CN104525263A - Preparation method of cyclodextrin/montmorillonite/heteropoly acid composite catalyst - Google Patents

Abstract

The invention relates to a preparation method of a cyclodextrin/montmorillonite/heteropolyacid composite catalyst, belonging to the technical field of composite material preparation. The invention uses cyclodextrin and its derivatives and lithium montmorillonite as basic raw materials, compound them in a solution, and then add them into a heteropolyacid solution to form a three-way composite catalyst. In the composite catalyst, the molar ratio of the three components is changed to control the loading amount of the cyclodextrin and the heteropolyacid on the montmorillonite to regulate the catalytic efficiency. In the composite catalyst, montmorillonite has a large surface area, and cyclodextrin can be intercalated into the interlayer of montmorillonite, and heteropolyacid and cyclodextrin form supramolecular clathrates; the catalyst can be used for long-chain fatty acids and The esterification reaction of polyethylene glycol has a good catalytic effect and is beneficial to the recovery and reuse of the catalyst.

Description

A kind of preparation method of cyclodextrin/montmorillonite/heteropolyacid composite catalyst

technical field

The invention relates to a preparation method of a cyclodextrin/montmorillonite/heteropolyacid composite catalyst, belonging to the technical field of composite material preparation.

Background technique

Cyclodextrin (CD) is the product of cyclodextrin glycosyltransferase acting on starch. It is a cyclic oligosaccharide composed of multiple glucose molecules linked by 1,4-glycosidic bonds. It has a cavity structure that is hydrophilic on the outside and hydrophobic on the inside, and its hydrophobic cavity can combine with more organic guest molecules that match in size to form host-guest inclusion complexes, so it can be used to include inorganic and organic molecules such as drugs, Flavors and fragrances, etc., the hydrophilic hydroxyl on the outside has a chelating effect on metal ions, so it is used in sewage treatment, cosmetics, catalysts, medicine and other fields.

Montmorillonite (MMT) is a kind of silicate clay, which is a typical 2:1 layered crystal. Each unit cell is composed of two silicon-oxygen tetrahedra with a layer of aluminum-oxygen octahedron in between. They are connected by shared oxygen atoms, and the layer spacing is about 1nm. Part of the trivalent aluminum on the alumina octahedron of montmorillonite is isomorphically replaced by divalent magnesium, so that the inner surface of the layer has a negative charge, and the excess negative charge is compensated by the cations adsorbed between the layers, such as Na ⁺ , K ⁺ , Ca ^{2 +} etc., they are easily exchanged with inorganic or organic cations. Due to the layered structure of montmorillonite, it has a large specific surface area and cation exchange capacity, good adsorption performance and other unique mineral properties and physical and chemical properties. The wide range of sources and low price of montmorillonite have attracted the attention of mineral processing and environmental protection disciplines. The research on montmorillonite mineral environmental protection materials has also become a research field with broad prospects and plays an extremely important role in the fields of environmental protection and catalysis. .

Because the cavity of cyclodextrin has inclusion effect, heteropolyacid can enter its cavity to form a supramolecular complex under a certain action, and the formed inclusion complex can make the esterification reaction of alkyd acid regenerate into cyclodextrin. In the microenvironment of the cavity, the reaction concentration of alkyd is increased, thereby improving the efficiency of esterification; the dispersion of montmorillonite can facilitate the recovery and reuse of composite catalysts

Contents of the invention

The purpose of the present invention is to provide a preparation method of cyclodextrin/montmorillonite/heteropolyacid composite catalyst, cyclodextrin enters the interlayer of montmorillonite through intercalation, and heteropolyacid enters the cavity of cyclodextrin to form A supramolecular clathrate is obtained to obtain a high-efficiency esterification catalyst.

Technical scheme of the present invention: the present invention uses cyclodextrin and its derivatives and lithium montmorillonite as the basic raw materials, and after they are compounded in the solution, they are added into the solution of heteropolyacid to form a three-way composite catalyst, wherein the montmorillonite lithium The desoil is sodium montmorillonite, the cyclodextrins are α-cyclodextrin and β-cyclodextrin, and the cyclodextrin derivatives are hydroxypropyl-α-cyclodextrin and hydroxypropyl-β-cyclodextrin fine, carboxymethyl-α-cyclodextrin and carboxymethyl-β-cyclodextrin, and heteropolyacids are phosphotungstic acid, silicotungstic acid and germanotungstic acid respectively; Ratio, control the loading of cyclodextrin and heteropolyacid on montmorillonite, wherein the mass ratio of montmorillonite: cyclodextrin is 2～20:1, and the molar ratio of cyclodextrin: heteropolyacid is 1: 1~2.

The preparation method of the present invention is:

1. Ultrasonic dispersion of montmorillonite in water to obtain an expanded montmorillonite solution;

2. Add cyclodextrin and its derivatives to the above solution, and stir in a water bath at 30-50°C for 6-12 hours to obtain a cyclodextrin/montmorillonite mixture, then centrifuge and separate the precipitate. Carry out drying in oven, obtain cyclodextrin/montmorillonite compound;

3. Add the above-mentioned cyclodextrin/montmorillonite compound into the aqueous solution of heteropolyacid, then place it in a water bath at 50-80°C and stir for 4-6 hours, and finally centrifuge and dry the precipitate to obtain cyclodextrin/montmorillonite Soil removal/heteropolyacid composite catalyst.

Beneficial effects of the present invention: the present invention utilizes the large surface area of montmorillonite, inserts cyclodextrin and its derivatives on its surface and between layers, and utilizes the inclusion action of cyclodextrin to make heteropolyacids wrapped by cyclodextrin After knotting, the catalytic esterification reaction of long-chain fatty acids and polyethylene glycol is carried out in the microenvironment of the inner cavity of cyclodextrin, which is equivalent to increasing the concentration of alkyd reactants and increasing the esterification rate; and the prepared cyclodextrin The dextrin/montmorillonite/heteropolyacid composite catalyst is easy to separate and recover, and can be reused.

Detailed ways

Example 1

Put 2.78g of α-cyclodextrin (α-CD), 4.66g of sodium chloroacetate and 1.92g of sodium hydroxide in a 250mL reactor, measure 200mL of deionized water, react at 80°C for 3h, and then use an ice bath to After cooling down to room temperature, add 3mol/1 hydrochloric acid dropwise to adjust the pH value to 6, precipitate with a large amount of methanol and dissolve the precipitate several times to wash away unreacted raw materials and by-product sodium chloride. Finally, the product was exchanged with ion exchange resin (Z001×4) to convert sodium ions into hydrogen ions, and after the column was finished, the product was placed in a freeze dryer to dry for one week, and finally carboxymethylated α-cyclodextrin ( α-CMCD).

Example 2

Add 5g montmorillonite to 200mL 5g/L carboxymethyl-α-cyclodextrin aqueous solution, place the mixture in a water bath at 30°C for a stirring reaction for 12 hours, then centrifuge the mixture, remove the supernatant, and The precipitate was dried in an oven to obtain an interlayer cyclodextrin derivative/montmorillonite composite; the content of the cyclodextrin derivative in the composite was tested by TGA to be 12%.

Example 3

Add 4g of cyclodextrin derivative/montmorillonite complex (mass of cyclodextrin derivative is 0.48g) to 0.88mmol (2.5g) H3PW12O40 plus 50mL distilled water to make a solution, stir in a water bath at 60°C for 6h, and centrifuge and drying to obtain cyclodextrin/montmorillonite/heteropolyacid composite catalyst.

Example 4

The PEG (molecular weight is 200) that takes by weighing 3.84g palmitic acid and 2g adds in the there-necked flask by the mol ratio of 1.5: 1, then adds 1% cyclodextrin/montmorillonite/heteropolyacid composite catalyst (58.4mg) and 100mL of xylene was used as the water-carrying agent, reflux reaction at 140°C for 5 hours, after the reaction was completed, the catalyst was removed by filtration, and then the water-carrying agent xylene was removed by vacuum distillation, and the polyester was obtained by drying, and the components in the polyester were determined, and calculated Esterification rate.

Claims (4)

1. A preparation method of a cyclodextrin/montmorillonite/heteropolyacid composite catalyst, belonging to the technical field of composite material preparation. It is characterized in that the preparation method is as follows: (1) Ultrasonic dispersion of montmorillonite in water to obtain an expanded montmorillonite solution; (2) Add cyclodextrin and its derivatives to the above solution, stir in a water bath at 30-50°C for 6-12 hours to obtain a cyclodextrin/montmorillonite mixture, then centrifuge and precipitate The material is placed in an oven for drying to obtain a cyclodextrin/montmorillonite composite; (3) Add the above-mentioned cyclodextrin/montmorillonite complex into the aqueous solution of heteropolyacid, then place it in a water bath at 50-80°C and stir for 4-6 hours, and finally centrifuge and dry the precipitate to obtain cyclodextrin/montmorillonite Montmorillonite/heteropolyacid composite catalyst. 2. according to the preparation method of a kind of cyclodextrin/montmorillonite/heteropolyacid composite catalyst described in claims 1, it is characterized in that montmorillonite is sodium-based montmorillonite, and cyclodextrin is α-cyclodextrin Glycerin and β-cyclodextrin, cyclodextrin derivatives are hydroxypropyl-α-cyclodextrin, hydroxypropyl-β-cyclodextrin, carboxymethyl-α-cyclodextrin and carboxymethyl-β - Cyclodextrin, heteropolyacids are phosphotungstic acid, silicotungstic acid and germanotungstic acid respectively. 3. according to the preparation method of a kind of cyclodextrin/montmorillonite/heteropolyacid composite catalyst described in claim 1, it is characterized in that montmorillonite: the mass ratio of cyclodextrin is 2～20: 1, cyclodextrin The molar ratio of dextrin:heteropolyacid is 1:1～2. 4. according to the preparation method of a kind of cyclodextrin/montmorillonite/heteropolyacid composite catalyst described in claims 1, it is characterized in that montmorillonite has larger surface area, and cyclodextrin can intercalate into montmorillonite Between layers of soil, heteropolyacids and cyclodextrins form supramolecular clathrates; the catalyst can be used for the esterification reaction of long-chain fatty acids and polyethylene glycol, has a good catalytic effect, and is conducive to catalyst recovery and reuse.