A method and system for analyzing sulfide forms in an alkylated sulfuric acid working solution

Abstract

The present application relates to the technical field of petroleum chemical analysis, and provides a method and system for analyzing the form of sulfides in a sulfuric acid alkylation working solution, the method comprising the following steps: S1, sample collection and pretreatment; S2, derivatization reaction; S3, separation and detection; S4, data processing and analysis; the system comprises a sample pretreatment module, a derivatization reaction module, a separation and detection module, and a data processing and analysis module, the method provided by the present application can accurately and quickly analyze the form and content of various sulfides in the working solution, has high sensitivity and accuracy, is simple and fast to operate, has good versatility and expansibility, is suitable for qualitative and quantitative analysis of the form of various sulfides in the field of petroleum chemical industry, and has important industrial application value.

Description

Technical Field

[0001] This invention relates to the field of petrochemical analysis technology, and in particular to a method and system for analyzing the speciation of sulfides in sulfuric acid alkylation working fluid. Background Technology

[0002] In petroleum refining, sulfuric acid alkylation is a crucial method for producing high-octane gasoline blending components. However, sulfides present in the sulfuric acid alkylation working fluid can significantly impact product quality, equipment corrosion, and subsequent processing. Therefore, accurately analyzing the morphology of sulfides in the working fluid is essential for optimizing process operations, improving product quality, and reducing equipment corrosion risks.

[0003] Currently, traditional sulfide analysis methods have many limitations. For example, patent CN111537503B discloses a sulfide analysis method and an automatic sulfide analyzer. This method directly measures the absorbance signal value at a preset wavelength by preparing a sulfur colloidal solution and establishing a standard working curve, thereby measuring the sulfide concentration in the sample. This method has small sample volume, is simple to operate, and can achieve rapid and accurate quantitative analysis. However, this method mainly targets the determination of total sulfide content and does not cover the determination of different forms of sulfides (such as thioesters, thiols, thioethers, etc.), making it difficult to meet the needs of accurate identification of multiple sulfide structures in complex systems. Patent CN108074255B discloses a method, device, and system for extracting sulfide morphology information in sulfide-type hydrogenation catalysts based on heterogeneous parallel processing. This method extracts sulfide morphology information by preprocessing the catalyst grayscale image and using geometric line segment fitting. This method, which analyzes lamellar length and distribution and combines heterogeneous parallel processing technology to achieve efficient analysis of multiple images, significantly improves the speed and accuracy of sulfide morphology extraction. However, it relies on the geometric feature analysis of microscopic images and cannot directly obtain sulfide chemical composition information, making it unsuitable for qualitative and quantitative analysis of different sulfide morphologies in complex liquid systems. Patent CN101556247B discloses an analytical method for sulfide morphology distribution in C5 feedstock and fractions. This method uses ultraviolet fluorescence, potentiometric titration, silver nitrate washing-ultraviolet fluorescence, and Zn-HAc reduction to sequentially determine the contents of total sulfur, hydrogen sulfide sulfur, mercaptan sulfur, thioether sulfur, and disulfide sulfur, and calculates the residual sulfur content using the difference method, achieving quantitative analysis of multiple sulfide morphologies. While this method has high repeatability and precision, its operation steps are cumbersome and the analysis time is long. It cannot obtain multiple sulfide morphologies and contents using a single instrument, making it difficult to meet the needs of rapid and accurate analysis in industrial production.

[0004] Therefore, there is an urgent need in the market for a method and system for analyzing the speciation of sulfides in sulfuric acid alkylation working solutions, which can achieve rapid and accurate detection of the speciation and content of various sulfides in sulfuric acid alkylation working solutions, and has good versatility and scalability. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention discloses a method and system for analyzing the speciation of sulfides in sulfuric acid alkylation working fluid. This method can accurately and quickly analyze the speciation and content of various sulfides in the working fluid, solving the problems of inaccurate analysis, low sensitivity, and complex operation in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for analyzing the speciation of sulfides in a sulfuric acid alkylation working solution, comprising the following steps:

[0008] S1. Sample collection and pretreatment: Collect working solution samples from the sulfuric acid alkylation unit, add pretreatment extract, extract, filter, concentrate, and obtain pretreated samples for later use.

[0009] S2, Derivatization reaction: The sample after pretreatment in step S1 is derivatized to convert different forms of sulfides into easily detectable derivatives, and the derivatized sample is obtained.

[0010] S3. Separation and detection: The sample derivatized in step S2 is separated and detected by gas chromatography-mass spectrometry to obtain detection data;

[0011] S4. Data Processing and Analysis: Data processing software is used to process and analyze the test data to obtain information on the types and contents of sulfides.

[0012] The applicant effectively removed interfering impurities by selectively extracting and precisely filtering the sulfuric acid alkylation working solution samples; subsequently, the samples were derivatized to convert different forms of sulfides into easily detectable derivatives; high-sensitivity and high-resolution separation and detection were achieved using a two-dimensional gas chromatography-sulfur chemiluminescence detector-mass spectrometer to accurately distinguish the forms and contents of various sulfides; finally, the detection data were processed and analyzed using dedicated software to generate an accurate report on the types and contents of sulfides.

[0013] In some embodiments of the present invention, the pretreatment extract in step S1 is a mixture of at least one of dimethyl phthalate and dichloromethane and a demulsifier.

[0014] In some embodiments of the present invention, the amount of demulsifier added to the pretreatment extract in step S1 is 0.5-3.0 wt%.

[0015] In some embodiments of the present invention, the demulsifier is an aqueous solution of sodium hydroxide.

[0016] Preferably, the demulsifier is a 5 wt% sodium hydroxide aqueous solution.

[0017] The applicant chose sodium hydroxide aqueous solution as a demulsifier, which serves the core function of breaking the emulsion layer formed by sulfuric acid and the hydrocarbon phase. In addition, it also produces two unexpected effects: acid neutralization and sulfide protection. Firstly, it acts as a deacidifying and purifying agent, reducing the interference of sulfuric acid on subsequent derivatization. If residual free sulfuric acid in the sulfuric acid alkylation working solution is not completely removed, it will react with derivatizing reagents (such as acid anhydrides in acylation reagents and alkyl halides in alkylation reagents) in side reactions. Sulfuric acid will react with acylation reagents to generate carboxylic acids, consuming effective reagents and producing impurity peaks, thus interfering with the detection of thiols. Furthermore, sulfuric acid will catalyze the hydrolysis of alkylation reagents, preventing the effective conversion of thioethers into sulfonates and reducing detection sensitivity. The alkaline demulsifier sodium hydroxide can neutralize the residual sulfuric acid, and the resulting salts can be further purified by subsequent derivatization. The continuous precision filtration thoroughly removes thiols, indirectly achieving simultaneous "demulsification + deacidification," eliminating the need for a separate water washing and deacidification step and shortening pretreatment time. Secondly, it avoids the oxidation of thiols, ensuring the accuracy of speciation analysis. Thiols (such as methanethiol and ethanethiol) are strong reducing substances, and under acidic conditions (residual sulfuric acid), they are easily oxidized to disulfides by oxygen in the air, causing the "thiol speciation" to be misjudged as the "disulfide speciation," resulting in biased analytical results. However, the alkaline demulsifier can adjust the pH of the system to a weakly alkaline state. In a weakly alkaline environment, the oxidation rate of thiols is significantly reduced, effectively preserving the original speciation of thiols and ensuring that subsequent derivatization reactions only target the "original thiols," avoiding speciation misjudgment caused by oxidation. This effect is difficult to achieve in traditional pretreatment operations that use only organic solvent extraction without an alkaline demulsifier.

[0018] In some embodiments of the present invention, the extractant used in the extraction operation of step S1 is dimethyl sulfoxide or N-methylpyrrolidone.

[0019] Dimethyl sulfoxide or N-methylpyrrolidone is immiscible with hydrocarbon phases, has a significant density difference, and has a different boiling point than sulfides. As an extractant, it can facilitate subsequent distillation and separation.

[0020] In some embodiments of the present invention, in the derivatization reaction of step S2, acylation reaction is performed on thiol sulfides using an acylation reagent, and alkylation reaction is performed on thioether sulfides using an alkylation reagent.

[0021] In some embodiments of the present invention, the acylation reagent is pentafluorobenzoyl chloride.

[0022] Preferably, a catalyst is added to the acylation reaction in combination with the acylation reagent, and the molar ratio of the acylation reagent to the catalyst is 1:(0.5-1.2).

[0023] Preferably, the catalyst is triethylamine.

[0024] In some embodiments of the present invention, the alkylating agent is any one of dimethyl sulfate, iodomethane, and bromoethane.

[0025] In some embodiments of the present invention, in the separation and detection step S3, the gas chromatography conditions of the gas chromatography-mass spectrometry system include: using a normal two-dimensional chromatographic column system matched with a capillary column, and using a programmed temperature ramp; the mass spectrometry conditions include: using an electron impact source.

[0026] Another aspect of the present invention provides a system for analyzing the speciation of sulfides in sulfuric acid alkylation working solutions. The system is applied to a method for analyzing the speciation of sulfides in sulfuric acid alkylation working solutions. The system includes a sample pretreatment module, a derivatization reaction module, a separation and detection module, and a data processing and analysis module.

[0027] The sample pretreatment module includes an extraction device, a filtration device, and a temperature and stirring control unit, used for pretreatment of the sulfuric acid alkylation working solution sample;

[0028] The derivatization reaction module includes a reagent addition system and a reaction temperature and time control system, which are used to perform derivatization reactions on pretreated samples;

[0029] The separation and detection module uses a two-dimensional gas chromatography-tandem sulfur chemiluminescence detector-mass spectrometer to separate and detect the derivatized sample;

[0030] The data processing and analysis module includes a data processing software system and a data storage device, which are used to process and analyze the detection data and generate reports.

[0031] The pretreatment module and derivatization reaction module in the analytical system designed by the applicant are not operated independently. Instead, they are connected through a process of "concentration followed by direct injection derivatization" and synergistic effects between modules. This reduces the loss of sulfide transfer and avoids the problem of loss caused by the disconnect between the pretreatment and derivatization modules in traditional methods.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) This invention provides a method and system for analyzing the speciation of sulfides in a sulfuric acid alkylation working solution. The system consists of a sample pretreatment module, a derivatization reaction module, a separation and detection module, and a data processing and analysis module. It completes sample collection and pretreatment, derivatization reaction, separation and detection, and data processing and analysis. It can accurately and quickly analyze the speciation and content of various sulfides in the working solution, solves the problems of inaccurate analysis, low sensitivity, and complicated operation in the prior art, and has good versatility and scalability.

[0034] (2) In step S1, the present invention adds a pretreatment extract and specifically defines the composition of the demulsifier in the sample collection and pretreatment stage. While breaking the emulsion layer formed by sulfuric acid and hydrocarbon phase, it also has the functions of deacidification, purification and protection of sulfides from oxidation, so that the analytical method has good detection sensitivity and accuracy.

[0035] (3) The pretreatment module and derivatization reaction module in the analysis system designed in this invention achieve the effect of reducing sulfide transfer loss through the process of "concentration followed by direct injection derivatization" and the synergistic effect between modules, thus avoiding the problem of loss caused by the disconnect between the pretreatment and derivatization modules in traditional methods. Attached Figure Description

[0036] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0037] Figure 1 This is a schematic diagram of a sulfide speciation analysis system in a sulfuric acid alkylation working solution according to an embodiment of the present invention. Detailed Implementation

[0038] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0039] In the following examples, the compound monomers and related reagents used were all commercially available.

[0040] Example 1

[0041] The standardized analytical method for sulfides includes the following steps:

[0042] S1. Sample preparation: Prepare a 10 mg / L methanethiol standard solution for later use;

[0043] S2, Derivatization reaction: Take 5 mL of the methanethiol standard solution from step S1, add 1.3 µmol pentafluorobenzoyl chloride and 1.3 µmol triethylamine, and react at 60℃ for 30 min to obtain the derivatized sample for later use.

[0044] S3. Separation and Detection: The derivatized sample from step S2 was injected into a two-dimensional gas chromatography-tandem sulfur chemiluminescence detector-mass spectrometer for analysis. The gas chromatography conditions were as follows: one-dimensional column: HP-5MS (30 m × 0.32 mm × 0.25 μm) nonpolar capillary column; two-dimensional column: BPX-50 (0.8 m × 0.18 mm × 0.18 μm) medium polarity capillary column. The column temperature was programmed, starting at 50℃ and holding for 5 min, then increasing to 280℃ at a rate of 10℃ / min. Qualitative analysis of the sulfide derivatives was performed by comparing the retention time and mass spectrum with those of the standard. Quantitative analysis was performed using the single-point external standard method.

[0045] S4. Data Processing and Analysis: The data obtained from the two-dimensional gas chromatography-sulfur chemiluminescence detector-mass spectrometry system were processed using the dedicated GC-Image software. The software automatically identified the characteristic peaks of thiol sulfide derivatives.

[0046] By analyzing the peak area of ​​the derivative and comparing it with the peak area at which complete conversion is theoretically achieved (calculated based on the initial concentration of thiol), the derivatization rate is calculated. If the derivatization rate is 98%, and the derivatization rate is ≥95%, then the analytical method is proven to be accurate.

[0047] Example 2

[0048] A method for analyzing the speciation of sulfides in a sulfuric acid alkylation working solution includes the following steps:

[0049] S1. Sample Collection and Pretreatment: 100 mL of working solution sample was collected from the sulfuric acid alkylation unit and transferred to the extraction unit. 20 mL of pretreatment extraction buffer (98 wt% dimethyl phthalate and 2 wt% 5 wt% sodium hydroxide aqueous solution) was added. Extraction was performed for 15 min with N-methylpyrrolidone at a stirring speed of 200 r / min in an ice bath at 0°C. After extraction, the extract was filtered through a 0.2 μm pore size filter to remove solid impurities. The sample was then concentrated using a nitrogen purging device under the following conditions: 0°C ice bath, nitrogen flow rate 1.2 L / min, to obtain the pretreated sample.

[0050] S2, Derivatization reaction: Take 5 ml of the pretreated sample from step S1 into a reaction vessel, add 0.5 µmol pentafluorobenzoyl chloride and 0.5 µmol triethylamine, and react at 60 °C for 30 min to obtain the derivatized sample;

[0051] S3. Separation and Detection: The derivatized sample from step S2 was injected into a two-dimensional gas chromatography-tandem sulfur chemiluminescence detector-mass spectrometer for analysis. The gas chromatography conditions were as follows: one-dimensional column: HP-5MS (30 m × 0.32 mm × 0.25 μm) nonpolar capillary column; two-dimensional column: BPX-50 (0.8 m × 0.18 mm × 0.18 μm) medium polarity capillary column. The column temperature was programmed, starting at 50℃ and holding for 5 min, then increasing to 280℃ at a rate of 10℃ / min. Qualitative analysis of the sulfide derivatives was performed by comparing the retention time and mass spectrum with those of the standard. Quantitative analysis was performed using the single-point external standard method.

[0052] S4. Data Processing and Analysis: The data obtained from the two-dimensional gas chromatography-sulfur chemiluminescence detector-mass spectrometry system were processed using the dedicated two-dimensional GC-Image software. The software automatically identified the characteristic peaks of thiol sulfide derivatives and calculated the content of thiol sulfides to be 3.5 mg / L based on the standard curve.

[0053] Example 3

[0054] A method for analyzing the speciation of sulfides in a sulfuric acid alkylation working solution includes the following steps:

[0055] S1. Sample Collection and Pretreatment: 100 mL of working solution sample was collected from the sulfuric acid alkylation unit and transferred to the extraction unit. 20 mL of pretreatment extraction buffer (98 wt% dimethyl phthalate and 2 wt% 5 wt% sodium hydroxide aqueous solution) was added. Extraction was performed for 15 min with N-methylpyrrolidone at a stirring speed of 200 r / min in an ice bath at 0°C. After extraction, the extract was filtered through a 0.2 μm pore size filter to remove solid impurities. The sample was then concentrated using a nitrogen purging device under the following conditions: 0°C ice bath, nitrogen flow rate 1.2 L / min, to obtain the pretreated sample.

[0056] S2, Derivatization reaction: Take 5 ml of the pretreated sample from step S1 into a reaction vessel, add 1.5 µmol of dimethyl sulfate, and react at 50℃ for 20 min to obtain the derivatized sample;

[0057] S3. Separation and Detection: The derivatized sample from step S2 was injected into a two-dimensional gas chromatography-tandem sulfur chemiluminescence detector-mass spectrometer for analysis. The gas chromatography conditions were as follows: one-dimensional column: HP-5MS (30 m × 0.32 mm × 0.25 μm) nonpolar capillary column; two-dimensional column: BPX-50 (0.8 m × 0.18 mm × 0.18 μm) medium polarity capillary column. The column temperature was programmed, starting at 50℃ and holding for 5 min, then increasing to 280℃ at a rate of 10℃ / min. Qualitative analysis of the sulfide derivatives was performed by comparing the retention time and mass spectrum with those of the standard. Quantitative analysis was performed using the single-point external standard method.

[0058] S4. Data Processing and Analysis: The data obtained from the two-dimensional gas chromatography-sulfur chemiluminescence detector-mass spectrometry system were processed using the dedicated two-dimensional GC-Image software. The software automatically identified the characteristic peaks of sulfide derivatives and calculated the content of sulfide derivatives to be 17.6 mg / L based on the standard curve.

[0059] A sulfide speciation analysis system for sulfuric acid alkylation working solutions, applied to the sulfide speciation analysis methods in sulfuric acid alkylation working solutions of Examples 2 and 3, is disclosed. The system includes a sample pretreatment module, a derivatization reaction module, a separation and detection module, and a data processing and analysis module. Figure 1 As shown.

[0060] Example 1 prepared a 10 mg / L methanethiol standard solution and used the sulfide analysis method of the present invention. The accuracy and feasibility of the analytical method were demonstrated by calculating the derivatization rate. Examples 2 and 3 tested thiol sulfides and thioether sulfides in the sulfuric acid alkylation working solution, respectively, and successfully obtained accurate content. This proves that the present invention creatively provides a method and system for analyzing the speciation of sulfides in sulfuric acid alkylation working solution, which can achieve rapid and accurate detection of the speciation and content of various sulfides in sulfuric acid alkylation working solution.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for analyzing sulfide forms in an alkylate working solution of sulfuric acid, characterized by, The method comprises the following steps: S1, sample collection and pretreatment: collecting a working liquid sample from a sulfur acid alkylation device, adding a pretreatment extractant, extracting, filtering, concentrating, and obtaining a pretreated sample for standby; S2, derivatization reaction: performing derivatization treatment on the pretreated sample of step S1 to convert different forms of sulfides into derivatives easy to detect, and obtaining a derivatized sample; S3, separation and detection: separating and detecting the derivatized sample of step S2 by a gas chromatography-mass spectrometry instrument to obtain detection data; The gas chromatography-mass spectrometry instrument is a full two-dimensional gas chromatography sulfur chemiluminescence detector-mass spectrometry instrument; S4, data processing and analysis: processing and analyzing the detection data by using a data processing software to obtain the type and content information of sulfides; The pretreatment extractant in step S1 is a mixture of at least one of dimethyl phthalate and dichloromethane and a demulsifier; The addition amount of the demulsifier in the pretreatment extractant in step S1 is 0.5-3.0wt%; The demulsifier is a sodium hydroxide aqueous solution.

2. The method for analyzing sulfide form in an alkylated sulfuric acid working solution according to claim 1, characterized by, The extractant used in the extraction operation in step S1 is dimethyl sulfoxide or N-methyl pyrrolidone.

3. The method for analyzing sulfide form in an alkylated sulfuric acid working solution according to claim 1, characterized by, In the derivatization reaction of step S2, acylation reagent is used for acylation reaction for mercaptan sulfides, and alkylating reagent is used for alkylation reaction for sulfide sulfides.

4. The method for analyzing sulfide form in an alkylated sulfuric acid working solution according to claim 3, characterized by, The acylation reagent is pentafluorobenzoyl chloride.

5. The method for analyzing sulfide form in an alkylate working solution of sulfuric acid according to claim 3, characterized by, The alkylating reagent is any one of dimethyl sulfate, iodomethane and bromoethane.

6. The method for analyzing sulfide form in an alkylate working solution of sulfuric acid according to claim 1, characterized by, In the separation and detection of step S3, the gas chromatography conditions of the gas chromatography-mass spectrometry instrument include: using a capillary column matched positive full two-dimensional chromatographic column system, and using a programmed temperature method for column temperature; the mass spectrometry conditions include: using an electron impact source.

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