A system and method for detecting and analyzing the content of sulfuric acid in the effluent of an alkylating reaction of sulfuric acid

Abstract

The application provides a system and a method for detecting and analyzing the content of sulfuric acid in the effluent of a sulfuric acid alkylation reaction. The system includes a sample collection and storage module, a sample pretreatment module, an acid-base titration detection module, and a data processing module. Through efficient and accurate detection and dynamic feedback of the content of free sulfuric acid in the effluent under complex working conditions, the system provides key support for device operation state monitoring, process monitoring, and product quality control, improves detection efficiency, is suitable for rapid detection and feedback during the operation of industrial devices, enhances the timeliness and safety of process control, and has wide industrial applicability and promotional value.

Description

Technical Field

[0001] This invention relates to the field of petrochemical analysis technology, and in particular to a system and method for detecting and analyzing the sulfuric acid content in effluents from sulfuric acid alkylation reactions. Background Technology

[0002] With the continuous improvement of refined oil quality standards, the limits for components such as aromatics, sulfur, and olefins in gasoline are becoming increasingly stringent. Alkylated gasoline, due to its advantages such as high octane number, high anti-knock properties, and low aromatic and olefin content, has become an ideal gasoline blending component. Currently, common industrial alkylation processes are mainly classified into hydrofluoric acid process, sulfuric acid process, ionic liquid acid process, and solid acid process based on catalyst type. Among them, the sulfuric acid alkylation process uses concentrated sulfuric acid with a concentration of over 90 wt% as a catalyst, utilizing isobutane and low-carbon olefins to undergo an alkylation reaction under the catalysis of concentrated sulfuric acid to produce high-octane alkylated gasoline. This process has advantages such as high catalytic efficiency, wide availability of raw materials, low price, and stable process flow, and is widely used in industrial production.

[0003] In this process, the residual free sulfuric acid content in the reaction effluent is a key parameter for assessing the completion of the sulfuric acid alkylation reaction and the safety of subsequent product processing. Excessive free sulfuric acid content may cause corrosion of subsequent separation units and piping systems, increasing operating and maintenance costs and affecting the stability of the alkylation product quality. Furthermore, the neutral sulfate esters generated by the alkylation side reaction are insoluble in water but readily soluble in organic solvents such as ethanol, ether, and benzene. Under high temperature or strong alkaline environments, they easily hydrolyze to form sulfuric acid, thus interfering with the accurate determination of the free sulfuric acid content. The acidic sulfuric acid generated by the side reaction is soluble in sulfuric acid and dissolves in water during the process without carbon dioxide absorption, affecting the accurate judgment of the process status and leading to higher measured results. Simultaneously, impurities present in the reaction gases may also significantly interfere with acidity detection, further reducing the accuracy of the measurement.

[0004] Chinese patent CN112129884A discloses a method for determining the sulfuric acid content in a sulfuric acid-nitric acid type stainless steel pickling solution. This method involves heating to expel nitric acid (tested with formaldehyde), then titrating with a standard sodium hydroxide solution using methyl orange as an indicator to calculate the sulfuric acid content. This method primarily determines the sulfuric acid content in sulfuric acid and nitric acid type stainless steel pickling solutions, but does not address the detection and analysis of free sulfuric acid in alkylation reaction effluents. The analysis focuses only on acidic liquid phases, making it unsuitable for analyzing gas-liquid mixed phases. Chinese patent CN109459430B proposes an acid-base titration device and method. Through the coordinated operation of a gravity sensor, stirring device, and control device, it significantly improves the accuracy and ease of operation. However, this method is mainly applicable to the detection of conventional liquid acid and base samples. It struggles to adapt to the complex interference caused by the multi-component, highly corrosive, and by-reaction products in sulfuric acid alkylation reaction effluents. Its overall applicability is limited, its anti-interference ability is insufficient, and it cannot meet the requirements for high-precision detection and analysis under complex operating conditions.

[0005] In summary, while existing technologies have made some progress in the detection and analysis of sulfuric acid content in the liquid phase, they still have significant shortcomings in the real-time, accurate, and interference-resistant detection of free sulfuric acid in alkylation reaction effluents, making it difficult to meet the actual needs of unit operation monitoring, product quality control, and dynamic process optimization. Therefore, developing a method for analyzing the free sulfuric acid content in reaction effluents with strong anti-interference capabilities, high operational stability, and applicability to complex operating conditions is of great significance for achieving refined operation management, safe and controllable monitoring of sulfuric acid alkylation units, and improving the quality of alkylation oil. Summary of the Invention

[0006] Purpose of the invention: To address the problems and shortcomings of existing technologies, this invention proposes a system and method for detecting and analyzing the sulfuric acid content in the effluent of sulfuric acid alkylation reactions. The aim is to achieve efficient and accurate detection and dynamic feedback of the free sulfuric acid content in the effluent under complex operating conditions, providing key support for monitoring the operating status of the equipment, monitoring the process, and controlling product quality.

[0007] The technical solution of this invention:

[0008] In a first aspect, the present invention provides a system for detecting and analyzing the sulfuric acid content in effluents from sulfuric acid alkylation reactions, the system comprising a sample acquisition and storage module, a sample pretreatment module, an acid-base titration detection module, and a data processing module.

[0009] In some embodiments, the sample collection and storage module includes a sampling cylinder and an ice-water bath; wherein the sampling cylinder has a volume of 100-150 mL and a pressure range of 2-20 MPa, and the ice-water bath has a water bath temperature of 1-5 ℃.

[0010] In some embodiments, the sample pretreatment module includes a reaction vessel, a polyethylene tube, a separatory funnel, and an analytical balance; wherein the reaction vessel and separatory funnel have a capacity of 100-250 mL.

[0011] In some embodiments, the acid-base titration detection module includes an alkaline burette, phenolphthalein indicator, and sodium hydroxide standard solution; wherein the phenolphthalein indicator is a 1% phenolphthalein ethanol solution.

[0012] In some embodiments, the data processing module includes a data processing unit; the data processing unit is used to calculate the sulfuric acid content based on the data obtained from acid-base titration and the formula for calculating the sulfuric acid content in the reaction effluent;

[0013] The calculation formula is as follows:

[0014] Formula 1

[0015] in, C 硫酸 This indicates the sulfuric acid content (mg / kg) in the reaction effluent.

[0016] C NaoH Indicates the concentration of the sodium hydroxide standard solution (mol / L);

[0017] V 0 represents the volume (mL) of sodium hydroxide standard solution consumed by the blank solution.

[0018] V * This indicates the volume (mL) of sodium hydroxide standard solution consumed in the extraction of the water sample.

[0019] M The molar mass (g / mol) of sulfuric acid (1 / 2H2SO4) is 49 g / mol.

[0020] V 3 indicates the volume (mL) of water sample extracted;

[0021] m Indicates the mass (g) of the sample introduced into the water;

[0022] V This represents the total volume of ultrapure water used for extraction. V 1 and V The total of 2 (mL).

[0023] Furthermore, the aforementioned V 1 is 80-120 mL, V 2 is 20-50 mL. V3 represents 10-30 mL of sodium hydroxide standard solution, with a concentration of C. NaoH The concentration is 0.01-0.05 mol / L.

[0024] In a second aspect, the present invention provides an analytical method using the above-described sulfuric acid content detection and analysis system, comprising the following steps:

[0025] S1: The sampling cylinder of the sample collection and storage module is used to perform pressurized closed sampling of the reaction effluent in the device. After sampling, the sample is stored in a cold and dark environment and then moved to the sample pretreatment module.

[0026] S2: Take V One volume of ultrapure water is placed in the reaction vessel of the sample pretreatment module. The sampling cylinder and the reaction vessel are placed in an ice-water bath for cooling. One end of a polyethylene tube is connected to the outlet of the cylinder, and the other end is placed below the ultrapure water level in the reaction vessel. The cylinder is slowly opened, and all the effluent sample is slowly introduced into the reaction vessel. The mass m of the sample introduced into the reaction vessel is determined by analytical balance and differential weighing method.

[0027] Then, take V 2% ultrapure water was used to rinse the inner wall of the sampling cylinder and the polyethylene tube. The rinsed liquid was poured into the reaction vessel to obtain a mixture. The entire mixture in the reaction vessel was transferred to a separatory funnel, shaken, and allowed to stand. The lower layer of water was taken as the extract water sample, and the volume of the extract water sample was recorded as . V 3;

[0028] S3: Perform acid-base titration on the extracted water sample. Add phenolphthalein indicator to the extracted water sample and titrate with a standardized sodium hydroxide standard solution. Record the volume of sodium hydroxide standard solution consumed to reach the titration endpoint. V * ;

[0029] S4: Calculate the sulfuric acid content in the reaction effluent using the data recorded in the above modules according to Formula 1.

[0030] In some embodiments, the reaction effluent is selected from one or more combinations of the following: DuPont's STRATCO indirect refrigeration process, Exxon Mobil's tandem stirred tank self-cooling process, CB&I Lummus's CDAlky low-temperature alkylation process, or Sinopec's SINOALKY sulfuric acid alkylation process.

[0031] In some embodiments, the blank solution is the same volume as the extracted water sample. V 3% ultrapure water, therefore V 0 = 0.

[0032] In some embodiments, the reaction effluent is a gas-liquid mixture.

[0033] In some embodiments, the temperature of the cold, dark environment in S1 is 3-5°C.

[0034] In some embodiments, the shaking time and settling time in S2 is 1-3 minutes and the settling time is 5-10 minutes.

[0035] Furthermore, when slowly introducing the entire effluent sample into the reaction vessel, the gas cylinder must be placed vertically above the conical flask with the outlet facing downwards, and the sample flow rate should be 0.5-1 mm. 3 / s.

[0036] In some embodiments, the titration endpoint is defined as the color of the extracted water sample changing from colorless to red and remaining red for 30 seconds without fading.

[0037] Beneficial effects:

[0038] 1. A high-precision detection method based on sample pretreatment and static stratification is constructed. By performing low-temperature pretreatment and static stratification on the reaction effluent, the interference of neutral sulfate esters, acidic sulfate esters and dissolved gases on the determination of free sulfuric acid content is effectively removed, significantly improving the detection accuracy and stability of free sulfuric acid content, and providing reliable data support for the control of sulfuric acid alkylation reaction conditions and acid consumption monitoring.

[0039] 2. The modular detection process enables efficient and convenient on-site analysis. This method does not rely on large instruments. By using standardized reagent titration combined with a simplified sample processing procedure, the detection cycle is significantly shortened and the detection efficiency is improved. It is suitable for rapid detection and feedback during the operation of industrial plants, enhancing the timeliness and safety of process control. It has broad industrial applicability and promotional value.

[0040] 3. To achieve standardized and traceable management of the quantitative analysis process, by standardizing the concentration of sodium hydroxide standard solution and the unified judgment standard of titration endpoint, combined with standardized calculation formulas, the results are guaranteed to have good repeatability and traceability. This is applicable to the periodic monitoring and operation status analysis of alkylation units, providing strong support for process optimization and safe and stable operation of the unit. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0042] Figure 1 This is a schematic flowchart of a method for detecting and analyzing the sulfuric acid content in the effluent of a sulfuric acid alkylation reaction, as described in an embodiment of the present invention. Detailed Implementation

[0043] 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.

[0044] Unless otherwise specified, all chemical reagents used in this invention are commercially available analytical grade reagents.

[0045] Example 1

[0046] For the detection and analysis of residual free sulfuric acid content of 20 mg / kg in sulfuric acid alkylation reaction effluents, a method and system for detecting and analyzing sulfuric acid content in sulfuric acid alkylation reaction effluents proposed in this invention are used. The system includes a sample acquisition and storage module, a sample pretreatment module, an acid-base titration detection module, and a data processing module. The process is as follows: Figure 1 As shown.

[0047] The sample collection and storage module includes a 150 mL sampling cylinder and an ice-water bath. The sampling cylinder has a pressure range of 2-20 MPa, and the ice-water bath has a water temperature of 4°C.

[0048] The sample pretreatment module includes a 250 mL conical flask, a polyethylene tube, a 250 mL separatory funnel, and an analytical balance.

[0049] The acid-base titration detection module includes an alkaline burette, phenolphthalein indicator, and sodium hydroxide standard solution; wherein the phenolphthalein indicator is a 1% phenolphthalein ethanol solution.

[0050] The data processing module includes a data processing unit, which calculates the sulfuric acid content based on the data obtained from acid-base titration and the formula for calculating the sulfuric acid content in the reaction effluent.

[0051] The calculation formula is as follows:

[0052] Formula 1

[0053] in, C 硫酸 This indicates the sulfuric acid content (mg / kg) in the reaction effluent.

[0054] C NaoH The concentration of the sodium hydroxide standard solution is expressed in mol / L; in this example, it is 0.01 mol / L.

[0055] V 0 represents the volume (mL) of sodium hydroxide standard solution consumed by the blank solution.

[0056] V* This indicates the volume (mL) of sodium hydroxide standard solution consumed in the extraction of the water sample.

[0057] M The molar mass (g / mol) of sulfuric acid (1 / 2H2SO4) is 49 g / mol.

[0058] V 3 indicates the volume (mL) of water sample extracted;

[0059] m Indicates the mass (g) of the sample introduced into the water;

[0060] V This represents the total volume of ultrapure water used for extraction. V 1 and V The total of 2 (mL).

[0061] In this embodiment, the specific steps of the sulfuric acid content detection and analysis method include:

[0062] A sampling cylinder was used to perform pressurized, sealed sampling of the reaction effluent from the apparatus. After sampling, the sample was stored in a cool, dark environment at 4 °C, and the determination was completed within 24 hours of sampling. V 1= 100 mL of ultrapure water is placed in a 250 mL Erlenmeyer flask. The sampling cylinder and the Erlenmeyer flask are placed in a 0°C ice-water bath to cool them and prevent liquid phase evaporation. One end of a polyethylene tube is connected to the outlet of the cylinder, and the other end is placed below the ultrapure water level in the Erlenmeyer flask. The cylinder is slowly opened, and the flow rate is 1 mm / s. 3 The entire effluent sample was passed into water at a rate of / s, and the mass of the sample passed into the water was determined using an analytical balance and the differential weighing method. m= 180 g; then, select V Using 50 mL of ultrapure water as the rinsing solution, rinse the inner wall of the sampling cylinder and the polyethylene tube. Pour the rinse solution into an Erlenmeyer flask to obtain a mixture. Transfer the entire mixture from the Erlenmeyer flask to a separatory funnel, shake for 2 minutes, let stand for 5 minutes, and then extract the lower layer. V 20 mL of water sample was placed in a clean 250 mL Erlenmeyer flask as the extraction water sample. Three drops of phenolphthalein indicator were added to the extraction water sample, and titration was performed using a standardized sodium hydroxide solution. The titration endpoint was reached when the color of the extraction water sample changed from colorless to red and remained so for 30 seconds. The volume of sodium hydroxide standard solution consumed in the extraction of the water sample was recorded. V * =1 mL. The volume of sodium hydroxide standard solution consumed by the blank solution. V 0 = 0 mL.

[0063] Based on the data obtained from the above steps, the sulfuric acid content in the reaction effluent was calculated to be 20.42 mg / kg according to the formula, with a deviation rate of 2.1%, which meets the requirement of a measurement deviation of <5% in production.

[0064] Comparative Example 1

[0065] For the detection and analysis of residual free sulfuric acid content of 20 mg / kg in the effluent of sulfuric acid alkylation reaction, this comparative example adopts a conventional instrument detection method, namely, the method of determining sulfate content by liquid chromatography-ion chromatography, to detect and analyze the sulfuric acid content in the effluent of sulfuric acid alkylation reaction, including sample collection and storage module, sample pretreatment module, and instrument measurement module.

[0066] The sample collection and storage module and the sample pretreatment module are similar to those in Example 1.

[0067] The calculation formula is as follows:

[0068] Formula 2

[0069] in, C 硫酸 This indicates the sulfuric acid content (mg / kg) in the reaction effluent.

[0070] c Indicates sulfate concentration (mg / L);

[0071] m Indicates the mass (g) of the sample introduced into the water;

[0072] V 3 indicates the volume (mL) of water sample extracted;

[0073] In this comparative example, the specific steps of the sulfuric acid content detection and analysis method include:

[0074] Open sampling bottles were used to sample the reaction effluent from the apparatus in a non-sealed manner. After sampling, the samples were stored at room temperature, and the determination was ensured to be completed within 24 hours of sampling. V 3=100 mL of ultrapure water was placed in a 250 mL Erlenmeyer flask, and the mass of the sample in the open sampling bottle was... m A 10 g effluent sample was completely passed into ultrapure water. The mixture was placed in a 250 ml separatory funnel, shaken thoroughly for 5 min, and allowed to stand for 5 min. The lower layer sample was then analyzed by liquid chromatography-ion chromatography to determine the sulfate concentration. c =2.55mg / L.

[0075] Based on the data obtained from the above steps, the sulfuric acid content in the reaction effluent calculated according to the formula is 25.50 mg / kg, with a deviation rate of 27.5%, which does not meet the requirements for determination in production.

[0076] By analyzing the sulfuric acid content in the reaction effluent obtained by the method described in this patent (Example 1) and the conventional instrument detection method (Comparative Example 1), the accuracy of the method described in the patent is 25.4% higher than that of the conventional method. This indicates that by taking samples from a gas cylinder under pressure and performing closed sampling, acid-base titration, and other steps, the true material state of the sulfuric acid alkylation reaction effluent can be accurately determined, and the influence of other interfering substances can be effectively reduced, thereby significantly improving the accuracy and stability of the detection of free sulfuric acid content.

[0077] This invention can also be implemented in various other ways. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A system for detecting and analyzing the amount of sulfuric acid in a stream of an alkylated sulfuric acid reaction effluent, comprising: The analysis system comprises a sample collection and storage module, a sample pretreatment module, an acid-base titration detection module and a data processing module. The sample collection and storage module comprises a sampling steel bottle and an ice water bath device. The sample pretreatment module comprises a reaction container, a polyethylene tube, a separatory funnel and an analytical balance. The acid-base titration detection module comprises an alkaline burette, a phenolphthalein indicator and a sodium hydroxide standard solution. The data processing module comprises a data processing unit, which is used to calculate the sulfuric acid content according to the data obtained by acid-base titration and a calculation formula of the sulfuric acid content in the reaction effluent. The calculation formula is as follows: Formula 1 wherein, C 硫酸 represents the sulfuric acid content in the reaction effluent in mg / kg; C NaoH represents the concentration of the sodium hydroxide standard solution, in units of mol / L; V 0 represents the volume of sodium hydroxide standard solution consumed by the blank solution, in mL; V * VNaOH represents the volume of sodium hydroxide standard solution used for extraction of the water sample, in mL; M Molar mass of 1 / 2 sulfuric acid in g / mol, 49 g / mol; V 3 represents the volume of the extracted water sample, in mL; m represents the mass of the sample introduced into water, unit: g; V represents the total volume of ultrapure water used for extraction, in mL; and V 1 and V 2 are the total volume of ultrapure water used for extraction, in mL. The V 1 80-120 mL, V 2 20-50 mL, V 3 10-30 mL; the concentration C of the standard solution of sodium hydroxide NaoH 0.01-0.05 mol / L; The test method of the above system comprises the following steps: S1: using the sampling steel bottle of the sample collection and storage module to take pressure-closed sampling of the reaction effluent in the device, storing the sample in a cold and dark environment after sampling, and moving the sample to the sample pretreatment module; S2: take V 1 Put the volume of ultrapure water into the reaction vessel of the sample pretreatment module, and cool the sampling steel cylinder and the reaction vessel in an ice water bath. Connect one end of a polyethylene tube to the outlet of the steel cylinder and the other end to the ultrapure water in the reaction vessel below the water level. Slowly open the steel cylinder, and slowly pass the effluent sample into the reaction vessel. Determine the mass m of the sample passed into the reaction vessel by using an analytical balance and the subtraction weighing method. Then, take V 2 ultrapure water, rinse the inner wall of the sampling steel cylinder and the polyethylene tube, pour the rinsed liquid into the reaction container to obtain a mixed liquid; transfer all the mixed liquid in the reaction container to a separatory funnel, shake and stand, take the lower layer water sample as the extracted water sample, and record the volume of the extracted water sample as V 3 ; S3: The extracted water sample is subjected to acid-base titration detection, phenolphthalein indicator is added to the extracted water sample, and the volume of sodium hydroxide standard solution consumed by the extracted water sample to reach the titration end point is recorded V * ; S4: calculating the sulfuric acid content in the reaction effluent according to formula 1 according to the data recorded by the sample pretreatment module and the acid-base titration detection module.

2. The detection assay system of claim 1, wherein, The volume of the sampling steel bottle is 100-150 mL, the pressure bearing range is 2-20 Mpa, and the water bath temperature of the ice water bath device is 1-5 ℃.

3. The method of claim 1 or 2, wherein the method is applied to the analysis system for detecting the amount of sulfuric acid in the effluent of the alkylation reaction of sulfuric acid, characterized in that, The test method comprises the following steps: S1: using the sampling steel bottle of the sample collection and storage module to take pressure-closed sampling of the reaction effluent in the device, storing the sample in a cold and dark environment after sampling, and moving the sample to the sample pretreatment module; S2: take V 1 Put the volume of ultrapure water in the reaction vessel of the sample pretreatment module, and cool the sampling steel cylinder and the reaction vessel in an ice water bath. Connect one end of a polyethylene tube to the outlet of the steel cylinder and the other end to the ultrapure water level in the reaction vessel. Slowly open the steel cylinder, and slowly pass the effluent sample into the reaction vessel. Determine the mass m of the sample passed into the reaction vessel by using an analytical balance and difference subtraction weighing method. Then, take V 2 ultrapure water, rinse the inner wall of the sampling steel cylinder and the polyethylene tube, pour the rinsed liquid into the reaction container to obtain a mixed liquid; transfer all the mixed liquid in the reaction container to a separatory funnel, shake and stand, take the lower layer water sample as the extracted water sample, and record the volume of the extracted water sample as V 3 ; S3: The extracted water sample is subjected to acid-base titration detection, phenolphthalein indicator is added to the extracted water sample, the calibrated sodium hydroxide standard solution is used for titration, and the volume of the sodium hydroxide standard solution consumed by the extracted water sample to reach the titration end point is recorded V * ; S4: calculating the sulfuric acid content in the reaction effluent according to formula 1 according to the data recorded by the sample pretreatment module and the acid-base titration detection module.

4. The detection method according to claim 3, characterized in that, The reaction effluent in S1 is a gas-liquid mixed phase, and the temperature of the cold and dark environment is 3-5 ℃.

5. The detection method according to claim 3, characterized by, The shaking time of the shaking and standing in S2 is 1-3 min, and the standing time is 5-10 min. The shaking time of the shaking and standing in S2 is 1-3 min, and the standing time is 5-10 min.

6. The detection method according to claim 3, characterized in that, The sample flow rate when the effluent sample is passed into the reaction vessel entirely slowly is 0.5-1 mm 3 / s.

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