阅读说明：本技术 一种烃类含量的在线检测方法 (Online detection method for hydrocarbon content ) 是由 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：本发明涉及一种烯烃含量的在线检测方法,具体包括如下步骤：(1)校正模型建立选取各种费托合成馏分油样品,采用气相色谱法测定其中烯烃、烷烃及炔烃的含量；再将各样品通过样品池进行中红外光谱扫描,选取C＝C键在3100～3010cm<Sup>-1</Sup>为特征谱区；C-C键在2975～2800cm<Sup>-1</Sup>为特征谱区；C≡C键在3300～2150cm<Sup>-1</Sup>为特征谱区,将上述特征谱区的响应值与样品采用气相色谱法测定的烯烃、烷烃及炔烃的含量相关联,采用化学计量法的最小二乘法分别建立校正模型；(2)未知样品含量测定在与建立校正模型相同的测试条件下进行未知样品的中红外光谱扫描,分别将在3100～3010cm<Sup>-1</Sup>、2975～2800cm<Sup>-1</Sup>、3300～2150cm<Sup>-1</Sup>谱区的响应值代入各自对应的校正模型,得到未知样品的烯烃、烷烃及炔烃的含量。该方法操作简单,环境条件要求宽,检测对样品无破坏性,且不需要加入其它辅助试剂。(The invention relates to an on-line detection method of olefin content, which specifically comprises the following steps: (1) establishing a correction model, selecting various Fischer-Tropsch synthesis distillate oil samples, and determining the contents of olefin, alkane and alkyne in the 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 ‑1 Is a characteristic spectral region; the C-C bond is 2975-2800 cm ‑1 Is a characteristic spectral region; the C ≡ C bond is 3300-2150 cm ‑1 Relating 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; (2) the content determination of the unknown sample is carried out on the mid-infrared spectrum scanning of the unknown sample under the same test condition as the establishment of the correction model, and the scanning range is 3100-3010 cm ‑1 、2975～2800cm ‑1 、3300～2150cm ‑1 Response of spectral regionAnd substituting the values into respective corresponding correction models to obtain the contents of olefin, alkane and alkyne in the unknown sample. The method is simple to operate, has wide requirements on environmental conditions, has no damage to samples during detection, and does not need to add other auxiliary reagents.)

1. An online detection method for hydrocarbon content comprises the following steps:

(1) calibration model establishment

Selecting various Fischer-Tropsch synthesis distillate oil samples, and determining the contents of olefin, alkane and alkyne in the Fischer-Tropsch synthesis distillate 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;

(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.

2. The on-line detection method of hydrocarbon content as claimed in claim 1, characterized in that: in the step (1), an inlet pipe and an outlet pipe which enter the test sample cell are respectively led out from the material pipeline before and after the regulating valve with the pressure difference.

3. The on-line detection method of hydrocarbon content as claimed in claim 2, characterized in that: in the step (1), the pressure in the sample cell is regulated to be lower than 69bar through a valve, and the temperature of materials entering the sample cell is not higher than 200 ℃.

4. The on-line detection method of hydrocarbon content as claimed in claim 1, characterized in that: in the step (1), a branch flow sample cell is adopted, and an infrared spectrometer adopts an optical fiber probe type measurement.

5. The on-line detection method of hydrocarbon content as claimed in claim 1, characterized in that: the mid-infrared spectrum model is Mettler Reactr 15, the spectral range is 4000-^-1Resolution of 4cm^-1。

6. The on-line detection method of hydrocarbon content as claimed in claim 4, characterized in that: 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.

7. The on-line detection method of hydrocarbon content as claimed in claim 6, characterized in that: the method for establishing the correction model by adopting the least square method of the chemometric method comprises the following steps:

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

(2) corresponding relation exists between each group of data (xi, yi);

(3) error e ═ yi- (axi + b);

(4) when in useThe minimum degree of fitting is the highest, i.e.

(5) respectively solving first-order partial derivatives:

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

(7) Finally, the following can be obtained:

(8) substituting the values x and y into each sample to obtain the values a and b.

Technical Field

The invention relates to an on-line detection method of hydrocarbon content based on mid-infrared spectrum, which is particularly suitable for the on-line detection method of alkane, alkene and alkyne content in Fischer-Tropsch synthetic distillate oil.

Background

As is well known, an olefin is a hydrocarbon compound containing a C ═ C bond (carbon-carbon double bond) (olefinic bond), which is an important chemical raw material and an organic synthetic intermediate, and has been widely used in the chemical field. It can be used to synthesize some high molecular materials, and can be used as synthetic intermediate of surfactant, plasticizer and additive for synthesizing hydrocarbon lubricating oil and oil product. In particular, the alpha-olefin has important application in the industries of spice, paper, daily chemical and the like.

Olefins in the current market are mainly derived from cracking of petroleum, from elimination of alcohols to produce olefins, from carbonyl compounds by a series of reactions, paraffin cracking, fischer-tropsch synthesis, and the like. 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 the content of olefin 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 for gasoline component C₄～C₁₂The octane number can be calculated by establishing a model, and the contents of olefin, alkane and alkyne can not be directly measured.

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 problem, the invention provides an online detection method for hydrocarbon content, which comprises the following steps:

(1) calibration model establishment

Selecting various Fischer-Tropsch synthesis distillate oil samples, and determining the contents of olefin, alkane and alkyne in the Fischer-Tropsch synthesis distillate 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;

(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, in the step (1), an inlet pipe and an outlet pipe which enter the test sample cell are respectively led out before and after the regulating valve with the pressure difference in the material pipeline;

preferably, in the step (1), the pressure in the sample cell is regulated to be below 69bar through a valve, and the temperature of materials entering the sample cell is not higher than 200 ℃;

preferably, in the step (1), a branch flow sample cell is adopted, and the infrared spectrometer adopts a fiber probe type measurement.

Preferably, the mid-infrared spectrum has a type Mettler Reactr 15, a spectral range of 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.

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 the olefin (or the alkane or the alkyne) at the characteristic wavelength and the concentration value x of the olefin (or the alkane or the alkyne) have the following relationship, wherein y is ax + b, a is a coefficient, and b is an intercept;

(2) corresponding relation exists between each group 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;

(5) respectively solving first-order partial derivatives:

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

(7) Finally, the following can be obtained:

(8) substituting the values x and y into each sample to obtain the values a and b.

Compared with the prior art, the method has the following advantages:

(1) the mid-infrared spectrum has strong anti-interference capability and high measurement precision.

(2) 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.

(3) 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.

(4) 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.

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

Drawings

FIG. 1 is a schematic view of the detection of a sample according to the present invention

FIG. 2 is a graph showing the linear relationship between the predicted value of the 1-hexene model and the measured value by gas chromatography

FIG. 3 is a linear relationship diagram of a predicted value of n-hexane model and a measured value of gas chromatography

FIG. 4 is a graph showing the linear relationship between the predicted value of the 3-chlorophenyl-1-propyne model and the value measured by gas chromatography

Detailed Description

The detection method of the present invention is further described below with reference to the accompanying drawings.