A kind of immobilized ionic liquid catalyst and its preparation method and use

Abstract

The present invention provides a kind of immobilized ionic liquid catalyst, it comprises Lewis acid composite ionic liquid and solid base, wherein, the Lewis acid composite ionic liquid is a complex of imidazole ionic liquid and Lewis acid, the imidazole structure of the imidazole ionic liquid is N-alkyl imidazole, and the solid base is used as a carrier of the Lewis acid composite ionic liquid. The immobilized ionic liquid catalyst of the present invention can catalyze alkylene oxide to prepare dimethyl carbonate in one step. Moreover, the immobilized ionic liquid catalyst of the present invention has excellent catalytic activity, can realize the preparation of dimethyl carbonate under mild conditions, and the separation of product and catalyst is simple, reducing equipment investment cost.

Description

Technical Field

[0001] The invention belongs to the field of organic chemical industry, and specifically relates to an immobilized ionic liquid catalyst and a preparation method and application thereof. Background Art

[0002] Dimethyl carbonate (DMC) is a green and environmentally friendly chemical raw material with low toxicity and no pollution. It is widely used in lithium-ion battery electrolytes, organic synthesis intermediates and synthetic polycarbonate. At the same time, dimethyl carbonate can also be used as a gasoline additive and organic solvent, and has a wide range of application prospects. The dimethyl carbonate molecule contains a wealth of functional groups, among which the carbonyl and methyl groups can replace toxic raw materials for a variety of chemical reactions.

[0003] At present, the methods used to prepare dimethyl carbonate mainly include phosgene method, methanol oxidation carbonylation method, urea alcoholysis method and transesterification method. Among them, the transesterification method has become the mainstream method for industrial production of dimethyl carbonate due to its advantages such as mild reaction conditions, high yield, and green and pollution-free reaction process. The industrial transesterification method for preparing dimethyl carbonate is carried out in two steps. First, propylene oxide (or ethylene oxide) and carbon dioxide undergo a cycloaddition reaction under high temperature and high pressure conditions to generate propylene carbonate (or vinyl carbonate). After separation, high-purity propylene carbonate (or vinyl carbonate) is obtained, and then it undergoes an ester exchange reaction with methanol, and then distillation and separation is performed to finally obtain dimethyl carbonate.

[0004] Common homogeneous catalysts in cycloaddition reactions include metal complexes, metal halides, non-metallic organic catalysts, and ionic liquids. Common heterogeneous catalysts are resins that have both Lewis acid and base active sites, metal oxides, and homogeneous solid-supported catalysts. The catalysts for transesterification reactions are traditional homogeneous solid bases and heterogeneous solid bases. Homogeneous catalysts have good solubility in the reaction raw materials and do not have mass transfer problems, so the catalytic activity and product yield are relatively high, but the separation of the catalyst and the product is more difficult, resulting in poor catalyst reusability and high equipment investment. Heterogeneous catalysts do not have the problem of separating the product and the catalyst, but the mass transfer is limited, resulting in lower catalytic activity than homogeneous catalysts.

[0005] Ionic liquids have the advantages of being non-volatile, having good thermochemical stability, having a wide liquid temperature range, and having unique designability. They are used as clean solvents and new catalytic systems to catalyze a variety of reactions. Ionic liquid catalysts are widely used in the cycloaddition reaction of propylene oxide (ethylene oxide) and carbon dioxide. Their main advantage is that carbon dioxide can be well dissolved in ionic liquids, so ionic liquids are considered to be a very effective catalyst for fixing carbon dioxide and catalyzing carbon dioxide reactions. Patent CN101773858B prepared an imidazole composite ionic liquid catalyst to prepare propylene carbonate using propylene oxide and carbon dioxide as raw materials. The catalyst has high activity, fast reaction speed, mild reaction conditions, and low energy consumption, but its activity in catalyzing the one-step generation of dimethyl carbonate from alkylene oxide is low. Ionic liquid catalysts are also used in the reaction of propylene carbonate and methanol to prepare dimethyl carbonate. Patent application CN116178626A uses imidazole ionic liquid as a cationic skeleton, doped with nitrogen-containing basic group monomers, and subjected to free radical polymerization to prepare an alkaline polyionic liquid catalyst. The nitrogen doping in the catalyst increases the alkaline active sites, thereby exhibiting good catalytic performance in the reaction of catalyzing propylene carbonate and methanol to synthesize dimethyl carbonate. The catalyst can be separated by centrifugation and regenerated by vacuum freeze drying. However, the catalyst cannot catalyze the generation of dimethyl carbonate from alkylene oxide in one step, and the equipment investment in production is still relatively high.

[0006] Although the two-step method for preparing dimethyl carbonate from alkylene oxide is relatively mature in industrial applications, it has problems such as complex process, more equipment, and large amount of catalyst, resulting in high costs such as equipment investment and energy consumption. The ionic liquid catalysts involved in the prior art do not have dual activity, that is, they do not have dual activity of catalyzing cycloaddition and transesterification reactions, and cannot catalyze alkylene oxide to generate dimethyl carbonate in one step. Therefore, it is necessary to develop a catalyst with dual activity to prepare dimethyl carbonate by a one-step method, thereby simplifying the production process and reducing the complexity of the equipment. Summary of the invention

[0007] In view of the above problems, one of the purposes of the present invention is to provide an immobilized ionic liquid catalyst. The immobilized ionic liquid catalyst of the present invention can catalyze the preparation of dimethyl carbonate from alkylene oxide in one step. Moreover, the immobilized ionic liquid catalyst of the present invention has excellent catalytic activity, can realize the preparation of dimethyl carbonate under mild conditions, and the separation of the product and the catalyst is simple, thereby reducing the equipment investment cost.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] A solid-supported ionic liquid catalyst comprises a Lewis acid composite ionic liquid and a solid base, wherein the Lewis acid composite ionic liquid is a complex of an imidazole ionic liquid and a Lewis acid, the imidazole structure of the imidazole ionic liquid is N-alkyl imidazole, and the solid base serves as a carrier of the Lewis acid composite ionic liquid.

[0010] According to the catalyst of the present invention, the imidazolium ionic liquid is a halogenated alkyl imidazolium ionic liquid, for example, 1-butyl-3-methylimidazole bromide; the Lewis acid is a metal halide, preferably one of zinc chloride, zinc bromide or zinc iodide.

[0011] According to the catalyst of the present invention, the solid base is a dendritic fibrous silica loaded with an alkali metal, and the alkali metal is one of lithium, sodium, potassium and cesium.

[0012] According to the catalyst of the present invention, the mass ratio of the Lewis acid composite ionic liquid to the solid base is (2-10):1, preferably (2-7):1.

[0013] The second object of the present invention is to provide a method for preparing an immobilized ionic liquid catalyst, and the technical scheme is as follows:

[0014] A method for preparing an immobilized ionic liquid catalyst comprises the following steps:

[0015] Step 1: N-alkyl imidazole and halogenated alkane are stirred and mixed, reacted under heating conditions, and washed, rotary evaporated, and dried after the reaction is completed to prepare a halogenated alkyl imidazole ionic liquid; the halogenated alkyl imidazole ionic liquid and Lewis acid are stirred and mixed, reacted under heating conditions, and dried after the reaction is completed to prepare a Lewis acid composite ionic liquid;

[0016] Step 2: preparing dendritic fibrous silica by a hydrothermal method; using alkali metal acetate as a precursor, loading the alkali metal in the alkali metal acetate onto the dendritic fibrous silica, and obtaining a solid base after calcination;

[0017] Step 3: The Lewis acid composite ionic liquid reacts with a solid base to obtain a solid-supported ionic liquid catalyst.

[0018] According to the method for preparing an immobilized ionic liquid catalyst of the present invention, in step 1, in the step of reacting N-alkylimidazole with halogenated alkane,

[0019] N-alkylimidazole is N-methylimidazole, N-ethylimidazole, N-propylimidazole, or N-butylimidazole, preferably N-methylimidazole;

[0020] The halogenated alkane is butyl bromide, butyl chloride, or butyl iodide, preferably butyl bromide;

[0021] The mass ratio of N-alkylimidazole to halogenated alkane is 1:(1~4);

[0022] The reaction temperature is 70-120°C, preferably 75-90°C, and the reaction time is 20-30h.

[0023] According to the method for preparing an immobilized ionic liquid catalyst of the present invention, in step 1, in the step of reacting a halogenated alkyl imidazolium ionic liquid with a Lewis acid,

[0024] The Lewis acid is a metal halide, preferably one of zinc chloride, zinc bromide or zinc iodide, more preferably zinc bromide;

[0025] The mass ratio of the halogenated alkyl imidazolium ionic liquid to the Lewis acid is (5-20):1, preferably (8-15):1;

[0026] The reaction temperature is 90-120°C, preferably 95-110°C, and the reaction time is 20-30h.

[0027] According to the method for preparing an immobilized ionic liquid catalyst of the present invention, in step 2, alkylammonium bromide and urea are dissolved in water, and then tetraalkoxysilane is added, and the resulting mixed solution is subjected to a hydrothermal reaction. After the reaction is completed, the reaction solution is calcined to obtain dendritic fibrous silica;

[0028] The reaction temperature is 70-90°C and the reaction time is 20-30h;

[0029] The calcination temperature is 500-600°C and the calcination time is 5-8h;

[0030] The mass volume ratio (g / mL) of alkylammonium bromide to tetraalkoxysilane is 1:(1-10), preferably 1:(1-6);

[0031] The mass volume ratio (g / mL) of urea to tetraalkoxysilane is 1:(1-10), preferably 1:(1-6);

[0032] The alkylammonium bromide is selected from one or more of hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide;

[0033] The tetraalkoxysilane is selected from one or more of tetraethoxysilane, tetramethoxysilane and tetrapropoxysilane.

[0034] According to the method for preparing a supported ionic liquid catalyst of the present invention, in step 2, an alkali metal acetate is dissolved in water, added dropwise to the dendritic fibrous silica, and stirred to react so as to load the alkali metal in the alkali metal acetate onto the dendritic fibrous silica. After the reaction is completed, the reaction solution is allowed to stand and then calcined to obtain a solid base;

[0035] The reaction temperature is 15-35°C, preferably 20-30°C, and the reaction time is 10-15h;

[0036] The calcination temperature is 400-500°C and the calcination time is 1-3h;

[0037] The alkali metal acetate is selected from potassium acetate, lithium acetate, sodium acetate, or cesium acetate;

[0038] The mass ratio of dendritic fibrous silica to alkali metal acetate is (10-40):1, preferably (12-30):1.

[0039] According to the method for preparing a solid-supported ionic liquid catalyst of the present invention, wherein, in step 3, the solid base is first dispersed in a solvent, the mass volume ratio (g / mL) of the solid base to the solvent is 1:(50-100), and the solvent is selected from one or more of toluene, ethylbenzene, and benzene, preferably toluene;

[0040] Adding the Lewis acid composite ion liquid dropwise to react, preferably, adding the Lewis acid composite ion liquid dropwise to react under nitrogen protection;

[0041] The mass ratio of the Lewis acid composite ionic liquid to the solid base is (2-10):1, preferably (2-7):1;

[0042] The reaction temperature is 90~130℃, and the reaction time is 10~20h;

[0043] After the reaction is completed, the solid-supported ionic liquid catalyst is obtained by extraction with a solvent (eg, dichloromethane) and drying.

[0044] The third object of the present invention is to provide a method for preparing dimethyl carbonate, and the technical scheme is as follows:

[0045] A method for preparing dimethyl carbonate comprises the following steps:

[0046] The immobilized ionic liquid catalyst, methanol and alkylene oxide are added into a high-pressure reactor in a certain proportion, and carbon dioxide is introduced to react. After the reaction is completed, the immobilized ionic liquid catalyst is recovered by centrifugation, and dimethyl carbonate is obtained by distillation separation.

[0047] According to the method for preparing dimethyl carbonate of the present invention, wherein,

[0048] The amount of the immobilized ionic liquid catalyst added is 0.1-5wt%, preferably 0.1-3wt% of the alkylene oxide;

[0049] The mass ratio of methanol to alkylene oxide is 2:1-5:1;

[0050] Introduce carbon dioxide to control the reaction pressure at 2-4MPa;

[0051] The reaction temperature is 80-120°C, preferably 100-120°C;

[0052] The reaction time is 1h-5h, preferably 3-5h;

[0053] The alkylene oxide is ethylene oxide or propylene oxide.

[0054] A fourth object of the present invention is to provide a method for preparing dimethyl carbonate in one step by catalyzing alkylene oxide using an immobilized ionic liquid catalyst.

[0055] Beneficial Effects

[0056] 1) The loading of alkali metal on the solid base carrier of the immobilized ionic liquid catalyst prepared by the present invention can effectively regulate the alkalinity of the catalyst, and the dual-activity characteristics can realize the one-step preparation of dimethyl carbonate under relatively mild conditions;

[0057] (2) The solid base of the immobilized ionic liquid catalyst prepared by the present invention serves as a carrier of the Lewis acid composite ionic liquid. Its dendritic fiber structure is conducive to the diffusion of reactant molecules to the active sites and can effectively fix the ionic liquid, so that the catalyst exhibits high activity and high stability in the one-step preparation of dimethyl carbonate reaction;

[0058] (3) The immobilized ionic liquid catalyst provided by the present invention can be separated and recovered by a simple centrifugation operation after the reaction, which is simple to operate and reduces equipment investment costs. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0060] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0061] Gas chromatography test conditions:

[0062] The injection port temperature was 240°C, and the split ratio was 50:1. The column oven temperature program was: 60°C for 10 min, then increased to 160°C at 10°C / min, and then increased to 220°C at 20°C / min. The detector was FID, and the detection temperature was 240°C.

[0063] The main raw material information used in the examples is as follows:

[0064] N-methylimidazole: 99%, Aladdin

[0065] N-Ethylimidazole: 99%, Aladdin

[0066] N-propylimidazole: 99%, Aladdin

[0067] Butane bromide: 99%, Inokane

[0068] Chlorobutyl: 99%, Inokane

[0069] Iodine butane: 99%, Inokane

[0070] Zinc bromide: 98%, Inokite

[0071] Zinc chloride: 98%, Inokite

[0072] Zinc iodide: 98%, Inokane

[0073] Propylene carbonate: 99%, Inokite

[0074] Hexadecyltrimethylammonium bromide: 99%, Inokite

[0075] Urea: 99.999%, Inokane

[0076] Tetraethoxysilane: 99%, Inokite

[0077] Tetramethoxysilane: 99%, Inokane

[0078] Tetrapropoxysilane: 99%, Inokane

[0079] n-Pentanol: 99%, Inokane

[0080] Cyclohexane: AR, Inokane

[0081] Potassium acetate: 99%, Inokane

[0082] Lithium acetate: 99%, Inokane

[0083] Sodium acetate: 99%, Inokane

[0084] Toluene: ≥99.5%, Komiou

[0085] Ethylbenzene: ≥99.5%, Komiou

[0086] Example 1 Preparation of immobilized ionic liquid catalyst

[0087] (1) Preparation of halogenated alkyl imidazole: 8.5 g of N-methyl imidazole was added to a 50 mL three-necked flask and heated to 75 °C under magnetic stirring. Subsequently, 15 g of bromobutyl was added dropwise through a constant pressure funnel and reacted at 75 °C for 24 h. After cooling, the mixture was washed three times with ethyl acetate and rotary evaporated at 0.08 MPa and 70 °C for 1 h. Subsequently, the mixture was vacuum dried at 70 °C for 12 h to obtain 1-butyl-3-methyl imidazole bromide.

[0088] (2) Preparation of Lewis acid composite ionic liquid: 11.75 g of 1-butyl-3-methylimidazole bromide and 1 g of zinc bromide were placed in 120 mL of propylene carbonate, reacted at 95 °C for 24 h, and the product was vacuum dried at 60 °C for 12 h to prepare a Lewis acid composite ionic liquid.

[0089] (3) Preparation of dendritic fibrous silica: Dissolve 0.6 g of hexadecyltrimethylammonium bromide and 0.72 g of urea in 60 mL of water and stir continuously at room temperature for 6 h to completely dissolve the solid. Then, add 3.2 mL of tetraethoxysilane, 3.6 mL of n-pentanol and 60 mL of cyclohexane dropwise to the above mixture and mix them evenly by ultrasonication for 1 h. Transfer the mixture to a polytetrafluoroethylene hydrothermal autoclave and react in an oven at 80 °C for 24 h. After cooling to room temperature, wash with deionized water and anhydrous ethanol until neutral, then dry in an oven overnight, and finally calcine in a muffle furnace at 550 °C for 6 h to obtain dendritic fibrous silica.

[0090] (4) Preparation of solid base: 0.02 g of potassium acetate was dissolved in 5 mL of deionized water, and added dropwise to 0.3 g of dendritic fibrous silica. The mixture was stirred at room temperature for 12 h, allowed to stand at room temperature for 12 h, and then dried at 80 °C for 12 h. Finally, the mixture was calcined in a muffle furnace at 450 °C for 2 h to obtain a solid base.

[0091] (5) Preparation of immobilized ionic liquid: 0.3 g of solid base carrier was dispersed in 25 mL of toluene and heated at N 2 Under protection, 0.8 g of Lewis acid composite ionic liquid was added dropwise, reacted at 110°C, condensed and refluxed for 12 hours, cooled to room temperature after the reaction, extracted with dichloromethane for 12 hours, and then vacuum dried at 70°C for 12 hours to obtain a solid-supported ionic liquid catalyst.

[0092] Example 2 Preparation of immobilized ionic liquid catalyst

[0093] (1) Preparation of halogenated alkyl imidazole: 8.5 g of N-methyl imidazole was added to a 50 mL three-necked flask and heated to 75 °C under magnetic stirring. Subsequently, 20 g of bromobutyl was added dropwise through a constant pressure funnel and reacted at a constant temperature of 80 °C for 24 h. After cooling, the mixture was washed three times with ethyl acetate and rotary evaporated at 0.08 MPa and 70 °C for 1 h. Subsequently, the mixture was vacuum dried at 70 °C for 12 h to obtain 1-butyl-3-methyl imidazole bromide.

[0094] (2) Preparation of Lewis acid composite ionic liquid: 8.5 g of 1-butyl-3-methylimidazole bromide and 1 g of zinc bromide were placed in 120 mL of propylene carbonate, reacted at 110 °C for 24 h, and the product was vacuum dried at 60 °C for 12 h to prepare a Lewis acid composite ionic liquid.

[0095] (3) Preparation of dendritic fibrous silica: Dissolve 1 g of hexadecyltrimethylammonium bromide and 1.2 g of urea in 80 mL of water and stir continuously at room temperature for 6 h to completely dissolve the solid. Then, add 1.6 mL of tetraethoxysilane, 3.6 mL of n-pentanol and 60 mL of cyclohexane dropwise to the mixture and mix evenly by ultrasonication for 1 h. Transfer the mixture to a polytetrafluoroethylene hydrothermal reactor and react in an oven at 80 °C for 24 h. After cooling to room temperature, wash with deionized water and anhydrous ethanol until neutral, then dry in an oven overnight, and finally calcine in a muffle furnace at 500 °C for 5 h to obtain dendritic fibrous silica.

[0096] (4) Preparation of solid base: Dissolve 0.02 g of potassium acetate in 5 mL of deionized water, add dropwise to 0.25 g of dendritic fibrous silica, stir at room temperature for 12 h, let stand at room temperature for 12 h, then dry at 80 °C for 12 h, and finally calcine in a muffle furnace at 400 °C for 1.5 h to obtain a solid base.

[0097] (5) Preparation of immobilized ionic liquid: 0.2 g of solid base carrier was dispersed in 25 mL of toluene and heated at N 2 1 g of Lewis acid composite ionic liquid was added dropwise under protection, reacted at 100°C, condensed and refluxed for 12 hours, cooled to room temperature after the reaction, extracted with dichloromethane for 12 hours, and then vacuum dried at 70°C for 12 hours to obtain a solid-supported ionic liquid catalyst.

[0098] Example 3 Preparation of immobilized ionic liquid catalyst

[0099] (1) Preparation of halogenated alkyl imidazole: 8.5 g of N-methyl imidazole was added to a 50 mL three-necked flask and heated to 75 °C under magnetic stirring. Subsequently, 25 g of bromobutyl was added dropwise through a constant pressure funnel and reacted at a constant temperature of 90 °C for 24 h. After cooling, the mixture was washed three times with ethyl acetate and rotary evaporated at 0.08 MPa and 70 °C for 1 h. Subsequently, the mixture was vacuum dried at 70 °C for 12 h to obtain 1-butyl-3-methyl imidazole bromide.

[0100] (2) Preparation of Lewis acid composite ionic liquid: 13.5 g of 1-butyl-3-methylimidazole bromide and 1 g of zinc bromide were placed in 120 mL of propylene carbonate, reacted at 95 °C for 24 h, and the product was vacuum dried at 60 °C for 12 h to prepare a Lewis acid composite ionic liquid.

[0101] (3) Preparation of dendritic fibrous silica: Dissolve 1.5 g of hexadecyltrimethylammonium bromide and 1.8 g of urea in 100 mL of water and stir continuously at room temperature for 6 h to completely dissolve the solid. Then, add 6.4 mL of tetraethoxysilane, 3.6 mL of n-pentanol and 60 mL of cyclohexane dropwise to the above mixture and mix them evenly by ultrasonication for 1 h. Transfer the mixture to a polytetrafluoroethylene hydrothermal autoclave and react in an oven at 80 °C for 24 h. After cooling to room temperature, wash with deionized water and anhydrous ethanol until neutral, then dry in an oven overnight, and finally calcine in a muffle furnace at 600 °C for 8 h to obtain dendritic fibrous silica.

[0102] (4) Preparation of solid base: Dissolve 0.02 g of potassium acetate in 5 mL of deionized water, add dropwise to 0.5 g of dendritic fibrous silica, stir at room temperature for 12 h, let stand at room temperature for 12 h, then dry at 80 °C for 12 h, and finally calcine in a muffle furnace at 500 °C for 3 h to obtain a solid base.

[0103] (5) Preparation of immobilized ionic liquid: 0.3 g of solid base carrier was dispersed in 25 mL of toluene and heated at N 2 Under protection, 2 g of Lewis acid composite ionic liquid was added dropwise, reacted at 130°C, condensed and refluxed for 12 hours, cooled to room temperature after the reaction, extracted with dichloromethane for 12 hours, and then vacuum dried at 70°C for 12 hours to obtain a solid-supported ionic liquid catalyst.

[0104] Example 4 Preparation of immobilized ionic liquid catalyst

[0105] (1) Preparation of halogenated alkyl imidazole: Add 8.5 g of N-ethyl imidazole into a 50 mL three-necked flask and heat to 75 °C under magnetic stirring. Then, add 15 g of chlorobutane dropwise through a constant pressure funnel and react at 75 °C for 24 h. After cooling, wash with ethyl acetate three times, rotary evaporate at 0.08 MPa and 70 °C for 1 h, and then vacuum dry at 70 °C for 12 h to obtain 1-butyl-3-ethyl imidazole chloride.

[0106] (2) Preparation of Lewis acid composite ionic liquid: 11.75 g of 1-butyl-3-ethylimidazole chloride and 1 g of zinc chloride were placed in 120 mL of propylene carbonate, reacted at 95 °C for 24 h, and the product was vacuum dried at 60 °C for 12 h to prepare a Lewis acid composite ionic liquid.

[0107] (3) Preparation of dendritic fibrous silica: Dissolve 0.6 g of tetradecyltrimethylammonium bromide and 0.72 g of urea in 60 mL of water and stir continuously at room temperature for 6 h to completely dissolve the solid. Then, add 3.2 mL of tetramethoxysilane, 3.6 mL of n-pentanol and 60 mL of cyclohexane dropwise to the above mixture and mix them evenly by ultrasonication for 1 h. Transfer the mixture to a polytetrafluoroethylene hydrothermal autoclave and react in an oven at 80 °C for 24 h. After cooling to room temperature, wash with deionized water and anhydrous ethanol until neutral, then dry in an oven overnight, and finally calcine in a muffle furnace at 550 °C for 6 h to obtain dendritic fibrous silica.

[0108] (4) Preparation of solid base: 0.02 g of lithium acetate was dissolved in 5 mL of deionized water, added dropwise to 0.3 g of dendritic fibrous silica, stirred at room temperature for 12 h, allowed to stand at room temperature for 12 h, then dried at 80 °C for 12 h, and finally calcined in a muffle furnace at 450 °C for 2 h to obtain a solid base.

[0109] (5) Preparation of immobilized ionic liquid: 0.3 g of solid base carrier was dispersed in 25 mL of ethylbenzene under N 2 Under protection, 0.8 g of Lewis acid composite ionic liquid was added dropwise, reacted at 110°C, condensed and refluxed for 12 hours, cooled to room temperature after the reaction, extracted with dichloromethane for 12 hours, and then vacuum dried at 70°C for 12 hours to obtain a solid-supported ionic liquid catalyst.

[0110] Example 5 Preparation of immobilized ionic liquid catalyst

[0111] (1) Preparation of halogenated alkyl imidazole: 8.5 g of N-propyl imidazole was added to a 50 mL three-necked flask and heated to 75 °C under magnetic stirring. Then 15 g of iodobutane was added dropwise through a constant pressure funnel and reacted at 75 °C for 24 h. After cooling, the mixture was washed three times with ethyl acetate and rotary evaporated at 0.08 MPa and 70 °C for 1 h. Then, the mixture was vacuum dried at 70 °C for 12 h to obtain 1-butyl-3-propyl imidazole iodide.

[0112] (2) Preparation of Lewis acid composite ionic liquid: 11.75 g of 1-butyl-3-propylimidazole iodide and 1 g of zinc iodide were placed in 120 mL of propylene carbonate, reacted at 95 °C for 24 h, and the product was vacuum dried at 60 °C for 12 h to prepare a Lewis acid composite ionic liquid.

[0113] (3) Preparation of dendritic fibrous silica: Dissolve 0.6 g of octadecyltrimethylammonium bromide and 0.72 g of urea in 60 mL of water and stir continuously at room temperature for 6 h to completely dissolve the solid. Then, add 3.2 mL of tetrapropoxysilane, 3.6 mL of n-pentanol and 60 mL of cyclohexane dropwise to the above mixture and mix them evenly by ultrasonication for 1 h. Transfer the mixture to a polytetrafluoroethylene hydrothermal autoclave and react in an oven at 80 °C for 24 h. After cooling to room temperature, wash with deionized water and anhydrous ethanol until neutral, then dry in an oven overnight, and finally calcine in a muffle furnace at 550 °C for 6 h to obtain dendritic fibrous silica.

[0114] (4) Preparation of solid base: 0.02 g of sodium acetate was dissolved in 5 mL of deionized water, and added dropwise to 0.3 g of dendritic fibrous silica. The mixture was stirred at room temperature for 12 h, allowed to stand at room temperature for 12 h, and then dried at 80 °C for 12 h. Finally, the mixture was calcined in a muffle furnace at 450 °C for 2 h to obtain a solid base.

[0115] (5) Preparation of immobilized ionic liquid: 0.3 g of solid base carrier was dispersed in 25 mL of toluene and heated at N 2 Under protection, 0.8 g of Lewis acid composite ionic liquid was added dropwise, reacted at 110°C, condensed and refluxed for 12 hours, cooled to room temperature after the reaction, extracted with dichloromethane for 12 hours, and then vacuum dried at 70°C for 12 hours to obtain a solid-supported ionic liquid catalyst.

[0116] Application Example 1: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0117] Methanol and propylene oxide were added into a high-pressure reactor in a mass ratio of 4:1, and the immobilized ionic liquid catalyst prepared in Example 1 was added (the amount added was 0.5 wt% of the mass of propylene oxide). 2The pressure was 2MPa, and the temperature was raised to 100°C under stirring, and the reaction was carried out at a constant temperature for 4h. After the reaction was completed, the mixture was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of propylene oxide was calculated to be 99% and the yield of dimethyl carbonate was 63.2%. After the ionic liquid was reused 5 times, the conversion rate of propylene oxide was 98.5% and the yield of dimethyl carbonate was 62.5%, with no significant decrease.

[0118] Application Example 2: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0119] Methanol and propylene oxide were added into a high-pressure reactor in a mass ratio of 2:1, and the immobilized ionic liquid catalyst prepared in Example 2 was added (the amount added was 0.1 wt% of the mass of propylene oxide). 2 The pressure was raised to 2.5 MPa, and the temperature was raised to 100°C under stirring, and the reaction was carried out at a constant temperature for 4 hours. After the reaction was completed, the mixture was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of propylene oxide was calculated to be 97% and the yield of dimethyl carbonate was 60.5%. After the ionic liquid was reused 5 times, the conversion rate of propylene oxide was 96% and the yield of dimethyl carbonate was 59%, with no significant decrease.

[0120] Application Example 3: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0121] Methanol and propylene oxide were added into a high-pressure reactor in a mass ratio of 3:1, and the immobilized ionic liquid catalyst prepared in Example 3 was added (the amount added was 1 wt% of the mass of propylene oxide). 2 The pressure was 3 MPa, and the temperature was raised to 120°C under stirring, and the reaction was carried out at a constant temperature for 3 hours. After the reaction was completed, the mixture was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of propylene oxide was calculated to be 98.6% and the yield of dimethyl carbonate was 63%. After the ionic liquid was reused 5 times, the conversion rate of propylene oxide was 98% and the yield of dimethyl carbonate was 62.2%, with no significant decrease.

[0122] Application Example 4: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0123] Methanol and propylene oxide were added into a high-pressure reactor in a mass ratio of 5:1, and the immobilized ionic liquid catalyst prepared in Example 4 was added (the amount added was 2 wt% of the mass of propylene oxide). 2The pressure was 4 MPa, and the temperature was raised to 120°C under stirring, and the reaction was carried out at a constant temperature for 5 hours. After the reaction was completed, the mixture was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of propylene oxide was calculated to be 99% and the yield of dimethyl carbonate was 63%. After the ionic liquid was reused 5 times, the conversion rate of propylene oxide was 98.5% and the yield of dimethyl carbonate was 62.1%, with no significant decrease.

[0124] Application Example 5: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0125] Methanol and propylene oxide were added into a high-pressure reactor in a mass ratio of 4:1, and the immobilized ionic liquid catalyst prepared in Example 5 was added (the amount added was 0.5 wt% of the mass of propylene oxide). 2 The pressure was 3 MPa, and the temperature was raised to 100 ° C under stirring, and the reaction was kept at a constant temperature for 4 hours. After the reaction was completed, it was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of propylene oxide was calculated to be 99% and the yield of dimethyl carbonate was 63%. After the ionic liquid was reused 5 times, the conversion rate of propylene oxide was 97% and the yield of dimethyl carbonate was 59%, with no significant decrease.

[0126] Application Example 6: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0127] Methanol and ethylene oxide were added into a high-pressure reactor in a mass ratio of 4:1, and the immobilized ionic liquid catalyst in Example 1 was added (the amount added was 0.5 wt% of the mass of ethylene oxide). 2 The pressure was 3 MPa, and the temperature was raised to 100 ° C under stirring, and the reaction was kept at a constant temperature for 4 hours. After the reaction was completed, it was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene oxide was calculated to be 99.2% and the yield of dimethyl carbonate was 64%. After the ionic liquid was reused 5 times, the conversion rate of ethylene oxide was 98.7% and the yield of dimethyl carbonate was 62.8%, with no significant decrease.

[0128] Application Example 7: One-step preparation of dimethyl carbonate from alkylene oxide catalyzed by immobilized ionic liquid catalyst

[0129] Methanol and ethylene oxide were added into a high-pressure reactor in a mass ratio of 2:1, and the immobilized ionic liquid catalyst in Example 2 was added (the amount added was 0.1 wt% of the mass of ethylene oxide). 2The pressure was raised to 2.5 MPa, and the temperature was raised to 100°C under stirring, and the reaction was carried out at a constant temperature for 4 hours. After the reaction was completed, the mixture was cooled to room temperature and the catalyst was separated and recovered by centrifugation. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene oxide was calculated to be 98% and the yield of dimethyl carbonate was 61.2%. After the ionic liquid was reused 5 times, the conversion rate of ethylene oxide was 96.5% and the yield of dimethyl carbonate was 60.2%, with no significant decrease.

Claims

1. An immobilized ionic liquid catalyst, characterized in that: The catalyst comprises a Lewis acid composite ionic liquid and a solid base, wherein the Lewis acid composite ionic liquid is a complex of an imidazole ionic liquid and a Lewis acid, and the solid base serves as a carrier of the Lewis acid composite ionic liquid; Among them, the imidazolium ionic liquid is a halogenated alkyl imidazolium ionic liquid; the Lewis acid is a metal halide; the solid base is a dendritic fibrous silica loaded with an alkali metal; the mass ratio of the Lewis acid composite ionic liquid to the solid base is (2~10):

1.

2. The catalyst according to claim 1, characterized in that in, The alkali metal is one of lithium, sodium, potassium and cesium.

3. A method for preparing an immobilized ionic liquid catalyst, characterized in that: The following steps are involved: Step 1: N-alkyl imidazole and halogenated alkane are stirred and mixed, reacted under heating conditions, and washed, rotary evaporated, and dried after the reaction is completed to prepare a halogenated alkyl imidazole ionic liquid; the halogenated alkyl imidazole ionic liquid is stirred and mixed with a Lewis acid, reacted under heating conditions, and dried after the reaction is completed to prepare a Lewis acid composite ionic liquid, wherein the Lewis acid is a metal halide; Step 2: preparing dendritic fibrous silica by a hydrothermal method; using alkali metal acetate as a precursor, loading the alkali metal in the alkali metal acetate onto the dendritic fibrous silica, and obtaining a solid base after calcination; Step 3: The Lewis acid composite ionic liquid reacts with a solid base to obtain a solid-supported ionic liquid catalyst, wherein the mass ratio of the Lewis acid composite ionic liquid to the solid base is (2-10):

1.

4. The method for preparing an immobilized ionic liquid catalyst according to claim 3, characterized in that: in, In step 1, In the step of reacting N-alkylimidazole with alkyl halide, N-alkylimidazole is N-methylimidazole, N-ethylimidazole, N-propylimidazole, or N-butylimidazole; The halogenated alkane is butyl bromide, butyl chloride, or butyl iodide; The mass ratio of N-alkylimidazole to halogenated alkane is 1:(1~4); The reaction temperature is 70~120℃ and the reaction time is 20~30h; In the step of reacting the halogenated alkyl imidazolium ionic liquid with the Lewis acid, The mass ratio of the halogenated alkyl imidazolium ionic liquid to the Lewis acid is (5-20):1; The reaction temperature is 90~120℃ and the reaction time is 20~30h.

5. The method for preparing an immobilized ionic liquid catalyst according to claim 3 or 4, characterized in that: in, In step 2, in the preparation of dendritic fibrous silica, Alkyl ammonium bromide and urea are dissolved in water, and then tetraalkoxysilane is added, and the resulting mixed solution is subjected to a hydrothermal reaction. After the reaction is completed, the reaction solution is calcined to obtain dendritic fibrous silica; The hydrothermal reaction temperature is 70-90°C, and the hydrothermal reaction time is 20-30h; The calcination temperature is 500-600°C and the calcination time is 5-8h; The mass volume ratio of alkylammonium bromide to tetraalkoxysilane is 1:(1-10); The mass volume ratio of urea to tetraalkoxysilane is 1:(1-10); The alkylammonium bromide is selected from one or more of hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; The tetraalkoxysilane is selected from one or more of tetraethoxysilane, tetramethoxysilane and tetrapropoxysilane.

6. The method for preparing an immobilized ionic liquid catalyst according to claim 5, characterized in that: in, In step 2, in the preparation of the solid base, The alkali metal acetate is dissolved in water, and added dropwise to the dendritic fibrous silica, and stirred for reaction. After the reaction is completed, the reaction solution is allowed to stand, and then roasted to obtain a solid base; The reaction temperature is 15-35°C and the reaction time is 10-15h; The calcination temperature is 400-500°C and the calcination time is 1-3h; The alkali metal acetate is selected from potassium acetate, lithium acetate, sodium acetate, or cesium acetate; The mass ratio of dendritic fibrous silica to alkali metal acetate is (10-40):

1.

7. The method for preparing an immobilized ionic liquid catalyst according to claim 6, characterized in that: in, In step 2, in the preparation of the solid base, the reaction temperature is 20-30°C.

8. The method for preparing an immobilized ionic liquid catalyst according to claim 3 or 4, characterized in that: in, In step 3, The solid base is first dispersed in a solvent, the mass volume ratio of the solid base to the solvent is 1:(50-100), and the solvent is selected from one or more of toluene, ethylbenzene, and benzene; adding Lewis acid composite ionic liquid dropwise to react; The reaction temperature is 90~130℃, and the reaction time is 10~20h; After the reaction is completed, the solid-supported ionic liquid catalyst is obtained by extraction with a solvent and drying.

9. A method for preparing dimethyl carbonate, characterized in that: The following steps are involved: The immobilized ionic liquid catalyst prepared by the method according to any one of claims 3 to 8, methanol and alkylene oxide are added into a high-pressure reactor in a certain proportion, carbon dioxide is introduced to react, and after the reaction is completed, the immobilized ionic liquid catalyst is recovered by centrifugation, and dimethyl carbonate is obtained by distillation separation.

10. The method for preparing dimethyl carbonate according to claim 9, characterized in that: in, The amount of the immobilized ionic liquid catalyst added is 0.1-5wt% of the alkylene oxide; The mass ratio of methanol to alkylene oxide is 2:1-5:1; Introduce carbon dioxide to control the reaction pressure at 2-4MPa; The reaction temperature is 80-120°C; The reaction time is 1h-5h; The alkylene oxide is ethylene oxide or propylene oxide.

11. Use of the immobilized ionic liquid catalyst according to claim 1 or 2 or the immobilized ionic liquid catalyst prepared by the method according to any one of claims 3 to 8 in catalyzing the one-step preparation of dimethyl carbonate from alkylene oxide.