Alkyl naphthalene sulfonate antirust agent produced through methyl naphthalene alkylation

Abstract

The embodiment of the invention provides an alkyl naphthalene sulfonate antirust agent produced through methylnaphthalene alkylation, and relates to the technical field of synthesis of petroleum sulfonate antirust agents. A method for producing an alkyl naphthalene sulfonate antirust agent through methylnaphthalene alkylation comprises the following steps: adding high-purity methylnaphthalene into a reaction kettle, adding a Lewis acid catalyst, uniformly stirring and mixing, slowly adding C9-C12 olefin into a reaction system in a dropwise adding manner under a stirring condition, dropwise adding for 30 minutes to 2 hours, and after the dropwise adding is finished, cooling to room temperature to obtain the alkyl naphthalene sulfonate antirust agent. After the dropwise adding is finished, continuously keeping the temperature, stirring and reacting for 2-4 hours, and cooling to room temperature after the reaction is finished, so as to obtain a reaction mixture containing alkyl naphthalene. The alkyl naphthalene sulfonate with clear components, high purity and excellent anti-rust performance is prepared by optimizing the molar ratio and reaction conditions of methylnaphthalene and olefin and combining an efficient purification process, green and efficient preparation of the anionic surfactant with controllable raw materials and stable quality is realized, and the method has a good industrial application prospect.

Description

Technical Field

[0001] This application relates to the field of petroleum sulfonate rust inhibitors, and more specifically, to the production of alkylnaphthalene sulfonate rust inhibitors by methylnaphthalene alkylation. Background Technology

[0002] Methylnaphthalene, as an important organic chemical intermediate, has broad application prospects in oil extraction, printing and dyeing, textiles, liquid crystals, and thermal conductive materials. With the continuous growth of C10 aromatic hydrocarbon production, the raw material supply of methylnaphthalene is becoming increasingly abundant, providing strong support for its large-scale production and downstream high-value utilization. Against this backdrop, developing high-value-added downstream products of methylnaphthalene and promoting its green and sustainable development has become an important direction in the fine chemical industry.

[0003] Given this trend, we can see that the downstream application industries of methylnaphthalene can also develop well. The application of surfactants in the field of rust prevention is mainly achieved by forming a protective film and inhibiting the contact of corrosive media with the metal surface. Among the many surfactants, anionic surfactants are the most widely and deeply studied and applied. At present, the high-performance anionic surfactants are petroleum sulfonates and heavy alkylbenzene sulfonates (HABS). However, the above-mentioned anionic surfactants are all made from by-products, but their raw materials are mostly derived from petroleum by-products, with complex components and poor batch stability, making it difficult to control product quality.

[0004] Therefore, developing a novel anionic rust inhibitor with a clear source of raw materials, a well-defined structure, and stable and efficient performance has become a current research hotspot. Given the structural similarity between alkylated methylnaphthalene and heavy alkylbenzene, it is speculated that the alkylnaphthalene sulfonate obtained after sulfonation should have good interfacial activity and metal protection capabilities. Alkylnaphthalene sulfonate can be prepared through steps such as alkylation, sulfonation, neutralization, and purification. It has already been applied in fields such as oil extraction, but the existing process still needs to be improved in terms of reaction selectivity, product purity, and process controllability. Summary of the Invention

[0005] The production of alkylnaphthalene sulfonate rust inhibitors by methylnaphthalene alkylation according to embodiments of this application includes the following steps: S1. Add high-purity methylnaphthalene to the reaction vessel, add Lewis acid catalyst, stir and mix evenly, and slowly add C9–C12 olefin to the reaction system dropwise under stirring conditions. The dropwise addition time is 30 minutes to 2 hours. After the dropwise addition is completed, continue to keep warm and stir the reaction for 2 to 4 hours. After the reaction is completed, cool to room temperature to obtain a reaction mixture containing alkylnaphthalene. S2. Wash the reaction mixture obtained in step S1 with dilute acid to separate and remove catalyst residue and water-soluble byproducts, retain the organic phase, and dry the organic phase to obtain a pure alkylnaphthalene intermediate. S3. Transfer the alkylnaphthalene intermediate obtained in step S2 to a sulfonation reactor. Slowly add fuming sulfuric acid dropwise to the reactor at 0°C to 40°C, stirring continuously during the dropwise addition. After the dropwise addition is completed, keep the reactor at the same temperature range and stir for 1 to 2 hours to obtain the sulfonation reaction mixture. S4. Transfer the sulfonated reaction mixture obtained in step S3 to a settling container and let it stand at room temperature for more than 4 hours to allow the reaction system to separate into layers. Separate and remove the lower waste acid phase and retain the upper organic phase. S5. Wash the organic phase obtained in step S4 with deionized water once until the aqueous phase is neutral, and then dry the washed organic phase. S6. Add an alkaline aqueous solution to the dried organic phase obtained in step S5, and carry out a neutralization reaction while stirring at 20℃~50℃. Control the feeding rate until the pH value of the reaction system reaches 7.0~9.0 to obtain a neutralized alkylnaphthalene sulfonate solution. S7. The solution obtained in step S6 is passed through a solid-liquid separation device to remove insoluble impurities, and the filtrate is collected to obtain the alkyl naphthalene sulfonate product.

[0006] Furthermore, the methylnaphthalene in step S1 has a purity of not less than 95%, and is at least one of α-methylnaphthalene or β-methylnaphthalene, and the molar ratio of methylnaphthalene to C9–C12 olefin is 1:1.5 to 1:2.5.

[0007] Furthermore, in step S1, the C9–C12 olefin is any one or more of nonene, decene, or undecene, and its carbon chain structure is straight or has a methyl branch. The C9–C12 olefin is added dropwise in a constant flow manner, with a dropping rate of 10%–20% of the total olefin mass added per hour.

[0008] Furthermore, in step S1, the Lewis acid catalyst is at least one of anhydrous aluminum trichloride, boron trifluoride diethyl ether complex, ferric chloride, or zirconium sulfate.

[0009] Furthermore, in step S1, the amount of Lewis acid catalyst used is 5%–15% of the mass of methylnaphthalene.

[0010] Furthermore, in step S1, the reaction temperature is controlled between 40°C and 60°C. During the reaction, the temperature is adjusted by external cooling and heating devices, and a mechanical stirring device is used for stirring.

[0011] Furthermore, the SO3 content in the fuming sulfuric acid used in step S3 is 10%–30%, and the amount of fuming sulfuric acid added is measured as 1.05–1.2 times the number of aromatic rings in the alkylnaphthalene.

[0012] Furthermore, in step S4, after the sulfonated reaction mixture separates into layers, the lower waste acid phase is separated and removed using a separatory funnel.

[0013] Furthermore, the alkaline aqueous solution used in step S6 is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a concentration of 10%–30%.

[0014] Furthermore, in step S7, the neutralized solution is centrifuged using a centrifuge to separate the supernatant or filtrate, thereby obtaining the alkylnaphthalene sulfonate product.

[0015] The beneficial effects of this application are: by controlling the molar ratio of methylnaphthalene to nonene to be 1:2 and the reaction temperature to be 50℃, the conversion rate of the alkylation reaction is improved, the generation of by-products is reduced, and a structurally well-defined and quality-stable alkylnaphthalene intermediate is obtained. This lays a good foundation for subsequent sulfonation reactions and the preparation of high-performance alkylnaphthalene sulfonates. High-purity α- or β-methylnaphthalene is reacted with C9–C12 olefins under Lewis acid catalysis, combined with processes such as dilute acid washing, drying, low-temperature dropwise addition of fuming sulfuric acid for sulfonation, static sedimentation and separation, neutralization, and centrifugal filtration. These processes effectively remove catalyst residues, waste acid, and insoluble matter, resulting in alkylnaphthalene sulfonate products with clear components. With high purity and excellent interfacial properties, this product possesses good oil solubility and metal surface adsorption capacity, forming a dense hydrophobic film that effectively isolates moisture and oxygen. It exhibits stable and reliable rust prevention performance, and its mild processing conditions ensure safe operation and simple post-processing, making it suitable for large-scale production. Leveraging abundant C10 aromatic resources and a stable supply of methylnaphthalene, this invention achieves the efficient preparation of anionic surfactants with clearly defined raw material sources and controllable product quality. It overcomes the quality fluctuation problems caused by raw material by-products in traditional petroleum sulfonates or heavy alkylbenzene sulfonates, promoting the downstream application of methylnaphthalene towards a green and sustainable direction, and has significant industrial application value and market prospects.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the overall steps according to an embodiment of this application; Figure 2 This is a flowchart of the alkylation reaction according to an embodiment of this application; Figure 3 This is a flowchart of the sulfonation reaction according to an embodiment of this application. Detailed Implementation

[0019] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0020] The following describes, with reference to the accompanying drawings, an embodiment of the present application for the production of an alkylnaphthalene sulfonate rust inhibitor by methylnaphthalene alkylation.

[0021] like Figures 1 to 3 As shown in the embodiments of this application, the production of alkylnaphthalene sulfonate rust inhibitors by methylnaphthalene alkylation includes the following seven key steps: alkylation reaction, dilute acid washing and drying, sulfonation reaction, precipitation and acid separation, water washing and drying, neutralization reaction, and solid-liquid separation. By systematically optimizing the reaction raw material ratio, temperature control, catalyst selection, and multi-stage post-processing, the stable preparation of high-conversion, low-by-product, and high-purity alkylnaphthalene sulfonate products is achieved. It is suitable for laboratory research and industrial continuous production, and is especially suitable for the preparation of high-performance rust inhibitors, lubricant dispersants, and oilfield chemicals.

[0022] S1, Alkylation reaction In this embodiment, the alkylation reaction is the core step in preparing the high-performance alkylnaphthalene intermediate. High-purity methylnaphthalene is added to the reaction vessel, preferably using at least one of α-methylnaphthalene or β-methylnaphthalene with a purity of not less than 95% as the starting material to ensure the selectivity of subsequent reactions and the controllability of the product structure. A Lewis acid catalyst is added to the reaction vessel and mixed evenly under stirring. The Lewis acid catalyst is selected from at least one of anhydrous aluminum trichloride (AlCl3), boron trifluoride diethyl ether complex (BF3·OEt2), ferric chloride (FeCl3), or zirconium sulfate. In this preferred embodiment, anhydrous aluminum trichloride is used as the catalyst, and its amount is 5%–15% of the mass of methylnaphthalene, more preferably 10%.

[0023] The temperature of the reaction system is controlled to rise to 40℃~60℃, preferably 50℃. The temperature is precisely controlled by an external cooling and heating device to prevent local overheating caused by exothermic reaction. Under continuous mechanical stirring, the C9-C12 olefin is slowly added to the reaction system dropwise for 30 minutes to 2 hours. The C9-C12 olefin is any one or more of nonene, decene or undecene, and its carbon chain structure is straight chain or has a methyl branch.

[0024] In this embodiment, nonene was selected as the alkylating agent and added dropwise in a constant flow manner. The dropping rate was 10%–20% of the total olefin mass added per hour, preferably 15%.

[0025] The molar ratio of methylnaphthalene to C9–C12 olefins was controlled between 1:1.5 and 1:2.5. Through systematic experimental studies, it was found that the optimal reaction effect could be obtained when the molar ratio of methylnaphthalene to nonene was 1:2 and the reaction temperature was 50℃. After the addition was completed, the reaction was continued to be stirred at the temperature for 2 to 4 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a reaction mixture containing alkylnaphthalene.

[0026] To ensure the safety of the reaction, the entire alkylation process should be carried out under nitrogen protection. The reaction apparatus should be pre-dried and purged with nitrogen three times to avoid moisture causing violent hydrolysis of the catalyst, heat decomposition, or even a spraying accident. The reactor should be made of glass-lined glass or 316L stainless steel and equipped with a high-efficiency mechanical stirrer (200–500 rpm) to ensure uniform mass transfer.

[0027] To verify the rationality of the above process parameters, a systematic optimization experiment was conducted. The experimental results are shown in Tables 1 and 2. Table 1 shows the experimental results for preparing alkylnaphthalenes at different naphthalene-to-olefin ratios.

[0028] Table 2 shows the experimental results for the preparation of alkylnaphthalenes at different reaction temperatures.

[0029] Conversion rate and byproduct data were determined by gas chromatography (GC). Chromatographic conditions: DB-5 capillary column (30m×0.32mm×0.25μm), injection port temperature 300℃, detector (FID) temperature 320℃, temperature program: 80℃ held for 2 min, increased to 280℃ at 10℃ / min, held for 10 min, and the sample was diluted with toluene before injection.

[0030] Experimental data show that at a molar ratio of 1:2 and a reaction temperature of 50℃, the conversion rate of methylnaphthalene is as high as 99.21%, the conversion rate of nonene is 98.52%, and the proportion of by-products is the lowest (4.56%). This indicates that the conditions can achieve a balance between high conversion rate and low side reaction, which is conducive to the generation of alkylnaphthalene intermediates with well-defined structure and stable quality. This lays a good foundation for subsequent sulfonation reactions and the preparation of high-performance alkylnaphthalene sulfonates.

[0031] The obtained alkylnaphthalene intermediate was subjected to 1 H-NMR (400MHz, CDCl3) confirmed the presence of a characteristic —CH2— peak at δ2.8–3.1ppm, indicating the successful introduction of the alkyl group into the aromatic ring, with a target product yield ≥95%.

[0032] S2, dilute acid washing and drying The reaction mixture obtained in step S1 is transferred to a separatory apparatus and washed with dilute acid (such as 5%–10% dilute hydrochloric acid or dilute sulfuric acid) to remove unreacted catalyst residues (such as AlCl3 hydrolysis products) and water-soluble byproducts.

[0033] After thorough stirring, allow the mixture to stand and separate into layers. Separate and discard the lower aqueous phase, retaining the upper organic phase. Then, dry the organic phase, preferably using anhydrous sodium sulfate or anhydrous magnesium sulfate as a drying agent. The drying time is 0.5-2 hours until the moisture is completely removed, yielding a pure alkylnaphthalene intermediate.

[0034] S3, sulfonation reaction The alkylnaphthalene intermediate obtained in step S2 is transferred to a three-necked flask and placed in an ice-water bath or a constant temperature cooling device. The reaction temperature is controlled within the range of 0°C to 40°C, preferably 20°C to 30°C.

[0035] Fuming sulfuric acid is slowly added dropwise under continuous stirring. The dropping rate is strictly controlled during the process to avoid local overheating that could lead to oversulfonation or coking reactions.

[0036] The SO3 content in the fuming sulfuric acid is 10%–30%, preferably 20%, and its addition amount is measured as 1.05–1.2 times the molar number of aromatic rings in the alkylnaphthalene to ensure that the sulfonation reaction proceeds fully. After the addition is completed, the mixture is kept at the same temperature and stirred for 1 to 2 hours to obtain the sulfonation reaction mixture.

[0037] The dropping rate should be controlled at 1-2 mL per minute, and the total dropping time should be no less than 60 minutes. Nitrogen gas should be continuously introduced during the reaction to prevent the fuming sulfuric acid from absorbing moisture or oxidizing. The reaction apparatus should be equipped with a corrosion-resistant dropping funnel (PTFE piston) and an acid-resistant stirring paddle.

[0038] S4, Sedimentation Acid The sulfonated reaction mixture obtained in step S3 is transferred to a settling container and allowed to settle at room temperature for at least 4 hours, preferably 6–8 hours, to allow the system to fully separate into layers.

[0039] The upper layer is an organic phase containing alkyl naphthalene sulfonic acid, and the lower layer is a waste acid phase (mainly unreacted sulfuric acid and some hydrolysis products). After separation, the lower waste acid phase is separated and removed by a separating funnel or an automatic acid discharge device, while the upper organic phase is retained, thus achieving effective separation and recycling of waste acid.

[0040] Waste acid can be concentrated to over 70% and reused in other sulfonation processes, or handed over to qualified units for treatment, which meets environmental protection requirements.

[0041] S5. Washing and Drying Wash the organic phase obtained in step S4 with deionized water once or multiple times while stirring until the aqueous phase is neutral (pH≈7) to remove residual trace acidic substances.

[0042] After separating the aqueous phase, the organic phase is dried again using anhydrous sodium sulfate or molecular sieve for 0.5–2 hours to obtain the dried sulfonated product.

[0043] S6, neutralization reaction Slowly add an alkaline aqueous solution to the dried organic phase obtained in step S5, and carry out a neutralization reaction while stirring at 20℃~50℃.

[0044] The alkaline aqueous solution is a 10%–30% sodium hydroxide or potassium hydroxide aqueous solution, preferably a 20% NaOH solution. The feeding rate is controlled to avoid violent exothermic reactions until the pH value of the reaction system reaches 7.0–9.0, preferably 8.0, to obtain a neutralized alkylnaphthalene sulfonate solution.

[0045] The neutralization process is significantly exothermic, so it is recommended to carry it out under jacket cooling and control the temperature rise to no more than 10°C.

[0046] S7: Solid-liquid separation The solution obtained in step S6 is passed through a solid-liquid separation device to remove any possible insoluble impurities (such as trace amounts of inorganic salts or polymers), and the filtrate is collected to obtain the alkyl naphthalene sulfonate product.

[0047] In this embodiment, a centrifuge is used for centrifugation at a speed of 6000–8000 rpm for 10–30 minutes. The supernatant (i.e., filtrate) is collected to avoid precipitates from mixing into the final product. The resulting alkylnaphthalene sulfonate product is a brownish-yellow to dark brown liquid with good oil solubility and surface activity. It can be directly used in industrial fields such as rust inhibitors, lubricating additives, or oil extraction aids.

[0048] The product was detected by infrared spectroscopy at 1170 cm⁻¹. -1 and 1035cm -1 Typical S=O and S-O stretching vibration peaks were observed, confirming the successful introduction of sulfonic acid groups. The rust-preventive performance was verified by the GB / T10125-2012 salt spray test (5% NaCl, 36℃, 24h), showing no rust.

[0049] The preparation method of this application achieves efficient and stable conversion from raw materials to final products through systematic optimization and synergistic effects among the various steps. The alkylation reaction is efficiently catalyzed by the aforementioned Lewis acid catalyst at the preferred molar ratio and temperature, which not only achieves high conversion rate but also ensures the regularity and consistency of the molecular structure of the alkylnaphthalene intermediate. This is the structural basis for obtaining high-performance final products. The subsequent dilute acid washing effectively removes catalyst residues and ionic impurities, avoiding their poisoning effect on the subsequent sulfonation reaction and their adverse effects on the rust prevention performance of the final product.

[0050] The critical sulfonation reaction was carried out under strict control with low temperature, slow dropwise addition, and nitrogen protection, which effectively suppressed side reactions such as over-sulfonation, oxidation, and coking. This ensured that the sulfonic acid group was accurately introduced into the aromatic ring of the alkylnaphthalene, generating a well-defined monosulfonic acid product. Subsequent multi-stage purification steps (precipitation, acid separation, water washing, and drying) gradually separated and removed the waste acid and residual acidic substances generated in the reaction, creating a pure reaction environment for the neutralization reaction and avoiding the generation of inorganic salt impurities. Finally, through solid-liquid separation, any insoluble particles that might be present in the system were removed, resulting in a clear, homogeneous, and stable alkylnaphthalene sulfonate product.

[0051] The above process flow is reasonably designed, with close connection between unit operations, mild and controllable process conditions, and parameters of each step have been fully optimized through experiments. It has good repeatability and feasibility for scale-up, and is particularly suitable for the large-scale continuous production of high-performance rust inhibitors, lubricating oil additives and oilfield chemicals.

[0052] Example 1 Add 100g of β-methylnaphthalene with a purity ≥95% to a 500mL three-necked flask. The flask is equipped with a mechanical stirrer (paddle stirrer), a constant pressure dropping funnel, a digital thermometer, and a nitrogen inlet tube. The reaction apparatus is dried at 110℃ for 2 hours and purged with nitrogen three times to ensure that the system is anhydrous and oxygen-free.

[0053] Start stirring at 300 rpm, add 10 g of anhydrous aluminum trichloride (10% of the mass of methylnaphthalene), stir for 10 minutes to disperse the catalyst evenly, place the reaction system in a constant temperature water bath, heat to 50°C and maintain constant temperature.

[0054] Under continuous stirring and nitrogen protection, 92g of nonene (the molar ratio of methylnaphthalene to nonene is 1:2) was slowly added to the system by a constant flow pump at a rate of 15% of the total olefin mass per hour. The addition time was controlled at about 67 minutes (i.e., 1 hour and 7 minutes). The reaction temperature was monitored during the addition process, and the temperature rise was controlled to not exceed ±2℃ by external cold water circulation.

[0055] After the addition is complete, continue stirring at 50°C for 3 hours to allow the alkylation reaction to proceed fully. After the reaction is complete, allow it to cool naturally to room temperature to obtain a dark red to brownish-red viscous liquid, which is the reaction mixture containing alkylnaphthalene.

[0056] The above reaction mixture was transferred to a separatory funnel, 100 mL of 5% dilute hydrochloric acid was added, and the mixture was stirred for 10 minutes and allowed to stand to separate into layers. The lower aqueous phase was discarded, and the mixture was washed once more. The organic phases were combined, and 20 g of anhydrous sodium sulfate was added to dry the mixture for 2 hours. After filtration, a pure alkylnaphthalene intermediate was obtained with a yield ≥95%.

[0057] Take 80g of the above alkylnaphthalene intermediate and transfer it to another 500mL three-necked flask. Place it in an ice-water bath equipped with a mechanical stirrer, a dropping funnel, and a temperature sensor. Start the stirrer and set the speed to 400rpm. Adjust the cooling bath to stabilize the temperature of the reaction system at 25℃.

[0058] Under stirring conditions, slowly add 45g of fuming sulfuric acid (SO3 content 20%, measured as 1.1 times the molar number of aromatic rings) dropwise at a rate of 1-2mL per minute for about 90 minutes. During the addition process, closely monitor the reaction temperature to ensure it does not exceed 40℃.

[0059] After the addition is complete, maintain the temperature at 25–30℃ and stir for 1.5 hours to carry out the sulfonation aging reaction, and obtain a dark brown viscous sulfonated reaction mixture.

[0060] The sulfonated product was transferred to a settling container and allowed to settle at room temperature for 6 hours. The system was clearly divided into two layers: the upper layer was a reddish-brown organic phase (containing alkyl naphthalene sulfonic acid), and the lower layer was a dark brown waste acid phase. The lower waste acid phase was separated and discarded by a separatory funnel, while the upper organic phase was retained.

[0061] The organic phase was washed twice with 100 mL of deionized water each time. After stirring, the phase was allowed to stand and separate until the aqueous phase was neutral (pH≈7). After separating the aqueous phase, 10 g of anhydrous sodium sulfate was added and dried for 1 hour. The dried sulfonated product was then obtained by filtration.

[0062] The dried sulfonated product was heated to 40°C, and about 35g of 20% NaOH aqueous solution was slowly added dropwise while stirring. The pH was controlled to rise to 8.0. The neutralization reaction was exothermic, and the temperature rise was controlled to not exceed 10°C by jacket cooling to obtain the neutralized alkylnaphthalene sulfonate solution.

[0063] The neutralized solution was transferred to a centrifuge and centrifuged at 7000 rpm for 20 minutes. The supernatant was collected to obtain the alkyl naphthalene sulfonate rust inhibitor product.

[0064] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0065] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A methylnaphthalene alkylation process for producing alkylnaphthalene sulfonate rust inhibitors, characterized in that, Includes the following steps: S1. Add high-purity methylnaphthalene to the reaction vessel, add Lewis acid catalyst, stir and mix evenly, and slowly add C9-C12 olefins to the reaction system dropwise under stirring conditions. The dropwise addition time is 30 minutes to 2 hours. After the dropwise addition is completed, continue to keep warm and stir the reaction for 2 to 4 hours. After the reaction is completed, cool to room temperature to obtain a reaction mixture containing alkylnaphthalene. S2. Wash the reaction mixture obtained in step S1 with dilute acid to separate and remove catalyst residue and water-soluble byproducts, retain the organic phase, and dry the organic phase to obtain a pure alkylnaphthalene intermediate. S3. Transfer the alkylnaphthalene intermediate obtained in step S2 to a sulfonation reactor. Slowly add fuming sulfuric acid dropwise to the reactor at 0°C to 40°C, stirring continuously during the dropwise addition. After the dropwise addition is completed, keep the reactor at the same temperature range and stir for 1 to 2 hours to obtain the sulfonation reaction mixture. S4. Transfer the sulfonated reaction mixture obtained in step S3 to a settling container and let it stand at room temperature for more than 4 hours to allow the reaction system to separate into layers. Separate and remove the lower waste acid phase and retain the upper organic phase. S5. Wash the organic phase obtained in step S4 with deionized water once until the aqueous phase is neutral, and then dry the washed organic phase. S6. Add an alkaline aqueous solution to the dried organic phase obtained in step S5, and carry out a neutralization reaction while stirring at 20℃~50℃. Control the feeding rate until the pH value of the reaction system reaches 7.0~9.0 to obtain a neutralized alkylnaphthalene sulfonate solution. S7. The solution obtained in step S6 is passed through a solid-liquid separation device to remove insoluble impurities, and the filtrate is collected to obtain the alkyl naphthalene sulfonate product.

2. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, The methylnaphthalene in step S1 has a purity of not less than 95% and is at least one of α-methylnaphthalene or β-methylnaphthalene, and the molar ratio of methylnaphthalene to C9–C12 olefin is 1:1.5 to 1:2.

5.

3. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, In step S1, the C9–C12 olefin is any one or more of nonene, decene, or undecene, and its carbon chain structure is a straight chain or has a methyl branch. The C9–C12 olefin is added dropwise in a constant flow manner, and the dropping rate is 10%–20% of the total olefin mass added per hour.

4. The alkylnaphthalene alkylation process for producing alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, In step S1, the Lewis acid catalyst is at least one of anhydrous aluminum trichloride, boron trifluoride diethyl ether complex, ferric chloride, or zirconium sulfate.

5. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, In step S1, the amount of Lewis acid catalyst used is 5%-15% of the mass of methylnaphthalene.

6. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, In step S1, the reaction temperature is controlled between 40°C and 60°C. During the reaction, the temperature is adjusted by external cooling and heating devices, and a mechanical stirring device is used for stirring.

7. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, The SO3 content in the fuming sulfuric acid used in step S3 is 10%-30%, and the amount of fuming sulfuric acid added is measured as 1.05-1.2 times the number of aromatic rings in the alkylnaphthalene.

8. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, In step S4, after the sulfonated reaction mixture separates into layers, it is separated by a separatory funnel and the lower waste acid phase is removed.

9. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, The alkaline aqueous solution used in step S6 is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a concentration of 10%-30%.

10. The alkylation of methylnaphthalene to produce alkylnaphthalene sulfonate rust inhibitor according to claim 1, characterized in that, In step S7, the neutralized solution is centrifuged and separated, and the supernatant or filtrate is collected to obtain the alkylnaphthalene sulfonate product.

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