CN103394372B - Heteropoly ionic liquid catalyst with Br*nsted-Lewis dual acidity - Google Patents

Abstract

The invention relates to a heteropolyionic liquid catalyst with Brönsted-Lewis biacidity and a preparation method thereof, belonging to the technical field of new chemical materials and preparation thereof. The synthesis steps are as follows: (1) React 1,3-propane sultone with N-methylimidazole in toluene under nitrogen protection to obtain the intermediate 1-methyl-3-(3-sulfopropyl) Imidazole mesylate (MIMPS). (2) Using the intermediate MIMPS and Al(NO ₃ ) ₃ 9H ₂ O as the source of counter-charged cations, and phosphotungstic acid as the source of anions, by adjusting the ratio of anions and cations, reacting in aqueous solution under certain conditions to obtain Brönsted -Lewis biacidic heteropolyionic liquid catalytic material. In the present invention, organic cations with sulfonic acid groups, metal aluminum ions and protons are simultaneously used as counter cations to prepare heteropoly-salt strong acid functionalized ionic liquids with Brönsted-Lewis biacidity in the cationic part. The preparation process The method is simple and easy, and can be used as an efficient catalyst for the benzylation reaction of benzyl alcohol.

Description

A Heteropolyionic Liquid Catalyst with Br*nsted-Lewis Biacidity

technical field

The invention relates to an acid-functionalized ionic liquid catalyst and a preparation method thereof, in particular to a strong-acid-functionalized heteropolyionic liquid catalyst with Brönsted-Lewis double acidity in the cationic part and a preparation method thereof, which belongs to a novel Materials and their preparation technologies.

Background technique

Functionalized ionic liquids refer to ionic liquids that introduce functional groups into ions (anions or cations), and the presence of such functional groups has a great impact on ionic liquids, making the ionic liquids have some unique properties or can meet specific requirements. Requirements, including functionalization for physical properties (such as mobility, conductivity, liquid range, solubility) and functionalization for chemical properties (polarity, acidity, chirality, coordination ability). The design of specific functionalization of ionic liquids can be achieved by introducing different functional groups, such as ionic liquids containing protic acids, ionic liquids containing chiral centers, ionic liquids with ligand properties, etc. Among them, acid-functionalized ionic liquids are a research hotspot in recent years.

Acid-functionalized ionic liquids are usually divided into three types: Lewis acid, Br?nsted acid and Br?nsted-Lewis double acid type. The typical chemical formula of Lewis acid, Br?nsted acid and Br?nsted-Lewis double acid type ionic liquid is as follows:

       

The above-mentioned traditional Brönsted acid-type ionic liquids have low acid strength and insufficient activity for certain acid-catalyzed reactions; and the Lewis acid introduced by anion has the disadvantage of being unstable to water, and it is difficult to react with water in esterification, dehydration, etc. Good separation and recovery are achieved in the acid-catalyzed reaction produced. Therefore, in the process of developing a new type of acid-functionalized ionic liquid catalyst, it is hoped that the developed one has the advantages of high acid strength and good water stability, and it is best to have both Brönsted-Lewis biacidity to meet various acid-catalyzed reactions. demand.

Organic-inorganic hybrid materials based on heteropolyacids have attracted the attention of researchers in recent years. Among them, organic salts of heteropolyacids with ionic liquid structures are one of the hot topics. Shi Jiehua et al. prepared 1-butyl-3-methylimidazolium phosphotungstate ([BMIM] ₃ PW ₁₂ O ₄₀ ) catalyst and used it in the esterification reaction of ethanol and acetic acid (Acta Catalytica Sinica, 2008, 29(7) : 629-632); Leng Yan et al. prepared an acidic polyvinylpyrrolidone-heteropolyacid hybrid catalyst, and the acid strength of the catalyst was only –3.0< H 0 < 0.8 as measured by the Hammett indicator method (Acta Catalytica Sinica, 2012 , 33(7): 1224-1228). Yan Leng et al. introduced sulfonic acid groups into organic cations to prepare strongly acidic [MIMPS] ₃ PW ₁₂ O ₄₀ , [PyPS] ₃ PW ₁₂ O ₄₀ , [TEAPS] ₃ PW ₁₂ O ₄₀ ionic liquids. It can be used as a highly efficient "reaction-guided self-separation" catalyst in the esterification reaction (Angew. Chem. Int. Ed. 2009, 48: 168-171), which has attracted the attention of researchers.

In summary, the design and synthesis of heteropolyacids with ionic liquid structure and their application in acid-catalyzed reactions is a hot topic at present, but it is still in its infancy. At present, the most effective way to increase the acid strength of heteropolyionic liquids is to introduce strong acid sulfonic acid groups into the organic cations. How to further adjust the type of acid center and effectively increase the acid strength is the key issue of research. So far, the introduction of Lewis acid centers into cationic moieties, combined with traditional Br?nsted acid cations, to create Br? None have been reported.

Contents of the invention

The purpose of the present invention is to solve the problem that the acid strength of the existing acid functionalized ionic liquid is low, to provide a novel strong acid heteropolyionic liquid catalyst with Brönsted-Lewis biacidity, and to provide this ion Liquid preparation method. The invention also provides the application of the catalyst in the benzylation reaction of anisole and benzyl alcohol.

According to the present invention, the strong-acid heteropolyionic liquid catalyst molecule general formula that provides has Brönsted-Lewis biacidity is as follows:

H _X [MIMPS] _Y Al _(3-XY)/3 PW ₁₂ O ₄₀

In the formula, MIMPS is 1-methyl-3-(3-sulfopropyl)imidazolium cation. X, Y represent the degree of replacement of protons by cations, usually, the value of X is 0 to 1, and the value of Y is 1 to 2, and X +Y<3.

According to another aspect of the present invention, the present invention also provides the above-mentioned synthetic method of the strong-acid heteropolyionic liquid with Brönsted-Lewis biacidity, and its synthetic steps are as follows:

(1) Synthesis of intermediates:

Add 0.10 mol of 1,3-propane sultone into a three-necked flask (250 mL), add 100 mL of toluene to dissolve it, then add 0.10 mol of N-methylimidazole, and react under nitrogen gas at 50 °C for 24 h under magnetic stirring. The reaction solution was suction-filtered, and the resulting white precipitate was washed three times with ethyl acetate, and dried in vacuum at 60°C for 4 h to obtain 1-methyl-3-(3-sulfopropyl) imidazolone sulfonate (MIMPS ) white precipitated powdery solid.

(2) Synthesis of Br?nsted-Lewis bis-acid type strong acid heteropolyionic liquid:

Add the intermediate MIMPS and Al(NO ₃ ) ₃ ?9H ₂ O obtained in step (1) into a three-necked flask (100 mL) in a certain proportion, and weigh phosphotungstic acid in proportion to add 40 mL of deionized Dissolve in water, add phosphotungstic acid aqueous solution into a three-necked flask, react at room temperature (25 °C) for 24 h under magnetic stirring, distill under reduced pressure, and dry in vacuum at 80 °C for 6 h to obtain a strong acid with both Brönsted-Lewis biacidity Functionalized heteropolyionic liquid catalytic materials.

The synthetic chemical process formula of ionic liquid of the present invention is as follows:

The invention also discloses the application of the strong acid heteropolyionic liquid catalyst in the benzylation reaction using anisole and benzyl alcohol as raw materials.

The strong-acid heteropolyionic liquid catalyst with Brönsted-Lewis biacidity provided by the invention has the following characteristics compared with existing acid-functionalized ionic liquids and technologies thereof:

(1) The present invention provides a method of using protons, metal aluminum ions, and imidazolium cations with sulfonic acid groups as counter cations of heteropolyanions to synthesize a new type of ionic liquid, which enriches the variety of ionic liquids;

(2) The preparation technology of the ionic liquid provided by the present invention uses alkylimidazole, sultone, aluminum nitrate, and phosphotungstic acid as raw materials, and has the advantages of low cost and simple preparation method;

(3) In the ionic liquid provided by the present invention, the organic cation has a Brönsted acidic sulfonic acid group; the metal aluminum ion has a Lewis acidity; the proton in the heteropolyacid acid salt also has a Brönsted acidity. Combining the three, the Brönsted-Lewis double-acid ionic liquid provided by the present invention has an acid strength close to that of free heteropolyacids, and has melting points and solubility properties different from free heteropolyacids and common heteropolyacids, which can be conveniently It is used as a catalytic material for reactions requiring strong acid catalysis;

(4) The present invention also provides a new type of organic-inorganic hybrid material that uses metal cations, organic cations and protons as counter cations of heteropolyanions at the same time, and provides an organic-inorganic hybrid material for this purpose. new way of

(5) The Brönsted-Lewis diacid type heteropolyionic liquid provided by the present invention is solid at room temperature, slightly soluble in water, and insoluble in toluene. At the temperature of the benzylation reaction process, it is a viscous liquid with fluidity. Cool to room temperature after the reaction, the catalyst phase settles at the bottom of the reactor, the upper organic phase is easy to pour out, and the colloidal solid catalyst can be directly used for the next reaction.

Description of drawings

FIG. 1 is the ¹ H NMR spectrum of the ionic liquid 1 prepared in Example 1.

Figure 2 is the FT-IR spectrum of ionic liquid 1 prepared in Example 1; where (a) H ₃ PW ₁₂ O ₄₀ (b) MIMPS (c) ionic liquid 1 [MIMPS]Al _2/3 PW ₁₂ O ₄₀ ( d) [MIMPS] ₃ PW ₁₂ O ₄₀ .

Fig. 3 is the acetonitrile-n-butylamine potentiometric titration curve diagram of the ionic liquid 1 prepared in Example 1.

Figure 4 is the Py -IR spectra of ionic liquids 1 and 2 prepared in Examples 1 and 2; where (a) ionic liquid 1 [MIMPS]Al _2/3 PW ₁₂ O ₄₀ (b) H ₂ [MIMPS] PW ₁₂ O ₄₀ (c) ionic liquid 2 H [MIMPS]Al _1/3 PW ₁₂ O ₄₀

Fig. 5 is the acetonitrile-n-butylamine potentiometric titration curve of ionic liquid 2 prepared in Example 2.

Fig. 6 is the acetonitrile-n-butylamine potentiometric titration curve of the ionic liquid 3 prepared in Example 3.

Detailed ways

The following examples serve to further illustrate the present invention, but do not thereby limit the present invention.

[Example 1] Synthesis of Ionic Liquid 1:

(1) Weigh 12.21 g (0.10 mol) of 1,3-propane sultone into a three-necked flask (250 mL), add 100 mL of toluene to dissolve it, then add 9.02 g (0.10 mol) of N-methylimidazole, Under magnetic stirring at 50°C, react with nitrogen gas for 24 h, filter the reaction solution with suction, wash the white precipitate three times with ethyl acetate, and dry it in vacuum at 60°C for 4 h, the white powdery solid obtained is 1-formazol 3-(3-sulfopropyl) imidazolidine sulfonate (MIMPS).

(2) Weigh 1.00 g (2.67 mmol) of Al(NO ₃ ) ₃ ?9H ₂ O and 0.82 g (4 mmol) of MIMPS into a three-neck flask (100 mL), weigh 11.52 g (4 mmol) of phosphotungstic acid in Add 40 mL of deionized water into the beaker to dissolve it, add the aqueous solution of phosphotungstic acid into the three-necked flask, react under magnetic stirring at room temperature (25 °C) for 24 h, distill under reduced pressure, and dry in vacuum at 80 °C for 6 h to obtain a white-green solid. Denote as ionic liquid 1, its structural formula is:

Its melting point is 101-103 ℃, slightly soluble in water, insoluble in toluene. As shown in Figure 1: ¹ H-NMR (500MHz, DMSO) characterization results are: δ 2.21(quint, 2H), 2.83(t, 2H), 3.83(s, 3H), 4.26(t, 2H), 7.38( d, 1H), 7.46(d, 1H), 8.70(s, 1H); as shown in Figure 2(c), the IR (KBr, v/cm -1 ) characterization results are: 3416, 1624, 1470, ¹³⁸⁴ , 1296, 1170, 1080, 1044, 981, 893, 800, 620, 595, 524; use n-butylamine potentiometric titration to measure its acid strength and acid content, as shown in Figure 3, its acid strength is 684mV (under the same conditions Phosphotungstic acid is 702 mV), the total acid content is 0.3416mmol/g (0.7913 mmol/g for phosphotungstic acid under the same conditions); pyridine-IR (KBr, v/cm -1 ) is used to characterize the type of acid center, as shown in ^the figure 4, the 1540 peak indicates the Br?nsted acid center, and the 1450 peak indicates the Lewis acid center, which proves that the ionic liquid has the characteristics of Br?nsted-Lewis double acid.

[Example 2] Synthesis of ionic liquid 2:

(1) Weigh 12.21 g (0.10 mol) of 1,3-propane sultone into a three-necked flask (250 mL), add 100 mL of toluene to dissolve it, then add 9.02 g (0.10 mol) of N-methylimidazole, Under magnetic stirring at 50°C, react with nitrogen gas for 24 h, filter the reaction solution with suction, wash the white precipitate three times with ethyl acetate, and dry it in vacuum at 60°C for 4 h, the obtained white powdery solid is MIMPS.

(2) Weigh 0.50 g (1.33 mmol) of Al(NO ₃ ) ₃ ?9H ₂ O and 1.64 g (4 mmol) of MIMPS into a three-neck flask (100 mL), weigh 11.52 g (4 mmol) of phosphotungstic acid in Add 40 mL of deionized water into the beaker to dissolve it, add the aqueous solution of phosphotungstic acid into the three-necked flask, react under magnetic stirring at room temperature (25 °C) for 24 h, distill under reduced pressure, and dry under vacuum at 80 °C for 6 h, the obtained white solid is recorded as Ionic liquid 2, its structural formula is:

Its melting point is 187-190 ℃, slightly soluble in water, insoluble in toluene. As shown in Figure 5, the acid strength is 625mV and the total acid content is 0.1708mmol/g.

[Example 3] Synthesis of ionic liquid 3:

(1) Weigh 12.21 g (0.10 mol) of 1,3-propane sultone into a three-necked flask (250 mL), add 100 mL of toluene to dissolve it, then add 9.02 g (0.10 mol) of N-methylimidazole, Under magnetic stirring at 50°C, react with nitrogen gas for 24 h, filter the reaction solution with suction, wash the white precipitate three times with ethyl acetate, and dry it in vacuum at 60°C for 4 h, the obtained white powdery solid is MIMPS.

(2) Weigh 0.50 g (1.33 mmol) of Al(NO ₃ ) ₃ ?9H ₂ O and 1.64 g (8 mmol) of MIMPS into a three-neck flask (100 mL), weigh 11.52 g (4 mmol) of phosphotungstic acid in Add 40 mL of deionized water into the beaker to dissolve it, add the aqueous solution of phosphotungstic acid into the three-necked flask, react under magnetic stirring at room temperature (25 °C) for 24 h, distill under reduced pressure, and dry under vacuum at 80 °C for 6 h, the obtained white solid is recorded as Ionic liquid 3, its structural formula is:

Its melting point is 95-99 ℃, slightly soluble in water, insoluble in toluene. As shown in Figure 6, the acid strength is 673mV and the total acid content is 0.1812mmol/g.

the

[Example 4] In a 100 mL three-necked flask equipped with a thermometer, a magnet, and a reflux condenser, 0.05 mol of anisole, 0.05 mol of benzyl alcohol and 0.10 mmol of ionic liquid 1 were added. Heating in an air bath in a magnetic stirrer at a constant temperature to the reflux temperature, after reacting for 2 h, stop the reaction, cool, decant and separate the upper organic phase, and analyze it by a gas chromatograph. The results of the reaction catalyzed by ionic liquid 1 are shown in Table 1.

[Example 5] In a 100 mL three-necked flask equipped with a thermometer, a magnet, and a reflux condenser, 0.05 mol of anisole, 0.05 mol of benzyl alcohol and 0.10 mmol of ionic liquid 2 were added. Heating in an air bath in a magnetic stirrer at a constant temperature to the reflux temperature, after reacting for 2 h, stop the reaction, cool, decant and separate the upper organic phase, and analyze it by a gas chromatograph. The results of the reaction catalyzed by ionic liquid 2 are shown in Table 1.

[Example 6] In a 100 mL three-necked flask equipped with a thermometer, a magnet, and a reflux condenser, 0.05 mol of anisole, 0.05 mol of benzyl alcohol and 0.10 mmol of ionic liquid 3 were added. Heating in an air bath in a magnetic stirrer at a constant temperature to the reflux temperature, after reacting for 2 h, stop the reaction, cool, decant and separate the upper organic phase, and analyze it by a gas chromatograph. The results of the reaction catalyzed by ionic liquid 3 are shown in Table 1.

[Comparative Example 1] In a 100 mL three-necked flask equipped with a thermometer, a magnet, and a reflux condenser, add 0.05 mol of anisole, 0.05 mol of benzyl alcohol and 0.10 mmol of ionic liquid [MIMPS] ₃ PW ₁₂ O ₄₀ . Heating in an air bath in a magnetic stirrer at a constant temperature to the reflux temperature, after reacting for 2 h, stop the reaction, cool, decant and separate the upper organic phase, and analyze it by a gas chromatograph. Table 1 shows the reaction results catalyzed by ionic liquid [MIMPS] ₃ PW ₁₂ O ₄₀ .

[Comparative Example 2] In a 100 mL three-necked flask equipped with a thermometer, a magnet, and a reflux condenser, 0.05 mol of anisole, 0.05 mol of benzyl alcohol and 0.10 mmol of ionic liquid [BMIM] ₃ PW ₁₂ O ₄₀ were added. Heating in an air bath in a magnetic stirrer at a constant temperature to the reflux temperature, after reacting for 2 h, stop the reaction, cool, decant and separate the upper organic phase, and analyze it by a gas chromatograph. Table 1 shows the results of the ionic liquid [BMIM] ₃ PW ₁₂ O ₄₀ catalyzed reaction.

Table 1 Evaluation of the reaction performance of Br?nsted-Lewis double-acidic ionic liquid catalysts

Description: under the reaction conditions provided by the present invention, ionic liquid [BMIM] ₃ PW ₁₂ O ₄₀ has no activity to the benzylation reaction of anisole and benzyl alcohol; while ionic liquid [MIMPS] ₃ PW ₁₂ O ₄₀ has relatively High activity, but the selectivity of benzylation reaction is low, there is a large part of benzyl alcohol dehydration reaction to generate by-product benzyl ether; Close to complete conversion, and the benzylation selectivity is greatly improved, and the by-product benzyl ether generation ratio is greatly reduced; the catalytic benzylation reaction performance of the three ionic liquids in Examples 4, 5, and 6 is exactly the same as that shown in Figures 3, 5, and 6. Corresponds to the acid strength data characterized by the n-butylamine potentiometric titration method.

Claims (4)

1. a heteropolyionic liquid catalyst with Brönsted-Lewis biacidity is characterized in that molecular formula is as follows: H _X [MIMPS] _Y Al _(3-XY)/3 PW ₁₂ O ₄₀ In the formula, MIMPS is 1-methyl-3-(3-sulfopropyl)imidazolium cation; X and Y represent the degree of proton substitution by cation, and the value of X is 0 to 1, and the value of Y is 1 to 2, and X+Y<3. the 2. a heteropolyionic liquid catalyst with Brönsted-Lewis biacidity as claimed in claim 1, is characterized in that its cation comprises imidazolium cation, metal aluminum ion and hydrogen proton of sulfonic acid group functionalization, and anion is phosphorus Tungstate anion. the 3. a preparation method of the heteropolyionic liquid catalyst with Brönsted-Lewis biacidity described in claim 1 or 2, is characterized in that preparation process is as follows: (1) Preparation of intermediate 1-methyl-3-(3-sulfopropyl) imidazolidine sulfonate: 1,3-propane sultone in toluene solvent and N-methylimidazole in nitrogen Reaction under protection to obtain 1-methyl-3-(3-sulfopropyl) imidazolone sulfonate white precipitated powdery solid; (2) Synthesis of ionic liquid: using the intermediate 1-methyl-3-(3-sulfopropyl) imidazolone sulfonate, Al(NO ₃ ) ₃ ?9H ₂ O as the counter cation source, phosphorus Tungstic acid is an anion source, and by adjusting the ratio of anions and cations, it reacts in an aqueous solution at room temperature to obtain a heteropolyionic liquid catalyst with Brönsted-Lewis diacidity. 4. the application of a heteropolyionic liquid catalyst with Brönsted-Lewis biacidity described in claim 1 or 2 in the benzylation reaction of catalyzed anisole and benzyl alcohol.