Process for the catalytic synthesis of methyl tert-butyl ether

Abstract

This invention discloses a catalytic synthesis process for methyl tert-butyl ether, belonging to the field of etherification catalytic synthesis technology. The main raw materials are methanol and pre-ether C4. By introducing mesoporous silica in situ into a strongly acidic cation exchange resin and loading sulfonic acid imidazole trifluoromethanesulfonate ionic liquid into the ion exchange resin, a composite catalyst with a multi-level pore structure is formed, thereby significantly improving the utilization rate of acidic sites inside the catalyst. The resulting modified catalyst can be used in the etherification reaction of methyl tert-butyl ether and subsequent catalytic distillation process, so that the reaction equilibrium continuously shifts towards the product, thereby improving the overall conversion rate of the etherification reaction. This process also improves the raw material conversion rate and product purity through the synergistic effect of reaction and separation, and realizes the recycling of raw materials by combining a methanol recovery system. This process has high reaction efficiency, good catalyst stability, and is suitable for large-scale industrial continuous production.

Description

Technical Field

[0001] This invention belongs to the field of etherification catalytic synthesis technology, specifically a catalytic synthesis process for methyl tert-butyl ether. Background Technology

[0002] Methyl tert-butyl ether (MTBE) is an important high-octane component of gasoline. Its industrial production mainly involves the etherification reaction of pre-ether C4 with methanol under liquid-phase conditions. Isobutylene undergoes addition reaction with methanol to generate MTBE. Since this reaction is a typical liquid-phase acid-catalyzed etherification reaction, strong acid cation exchange resins are commonly used in industry as solid acid catalysts to improve isobutylene conversion and product selectivity. However, traditional resins suffer from problems such as insufficient utilization of acidic sites and a simple pore structure, which prevents some acidic sites from effectively participating in the reaction, thus limiting the overall catalytic efficiency, especially under enhanced process conditions such as catalytic distillation columns.

[0003] Currently, various modification strategies have been proposed to improve the catalytic efficiency of resin-based solid acid catalysts. Among them, organic molecules are used to regulate the environment of the sulfonic acid groups of the resin to enhance the stability and accessibility of its acidic sites, thereby enhancing the catalytic activity in the etherification reaction. In addition, resins are often combined with appropriate inorganic solid materials to form adsorption and dispersion regions on the outer surface of resin particles, thereby improving the distribution of raw materials on the outer surface of the catalyst, promoting the contact between reactants and acidic sites, and further improving the overall catalytic performance.

[0004] In the existing technical solutions, Chinese patent application with publication number CN116060128A discloses an etherification reaction catalyst and its preparation method, as well as a process for preparing ethylene glycol tert-butyl ether. The process involves using a large-pore, strongly acidic ion exchange resin and an organic ester to stabilize the acidic sites of the resin through heat treatment, impregnation, and calcination, thereby obtaining a modified acidic ion exchange resin. The obtained modified acidic ion exchange resin is then combined with amorphous silica-alumina, and the Lewis acid centers of the amorphous silica-alumina composite form an acidic synergy with the acidic sites of the resin, promoting the effective combination of the raw materials and the acidic sites, thus forming a highly efficient catalyst for the etherification reaction.

[0005] In the above technical solutions, heat treatment of the strong acid ion exchange resin with organic esters is difficult to change the internal pore structure of the resin, resulting in the internal acid sites being difficult to fully expose or participate in the reaction. At the same time, the amorphous silica-alumina composite with the resin has a particle size much larger than the nanoscale pores of the resin, and cannot enter the interior of the resin. It can only adhere to the outer surface of the particles, so the reaction still mainly takes place on the outer surface layer. The utilization rate of a large number of strong acid cations inside the resin is low, and the overall catalytic efficiency is limited. It is difficult to meet the requirements of the etherification process for a high-activity and high-efficiency catalytic system, thus further restricting the improvement of the conversion rate and yield of methyl tert-butyl ether synthesis. Summary of the Invention

[0006] The purpose of this invention is to provide a catalytic synthesis process for methyl tert-butyl ether. By preparing a strongly acidic cation exchange resin modified with in-situ grown mesoporous silica and sulfonated imidazole trifluoromethanesulfonate ionic liquid as a catalyst, the utilization rate of methanol and pre-ether C4 feedstock is improved, ensuring efficient conversion of reactants. At the same time, through separation, purification and methanol recovery processes, high-purity preparation of methyl tert-butyl ether is achieved, further reducing raw material consumption and energy consumption, and extending the service life of the catalyst, making it suitable for large-scale industrial production.

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

[0008] This invention provides a catalytic synthesis process for methyl tert-butyl ether, including an etherification process of pre-ether C4 and methanol, a purification process for separating methyl tert-butyl ether, and a methanol recovery process.

[0009] Furthermore, the etherification process of pre-etherified C4 and methanol includes the following steps:

[0010] Pre-etherified C4, methanol, and modified strong acid cation exchange resin are placed in a static mixer at the inlet of the etherification reaction system and mixed at 50-70℃ for 20-40 min. The mixed material is then added to the etherification reactor from the top of the reactor and reacted for 2-4 h at 70-90℃ and 0.8-1.5 MPa pressure. The reactants are collected to obtain crude methyl tert-butyl ether.

[0011] This process utilizes a modified strong acid cation exchange resin to efficiently catalyze the etherification reaction of methanol and isobutylene. The modified structure significantly improves the accessibility and activity stability of the internal acidic sites, making it easier for isobutylene to be enriched and participate in the reaction within the catalyst. This results in an overall improvement in conversion rate and selectivity, a uniform etherification process, and the stable production of crude methyl tert-butyl ether. This demonstrates the comprehensive advantages of simultaneously achieving enhanced catalyst activity, improved material utilization efficiency, and stable process operation.

[0012] Furthermore, the preparation process of the modified strong acid cation exchange resin is as follows:

[0013] Sulfonic acid-supported mesoporous silica ion exchange resin, sulfonic acid-based imidazole trifluoromethanesulfonate ionic liquid, and anhydrous ethanol were placed in a reaction vessel and impregnated at 150-200 r / min for 12-14 h at 40-60 °C. After impregnation, the mixture was filtered, and the filter cake was vacuum dried at 60-70 °C for 10-12 h to obtain the modified strong acid cation exchange resin.

[0014] Furthermore, the ratio of sulfonic acid-supported mesoporous silica ion exchange resin, sulfonic acid-based imidazole trifluoromethanesulfonate ionic liquid, and anhydrous ethanol is 300-500g: 50-100g: 2-3L.

[0015] Furthermore, the preparation process of the sulfonic acid-supported mesoporous silica ion exchange resin is as follows:

[0016] A sulfonate-type macroporous ion exchange resin, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ethanol, and deionized water were placed in a reactor and reacted at 25-35°C for 1-2 hours. A 0.2 mol / L ammonia solution was added, and the reaction was carried out at 50-60°C for 2-4 hours. The mixture was then cooled to 25-30°C, filtered, and the filter cake was added to a 1 mol / L hydrochloric acid solution. The reaction was carried out at 50-60°C for 10-12 hours. The mixture was then centrifuged, and the solid phase was collected to obtain a sulfonate-type supported mesoporous silica ion exchange resin.

[0017] Furthermore, the ratio of sulfonate-type macroporous ion exchange resin, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia solution, hydrochloric acid solution, ethanol, and deionized water is 400-600g: 80-100g: 100-200g: 500-700mL: 700-900mL: 1-1.5L: 600-800mL.

[0018] Furthermore, the preparation process of the sulfonyl imidazole trifluoromethanesulfonate ionic liquid is as follows:

[0019] Sulfonate imidazole inner salt and trifluoromethanesulfonic acid were placed in a reaction vessel and reacted at 80-90℃ for 68-72 h. After extraction, the mixture was dried under vacuum to constant weight to obtain sulfonate imidazole trifluoromethanesulfonate ionic liquid.

[0020] Furthermore, the mass ratio of sulfonyl imidazole inner salt to trifluoromethanesulfonic acid is 60-80:60-80.

[0021] Furthermore, the preparation process of the sulfonate imidazole inner salt is as follows:

[0022] N-Butylimidazole and 1,4-butanesulfonate lactone were placed in a reaction vessel and reacted at 80-90℃ for 18-24 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and vacuum dried to constant weight to obtain the sulfonate imidazole lactone.

[0023] Furthermore, the mass ratio of N-butylimidazole to 1,4-butanesulfonate lactone is 40-60:40-60.

[0024] Furthermore, the purification process for separating methyl tert-butyl ether includes the following steps:

[0025] Crude methyl tert-butyl ether is added into the catalytic distillation column through the bottom feed inlet. Modified strong acid cation exchange resin is added to the middle layer of the column. Under a temperature gradient of 70-80℃ at the bottom and 30-45℃ at the top, the pressure at the top of the column is adjusted to 0.2-0.5 MPa, and catalytic fractionation is carried out for 2-4 hours. The top of the column contains methanol and C4 fraction after etherification reaction. A high-purity methyl tert-butyl ether vapor fraction is formed in the middle of the column, and the bottom of the column contains heavy components. The high-purity methyl tert-butyl ether vapor fraction is continuously collected and cooled to 25-35℃ in a condenser to convert it into a liquid phase. The liquid is filtered to remove impurities and the filtrate is collected to obtain methyl tert-butyl ether.

[0026] This process allows the reversible etherification reaction of methanol and isobutylene to proceed simultaneously with the purification of methyl tert-butyl ether in a catalytic distillation column. It achieves efficient separation by utilizing the upward temperature gradient within the column. The generated methyl tert-butyl ether is rapidly vaporized in the middle and removed from the reaction zone, thus driving the reversible etherification reaction towards the product. Through segmented removal of light and heavy impurities at the top and bottom of the column, high-purity methyl tert-butyl ether fractions can be obtained simultaneously. The product is then continuously stripped, condensed, and filtered to obtain the final product. This process achieves a highly efficient preparation process combining reaction enhancement and separation enhancement, offering advantages such as high conversion rate, high selectivity, and excellent product purity.

[0027] Furthermore, the methanol recovery process includes the following steps:

[0028] The methanol and C4 fraction after etherification (post-etherification C4) from the top of the 233 distillate are collected, cooled, and then fed into a methanol-water washing tower. The methanol is mixed with the aqueous phase in the tower, dissolving in the aqueous phase and separating from the post-etherification C4. After collecting the post-etherification C4, the methanol-water solution is sent to a methanol recovery tower. The separated methanol and water are collected, and the methanol is recycled in a recovery tank. The water at the bottom of the tower can also be fed back into the methanol-water washing tower to further aid in the separation of methanol and post-etherification C4, thus completing the methanol recovery process.

[0029] This process utilizes the high solubility of methanol in the aqueous phase to separate the methanol obtained from the 233 top and the C4 fraction after etherification through aqueous phase extraction in a methanol-water washing tower. The etherified C4 fraction is directly recovered, while the methanol-containing aqueous phase further enters the methanol recovery tower, where methanol and water are effectively separated through catalytic fractionation. The obtained methanol is returned to the system for recycling, while the aqueous phase at the bottom of the tower is recirculated back to the water washing tower to continue participating in extraction, achieving a closed-loop circulation of the aqueous phase and methanol. This significantly reduces methanol loss and improves the utilization rate of raw materials and the overall economic efficiency of the process.

[0030] The beneficial effects of this invention are:

[0031] 1. In the catalytic synthesis process of methyl tert-butyl ether, this invention uses a modified strong acid cation exchange resin as a catalyst. By introducing a mesoporous silica structure in situ into the strong acid cation exchange resin, the reactants methanol and isobutylene can more easily enter the interior of the ion exchange resin catalyst, thereby significantly improving the accessibility and utilization rate of the acidic sites of sulfonic acid groups in the resin. At the same time, by introducing sulfonic acid group imidazole trifluoromethanesulfonate ionic liquid to modify the resin, its hydrophobic segments can promote the enrichment and residence of isobutylene near the acidic sites in the resin, while reducing the competitive adsorption of polar molecules such as methanol on the acidic sites, allowing more internal acidic sites to effectively participate in the reaction, thus providing a more stable and efficient solid acid catalytic basis for the efficient catalytic synthesis of methyl tert-butyl ether.

[0032] 2. In the catalytic synthesis process of methyl tert-butyl ether, this invention uses a modified strong acid cation exchange resin as a catalyst. The multi-level pore network constructed inside the resin by mesoporous silica provides sufficient space for the loading and dispersion of ionic liquids, allowing the ionic liquids to be more uniformly distributed in the acidic region inside the resin, avoiding their confinement to the outer surface of the particles. On the other hand, the introduced sulfonic acid imidazole trifluoromethanesulfonate ionic liquid, through its stable ionic structure and strong electron-withdrawing groups, regulates the acidic microenvironment around the sulfonic acid groups in the resin, further enhancing the acidity and reactivity of the sulfonic acid groups in the mesopores. This effectively activates the internal acidic sites with low utilization rates, enabling them to participate in the etherification reaction, promoting the uniform progress of the methyl tert-butyl ether synthesis reaction on the catalyst, which is beneficial for improving reaction conversion efficiency, stabilizing catalytic performance, and improving the catalyst's performance in continuous operation processes.

[0033] 3. In the catalytic synthesis process of methyl tert-butyl ether, this invention uses a modified strong acid cation exchange resin as a catalyst in both the etherification reaction and the separation and purification process. This allows the same catalytic system to run through the reaction and post-treatment processes, forming a synergistic overall catalytic flow. The synthesis of methyl tert-butyl ether is a typical reversible etherification reaction. Its conversion degree is not only controlled by the reaction conditions but also closely related to the effective concentration distribution of reactants at acidic sites in the catalyst. The synergistic modification of the strong acid cation exchange resin by mesoporous silica and sulfonated imidazole trifluoromethanesulfonate ionic liquid promotes the enrichment of isobutylene near the acidic sites and inhibits the competitive adsorption of polar molecules on the active centers. This drives the reaction equilibrium towards the formation of methyl tert-butyl ether in a localized region inside the catalyst. This not only improves the overall conversion efficiency of the etherification reaction but also helps to avoid rapid catalyst deactivation by increasing the utilization rate of acidic sites, thus improving the reaction efficiency and long-term stability of the catalyst in the synthesis process of methyl tert-butyl ether. Attached Figure Description

[0034] Figure 1This is a flowchart of the synthesis process of methyl tert-butyl ether according to the present invention. Detailed Implementation

[0035] 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.

[0036] Example 1: This example provides a modified strong acid cation exchange resin for the catalytic synthesis of methyl tert-butyl ether. Please refer to [link to example]. Figure 1 Specifically, it is prepared through the following steps:

[0037] S1: Place 40g of N-butylimidazole and 40g of 1,4-butanesulfonic acid lactone in a reaction vessel and stir at 200r / min at 80℃ for 18h. After the reaction is completed, cool to room temperature, filter, wash the filter cake twice with anhydrous diethyl ether, and dry under vacuum at 60℃ to constant weight to obtain sulfonylimidazole lactone.

[0038] S2: Place 60g of sulfonyl imidazole inner salt and 60g of trifluoromethanesulfonic acid in a reaction vessel and stir at 2000r / min at 80℃ for 68h. After the reaction is completed, cool to room temperature and add an extraction solution (the extraction solution is obtained by mixing deionized water and diethyl ether at a volume ratio of 1:4). Extract twice and collect the lower aqueous phase. Place the aqueous phase in a vacuum drying oven at 90℃ and dry it under vacuum to constant weight to obtain sulfonyl imidazole trifluoromethanesulfonate ionic liquid.

[0039] S3: 400g of sulfonate-type macroporous ion exchange resin, 80g of hexadecyltrimethylammonium bromide, 100g of tetraethyl orthosilicate, 1L of ethanol and 600mL of deionized water were placed in a reaction vessel and stirred at 200r / min for 1h at 25℃. Then, 500mL of 0.2mol / L ammonia solution was added and stirred at 300r / min for 2h at 40℃. After cooling to 25℃, the mixture was filtered, and the filter cake was added to 700mL of 1mol / L hydrochloric acid solution. The mixture was stirred at the same rate for 10h at 50℃. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid phase was collected to obtain sulfonate-type supported mesoporous silica ion exchange resin.

[0040] S4: 300g of sulfonic acid-supported mesoporous silica ion exchange resin, 50g of sulfonic acid imidazole trifluoromethanesulfonate ionic liquid and 2L of anhydrous ethanol were placed in a reaction vessel and impregnated at 200r / min at 40℃ for 12h. After impregnation, the mixture was filtered and the filter cake was vacuum dried at 60℃ for 10h to obtain the modified strong acid cation exchange resin.

[0041] Example 2: This example provides a modified strong acid cation exchange resin for the catalytic synthesis of methyl tert-butyl ether, prepared through the following steps:

[0042] S1: Place 50g of N-butylimidazole and 50g of 1,4-butanesulfonic acid lactone in a reaction vessel and stir at 250r / min at 85℃ for 22h. After the reaction is completed, cool to room temperature, filter, wash the filter cake three times with anhydrous diethyl ether, and dry it under vacuum at 70℃ to constant weight to obtain sulfonylimidazole lactone.

[0043] S2: Place 70g of sulfonyl imidazole inner salt and 70g of trifluoromethanesulfonic acid in a reaction vessel, stir at 250r / min at 85℃ for 70h, and after the reaction is completed, cool to room temperature, add extraction solution for extraction (the extraction solution is obtained by mixing deionized water and diethyl ether at a volume ratio of 1:4), extract 3 times, collect the lower aqueous phase, place the aqueous phase in a vacuum drying oven at 95℃, and vacuum dry to constant weight to obtain sulfonyl imidazole trifluoromethanesulfonate ionic liquid.

[0044] S3: 500g of sulfonate-type macroporous ion exchange resin, 90g of hexadecyltrimethylammonium bromide, 150g of tetraethyl orthosilicate, 1.2L of ethanol and 700mL of deionized water were placed in a reaction vessel and stirred at 250r / min at 30℃ for 1.5h. 600mL of 0.2mol / L ammonia solution was added and stirred at 350r / min at 45℃ for 3h. After cooling to 30℃, the mixture was filtered, and the filter cake was added to 800mL of 1mol / L hydrochloric acid solution. The mixture was stirred at the same rate at 55℃ for 11h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid phase was collected to obtain sulfonate-type supported mesoporous silica ion exchange resin.

[0045] S4: 400g of sulfonic acid-supported mesoporous silica ion exchange resin, 80g of sulfonic acid imidazole trifluoromethanesulfonate ionic liquid and 1.5L of anhydrous ethanol were placed in a reaction vessel and impregnated at 250r / min at 50℃ for 13h. After impregnation, the mixture was filtered and the filter cake was vacuum dried at 65℃ for 11h to obtain the modified strong acid cation exchange resin.

[0046] Example 3: This example provides a modified strong acid cation exchange resin for the catalytic synthesis of methyl tert-butyl ether, prepared through the following steps:

[0047] S1: 60g of N-butylimidazole and 60g of 1,4-butanesulfonate lactone were placed in a reaction vessel and stirred at 300r / min at 90℃ for 24h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed 4 times with anhydrous diethyl ether and dried under vacuum at 80℃ to constant weight to obtain sulfonate imidazolium lactone.

[0048] S2: Place 80g of sulfonyl imidazole inner salt and 80g of trifluoromethanesulfonic acid in a reaction vessel, stir at 300r / min at 90℃ for 72h. After the reaction is completed, cool to room temperature, add extraction solution for extraction, extract 4 times, collect the lower phase, place the aqueous phase in a vacuum drying oven at 100℃ and vacuum dry to constant weight to obtain sulfonyl imidazole trifluoromethanesulfonate ionic liquid.

[0049] S3: 600g of sulfonate-type macroporous ion exchange resin, 100g of hexadecyltrimethylammonium bromide, 200g of tetraethyl orthosilicate, 1.5L of ethanol and 800mL of deionized water were placed in a reaction vessel and stirred at 300r / min at 35℃ for 2h. Then, 700mL of 0.2mol / L ammonia solution was added and stirred at 400r / min at 50℃ for 4h. After cooling to 35℃, the mixture was filtered, and the filter cake was added to 900mL of 1mol / L hydrochloric acid solution. The mixture was stirred at the same rate at 60℃ for 12h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the solid phase was collected to obtain sulfonate-type supported mesoporous silica ion exchange resin.

[0050] S4: 500g of sulfonic acid-supported mesoporous silica ion exchange resin, 100g of sulfonic acid imidazole trifluoromethanesulfonate ion liquid and 3L of anhydrous ethanol were placed in a reaction vessel and impregnated at 300r / min at 60℃ for 14h. After impregnation, the mixture was filtered and the filter cake was vacuum dried at 70℃ for 12h to obtain the modified strong acid cation exchange resin.

[0051] The modified strong acid cation exchange resins prepared in Examples 1-3 above were first subjected to a lactone ring-opening addition reaction between N-butylimidazolium and 1,4-sulfonyl lactone. The nucleophilic sites on the imidazolium ring attacked the sulfonyl lactone, generating a sulfonyl imidazolium inner salt with sulfonic acid functional groups. Subsequently, this inner salt underwent protonation and anion exchange reactions with trifluoromethanesulfonic acid. Trifluoromethanesulfonic acid donated protons to further acidify the imidazolium cation, thereby obtaining a sulfonyl imidazolium trifluoromethanesulfonate ionic liquid with two acidic sites. Then, a hexadecyltrimethylammonium bromide template agent was introduced onto the surface of the sulfonate-type macroporous ion exchange resin, and tetraethyl orthosilicate under ammonia catalysis underwent a sol-gel polycondensation reaction. The template agent and silicon source formed a condensation reaction in the macroporous ion exchange resin. Simultaneous diffusion and hydrolysis-condensation occur both inside and outside the resin structure, forming a regular mesoporous silica layer on the resin surface and allowing in-situ growth of a mesoporous silica framework within its internal channels. After removing the template agent through acid treatment, hydrogen ions in the acid solution exchange with the original sulfonate groups of the resin, converting them into hydrogen sulfonate groups, thus obtaining a sulfonate-supported mesoporous silica ion exchange resin. Subsequently, using ethanol as a solvent, the ionic liquid gradually accumulates in the mesoporous silica channels of the outer and inner layers and is firmly anchored in the mesoporous framework through electrostatic adsorption and hydrogen bonding with silanol groups and resin sulfonate groups, thereby achieving uniform fixation of the ionic liquid throughout the entire ion exchange resin, resulting in a modified strongly acidic cation exchange resin.

[0052] Example 4: This example provides a catalytic synthesis process for methyl tert-butyl ether, including the following steps:

[0053] Step 1: Place the pre-etherified C4, methanol, and modified strong acid cation exchange resin in a static mixer at the inlet of the etherification reaction system. Stir and mix at 200 r / min for 20 min at 50 °C. Add the mixed material to the etherification reactor from the top of the reactor. Continue the reaction at 70 °C and 0.8 MPa pressure for 2 h. After the reaction is completed, cool to 40 °C and collect the reaction material to obtain crude methyl tert-butyl ether.

[0054] Step 2: Crude methyl tert-butyl ether is added to a catalytic distillation column. Modified strong acid cation exchange resin is added to the middle layer of the column. Under a temperature gradient of 70°C at the bottom and 30°C at the top, the pressure at the top of the column is adjusted to 0.2 MPa, and catalytic fractionation is carried out for 2 hours. The top of the column contains methanol and the C4 fraction after etherification (post-etherification C4). A high-purity methyl tert-butyl ether vapor fraction is formed in the middle of the column, and the bottom of the column contains the heavy component (C9). The high-purity methyl tert-butyl ether vapor fraction is continuously collected and cooled to 25°C in a condenser to convert it into a liquid phase. The liquid is filtered to remove impurities and the filtrate is collected to obtain methyl tert-butyl ether.

[0055] Step 3: During the separation process in the catalytic distillation column in Step 2, the C4 etherified material is collected at the top of the column, cooled, and then enters the methanol washing column. It mixes with the aqueous phase in the methanol washing column, and the methanol dissolves in the aqueous phase to separate from the C4 etherified material. After collecting the C4 etherified material, the methanol-water solution is sent to the methanol recovery column. The separation is carried out by taking advantage of the fact that methanol has a lower boiling point than water. The top of the column contains methanol with a lower boiling point, and the bottom of the column contains water. The separated methanol and water are collected. The methanol at the top of the column can be recovered and used as a raw material for the etherification reaction in Step 1. The water at the bottom of the column can also enter the methanol washing column to further help separate methanol and C4 etherified material, forming a cycle and completing the methanol recovery process.

[0056] Example 5: This example provides a catalytic synthesis process for methyl tert-butyl ether, including the following steps:

[0057] Step 1: Place the pre-etherified C4, methanol, and modified strong acid cation exchange resin in a static mixer at the inlet of the etherification reaction system. Stir and mix at 250 r / min for 30 min at 60 °C. Add the mixed material to the etherification reactor from the top of the reactor. Continue the reaction at 80 °C and 1.2 MPa pressure for 3 h. After the reaction is completed, cool to 50 °C and collect the reaction material to obtain crude methyl tert-butyl ether.

[0058] Step 2: Crude methyl tert-butyl ether is added to a catalytic distillation column. Modified strong acid cation exchange resin is added to the middle layer of the column. Under a temperature gradient of 75°C at the bottom and 40°C at the top, the pressure at the top of the column is adjusted to 0.3 MPa, and catalytic fractionation is carried out for 3 hours. The top of the column contains methanol and the C4 fraction after etherification (post-etherification C4). A high-purity methyl tert-butyl ether vapor fraction is formed in the middle of the column, and the bottom of the column contains the heavy component (C9). The high-purity methyl tert-butyl ether vapor fraction is continuously collected and cooled to 30°C in a condenser to convert it into a liquid phase. The liquid is filtered to remove impurities and the filtrate is collected to obtain methyl tert-butyl ether.

[0059] Example 6: This example provides a catalytic synthesis process for methyl tert-butyl ether, including the following steps:

[0060] Step 1: Place the pre-etherified C4, methanol, and modified strong acid cation exchange resin in a static mixer at the inlet of the etherification reaction system. Stir and mix at 300 r / min for 40 min at 70 °C. Add the mixed material to the etherification reactor from the top of the reactor. Continue the reaction at 90 °C and 1.5 MPa pressure for 4 h. After the reaction is completed, cool to 60 °C and collect the reaction material to obtain crude methyl tert-butyl ether.

[0061] Step 2: Add crude methyl tert-butyl ether to a catalytic distillation column. Add modified strong acid cation exchange resin to the middle layer of the column. Under a temperature gradient of 80℃ at the bottom and 45℃ at the top, adjust the pressure at the top of the column to 0.5MPa and carry out catalytic fractionation for 4 hours. The top of the column contains methanol and the C4 fraction after etherification (post-etherification C4). A high-purity methyl tert-butyl ether vapor fraction is formed in the middle of the column, and the bottom of the column contains the heavy component (C9). After continuously collecting the high-purity methyl tert-butyl ether vapor fraction, it is cooled to 25-35℃ in a condenser to be converted into a liquid phase. Filter to remove impurities and collect the filtrate to obtain methyl tert-butyl ether.

[0062] Comparative Example 1: Based on Example 2, a commercially available large-pore strong acid cation exchange resin was used instead of the modified strong acid cation exchange resin, while the other steps remained unchanged.

[0063] Comparative Example 2: Based on Example 2, a commercially available imidazole trifluoromethanesulfonate ionic liquid was used instead of the sulfonic acid imidazole trifluoromethanesulfonate ionic liquid prepared in S2, while the other steps remained unchanged.

[0064] Comparative Example 3: Based on Example 2, the sulfonic acid-supported mesoporous silica ion exchange resin prepared in S3 was used to replace the modified strong acid cation exchange resin, while the other steps remained unchanged.

[0065] The commercially available, strongly acidic cation exchange resins purchased in the aforementioned examples and comparative examples were manufactured by DuPont, model AmberLite™ HPR2900 H, a hydrogen-form ion exchange resin with an average particle size of 800 μm and an average pore size of 30 nm; the sulfonate-type macroporous ion exchange resins were manufactured by DuPont, model AmberLite™ HPR2900 Na, a sodium-form ion exchange resin with an average particle size of 800 μm and an average pore size of 30 nm; the imidazole trifluoromethanesulfonate ionic liquid was manufactured by Shandong Xinyang Chemical Co., Ltd., CAS number 145022-44-2, named 1-ethyl-3-methylimidazolium trifluoromethanesulfonate; and the pre-ether C4 was manufactured by Anhui Yifeng Petrochemical Co., Ltd., containing 20 wt% isobutylene.

[0066] The strongly acidic cation exchange resins prepared in Examples 1-3 and Comparative Examples 1-3 were used to simulate the catalytic synthesis process of methyl tert-butyl ether, and their catalytic performance was evaluated. The test results are shown in Table 1.

[0067] Experimental preparation: A commonly used laboratory high-pressure autoclave etherification reaction apparatus (volume 0.5-1L) with stirring was used to simulate the etherification reaction conditions of pre-etherified C4 and methanol. The catalyst sample prepared above was washed with deionized water until the supernatant was clear and transparent, and then soaked in a mixture of methanol and water (volume ratio 1:1) for 2 hours. After that, it was sieved to a particle size of 0.4-0.6 mm and then used for catalytic performance testing.

[0068] Catalyst efficiency test: Referring to the etherification reaction method in Example 5, 50g of pretreated resin catalyst was weighed and loaded into a high-pressure stirred tank. Pre-ether C4 / methanol mixed feedstock was added according to the set molar ratio, based on isobutylene in pre-ether C4 (molar ratio of isobutylene to methanol was 1:1.1), and the feed mass was recorded. The mixture was premixed at 250r / min for 30min at 60℃, then heated to 80℃ and the system pressure was stabilized at 1.2MPa. The reaction was carried out under these conditions for 3h. The contents of methanol, isobutylene, and methyl tert-butyl ether were determined by gas chromatography, and the methanol conversion rate, isobutylene conversion rate, and methyl tert-butyl ether yield were calculated. Under the same reaction conditions, the higher the methyl tert-butyl ether yield (or isobutylene conversion rate), the higher the catalytic activity of the catalyst.

[0069] Catalyst utilization test: Referring to the standard in the catalytic performance test, under the same conditions, change the amount of catalyst and use gas chromatography to determine the content of methyl tert-butyl ether. When the content of methyl tert-butyl ether reaches 85%, record the amount of catalyst required. The less catalyst is used, the higher the catalyst utilization rate.

[0070] Table 1 Catalytic Performance Test Table

[0071] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Methyl tert-butyl ether content (%) 88.9 91.2 89.5 76.2 82.1 80.3 Methanol conversion rate (%) 90.0 92.5 91.0 79.0 84.0 86.0 Isobutylene conversion rate (%) 88.5 91.0 89.8 77.5 82.5 84.0 Methyl tert-butyl ether yield (%) 86.0 89.5 87.5 74.0 79.0 80.5 Catalyst dosage (g) 40 36 38 72 65 61

[0072] As shown in Table 1, the modified strong acid cation exchange resins prepared in Examples 1-3 exhibit better catalytic performance for methyl tert-butyl ether than those in Comparative Examples 1-3. This demonstrates that the modified strong acid cation exchange resins prepared in this invention, by constructing a mesoporous silica structure in situ within the resin and introducing a sulfonic acid imidazole trifluoromethanesulfonate ionic liquid to synergistically regulate acidic sites, successfully construct a modified strong acid solid acid catalytic system with both high acidic site density and excellent mass transfer performance. This significantly improves the effective contact probability and reaction rate of isobutylene and methanol within the resin, enhances the overall conversion efficiency and target product selectivity of the etherification reaction, and overcomes the problems of low acidic site utilization, reaction concentration on the outer surface of particles, and limited overall catalytic efficiency in existing resin-based solid acid catalysts. Consequently, it exhibits superior and more stable catalytic performance in the methyl tert-butyl ether synthesis process.

[0073] 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 process for the catalytic synthesis of methyl tert-butyl ether, characterized in that, Includes the following steps: Step 1: Using pre-etherified C4 and methanol as raw materials, and modified strong acid cation exchange resin as catalyst, the mixture is added to an etherification reactor to carry out an etherification reaction, yielding crude methyl tert-butyl ether. Step 2: Add crude methyl tert-butyl ether to a catalytic distillation column. Add a modified strong acid cation exchange resin to the middle layer of the column for catalytic fractionation. The top of the column is a mixture of methanol and post-ether C4. The middle of the column forms a gas phase fraction of high-purity methyl tert-butyl ether. The bottom of the column contains the heavy fraction. The post-ether C4, methanol, methyl tert-butyl ether and the heavy fraction are cooled and collected separately. Step 3: Add the mixture of methanol and C4 after etherification to the methanol-water washing tower. Separate the C4 after etherification at the top of the tower, cool it and collect it. Methanol and water enter the methanol separation tower to separate the aqueous phase. The separated aqueous phase is recycled in the separation tower, and the methanol enters the etherification reactor in Step 1 for recycling. The modified strong acid cation exchange resin is prepared by the following steps: Sulfonic acid-supported mesoporous silica ion exchange resin, sulfonic acid imidazole trifluoromethanesulfonate ionic liquid and anhydrous ethanol are placed in a reaction vessel and stirred and impregnated at 40-60℃ and 150-200r / min for 12-14h. After filtration, the filter cake is vacuum dried for 10-12h to obtain modified strong acid cation exchange resin. The sulfonic acid-supported mesoporous silica ion exchange resin is prepared by the following steps: Sulfonate-type macroporous ion exchange resin, hexadecyltrimethylammonium bromide, ethanol and deionized water were placed in a reaction vessel and reacted at 25-35℃ for 1-2 h. Then, 0.2 mol / L ammonia solution and tetraethyl orthosilicate were added and reacted at 50-60℃ for 2-4 h. The mixture was cooled to 25-30℃, filtered, and the filter cake was added to 1 mol / L hydrochloric acid solution and reacted at 50-60℃ for 10-12 h. The mixture was centrifuged and the solid phase was collected to obtain sulfonate-type supported mesoporous silica ion exchange resin. The sulfonyl imidazole trifluoromethanesulfonate ionic liquid is prepared by the following steps: Sulfonate imidazole inner salt and trifluoromethanesulfonic acid were placed in a reaction vessel and reacted at 80-90℃ for 68-72 h. After extraction, the mixture was dried under vacuum to constant weight to obtain sulfonate imidazole trifluoromethanesulfonate ionic liquid.

2. A process for catalytic synthesis of methyl tert-butyl ether according to claim 1, characterized by, The ratio of the sulfonic acid-supported mesoporous silica ion exchange resin, sulfonic acid imidazole trifluoromethanesulfonate ionic liquid, and anhydrous ethanol is 300-500g: 50-100g: 2-3L.

3. The process as claimed in claim 1, wherein the process is characterized by, The ratio of sulfonate-type macroporous ion exchange resin, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia solution, hydrochloric acid solution, ethanol and deionized water is 400-600g: 80-100g: 100-200g: 500-700mL: 700-900mL: 1-1.5L: 600-800mL.

4. The process as claimed in claim 1, wherein the process is characterized by, The mass ratio of the sulfonic acid imidazole inner salt to trifluoromethanesulfonic acid is 60-80:60-80.

5. The catalytic synthesis process for methyl tert-butyl ether according to claim 1, characterized in that, The sulfonyl imidazole inner salt is prepared by the following steps: N-Butylimidazole and 1,4-butanesulfonate lactone were placed in a reaction vessel and reacted at 80-90℃ for 18-24h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and vacuum dried to constant weight to obtain sulfonate imidazolium lactone.

6. The process according to claim 5, wherein the process is characterized by, The mass ratio of N-butylimidazole to 1,4-butanesulfonate lactone is 40-60:40-60.

7. The catalytic synthesis process for methyl tert-butyl ether according to claim 1, characterized in that, The reaction temperature of the etherification reactor in step one is 70-90℃ and the pressure is 0.8-1.5MPa.

8. The process as claimed in claim 1, wherein the process is characterized by, The temperature of the bottom of the catalytic distillation column described in step two is 70-80℃, the temperature of the top of the column is 30-45℃, and the pressure of the top of the column is 0.2-0.5MPa.

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