Method for measuring content of target component in coking crude benzene

Abstract

The invention provides a method for determining the content of a target component in coking crude benzene. The method for determining the content of the target component in the coking crude benzene comprises the following steps: mixing a coking crude benzene sample with internal standard substances 1, 4-dioxane and n-nonane, and injecting the mixture into a chromatographic instrument by adopting a capillary chromatographic column and taking methanol as a mobile phase to obtain a chromatogram and peak areas of all substances; calculating to obtain the content of the target component; the target components comprise benzene, toluene, ethylbenzene and xylene; wherein the xylene comprises p-xylene, m-xylene and o-xylene; the capillary chromatographic column comprises any one of a cross-linked and bonded polyethylene glycol quartz elastic capillary chromatographic column, a DB-1 chromatographic column and an HP-5 chromatographic column. According to the method disclosed by the invention, the component detection in the coking crude benzol is more accurate, the refining processing technology develops towards a more large-scale and multi-product deep processing direction, a higher additional value is generated, and the high-quality development of the industry is promoted.

Description

Technical Field

[0001] This invention belongs to the field of detection technology, and in particular relates to a method for determining the content of target components in coking crude benzene. Background Technology

[0002] Crude benzene is an organic liquid mixture mainly composed of benzene series compounds, recovered from crude coal gas generated by coal pyrolysis through a multi-stage countercurrent wash oil absorption method after ammonia removal. Benzene is the main component, accounting for about 70%. Crude benzene also contains small amounts of low molecular weight short-chain alkanes and unsaturated compounds. The wash oil absorption can achieve a recovery rate of 90% to 96%.

[0003] Crude benzene from coking plants can be refined into various products such as benzene, toluene, xylene, and heavy benzene. In recent years, coke production has been substantial, and the refining of crude benzene from coking plants has shown a trend towards large-scale, industrialized, and intensive processing. Current crude benzene refining technology generally employs a hydrogenation process, which boasts low energy consumption, low cost, high product quality, and strong competitiveness, representing one of the development directions for crude benzene processing and refining. This represents clean production that meets the requirements of high-quality development in ecological civilization and also allows for the full utilization of valuable benzene resources. Furthermore, existing crude benzene hydrogenation refining processes are categorized by reaction temperature into high-temperature methods (600~630℃) and low-temperature methods (320~380℃). Both methods convert olefins, cycloalkanes, sulfur-containing compounds, and nitrogen-containing compounds in the light benzene fraction after the heavy benzene removal unit into corresponding saturated hydrocarbons, and then separate aromatics and non-aromatics through extractive distillation. High-quality benzene, toluene, xylene, and other products can be obtained through distillation; and the high-temperature method simultaneously involves the hydrogenation and dealkylation of benzene homologues, allowing the removed alkyl groups to be used as a hydrogen source, eliminating the need for external hydrogen supply.

[0004] However, regardless of the type of crude benzene hydrogenation refining, it is necessary to detect the content of the three benzenes (benzene, toluene, and xylene) in the crude benzene. Therefore, a simple, accurate, and standardized detection method is particularly important. Currently, the publicly available technical data on the detection of the three benzenes in crude benzene are Appendix A of GB / T30053-2013 and YB / T5022-2016, which respectively use the area ratio method and the dioxane internal standard method. Although these two methods can meet the general testing needs of the industry, both the area ratio method and the single internal standard detection method have shortcomings. The area ratio method must ensure that every substance in the crude benzene shows a peak in the detection process, and the data calculation is mainly based on the assumption that the correction factors of various substances in crude benzene are the same, and the application is verified by experiments within a certain uncertainty range. The dioxane internal standard method, due to the large differences in composition between the internal standard and the five target substances (benzene, toluene, o-xylene, m-xylene, and p-xylene), will also affect the accuracy of the determination results.

[0005] Therefore, research is urgently needed to develop a more reliable and accurate method for determining BTEX in crude benzene.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a method for determining the content of target components in crude benzene from coking, so as to solve the above-mentioned problems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for determining the content of a target component in coking crude benzene. The method involves mixing a coking crude benzene sample with internal standards 1,4-dioxane and n-nonane to obtain an analytical sample. A capillary column is used with methanol as the mobile phase. The analytical sample is injected into the chromatograph to obtain a chromatogram and peak areas of each substance. The content of the target component is then calculated. The target components include benzene, toluene, ethylbenzene, and xylene; Xylene includes para-xylene, m-xylene, and o-xylene; The capillary column includes any one of the following: a cross-linked polyethylene glycol quartz elastic capillary column, a DB-1 column, and an HP-5 column. The chromatographic column used in this invention can separate the analytes.

[0009] Preferably, the method further includes pretreating the analytical sample; more preferably, the pretreatment includes: adding sodium hydroxide or potassium hydroxide to the analytical sample for dehydration, shaking, and standing, then allowing the analytical sample to reach room temperature, and taking the supernatant for later use. The dehydration, shaking, and standing operations can be repeated three times.

[0010] In the internal standard, the volume ratio of 1,4-dioxane to n-nonane is 3:1 to 4:1.

[0011] Preferably, the detection device used in the method is a flame hydrogen ionization detector (FID).

[0012] Preferably, the carrier gas for injection is nitrogen; more preferably, the injection flow rate is 90-110 mL / min.

[0013] More preferably, the injection volume is 0.5-0.8 μL.

[0014] Preferably, the temperature control method during column detection includes: maintaining an initial temperature of 45-55℃ for 10-12 minutes, then increasing the temperature at 5-8℃ / min to 90-100℃ and maintaining it for 10-12 minutes; then increasing the temperature at 10-12℃ / min to 200-205℃ and maintaining it for 15-20 minutes.

[0015] Optionally, the calculation formula is: ; in: x: Mass fraction of each target component in the crude benzene sample, in % m: Mass of crude benzene sample, in grams; A B Peak area of ​​benzene, in microvolt-seconds (μV·s); f i : Relative correction factor of benzene to the internal standard 1,4-dioxane; A S1 Peak area of ​​internal standard 1,4-dioxane, in microvolt-seconds (μV·s); m S1 Mass of internal standard 1,4-dioxane, in g; A S2 Peak area of ​​internal standard n-nonane, in microvolt-seconds (μV·s); m S2 Mass of the internal standard n-nonane, in grams; A j Peak areas of toluene, p-xylene, m-xylene, and o-xylene, in microvolt-seconds (μV·s); f j : The relative correction factor of toluene to the internal standard n-nonane.

[0016] Preferably, the f i The calculation formula is: ; in: f i : The relative correction factor of the component to the internal standard; A s Peak area of ​​the internal standard; A i Peak area of ​​the component; m i Mass of the component, in grams; m s : The mass of the internal standard, in grams.

[0017] f j This is the relative correction factor for toluene against the internal standard n-nonane; its calculation formula can be found in f. i The calculation formula can be obtained by simply replacing the corresponding components and internal standards.

[0018] In this application, 1,4-dioxane is used as an internal standard for benzene, and n-nonane is used as an internal standard for other benzene compounds (toluene and xylene). When calculating correction factors and results, attention should be paid to the corresponding relationships. In the formula, the relative correction factors of other benzene compounds (excluding benzene) relative to n-nonane are close to the relative correction factor of toluene; using the same value can reduce errors caused by the determination of correction factors.

[0019] The method for determining the benzene content in crude benzene is as follows: ; ; The relative correction factor f for benzene to the internal standard 1,4-dioxane was calculated using the above formula. i When using this formula to calculate the correction factor, the mass and peak area of ​​the internal standard 1,4-dioxane and benzene in the sample are accurately measured by internal standard analysis.

[0020] The first part of the summation term in the formula is the determination and calculation of benzene content, and the second part is the calculation of five components: toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene.

[0021] Similarly, the relative correction factor of toluene for n-nonane can be calculated using the following formula.

[0022] The correction factors for the three homologues of ethylbenzene and xylene are the relative correction factors of toluene to n-nonane.

[0023] ; ; You only need to calculate the total sum.

[0024] Preferably, the volume ratio of the coking crude benzene sample to the internal standard is 3:1 to 1:1.

[0025] This invention relates to the detection of benzene, toluene, ethylbenzene, and xylene (including three isomers: o-xylene, m-xylene, and p-xylene), abbreviated as BTEX, in crude coking benzene. It innovatively combines a gas chromatograph, a flame ionization detector (FID), and a cross-linked polyethylene glycol quartz capillary column, employing dual internal standards for quantification of each component. After pretreatment of the crude benzene sample to avoid the influence of moisture on the chromatographic column, a micro-injection technique is used to introduce the sample into the gas chromatograph, equipped with a cross-linked polyethylene glycol quartz capillary column capable of completely separating the corresponding components. This allows each component in the sample to be vaporized and ionized before entering the FID flame ionization detector. Then, the peak area or peak height of each component is used to quantify the individual components in the sample. Specifically, the internal standard 1,4-dioxane is used to determine the benzene content, and n-nonane is used to determine the toluene and xylene contents.

[0026] The beneficial effects of this invention are: Typically, the content of various components in crude benzene from coking plants varies considerably, with benzene accounting for approximately 70%, toluene approximately 12%, and the three isomers of xylene each accounting for approximately 1.5-2%. There are also many other unsaturated hydrocarbon mixtures. Existing single internal standard technologies do not have an ideal range of content, while increasing the number of internal standards significantly increases the difficulty of internal standard screening and makes the preparation and testing process more cumbersome. This invention uses dual internal standards, which overcomes the problem of insufficient accuracy in single internal standard measurements and avoids excessively increasing the workload and difficulty of detection, thus comprehensively improving detection efficiency and accuracy. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 The chromatograms are for 1,4-dioxane, n-nonane, benzene, toluene, and xylene. Figure 2 The chromatograms are of the components in the coking crude benzene sample obtained in Example 1. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that the gas chromatograph used in the embodiments of the present invention has a programmed temperature rise function, is equipped with a capillary column split / splitless injection port, an FID flame ionization detector, a chromatography workstation, and has an automatic injection system. It can also use a micro-injector for injection. The instrument sensitivity meets the requirements of GB / T9722. A 0.1 mg sensitivity and a 200 g range analytical balance is used for weighing.

[0031] Example 1 This embodiment provides a method for determining the content of a target component in crude benzene from coking, specifically including the following steps: S1: Take five 5mL volumetric flasks, first inject 2mL of methanol into each volumetric flask, then use a 50μL microsyringe to inject 25μL of chromatographic grade benzene, 25μL of chromatographic grade toluene, 25μL of chromatographic grade p-xylene, 25μL of chromatographic grade m-xylene and 25μL of chromatographic grade o-xylene into each of the five volumetric flasks respectively, and mix them thoroughly to obtain qualitative samples for later use; S2: Accurately measure 30 mL of benzene, 10 mL of toluene, 1 mL of p-xylene, 1 mL of m-xylene, and 1 mL of o-xylene using a pipette and inject them into a clean, dry 50 mL volumetric flask. Mix thoroughly to obtain a sample simulation mixture for later use; or, accurately weigh 26.22 g of benzene, 8.65 g of toluene, 0.857 g of p-xylene, 0.868 g of m-xylene, and 0.879 g of o-xylene using the incremental method on an analytical balance and mix thoroughly in a volumetric flask to obtain the sample simulation mixture. S3: Accurately measure 15 mL of 1,4-dioxane and 5 mL of n-nonane using a pipette as internal standards for benzene and other analytes, respectively. Place them in a clean, dry 20 mL volumetric flask and mix thoroughly to obtain the internal standard mixture. Alternatively, accurately weigh 15.51 g of 1,4-dioxane and 3.59 g of n-nonane using the incremental method on an analytical balance and mix thoroughly to obtain the internal standard mixture. S4: Use a 2mL single-mark pipette to take 1mL each of the sample simulation mixture obtained in S2 and the internal standard mixture obtained in S3, add them to a 2mL sealed sample bottle to obtain the analytical sample, mix well and set aside for later use. S5: Place 300 mL of the sample in a clean and dry 500 mL ground glass conical flask, add about 100 g of sodium hydroxide or potassium hydroxide for dehydration, stopper and shake thoroughly for 5 min, let stand for 5 min, repeat the shaking and standing process three times to bring the sample to room temperature, use a pipette to measure 10 mL of the upper liquid and inject it into a clean, dry, stoppered 20 mL single-mark volumetric flask, use a 2 mL single-mark pipette to take 1 mL of it, then take 1 mL of the internal standard mixture obtained in S3 and add it to a 2 mL sealed sample bottle to obtain the pretreated analytical sample, mix well and set aside for use.

[0032] Test case First, qualitative analysis of components: Component identification was performed by comparing the retention times of the chromatographic peaks of each component in the sample with those of the component chromatographic peaks in the qualitative sample prepared in S1 of Example 1. The retention times of each component in the qualitative sample are shown in Table 1 below.

[0033] Table 1 Retention time table of each component in the qualitative sample After the instrument stabilizes, under the test conditions specified in Table 2, inject 0.8 μL of the analytical sample obtained in S4 and the pretreated analytical sample obtained in S5 into the chromatograph using a 1 μL syringe. Record the chromatogram and peak area on the chromatographic workstation.

[0034] Table 2 Chromatographic Operating Conditions Result calculation: Use the following formula for calculation: ; x: Mass fraction of each target component in the crude benzene sample, in % m: Mass of crude benzene sample, in grams; A B Peak area of ​​benzene, in microvolt-seconds (μV·s); f i : Relative correction factor of benzene to the internal standard 1,4-dioxane; A S1 Peak area of ​​internal standard 1,4-dioxane, in microvolt-seconds (μV·s); m S1 Mass of internal standard 1,4-dioxane, in g; A S2 Peak area of ​​internal standard n-nonane, in microvolt-seconds (μV·s); m S2 Mass of the internal standard n-nonane, in grams; A j Peak areas of toluene, p-xylene, m-xylene, and o-xylene, in microvolt-seconds (μV·s); f j : The relative correction factor of toluene to the internal standard n-nonane.

[0035] Among them, f i The calculation formula is: ; f i : The relative correction factor of the component to the internal standard; A s Peak area of ​​the internal standard; A i Peak area of ​​the component; m i Mass of the component, in grams; m s : The mass of the internal standard, in grams.

[0036] In addition, f j The calculation formula can be found in f. i .

[0037] ; ; m s : The mass of the internal standard, in grams; m i : Mass of the analyte in the sample, in g; m: Mass of crude benzene sample, in g; A i Peak area of ​​the measured component, in microvolt-seconds (μV·s); A s Peak area of ​​the internal standard, in microvolt-seconds (μV·s); f i : Relative correction factor for the analyte; x i : Mass fraction of the analyte, %.

[0038] When calculating correction factors and results, attention should be paid to the correspondence. In the formula, the relative correction factors of benzene compounds other than benzene relative to n-nonane are close to the relative correction factor of toluene. Taking the same value can reduce the error caused by the determination of correction factors.

[0039] The arithmetic mean of two independent measurements obtained under repeatability conditions is taken as the final test result, and the value is rounded to two decimal places according to the numerical rounding rules of GB / T 8170.

[0040] Figure 1 Chromatograms of internal standards 1,4-dioxane, n-nonane, benzene, toluene, and xylene; Figure 2 The chromatogram is obtained for the crude benzene sample provided in Example 1.

[0041] The test results are shown in Table 3-4 below: Table 3 Test Results of Example 1-1 Table 4 Test Results of Example 1-2 As can be seen from the table above, regardless of the amount of the main component, when using the same bottle of solvent with pre-added internal standard, the peak area of ​​the internal standard meets the repeatability requirements of the chromatograph for peak area.

[0042] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for determining the content of a target component in crude benzene from coking, characterized in that, The coking crude benzene sample was mixed with the internal standard 1,4-dioxane and n-nonane to obtain the analytical sample. The analytical sample was injected into the chromatograph using a capillary column with methanol as the mobile phase to obtain the chromatogram and peak area of ​​each substance. The content of the target component was calculated. The target components include benzene, toluene, ethylbenzene, and xylene; Xylene includes para-xylene, m-xylene, and o-xylene; The capillary column includes any one of the following: a cross-linked polyethylene glycol quartz elastic capillary column, a DB-1 column, and an HP-5 column.

2. The method according to claim 1, characterized in that, The method further includes pretreating the analytical sample; The pretreatment includes: adding sodium hydroxide or potassium hydroxide to the analytical sample for dehydration, shaking, and standing, then allowing the analytical sample to reach room temperature, and taking the upper liquid for later use.

3. The method according to claim 1, characterized in that, In the internal standard, the volume ratio of 1,4-dioxane to n-nonane is 3:1 to 4:

1.

4. The method according to claim 1, characterized in that, The detection device used in the method includes a FID (Flame Ionization Detector).

5. The method according to claim 4, characterized in that, The carrier gas for the injection is nitrogen; the injection flow rate is 90-110 mL / min.

6. The method according to claim 4 or 5, characterized in that, The injection volume is 0.5-0.8 μL.

7. The method according to claim 1, characterized in that, The temperature control method for column detection includes: initial temperature of 45-55℃ for 10-12 min, then increasing the temperature to 90-100℃ at 5-8℃ / min and holding for 10-12 min; then increasing the temperature to 200-205℃ at 10-12℃ / min and holding for 15-20 min.

8. The method according to claim 3, characterized in that, The formula for the calculation is: ； in: x: Mass fraction of each target component in the crude benzene sample, in % m: Mass of crude benzene sample, in grams; A B Peak area of ​​benzene, in microvolt-seconds (μV·s); f i : Relative correction factor of benzene to the internal standard 1,4-dioxane; A S1 Peak area of ​​internal standard 1,4-dioxane, in microvolt-seconds (μV·s); m S1 Mass of internal standard 1,4-dioxane, in g; A S2 Peak area of ​​internal standard n-nonane, in microvolt-seconds (μV·s); m S2 Mass of the internal standard n-nonane, in grams; A j Peak areas of toluene, p-xylene, m-xylene, and o-xylene, in microvolt-seconds (μV·s); f j : The relative correction factor of toluene to the internal standard n-nonane.

9. The method according to claim 8, characterized in that, The f i The calculation formula is: ； in: f i : The relative correction factor of the component to the internal standard; A s Peak area of ​​the internal standard; A i Peak area of ​​the component; m i Mass of the component, in grams; m s : The mass of the internal standard, in grams.

10. The method according to claim 1, characterized in that, The volume ratio of the coking crude benzene sample to the internal standard is 3:1 to 1:1.

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