A process for the preparation of glycol methylene ethers from methanol and ethylene glycol

Abstract

The present application relates to the technical field of organic chemical industry, in particular to a method for preparing glycol methanol ethers reagent by methanol and ethylene glycol etherification. The method comprises raw material preparation and selective control of reaction path: mixing raw materials under nitrogen protection, molecular sieve and selective switching catalyst, and then separating glycol monomethyl ether under visible light irradiation and separating glycol dimethyl ether under ultraviolet light irradiation. The selective switching catalyst is prepared by preparing ZnInS nanorods, APTES pretreatment, constructing ZnInS / Ni composite and subsequent heat treatment and reduction, which contains gradient nickel loaded SiO2 shell and ZnInS core, and can regulate active sites and photoactive carrier activity. The method can directionally prepare target products, has high catalytic activity and stability, and has mild reaction conditions, and is suitable for efficient preparation of glycol methanol ethers reagent.

Description

Technical Field

[0001] This invention relates to the field of organic chemical technology, and in particular to a method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol. Background Technology

[0002] Ethylene glycol methyl ethers (including ethylene glycol monomethyl ether and ethylene glycol dimethyl ether) are an important class of fine chemical intermediates, widely used in coating solvents, pharmaceutical synthesis, battery electrolytes, and other fields. Their efficient preparation is of great significance to the chemical industry. Currently, methods for preparing these reagents through the etherification reaction of methanol and ethylene glycol commonly use catalysts including concentrated sulfuric acid and solid acids (such as molecular sieves and metal oxides), but existing technologies have significant limitations.

[0003] While traditional concentrated sulfuric acid catalysis is cost-effective, it suffers from severe equipment corrosion, numerous side reactions (such as ethylene glycol self-polymerization and methanol decomposition), and difficulties in product separation. Furthermore, it cannot selectively control the ratio of monomethyl ether to dimethyl ether. Solid acid catalysts can alleviate corrosion, but most have uneven distribution of acidic sites, resulting in insufficient selectivity for either monomethyl ether or dimethyl ether, particularly in secondary etherification reactions, leading to limited yields of the target product. In addition, some photocatalytic systems attempt to drive the reaction using light energy, but the catalysts are mostly of a single structure, resulting in low photogenerated carrier separation efficiency and a lack of precise control over product formation pathways, hindering the targeted preparation of monomethyl and dimethyl ethers and limiting their industrial application. Therefore, developing a highly selective, stable, and precisely controllable synthetic method for product types has become a current research hotspot and challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol.

[0005] To achieve the above objectives, the present invention provides a method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol, comprising the following steps:

[0006] S1. Raw material preparation: Under nitrogen protection, methanol and ethylene glycol are mixed, and molecular sieves and selective switching catalysts are added to obtain the reaction pretreatment liquid;

[0007] S2. Selective control of reaction pathways:

[0008] (a) Under visible light irradiation, the pre-reaction liquid was heated to 60°C and stirred for 6 hours under normal pressure. After cooling to room temperature, it was filtered, and excess methanol was removed by atmospheric distillation. Then, it was distilled under reduced pressure, and the fraction collected at a pressure of 10 kPa and a temperature of 65-70°C was obtained to yield ethylene glycol monomethyl ether.

[0009] (b) Under ultraviolet light irradiation, the pre-reaction liquid was heated to 90°C and pressure 0.25 MPa, and reacted for 10 h with stirring. After cooling to room temperature, the mixture was filtered, excess methanol was removed by atmospheric distillation, and then distilled under reduced pressure. The fraction collected at pressure 10 kPa and temperature 35-40°C was used to obtain ethylene glycol dimethyl ether.

[0010] The preparation process of the selective switching catalyst is as follows:

[0011] (1) Under nitrogen protection, zinc chloride and indium chloride were added to pyridine and stirred for 10-20 min. Then polyethylene glycol 600 and di-tert-butyl disulfide were added, and the mixture was placed in a self-pressurizing reactor. The temperature was raised to 180-220℃ and the reaction was continued for 16-24 h. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times each with ethanol and acetone. After drying, ZnInS nanorod powder was obtained. The chemical reaction equation is: Zn 2+ +2In 3+ +4S 2- →ZnIn2S4↓, In the reaction, zinc chloride and indium chloride dissolve in pyridine, and the amino group in pyridine reacts with Zn... 2+ In 3+ Coordination forms a metal-ligand complex, increasing the solubility of the metal ion in nonpolar solvents; upon heating to 215-225℃, di-tert-butyl disulfide decomposes to produce S. 2- With Zn in solution 2+ In 3+ A coordination reaction occurs in proportion to form ZnIn2S4 crystals; PEG600 contains hydrophilic hydroxyl groups, while the (100) crystal plane of ZnIn2S4 crystals exposes Zn due to atomic arrangement characteristics. 2+ In 3+ The ZnIn2S4 crystal has a high concentration of metal ions and a high surface polarity. The hydroxyl groups of PEG600 can bind to the metal ions or polar sites on the (100) crystal face through hydrogen bonding or weak coordination to form a stable adsorption layer that covers the active growth sites on the crystal face, thus hindering the deposition of atoms or ions in the radial direction (perpendicular to the axial direction). Other crystal faces of ZnIn2S4, such as the (001) face, have a lower surface polarity and a weaker interaction with PEG600. They are not adsorbed and covered, and can continue to accept atomic deposition and preferentially grow along the axial direction, ultimately promoting the formation of a one-dimensional nanorod structure.

[0012] (2) ZnInS nanorod powder was added to an ethanol / water mixed solvent and ultrasonically dispersed for 20-40 min. Then, 3-aminopropyltriethoxysilane was added and stirred at room temperature for 1-3 h. After filtration, the product was washed with deionized water and dried to obtain pretreated ZnInS nanorod powder. In the reaction, after the ZnInS nanorod powder was ultrasonically dispersed in an ethanol / water mixed solvent, the Zn exposed on the surface... 2+ In 3+The residual hydroxyl groups interact with 3-aminopropyltriethoxysilane (APTES): the amino group of APTES forms a coordinate bond with the metal ion through the lone pair electrons, and the amino group can also form hydrogen bonds with the surface hydroxyl groups, so that APTES is directionally adsorbed on the surface of ZnInS nanorod powder; the silicon-oxygen end of APTES undergoes preliminary hydrolysis in the ethanol / water system to generate active sites containing silanol groups, which provide an anchoring basis for subsequent reactions;

[0013] (3) Tetraethyl orthosilicate and nickel nitrate were added to ethanol, ammonia was added dropwise to adjust the pH of the system to 9.5, and after stirring for 10-20 min, pretreated ZnInS nanorod powder was added. The temperature was raised to 40-50℃ and the reaction was carried out for 10-14 h. The product was collected by centrifugation, washed and dried to obtain ZnInS / Ni composite. In the reaction, tetraethyl orthosilicate underwent hydrolysis in ethanol to generate silicic acid units. The silanol groups on the surface of the added pretreated ZnInS nanorods (from APTES hydrolysis) condensed with the silicic acid units generated by TEOS hydrolysis to form -Si-O-Si- bonds, gradually building a SiO2 shell. Ni in nickel nitrate 2+ Ni is uniformly doped into the shell by coordinating with silanol groups in the SiO2 network to form Si-O-Ni bonds. The difference in the ratio of tetraethyl orthosilicate to nickel nitrate determines the Ni content. 2+ The doping amount was adjusted, and the resulting product was reacted, washed, and dried to obtain a ZnInS / Ni composite with a core (ZnInS)-shell (SiO2-Ni) structure.

[0014] (4) The ZnInS / Ni composite was placed in a muffle furnace under a nitrogen atmosphere and heated to 200℃ at a rate of 5℃ / min, held for 2h, then heated to 550-650℃ and held for 1-2h, then cooled to 300℃, H2 / Ar mixed gas was introduced and held for 1h, and then cooled to room temperature to obtain the selective switching catalyst. In this process, the ZnInS / Ni composite was first heated to 200℃ and held to remove residual organic matter and impurities; the temperature was then increased to 550-650℃ to promote the condensation and crystallization of the SiO2 shell and enhance the density and structural stability of the shell; after cooling to 300℃, H2 / Ar mixed gas was introduced, and H2 partially condensed the Ni in the shell. 2+ Reduced to Ni with electron transport activity 0 or Ni δ+ (“δ+” indicates that nickel is in a partially oxidized state (non-integer valence state), that is, its oxidation state is between 0 and +2. This valence state originates from the fact that when Ni forms coordinate bonds with oxygen atoms in the surrounding SiO2 shell, the electron density shifts towards the more electronegative O, giving Ni a partial positive charge, but without completely losing 2 electrons. Ni) δ+Its importance lies in its combination of electron transport capability and weak Lewis acidity. It can act as an electron relay station to promote the separation of photogenerated carriers and assist in the activation of hydroxyl groups under high load, making it a key active species for achieving selective switching of catalysts and improving the photogenerated carrier separation efficiency of the catalyst. After cooling, it forms a selective switching catalyst that combines photocatalytic activity, Ni active sites (shell), and a stable structure.

[0015] Preferably, the molar ratio of methanol to ethylene glycol is 3-10:1.

[0016] Preferably, the ethylene glycol, molecular sieve, and selective switching catalyst are in a weight ratio of 1:0.06-0.1:0.03-0.07.

[0017] Preferably, the molar ratio of zinc chloride, indium chloride and di-tert-butyl disulfide in (1) is 1.2-1.6:2:3.84-4.32.

[0018] Preferably, in (1), zinc chloride, polyethylene glycol 600 and pyridine are in a weight ratio of 1:0.35-0.45:15-25.

[0019] Preferably, in (2), the ZnInS nanorod powder, ethanol / water mixed solvent and 3-aminopropyltriethoxysilane are mixed in a weight ratio of 1:80-100:0.06-0.14, and the ethanol / water mixed solution refers to the mixture of ethanol and water in a weight ratio of 4:1.

[0020] Preferably, the proportions of tetraethyl orthosilicate and nickel nitrate added in (3) are different in the catalysts used for different reaction pathways in the preparation of ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol, specifically:

[0021] When used in catalytic reaction pathway (a), the molar ratio of tetraethyl orthosilicate to nickel nitrate is 1:0.02-0.05;

[0022] When used in catalytic reaction pathway (b), the molar ratio of tetraethyl orthosilicate to nickel nitrate is 1:0.1-0.2;

[0023] Preferably, in (3), the weight ratio of tetraethyl orthosilicate, ethanol and pretreated ZnInS nanorod powder is 1:10-20:3-7.

[0024] Preferably, the H2 / Ar mixed gas in (4) refers to H2 and Ar mixed at a volume ratio of 1:19, with a flow rate of 80 ml / min.

[0025] Preferably, the selective switching catalytic mechanism of the selective switching catalyst is as follows:

[0026] In the preparation of ethylene glycol methyl ethers by etherification of methanol and ethylene glycol, the first step involves a nucleophilic substitution reaction between a hydroxyl group in the ethylene glycol molecule and methanol at an active site, generating ethylene glycol monomethyl ether (MEGME). This step has a low activation energy. The second step involves the further reaction of the remaining hydroxyl group in the MEGME molecule with methanol to generate ethylene glycol dimethyl ether (DEGME). Due to the electron-donating effect and steric hindrance of the methoxy group already present in MEGME, the nucleophilic activity of the remaining hydroxyl group is significantly reduced, resulting in a substantial increase in the activation energy of the second step reaction. This requires higher energy input and a stronger active site to drive the reaction.

[0027] In this invention, the catalyst used in the route for generating monomethyl ether is low-nickel supported (tetraethyl orthosilicate to nickel nitrate molar ratio 100:0.1-0.5), and the reaction is carried out under visible light irradiation and atmospheric pressure at 60°C. Under these conditions, the core layer of the ZnInS nanorod absorbs visible light energy, and valence band electrons transition to the conduction band, generating photogenerated holes (h0). + ) and electrons (e - Low-loaded Ni exists in the form of single atoms or small clusters, acting as an electron relay station to accelerate electron-hole separation. This allows photogenerated holes to be efficiently transferred to the catalyst surface to activate methanol molecules, generating low-activity ·CH3O radicals. Due to the low Ni loading, the number and strength of acidic sites introduced by Ni in the SiO2 shell are small, which cannot effectively provide protons or coordination to activate the remaining hydroxyl groups in MEGME. This makes it difficult for the hydroxyl groups of MEGME to be converted into the more easily attacked protonated form. At the same time, the low-nickel shell structure is relatively loose, and the interaction between MEGME and the catalyst surface is only weak hydrogen bonding or van der Waals forces. At a temperature of 60°C, thermal motion can overcome this weak adsorption, allowing MEGME to quickly detach from the active center region and significantly reducing the chance of contact with highly reactive species. In addition, the energy provided by visible light is low and insufficient to compensate for the high activation energy difference in the second step reaction, further inhibiting the secondary etherification of MEGME. Ultimately, the reaction mainly stops at the first step, with high selectivity for the formation of monomethyl ether.

[0028] In the pathway for dimethyl ether formation, a high-nickel-supported catalyst (tetraethyl orthosilicate to nickel nitrate molar ratio 100:2-5) was used. The reaction was conducted under UV irradiation, at 90°C and 0.25 MPa. The higher UV energy not only excited the ZnInS core layer to generate more photogenerated carriers but also significantly enhanced the oxidation capacity of photogenerated holes, resulting in a substantial increase in the activity of the ·CH3O radical generated from activated methanol. Simultaneously, the high nickel support led to the formation of more Ni-associated acidic sites in the SiO2 shell. These sites can activate the remaining hydroxyl groups in MEGME through coordination or proton transfer, reducing their ·CH3O content. The energy barrier of free radical attack is reduced. In addition, the temperature of 80-90℃ and the pressure of 0.25MPa provide additional thermodynamic driving force for the reaction, further reducing the activation energy barrier of the second step reaction. The excess methanol drives the equilibrium towards the formation of DEGME through the concentration effect. Under these conditions, the residence time of MEGME on the catalyst surface is prolonged, the shell structure is more compact due to the high nickel loading, the diffusion resistance is slightly increased, and it fully interacts with the highly active CH3O free radicals and acidic sites, finally completing the secondary etherification reaction and achieving highly selective formation of dimethyl ether.

[0029] In the reaction of ·CH3O radicals attacking ethylene glycol, the interaction between the removed hydroxyl group and the nickel site, along with the subsequent formation and removal of water, constitutes a key intermediate cycle for the continued reaction. When the ·CH3O radical attacks the CO bond between the terminal carbon of ethylene glycol and the hydroxyl oxygen, the CO bond undergoes heterolytic cleavage, causing the hydroxyl group to detach from the ethylene glycol molecule. This leaving group, due to its negative charge, readily reacts with the Ni on the catalyst surface. δ+ Weak bonds are formed through electrostatic attraction and coordination, and the molecules are temporarily adsorbed by nickel sites. Simultaneously, during the activation of methanol molecules at the catalyst's active site to generate ·CH3O radicals, the homolytic cleavage of OH bonds releases hydrogen radicals, which are then adsorbed by Ni. δ+ The adsorbed hydroxyl groups combine with ·H in the system through electron transfer at the nickel sites to form water molecules. At this point, the nickel sites return to their initial state and can continue to adsorb new hydroxyl leaving groups, forming a catalytic cycle. The generated water molecules, due to their high polarity, rapidly detach from the nickel sites and diffuse into the molecular sieve, thus achieving selective water removal. This process avoids water interference with Ni... δ The occupation of active sites disrupts the reaction equilibrium by removing byproducts, thus driving the continuous conversion of ethylene glycol.

[0030] The beneficial effects of this invention are:

[0031] 1. The method of this invention can achieve the directional preparation of ethylene glycol monomethyl ether and dimethyl ether, and has excellent product selectivity control capability. By designing selectively switching catalysts, a gradient distribution of Lewis acidic sites is constructed using the difference in nickel loading. Combined with the control of the activity of methoxy radicals by the wavelength of the light source, the activation energy requirements of the two-step etherification reaction are precisely matched. In this method, the low-nickel catalyst and visible light synergistically promote the first step of etherification, while the high-nickel catalyst and ultraviolet light synergistically drive the second step of etherification, thereby generating the target product as needed. This solves the problem that traditional methods are difficult to selectively control the ratio of monomethyl and dimethyl ethers.

[0032] 2. The catalyst used in this invention has high catalytic activity and excellent stability, which can efficiently promote the continuous reaction. The catalyst adopts a core-shell structure design, with ZnInS nanorods as the core and SiO2-Ni as the shell. This not only ensures the efficient separation of photogenerated charge carriers, but also protects the active components from corrosion through the SiO2 shell. At the same time, the molecular sieve adsorbs the water generated in the reaction in real time, preventing it from occupying the active sites and further maintaining the catalytic activity. It can still maintain high performance after multiple cycles of use, solving the problems of easy deactivation and rapid activity decay of traditional catalysts.

[0033] 3. The method in this invention has mild reaction conditions and is environmentally friendly, lowering the threshold for industrial application. This invention adopts a light-driven reaction, providing energy through visible or ultraviolet light depending on the target product. The reaction temperature is controlled at 60 or 90°C, and the pressure is atmospheric pressure or 0.25 MPa. Compared with the high temperature and high pressure conditions of traditional strong acid catalysis, it is easier to control and avoids equipment corrosion problems. In addition, no toxic or harmful raw materials are used in the catalyst preparation process, the product separation after the reaction is simple, the by-products are few and can be effectively adsorbed by molecular sieves, reducing the emission of waste. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of a method for preparing ethylene glycol methyl ether reagents using methanol and ethylene glycol etherification according to the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0036] Preparation Example 1: Specific synthesis method of selective switching catalyst, including the following steps:

[0037] (1) Under nitrogen protection, 16.36 g zinc chloride and 44.24 g indium chloride were added to 245.4 g pyridine and stirred for 10 min. Then, 5.73 g polyethylene glycol 600 and 56.18 g di-tert-butyl disulfide were added and placed in a self-pressurizing reactor. The temperature was raised to 180 °C and the reaction was continued for 16 h. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times each with ethanol and acetone. The ZnInS nanorod powder was obtained after drying.

[0038] (2) 20g of ZnInS nanorod powder was added to 1.6kg of ethanol / water mixed solvent (ethanol and water were mixed in a weight ratio of 4:1), ultrasonically dispersed for 20min, and then 1.2g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature for 1h, filtered, and the product was washed with deionized water and dried to obtain pretreated ZnInS nanorod powder.

[0039] (3) Add 6.67g of tetraethyl orthosilicate and 0.12g of nickel nitrate to 66.7g of ethanol, add ammonia dropwise, adjust the pH of the system to 9.5, stir for 10min, add 20g of pretreated ZnInS nanorod powder, heat to 40℃, react for 10h, collect the product by centrifugation, and obtain ZnInS / Ni composite after washing and drying;

[0040] (4) Place 20g of ZnInS / Ni composite in a muffle furnace. Under a nitrogen atmosphere, heat the mixture to 200℃ at a heating rate of 5℃ / min and hold for 2h. Then heat it to 550℃ and hold for 1h. Cool it down to 300℃ and introduce H2 / Ar mixed gas (H2 and Ar are mixed at a volume ratio of 1:19 and the flow rate is 80ml / min). Hold the mixture for 1h and cool it to room temperature to obtain the selective switching catalyst.

[0041] Preparation Example 2: Specific synthesis method of selective switching catalyst, including the following steps:

[0042] (1) Under nitrogen protection, 19.08 g zinc chloride and 44.24 g indium chloride were added to 381.64 g pyridine and stirred for 15 min. Then, 7.63 g polyethylene glycol 600 and 59.69 g di-tert-butyl disulfide were added and placed in a self-pressurizing reactor. The temperature was raised to 200 °C and the reaction was continued for 20 h. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times each with ethanol and acetone. The ZnInS nanorod powder was obtained after drying.

[0043] (2) 20g of ZnInS nanorod powder was added to 1.8kg of ethanol / water mixed solvent (ethanol and water were mixed in a weight ratio of 4:1), ultrasonically dispersed for 30min, and then 2g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature for 2h, filtered, and the product was washed with deionized water and dried to obtain pretreated ZnInS nanorod powder.

[0044] (3) Add 4g of tetraethyl orthosilicate and 0.12g of nickel nitrate to 60g of ethanol, add ammonia dropwise, adjust the pH of the system to 9.5, stir for 15min, add 20g of pretreated ZnInS nanorod powder, heat to 45℃, react for 12h, collect the product by centrifugation, and obtain ZnInS / Ni composite after washing and drying.

[0045] (4) Place 20g of ZnInS / Ni composite in a muffle furnace. Under a nitrogen atmosphere, heat the mixture to 200℃ at a heating rate of 5℃ / min and hold for 2h. Then heat it to 600℃ and hold for 1.5h. Cool it down to 300℃ and introduce H2 / Ar mixed gas (H2 and Ar are mixed at a volume ratio of 1:19 and the flow rate is 80ml / min). Hold the mixture for 1h and cool it to room temperature to obtain the selective switching catalyst.

[0046] Preparation Example 3: Specific synthesis method of selective switching catalyst, including the following steps:

[0047] (1) Under nitrogen protection, 21.81 g zinc chloride and 44.24 g indium chloride were added to 545.2 g pyridine and stirred for 20 min. Then, 9.81 g polyethylene glycol 600 and 63.20 g di-tert-butyl disulfide were added and placed in a self-pressurizing reactor. The temperature was raised to 220 °C and the reaction was continued for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times each with ethanol and acetone. The ZnInS nanorod powder was obtained after drying.

[0048] (2) 20g of ZnInS nanorod powder was added to 2kg of ethanol / water mixed solvent (ethanol and water were mixed in a weight ratio of 4:1), ultrasonically dispersed for 40min, and then 2.8g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature for 3h, filtered, and the product was washed with deionized water and dried to obtain pretreated ZnInS nanorod powder.

[0049] (3) Add 2.86g of tetraethyl orthosilicate and 0.13g of nickel nitrate to 57.2g of ethanol, add ammonia dropwise, adjust the pH of the system to 9.5, stir for 20min, add 20g of pretreated ZnInS nanorod powder, heat to 50℃, react for 14h, collect the product by centrifugation, and obtain ZnInS / Ni composite after washing and drying;

[0050] (4) The ZnInS / Ni composite was placed in a muffle furnace and heated to 200°C at a heating rate of 5°C / min under a nitrogen atmosphere. The temperature was held for 2 hours, then heated to 650°C and held for 2 hours. The temperature was then lowered to 300°C, and a H2 / Ar mixed gas (H2 and Ar were mixed at a volume ratio of 1:19 and the flow rate was 80 ml / min) was introduced. The temperature was held for 1 hour and then cooled to room temperature to obtain the selective switching catalyst.

[0051] Preparation Example 4: The difference between Preparation Example 5 and Preparation Example 1 is that the amount of tetraethyl orthosilicate, nickel nitrate, ethanol and pretreated ZnInS nanorod powder added in step (3) is 6.67g:0.58g:66.7g:20g.

[0052] Preparation Example 5: The difference between Preparation Example 5 and Preparation Example 2 is that the amount of tetraethyl orthosilicate, nickel nitrate, ethanol and pretreated ZnInS nanorod powder added in step (3) is 4g:0.53g:60g:20g.

[0053] Preparation Example 6: The difference between Preparation Example 6 and Preparation Example 3 is that the amount of tetraethyl orthosilicate, nickel nitrate, ethanol and pretreated ZnInS nanorod powder added in step (3) is 2.86g:0.50g:57.2g:20g.

[0054] Comparative preparation example 1: The difference between comparative preparation example 1 and preparation example 2 is that nickel nitrate is not added in step (3).

[0055] Comparative preparation example 2: The difference between comparative preparation example 2 and preparation example 5 is that the amount of nickel nitrate added in step (3) is 1.06g.

[0056] Example 1: A method for preparing ethylene glycol monomethyl ether using methanol and ethylene glycol etherification:

[0057] S1. Raw material preparation: Under nitrogen protection, 154.86g of methanol and 100g of ethylene glycol were mixed, and 6g of molecular sieve and 3g of selective switching catalyst prepared according to Preparation Example 1 were added to obtain the reaction pretreatment liquid;

[0058] S2. Selective control of reaction pathways:

[0059] Under visible light irradiation, the pre-reaction liquid was heated to 60°C and stirred for 6 hours under normal pressure. After cooling to room temperature, the mixture was filtered, and excess methanol was removed by atmospheric distillation. Then, the mixture was distilled under reduced pressure, and the fraction collected at a pressure of 10 kPa and a temperature of 65-70°C was used to obtain ethylene glycol monomethyl ether.

[0060] Example 2: A method for preparing ethylene glycol monomethyl ether using methanol and ethylene glycol etherification:

[0061] S1. Raw material preparation: Under nitrogen protection, 335.52g of methanol and 100g of ethylene glycol were mixed, and 8g of molecular sieve and 5g of selective switching catalyst prepared according to Preparation Example 2 were added to obtain the reaction pretreatment liquid;

[0062] S2. Selective control of reaction pathways:

[0063] Under visible light irradiation, the pre-reaction liquid was heated to 60°C and stirred for 6 hours under normal pressure. After cooling to room temperature, the mixture was filtered, and excess methanol was removed by atmospheric distillation. Then, the mixture was distilled under reduced pressure, and the fraction collected at a pressure of 10 kPa and a temperature of 65-70°C was used to obtain ethylene glycol monomethyl ether.

[0064] Example 3: A method for preparing ethylene glycol monomethyl ether using methanol and ethylene glycol etherification:

[0065] S1. Raw material preparation: Under nitrogen protection, 516.19g of methanol and 100g of ethylene glycol were mixed, and 10g of molecular sieve and 7g of selective switching catalyst prepared according to Preparation Example 3 were added to obtain the reaction pretreatment liquid;

[0066] S2. Selective control of reaction pathways:

[0067] Under visible light irradiation, the pre-reaction liquid was heated to 60°C and stirred for 6 hours under normal pressure. After cooling to room temperature, the mixture was filtered, and excess methanol was removed by atmospheric distillation. Then, the mixture was distilled under reduced pressure, and the fraction collected at a pressure of 10 kPa and a temperature of 65-70°C was used to obtain ethylene glycol monomethyl ether.

[0068] Example 4: A method for preparing ethylene glycol dimethyl ether using methanol and ethylene glycol etherification:

[0069] S1. Raw material preparation: Under nitrogen protection, 154.86g of methanol and 100g of ethylene glycol were mixed, and 6g of molecular sieve and 3g of selective switching catalyst prepared according to Preparation Example 4 were added to obtain the reaction pretreatment liquid;

[0070] S2. Selective control of reaction pathways:

[0071] Under ultraviolet light irradiation, the pre-reaction liquid was heated to 90℃ and pressure 0.25MPa, and reacted for 10h with stirring. After cooling to room temperature, it was filtered, excess methanol was removed by atmospheric distillation, and then distilled under reduced pressure. The fraction collected at pressure 10KPa and temperature 35-40℃ was used to obtain ethylene glycol dimethyl ether.

[0072] Example 5: A method for preparing ethylene glycol dimethyl ether using methanol and ethylene glycol etherification:

[0073] S1. Raw material preparation: Mix 335.52g of methanol and 100g of ethylene glycol, add 8g of molecular sieve and 5g of selective switching catalyst prepared according to preparation example 5 to obtain the reaction pretreatment liquid;

[0074] S2. Selective control of reaction pathways:

[0075] Under ultraviolet light irradiation, the pre-reaction liquid was heated to 90℃ and pressure 0.25MPa, and reacted for 10h with stirring. After cooling to room temperature, it was filtered, excess methanol was removed by atmospheric distillation, and then distilled under reduced pressure. The fraction collected at pressure 10KPa and temperature 35-40℃ was used to obtain ethylene glycol dimethyl ether.

[0076] Example 6: A method for preparing ethylene glycol dimethyl ether using methanol and ethylene glycol etherification:

[0077] S1. Raw material preparation: Under nitrogen protection, 516.19g of methanol and 100g of ethylene glycol were mixed, and 10g of molecular sieve and 7g of selective switching catalyst prepared according to Preparation Example 6 were added to obtain the reaction pretreatment liquid;

[0078] S2. Selective control of reaction pathways:

[0079] Under ultraviolet light irradiation, the pre-reaction liquid was heated to 90℃ and pressure 0.25MPa, and reacted for 10h with stirring. After cooling to room temperature, it was filtered, excess methanol was removed by atmospheric distillation, and then distilled under reduced pressure. The fraction collected at pressure 10KPa and temperature 35-40℃ was used to obtain ethylene glycol dimethyl ether.

[0080] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the selective catalyst prepared in Example 2 was replaced with the selective switching catalyst prepared in Example 5.

[0081] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the selective switching catalyst prepared in Example 2 was replaced with the selective catalyst prepared in Example 2.

[0082] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that visible light irradiation in step S2 is replaced with ultraviolet light irradiation.

[0083] Comparative Example 4: The difference between Comparative Example 4 and Example 5 is that the selective catalyst prepared in Example 5 was replaced with the selective switching catalyst prepared in Example 2.

[0084] Comparative Example 5: The difference between Comparative Example 5 and Example 5 is that the selective catalyst prepared in Example 5 was replaced with the selective switching catalyst prepared in Comparative Preparation Example 2.

[0085] Comparative Example 6: The difference between Comparative Example 6 and Example 5 is that the ultraviolet light irradiation in step S2 is replaced with visible light irradiation.

[0086] Performance testing:

[0087] 1. Using a gas chromatograph, the content of the target product in the crude products obtained after removing methanol by atmospheric distillation in Examples 1-6 and Comparative Examples 1-6 was analyzed by internal standard method. The target product in Examples 1-3 and Comparative Examples 1-3 was ethylene glycol monomethyl ether, and the target product in Examples 4-6 and Comparative Examples 4-6 was ethylene glycol dimethyl ether. The experimental results are shown in Table 1.

[0088] 2. Using gas chromatography and the internal standard method, the conversion rate of Examples 1-6 and Comparative Examples 1-6 was calculated by analyzing the changes in the peak area of ​​ethylene glycol before and after the reaction. The experimental results are shown in Table 1.

[0089] 3. The catalysts used in Examples 1-6 and Comparative Examples 2 and 5 were selected and reused 10 times according to the corresponding experimental methods (filtered, washed with ethanol, and dried at 60°C after each reaction); the content of ethylene glycol monomethyl ether / ethylene glycol dimethyl ether and the conversion rate of ethylene glycol were analyzed and calculated after each cycle. The retention rate of ethylene glycol monomethyl ether / ethylene glycol dimethyl ether and the conversion retention rate of ethylene glycol in the 10th cycle were calculated. The experimental results are shown in Table 1.

[0090] Table 1 Performance Test Results

[0091] Target product content / % Ethylene glycol conversion rate / % Content retention rate / % Ethylene glycol conversion retention rate / % Example 1 97.5 96.2 96.5 94.8 Example 2 98.1 96.3 96.8 95.2 Example 3 97.1 95.4 96.2 94.5 Example 4 98.3 97.8 95.8 94.9 Example 5 98.6 97.7 96.1 95.5 Example 6 98.4 98.1 96.0 95.1 Comparative Example 1 76.2 81.5 - - Comparative Example 2 63.8 68.9 55.3 65.7 Comparative Example 3 65.4 79.6 - - Comparative Example 4 70.3 76.8 - - Comparative Example 5 81.7 83.2 78.6 82.0 Comparative Example 6 52.6 58.3 - -

[0092] Performance Analysis:

[0093] As can be seen from the experimental data in Table 1, the excellent performance of the examples stems from the precise structural design of the catalyst and the synergistic regulation of the reaction conditions. The catalyst uses ZnInS nanorods as the core, and forms a one-dimensional structure through selective adsorption of PEG600, increasing the specific surface area and exposing more photoactive sites. APTES pretreatment introduces silanol groups onto the ZnInS surface, which are firmly bonded to the SiO2 shell through -Si-O-Si- bonds, preventing core-shell separation and providing a uniform anchoring basis for nickel sites. The nickel is represented by Ni. δ+ The (partially oxidized) form is dispersed in the shell, retaining the electron transport capability of the metallic state. Furthermore, due to the weak Lewis acidity of the partially positively charged state, it can act as an electron relay station to accelerate the separation of photogenerated carriers, reduce recombination probability, and improve methanol activation efficiency. This core-shell structure not only protects ZnInS from the corrosive effects of the reaction environment but also, through the confinement effect of SiO2, allows active species (·CH3O radicals, Ni...) to... δ+ The molecular sieve concentrates at the reaction interface, increasing the collision probability with the substrate, thereby improving conversion while suppressing side reactions and significantly enhancing the selectivity of the target product. Furthermore, the real-time water absorption of the molecular sieve continuously removes reaction byproduct water, preventing it from occupying Ni. δ+ The active sites or the inhibition of methanol activation further promote the forward reaction, jointly ensuring the high performance of the embodiments.

[0094] Examples 1-3 were able to produce ethylene glycol monomethyl ether on demand, the key being the synergistic effect of the low-nickel supported catalyst and visible light irradiation, which matched the requirements of the first-step etherification reaction. Under low-nickel loading, the Ni in the SiO2 shell... δ+ The sites are sparse and dispersed, and their Lewis acidity is weak. They can only temporarily adsorb the hydroxyl groups removed by ethylene glycol through weak coordination, avoiding interference from free hydroxyl groups, but are insufficient to activate the remaining hydroxyl groups in monomethyl ether (because the methoxy group of monomethyl ether has an electron-donating effect and steric hindrance, activation requires a stronger acidic site). At the same time, the visible light energy is low, and the photogenerated hole oxidation ability is limited. The generated ·CH3O free radicals have moderate reactivity, which can only overcome the low activation energy barrier of the first step of etherification and undergo nucleophilic substitution with the terminal hydroxyl group of ethylene glycol. The interaction between monomethyl ether and the loose shell is weak, and it can quickly detach from the active region at the reaction temperature, reducing secondary contact with ·CH3O free radicals. This synergistic mechanism of "weak acidic sites + low-reactivity free radicals + rapid desorption" effectively inhibits secondary etherification, keeping the reaction mainly at the monomethyl ether stage and achieving high selectivity.

[0095] Examples 4-6 were able to directionally generate ethylene glycol dimethyl ether because the reaction environment created by the high-nickel supported catalyst and ultraviolet irradiation precisely matched the high activation energy requirement of the second-step etherification. The high nickel loading increased the Ni content in the SiO2 shell. δ+ The densely packed sites enhance the Lewis acidity of the ZnInS core, activating the remaining hydroxyl groups in monomethyl ether through coordination or proton transfer, thus lowering the energy barrier against attack by ·CH3O radicals. Simultaneously, the higher energy of ultraviolet light not only excites the ZnInS core to generate more photogenerated carriers but also significantly enhances the oxidation capacity of photogenerated holes, greatly increasing the activity of ·CH3O radicals, sufficient to overcome the steric hindrance and electron repulsion of monomethyl ether. Furthermore, the higher reaction temperature and pressure provide additional thermodynamic driving forces, which, combined with the concentration effect of excess methanol, further push the equilibrium towards secondary etherification. The dense shell structure prolongs the residence time of monomethyl ether in the active region, allowing it to fully interact with the highly active ·CH3O radicals and acidic sites, ultimately completing the second-step etherification reaction and achieving highly selective formation of dimethyl ether.

[0096] The catalysts used in Examples 1-6 exhibited significantly better cycle stability than those in Comparative Examples 2 and 5. This difference stemmed primarily from the differences in catalyst structure design and active site regulation. The catalysts used in Examples 1-6 employed a core-shell structure (ZnInS nanorods as the core and SiO2-Ni as the shell). The ZnInS core was directionally grown using PEG600 to form one-dimensional nanorods, increasing the exposure of photoactive sites. APTES pretreatment introduced silanol groups onto the ZnInS surface, which then firmly bonded to the SiO2 shell through -Si-O-Si- bonds, preventing core-shell separation. Simultaneously, the Ni... δ+ (Partial oxidation state) provides uniform anchoring points, Niδ+ Dispersed within the SiO2 shell by Si-O-Ni bonds, the molecular sieve retains its electron transport capability and participates in the catalytic cycle due to its weak Lewis acidity. Furthermore, it is less prone to aggregation or detachment. During the reaction, the molecular sieve adsorbs the generated water in real time, preventing it from occupying Ni. δ+ The active sites maintain the effectiveness of the catalytic center; the light source (visible / ultraviolet light) and nickel loading (low / high) are precisely matched to meet the activation energy requirements of mono / dimethyl ether reactions, reducing the erosion of the catalyst by side reactions. Therefore, the active sites remain intact during cycling, resulting in excellent stability.

[0097] The catalyst in Comparative Example 2 did not contain nickel nitrate and lacked Ni. δ+ The active sites exhibit extremely low photogenerated carrier separation efficiency, weak methanol activation ability, and a high tendency to generate numerous byproducts (such as ethylene glycol self-polymerization products) during the reaction. These byproducts can cover the ZnInS core surface, blocking the active sites, and there is no Ni... δ+ The anchoring and electron transfer functions of the core-shell structure make it susceptible to damage from byproduct erosion, and its activity rapidly declines during cycling.

[0098] The catalyst in Comparative Example 5 had excessive Ni loading, leading to an increase in Ni content in the SiO2 shell. δ+ Aggregation forms large particles, which disrupts the compactness of the shell. Aggregated Ni is easily detached from the shell and lost. At the same time, excessive Ni enhances the adsorption capacity for byproducts, accelerates the poisoning of active sites, and weakens the core-shell binding force due to Ni aggregation. This leads to decreased structural stability during cycling and continuous decline in activity.

[0099] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol, characterized in that, Includes the following steps: S1. Raw material preparation: Under nitrogen protection, methanol and ethylene glycol are mixed, and molecular sieves and selective switching catalysts are added to obtain the reaction pretreatment liquid; S2. Selective control of reaction pathways: (a) Under visible light irradiation, the pre-reaction liquid was heated to 60°C and stirred for 6 hours under normal pressure. After cooling to room temperature, it was filtered, and excess methanol was removed by atmospheric distillation. Then, it was distilled under reduced pressure, and the fraction collected at a pressure of 10 kPa and a temperature of 65-70°C was obtained to yield ethylene glycol monomethyl ether. (b) Under ultraviolet light irradiation, the pre-reaction liquid was heated to 90°C and pressure 0.25 MPa, and reacted for 10 h with stirring. After cooling to room temperature, the mixture was filtered, excess methanol was removed by atmospheric distillation, and then distilled under reduced pressure. The fraction collected at pressure 10 kPa and temperature 35-40°C was used to obtain ethylene glycol dimethyl ether. The preparation process of the selective switching catalyst is as follows: (1) Under nitrogen protection, zinc chloride and indium chloride were added to pyridine and stirred for 10-20 min. Then polyethylene glycol 600 and di-tert-butyl disulfide were added and placed in a self-pressurizing reactor. The temperature was raised to 180-220℃ and the reaction was continued for 16-24 h. The mixture was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with acetone, and dried to obtain ZnInS nanorod powder. (2) Add ZnInS nanorod powder to an ethanol / water mixed solvent, ultrasonically disperse for 20-40 min, then add 3-aminopropyltriethoxysilane, stir at room temperature for 1-3 h, filter, wash the product with deionized water and dry to obtain pretreated ZnInS nanorod powder. (3) Add tetraethyl orthosilicate and nickel nitrate to ethanol, add ammonia dropwise, adjust the pH of the system to 9.5, stir for 10-20 min, add pretreated ZnInS nanorod powder, heat to 40-50℃, react for 10-14 h, collect the product by centrifugation, and obtain ZnInS / Ni composite after washing and drying. (4) The ZnInS / Ni composite was placed in a muffle furnace and heated to 200°C at a heating rate of 5°C / min under a nitrogen atmosphere. The temperature was held for 2 hours, then heated to 550-650°C and held for 1-2 hours. The temperature was then lowered to 300°C, and H2 / Ar mixed gas was introduced and held for 1 hour. After cooling to room temperature, the selective switching catalyst was obtained.

2. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, The molar ratio of methanol to ethylene glycol is 3-10:

1.

3. The method for preparing ethylene glycol methyl ether reagents using methanol and ethylene glycol etherification according to claim 1, characterized in that, The ethylene glycol, molecular sieve, and selective switching catalyst are present in a weight ratio of 1:0.06-0.1:0.03-0.

07.

4. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, In (1), the molar ratio of zinc chloride, indium chloride and di-tert-butyl disulfide is 1.2-1.6:2:3.84-4.

32.

5. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, In (1), zinc chloride, polyethylene glycol 600 and pyridine are in a weight ratio of 1:0.35-0.45:15-25.

6. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, In (2), the ZnInS nanorod powder, ethanol / water mixed solvent and 3-aminopropyltriethoxysilane are mixed in a weight ratio of 1:80-100:0.06-0.

14. The ethanol / water mixed solution refers to the mixture of ethanol and water in a weight ratio of 4:

1.

7. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, In (3), the proportions of tetraethyl orthosilicate and nickel nitrate added to the catalyst vary depending on the reaction pathway used to prepare ethylene glycol methyl ether reagents via methanol and ethylene glycol etherification. Specifically: When used in catalytic reaction pathway (a), the molar ratio of tetraethyl orthosilicate to nickel nitrate is 1:0.02-0.05; When used in catalytic reaction pathway (b), the molar ratio of tetraethyl orthosilicate to nickel nitrate is 1:0.1-0.

2.

8. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, In (3), the weight ratio of tetraethyl orthosilicate, ethanol and pretreated ZnInS nanorod powder is 1:10-20:3-7.

9. The method for preparing ethylene glycol methyl ether reagents by etherification of methanol and ethylene glycol according to claim 1, characterized in that, The H2 / Ar mixed gas mentioned in (4) refers to the mixture of H2 and Ar at a volume ratio of 1:19, with a flow rate of 80 ml / min.

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