv) for reactive distillation treatment.

In step (iv), the first mixture stream 6 obtained in step (iii) is subjected to reactive distillation in the presence of a C1-C4 alcohol to remove tertiary carbon olefins, thereby obtaining a second mixture stream comprising an entrainer (e.g. a C1-C4 alcohol) and C6 hydrocarbons from which tertiary carbon olefins have been removed. According to a preferred embodiment of the present application, the entrainer is a C1-C4 alcohol as described above, in which case there is no need to add a C1-C4 alcohol to step (iv). In one embodiment, step (iv) is carried out in reactive rectification column R1. In one embodiment, the number of theoretical plates of the reactive distillation column R1 is 20-40, the reflux ratio is 1-10, the feeding position of the first mixture material flow 6 is 10-35 plates from top, the temperature of the top of the column is 40-70 ℃, and the temperature of the bottom of the column is 80-120 ℃. According to a preferred embodiment, the pressure in the reactive rectification column R1 is in the range of 0.01-1.0MPa, such as in the range of 0.1-0.5MPa, or in the range of 0.5-0.8MPa, or in the range of 0.8-1.0MPa, for example the reactive rectification column R1 is operated at atmospheric pressure.

In one embodiment, the reactive rectification column R1 is packed with an etherification catalyst, which is preferably a strongly acidic cationic resin, preferably Amberlyst 15 or Amberlyst 35. The tertiary olefins in the first mixture stream 6 react with the C1-C4 alcohol in the presence of the etherification catalyst to form ethers, which can then be removed as etherification product stream 9 by rectification in the reactive rectification column R1. After said first mixture stream 6 is fed to reactive distillation column R1 where etherification reactions take place to convert tertiary olefins therein to ethers and after removal as etherification product stream 9, a second mixture stream 8 is obtained. In one embodiment, the reactive distillation column R1 is composed of three sections, a distillation section, a reaction section and a stripping section in sequence from top to bottom. The reaction section comprises a plurality of catalyst beds, for example 3,4, 5, 6, 7, 8, 9, 10, on which the catalyst is loaded, for example in the form of packing packs. Structured packing is filled between each bed. According to one embodiment, the first mixture stream is fed from below the lower catalyst bed. After the reactive distillation step (iv), the majority of the tertiary olefin is removed as etherification product stream 9. According to a preferred embodiment of the present invention, after the reactive distillation step (iv), the removal ratio of tertiary olefins in the first mixture stream 6 is greater than 80%, alternatively greater than 85%, alternatively greater than 90%, alternatively greater than 95%, alternatively greater than 99%, alternatively greater than 99.9%, alternatively greater than 99.99%. According to a particularly preferred embodiment, after removal of the tertiary olefins by reactive distillation in step (iv), no tertiary olefins can be detected in the resulting second mixture stream 8, i.e. the content of tertiary olefins in stream 8 is below the lower limit of detection of conventional laboratory or industrial scale detection techniques. The second mixture stream 8 obtained in step (iv) from which the tertiary olefins have been removed, comprising mainly C6 hydrocarbons and an entrainer (C1-C4 alcohol, preferably methanol), is fed to an extraction column D3 in which step (v) is carried out in which the entrainer in the second mixture stream 8 is removed by extraction with a first extractant (e.g. water), the solution stream 11 of which in the first extractant is taken off at the bottom of the column, and the refined C6 hydrocarbon stream 12 from which the entrainer has been removed is fed to a subsequent de-heavies step (vi). According to a preferred embodiment of the present application, the first extractant is water and stream 11 is a mixture of C1-C4 alcohols in water. According to one embodiment of the present application, step (v) is performed in extraction column D3, which can be referred to as a water wash column when the first extractant is water. In one embodiment, the extraction column has from 3 to 10 theoretical plates, and the water and second mixture stream 8 are fed from the first and last plates, respectively, above. The weight ratio of the first extractant (water) stream 10 and the second mixture stream 8 is referred to as the water-to-oil ratio, and according to one embodiment, the water-to-oil ratio is 0.4 to 4, such as 0.4 to 3, 0.4 to 3.5, 0.4 to 3, 0.4 to 2.5, 0.4 to 2.0, 0.4 to 1.5, 0.4 to 1.0, or 0.4 to 0.5, and can be, for example, within the range of any two of the following values in combination: 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9.

In the extraction column D3, the operating temperature in step (v) is 5 to 45 ℃, for example, 5 to 40 ℃,5 to 35 ℃,5 to 30 ℃,5 to 25 ℃,5 to 20 ℃,5 to 15 ℃,5 to 10 ℃, 10 to 45 ℃, 10 to 40 ℃, 10 to 35 ℃, 10 to 30 ℃, 10 to 25 ℃, 10 to 20 ℃, 10 to 15 ℃, 15 to 45 ℃, 15 to 40 ℃, 15 to 35 ℃, 15 to 30 ℃, 15 to 25 ℃, 15 to 20 ℃, 20 to 45 ℃, 20 to 40 ℃, 20 to 35 ℃, 20 to 30 ℃, 20 to 25 ℃, 25 to 45 ℃, 25 to 40 ℃, 25 to 35 ℃, 25 to 30 ℃, 30 to 45 ℃, 30 to 40 ℃, 30 to 35 ℃, 35 to 45 ℃, 35 to 40 ℃, 40 to 45 ℃, and can be, for example, within the range of values obtained by combining any two of the following endpoints: 5. 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 ℃. After said step (v), the major part of the entrainer is removed as a solution stream 11 of entrainer in the first extractant. According to an embodiment of the present invention, the total amount of entrainer in the second mixture stream 8 prior to step (v) may be in the range of from 10 to 40 wt%, such as from 12 to 35 wt%, or from 15 to 30 wt%, or from 18 to 28 wt%, or from 20 to 25 wt%. According to a preferred embodiment of the present invention, after the extraction step (v), the removal proportion of entrainer contained in the second mixture stream 8 is more than 80%, alternatively more than 85%, alternatively more than 90%, alternatively more than 95%, alternatively more than 99%, alternatively more than 99.9%, alternatively more than 99.99%. According to a particularly preferred embodiment, after removal of the entrainer by extraction with the first extractant in step (v), no residual entrainer is detectable in the resulting refined C6 hydrocarbon stream 12, i.e. the amount of entrainer in stream 12 is below the lower limit of detection for conventional laboratory or industrial scale detection techniques. According to one embodiment of the present application, the weight percentage of 1-hexene in the refined C6 hydrocarbon stream 12 is increased to 50 wt% to 95 wt%, such as 60 wt% to 90 wt%, such as 70 wt% to 89 wt%, such as 80 wt% to 88 wt%, such as 85 wt% to 88 wt%.

Step (vi) is a heavies removal step in which the refined C6 hydrocarbon stream 12 obtained in step (v) is passed to a heavies removal column D5 in which a heavies removal operation is carried out to remove heavies hydrocarbons boiling above 1-hexene, which are removed as heavies hydrocarbon stream 16, which stream 16 may be directly burned off, disposed of as waste, subjected to purification and separation operations such as further fractionation, or used in other chemical processes as a reactant or adjunct. After removal of the heavies hydrocarbons, a 1-hexene rich stream 15 is obtained, which 1-hexene rich stream 15 comprises mainly 1-hexene and C6 hydrocarbons boiling below that of 1-hexene. In one embodiment, the fine heavies removal of step (vi) is performed in a fine heavies removal column D5, according to one embodiment of the present application, the fine heavies removal column D5 is an atmospheric distillation column with a theoretical plate number of 60 to 160. The reflux ratio is 10 to 40, for example, 15 to 40, 20 to 40, 25 to 40, 30 to 40, 35 to 40, 15 to 35, 20 to 35, 25 to 35, 30 to 35, 15 to 30, 20 to 30, 25 to 30, 15 to 25, 15 to 20, or 20 to 25. According to one embodiment of the application, the feeding position of the refined C6 hydrocarbon material flow 12 is 10 th to 50 th plates from the top, the temperature of the top of the tower is 58 ℃ to 68 ℃, and the temperature of the bottom of the tower is 60 ℃ to 90 ℃. According to a preferred embodiment, the pressure in the fine heavies removal column D5 is in the range of from 0.01 to 1.0MPa, such as from 0.1 to 0.5MPa, or from 0.5 to 0.8MPa, or from 0.8 to 1.0MPa, for example the fine heavies removal column D5 is operated at atmospheric pressure. According to one embodiment of the present application, after performing said step (vi), the 1-hexene content in said 1-hexene rich stream 15 is increased by at least 1 wt.%, such as by at least 1.5 wt.%, or by at least 2 wt.%, or by at least 2.5 wt.%, or by at least 3 wt.%, or by at least 3.2 wt.%, or by at least 3.4 wt.% relative to the 1-hexene content in the refined C6 hydrocarbon stream.

Step (vii) is an extractive distillation step in which the 1-hexene rich stream 15 obtained in step (vi) is fed to an extractive distillation light ends removal column D6 while a second extractant stream 24 is fed to the extractive distillation light ends removal column D6, the 1-hexene rich stream 15 is subjected to extractive distillation with a second extractant to remove C6 hydrocarbons having a lower boiling point than 1-hexene and is discharged as C6 hydrocarbon stream 17 having a lower boiling point than 1-hexene, which stream 17 can be directly burned off, treated as waste, subjected to purification and separation operations such as further fractionation, or used in other chemical processes as a reactant or an auxiliary. Thereby obtaining a third mixture stream 18, the third mixture stream 18 comprising primarily the second extractant and 1-hexene. In one embodiment, the extractive distillation in step (vii) is performed in an extractive distillation light component removal column D6, wherein the extractive distillation light component removal column D6 is an atmospheric distillation column with a theoretical plate number of 20 to 80 and a reflux ratio of 1 to 20, for example, 2,3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19. The feeding position of the 1-hexene-rich material flow 15 is 5-75 blocks from the top, and the feeding position of the second extractant flow 24 is 2-10 plates from the top. According to a preferred embodiment, the second extractant stream 24 is fed at a position above the 1-hexene rich stream 15. According to another embodiment, the feed volume ratio of the second extractant stream 24 to the 1-hexene rich stream 15 is in the range of from 1:1 to 20:1, for example within the range of any two of the following values in combination: 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19: 1. According to one embodiment of the application, the temperature of the tower top is 55-65 ℃, and the temperature of the tower kettle is 60-160 ℃. According to a preferred embodiment, the pressure in the extractive distillation light ends removal column D6 is in the range of 0.01 to 1.0MPa, such as in the range of 0.1 to 0.5MPa, alternatively 0.5 to 0.8MPa, alternatively 0.8 to 1.0 MPa. In one embodiment, the second extractant is selected from one of N-methylpyrrolidone, N-formylmorpholine, N-dimethylformamide, preferably N-methylpyrrolidone. According to a preferred embodiment of the present invention, after said step (vii), said 1-hexene rich stream 15 comprises a removal proportion of C6 hydrocarbons boiling lower than 1-hexene of more than 80%, alternatively more than 85%, alternatively more than 90%, alternatively more than 95%, alternatively more than 99%, alternatively more than 99.9%, alternatively more than 99.99%. According to one embodiment of the present application, the stream 18 comprises predominantly the second extractant and 1-hexene in a weight percentage from 50 wt% to 90 wt%, such as from 60 wt% to 85 wt%, such as from 65 wt% to 82 wt%, such as from 68 wt% to 80 wt%, such as from 70 wt% to 78 wt%. According to one embodiment of the invention, the third mixture stream 18 additionally comprises very small amounts of cycloolefins, for example the cycloolefin content can be 1% by weight or less, for example 0.8% by weight or less, or 0.6% by weight or less, or 0.5% by weight or less, or 0.4% by weight or less, or 0.2% by weight or less, or 0.1% by weight or less.

Step (viii) is an extraction step in which the third mixture stream 18 obtained in step (vii) is fed to the 1-hexene purification column D7, while the third extractant stream 25 is fed to the 1-hexene purification column D7: (viii) extracting the third mixture stream 18 obtained in step (vii) with a third extractant, resulting in a 1-hexene product stream 19 and a fourth mixture stream 20, said fourth mixture stream 20 comprising said second extractant, third extractant and cyclic olefin. In one embodiment, step (viii) is performed in purification column D7. According to an embodiment of the present application, the purification column D7 is an atmospheric distillation column, the number of theoretical plates is 20 to 80, and the reflux ratio can be 1 to 20, and for example, can be within a range of values obtained by combining any two following values: 2.3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19. The third mixture stream 18 is fed from 5 th to 75 th plates from the top, and the third extractant stream 25 is fed from 2 th to 10 th plates from the top. According to a preferred embodiment, the feed position of the third extractant stream 25 is above the feed position of the third mixture stream 18. According to a preferred embodiment, the feed volume ratio of the third extractant to the third mixture stream 18 is from 0.5:1 to 1.5:1, preferably from 1:1 to 1.2:1, the overhead temperature is from 58 to 68 ℃ and the still temperature is from 120 to 200 ℃. According to a preferred embodiment, the pressure in the purification column D7 is between 0.01 and 1.0MPa, such as between 0.1 and 0.5MPa, or between 0.5 and 0.8MPa, or between 0.8 and 1.0 MPa. In one embodiment, the third extractant is selected from: n-methyl pyrrolidone, N-formyl morpholine (NFM) and N, N-dimethylformamide, and N-methyl pyrrolidone is preferred. Preferably, the second extractant is the same as the third extractant, preferably both extractants are N-methylpyrrolidone. According to a preferred embodiment of the present application, the 1-hexene content of the target product 1-hexene in the 1-hexene product stream is between 85 and 99.9 wt%, such as ≥ 88 wt%, or ≥ 90 wt%, or ≥ 92 wt%, or ≥ 94 wt%, or ≥ 95 wt%, or ≥ 96 wt%, or ≥ 98 wt%, or ≥ 99 wt%.

According to another embodiment of the present invention, the method of the present application additionally comprises optional step (a) and step (b). Step (a) and step (b) will be further described below.

In one embodiment, the present invention optionally performs step (a) after step (v), which step (a) comprises performing a step of recovering a C1-C4 alcohol in alcohol recovery column D4. In one embodiment, the recovery is performed in a recovery column D4, which is an atmospheric distillation column having 8 to 50 theoretical plates. According to one embodiment of the present application, the solution stream 11 of entrainer in the first extractant, which is output from the extraction column D3 in step (v), is sent to a recovery column D4 where a distillation is carried out to separate the entrainer and the first extractant from each other in this recovery column 4. The separated entrainer is mixed with an optionally provided fresh entrainer 13 to form an entrainer stream 5 which is conveyed to an azeotropic distillation tower D2; the separated first extractant is mixed with an optional supply of fresh first extractant 14 to form first extractant stream 10 which is fed to extraction column D3. In one embodiment, the reflux ratio in the recovery column D4 is 1 to 12, and may be, for example, within a range of values defined by a combination of any two of the following endpoints: 2.3, 4, 5, 6, 7, 8, 9, 10, 11. The feeding position of the entrainer in the solution material flow 11 of the first extracting agent is 3-35 tower plates, the tower top temperature is 50-80 ℃, and the tower kettle temperature is 90-120 ℃. According to a preferred embodiment, the pressure in the recovery column D4 is in the range of 0.01 to 1.0MPa, such as in the range of 0.1 to 0.5MPa, alternatively 0.5 to 0.8MPa, alternatively 0.8 to 1.0MPa, for example the recovery column D4 is operated at atmospheric pressure.

In one embodiment, after steps (vii) and (viii), preferably after step (viii), a fourth mixture stream 20 comprising a second extractant and a third extractant is sent to extractant recovery column D8, separating the cyclic olefin stream 21 from the second and third extractants. According to a preferred embodiment, the second and third extractant are of the same kind. Preferably, the extractant recovery tower D8 is an atmospheric distillation tower, the number of theoretical plates is 6-40, the reflux ratio is 1-20, the feeding position of the material flow 20 is 2-35 from top, the temperature of the top of the tower is 55-80 ℃, and the temperature of the bottom of the tower is 140-250 ℃. According to a preferred embodiment, the pressure in the extractant recovery column D8 is in the range of 0.01 to 1.0MPa, such as in the range of 0.1 to 0.5MPa, alternatively 0.5 to 0.8MPa, alternatively 0.8 to 1.0MPa, for example the recovery column D4 is operated at atmospheric pressure. After separation a stream 21 comprising cycloalkene is obtained, which stream 21 can be directly burnt off, treated as waste, subjected to purification and separation operations such as further fractionation or used in other chemical processes as reactants or auxiliaries. A regenerated extractant stream 22 is additionally obtained which is mixed with an optionally supplemented fresh extractant stream 23 and fed as required as a second extractant stream 24 and a third extractant stream 25 to the extractive rectification lightens-removing column D6 and the 1-hexene purification column D7.

In another aspect, the present invention provides an apparatus for purifying 1-hexene comprising a design as shown in figure 1:

precut column D1 for precut fractionation of stream 1 comprising 1-hexene at least partially removing C5 lower distillate stream 2 and C7 upper distillate stream 4 to obtain C6 rich distillate stream 3;

(iv) an azeotropic distillation column D2 downstream of pre-cut column D1 for azeotropic distillation of the C6 cut stream obtained from step (iii) to remove oxygenates 7;

a reactive rectification column R1 downstream of the azeotropic rectification column D2 for reactive rectification of the first mixture stream 6 coming out of the upstream azeotropic rectification column D2 to remove tertiary carbon olefins 9;

an extraction column D3 downstream of the reactive rectification column R1; preferably, the extraction column D3 is a water wash column;

a fine heavies removal column D5 downstream of the extraction column D3;

an extractive distillation light component removing tower D6 is arranged at the downstream of the fine component heavy component removing tower D5;

a 1-hexene purifying column D7 downstream of the extractive distillation light component removing column D6.

In another embodiment, the apparatus further comprises: an alcohol recovery column D4 and an extractant recovery column D8.

According to some embodiments of the present application, 1-hexene products having a purity of greater than 98.5% may be separated from a syngas direct to olefin (FTO) process product using the purification apparatus and methods of the present application.

Without wishing to be bound by any particular theory, the present invention has the following advantages over the prior art:

(1) the removal of the oxygen-containing compounds adopts an azeotropic distillation mode, and by utilizing the characteristic that the temperature of an azeotrope formed by methanol and a C6 hydrocarbon material flow is lower than that of an azeotrope formed by other oxygen-containing compounds and C6 hydrocarbon, the oxygen-containing compounds except methanol in the C6 hydrocarbon material flow can be removed by a simple one-step method, and compared with the flow of removing the oxygen-containing compounds by the existing liquid-liquid extraction mode and the extraction distillation mode, the process flow is simple and the energy consumption is low;

(2) the azeotropic agent used in removing the oxygen-containing compound by the azeotropic distillation method and the downstream reactant participating in the etherification reaction are all methanol, the mixed material flow of the methanol and the C6 hydrocarbon in the discharge at the top of the azeotropic distillation tower does not need to remove the methanol and can directly enter the downstream etherification reaction distillation tower for the etherification reaction, and the methanol recovery tower can be shared by the recovery of the azeotropic agent methanol and the excessive methanol in the etherification reactant, so that the process flow is simplified, and the equipment investment cost is reduced;

(3) c6 isomeric hydrocarbon with a boiling point lighter than 1-hexene is removed by adopting an extraction and rectification mode, the existence of the extracting agent can increase the relative volatility between a light component and 1-hexene, and compared with the existing mode of removing isomeric hydrocarbon with a boiling point lower than 1-hexene by precision rectification with high plate number and high reflux ratio, the method makes full use of the action of the extracting agent, effectively reduces the separation plate number and reflux ratio, has less equipment investment and high product purity;

(4) based on the special combination of the specific steps, the method can achieve the aim of obtaining higher 1-hexene concentration of the target product with simpler equipment structure, lower capital construction cost and operation cost.

Examples

Preferred embodiments of the present invention are specifically exemplified in the following examples, but it should be understood that the scope of the present invention is not limited thereto. In the following inventive and comparative examples of the present application, the product light hydrocarbon fraction of synthesis gas direct to olefins (FTO) was used as feedstock, which was carried out according to the process conditions of the literature (Cobalt carbide nanoparticles for direct production of lower olefins from syngas (NATURE 2016,538,84-87)), and a stream 1 containing 1-hexene was obtained by preliminary fractionation, the composition of which is shown in tables 1-3 below. The results of calculating the composition of the obtained streams are shown in tables 1-3.

Example 1

The assembly of the apparatus and the purification of 1-hexene were carried out in this example 1 according to the scheme shown in FIG. 1: stream 1 comprising 1-hexene is cut in precut column D1, giving C6-rich fraction stream 3, removing the oxygenated compounds in an azeotropic distillation tower D2 under the condition of adding a methanol stream 5 to obtain a first mixture stream 6 and an oxygenated compound stream 7, in an etherification reaction rectifying tower R1, methanol reacts with tertiary carbon olefin in C6 hydrocarbon under the action of an etherification catalyst to generate corresponding ether and remove the ether as an etherification product stream 9, a second mixture stream 8 is conveyed to an extraction tower D3, water is used for washing and extracting to remove the methanol, the obtained refined C6 hydrocarbon stream is subjected to rectification to remove heavy components in a rectification heavy component removing tower D5 to obtain a 1-hexene-enriched stream 15, removing light components in an extractive distillation light component removing tower D6 to obtain a third mixture 18, and removing cycloolefin components in a 1-hexene purifying tower D7 to obtain a 1-hexene product stream 19.

The specific operating conditions of each unit in the process flow are as follows: light hydrocarbon fraction stream 1 in the synthesis gas direct olefin (FTO) product is pre-separated by pre-cutter D1 to obtain C6-enriched fraction stream 3. Precutting tower D1 is dividing wall type rectifying column, and this dividing wall type rectifying column is through setting up a vertical baffle in the inside of traditional rectifying column, divide into 4 parts with the rectifying column: the device comprises a partition board, a side line extraction device, a side line rectification device, a public rectification device and a public stripping device, wherein the feeding side of the partition board is a pre-rectification area, the number of tower plates of the pre-rectification area is 10, the side line extraction side of the partition board is a side line rectification area, the number of tower plates of the side line rectification area is 10, the public rectification area is arranged above the partition board, the number of tower plates of the public rectification area is 10, the public stripping area is arranged below the partition board, and the number of tower. Wherein the public rectification zone, the side-stream rectification zone and the public stripping zone form a main tower zone; the material flow 1 enters a pre-fractionating area and is fed from the 6 th tray from the top, the C5-fraction material flow 2 is extracted from the 1 st tray from the top, the C6-enriched fraction material flow 3 is extracted from the 6 th tray from the top in a side-stream rectifying area, and the C7+ fraction material flow 4 is extracted from the 10 th tray from the top in a common stripping area. The temperature of the top of the tower is controlled to be 30-35 ℃, the temperature of the bottom of the tower is controlled to be 95-100 ℃, and the pressure in the tower is 0.1 MPa.

The C6-rich fraction material flow 3 enters an azeotropic distillation tower D2, an entrainer of the azeotropic distillation tower D2 is methanol, the mass flow ratio of the entrainer to C6-rich fraction feed is 1:3, the theoretical plate number of the azeotropic distillation tower D2 is 40, the C6-rich fraction material flow 3 and the entrainer material flow 5 are respectively fed from a 25 th plate and a 2 nd plate, the reflux ratio is 2, the temperature of the top of the tower is controlled to be 46.5-47.5 ℃, the temperature of the bottom of the tower is controlled to be 73-75 ℃, and the pressure in the tower is XX. The first mixture stream 6 containing methanol and C6 hydrocarbon is obtained at the top of the tower, and the oxygen-containing compound stream 7 is obtained at the bottom of the tower.

The first mixture material flow 6 enters an etherification reaction rectifying tower R1, Amberlyst 15 etherification catalyst is adopted, the number of theoretical plates is 30, the catalyst is respectively filled on the 10 th plate, the 15 th plate and the 20 th plate, the feeding position of the first mixture material flow 6 is the 21 st plate, the reflux ratio is 3, the tower top temperature is controlled to be 46-48 ℃, the tower bottom temperature is controlled to be 100-102 ℃, and the tower internal pressure is 0.1 MPa. A second mixture stream 8 comprising C6 hydrocarbons is withdrawn overhead and an etherification product stream 9 is withdrawn bottoms.

The second mixture material flow 8 enters a methanol water washing tower D3, the number of theoretical plates is 5, the feeding positions of water 10 and the second mixture material flow 8 are respectively the 1 st block and the 5 th block from the top, the mass flow rate of the water 10 and the second mixture material flow 8 is 1:2, the operating temperature is 40 ℃, the pressure in the tower is 0.1MPa, a refined C6 hydrocarbon material flow 12 at the top of the methanol water washing tower is obtained at the top of the tower, and a methanol water solution material flow 11 is extracted at the bottom of the tower.

The methanol aqueous solution material flow 11 enters a methanol recovery tower D4, the theoretical plate number of the methanol recovery tower D4 is 40, the feeding position of the methanol aqueous solution material flow 11 is 20, the reflux ratio is 4, the tower top temperature is controlled to be 60.5-61.5 ℃, the tower bottom temperature is 100-102 ℃, the tower internal pressure is 0.1MPa, the regenerated methanol material flow is extracted from the tower top and mixed with a little supplementary fresh methanol material flow to form a methanol material flow 5, the methanol material flow is conveyed to an azeotropic distillation tower D2, the regenerated water material flow is extracted from the tower bottom and mixed with a little supplementary fresh water material flow 14 to form a water material flow 10, and the water material flow is conveyed to a water washing tower D3.

The stream 12 at the top of the methanol washing tower D4 enters a fine component heavy component removal tower D5, the theoretical plate number is 100, the feeding position of the stream 12 is the upper 50 th block, the reflux ratio is 20, the temperature at the top of the tower is controlled to be 61-62 ℃, the temperature at the bottom of the tower is 67-68 ℃, the pressure in the tower is 0.1MPa, the stream 15 rich in 1-hexene is extracted at the top of the tower, and the stream 16 with the boiling point higher than that of 1-hexene is extracted at the bottom of the tower.

The material flow 15 enters an extractive distillation light component removal tower D6, NMP (N-methyl pyrrolidone) is used as an extracting agent, the theoretical plate number of the extractive distillation light component removal tower D6 is 50, the feeding positions of an extracting agent material flow 24 and a 1-hexene-rich material flow 15 are respectively the 3 rd block and the 20 th block, the reflux ratio is 3, the mass flow ratio of the extracting agent to the 1-hexene-rich material flow is 10:1, the tower top temperature is controlled to be 57.6-58.6 ℃, the tower bottom temperature is controlled to be 112-114 ℃, the tower internal pressure is 0.1MPa, a C5-light hydrocarbon material flow 17 is extracted from the tower top, and a mixed material flow of the extracting agent and the 1-hexene-rich material flow, namely a third mixed material flow 18, is extracted from the tower bottom.

The material flow 18 enters a 1-hexene purification tower D7, NMP is used as an extracting agent, the number of theoretical plates of a 1-hexene purification tower D7 is 40, the feeding positions of an extracting agent material flow 25 and the material flow 18 are respectively the upper 3 rd block and the upper 30 th block, the reflux ratio is 3, the mass flow ratio of the extracting agent to the material flow 18 is 10:1, the temperature of the top of the tower is controlled to be 63.2-63.7 ℃, the temperature of the bottom of the tower is 197-199 ℃, the pressure in the tower is 0.1MPa, a 1-hexene product material flow 19 is extracted from the top of the tower, and a mixed material flow 20 of the extracting agent containing a small amount of cycloolefin and cycloolefin is extracted from the bottom of the tower.

The material flow 20 enters an extractant recovery tower D8, the theoretical plate number of the extractant recovery tower D8 is 30, the feeding position of the material flow 20 is the 15 th upper block, the reflux ratio is 10, the temperature of the top of the tower is controlled to be 57-58 ℃, the temperature of the bottom of the tower is controlled to be 203-205 ℃, the pressure in the tower is 0.1MPa, a cycloolefin material flow 21 is extracted from the top of the tower, a regenerated extractant material flow 22 is obtained from the bottom of the tower, the material flow is separated as required after being mixed with a little supplementary fresh extractant material flow 23 and then enters an extractive distillation light component removal tower D6 and a 1-hexene purification tower D7 respectively.

According to the above-mentioned procedures and conditions, 1-hexene with a purity of 98.6% was isolated with a recovery of 1-hexene of 90%, and the composition data of the various streams in the separation scheme are shown in Table 1.

TABLE 1 data (mass fraction) of each material flow in example 1

Logistics	1	3	6	7	8	9	12	15	16	17	18	19	20	21
															C6 fraction below	0.261	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
4-methyl-1-Pentene and pentene composition	0.015	0.034	0.029	0.000	0.031	0.000	0.040	0.041	0.000	0.225	0.000	0.003	0.000	0.000
															3-methyl-1-pentene	0.015	0.034	0.029	0.000	0.031	0.000	0.040	0.041	0.000	0.218	0.000	0.005	0.000	0.000
3-methylpentane	0.023	0.054	0.046	0.000	0.049	0.000	0.064	0.066	0.000	0.384	0.000	0.000	0.000	0.000
															2, 3-dimethyl-1-butane Alkene(s)	0.003	0.007	0.006	0.000	0.006	0.000	0.008	0.009	0.000	0.049	0.000	0.000	0.000	0.000
2-methyl-1-pentene	0.0023	0.053	0.045	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
															1-hexene	0.0299	0.687	0.584	0.007	0.628	0.002	0.806	0.834	0.067	0.122	0.076	0.986	0.002	0.922
N-hexane	0.009	0.020	0.017	0.000	0.018	0.001	0.024	0.000	0.651	0.002	0.000	0.000	0.000	0.000
															2-ethyl-1-butene	0.003	0.007	0.006	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
3-hexene	0.003	0.008	0.007	0.000	0.007	0.000	0.009	0.001	0.248	0.000	0.000	0.001	0.000	0.001
															3-firstCyclopentenes	0.003	0.006	0.005	0.000	0.005	0.000	0.007	0.007	0.001	0.000	0.001	0.005	0.000	0.064
2-methyl-2-pentene	0.0004	0.001	0.001	0.000	0.001	0.000	0.001	0.000	0.032	0.000	0.000	0.000	0.000	0.000
															3-methyl-1-hexene	0.0004	0.001	0.000	0.008	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Fraction of C6 or above	0.304	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
															Methanol	0.000	0.000	0.226	0.280	0.222	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Oxygen-containing compound	0.038	0.088	0.000	0.704	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
															Ether compounds	0.000	0.000	0.000	0.000	0.000	0.998	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Water (W)	0.000	0.000	0.000	0.000	0.000	0.000	0.001	0.001	0.000	0.000	0.000	0.000	0.000	0.008
															NMP	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.923	0.000	0.997	0.006

Example 2

The assembly of the apparatus and the purification of 1-hexene were carried out in this example 2 according to the scheme shown in FIG. 1: stream 1 comprising 1-hexene is cut in precut column D1, giving C6-rich fraction stream 3, removing the oxygenated compounds in an azeotropic distillation tower D2 under the condition of adding a methanol stream 5 to obtain a first mixture stream 6 and an oxygenated compound stream 7, in an etherification reaction rectifying tower R1, methanol reacts with tertiary carbon olefin in C6 hydrocarbon under the action of an etherification catalyst to generate corresponding ether and remove the ether as an etherification product stream 9, a second mixture stream 8 is conveyed to an extraction tower D3, water is used for washing and extracting to remove the methanol, the obtained refined C6 hydrocarbon stream is subjected to rectification to remove heavy components in a rectification heavy component removing tower D5 to obtain a 1-hexene-enriched stream 15, removing light components in an extractive distillation light component removing tower D6 to obtain a third mixture 18, and removing cycloolefin components in a 1-hexene purifying tower D7 to obtain a 1-hexene product stream 19.

The C6-rich fraction material flow 3 enters an azeotropic distillation tower D2, an entrainer of the azeotropic distillation tower D2 is methanol, the mass flow ratio of the entrainer to C6-rich fraction feed is 1:3, the theoretical plate number of the azeotropic distillation tower D2 is 40, the C6-rich fraction material flow 3 and the entrainer material flow 5 are respectively fed from a 25 th plate and a 2 nd plate, the reflux ratio is 2, the temperature of the top of the tower is controlled to be 46.5-47.5 ℃, the temperature of the bottom of the tower is controlled to be 73-75 ℃, and the pressure in the tower is 0.1 MPa. The first mixture stream 6 containing methanol and C6 hydrocarbon is obtained at the top of the tower, and the oxygen-containing compound stream 7 is obtained at the bottom of the tower.

The material flow 15 enters an extractive distillation light component removal tower D6, N-formyl morpholine (NFM) is used as an extracting agent, the theoretical plate number of an extractive distillation light component removal tower D6 is 60, the feeding positions of an extracting agent material flow 24 and a 1-hexene-rich material flow 15 are respectively the 3 rd block and the 30 th block, the reflux ratio is 10, the mass flow ratio of the extracting agent to the 1-hexene-rich material flow is 10:1, the tower top temperature is controlled to be 57.5-58.5 ℃, the tower bottom temperature is 88-90 ℃, the tower internal pressure is 0.1MPa, a C5-light hydrocarbon material flow 17 is extracted from the tower top, and a mixed material flow of the extracting agent and the 1-hexene-rich material flow, namely a third mixed material flow 18, is extracted from the tower bottom.

The material flow 18 enters a 1-hexene purification tower D7, NFM is used as an extracting agent, the theoretical plate number of the 1-hexene purification tower D7 is 40, the feeding positions of an extracting agent material flow 25 and the material flow 18 are respectively the upper 3 rd block and the upper 30 th block, the reflux ratio is 3, the mass flow ratio of the extracting agent to the material flow 18 is 10:1, the tower top temperature is controlled to be 63.2-63.7 ℃, the tower bottom temperature is 217-219 ℃, the tower internal pressure is 0.1MPa, a 1-hexene product material flow 19 is extracted from the tower top, and the extracting agent containing a small amount of cycloolefin and a cycloolefin mixed material flow 20 are extracted from the tower bottom.

The material flow 20 enters an extractant recovery tower D8, the theoretical plate number of the extractant recovery tower D8 is 30, the feeding position of the material flow 20 is the 15 th upper block, the reflux ratio is 10, the temperature of the top of the tower is controlled to be 54-55 ℃, the temperature of the bottom of the tower is 239-241 ℃, the pressure in the tower is 0.1MPa, a cycloolefin material flow 21 is collected from the top of the tower, a regenerated extractant material flow 22 is obtained from the bottom of the tower, the material flow is separated as

extractant materials

24 and 25 after being mixed with a little supplementary fresh extractant material flow 23 as required, and then the separated material flow enters an extractive distillation light component removal tower D6 and a 1-hexene purification tower D7 respectively.

According to the above-mentioned procedures and conditions, 1-hexene with a purity of 99.2% was isolated with a recovery of 1-hexene of 90%, and the composition data of the various streams in the separation scheme are shown in Table 2.

Table 2 data (mass fraction) of each material flow in example 2

Example 3

The assembly of the apparatus and the purification of 1-hexene were carried out in this example 3 according to the scheme shown in FIG. 1: stream 1 comprising 1-hexene is cut in precut column D1, giving C6-rich fraction stream 3, removing the oxygenated compounds in an azeotropic distillation tower D2 under the condition of adding a methanol stream 5 to obtain a first mixture stream 6 and an oxygenated compound stream 7, in an etherification reaction rectifying tower R1, methanol reacts with tertiary carbon olefin in C6 hydrocarbon under the action of an etherification catalyst to generate corresponding ether and remove the ether as an etherification product stream 9, a second mixture stream 8 is conveyed to an extraction tower D3, water is used for washing and extracting to remove the methanol, the obtained refined C6 hydrocarbon stream is subjected to rectification to remove heavy components in a rectification heavy component removing tower D5 to obtain a 1-hexene-enriched stream 15, removing light components in an extractive distillation light component removing tower D6 to obtain a third mixture 18, and removing cycloolefin components in a 1-hexene purifying tower D7 to obtain a 1-hexene product stream 19.

The material flow 15 enters an extractive distillation light component removal tower D6, Dimethylformamide (DMF) is used as an extracting agent, the number of theoretical plates of an extractive distillation light component removal tower D6 is 50, the feeding positions of an extracting agent material flow 24 and a 1-hexene-rich material flow 15 are respectively the 3 rd block and the 20 th block, the reflux ratio is 8, the mass flow ratio of the extracting agent to the 1-hexene-rich material flow is 10:1, the temperature of the top of the tower is controlled to be 57.9-58.9 ℃, the temperature of the bottom of the tower is controlled to be 93-95 ℃, the pressure in the tower is 0.1MPa, a C5-light hydrocarbon material flow 17 is extracted from the top of the tower, and a mixed material flow of the extracting agent and the 1-hexene-rich material flow, namely a third mixed material flow 18, is extracted.

The material flow 18 enters a 1-hexene purification tower D7, DMF is used as an extracting agent, the number of theoretical plates of a 1-hexene purification tower D7 is 50, the feeding positions of an extracting agent material flow 25 and the material flow 18 are respectively the 8 th block and the 30 th block, the reflux ratio is 5, the mass flow ratio of the extracting agent to the material flow 18 is 10:1, the temperature of the top of the tower is controlled to be 63.2-63.7 ℃, the temperature of the bottom of the tower is controlled to be 147-149 ℃, the pressure in the tower is 0.1MPa, a 1-hexene product material flow 19 is extracted from the top of the tower, and a mixed material flow 20 of the extracting agent containing a small amount of cycloolefin and cycloolefin is extracted from the bottom of the tower.

The material flow 20 enters an extractant recovery tower D8, the theoretical plate number of the extractant recovery tower D8 is 30, the feeding position of the material flow 20 is the 15 th upper block, the reflux ratio is 10, the temperature of the top of the tower is controlled to be 65-66 ℃, the temperature of the bottom of the tower is 151-153 ℃, the pressure in the tower is 0.1MPa, a cycloolefin material flow 21 is extracted from the top of the tower, a regenerated extractant material flow 22 is obtained from the bottom of the tower, the material flow is separated as

extractant materials

According to the above procedures and conditions, 1-hexene with a purity of 98.7% was isolated with a recovery of 1-hexene of 90%, and the composition data of the various streams in the separation scheme are shown in Table 3.

Table 3 data (mass fraction) of each material flow in example 3

Logistics	1	3	6	7	8	9	12	15	16	17	18	19	20	21
															C6 fraction below	0.261	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
4-methyl-1-pentene	0.015	0.034	0.029	0.000	0.031	0.000	0.040	0.041	0.000	0.226	0.000	0.003	0.000	0.000
															3-methyl-1-pentene	0.015	0.034	0.029	0.000	0.031	0.000	0.040	0.041	0.000	0.219	0.000	0.005	0.000	0.000
3-methylpentane	0.023	0.054	0.046	0.000	0.049	0.000	0.064	0.066	0.000	0.384	0.000	0.000	0.000	0.000
															2, 3-dimethyl-1-butane Alkene(s)	0.003	0.007	0.006	0.000	0.006	0.000	0.008	0.009	0.000	0.049	0.000	0.000	0.000	0.000
2-methyl-1-pentene	0.0023	0.053	0.045	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
															1-hexene	0.0299	0.687	0.584	0.007	0.628	0.002	0.806	0.834	0.067	0.109	0.076	0.987	0.002	0.845
N-hexane	0.009	0.020	0.017	0.000	0.018	0.001	0.024	0.000	0.651	0.002	0.000	0.000	0.000	0.000
															2-ethyl-1-butene	0.003	0.007	0.006	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
3-hexene	0.003	0.008	0.007	0.000	0.007	0.000	0.009	0.001	0.248	0.000	0.000	0.001	0.000	0.001
															3-methylcyclopentene	0.003	0.006	0.005	0.000	0.005	0.000	0.007	0.007	0.001	0.000	0.001	0.005	0.000	0.052
2-methyl-2-pentene	0.0004	0.001	0.001	0.000	0.001	0.000	0.001	0.000	0.032	0.000	0.000	0.000	0.000	0.000
															3-methyl-1-hexene	0.0004	0.001	0.000	0.008	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Fraction of C6 or above	0.304	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
															Methanol	0.000	0.000	0.226	0.280	0.222	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Oxygen-containing compound	0.038	0.088	0.000	0.704	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
															Ether compounds	0.000	0.000	0.000	0.000	0.000	0.998	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Water (W)	0.000	0.000	0.000	0.000	0.000	0.000	0.001	0.001	0.000	0.000	0.000	0.000	0.000	0.000
															DMF	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.012	0.922	0.000	0.997	0.101

Claims

1. A method of purifying 1-hexene, comprising:

step (i): providing a stream comprising 1-hexene;

2. The method of claim 1, further comprising at least one of the following steps (a) and (b):

step (a) of recovering said C1-C4 alcohol after step (v);

3. The method according to claim 1 or 2, wherein step (ii) is carried out in a pre-cut tower provided with vertical partitions therein to divide the pre-cut tower into 4 sections: one side of the baffle for feeding is a pre-fractionating area, one side of the baffle for taking out is a side-line rectifying area, a public rectifying area is arranged above the baffle, and a public stripping area is arranged below the baffle; the number of theoretical plates in the pre-distillation zone is 5-15, the number of theoretical plates in the lateral line distillation zone is 5-15, the number of theoretical plates in the public distillation zone is 5-15, and the number of theoretical plates in the public stripping zone is 5-15; feeding the stream containing 1-hexene from the step (i) from the tower plates 2-15 from the top of the pre-fractionation zone, wherein the extraction position of the C6-rich fraction stream is between the tower plates 2-15 from the top of the side rectification zone, the reflux ratio is 1-10, the tower top temperature is 20-40 ℃, and the tower bottom temperature is 100-150 ℃.

4. The process of claim 1 or 2, wherein the azeotroping agent in step (iii) comprises at least one C1-C4 alcohol selected from the group consisting of: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 2-methyl-1, 3-propanediol, 3-methyl-1, 2-propanediol, 1,2, 3-propanetriol, 1,2, 3-butanetriol, 1,2, 4-butanetriol, 2-methyl-1, 2, 3-propanetriol, 1,2,3, 4-butanetetraol, or any mixture thereof; and/or

The step (iii) is carried out in an azeotropic distillation tower, the number of theoretical plates of the azeotropic distillation tower is 20-40, the feeding position of the C6-enriched fraction material flow is 3-35 from the top, the feeding position of the C1-C4 alcohol is 1-10 from the top, the reflux ratio is 1-10, the temperature of the tower top is 40-60 ℃, and the temperature of the tower kettle is 50-100 ℃; and/or

Wherein the volumetric flow ratio of the C1-C4 alcohol to the C6-rich fraction stream is from 0.1:1 to 1.5: 1.

5. The process according to claim 1 or 2, wherein step (iv) is carried out in a reactive distillation column having a theoretical plate number of 20 to 40, a reflux ratio of 1 to 10, a feed position of the first mixture stream of 10 to 35 from the top, an overhead temperature of 40 to 70 ℃ and a still temperature of 80 to 120 ℃; and/or

Step (iv) is carried out in the presence of an etherification catalyst, which is a strongly acidic cationic resin; and/or

Wherein the C1-C4 alcohol used in step (iv) is selected from at least one of the following: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 2-methyl-1, 3-propanediol, 3-methyl-1, 2-propanediol, 1,2, 3-propanetriol, 1,2, 3-butanetriol, 1,2, 4-butanetriol, 2-methyl-1, 2, 3-propanetriol, 1,2,3, 4-butanetetraol, or any mixture thereof.

6. The process of claim 1 or 2, wherein step (v) is carried out in an extraction column, the first extractant is water, the number of theoretical plates of the extraction column is 3 to 10, the feed position of water is the first plate from the top of the extraction column, the feed position of the second mixture stream is the lowest plate from the top of the extraction column, the water-oil ratio is 0.4 to 4, and the operating temperature is 5 to 45 ℃; and/or

And (vi) the step is carried out in a fine heavy component removal tower, wherein the fine heavy component removal tower is an atmospheric pressure rectifying tower, the theoretical plate number of the atmospheric pressure rectifying tower is 60-160, the reflux ratio is 10-40, the feeding position of a fine C6 hydrocarbon material flow is 10-50 plates from top, the temperature of the top of the tower is 58-68 ℃, and the temperature of the bottom of the tower is 60-90 ℃.

7. The method of claim 1 or 2, wherein the step (vii) is carried out in an extractive distillation light component removal tower, the extractive distillation light component removal tower is an atmospheric distillation tower, the theoretical plate number of the tower is 20-80, the reflux ratio is 1-20, the feeding position of the 1-hexene-rich material stream is 5-75 from the top, the feeding position of the second extractant is 2-10 from the top, the tower top temperature is 55-65 ℃, and the tower bottom temperature is 60-160 ℃;

wherein the second extractant is selected from at least one of: n-methylpyrrolidone, N-formylmorpholine, N-dimethylformamide;

wherein the feed volume ratio of the second extractant to the 1-hexene rich stream is from 1:1 to 20: 1.

8. The process of claim 1 or 2, wherein step (viii) is carried out in a purification column, which is an atmospheric distillation column, having a theoretical plate number of 20 to 80, a reflux ratio of 1 to 20, a feed position of the third mixture stream of 5 to 75 from the top, a feed position of the third extractant of 2 to 10 from the top, a feed volume ratio of the third extractant to the third mixture stream of 0.5:1 to 1.5:1, an overhead temperature of 58 to 68 ℃, and a column bottom temperature of 120 to 200 ℃;

wherein the third extractant is selected from at least one of: n-methylpyrrolidone, N-formylmorpholine and N, N-dimethylformamide.

9. An apparatus for purifying 1-hexene, comprising, in order from upstream to downstream: the device comprises a pre-cutting tower, an azeotropic distillation tower, a reactive distillation tower, an extraction tower, a component heavy component removal tower, an extractive distillation light component removal tower and a 1-hexene purification tower.

10. The apparatus of claim 9, further comprising: