阅读说明：本技术 一种可在线监控的直链烯烃生产方法 (Linear olefin production method capable of being monitored on line ) 是由 李俊诚 钱震 张晓龙 武靖为 高源� 邬学霆 陈浩庭 于 2019-03-04 设计创作，主要内容包括：本发明涉及一种可在线监控的直链烯烃生产方法。具体包括：以煤基费托合成油为原料,经过脱酸、馏分切割、脱含氧化合物、烷烯分离和异构体分离步骤得到聚合级烯烃产品,烯烃碳数N的范围为4-18；在生产过程中,采用在线中红外光谱仪实时测定原料中烯烃、烷烃及炔烃的含量,并根据检测结果实时调整各工艺步骤的操作条件。本发明可以高效、能耗低、响应速度快、产品纯度高的生产直链烯烃。(The invention relates to a linear olefin production method capable of being monitored on line. The method specifically comprises the following steps: taking coal-based Fischer-Tropsch synthetic oil as a raw material, and performing deacidification, fraction cutting, oxygen-containing compound removal, alkane-alkene separation and isomer separation to obtain a polymer grade alkene product, wherein the carbon number N of the alkene is 4-18; in the production process, the content of olefin, alkane and alkyne in the raw material is measured in real time by adopting an online mid-infrared spectrometer, and the operating conditions of each process step are adjusted in real time according to the detection result. The invention can produce the linear chain olefin with high efficiency, low energy consumption, high response speed and high product purity.)

1. A linear olefin production process that can be monitored on-line, characterized by: taking coal-based Fischer-Tropsch synthetic oil as a raw material, and performing deacidification, fraction cutting, oxygen-containing compound removal, alkane-alkene separation and isomer separation to obtain a polymer grade alkene product, wherein the carbon number N of the alkene is 4-18; in the production process, the content of olefin, alkane and alkyne in the raw material is measured in real time by adopting an online mid-infrared spectrometer, and the operating conditions of each process step are adjusted in real time according to the detection result.

2. The on-line monitorable linear olefin production process according to claim 1 and wherein: and the contents of olefin, alkane and alkyne in the product and the intermediate product are also measured in real time by adopting an online mid-infrared spectrometer.

3. The on-line monitorable linear olefin production process according to claim 1 or 2 wherein: a branch with a test sample pool is arranged on a material pipeline to be monitored on line, and an on-line mid-infrared spectrometer is adopted to detect materials in the sample pool.

4. The on-line monitorable linear olefin production process according to claim 3 and wherein: an inlet pipe and an outlet pipe which are led out to enter the sample cell respectively before and after a regulating valve with pressure difference in a material pipeline; the pressure in the cell was regulated by a valve to be below 69bar and the temperature of the feed to the cell was not higher than 200 ℃.

5. The on-line monitorable linear olefin production process according to any one of claims 1 to 4 wherein: the mid-infrared spectrometer adopts an optical fiber probe type measurement, and the spectral range is 4000-650cm^-1Resolution of 4cm^-1。

6. The on-line monitorable linear olefin production process according to any one of claims 1 to 5 wherein: the detection steps of the intermediate infrared spectrometer are as follows:

(1) calibration model establishment

Selecting various Fischer-Tropsch synthesis oil samples, and determining the contents of olefin, alkane and alkyne in the Fischer-Tropsch synthesis oil samples by adopting a gas chromatography; and then, performing mid-infrared spectrum scanning on each sample through a sample cell, and selecting C-C bond at 3100-3010 cm^-1Is a characteristic spectral region; the C-C bond is 2975-2800 cm^-1Is a characteristic spectral region; the C ≡ C bond is 3300-2150 cm^-1For the characteristic spectral region, the response value of the characteristic spectral region is related to the contents of alkene, alkane and alkyne in the sample determined by gas chromatography, and least square method of stoichiometry is adopted for dividingRespectively establishing a correction model;

(2) determination of unknown sample content

Performing mid-infrared spectrum scanning on an unknown sample under the same test condition as that of the calibration model, wherein the mid-infrared spectrum scanning is respectively 3100-3010 cm^-1、2975～2800cm^-1、3300～2150cm^-1And substituting the response values of the spectral regions into the corresponding correction models to obtain the contents of the olefin, the alkane and the alkyne in the unknown sample.

7. The on-line monitorable linear olefin production process according to any one of claims 1 to 6 wherein: the method comprises the following steps of deacidification, fraction cutting, oxygen-containing compound removal, alkane-alkene separation and isomer separation:

(1) deacidifying: performing alkali washing by using an alkali washing kettle; adding distillate oil and a proper amount of potassium carbonate solution into a neutralization reactor, stirring, standing for layering after complete reaction, transferring an emulsion phase and a water phase to a standing phase-splitting tank, washing with water, standing for layering, and sending the near-neutral distillate oil to a subsequent working section;

(2) and (3) cutting fractions: the nearly neutral distillate oil after deacidification treatment enters a light component removal tower, the component with the carbon number less than N is separated from the top of the light component removal tower, and the component at the bottom of the tower enters a heavy component removal tower; separating the component with carbon number greater than N from the bottom of the heavy component removing tower, and separating the component with carbon number of N from the top of the heavy component removing tower;

(3) removing oxygen-containing compounds: introducing the component with the carbon number of N obtained in the step (2) into an extraction and rectification tower, and reversely contacting with an extracting agent to remove oxygen-containing compounds and control the content of the oxygen-containing compounds to be below 1000 ppm; the oil product is preheated to 30-50 ℃ in a preheating furnace and then enters an adsorption tower provided with a molecular sieve to further adsorb and separate the oxygen-containing compound, remove the oxygen-containing compound and control the content of the oxygen-containing compound to be below 1 ppm;

(4) and (3) alkane and alkene separation: treating the product obtained in the step (3) by adopting a first simulated moving bed, separating alkane and alkene, wherein the operation temperature is 50-100 ℃, the operation pressure is 0.4-0.6Mpa, and the content of the obtained alkene component is more than 99.9 wt%;

(5) isomer separation: and (3) treating the product obtained in the step (4) by adopting a second simulated moving bed to separate linear chain olefin, wherein the operation parameters are that the operation temperature is 50-100 ℃, the operation pressure is 0.4-0.6Mpa, and the linear chain olefin component content in the obtained product is more than 99.7 wt% through adsorption drying treatment, so that the product is a polymerization grade olefin product.

8. The on-line monitorable linear olefin production process according to claim 7 and wherein: the extractant used in the step of removing the oxygen-containing compounds is ethylene glycol, dimethyl phthalate or a mixture thereof.

9. The on-line monitorable linear olefin production process according to claim 7 and wherein: in the first simulated moving bed process in the step (4), the operation temperature is 90-100 ℃, the operation pressure is 0.45-0.55Mpa, the simulated moving bed filling agent is a 5A molecular sieve and/or a modified 5A molecular sieve, and the agent-oil ratio is 0.5-2: 1 (mass ratio).

10. The on-line monitorable linear olefin production process according to claim 7 and wherein: in the second simulated moving bed process in the step (5), the operation temperature is 90-100 ℃, the operation pressure is 0.45-0.55Mpa, the simulated moving bed filling agent is 13X molecular sieve and/or modified 13X molecular sieve, and the agent-oil ratio is 0.5-2: 1 (mass ratio).

Technical Field

The invention relates to a linear chain olefin production method capable of being monitored on line, in particular to a production method for measuring the contents of olefin, alkane and alkyne in real time and correspondingly adjusting the operating conditions.

Background

The Fischer-Tropsch synthetic oil product contains a large amount of valuable chemical raw materials, namely olefin, which is a key raw material for producing other fine chemical products and has extremely important influence on downstream industries.

At present, the subsequent processing method for Fischer-Tropsch synthetic oil products at home and abroad mainly focuses on the aspects of distillation and rectification.

Patents US7217852 and US7294253 propose a process for the distillation of products of fischer-tropsch synthesis and an intermediate distillate obtained by distillation, which contains branches such as methyl, ethyl, propyl, etc., and the C9-C16 components account for more than 90% of the total distillate, which is the main component constituting the diesel oil and which has good low-temperature fluidity.

AU199951882, US6855248 and WO0011113 propose a process for the distillation of a waxy fischer-tropsch synthesis oil by cutting a fischer-tropsch derivative comprising heavy hydrocarbons, light hydrocarbons, hydrocarbons of intermediate carbon number by passing the fischer-tropsch derivative through a distillation column, the carbon number distribution of the product coming out of the column: light hydrocarbon C23-, middle carbon number hydrocarbon C20-C38, heavy hydrocarbon C30+ to obtain useful wax product.

EP1835011 proposes a method for the distillation treatment of a fischer-tropsch synthesis crude and the resulting middle distillate, the main process being to cut the FTS crude into naphtha and middle distillate. The south Africa SASOL company develops a combined process route of alkaline washing, etherification, rectification and extraction in 1994 to realize the preparation of polymerization-grade 1-hexene and 1-octene. However, the process has complicated route and high operation energy consumption, so that the investment and operation cost is very high, and the technology can only separate C6 and C8 components, but cannot separate high-carbon-number components.

In document CN104370678, a light distillate oil of carbon five synthesized by fischer-tropsch is used as a raw material, the raw material is extracted and rectified, an extracting agent is N, N-dimethylformamide, and a 1-pentene enriched material obtained from the top of an extractive rectification tower is further purified by precision rectification to obtain a 1-pentene product. The olefin obtained by the method has single carbon number, and the basic method used is extraction and rectification.

In addition, the south Africa SASOL company develops a combined process route of alkaline washing, etherification, rectification and extraction in 1994 to realize the preparation of polymerization-grade 1-hexene and 1-octene. However, the process has complicated route and high operation energy consumption, so that the investment and operation cost is very high, and the technology can only separate C6 and C8 components, but cannot separate high-carbon-number components.

The separation processes in the technical documents all adopt the traditional extractive distillation process, and because the difference between the boiling points of the linear chain olefin and the isomeric olefin is very small, the separation cost by adopting the extractive distillation process is very high, the using amount of the solvent is large, the recovery is difficult, and the requirements of the current social development are not met. Although current technology is capable of separating liquid olefins from liquid alkanes, there is still a need to provide more improved processes for separating olefins from alkanes.

In addition, in the process of production, the precision of process control has a great influence on the quality of products, so that the online real-time detection of material composition is very important.

Patent CN 103760131A discloses a gasoline oil attribute real-time prediction method based on near infrared spectrum detection. The method requires scanning near infrared spectrograms of gasoline components C4-C12 and establishing a model to calculate the octane number, but cannot directly measure the contents of olefin, alkane and alkyne.

Patent CN 104122235a discloses a device and a method for detecting olefin gas. The method can only detect whether various olefins leak in the device area, but the gas detection of the olefins needs gaseous olefins or detects the gasified olefins, the detection process is complicated, the pretreatment is complex, and quantitative detection cannot be formed.

The Lioshi (in-line infrared spectroscopy for detecting olefin and aromatic hydrocarbon (benzene) in gasoline, fine petrochemical engineering, No. 4, 7 months in 2001) provides a method for detecting olefin and aromatic hydrocarbon in gasoline by using in-line infrared spectroscopy. The method adopts near infrared spectrum to perform online detection on gasoline in a pipeline, the application range of a detection sample is small, and the repeatability and reproducibility deviation of olefin detection are large.

Disclosure of Invention

In order to solve the technical problems, the invention provides the linear chain olefin production method which has high efficiency, low energy consumption, high response speed and high product purity and can be monitored on line.

The adopted technical scheme is as follows:

taking coal-based Fischer-Tropsch synthetic oil as a raw material, and performing deacidification, fraction cutting, oxygen-containing compound removal, alkane-alkene separation and isomer separation to obtain a polymer grade alkene product, wherein the carbon number N of the alkene is 4-18; in the production process, the content of olefin, alkane and alkyne in the raw material is measured in real time by adopting an online mid-infrared spectrometer, and the operating conditions of each process step are adjusted in real time according to the detection result.

And the contents of olefin, alkane and alkyne in the product and the intermediate product are also measured in real time by adopting an online mid-infrared spectrometer.

A branch with a test sample pool is arranged on a material pipeline to be monitored on line, and an on-line mid-infrared spectrometer is adopted to detect materials in the sample pool.

An inlet pipe and an outlet pipe which are led out to enter the sample cell respectively before and after a regulating valve with pressure difference in a material pipeline; the pressure in the cell was regulated by a valve to be below 69bar and the temperature of the feed to the cell was not higher than 200 ℃.

The sample cell is a branch flow sample cell, the mid-infrared spectrometer adopts an optical fiber probe type measurement, and the spectral range is 4000-^-1Resolution of 4cm^-1。

Preferably, the spectral scanning is performed by a fiber optic probe, and the spectral peak height at the characteristic wavelength is obtained by processing the spectral scanning by an instrument software workstation.

The detection steps of the intermediate infrared spectrometer are as follows:

(1) calibration model establishment

Selecting various Fischer-Tropsch synthesis oil samples, and determining the contents of olefin, alkane and alkyne in the Fischer-Tropsch synthesis oil samples by adopting a gas chromatography; then, the samples are subjected to mid-infrared spectrum scanning through a sample cell, and C-C bond is selected to be 3100-3010 cm^-1Is a characteristic spectral region; the C-C bond is 2975-2800 cm^-1Is a characteristic spectral region; the C ≡ C bond is 3300-2150 cm^-1For the characteristic spectral region, the response value of the characteristic spectral region is compared with the alkene, alkane and alkyne of the sample by gas chromatographyCorrelating the content of the hydrocarbons, and respectively establishing a correction model by adopting a least square method of a stoichiometric method;

(2) determination of unknown sample content

Performing mid-infrared spectrum scanning on an unknown sample under the same test condition as that of the calibration model, wherein the mid-infrared spectrum scanning is respectively 3100-3010 cm^-1、2975～2800cm^-1、3300～2150cm^-1And substituting the response values of the spectral regions into the corresponding correction models to obtain the contents of the olefin, the alkane and the alkyne in the unknown sample.

Preferably, the step of establishing the correction model by using the least square method of the chemometric method comprises the following steps:

(1) assuming that the spectral peak height y of an olefin (or an alkane or an alkyne) at a characteristic wavelength is in the following relation with the concentration value x of the olefin (or the alkane or the alkyne), wherein y is ax + b, a is a coefficient and b is an intercept.

(2) There is a correspondence for each set of data (xi, yi).

(3) Error e ═ yi- (axi + b)

(4) When in use

The minimum degree of fitting is the highest, i.e.Minimum, S stands for standard deviation

(5) Separately solving a first order partial derivative

(6) Let the above two formulae equal 0, respectively, have

(7) Finally obtaining the final product

(8) Substituting the values x and y of each sample to obtain a value a and a value b, and further obtaining a linear relation equation.

The method comprises the following steps of deacidification, fraction cutting, oxygen-containing compound removal, alkane-alkene separation and isomer separation:

(1) deacidifying: performing alkali washing by using an alkali washing kettle; adding distillate oil and a proper amount of potassium carbonate solution into a neutralization reactor, stirring, standing for layering after complete reaction, transferring an emulsion phase and a water phase to a standing phase-splitting tank, washing with water, standing for layering, and sending the near-neutral distillate oil to a subsequent working section;

(2) and (3) cutting fractions: the nearly neutral distillate oil after deacidification treatment enters a light component removal tower, the component with the carbon number less than N is separated from the top of the light component removal tower, and the component at the bottom of the tower enters a heavy component removal tower; separating the component with carbon number greater than N from the bottom of the heavy component removing tower, and separating the component with carbon number of N from the top of the heavy component removing tower;

(3) removing oxygen-containing compounds: introducing the component with the carbon number of N obtained in the step (2) into an extraction and rectification tower, and reversely contacting with an extracting agent to remove oxygen-containing compounds and control the content of the oxygen-containing compounds to be below 1000 ppm; the oil product is preheated to 30-50 ℃ in a preheating furnace and then enters an adsorption tower provided with a molecular sieve to further adsorb and separate the oxygen-containing compound, remove the oxygen-containing compound and control the content of the oxygen-containing compound to be below 1 ppm;

(4) and (3) alkane and alkene separation: treating the product obtained in the step (3) by adopting a first simulated moving bed, separating alkane and alkene, wherein the operation temperature is 50-100 ℃, the operation pressure is 0.4-0.6Mpa, and the content of the obtained alkene component is more than 99.9 wt%;

(5) isomer separation: and (3) treating the product obtained in the step (4) by adopting a second simulated moving bed to separate linear chain olefin, wherein the operation parameters are that the operation temperature is 50-100 ℃, the operation pressure is 0.4-0.6Mpa, and the linear chain olefin component content in the obtained product is more than 99.7 wt% through adsorption drying treatment, so that the product is a polymerization grade olefin product.

The simulated moving bed equipment used in the invention is as follows:

comprises an adsorption bed, a raw material feeding system, a desorbent feeding system, a circulating system, a liquid pumping system, a raffinate pumping system, a program control valve group and an automatic control system; wherein, the adsorption bed comprises a plurality of adsorption columns which are divided into an adsorption area, a purification area, a desorption area and a buffer area;

the upper end of each adsorption column is provided with a raw material feed valve, a desorbent feed valve and a circulating liquid feed valve;

the lower end of each adsorption column is provided with a raffinate discharge valve and an extract discharge valve;

a one-way valve is arranged between every two adjacent adsorption columns;

the raw material feeding system is connected with a raw material feeding valve of each adsorption column;

the desorbent feed system is connected with a desorbent feed valve of each adsorption column;

the circulating system comprises a circulating pump, and is connected with a circulating liquid feeding valve of each adsorption column through the circulating pump;

the extract system is connected with an extract discharge valve of each adsorption column;

the raffinate system is connected with a raffinate discharge valve of each adsorption column;

all valves form a program control valve group, the program control valve group is connected with an automatic control system, and the automatic control system can control the opening and closing state of each valve in the program control valve group.

Further, the extracting agent used in the step of removing the oxygen compounds is ethylene glycol, dimethyl phthalate or a mixture thereof.

Further, in the first simulated moving bed process in the step (4), the operation temperature is 90-100 ℃, the operation pressure is 0.45-0.55Mpa, the simulated moving bed filling agent is a 5A molecular sieve and/or a modified 5A molecular sieve, and the agent-oil ratio is 0.5-2: 1 (mass ratio).

Further, in the second simulated moving bed process in the step (5), the operation temperature is 90-100 ℃, the operation pressure is 0.45-0.55Mpa, the simulated moving bed filling agent is 13X molecular sieve and/or modified 13X molecular sieve, and the agent-oil ratio is 0.5-2: 1 (mass ratio).

Further, the second simulated moving bed process selected in the step (5) has the operation temperature of 90-100 ℃, the operation pressure of 0.45-0.55Mpa, the simulated moving bed filling agent is 13X molecular sieve and/or modified 13X molecular sieve, and the agent-oil ratio is 0.5-2: 1 (mass ratio).

Further, the target olefin carbon number N is in the range of 6 to 14, preferably 8 to 12, and more preferably 8 to 10.

Further, the addition amount of the potassium carbonate in the step (1) is 200-220mgK₂CO₃Distillate oil of 100 ml.

Further, the oxygenate removal step (3) may be free of extractive distillation steps.

Further, the oxygenate removal step, the alkane-alkene separation step, and the isomer separation step include a solvent regeneration step.

Furthermore, the coal-based Fischer-Tropsch synthetic oil contains 73 to 75 weight percent of olefin, 22 to 25 weight percent of alkane and 3 to 5 weight percent of oxide

Further, the adsorbent in the first simulated moving bed is a 5A molecular sieve and/or a modified 5A molecular sieve, and the adsorbent in the second simulated moving bed is a 13X molecular sieve and/or a modified 13X molecular sieve.

Advantageous effects

(1) In the alkane and alkene mixture, the adsorption performance of alkane and alkene on a specific adsorbent has certain difference, the method of the invention separates the mixed components by utilizing the difference of the adsorption performance of different substances, and the traditional rectification and extraction processes are not separated by utilizing the difference of boiling points. Compared with the traditional rectification and extraction process, the invention adopts the mode of connecting two stages of simulated moving beds in series for separation, and the obtained product has higher purity, higher yield, lower energy consumption and about 15 percent of the production cost of the traditional process. Meanwhile, the carbon number distribution of olefin products obtained based on the simulated moving bed technology is wide, and the olefin products can be produced from C4 to C18 (including odd carbon), which cannot be achieved by the traditional rectification and extraction technology.

(2) The online detection in the olefin production process is realized, the online detection is more convenient than the offline detection, and the accuracy of the measurement result is credible; the operation conditions of all the process steps are adjusted in real time according to the online detection result, so that the quick response of the process operation is realized, and the production efficiency, the product quality and the product percent of pass are improved. The infrared spectrum range is selected, the anti-interference capability is strong, the measurement precision is high, the product quality control in industrial mass production is well realized, the cost is reduced, and the operation is convenient.

(3) The branch sample cell combines the measurement of fiber probe, has reduced sample measurement pretreatment process, reduces the loaded down with trivial details process of detection, realizes on-line measuring.

(4) The detection method is easy to realize, has wide requirements on environmental conditions, and is suitable for detecting the olefin, the alkane and the alkyne in the hydrocarbons which are liquid at the temperature of between 80 ℃ below zero and 200 ℃ and under the pressure of 69 bar.

(5) The detection has no damage to the sample, other auxiliary reagents are not required to be added, the detection difficulty is reduced, the detection frequency is improved, and timely data guidance is provided for process operation.

(6) The detection carbon number is C4-C40, and the range is wider.

Drawings

FIG. 1 is a schematic diagram of the process for separating linear olefins according to the present invention.

FIG. 2 is a schematic view of the detection of a sample according to the present invention

Detailed Description

The process flow of the invention is shown in figure 1, and the raw materials are subjected to deacidification treatment, fraction cutting, extractive distillation to remove oxygenated compounds, simulated moving bed I to separate alkane-olefin, simulated moving bed II to separate straight chain-isoolefin, and adsorption drying treatment to obtain a polymer grade straight chain olefin product.

In the process of technological production, the precision of technological control has great influence on the quality of products, and the online real-time detection of material composition is very important. The schematic diagram of the sample detection of the present invention is shown in fig. 2. And a branch with a test sample pool is arranged on the material pipeline, and an online mid-infrared spectrometer is adopted to detect the material in the sample pool.

The detection steps are as follows:

(1) calibration model establishment

Determining the contents of olefin, alkane and alkyne in 100 Fischer-Tropsch synthesis oil samples by adopting a gas chromatography; and then, performing mid-infrared spectrum scanning on each sample through a sample cell, and selecting C-C bond at 3100-3010 cm^-1Is a characteristic spectral region; the C-C bond is 2975-2800 cm^-1Is a characteristic spectral region; the C ≡ C bond is 3300-2150 cm^-1Relating the response value of the characteristic spectrum region with the contents of alkene, alkane and alkyne of a sample determined by adopting a gas chromatography, and respectively establishing a correction model by adopting a least square method of a stoichiometric method;

the sample enters a sample cell from an inlet pipe after passing through a material pipeline, the inlet pipe and an outlet pipe which enter a test sample cell are respectively led out from the front and the back of a regulating valve with pressure difference in the material pipeline, the pressure in the sample cell is regulated to be below 69bar through a valve, the temperature of the material entering the sample cell is not higher than 200 ℃, the sample cell is a branch flow sample cell, and an infrared spectrometer adopts an optical fiber probe type measurement.

The gas chromatograph is Agilent 7820 gas chromatograph, PONA chromatographic column, split/non-split sample inlet, and PONA chromatographic column.

The used mid-infrared spectrometer is a Metler ReactrI 15, and the spectral range is 4000-650cm^-1Resolution of 4cm^-1。

And performing spectral scanning through the optical fiber probe, and processing through an instrument software workstation to obtain the spectral peak height under the characteristic wavelength.

(2) Determination of content

Performing mid-infrared spectrum scanning on the sample under the same test condition as that of the calibration model, wherein the mid-infrared spectrum scanning is respectively 3100-3010 cm^-1、2975～2800cm^-1、3300～2150cm^-1And substituting the response values of the spectral regions into the corresponding correction models to obtain the contents of the alkene, the alkane and the alkyne in the sample. By comparing the detection result of the gas chromatography of the sample with the detection result of the on-line mid-infrared spectroscopy, the detection results of the on-line mid-infrared spectroscopy and the gas chromatography are basically consistent, and compared with the detection result of the gas chromatography,the maximum measurement deviation is only about +/-2%.

In the production process of the straight chain olefin, the content of olefin, alkane and alkyne in raw materials, products and intermediate products is measured in real time by adopting an online mid-infrared spectrometer, and the operating conditions of each process step are adjusted in real time according to the detection result.

The deacidification method comprises the following steps: firstly, distillate oil and a proper amount of potassium carbonate solution (the adding amount of potassium carbonate is 200-220 mgK)₂CO₃100ml distillate oil; the mass fraction of the potassium carbonate solution is 20 percent at normal temperature), the solution is added into a neutralization reactor, the mixture is fully stirred, after the reaction is completed, standing and layering are carried out, an emulsion phase and a water phase are transferred to a standing phase-splitting tank, water is injected for water washing (the volume ratio of the water to the oil is 3: 1), redundant alkali liquor is removed, after the water washing, standing and layering are carried out, and neutral distillate oil is sent to a subsequent working section.

The method for removing the oxygen-containing compounds comprises the following steps: introducing the oil product into an extraction and rectification tower, reversely contacting with an extracting agent, removing oxygen-containing compounds and controlling the content of the oxygen-containing compounds to be below 1000 ppm; the oil product is preheated to 40 deg.c in a preheating furnace and then in an adsorption tower with molecular sieve to further adsorb and separate oxide in the mass ratio of 13X molecular sieve to oil of 1 to 3 at 40 deg.c and 0.5MPa, with the content of the oxide being controlled below 1 ppm.

The simulated moving bed divides the fixed adsorption bed into a plurality of sections, the sections are filled with adsorbents, and liquid between the sections cannot directly flow through. Each section is provided with an inlet and outlet pipeline, and the inlet and outlet of the pipeline are controlled by a valve. Typically, in a simulated moving bed with 8 adsorption columns, 20 of 24 inlets and outlets only play a role in connection between sections, the other 4 inlets and outlets are used for the inlet or outlet of four strands of materials, the positions of the inlets and outlets of the materials at a certain moment divide the whole adsorption bed layer into four zones, the distances of the zones are unequal, and the mass transfer of each zone is different. The inlet and outlet of four materials in the simulated moving bed move upwards at a speed synchronous with the change of solid phase concentration, thus forming a closed loop, and the total result is basically the same as the effect of keeping the inlet and outlet positions still and the solid adsorbent moving from top to bottom in the adsorber, thereby achieving the separation effect.

A first simulated moving bed: the operation temperature is 50-100 ℃, the operation pressure is 0.4-0.6Mpa, the filler of the simulated moving bed is an A series molecular sieve (such as a 3A, 4A, 5A or modified 5A molecular sieve), the agent-oil ratio is 1: 1 (the mass ratio of the filler to the oil), and the content of the obtained olefin component is more than 99.9 wt%; a second simulated moving bed: the operating temperature is 50-100 ℃, the operating pressure is 0.5Mpa, the filler of the simulated moving bed is X series molecular sieve (such as 13X molecular sieve or modified 13X molecular sieve), the agent-oil ratio is 0.5-2: 1 (the mass ratio of the filler to the oil), the content of the obtained olefin component is more than 99.7 wt%, the distillate oil raw material source adopted by the invention is a 120-ten thousand ton/year coal oil production device of Nemengqiita chemical industry Limited liability company, and the components are shown in Table 1.

TABLE 1 distillate feedstock composition

Numbering	Species of matter	Content/wt%
			1	Alkanes (normal/iso-alkanes)	23.17
2	Olefins (normal/iso olefins)	71.83
			3	Acids substances	0.5
4	Alcohols	4
			5	Aldehydes, esters, ketones	0.5

The raw material composition of the distillate obtained after deacidification is shown in table 2.

TABLE 2 Deacidification distillate composition

Numbering	Species of matter	Content/wt%
			1	Alkanes (normal/iso-alkanes)	23.9
2	Olefins (normal/iso olefins)	74.1
			3	Acids (acids)	--
4	Aldehydes, esters, ketones	2

The distillate feedstock composition obtained after oxygenate removal is given in table 3.

TABLE 3 oxygenate removal distillate composition

Numbering	Species of matter	Content/wt%
			1	Alkanes (normal/iso-alkanes)	24.40
2	Olefins (normal/iso olefins)	75.59
			3	Acids (acids)	--
4	Aldehydes, esters, ketones	≤1ppm

Comparative example 1

The target carbon number is 6, and the alkane and the alkene are separated in an extraction and rectification mode after deacidification, fraction cutting and oxygen-containing compound removal treatment, and the separation is not carried out by a simulated moving bed. Wherein the operation temperature of the separation of the alkane and the alkene is 100-105 ℃, the temperature at the top of the tower is 48-50 ℃, the reflux ratio is 5, the agent-oil ratio is 1: 1 (the mass ratio of the filling agent to the oil), the extracting agent is NMP (the fourth extracting agent in the example 1 of the reference CN 105777467A), and the content of the obtained alkene component is 98.08 wt%; straight chain hydrocarbon and branched chain hydrocarbon are not separated, the boiling points are only 3 ℃ lower, and the separation by using a rectification method is very difficult.

Comparative example 2

The method for directly treating the Fischer-Tropsch light distillate oil by using the document US3510423 is not suitable for the process for preparing the single-carbon straight-chain hydrocarbon from the Fischer-Tropsch light distillate oil, and cannot separate single carbon, oxide and finally a single-carbon olefin product because a pretreatment working section is not provided.

Secondly, the step of removing the oxygen-containing compounds is very important, 5 percent of the oxygen-containing compounds in the raw materials can cause the service life of the adsorbent in the simulated moving bed to be reduced by about 50 percent, the ratio of the solvent to the oil needs to be increased from 1: 1 to 2: 1, the production cost is greatly increased, and meanwhile, the product purity is greatly influenced.

Moreover, the simulated moving bed equipment can obviously reduce energy consumption, is simple and convenient to operate, and greatly reduces the production cost.