Method for rapidly evaluating stability of gas standard material of sulfur compounds in natural gas

Abstract

The application discloses a method for rapidly evaluating stability of a gas standard substance of sulfur compounds in natural gas, which comprises calculating a unit peak area response value of the sulfur compounds, calculating an average response area, calculating an evaluation factor and stability judgment. The application solves the problems of complicated and tedious short-term stability investigation of the gas standard substance of sulfur compounds in natural gas, analysis response drift of the sulfur compounds, difficulty in stabilization and inaccuracy of comparison values, adopts a sulfur chemiluminescence gas chromatograph with an equal molar response to evaluate and verify the stability of the gas standard substance of multi-component sulfur compounds in natural gas, judges whether the standard substance values are accurate by calculating the evaluation factor ratio of each compound, and does not need to simultaneously perform alternating sample injection operation, only needs to analyze one measured sample by using the method, the analysis sample injection times are three, the evaluation result is the same as that of a traditional method, the method efficiency is improved by more than 4 times, and the method has the advantages of rapidness and simplicity.

Description

Technical Field

[0001] This invention relates to gaseous reference materials in the chemical metrology industry, specifically to a method for rapidly evaluating the stability of gaseous reference materials containing sulfur compounds in natural gas. Background Technology

[0002] The development of gaseous reference materials for sulfur compounds in natural gas is quite challenging. The main problem lies in the highly reactive nature of sulfur compounds, which readily undergo chemical adsorption onto the inner walls of gas cylinders. Multi-component gaseous reference materials for sulfur compounds in natural gas contain sulfur compounds with varying adsorption capacities, resulting in inconsistent adsorption amounts. At the same concentration, some components show a decrease in adsorption, leading to poor stability. Furthermore, the stability of gaseous reference materials needs to be evaluated during their development. Current methods generally employ a comparative approach, comparing a newly prepared gaseous reference material with existing ones. If the mass value of the existing gaseous reference material is lower than that of the newly prepared one, it indicates poor stability. This method requires the preparation of new sulfur compound gaseous reference materials for each evaluation, followed by comparison using the comparative method. This necessitates simultaneous analysis of both samples, resulting in a large analytical volume and making the process time-consuming and labor-intensive. Additionally, the analytical instruments used are typically sulfur chemiluminescence gas chromatographs or flame photometric gas chromatographs, which suffer from significant instrument drift, requiring multiple injections (at least six) to achieve stability, with analysis times generally exceeding several hours. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple and efficient method for rapidly evaluating the stability of sulfur compound gaseous standard materials in natural gas.

[0004] The objective of this invention is achieved through the following technical solution: a method for rapidly evaluating the stability of sulfur compound gaseous standard materials in natural gas, comprising the following steps:

[0005] S1. Calculate the unit peak area response value for sulfur compounds:

[0006] A gaseous standard of sulfur compounds in natural gas is passed into a gas chromatograph with a sulfur chemiluminescence detector exhibiting equimolar response characteristics. After separation, the unit peak area response value of the sulfur compounds is calculated using the following formula:

[0007]

[0008] In the formula, ω represents the number of sulfur atoms in the sulfur compound; A i A′ represents the peak area response value of the i-th sulfur compound. i The unit peak area response value of the i-th sulfur compound

[0009] S2. Calculate the average response area:

[0010] The average response area is calculated based on the unit peak area response value of the sulfur compound obtained in step S1. The calculation formula is as follows:

[0011]

[0012] Where n is the number of sulfur compounds, This represents the average peak area response value for each sulfur compound.

[0013] S3. Calculate the evaluation factors:

[0014] Based on the average response area obtained in step S2, the evaluation factor is calculated using the following formula:

[0015]

[0016] Where, θ i As an evaluation factor for i-sulfur compounds;

[0017] S4. Stability assessment:

[0018] If 95% ≤ θ i ≤105% indicates that the sulfur compound has good stability;

[0019] If θ i >105% or θ i If the value is less than 95%, it indicates that the stability of sulfur compounds does not meet the requirements.

[0020] Furthermore, the sulfur compound standard material is a multi-component sulfur compound gaseous standard material in methane.

[0021] Furthermore, the multi-component sulfur compound gas standard material is at least two of the following 12 types: hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide, ethyl mercaptan, carbon disulfide, ethyl sulfide, n-propanethiol, isopropanethiol, thiophene, dimethyl disulfide, methyl ethyl sulfide, or tetrahydrothiophene.

[0022] This invention has the following advantages: It solves the complex and cumbersome technical problem of short-term stability testing of sulfur compound gaseous standards in natural gas, overcomes the problems of sulfur compound analysis response drift and instability leading to inaccurate comparative values, and uses a sulfur chemiluminescence gas chromatograph with equimolar response to evaluate and verify the stability of multi-component sulfur compound gaseous standards in natural gas. The accuracy of the verification standard value is determined by calculating the evaluation factor ratio of each compound, and it eliminates the need for simultaneous alternating injection of two gas cylinders. Using this method, only one sample needs to be analyzed, with three injections required. The rating results are identical to traditional methods, and the method efficiency is improved by more than four times, offering advantages such as speed and simplicity. Attached Figure Description

[0023] Figure 1 The image shows the chromatograms of the elution peaks of the 12 sulfur compounds in Example 1. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. The scope of protection of the present invention is not limited to the following: Embodiment 1:

[0025] A sulfur chemiluminescence detector gas chromatograph needs to be validated using stable multi-component sulfur compound gaseous standards. It exhibits equimolar response characteristics, meaning that equal molar numbers of sulfur atoms produce approximately the same response.

[0026] A stable sulfur compound standard was selected—a gaseous standard of 12 sulfur compounds in methane. The 12 components were hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide, ethanethiol, carbon disulfide, ethanethiol, n-propanethiol, isopropanethiol, thiophene, dimethyl disulfide, and tetrahydrothiophene. The isomolar response characteristics of the 12 sulfur compounds were verified using a gas chromatograph with a sulfur chemiluminescence detector (Agilent Technologies, 7890B). The experimental method is as follows:

[0027] S1. Calculate the unit peak area response value for sulfur compounds:

[0028] A gaseous standard of sulfur compounds in natural gas is passed into a gas chromatograph with a sulfur chemiluminescence detector exhibiting equimolar response characteristics. After separation, the unit peak area response value of the sulfur compounds is calculated using the following formula:

[0029]

[0030] In the formula, ω represents the number of sulfur atoms in the sulfur compound; A i A′ represents the peak area response value of the i-th sulfur compound. i The unit peak area response value of the i-th sulfur compound

[0031] S2. Calculate the average response area:

[0032] The average response area is calculated based on the unit peak area response value of the sulfur compound obtained in step S1. The calculation formula is as follows:

[0033]

[0034] Where n is the number of sulfur compounds, This represents the average peak area response value for each sulfur compound.

[0035] S3. Calculate the evaluation factors:

[0036] Based on the average response area obtained in step S2, the evaluation factor is calculated using the following formula:

[0037]

[0038] Where, θ i As an evaluation factor for i-sulfur compounds;

[0039] S4. Stability assessment:

[0040] If 95% ≤ θ i ≤105% indicates that the sulfur compound has good stability;

[0041] If θ i >105% or θ i If the value is less than 95%, it indicates that the stability of sulfur compounds does not meet the requirements.

[0042] Experimental verification data are detailed in Table 1, and the peak chromatograms are shown in [reference needed]. Figure 1 .

[0043] Table 1.12 Verification data of isomolar response of sulfur compounds in the components

[0044]

[0045] From Table 1 and Figure 1 It can be seen that stable multi-component sulfur compound gaseous standards have an equimolar response in sulfur chemiluminescence gas chromatographs, and their evaluation factor is between 95% and 105%.

[0046] Example 2:

[0047] This method is defined as the evaluation factor method, and the comparison method is defined as the traditional method. First, the traditional method is used to determine the sample to be evaluated using a standard gas. To eliminate instrument drift caused by sulfur chemiluminescence gas chromatography, two samples are injected alternately before data processing and analysis. The gas to be evaluated is a standard gas of sulfur compounds in natural gas, containing ethanethiol and dimethyl disulfide. The standard gas is a national first- or second-level gas standard (No.: L185903045), and the sample to be evaluated is a newly prepared gas standard (No.: JN03202).

[0048] The stability of the two-component sulfur compound gaseous standard was evaluated using the traditional method. The experimental results are shown in Table 2.

[0049] Table 2. Evaluation of two-component sulfur compound gaseous reference materials using conventional methods

[0050]

[0051] As shown in Table 2, after evaluation of the sample values ​​by the traditional method, the differences between the two sulfur compounds in the sample (JN03202) and the nominal values ​​are both within 5%, which meets the qualification requirements.

[0052] The evaluation factor method was used to evaluate the tested samples, and the data are shown in Table 3.

[0053] Table 3. Evaluation of two-component sulfur compound gaseous reference materials using the evaluation factor method.

[0054]

[0055] As shown in Table 3, the evaluation factor of sample (JN03202) is within 95% ≤ θ. i Within the range of ≤105%, the tested sample meets the qualification requirements. This proves that the newly prepared gaseous standard substance has good short-term stability.

[0056] Example 3: A method for rapidly evaluating the stability of sulfur compound gaseous standard materials in natural gas, comprising the following steps:

[0057] S1. Calculate the unit peak area response value for sulfur compounds:

[0058] A gaseous standard of 12 sulfur compounds (sample number: SY11112) from a bottle of natural gas was passed into a gas chromatograph with a sulfur chemiluminescence detector having equimolar response characteristics. After separation, the unit peak area response value of each sulfur compound was calculated. The calculation formula is as follows:

[0059]

[0060] In the formula, ω represents the number of sulfur atoms in the sulfur compound; A i A′ represents the peak area response value of the i-th sulfur compound. i The unit peak area response value of the i-th sulfur compound

[0061] S2. Calculate the average response area:

[0062] The average response area is calculated based on the unit peak area response values ​​of each sulfur compound obtained in step S1. The calculation formula is as follows:

[0063]

[0064] Where n is the number of sulfur compounds, This represents the average peak area response value for each sulfur compound.

[0065] S3. Calculate evaluation factors:

[0066] Based on the average response area obtained in step S2, calculate each evaluation factor using the following formula:

[0067]

[0068] Where, θ i As an evaluation factor for i-sulfur compounds;

[0069] The experimental results are shown in Table 4:

[0070] Table 4. Evaluation of the tested samples using the evaluation factor method.

[0071]

[0072] S4. Stability assessment:

[0073] If 95% ≤ θ i ≤105% indicates that the sulfur compound has good stability;

[0074] If θ i >105% or θ i If the value is less than 95%, it indicates that the stability of sulfur compounds does not meet the requirements.

[0075] As shown in Table 4, the evaluation factors for methanethiol, ethanethiol, carbon disulfide, and dimethyl disulfide in the tested sample (SY11112) were not between 95% and 105%, failing to meet the qualification requirements. Therefore, this newly prepared gaseous standard substance is unqualified.

[0076] In summary, the evaluation factor can be used to determine whether the quality value of the verification standard is accurate, and it does not require the simultaneous alternating injection of two gas bottles. Using this method, only one sample needs to be analyzed, and the number of injections is three. The rating results are no different from those of the traditional method, and the method efficiency is improved by more than four times. It has the advantages of being fast and simple.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, are covered within the scope of protection of the present invention.

Claims

1. A method for rapidly evaluating the stability of gaseous reference materials containing sulfur compounds in natural gas, characterized in that, It includes the following steps: S1. Calculate the unit peak area response value for sulfur compounds: A gaseous standard of sulfur compounds in natural gas is passed into a gas chromatograph with a sulfur chemiluminescence detector exhibiting equimolar response characteristics. After separation, the unit peak area response value of the sulfur compounds is calculated using the following formula: ； In the formula, The number of sulfur atoms in the sulfur compound; The peak area response value of the i-th sulfur compound; This represents the unit peak area response value for the i-th sulfur compound; S2. Calculate the average response area: The average response area is calculated based on the unit peak area response value of the sulfur compound obtained in step S1. The calculation formula is as follows: ； in, The number of sulfur compounds. This represents the average peak area response value for each sulfur compound. S3. Calculate evaluation factors: Based on the average response area obtained in step S2, the evaluation factor is calculated using the following formula: ； in, As an evaluation factor for i-sulfur compounds; S4. Stability assessment: like This indicates that sulfur compounds have good stability; like or If the value is less than 95%, it indicates that the stability of sulfur compounds does not meet the requirements.

2. The method for rapidly evaluating the stability of sulfur compound gaseous standard materials in natural gas according to claim 1, characterized in that, The sulfur compound standard material is a multi-component sulfur compound gaseous standard material in methane.

3. The method for rapidly evaluating the stability of sulfur compound gaseous standard materials in natural gas according to claim 2, characterized in that, The multi-component sulfur compound gas standard is at least two of hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide, ethyl mercaptan, carbon disulfide, ethyl sulfide, n-propanethiol, isopropanethiol, thiophene, dimethyl disulfide, methyl ethyl sulfide, or tetrahydrothiophene.

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