Alkylation superposition process of etherified C4

Abstract

The invention discloses an alkylation superposition process of etherified C4, and belongs to the technical field of alkylation processes, the process takes etherified C4 as a raw material, and the etherified C4 is sequentially subjected to the steps of dehydration adsorption, propane separation, alkylation synthesis, flash separation, washing and refining, fractionation separation and waste acid treatment. According to the preparation method, sulfonate doped polypyrrole modified silica gel is taken as an adsorbent, pyrrole is subjected to in-situ polymerization on silica gel, alkyl chain-containing hydroxyl sodium sulfonate is added for doping modification, polar impurities can be efficiently captured, the purity of a C4 raw material is remarkably improved, purified C4 and isooctane are subjected to an alkylation reaction under the catalysis of sulfuric acid, and the purity of the C4 raw material is improved. The method has the advantages that reaction and separation are synergistically enhanced through flash evaporation, washing and rectification, the system stability and the reaction conversion rate are improved, the industrial isooctane superimposed oil is obtained, the raw materials and the catalyst are recycled, the overall energy efficiency is high, the product quality is excellent, and the method is suitable for industrial continuous production.

Description

Technical Field

[0001] This invention belongs to the field of alkylation process technology, specifically a post-etherification C4 alkylation superposition process. Background Technology

[0002] Currently, industrial isooctane is mostly produced using sulfuric acid catalytic alkylation. This process typically uses isobutane and post-etherified C4 from the etherification unit as the main raw materials. During the etherification process, it is difficult to completely remove trace amounts of oxygen-containing compounds from post-etherified C4, which often contains residual polar impurities such as water, alcohols, ethers, carbonyl compounds, and thiols. When these impurities enter the sulfuric acid alkylation reaction system, they will undergo side reactions with concentrated sulfuric acid, reducing catalyst activity, increasing acid consumption, and leading to a decrease in the quality and yield of industrial isooctane.

[0003] Therefore, in order to improve the efficiency of the alkylation process, adsorbents are commonly used for pretreatment in the process. Commonly used adsorbent types include aluminosilicates, molecular sieves, alumina, and activated carbon. These materials can reduce the impurity content in the raw materials through physical adsorption or pore sieving, thereby providing more stable reaction conditions for industrial isooctane production.

[0004] Chinese patent application CN105152840A discloses a refining process for C4 hydrocarbon streams. In the C4 refining process, molecular sieves and silica gel are used as adsorbents to remove impurities in C4, thereby achieving adsorption and purification treatment of alkylation raw materials.

[0005] In the above schemes, molecular sieves and silica gel mainly rely on pore size sieving and weakly polar sites on the surface to exert adsorption. The surface of silica gel only has weakly polar silanol groups and lacks functional sites that can interact directionally with strongly polar oxygen-containing impurities such as alcohols and ethers, resulting in low adsorption selectivity for polar impurities. Therefore, this type of adsorbent cannot effectively reduce the impurity content when treating C4 ethers containing multiple polar impurities, which has a significant impact on the stability and yield of subsequent alkylation processes. Summary of the Invention

[0006] The purpose of this invention is to provide an alkylation process for post-etherified C4, which involves in-situ initiation of pyrrole oxidative polymerization in a porous silica gel structure, using alkyl-chain hydroxysulfonates as dopants and functionalizing components to prepare a modified silica gel adsorbent with high selective adsorption capacity. This adsorbent efficiently removes polar impurities from the post-etherified C4 feedstock, ensuring the efficiency of the alkylation reaction. Simultaneously, by combining light hydrocarbon removal fractionation, flash separation, acid-base washing purification, and two-stage distillation separation processes, high-purity industrial isooctane is obtained, and the feedstock and impurities are recycled, thereby reducing energy and feedstock consumption. This results in a highly efficient and stable alkylation process.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides an alkylation process for C4 etherification, which sequentially includes a raw material C4 refining process, an industrial isooctane synthesis process, an industrial isooctane flash separation process, an industrial isooctane washing and refining process, an industrial isooctane fractionation separation process, and a waste acid treatment process.

[0009] Furthermore, the refining process for the raw material C4 includes the following steps:

[0010] After etherification, C4 and C4 are dehydrated and sent to the raw material refining unit, where they are treated with sulfonate-doped polypyrrole-modified silica gel adsorbent. The treated material is then introduced into a light hydrocarbon removal tower for fractionation to remove propane. The bottom fraction is collected and cooled to obtain the refined C4 fraction.

[0011] Furthermore, the top pressure of the light hydrocarbon removal tower is 0.5-1.5 MPa, the top temperature is 30-50℃, and the bottom temperature is 90-120℃.

[0012] This process achieves deep purification of C4 feedstock through the synergistic effect of dehydration, adsorption purification, and distillation separation. Dehydration effectively removes free water, preventing corrosion of subsequent equipment and deactivation of the adsorbent. After treatment with modified silica gel adsorbent, polar impurities are preferentially removed, making the material composition more stable. Subsequently, the components are separated in a light hydrocarbon removal tower by utilizing the difference in volatility between them, allowing light impurities such as propane to be removed from the top of the tower, ultimately obtaining a high-purity refined C4 fraction. This reduces the occurrence of side reactions in subsequent reactions, improves the reaction yield, thereby enhancing product quality and strengthening the stability and controllability of the entire process.

[0013] Furthermore, the preparation process of sulfonate-doped polypyrrole-modified silica gel adsorbent is as follows:

[0014] Silica gel and a 0.3 mol / L pyrrole solution were placed in a reaction vessel and reacted at 25-35℃ for 9-12 h. Ferric chloride hexahydrate was added, and the reaction was continued at 25-35℃ for 1-3 h. Then, sodium hydroxysulfonate containing alkyl chain was added, and the reaction was continued at the same temperature for 2-4 h. The mixture was filtered, washed, and vacuum dried to constant weight to obtain sulfonate-doped polypyrrole modified silica gel adsorbent.

[0015] Furthermore, the ratio of silica gel, pyrrole solution, ferric chloride hexahydrate, and sodium hydroxysulfonate containing alkyl chains is 300-500g: 1.5-2.5L: 250-450g: 80-160g.

[0016] Furthermore, the preparation process of sodium alkyl-chain hydroxysulfonate is as follows:

[0017] Sodium bisulfite and deionized water were placed in a reaction vessel and stirred at 25-35℃ for 10-20 min. A 20wt% sodium hydroxide solution was added to adjust the pH of the reaction solution to 7-8. 1-Buten-3-ol was added, and a 5wt% dilute sulfuric acid solution was added to adjust the pH of the reaction solution to 7-8. The reaction was carried out at 40-50℃ for 1-2 h. The product was then distilled under reduced pressure at 80-90℃. The product was added to an 80wt% methanol solution to precipitate the product. The product was filtered, the filter cake was collected, and vacuum dried to constant weight to obtain sodium alkyl chain hydroxysulfonate.

[0018] Furthermore, the ratio of sodium bisulfite, sodium hydroxide solution, 1-buten-3-ol, dilute sulfuric acid, and deionized water is 100-200g: 150-250mL: 80-160g: 300-500mL: 600-800mL.

[0019] Furthermore, the industrial isooctane synthesis process includes the following steps:

[0020] The refined C4 fraction and isobutane are fed into a reactor and reacted under the action of sulfuric acid catalyst. The reaction solution is introduced into an acid settling tank for separation. When the concentration of the upper sulfuric acid phase is greater than 90 wt%, the sulfuric acid phase is recovered and recycled. When it is less than 90 wt%, it is treated as waste acid. The lower layer is crude industrial isooctane.

[0021] Furthermore, the temperature inside the reactor is 5-10℃, and the pressure is 0.3-0.6MPa.

[0022] Furthermore, the pressure in the acid settling tank is 0.2-0.4 MPa.

[0023] This process utilizes the strong acid catalytic properties of sulfuric acid on olefins to promote the alkylation reaction of isobutane and etherified C4. After the reaction, the density difference between sulfuric acid and the product is used to achieve gravity stratification. The high-concentration sulfuric acid in the upper layer can be recycled to maintain the acid strength of the system and reduce catalyst consumption, while the lower layer is crude industrial isooctane. This process combines high-efficiency reaction with catalyst recovery.

[0024] Furthermore, the industrial isooctane flash separation process includes the following steps:

[0025] Industrial crude isooctane is subjected to flash evaporation separation under reduced pressure to obtain a gas-liquid two-phase mixture. The gas phase is compressed and refrigerated to form a circulating refrigerant and is reused in the reactor, while the liquid phase is collected as industrial crude isooctane flash evaporation product.

[0026] Furthermore, the flash temperature is 0-20℃ and the pressure is 0.1-0.3MPa.

[0027] Furthermore, the pressure for compression refrigeration is 0.5-0.8 MPa.

[0028] This process utilizes the principle of pressure reduction flash evaporation to selectively vaporize light hydrocarbons in crude industrial isooctane, forming a gas-liquid two-phase system. After flash separation, unreacted isobutane and light components in the gas phase enter the compression refrigeration system and are converted into circulating refrigerant, which is then returned to the reactor to maintain the reaction temperature, thereby achieving energy recovery and process temperature control. The liquid phase remains in a stable liquid state under flash evaporation conditions and is output as crude industrial isooctane flash product. The automatic separation of light and heavy components is achieved through the difference in volatility of the components, and the process is self-circulated.

[0029] Furthermore, the industrial isooctane washing and refining process includes the following steps:

[0030] The crude industrial isooctane flash distillation product is subjected to acid washing, alkali washing and water washing in sequence. After separation, the final liquid phase is collected to obtain the refined industrial isooctane feed stream.

[0031] Furthermore, the pickling solution is concentrated sulfuric acid with a concentration of 98 wt%, the alkaline washing solution is sodium hydroxide with a concentration of 12 wt%, and the water washing solution is deionized water.

[0032] Furthermore, the pH value of the washing system should be controlled at 8-10 during alkaline washing.

[0033] This process removes entrained acids and sulfates from the reaction effluent through acid washing, alkali washing, and water washing in stages. This prevents them from decomposing and causing corrosion in subsequent towers and prevents scale formation in reboilers. Acid washing can absorb most of the acid esters, alkali washing can remove residual acids and the alkali solution can be recycled, and water washing can remove water-soluble salts to obtain adsorbed and purified material. Through staged washing, impurities are effectively removed while taking into account reagent recycling and operational economy, thereby obtaining a higher quality industrial isooctane product.

[0034] Furthermore, the industrial isooctane fractionation and separation process includes the following steps:

[0035] The industrial isooctane refining feed stream is sequentially fed into an isobutane removal separation tower and a n-butane removal separation tower for fractionation. Isobutane and n-butane are recovered from the top of the towers, respectively, and the bottom fraction is continuously collected after cooling to obtain industrial isooctane composite oil.

[0036] Furthermore, the top pressure of the isobutane separation tower is 0.2-0.4 MPa, the top temperature is 35-45℃, and the bottom temperature is 90-110℃.

[0037] Furthermore, the top pressure of the n-butane removal separation column is 0.2-0.4 MPa, the top temperature is 30-50℃, and the bottom temperature is 120-140℃.

[0038] This process achieves efficient separation of isobutane, n-butane, and industrial isooctane through two-stage distillation. Isobutane and n-butane have low boiling points and high relative volatility, making them more likely to migrate to the gas phase and accumulate at the top of the column during multi-stage vapor-liquid contact. Industrial isooctane has a high boiling point and low volatility, mainly remaining at the bottom of the column. By first separating the light isobutane and then separating the relatively moderately volatile n-butane, high-purity industrial isooctane can be gradually obtained. Thermodynamic selective separation is achieved through the difference in volatility between the components, effectively separating light and heavy hydrocarbons, and realizing material collection to obtain high-purity industrial isooctane products.

[0039] Furthermore, the waste acid treatment process includes the following steps:

[0040] Waste acid generated in the acid settling tank during the industrial isooctane synthesis process is sent to the acid discharge tank. After settling and stratification, the lower layer of waste acid is discharged and collected in a centralized manner, thus achieving waste acid treatment.

[0041] Furthermore, the acid removal tank is filled with an inert nitrogen atmosphere at a temperature of 20-30℃.

[0042] This process removes low-concentration acids generated during the reaction in a timely manner at the front end, preventing them from entering subsequent flash evaporation, washing, and distillation units and causing corrosion or affecting product quality. At the same time, the inert atmosphere prevents moisture from entering and causing further decrease in acidity. This waste acid treatment process achieves effective separation, centralized collection, and safe external delivery of the acid phase, ensuring the long-term stable operation of the alkylation unit.

[0043] The beneficial effects of this invention are:

[0044] 1. In the alkylation and polymerization process of post-ether C4, the adsorbent is a sulfonate-doped polypyrrole-modified silica gel adsorbent. By initiating in-situ oxidative polymerization of pyrrole in the porous structure of silica gel, and introducing sodium hydroxysulfonate containing alkyl chains as a dopant during the polymerization process, a polypyrrole functional layer is uniformly generated on the outer surface and inner wall of the pores of silica gel. A functional interface rich in strong polar functional groups such as sulfonic acid groups and hydroxyl groups is constructed on the silica gel. This functional interface can generate hydrogen bonding and electrostatic adsorption with polar oxygen-containing impurities such as alcohols, ethers, and carbonyl compounds. At the same time, the alkyl chain can provide moderate hydrophobicity, improve the interaction between the adsorbent and the non-polar impurities, enhance the selective capture ability of the adsorbent for polar impurities, and thus significantly improve the removal depth of polar impurities in post-ether C4.

[0045] 2. In the alkylation and polymerization process of post-ether C4, this invention first prepares hydroxyl-containing sulfonates during the synthesis of sulfonate-doped polypyrrole-modified silica adsorbents. These sulfonates are then used as dopants and functionalizing components during the in-situ oxidative polymerization of pyrrole. The hydroxyl groups in the sodium hydroxysulfonate molecule can form hydrogen bonds with the silanol groups on the silica gel surface. Simultaneously, the flexibility of the alkyl chain enhances the adsorption stability of the sulfonate on the silica gel surface, making it easier for the sulfonate to adsorb and anchor onto the silica gel before and after polymerization. Furthermore, during the doping process, it can further bind with the polypyrrole segments through hydrogen bonds and other interactions, enhancing the stability of the functional interface and silica gel bonding during the in-situ growth of pyrrole. Additionally, the conjugated nitrogen-containing skeleton of pyrrole effectively delocalizes positive charges after doping, providing stable binding sites for the sodium hydroxysulfonate, thus facilitating the fixation and uniform distribution of anionic sulfonates on the silica gel. This forms a stable and continuous functional interface, enabling the adsorbent to maintain continuous and stable capture of polar impurities in post-ether C4 during operation, exhibiting stable and long-lasting high efficiency in deep removal of polar impurities.

[0046] 3. In the alkylation superposition process of C4 after etherification, this invention uses sulfonate-doped polypyrrole-modified silica gel as an adsorbent in the raw material C4 purification process. This adsorbent provides a well-developed pore structure and mass transfer channels, enabling the C4 raw material after etherification to quickly enter the interior of the adsorbent. The sulfonate-doped polypyrrole-modified layer forms a continuous and dense polar interface on the silica gel surface, enhancing the ability to capture and fix polar impurities, significantly reducing the impurity content in the raw material before entering the alkylation unit, resulting in higher raw material purity and a more stable reaction system in the subsequent alkylation superposition process. This significantly improves the operational stability of the alkylation superposition process and achieves continuous and stable production of higher quality products. Attached Figure Description

[0047] Figure 1 This is a flow chart of the alkylation process of C4 after etherification. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Example 1: This example provides a sulfonate-doped polypyrrole-modified silica adsorbent for the alkylation and superposition process of post-etherified C4, prepared through the following steps:

[0050] S1: Place 100g sodium bisulfite and 600mL deionized water in a reaction vessel and stir at 200r / min for 10min at 25℃. Add 150mL of 20wt% sodium hydroxide solution to adjust the pH of the reaction solution to 7. Add 80g 1-buten-3-ol and 300mL of 5wt% dilute sulfuric acid to adjust the pH of the reaction solution to 7. Stir at 200r / min for 1h at 40℃. After the reaction is completed, cool to room temperature and distill under reduced pressure at 80℃. Add the product to 80wt% methanol solution to precipitate the product. Filter, collect the filter cake, and dry under vacuum at 70℃ to constant weight to obtain sodium alkyl chain hydroxysulfonate.

[0051] S2: 300g of silica gel and 1.5L of 0.3mol / L pyrrole solution were placed in a reaction vessel and stirred at 200r / min at 25℃ for 9h. 250g of ferric chloride hexahydrate was added and the reaction was continued at 25℃ with the same stirring rate for 1h. Then 80g of sodium alkyl-chain hydroxysulfonate was added and the reaction was continued at the same temperature and stirring rate for 2h. After the reaction was completed, the mixture was filtered, and the filter cake was washed twice with deionized water and ethanol. It was then vacuum dried at 60℃ to constant weight to obtain sulfonate-doped polypyrrole modified silica gel adsorbent.

[0052] Example 2: This example provides a sulfonate-doped polypyrrole-modified silica adsorbent for the alkylation and superposition process of post-etherified C4, prepared through the following steps:

[0053] S1: Place 150g sodium bisulfite and 700mL deionized water in a reaction vessel and stir at 250r / min for 15min at 30℃. Add 200mL of 20wt% sodium hydroxide solution to adjust the pH of the reaction solution to 7.5. Add 120g 1-buten-3-ol and 400mL of 5wt% dilute sulfuric acid to adjust the pH of the reaction solution to 7.5. Stir at 250r / min for 1.5h at 45℃. After the reaction is completed, cool to room temperature and distill under reduced pressure at 85℃. Add the product to an 80wt% methanol solution to precipitate the product. Filter, collect the filter cake, and dry under vacuum at 80℃ to constant weight to obtain sodium alkyl chain hydroxysulfonate.

[0054] S2: 400g of silica gel and 2L of 0.3mol / L pyrrole solution were placed in a reaction vessel and stirred at 250r / min at 30℃ for 11h. 350g of ferric chloride hexahydrate was added and the reaction was continued at 30℃ with the same stirring rate for 2h. Then 120g of sodium alkyl chain hydroxysulfonate was added and the reaction was continued at the same temperature and stirring rate for 3h. After the reaction was completed, the mixture was filtered, and the filter cake was washed three times with deionized water and ethanol. It was then vacuum dried at 70℃ to constant weight to obtain sulfonate-doped polypyrrole modified silica gel adsorbent.

[0055] Example 3: This example provides a sulfonate-doped polypyrrole-modified silica adsorbent for the alkylation and superposition process of post-etherified C4, prepared through the following steps:

[0056] S1: Place 200g sodium bisulfite and 800mL deionized water in a reaction vessel and stir at 300r / min for 20min at 35℃. Add 250mL of 20wt% sodium hydroxide solution to adjust the pH of the reaction solution to 8. Add 160g 1-buten-3-ol and 500mL of 5wt% dilute sulfuric acid to adjust the pH of the reaction solution to 8. Stir at 300r / min for 2h at 50℃. After the reaction is completed, cool to room temperature and distill under reduced pressure at 90℃. Add the product to 80wt% methanol solution to precipitate. Filter, collect the filter cake, and dry under vacuum at 90℃ to constant weight to obtain sodium alkyl chain hydroxysulfonate.

[0057] S2: 500g of silica gel and 2.5L of 0.3mol / L pyrrole solution were placed in a reaction vessel and stirred at 300r / min at 35℃ for 12h. 450g of ferric chloride hexahydrate was added, and the reaction was continued at 35℃ with the same stirring rate for 3h. Then, 160g of sodium alkyl-chain hydroxysulfonate was added, and the reaction was continued at the same temperature and stirring rate for 4h. After the reaction was completed, the mixture was filtered, and the filter cake was washed four times with deionized water and ethanol. It was then vacuum dried at 80℃ to constant weight to obtain sulfonate-doped polypyrrole-modified silica gel adsorbent.

[0058] The sulfonate-doped polypyrrole-modified silica adsorbents prepared in Examples 1-3 above were first prepared by reacting 1-buten-3-ol with sodium bisulfite in a solution system with a nucleophilic addition reaction to generate sodium alkyl-chain hydroxysulfonate, introducing polar functional groups into the material. Subsequently, pyrrole monomers were introduced in situ onto the silica surface, and oxidative polymerization of pyrrole was triggered by ferric chloride, so that polypyrrole was uniformly loaded onto the surface and pores of the silica framework. On this basis, sodium alkyl-chain hydroxysulfonate was introduced into the polypyrrole layer, and the effective doping of sulfonate in the polypyrrole network was achieved through charge interaction and structural recombination, thereby obtaining the sulfonate-doped polypyrrole-modified silica adsorbent.

[0059] Example 4: This example provides a post-etherification C4 alkylation process, such as... Figure 1 As shown, it includes the following steps:

[0060] Step 1: The C4 fraction after etherification is placed in a condenser to remove free water, and then enters the raw material refining unit located before the light hydrocarbon removal tower. The refining unit is filled with sulfonate-doped polypyrrole-modified silica gel adsorbent. The material treated with the adsorbent enters the light hydrocarbon removal tower. At a top pressure of 0.5 MPa, a top temperature of 30°C, and a bottom temperature of 90°C, the propane light component in the raw material is removed at the top of the tower. The light hydrocarbon removed C4 fraction obtained at the bottom of the tower is collected and cooled to obtain the refined C4 fraction.

[0061] Step 2: Add the refined C4 fraction and isobutane to the industrial isooctane reactor. Pass sulfuric acid catalyst into the reactor and mix thoroughly at 100 r / min using an impeller-type mechanical stirrer under 5°C and 0.3 MPa pressure. After the reaction, the reaction solution enters an acid settling tank and undergoes gravity separation under an operating pressure of 0.2 MPa. The upper layer is the sulfuric acid phase. When the sulfuric acid concentration is greater than 90 wt%, it can be continuously fed into the reactor for recycling. When the concentration is less than 90 wt%, it is treated as waste acid. The lower layer is the product, yielding crude industrial isooctane.

[0062] Step 3: The crude industrial isooctane is subjected to depressurized flash evaporation at a flash temperature of 0°C and a pressure of 0.1 MPa. Some components are vaporized to form a gas-liquid mixture, which enters the flash tank for gas-liquid separation. The gas phase mainly consists of unreacted isobutane and light hydrocarbons, which enter the compression refrigeration system through the outlet to form a circulating refrigerant at an operating pressure of 0.5 MPa. The generated refrigerant is pumped to the reactor inlet by the circulating refrigerant pump and mixed with the raw materials to maintain the required reaction temperature. The separated liquid phase remains liquid under flash evaporation conditions, thus obtaining the crude industrial isooctane flash product.

[0063] Step 4: Place the industrial isooctane flash distillation crude product and 98wt% concentrated sulfuric acid in an acid washing mixer and perform acid washing at 25°C. After standing and separating, place the lower layer product and 12wt% sodium hydroxide in an alkaline washing mixer and perform alkaline washing at 25°C and pH 8. After standing and separating, the upper alkaline solution is circulated in the alkaline washing mixer, and the lower layer product and deionized water are placed in a water washing mixer and washed at 25°C. After standing and separating, collect the lower layer product to obtain refined industrial isooctane.

[0064] Step 5: The industrial isooctane refined feed stream is first preheated by heat exchange and then enters the isobutane removal separation tower. Fractionation is carried out under the conditions of 0.2 MPa top pressure, 35°C top temperature, and 90°C bottom temperature, so that isobutane is enriched from the top of the tower and continuously collected. After cooling at 25°C, it can be added as feedstock to the industrial isooctane reactor in Step 2 for recycling. The bottom liquid phase is the heavy component containing the product after isobutane removal, which is sent to the next separation stage. The heavy component containing the product is sent to the n-butane removal separation tower for further fractionation under the conditions of 0.2 MPa top pressure, 30°C top temperature, and 120°C bottom temperature, so that n-butane is enriched at the top of the tower and condensed and recovered. After cooling at 25°C, it enters the n-butane tank area. The bottom fraction is continuously collected after cooling to obtain industrial isooctane composite oil.

[0065] Step Six: Send the waste acid generated in Step Two into the acid discharge tank and let it stand at 30°C under nitrogen atmosphere protection. After standing, discharge the lower layer of waste acid to the waste acid storage tank for centralized collection. Once the set liquid level is reached, it will be discharged through the external transmission line, thus completing the waste acid treatment process.

[0066] Example 5: This example provides a post-etherification C4 alkylation process, such as... Figure 1 As shown, it includes the following steps:

[0067] Step 1: The C4 fraction after etherification is placed in a condenser to remove free water, and then enters the raw material refining unit located before the light hydrocarbon removal tower. The refining unit is filled with sulfonate-doped polypyrrole-modified silica gel adsorbent. The material treated with the adsorbent enters the light hydrocarbon removal tower. At a top pressure of 1 MPa, a top temperature of 40°C, and a bottom temperature of 110°C, the propane light component in the raw material is removed at the top of the tower. The light hydrocarbon removed C4 fraction obtained at the bottom of the tower is collected and cooled to obtain the refined C4 fraction.

[0068] Step 2: Add the refined C4 fraction and isobutane to the industrial isooctane reactor. Pass sulfuric acid catalyst into the reactor and mix thoroughly at 100 r / min using an impeller-type mechanical stirrer under 5°C and 0.3 MPa pressure. After the reaction, the reaction solution enters an acid settling tank and undergoes gravity separation under an operating pressure of 0.2 MPa. The upper layer is the sulfuric acid phase. When the sulfuric acid concentration is greater than 90 wt%, it can be continuously fed into the reactor for recycling. When the concentration is less than 90 wt%, it is treated as waste acid. The lower layer is the product, yielding crude industrial isooctane.

[0069] Step 3: The crude industrial isooctane is subjected to depressurized flash evaporation at a flash temperature of 10°C and a pressure of 0.2 MPa. Some components are vaporized to form a gas-liquid mixture, which enters the flash tank for gas-liquid separation. The gas phase mainly consists of unreacted isobutane and light hydrocarbons, which enter the compression refrigeration system through the outlet to form a circulating refrigerant at an operating pressure of 0.7 MPa. The generated refrigerant is pumped to the reactor inlet by the circulating refrigerant pump and mixed with the raw materials to maintain the required reaction temperature. The separated liquid phase remains liquid under flash evaporation conditions, thus obtaining the crude industrial isooctane flash product.

[0070] Step 4: Place the industrial isooctane flash distillation crude product and 98wt% concentrated sulfuric acid in an acid washing mixer and acid wash at 35°C. After standing and separating, place the lower layer product and 12wt% sodium hydroxide in an alkaline washing mixer and alkaline wash at 30°C and pH 9. After standing and separating, the upper alkaline solution is circulated in the alkaline washing mixer, and the lower layer product and deionized water are placed in a water washing mixer and water washed at 30°C. After standing and separating, collect the lower layer product to obtain refined industrial isooctane.

[0071] Step 5: The industrial isooctane refined feed stream is first preheated by heat exchange and then enters the isobutane removal separation tower. Fractionation is carried out under the conditions of 0.3 MPa top pressure, 30°C top temperature, and 100°C bottom temperature, so that isobutane is enriched from the top of the tower and continuously collected. After cooling at 30°C, it can be added as feedstock to the industrial isooctane reactor in Step 2 for recycling. The bottom liquid phase is the heavy component containing the product after isobutane removal, which is sent to the next separation stage. The heavy component containing the product is sent to the n-butane removal separation tower, where it is further fractionated under the conditions of 0.3 MPa top pressure, 40°C top temperature, and 130°C bottom temperature, so that n-butane is enriched at the top of the tower and condensed and recovered. After cooling at 30°C, it enters the n-butane tank area. The bottom fraction is continuously collected after cooling to obtain industrial isooctane composite oil.

[0072] Step Six: Send the waste acid generated in Step Two into the acid discharge tank and let it stand at 30°C under nitrogen atmosphere protection. After standing, discharge the lower layer of waste acid to the waste acid storage tank for centralized collection. Once the set liquid level is reached, it will be discharged through the external transmission line, thus completing the waste acid treatment process.

[0073] Example 6: This example provides a post-etherification C4 alkylation process, such as... Figure 1 As shown, it includes the following steps:

[0074] Step 1: The C4 fraction after etherification is placed in a condenser to remove free water, and then enters the raw material refining unit located before the light hydrocarbon removal tower. The refining unit is filled with sulfonate-doped polypyrrole-modified silica gel adsorbent. The material treated with the adsorbent enters the light hydrocarbon removal tower. At a top pressure of 1.5 MPa, a top temperature of 50°C, and a bottom temperature of 120°C, the propane light component in the raw material is removed at the top of the tower. The light hydrocarbon removed C4 fraction obtained at the bottom of the tower is collected and cooled to obtain the refined C4 fraction.

[0075] Step 2: Add the refined C4 fraction and isobutane to the industrial isooctane reactor. Pass sulfuric acid catalyst into the reactor and mix thoroughly at 100 r / min using an impeller-type mechanical stirrer under 5°C and 0.3 MPa pressure. After the reaction, the reaction solution enters an acid settling tank and undergoes gravity separation under an operating pressure of 0.2 MPa. The upper layer is the sulfuric acid phase. When the sulfuric acid concentration is greater than 90 wt%, it can be continuously fed into the reactor for recycling. When the concentration is less than 90 wt%, it is treated as waste acid. The lower layer is the product, yielding crude industrial isooctane.

[0076] Step 3: The crude industrial isooctane is subjected to depressurized flash evaporation at a flash temperature of 20°C and a pressure of 0.3 MPa. Some components are vaporized to form a gas-liquid mixture, which enters the flash tank for gas-liquid separation. The gas phase mainly consists of unreacted isobutane and light hydrocarbons, which enter the compression refrigeration system through the outlet to form a circulating refrigerant at an operating pressure of 0.8 MPa. The generated refrigerant is pumped to the reactor inlet by the circulating refrigerant pump and mixed with the raw materials to maintain the required reaction temperature. The separated liquid phase remains liquid under flash evaporation conditions, thus obtaining the crude industrial isooctane flash product.

[0077] Step 4: Place the industrial isooctane flash distillation crude product and 98wt% concentrated sulfuric acid in an acid washing mixer and acid wash at 40°C. After standing and separating, place the lower layer product and 12wt% sodium hydroxide in an alkaline washing mixer and alkaline wash at 35°C and pH 10. After standing and separating, the upper alkaline solution is recycled in the alkaline washing mixer, and the lower layer product and deionized water are placed in a water washing mixer and water washed at 35°C. After standing and separating, collect the lower layer product to obtain refined industrial isooctane.

[0078] Step 5: The industrial isooctane refined feed stream is first preheated by heat exchange and then enters the isobutane removal separation tower. Fractionation is carried out under the conditions of 0.4 MPa top pressure, 45°C top temperature, and 110°C bottom temperature, so that isobutane is enriched from the top of the tower and continuously collected. After cooling at 35°C, it can be added as raw material to the industrial isooctane reactor in Step 2 for recycling. The bottom liquid phase is the heavy component containing the product after isobutane removal, which is sent to the next separation stage. The heavy component containing the product is sent to the n-butane removal separation tower, where it is further fractionated under the conditions of 0.4 MPa top pressure, 50°C top temperature, and 140°C bottom temperature, so that n-butane is enriched at the top of the tower and condensed and recovered. After cooling at 35°C, it enters the n-butane tank area. The bottom fraction is continuously collected after cooling to obtain industrial isooctane composite oil.

[0079] Step Six: Send the waste acid generated in Step Two into the acid discharge tank and let it stand at 30°C under nitrogen atmosphere protection. After standing, discharge the lower layer of waste acid to the waste acid storage tank for centralized collection. Once the set liquid level is reached, it will be discharged through the external transmission line, thus completing the waste acid treatment process.

[0080] Comparative Example 1: Based on Example 2, commercially available silica gel was used as the adsorbent instead of the sulfonate-doped polypyrrole-modified silica gel adsorbent prepared in S2, while the other steps remained unchanged.

[0081] Comparative Example 2: Based on Example 2, the sodium alkyl chain hydroxysulfonate salt prepared from S1 in S2 was removed, while the other steps remained unchanged.

[0082] Comparative Example 3: Based on Example 2, commercially available sulfonates were used instead of the sodium alkyl-chain hydroxysulfonate prepared in S1, while the remaining steps remained unchanged.

[0083] The silica gel purchased in the above examples and comparative examples was produced by Shanghai Aladdin Biochemical Technology Co., Ltd., with an average particle size of 40-60 mesh; the sulfonate was produced by Shanghai Maclean Biochemical Technology Co., Ltd., named sodium hydroxyethyl sulfonate, CAS number 1562-00-1; and the C4 ether was produced by Sinopec Petrochemical Sales Co., Ltd., with an average olefin content of 40%.

[0084] The adsorbents prepared in Examples 1-3 and Comparative Examples 1-3 were used in experiments simulating the alkylation of C4 after etherification, and their adsorption, purification and alkylation reaction performance were evaluated. The test results are shown in Table 1.

[0085] Experimental preparation: A combination of a stainless steel fixed-bed adsorption device and a high-pressure reactor with stirring, commonly used in the laboratory, was used to simulate the purification conditions of C4 after etherification and the subsequent alkylation reaction conditions. 100g of the adsorbent prepared above was taken as a sample.

[0086] Adsorption and purification performance: Referring to the operation method of the adsorption section in the raw material C4 refining process in Example 5, 100g of adsorbent was packed into a fixed bed adsorption column, and the etherified C4 raw material was introduced from bottom to top. The purified C4 at the outlet was analyzed by gas chromatography to obtain the mass fraction (%) of C4 hydrocarbon components in the purified C4 fraction. The higher the mass fraction of C4 hydrocarbon components in the purified C4, the higher the purity of C4, that is, the better the adsorption and purification performance, and the more effectively the polar impurities in the etherified C4 can be removed.

[0087] Alkylation reaction performance: Referring to the operation method of the industrial isooctane synthesis process in Example 5, the refined C4 fraction obtained in the above experiment was used as the alkylation reaction feedstock and added together with isobutane into a stirred autoclave reactor. Sulfuric acid was used as a catalyst to carry out the isooctane synthesis experiment. After the reaction was completed, the organic phase was separated after standing and layering. The mass fraction of olefin components in the feedstock before the reaction and the mass fraction of industrial isooctane in the product after the reaction were determined by gas chromatography. The C4 hydrocarbon conversion rate was calculated based on the change in the mass fraction of olefins before and after the reaction. The higher the C4 hydrocarbon conversion rate and the mass fraction of industrial isooctane, the higher the alkylation efficiency.

[0088] Table 1. Adsorption purification and alkylation reaction performance test table

[0089] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Refined C4 hydrocarbon content / % 96.8 97.9 97.4 91.2 93.1 94.3 C4 hydrocarbon conversion rate / % 90.6 93.8 92.4 78.5 82.4 86.2 Industrial isooctane mass fraction / % 92.7 95.6 94.3 80.1 84.5 88.0

[0090] As shown in Table 1, the sulfonate-doped polypyrrole-modified silica adsorbents prepared in Examples 1-3 exhibit better adsorption and purification performance in the refining C4 raw material process and in subsequent alkylation reaction performance than Comparative Examples 1-3. This indicates that the functionalization of the silica surface was achieved by doping polypyrrole with sodium hydroxysulfonate containing alkyl chains. The resulting sulfonate-doped polypyrrole-modified silica adsorbent has higher adsorption selectivity for polar impurities in the etherified C4, thereby significantly improving the purity of the refined C4. In the subsequent alkylation reaction, it significantly improves the C4 conversion rate and the industrial isooctane yield, making the alkylation process more stable and efficient.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A post-etherification C4 alkylation process, characterized in that, Includes the following steps: Step 1: The etherified C4 is dehydrated, purified by adsorption with sulfonate-doped polypyrrole-modified silica gel, and then sent to a light hydrocarbon removal tower for fractionation to remove propane, thus obtaining purified C4. Step 2: Refined C4 and isobutane are fed into a reactor and reacted under the catalysis of concentrated sulfuric acid. After separation in an acid settling tank, the upper layer is the acid phase. When the acid phase concentration is greater than 90 wt%, it can be recycled. When it is less than 90 wt%, it is treated as waste acid. The lower layer is crude industrial isooctane. Step 3: The industrial crude isooctane is flash-separated, the gas phase is compressed and refrigerated and recycled back to the reactor, and the liquid phase forms the flash crude product; Step 4: The flash-distilled crude product is subjected to acid washing, alkali washing and water washing in sequence to obtain refined industrial isooctane; Step 5: The refined industrial isooctane is first fractionated by an isobutane removal column, and the top isobutane is collected for recycling. The bottom fraction is then fractionated by a n-butane removal column, and the n-butane is collected at the top. The bottom fraction is then extracted to obtain industrial isooctane composite oil.

2. The alkylation and dimerization process for post-etherification C4 according to claim 1, characterized in that, The sulfonate-doped polypyrrole-modified silica gel adsorbent in step one is prepared through the following steps: Silica gel and a 0.3 mol / L pyrrole solution were placed in a reaction vessel and reacted at 25-35℃ for 9-12 h. Ferric chloride hexahydrate was added and the reaction was continued for 1-3 h. Then, sodium hydroxysulfonate containing alkyl chain was added and the reaction was continued for 2-4 h. The mixture was filtered, washed, and vacuum dried to constant weight to obtain sulfonate-doped polypyrrole modified silica gel adsorbent.

3. The alkylation and dimerization process for post-etherification C4 according to claim 2, characterized in that, The ratio of silica gel, pyrrole solution, ferric chloride hexahydrate and sodium hydroxysulfonate containing alkyl chain is 300-500g: 1.5-2.5L: 250-450g: 80-160g.

4. The alkylation and dimerization process for post-etherification C4 according to claim 3, characterized in that, The sodium alkyl-containing hydroxysulfonate salt is prepared by the following steps: Sodium bisulfite and deionized water were placed in a reaction vessel and stirred at 25-35℃ for 10-20 min. A 20wt% sodium hydroxide solution was added to adjust the pH of the reaction solution to 7-8. 1-Buten-3-ol was added, and a 5wt% dilute sulfuric acid solution was added to adjust the pH of the reaction solution to 7-8. The reaction was carried out at 40-50℃ for 1-2 h. The product was then distilled under reduced pressure at 80-90℃. The product was added to an 80wt% methanol solution to precipitate the product. The product was filtered, the filter cake was collected, and vacuum dried to constant weight to obtain sodium alkyl chain hydroxysulfonate. The ratio of sodium bisulfite, sodium hydroxide solution, 1-buten-3-ol, dilute sulfuric acid, and deionized water is 100-200g: 150-250mL: 80-160g: 300-500mL: 600-800mL.

5. The alkylation and dimerization process for post-etherification C4 according to claim 1, characterized in that, The pressure at the top of the light hydrocarbon removal tower described in step one is 0.5-1.5 MPa, the temperature at the top of the tower is 30-50℃, and the temperature at the bottom of the tower is 90-120℃.

6. The alkylation and dimerization process for post-etherification C4 according to claim 1, characterized in that, The reaction temperature of the reactor in step two is 5-10℃, and the pressure is 0.3-0.6MPa.

7. The alkylation process for post-etherified C4 alkylation according to claim 1, characterized in that... The flash separation in step three is carried out at a temperature of 0-20℃ and a pressure of 0.1-0.3MPa.

8. The alkylation and dimerization process for post-etherification C4 according to claim 1, characterized in that, The solvent for acid washing in step four is concentrated sulfuric acid with a concentration of 98 wt%, the solvent for alkaline washing is sodium hydroxide with a concentration of 12 wt%, and the solvent for water washing is deionized water.

9. The alkylation and dimerization process for post-etherification C4 according to claim 1, characterized in that, The isobutane removal separation tower described in step five has a top pressure of 0.2-0.4 MPa, a top temperature of 35-45℃, and a bottom temperature of 90-110℃. The pressure at the top of the n-butane removal separation tower is 0.2-0.4 MPa, the temperature at the top is 30-50℃, and the temperature at the bottom is 120-140℃.

10. The alkylation and dimerization process for post-etherified C4 according to claim 1, characterized in that, Step two, the waste acid treatment, includes the following steps: Waste acid is placed in an acid discharge tank under nitrogen atmosphere protection and left to stand at 20-30℃. After standing, the lower layer of waste acid is discharged and sent to a waste acid storage tank for centralized collection. Once the set liquid level is reached, it is discharged through an external transmission line, thus completing the waste acid treatment process.

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