CN114904587B - Preparation method of cesium modified phosphotungstic acid@UiO-66/porous carbon-based composite material - Google Patents

Abstract

The invention discloses a preparation method of cesium-modified phosphotungstic acid@UiO-66/porous carbon-based composite material. Belonging to the field of biomass resource utilization, the composite material is prepared from biomass framework carbon with a porous structure and Cs uniformly distributed in a biological carbon-based material pore channel _x H _3‑x PW ₁₂ O ₄₀ Composition @ UiO-66. The catalyst prepared by the method is placed in a high-pressure reaction kettle and used for preparing furfural through cellulose conversion, the reaction condition is mild, the selectivity of 5-hydroxymethylfurfural is excellent, and the repeated use performance is good. In addition, the catalyst has the advantages of simple synthesis process, simple recovery mode, low raw material cost, environmental protection and no pollution, and has profound significance for large-scale industrial production of 5-hydroxymethylfurfural.

Description

Preparation method of cesium-modified phosphotungstic acid@UiO-66/porous carbon-based composite materials

Technical field

The invention belongs to the field of biomass resource utilization and relates to a preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material. Specifically, it relates to a Cs _x H _3-x PW ₁₂ O ₄₀ Preparation method of @UiO-66/biomass porous carbon-based composite materials and its application in cellulose dehydration.

Background technique

In the existing technology, the development and progress of social economy and science and technology are highly dependent on traditional fossil resources, and the reserves of these non-renewable resources are increasingly consumed as human needs increase. Therefore, replacing non-renewable energy with renewable energy is one of the key measures to achieve sustainable development. As a renewable resource with abundant reserves, wide sources, and low price in nature, cellulose has attracted widespread attention because of its clean, environmentally friendly and pollution-free characteristics. Its catalytic conversion into high value-added chemical products is considered an attractive and Development potential of biomass utilization. Among numerous biomass-based derivatives, 5-hydroxymethylfurfural (5-HMF), as an important platform compound, has high economic value and is usually used in medicine, petrochemical and other fields.

Using cellulose as raw material to prepare 5-HMF is mainly through chemical catalysis. The catalyst needs to have both acid catalytic sites and alkali catalytic sites, so there are high requirements for catalytic design. Patent CN103028424A discloses a preparation method of a solid acid catalyst for the synthesis of 5-hydroxymethylfurfural. The solid acid catalyst is an oxide-loaded sulfate ion or chromium ion, which is used to synthesize 5-hydroxymethylfurfural. A higher yield can be obtained. The main active components of the catalyst are sulfate particles and chromium ions, which will burden the environment to a certain extent. Patent CN 109749738 A discloses the application of sulfonated carbon quantum dots in the preparation of 5-hydroxymethylfurfural. Using biomass as raw material, carbon quantum dots containing hydroxyl and carboxyl groups on the surface are first prepared using a hydrothermal method assisted by H ₂ O ₂ , and then sulfonate the carbon quantum dots to finally obtain sulfonated carbon quantum dots. Sulfonated carbon quantum dots can be used as catalysts to catalyze the dehydration of fructose to produce 5-hydroxymethylfurfural. They have high fructose conversion activity, good 5-HMF yield and excellent stability. However, the catalyst preparation process requires sulfonation. It will cause certain pollution to the environment.

Contents of the invention

In response to the above problems, the present invention provides a preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material and its application in cellulose dehydration; the catalyst provided by the present invention has high catalytic performance and is synthesized The process is simple, the recycling method is simple, the reusability is excellent, the raw material cost is low, environmentally friendly and pollution-free, and has profound significance for large-scale industrial production.

The technical solution of the present invention is: the present invention discloses a preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material; it uses biomass-derived porous carbon-based material as a carrier, and the cesium-modified Phosphotungstic acid @UiO-66 (Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66) is the active component, and the active component is evenly dispersed in the pores of the porous carbon-based material to prepare cesium-modified Phosphotungstic acid @UiO-66/porous carbon-based composite material (i.e. Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based composite material); the specific operation steps are as follows:

Step (1): Thoroughly mix the biomass raw material and the pore-forming agent, where the mass ratio of the biomass and the pore-forming agent is (10~1):1, then add 10~100mL of ultrapure water, and heat to a boiling state. Perform reflux treatment in a boiling state for 2 to 6 hours, wash, dry, and then calcine at 500 to 1000°C for 1 to 4 hours in an _N2 atmosphere, and cool to room temperature to obtain a porous carbon-based material;

Step (2): Dissolve the metal salt and terephthalic acid in a mixed solution containing N,N-dimethylformamide and formic acid, then add phosphotungstic acid and stir evenly to obtain H ₃ PW ₁₂ O ₄₀ @UiO- 66 precursor solution;

Step (3): Mix the porous carbon-based material and the H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor solution and stir evenly, then hydroheat at 100 to 220°C for 12 to 40 hours; after the reaction is completed, cool down and filter. Stir and wash with ethanol 3 times, filter and dry to obtain H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material;

Step (4): Add H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material to the cesium salt solution, stir for 6 to 12 hours, let stand for 6 to 12 hours, and control the rotary evaporation at 60 to 100°C. After drying, the cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material (Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/porous carbon-based material) is obtained.

Further, in step (1), the biomass raw material is any one of poplar, bamboo, soybean straw and fruit shell;

The pore-forming agent is any one of zinc acetylacetonate, zinc gluconate, zinc acetate and zinc oxalate;

The mass ratio of the biomass raw material to the pore-forming agent is: 10 to 1:1;

The volume of ultrapure water added is: 10 to 100 mL;

The boiling state is: 100~120℃;

The room temperature is: 15~30℃.

Further, in step (2), the metal salt is any one of zirconium chloride, hafnium chloride, and cerium chloride;

The mass ratio of the phosphotungstic acid, terephthalic acid and metal salt is (100~1):1:(10~1); the volume ratio of N,N-dimethylformamide and formic acid in the mixed solution It is (20～1):1.

Further, in step (3), the mass ratio of the porous carbon-based material to the H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor is 1: (50~1).

Further, in step (4), the cesium salt is any one of cesium carbonate, cesium nitrate, and cesium acetate;

The mass ratio of the cesium salt to H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material is 1: (50~1).

Further, the application of the Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/porous carbon-based composite material prepared by this preparation method in cellulose dehydration reaction; the specific conditions are: in a high-pressure reactor The application method of catalyzing the dehydration and conversion of cellulose to prepare 5-hydroxymethylfurfural is to prepare a solution of cellulose and biphasic solvent H ₂ O/THF at a mass ratio of 1: (40-80) and put it into a high-pressure reaction kettle. Keep the mass ratio of catalyst to cellulose raw material as 1: (2~20), the volume ratio of H ₂ O and THF as 1: (6~3), introduce N ₂ as protective gas and adjust the initial pressure of the system to 0.5~ 1.5MPa, the reaction temperature is 160~240℃, the heating rate is 5~15℃/min, the reaction time is 1~5h, and the stirring speed is 500~1200r/min.

The beneficial effects of the present invention are: The characteristics of the present invention are: 1. The present invention studies the dehydration and transformation of cellulose to obtain 5-HMF, which can effectively alleviate the environmental pollution problems caused by excessive consumption of fossil energy and reduce the dependence on non-renewable energy. It plays a key role in sustainable development strategy; 2. This method uses porous carbon-based materials prepared from biomass as a precursor as a carrier. The raw materials are natural and renewable, with wide sources, low cost, environmental protection and pollution-free; 3. This method optimizes The traditional production process and simple synthesis process achieve high-efficiency conversion of cellulose, the recycling method is simple and efficient, and the reuse performance is excellent, which is conducive to large-scale industrial production.

Description of drawings

Figure 1 is an operation flow chart of the present invention;

Figure 2 is an SEM morphology image of the Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66(Hf)/porous poplar carbon-based composite material prepared in Example 4 of the present invention.

Detailed ways

In order to explain the technical solution of the present invention more clearly, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

As shown _in the _figure , _{the Cs} @UiO-66 (Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66) is an active component, in which the active component is evenly dispersed in the pores of the porous carbon-based material; the specific operation steps are as follows:

Step 1: Thoroughly mix the biomass raw material and the pore-forming agent. The mass ratio of the biomass and the pore-forming agent is (10~1):1. Then add 10~00mL ultrapure water and perform reflux treatment in the boiling state. 2 to 6 hours, washing, drying, and then calcining at 500 to 1000°C for 1 to 4 hours in a _N2 atmosphere, and cooling to room temperature to obtain a porous carbon-based material;

Step 2: Dissolve the metal salt and terephthalic acid with a mixed solution of N,N-dimethylformamide and formic acid, then add phosphotungstic acid, stir evenly, and obtain the H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor. solution;

Step 3: Mix the biomass porous carbon-based material and H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor solution and stir evenly, then hydroheat at 100-220°C for 12-40 hours; after the reaction is completed, cool down and filter. Stir and wash with ethanol 3 times, filter and dry to obtain H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material;

Step 4: Add H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material to the cesium salt solution, stir for 6 to 12 hours, let stand for 6 to 12 hours, and control the rotary evaporation to dryness at 60 to 100°C. That is, the cesium-modified Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/porous carbon-based composite material is obtained;

The technical solution of the present invention will be further described in detail below through examples.

Example 1

Thoroughly mix 1.5g poplar wood and 1g zinc gluconate, then add 50mL ultrapure water, perform reflux treatment in a boiling state for 4h, wash, dry, and then calcine at 800°C for 2h in a _N2 atmosphere, and cool to room temperature. Porous poplar carbon-based materials were obtained.

Example 2

Dissolve 0.48g hafnium chloride and 0.27g terephthalic acid with a mixed solution of 54mL N,N-dimethylformamide and 6mL formic acid, then add 0.3g phosphotungstic acid to obtain H ₃ PW ₁₂ O ₄₀ @UiO -66 precursor solution.

Example 3

Mix 1.0g of biomass porous carbon-based material and H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor solution and stir evenly, then hydrotherm at 100 to 220°C for 12 to 40 hours; after the reaction is completed, cool down, filter, and add ethanol Stir and wash 3 times, filter and dry to obtain H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material.

Example 4

Add 1g of H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material into 50mL of 5wt% cesium nitrate solution, stir for 12h, let stand for 12h, control the rotary evaporation to dryness at 60°C, and obtain Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based materials.

Example 5

Take 1.0g of the prepared Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material catalyst, 2.5g of cellulose, 20mL of distilled water, and 30mL of tetrahydrofuran and place them into a high-pressure reaction kettle. Pour in 1MPa of nitrogen, vent, and repeat three times to remove the air in the reaction kettle. Adjust the heating temperature to 180°C, the heating rate to 10°C/min, the reaction time to 4h, and the stirring speed to 800r/min.

Example 6

The catalytic properties of several Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based materials are shown in Table 1. The reaction conditions are the same as in Example 5.

Table 1 Comparison of catalytic performance of several Cs _x H _3-x PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material catalysts;

Finally, it should be understood that the embodiments described in the present invention are only used to illustrate the principles of the embodiments of the present invention; other modifications may also fall within the scope of the present invention; therefore, alternatives to the embodiments of the present invention are provided as examples rather than limitations. Configurations may be considered consistent with the teachings of the invention; accordingly, embodiments of the invention are not limited to those expressly introduced and described herein.

Claims (6)

1. Preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material, which is characterized by: using biomass-derived porous carbon-based materials as carriers, cesium-modified phosphotungstic acid @UiO-66 As the active component, the active component is evenly dispersed in the pores of the porous carbon-based material to prepare the cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material; The specific operation steps are as follows: Step (1), mix the biomass raw material and the pore-forming agent, add ultrapure water, heat to the boiling state, and then perform reflux treatment in the boiling state for 2 to 6 hours, wash, dry, and then in _N2 atmosphere at 500 Calculate at ~1000°C for 1 to 4 hours and cool to room temperature to prepare porous carbon-based materials; set aside; Step (2): Dissolve the metal salt and terephthalic acid in a mixed solution containing N,N-dimethylformamide and formic acid, then add phosphotungstic acid and stir, thereby producing H ₃ PW ₁₂ O ₄₀ @ UiO-66 precursor solution; ready for use; Step (3), mix and stir the porous carbon-based material to be used with the H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor solution, and then hydroheat at 100 to 220°C for 12 to 40 hours; after the reaction is completed, cool down. , filter, stir and wash with ethanol 3 times, filter and dry; thereby preparing H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material; Step (4): Add the prepared H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material to the cesium salt solution, stir for 6 to 12 hours and then let it stand for 6 to 12 hours, and control the temperature at 60 to Rotate evaporate to dryness at 100°C, and finally prepare the cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material. 2. The preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material according to claim 1, characterized in that, In step (1), the biomass raw material is any one of poplar, bamboo, soybean straw and fruit shell; The pore-forming agent is any one of zinc acetylacetonate, zinc gluconate, zinc acetate and zinc oxalate; The mass ratio of the biomass raw material to the pore-forming agent is: 10 to 1:1; The weight of the ultrapure water added is: 10~100mL; The boiling state is: 100~120℃; The room temperature is: 15~30°C. 3. The preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material according to claim 1, characterized in that, In step (2), the metal salt is any one of zirconium chloride, hafnium chloride and cerium chloride; In the mixed solution, the volume ratio of the N,N-dimethylformamide to formic acid is: 20 to 1:1; The mass ratio of the phosphotungstic acid, terephthalic acid and metal salt is: 100~1:1:10~1. 4. The preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material according to claim 1, characterized in that, In step (3), the mass ratio of the porous carbon-based material to the H ₃ PW ₁₂ O ₄₀ @UiO-66 precursor solution is: 1:50~1. 5. The preparation method of cesium-modified phosphotungstic acid @UiO-66/porous carbon-based composite material according to claim 1, characterized in that, In step (4), the cesium salt solution is any one of cesium carbonate, cesium nitrate and cesium acetate; The mass ratio of the cesium salt solution to H ₃ PW ₁₂ O ₄₀ @UiO-66/biomass porous carbon-based material is 1:50-1. 6. Application of the cesium-modified phosphotungstic acid@UiO-66/porous carbon-based composite material prepared by the preparation method of claims 1-5 in cellulose dehydration reaction.