CN105233877A - Preparation method for porous spongy chitosan palladium-supported catalytic material - Google Patents

Abstract

The invention relates to a preparation method of a porous spongy chitosan-supported palladium catalytic material for organic reaction catalysis, and provides a porous spongy chitosan-supported palladium catalytic material for organic reaction catalysis and a preparation method thereof. The catalytic material uses chitosan as a polymer carrier starting material, directly uses palladium ions as a crosslinking agent to obtain a palladium crosslinked chitosan porous gel catalytic material, and the catalytic material has an open three-dimensional porous sponge structure, The porosity is 60-80%, the active component palladium is the crosslinking point of the gel network, and its mass percentage is less than or equal to 1.5% by weight of the catalytic material. The prepared material has good catalytic performance in the application of organic coupling reaction, and can be reused many times.

Description

A kind of preparation method of porous spongy chitosan supported palladium catalytic material

Technical field:

The invention relates to a method for preparing a porous spongy chitosan-loaded palladium catalytic material used for organic reaction catalysis, and belongs to the technical field of chemical catalyst preparation technology.

Background technique:

Chitosan is considered to be a good biopolymer carrier for the preparation of supported transition metal catalytic materials, which is mainly due to the large number of polar groups such as amino and hydroxyl groups in its molecular structure, which can be combined with transition metal palladium plasma Form a strong complex. According to existing literature reports, in the preparation process of chitosan-supported palladium catalytic materials using chitosan as a carrier, adsorption method is the most commonly used transition metal loading method. The general process is as follows: chitosan is now prepared A carrier solid of a certain shape is then immersed in a solution of transition metal ions such as palladium ions, and the loading of transition metals is realized through the complexation of palladium ions and polar groups of the polymer matrix. However, this loading method is often affected by the polymer aggregate structure and the complexation is uneven; the obtained chitosan-supported palladium fiber membrane even needs to be processed after solvent rinsing to remove some weakly complexed palladium. Another less commonly used method is the direct complexation crosslinking method, that is, in the solution state, the polymer and the transition metal palladium ion undergo a sufficient complexation crosslinking reaction to form a gel, and then make various forms of catalysts . However, in this method, due to the strong complexation between chitosan and transition metal, the viscosity of the system rises rapidly, and the transition metal loading cannot be too high, so it is not easy to obtain a heterogeneous catalytic material with a suitable catalyst loading.

Invention content :

The purpose of the invention is to provide a highly active chitosan palladium catalytic material and a preparation method thereof for the deficiencies in the prior art.

Concrete, in the present invention, we carry out technological improvement to direct complexation cross-linking method, utilize the chitosan of middle molecular weight as polymer carrier starting material, take the chitosan solution of low concentration as starting solution, directly utilize The transition metal palladium ion is used as a cross-linking agent without additional chemical cross-linking, and the gel solution is freeze-dried to form a film that can tolerate high-viscosity solution processing to achieve highly active porous sponge-like chitosan-loaded palladium catalytic materials. preparation.

The first aspect of the present invention is to provide a kind of porous spongy chitosan loaded palladium catalytic material for organic reaction catalysis, described catalytic material uses chitosan as polymer carrier starting material, directly utilizes palladium ion as cross-linking agent to obtain a palladium cross-linked chitosan porous gel catalytic material, the catalytic material has an open three-dimensional porous sponge-like structure, a porosity of 60-80%, and the active component palladium is the crosslinking point of the gel network, and its mass The percentage content is less than or equal to 1.5% by weight of the catalytic material.

Another aspect of the present invention is a preparation method of a porous spongy chitosan-supported palladium catalytic material, which is characterized in that it comprises the following steps: (1) take quantitative chitosan powder, add 2% acetic acid solution, and form a shell A mixed solution with a polysaccharide content (by weight) of 0.3-2%, let stand, defoam, and reserve; (2) Take quantitative solid PdCl ₂ , add distilled water, then add NaCl, heat and stir to dissolve completely, Pd ^{2 +} concentration is 0.01-0.05mol/L; (3) Add Pd ²⁺ solution dropwise to the above-mentioned chitosan solution under continuous stirring. With the gradual addition of Pd ²⁺ solution, the solution viscosity gradually increases until Form a gel; (4) Cast the gel solution into a petri dish, freeze it in a low-temperature refrigerator, and keep it at -20oC for 24 hours. (5) Freeze the frozen gel solution through a freeze dryer to form a film. The palladium cross-linked chitosan porous gel catalyst material is obtained, soaked in alkali to neutralize the residual acid, and finally washed with water and dried to obtain the final catalyst material.

Preferably:

The chitosan used in the step (1) has a molecular weight range of 50,000-200,000, and a deacetylation degree range of 70%-98%.

More preferably, the chitosan raw material used in the step (1) has a molecular weight range of 100,000, and a deacetylation degree range of 95%.

In the step (3), transition metal palladium ions are used to directly cross-link chitosan molecules without additional chemical cross-linking treatment, and the amount of palladium ions added is 0-1.5% of the weight of the carrier;

In the step (5), a freeze dryer is used to freeze-dry the low-temperature frozen chitosan-complexed palladium gel to form a film, and the solvent water molecules in the gel are directly sublimated from solid to gas, forming a sponge-like three-dimensional porous Material.

Compared with the prior art, the porous spongy chitosan supported palladium catalytic material provided by the inventive method has the following advantages:

(1) The preparation process is simple and the equipment requirements are low.

(2) Using transition metal palladium ions to directly cross-link chitosan molecules without additional chemical cross-linking treatment, changing the concentration of chitosan initial solution and the amount of transition metal palladium metal ions can realize the improvement of catalytic material performance (including pore structure, mechanical properties, etc.).

(3) The catalytic material has a high porosity. Palladium is not only the active center of the material but also the crosslinking point of the material. After the reaction, it is easy to filter and separate from the reaction solution.

(4) After the reaction solution is separated out of the reactor, there is no need for complicated post-treatment, as long as the catalyst is simply cleaned and dried, and the reaction raw materials are added again to start a new reaction.

Description of drawings:

Fig. 1 is a flow chart of the preparation process of the catalytic material in Example 1 of the present invention.

Fig. 2 is a photograph of the appearance of the catalytic material prepared in Example 1 of the present invention.

detailed description:

The present invention will be further described below in combination with specific embodiments.

The preparation of embodiment 1 catalytic material

The preparation process flowchart of catalytic material in the present embodiment is as shown in Figure 1, specifically comprises the following steps:

1. Preparation of dilute chitosan solution: Take 1g of pharmaceutical grade chitosan powder (molecular weight: 100,000, degree of deacetylation: 95%), dissolve in 2% 300ml acetic acid solution to form a mixed solution, and keep stirring for 2 hours to form a homogeneous phase Solution, let it stand for 2h for defoaming.

2. Preparation of palladium ion direct cross-linked chitosan gel: Weigh 0.3g palladium chloride, add 100ml distilled water, add 5g sodium chloride in a conical flask, heat and stir to completely dissolve to form Na ₂ PdCl ₄ solution; use a pipette to pipette an appropriate amount of Na ₂ PdCl ₄ solution, and under magnetic stirring, add drop by drop to 100ml of the above dilute chitosan solution. When the amount is about 5ml, the critical gel point appears in the system.

3. Preparation of porous spongy chitosan-supported palladium catalytic material: pour the above-mentioned gel solution into a petri dish, and place it in a freezer at minus 20oC for 24 hours; then, take out the frozen gel and store it in FD-1A- Freeze-dry in a 50-type freeze dryer to obtain light yellow porous chitosan-supported palladium catalytic material; neutralize with 1% sodium hydroxide solution to remove residual acid in the material, rinse with water to be neutral, and dry to obtain the final catalytic material. Figure 2 is a photo of the appearance of the catalytic material prepared in this example.

Application example 1

The porous spongy chitosan supported palladium catalytic material that embodiment 1 makes is carried out the applied experiment of catalytic Heck reaction, and its process and result are as follows:

Porous spongy chitosan-supported palladium catalytic material catalyzes the Heck coupling reaction of halogenated aromatic hydrocarbons and acrylate compounds:

Through the test, under the following reaction conditions: iodobenzene 1mmol, butyl acrylate 2mmol, catalytic material 0.013g (palladium content is 0.0012mmol), KOAc7.5mmol, reaction solvent DMSO (or DMF) 3ml + ethylene glycol 0.2ml, at 110oC After reacting for 3 hours, the yield of butyl cinnamate was 97%. The catalyst was reused 6 times, and the yield of butyl cinnamate was above 80%, which indicated that the catalyst had good performance and was relatively stable in the Heck reaction.

Application example 2

The porous spongy chitosan supported palladium catalytic material that embodiment 1 makes is carried out the applied experiment of catalyzing Sonogashira reaction, and its process and result are as follows:

Porous sponge-like chitosan-supported palladium catalytic material catalyzes the Sonogashira coupling reaction of halogenated aromatic hydrocarbons with phenylacetylene compounds:

Through the test, under the following reaction conditions: iodobenzene 1mmol, phenylacetylene 1.2mmol, catalytic material 0.065g (palladium content is 0.006mmol), KOAc7.5mmol, reaction solvent DMSO (or DMF) 3ml + ethylene glycol 0.2ml, at 110oC After 6 hours of reaction, the yield of the coupling product was 98%. The catalyst was reused 4 times, and the coupling yield was above 80%, which indicated that the catalyst had good performance and was relatively stable in the Sonogashira reaction.

Claims (6)

1. the chitosan loaded palladium chtalyst material of porous spongy, it is characterized in that, described catalysis material take shitosan as macromolecule carrier parent material, directly utilize palladium ion as crosslinking agent, obtain palladium cross-linked chitosan porous gel catalysis material, described catalysis material has open three-dimensional porous sponge shape structure, porosity 60-80%, active component palladium is the crosslinking points of gel network, and its mass percentage is less than or equal to 1.5% of catalysis material.

2. the preparation method of the chitosan loaded palladium chtalyst material of porous spongy a kind of as claimed in claim 1, it is characterized in that, comprise the following steps: (1) takes Chitosan powder in proportion, add the acetic acid solution of 2%, be made into the mixed solution that shitosan weight ratio is 0.5-4%, leave standstill, deaeration, for subsequent use; (2) take solid palladium chloride in proportion, adding distil water, then add sodium chloride, heating, stirring make it dissolve completely, Pd ²⁺concentration is 0.01-0.05mol/L; (3) under continuous stirring, in aforementioned chitosan solution, Pd is dripped ²⁺solution, until form gel; (4) gel solution obtained is cast in culture dish, be placed in low temperature refrigerator freezing, keep-20oC left and right 24h, (5) freezing gel solution is carried out freeze-drying film forming by freeze drier, obtain palladium cross-linked chitosan porous gel catalysis material, through alkali immersion treatment with in and residual acid, washing dry, obtain final catalysis material.

3. the preparation method of the chitosan loaded palladium chtalyst material of porous spongy according to claim 2, is characterized in that, the molecular weight ranges of shitosan: 50,000-20 ten thousand.

4. the preparation method of the chitosan loaded palladium chtalyst material of porous spongy according to claim 3, is characterized in that, the molecular weight ranges of shitosan: 100,000.

5. the preparation method of the chitosan loaded palladium chtalyst material of porous spongy according to claim 2, is characterized in that, the deacetylation scope of the shitosan used: 70%-98%.

6. the preparation method of the chitosan loaded palladium chtalyst material of porous spongy according to claim 2, is characterized in that, the deacetylation scope of the shitosan used: 95%.