Preparation method of propylene glycol methyl ether acetate
By supporting molybdenum oxide catalyst with silica and modifying it with ionic liquid, the problems of difficult catalyst separation and poor thermal stability in transesterification were solved, and efficient preparation of propylene glycol methyl ether acetate was achieved, improving the raw material conversion rate and reaction selectivity.
Patent Information
- Application Number
- CN202511012121.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-22
- Publication Date
- 2025-11-21
AI Technical Summary
In existing methods for preparing propylene glycol methyl ether acetate, the transesterification reaction is inefficient, the catalyst is difficult to separate from the product, the thermal stability is poor, it is difficult to recycle, and the reaction conditions are not easy to control, resulting in high production costs and low efficiency.
A supported catalyst was prepared by using silica-supported molybdenum oxide catalyst and secondary modification of ionic liquid to prepare a supported catalyst for transesterification reaction, which improves the dispersion effect and thermal stability of the catalyst and enhances the mass transfer capacity of the reactants.
The catalyst and product are easily separated, have good thermal stability, can be recycled, improve the conversion rate of raw materials and the selectivity of the reaction, reduce the activation energy of the reaction, and improve the efficiency of the transesterification reaction.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of propylene glycol methyl ether acetate preparation technology, specifically relating to a method for preparing propylene glycol methyl ether acetate. Background Technology
[0002] Propylene glycol methyl ether acetate (PGMEA) is a high-grade solvent. Its molecule contains both ether bonds and carbonyl groups, with the carbonyl groups forming an ester structure, and also contains alkyl groups. The same molecule contains both nonpolar and polar regions, and the functional groups in these two regions both restrict and repel each other, while each playing its inherent role. Therefore, it has a certain degree of solubility for both nonpolar and polar substances.
[0003] The industrial synthesis processes of propylene glycol methyl ether acetate (PGMEA) mainly include direct esterification, epichlorohydrin one-step process, and transesterification. Among these, direct esterification dominates the industrial market due to its mature technology. This method uses propylene glycol methyl ether and acetic acid as reactants, and the esterification reaction is carried out under the action of an acidic catalyst. Traditional processes typically use strong inorganic acids (such as concentrated sulfuric acid, phosphoric acid, or hydrochloric acid) as catalysts. However, these catalysts are highly corrosive, easily damaging reaction equipment and generating large amounts of acidic wastewater and solid waste, posing a challenge to environmental remediation. Furthermore, this process usually relies on a single hydrocarbon solvent (such as cyclohexane) for azeotropic dehydration, leading to excessively high reaction temperatures, prolonged reaction cycles, and increased energy consumption. Simultaneously, the highly exothermic reaction process is difficult to control precisely, resulting in incomplete separation of the aqueous phase. More importantly, acetic acid readily forms an azeotrope with water, which is carried out of the system, thus reducing the reaction yield.
[0004] In comparison, transesterification is considered a promising alternative process due to its mild reaction conditions, simple process flow, and lower production costs. However, this route currently relies mainly on homogeneous catalytic systems, which suffer from technical bottlenecks such as difficulty in separating the catalyst from the product, poor thermal stability, difficulty in recycling, and limited feed conversion rate, thus restricting its large-scale industrial application. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing propylene glycol methyl ether acetate, so as to solve the problem of low efficiency in the preparation of propylene glycol methyl ether acetate by transesterification reaction.
[0006] The objective of this invention can be achieved through the following technical solutions:
[0007] A method for preparing propylene glycol methyl ether acetate includes the following steps:
[0008] Propylene glycol methyl ether and methyl acetate were mixed, and a catalyst was added to carry out a transesterification reaction. The catalyst was prepared by the following steps: preparing a supported molybdenum oxide supported on silica to obtain a supported catalyst, and then modifying the supported catalyst with an ionic liquid.
[0009] In some possible implementations, the molar ratio of propylene glycol methyl ether to methyl acetate is 1:4-5;
[0010] The catalyst is added at a rate of 4% to 6% of the total mass of propylene glycol methyl ether and methyl acetate.
[0011] The reaction temperature is 120-130℃; the reaction time is 4-5 hours.
[0012] In some possible implementations, magnetic materials are introduced during the preparation of silica-supported molybdenum oxide to obtain a supported catalyst.
[0013] In some possible implementations, the introduction of magnetic materials during the preparation of silica-supported molybdenum oxide to obtain a supported catalyst includes the following steps:
[0014] Sodium dodecyl sulfonate and xylene were mixed and then an iron salt solution was added. The iron salt solution was a mixture of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and water. Under nitrogen protection, the temperature was raised to 80-90℃ and hydrazine hydrate solution was added. The reaction was stirred for 3-4 hours and then cooled to 35-45℃. Molybdenum oxide, tetraethyl silicate, and vinylsiloxane were added and the reaction was hydrolyzed for 20-30 hours. Ethanol was added to break the emulsion, and the catalyst was recovered using a magnet. The catalyst was washed with ethanol and deionized water and then freeze-dried to obtain the supported catalyst.
[0015] In some possible embodiments, the secondary modification includes the following steps: adding the supported catalyst and ionic liquid monomer to methanol, adding the initiator azobisisobutyronitrile and ultrasonically dispersing, then refluxing at 60°C for 40-48 hours under nitrogen protection, after the reaction is completed, heating to 80°C until all methanol evaporates, washing with methanol and water in sequence, and drying to obtain the catalyst.
[0016] In some possible implementations, the ratio of sodium dodecyl sulfonate to xylene is 1 g: 10 mL;
[0017] The iron salt solution is prepared by using ferric chloride tetrahydrate, ferric nitrate nonahydrate, and water in a ratio of 1.1-1.2 g: 4.8-5 g: 5-6 mL; the hydrazine hydrate solution has a mass fraction of 34%; and the ratio of the total amount of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and hydrazine hydrate solution to the total amount of hydrazine hydrate solution is 5.9-6.2 g: 6 mL.
[0018] In some possible implementations, the ratio of molybdenum oxide, tetraethyl silicate, and vinylsiloxane is 1-2 g: 10 mL: 12-16 mL.
[0019] In some possible embodiments, the vinylsiloxane is one of methacryloyloxypropyltrimethoxysilane and 7-octenyltrimethoxysilane.
[0020] In some possible implementations, the mass ratio of the supported catalyst to the ionic liquid monomer is 3:0.8-1; the amount of initiator added is 1% to 2% of the mass of the ionic liquid.
[0021] In some possible embodiments, the ionic liquid monomer is one of 1-propylsulfonic acid-3-vinylimidazolium chloride and 1-allyl-3-ethylimidazolium chloride.
[0022] The beneficial effects of this invention are:
[0023] This invention provides a method for preparing propylene glycol methyl ether acetate. The self-made catalyst used in this method has good catalytic effect. The catalyst system in this invention is different from the homogeneous catalytic system. The catalyst in this invention is easy to separate from the product, has good thermal stability, can be recycled, and improves the conversion rate of raw materials.
[0024] The catalyst in this invention is made by combining molybdenum oxide and a secondary modified ionic liquid. On the one hand, it improves the dispersion of the catalyst in the reaction system. On the other hand, the low viscosity and high fluidity of the ionic liquid facilitate the rapid mass transfer of reactants and products, and can provide more acidic sites, reduce the activation energy of the reaction, and thus improve the selectivity of the reaction. Detailed Implementation
[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0026] The following is a detailed description of a method for preparing propylene glycol methyl ether acetate according to an embodiment of this application.
[0027] This application provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0028] Propylene glycol methyl ether and methyl acetate were mixed, and a catalyst was added to carry out a transesterification reaction. The catalyst was prepared by the following steps: preparing a supported molybdenum oxide supported on silica to obtain a supported catalyst, and then modifying the supported catalyst with an ionic liquid.
[0029] In some specific embodiments, the molar ratio of propylene glycol methyl ether to methyl acetate is 1:4-5;
[0030] The catalyst is added at a rate of 4% to 6% of the total mass of propylene glycol methyl ether and methyl acetate.
[0031] The reaction temperature is 120-130℃; the reaction time is 4-5 hours.
[0032] In some possible implementations, magnetic materials are introduced during the preparation of silica-supported molybdenum oxide to obtain a supported catalyst.
[0033] In some possible implementations, the introduction of magnetic materials during the preparation of silica-supported molybdenum oxide to obtain a supported catalyst includes the following steps:
[0034] Sodium dodecyl sulfonate and xylene were mixed and then an iron salt solution was added. The iron salt solution was a mixture of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and water. Under nitrogen protection, the temperature was raised to 80-90℃ and hydrazine hydrate solution was added. The reaction was stirred for 3-4 hours and then cooled to 35-45℃. Molybdenum oxide, tetraethyl silicate, and vinylsiloxane were added and the reaction was hydrolyzed for 20-30 hours. Ethanol was added to break the emulsion, and the catalyst was recovered using a magnet. The catalyst was washed with ethanol and deionized water and then freeze-dried to obtain the supported catalyst.
[0035] In some possible embodiments, the secondary modification includes the following steps: adding the supported catalyst and ionic liquid monomer to methanol, adding the initiator azobisisobutyronitrile and ultrasonically dispersing, then refluxing at 60°C for 40-48 hours under nitrogen protection, after the reaction is completed, heating to 80°C until all methanol evaporates, washing with methanol and water in sequence, and drying to obtain the catalyst.
[0036] In some specific embodiments, in step S1, the ratio of sodium dodecyl sulfonate to xylene is 1g:10mL; the ratio of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and water in the iron salt solution is 1.1-1.2g:4.8-5g:5-6mL; the mass fraction of the hydrazine hydrate solution is 34%; and the ratio of the total amount of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and hydrazine hydrate solution is 5.9-6.2g:6mL.
[0037] In some specific embodiments, the ratio of molybdenum oxide, tetraethyl silicate, and vinylsiloxane is 1-2 g: 10 mL: 12-16 mL.
[0038] In some specific embodiments, the vinylsiloxane is one of methacryloyloxypropyltrimethoxysilane and 7-octenyltrimethoxysilane.
[0039] In some specific embodiments, the mass ratio of the supported catalyst to the ionic liquid monomer in step S2 is 3:0.8-1; the amount of initiator added is 1% to 2% of the mass of the ionic liquid.
[0040] In some specific embodiments, the ionic liquid monomer is one of 1-propylsulfonic acid-3-vinylimidazolium chloride and 1-allyl-3-ethylimidazolium chloride. Preferably, the ionic liquid monomer is a -SO3H ionic liquid, which exhibits good catalytic activity.
[0041] The following is a detailed description with reference to specific examples.
[0042] Example 1
[0043] This embodiment provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0044] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:4, and a catalyst was added. The reaction temperature was set at 120℃, and the amount of catalyst added was 4% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 4 hours. After the reaction was completed, the catalyst was separated by water cooling to room temperature. The supernatant was retained by centrifugation, and relevant data were tested.
[0045] The catalyst is prepared through the following steps:
[0046] Step S1: Mix 10g sodium dodecyl sulfonate and 100mL xylene, add an iron salt solution (1.1g ferric chloride tetrahydrate, 4.8g ferric nitrate nonahydrate, and 5mL water), heat to 80℃ under nitrogen protection, add 6mL of 34% (w / w) hydrazine hydrate solution as a reducing agent, continue stirring for 3h, cool to 35℃, add 1g molybdenum oxide, 10mL tetraethyl silicate, and 12mL methacryloyloxypropyltrimethoxysilane, hydrolyze for 20h, add 10% (w / w) of ethanol to break the emulsion, recover with a magnet, wash with ethanol and deionized water, and freeze-dry at -70℃ to obtain the supported catalyst.
[0047] Step S2, Secondary Modification: The supported catalyst and ionic liquid monomer were added to methanol, and the initiator azobisisobutyronitrile was added and ultrasonically dispersed. Under nitrogen protection, the mixture was refluxed at 60°C for 40 hours. After the reaction, the temperature was raised to 80°C until all the methanol evaporated. The mixture was washed successively with methanol and water, and dried to obtain the catalyst. The mass ratio of the supported catalyst to the ionic liquid monomer was 3:0.8; the amount of initiator added was 1% of the mass of the ionic liquid. The ionic liquid monomer was 1-propylsulfonic acid-3-vinylimidazolium chloride.
[0048] Example 2
[0049] This embodiment provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0050] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:5, and a catalyst was added. The reaction temperature was set at 120℃, and the amount of catalyst added was 4% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 4 hours. After the reaction was completed, the catalyst was separated by water cooling to room temperature. The supernatant was retained by centrifugation, and relevant data were tested.
[0051] The catalyst used is the same as in Example 1.
[0052] Example 3
[0053] This embodiment provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0054] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:4, and a catalyst was added. The reaction temperature was set at 130℃, and the amount of catalyst added was 4% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 4 hours. After the reaction was completed, the catalyst was separated by water cooling to room temperature. The supernatant was retained by centrifugation, and relevant data were tested.
[0055] The catalyst used is the same as in Example 1.
[0056] Example 4
[0057] This embodiment provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0058] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:4, and a catalyst was added. The reaction temperature was set at 120℃, and the amount of catalyst added was 4% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 5 hours. After the reaction was completed, the catalyst was separated by water cooling to room temperature. The supernatant was retained by centrifugation, and relevant data were tested.
[0059] The catalyst used is the same as in Example 1.
[0060] Example 5
[0061] This embodiment provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0062] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:4, and a catalyst was added. The reaction temperature was set at 120℃, and the amount of catalyst added was 6% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 4 hours. After the reaction was completed, the catalyst was separated by water cooling to room temperature. The supernatant was retained by centrifugation, and relevant data were tested.
[0063] The catalyst used is the same as in Example 1.
[0064] Example 6
[0065] This embodiment provides a method for preparing propylene glycol methyl ether acetate, which differs from Example 1 in that the catalyst preparation process is different. Specifically, the catalyst is prepared through the following steps:
[0066] Step S1: Mix 10g sodium dodecyl sulfonate and 100mL xylene, add an iron salt solution (1.1g ferric chloride tetrahydrate, 4.8g ferric nitrate nonahydrate, and 5mL water), heat to 80℃ under nitrogen protection, add 6mL of 34% (w / w) hydrazine hydrate reducing agent, continue stirring for 3h, cool to 35℃, add 2g molybdenum oxide, 10mL tetraethyl silicate, and 12mL methacryloyloxypropyltrimethoxysilane, hydrolyze for 20h, add 10% (w / w) of ethanol to demulsify, recover with a magnet, wash with ethanol and deionized water, and freeze-dry at -70℃ to obtain the supported catalyst.
[0067] Step S2, Secondary Modification: The supported catalyst and ionic liquid monomer were added to methanol, and the initiator azobisisobutyronitrile was added and ultrasonically dispersed. Under nitrogen protection, the mixture was refluxed at 60°C for 40 hours. After the reaction, the temperature was raised to 80°C until all the methanol evaporated. The mixture was washed successively with methanol and water, and dried to obtain the catalyst. The mass ratio of the supported catalyst to the ionic liquid monomer was 3:0.8; the amount of initiator added was 1% of the mass of the ionic liquid. The ionic liquid monomer was 1-propylsulfonic acid-3-vinylimidazolium chloride.
[0068] Example 7
[0069] This embodiment provides a method for preparing propylene glycol methyl ether acetate, which differs from Example 1 in that the catalyst preparation process is different. Specifically, the catalyst is prepared through the following steps:
[0070] Step S1: Mix 10g sodium dodecyl sulfonate and 100mL xylene, add an iron salt solution (1.1g ferric chloride tetrahydrate, 4.8g ferric nitrate nonahydrate, and 5mL water), heat to 80℃ under nitrogen protection, add 6mL of 34% (w / w) hydrazine hydrate reducing agent, continue stirring for 3h, cool to 35℃, add 1g molybdenum oxide, 10mL tetraethyl silicate, and 12mL 7-octenyltrimethoxysilane, hydrolyze for 20h, add 10% (w / w) of ethanol to demulsify, recover with a magnet, wash with ethanol and deionized water, and freeze-dry at -70℃ to obtain the supported catalyst.
[0071] Step S2, Secondary Modification: The supported catalyst and ionic liquid monomer were added to methanol, and the initiator azobisisobutyronitrile was added and ultrasonically dispersed. Under nitrogen protection, the mixture was refluxed at 60°C for 40 hours. After the reaction, the temperature was raised to 80°C until all the methanol evaporated. The mixture was washed successively with methanol and water, and dried to obtain the catalyst. The mass ratio of the supported catalyst to the ionic liquid monomer was 3:0.8; the amount of initiator added was 1% of the mass of the ionic liquid. The ionic liquid monomer was 1-propylsulfonic acid-3-vinylimidazolium chloride.
[0072] Example 8
[0073] This embodiment provides a method for preparing propylene glycol methyl ether acetate, which differs from Example 1 in that the catalyst preparation process is different. Specifically, the catalyst is prepared through the following steps:
[0074] Step S1: Mix 10g sodium dodecyl sulfonate and 100mL xylene, add an iron salt solution (1.1g ferric chloride tetrahydrate, 4.8g ferric nitrate nonahydrate, and 5mL water), heat to 80℃ under nitrogen protection, add 6mL of 34% (w / w) hydrazine hydrate solution as a reducing agent, continue stirring for 3h, cool to 35℃, add 1g molybdenum oxide, 10mL tetraethyl silicate, and 12mL methacryloyloxypropyltrimethoxysilane, hydrolyze for 20h, add 10% (w / w) of ethanol to break the emulsion, recover with a magnet, wash with ethanol and deionized water, and freeze-dry at -70℃ to obtain the supported catalyst.
[0075] Step S2, Secondary Modification: The supported catalyst and ionic liquid monomer were added to methanol, and the initiator azobisisobutyronitrile was added and ultrasonically dispersed. Under nitrogen protection, the mixture was refluxed at 60°C for 40 hours. After the reaction, the temperature was raised to 80°C until all the methanol evaporated. The mixture was washed successively with methanol and water, and dried to obtain the catalyst. The mass ratio of the supported catalyst to the ionic liquid monomer was 3:0.8; the amount of initiator added was 1% of the mass of the ionic liquid. The ionic liquid monomer was 1-allyl-3-ethylimidazolium chloride.
[0076] Comparative Example 1
[0077] The difference between this comparative example and Example 1 is that the catalyst is different; no secondary modification is performed, and a supported catalyst is used as the catalyst. 10g of sodium dodecyl sulfonate and 100mL of xylene are mixed, and an iron salt solution is added. The iron salt solution is a mixture of 1.1g of ferric chloride tetrahydrate, 4.8g of ferric nitrate nonahydrate, and 5mL of water. Under nitrogen protection, the temperature is raised to 80°C, and 6mL of a 34% (w / w) reducing agent hydrazine hydrate solution is added. The reaction is continued with stirring for 3 hours, then cooled to 35°C, and 1g of molybdenum oxide, 10mL of tetraethyl silicate, and 12mL of methacryloyloxypropyltrimethoxysilane are added. The reaction is hydrolyzed for 20 hours, and 10% (w / w) of the reaction volume of ethanol is added to break the emulsion. After recovery with a magnet, the mixture is washed with ethanol and deionized water, and then freeze-dried at -70°C to obtain the supported catalyst.
[0078] The remaining raw materials and preparation process are the same as in Example 1.
[0079] Comparative Example 2
[0080] The difference between this comparative example and Example 1 is that the catalyst is different; no secondary modification is performed, and methacryloyloxypropyltrimethoxysilane is not used. A supported catalyst is used instead: 10g of sodium dodecyl sulfonate and 100mL of xylene are mixed, and an iron salt solution is added. The iron salt solution is a mixture of 1.1g of ferric chloride tetrahydrate, 4.8g of ferric nitrate nonahydrate, and 5mL of water. Under nitrogen protection, the temperature is raised to 80°C, and 6mL of a 34% (w / w) reducing agent hydrazine hydrate solution is added. The reaction is stirred for 3 hours, then cooled to 35°C, and 1g of molybdenum oxide and 22mL of tetraethyl silicate are added. The hydrolysis reaction is carried out for 20 hours. Ethanol (10% by volume of the reaction liquid) is added to break the emulsion. After recovery with a magnet, the mixture is washed with ethanol and deionized water, and then freeze-dried at -70°C to obtain the supported catalyst.
[0081] The remaining raw materials and preparation process are the same as in Example 1.
[0082] Comparative Example 3
[0083] This comparative example provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0084] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:4, and a catalyst prepared according to the method in Comparative Example 1 was added. The reaction temperature was set at 120℃, and the amount of catalyst added was 4% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 5 hours. After the reaction was completed, the catalyst was cooled to room temperature with water and then separated. The supernatant liquid phase was retained by centrifugation, and relevant data were tested.
[0085] Comparative Example 4
[0086] This comparative example provides a method for preparing propylene glycol methyl ether acetate, comprising the following steps:
[0087] Propylene glycol methyl ether and methyl acetate were mixed at a molar ratio of 1:4, and a catalyst prepared according to the method in Comparative Example 2 was added. The reaction temperature was set at 120℃, and the amount of catalyst added was 4% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction was carried out for 5 hours. After the reaction was completed, the catalyst was cooled to room temperature with water and then separated. The supernatant liquid phase was retained by centrifugation, and relevant data were tested.
[0088] Comparative Example 5
[0089] The difference between this comparative example and Example 1 lies in the catalyst; the catalyst was prepared through the following steps:
[0090] Step S1: Mix 10g sodium dodecyl sulfonate and 100mL xylene, add an iron salt solution (1.1g ferric chloride tetrahydrate, 4.8g ferric nitrate nonahydrate, and 5mL water), heat to 80℃ under nitrogen protection, add 6mL of 34% (w / w) hydrazine hydrate solution as a reducing agent, continue stirring for 3h, cool to 35℃, add 1g molybdenum oxide, 10mL tetraethyl silicate, and 12mL vinyltrimethoxysilane, hydrolyze for 20h, add 10% (w / w) of ethanol to demulsify, recover with a magnet, wash with ethanol and deionized water, and freeze-dry at -70℃ to obtain the supported catalyst.
[0091] Step S2, Secondary Modification: The supported catalyst and ionic liquid monomer were added to methanol, and the initiator azobisisobutyronitrile was added and ultrasonically dispersed. Under nitrogen protection, the mixture was refluxed at 60°C for 40 hours. After the reaction, the temperature was raised to 80°C until all the methanol evaporated. The mixture was washed successively with methanol and water, and dried to obtain the catalyst. The mass ratio of the supported catalyst to the ionic liquid monomer was 3:0.8; the amount of initiator added was 1% of the mass of the ionic liquid. The ionic liquid monomer was 1-propylsulfonic acid-3-vinylimidazolium chloride.
[0092] The conversion rates of propylene glycol methyl ether in Examples 1-8 and Comparative Examples 1-5 were recorded. The conversion rate of propylene glycol methyl ether = number of moles of propylene glycol methyl ether consumed / initial number of moles of propylene glycol methyl ether. The results are shown in Table 1.
[0093] Table 1
[0094] project Conversion rate / % Example 1 62.5 Example 2 62.4 Example 3 62.3 Example 4 62.5 Example 5 62.6 Example 6 61.8 Example 7 63.0 Example 8 60.8 Comparative Example 1 52.3 Comparative Example 2 45.1 Comparative Example 3 52.6 Comparative Example 4 45.3 Comparative Example 5 57.6
[0095] The self-made catalyst used in the preparation method of propylene glycol methyl ether acetate in this invention has good catalytic effect. Examples 1-8 underwent secondary modification, while the catalyst in Comparative Example 1 did not undergo secondary modification. The ionic liquid introduced into the catalyst resulted in a conversion rate of propylene glycol methyl ether greater than 60%. The selected -SO3H ionic liquid exhibited superior catalytic activity, and in the repeatability test, the catalysts in Examples 1-8 showed no significant decrease in catalytic performance after being recovered and reused five times.
[0096] In Comparative Example 2, a supported catalyst was used, with molybdenum oxide as the active component. Compared to Comparative Example 1, the catalytic performance of Comparative Example 2 was poor. Both Comparative Example 1 and Comparative Example 2 are supported catalysts. Compared to Comparative Example 2, Comparative Example 1 introduced a hydrophobic long chain through methacryloyloxypropyltrimethoxysilane. Compared to Comparative Example 2, the catalyst of Comparative Example 1 is more conducive to forming a micro-sized and stable reaction system, improving the reaction efficiency of the reactants propylene glycol methyl ether and methyl acetate, and increasing the conversion rate of propylene glycol methyl ether. A comparison of Comparative Examples 1-5 and Example 1 shows that Example 1, by combining molybdenum oxide with a secondary modified ionic liquid, improves the dispersion of the catalyst in the reaction system. Furthermore, the low viscosity and high fluidity of the ionic liquid facilitate rapid mass transfer between reactants and products, and provide more acidic sites, reducing the activation energy of the reaction and thus improving the selectivity. Combining molybdenum oxide with the secondary modified ionic liquid and introducing hydrophobic long chains can further improve the conversion rate of the reactants, fully utilize the synergistic catalytic effect of the catalyst, improve the contact and mass transfer efficiency of the reactants, enhance the activation of the reactants, and improve the selectivity of the reaction.
[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0098] 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, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing propylene glycol methyl ether acetate, characterized in that, Includes the following steps: Propylene glycol methyl ether and methyl acetate were mixed, and a catalyst was added to carry out a transesterification reaction. The catalyst was prepared by the following steps: preparing a supported molybdenum oxide supported on silica to obtain a supported catalyst, and then modifying the supported catalyst with an ionic liquid.
2. The method for preparing propylene glycol methyl ether acetate according to claim 1, characterized in that, The molar ratio of propylene glycol methyl ether to methyl acetate is 1:4-5; The catalyst is added at a rate of 4% to 6% of the total mass of propylene glycol methyl ether and methyl acetate. The reaction temperature is 120-130℃; the reaction time is 4-5 hours.
3. The method for preparing propylene glycol methyl ether acetate according to claim 1, characterized in that, Magnetic materials were introduced during the preparation of silica-supported molybdenum oxide to obtain a supported catalyst.
4. The method for preparing propylene glycol methyl ether acetate according to claim 3, characterized in that, The process of introducing magnetic materials during the preparation of silica-supported molybdenum oxide to obtain a supported catalyst includes the following steps: Sodium dodecyl sulfonate and xylene were mixed and then added to an iron salt solution, which was a mixture of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and water. Under nitrogen protection, the temperature was raised to 80-90℃ and hydrazine hydrate solution was added. The mixture was stirred and reacted for 3-4 hours. The temperature was then lowered to 35-45℃ and molybdenum oxide, tetraethyl silicate, and vinylsiloxane were added. The mixture was hydrolyzed for 20-30 hours. Ethanol was added to break the emulsion, and the mixture was recovered using a magnet. The mixture was then washed with ethanol and deionized water and freeze-dried.
5. The method for preparing propylene glycol methyl ether acetate according to claim 1, characterized in that, The secondary modification includes the following steps: adding the supported catalyst and ionic liquid monomer to methanol, adding an initiator and ultrasonically dispersing, then refluxing at 60°C for 40-48 hours under nitrogen protection. After the reaction is completed, the temperature is raised to 80°C until all the methanol evaporates, and the mixture is washed with methanol and water in sequence and then dried.
6. The method for preparing propylene glycol methyl ether acetate according to claim 4, characterized in that, The ratio of sodium dodecyl sulfonate to xylene is 1g:10mL; The iron salt solution is prepared by using ferric chloride tetrahydrate, ferric nitrate nonahydrate, and water in a ratio of 1.1-1.2 g: 4.8-5 g: 5-6 mL; the hydrazine hydrate solution has a mass fraction of 34%; and the ratio of the total amount of ferric chloride tetrahydrate, ferric nitrate nonahydrate, and hydrazine hydrate solution to the total amount of hydrazine hydrate solution is 5.9-6.2 g: 6 mL.
7. The method for preparing propylene glycol methyl ether acetate according to claim 4, characterized in that, The ratio of molybdenum oxide, tetraethyl silicate, and vinylsiloxane is 1-2 g: 10 mL: 12-16 mL.
8. The method for preparing propylene glycol methyl ether acetate according to claim 4, characterized in that, The vinylsiloxane is one of methacryloyloxypropyltrimethoxysilane and 7-octenyltrimethoxysilane.
9. The method for preparing propylene glycol methyl ether acetate according to claim 5, characterized in that, The mass ratio of the supported catalyst to the ionic liquid monomer is 3:0.8-1; the amount of initiator added is 1% to 2% of the mass of the ionic liquid.
10. The method for preparing propylene glycol methyl ether acetate according to claim 5, characterized in that, The ionic liquid monomer is one of 1-propylsulfonic acid-3-vinylimidazolium chloride and 1-allyl-3-ethylimidazolium chloride.