CN116116371B - Double-K-base coupling material and preparation and application methods thereof - Google Patents

Abstract

The invention discloses a double-K-base coupling material, which is characterized in that K ₂CO₃ is loaded on the surface of Cu/CeZrO ₂ doped with lattice K, and the loading amount of K ₂CO₃ is 5-15 wt%. Preparing a double-K-based coupling material by doping a Cu/CeZrO ₂ solid solution with lattice K and surface loading K ₂CO₃, wherein K ₂CO₃ of the surface loading is a CO ₂ adsorption center, K ₂CO₃ is converted into KHCO ₃,KHCO₃ to decompose at 172-350 ℃ after adsorbing CO ₂ so as to release CO ₂ molecules, and the CO ₂ catalytic hydrogenation reaction under the same temperature window is promoted; the lattice doped K can increase oxygen vacancies, enhance the activation of CO ₂ molecules, promote the formation of formate intermediates and the further conversion of methanol in the CO ₂ hydrogenation reaction.

Description

A double K-based coupling material and its preparation and application method

Technical Field

The invention belongs to the technical field of new materials, and in particular relates to a double K-based coupling material and a preparation and application method thereof.

Background Art

Global carbon dioxide emissions continue to grow, causing greenhouse effects and environmental ecological problems. Although renewable energy generation has achieved significant growth, the demand for fossil fuels such as coal has not decreased significantly. How to reduce the content of _CO2 in the atmosphere and convert _CO2 into new energy has become a hot topic of research in countries around the world.

Carbon capture technology has received more and more attention, but there are risks in the process of carbon capture, and long-distance transportation leads to high production costs. Therefore, researchers have focused on expanding CCS to include "utilization", namely carbon capture and utilization (CCUS). Although there are many carbon capture methods today, they can only achieve the separation of _CO2 , and therefore cannot be recycled as a resource. Therefore, _CO2 catalytic hydrogenation to produce chemicals has become a new research hotspot. With the development and progress of hydrogen production technology, the conversion of _CO2 into high-energy-density liquid fuels through _CO2 hydrogenation is considered to be an ideal recycling route from _CO2 to resources. The use of _CO2 catalytic hydrogenation to convert _CO2 and _H2 into high-value-added chemicals not only greatly reduces the content of carbon dioxide in the atmosphere, but also produces high-value-added commodities, with good application prospects. There are many products generated by the _CO2 hydrogenation reaction, the most common products are carbon monoxide, methane, methanol and hydrocarbon compounds.

In the _CO2 capture reaction, the adsorbent is the core, and in the _CO2 hydrogenation reaction, the catalyst is the core. There are extensive studies in both _CO2 capture and _CO2 utilization at home and abroad, but most of them only involve one link of carbon capture and utilization, and the research covering both links is relatively scarce. Designing a bifunctional catalyst with high adsorption capacity, good activation ability, high conversion rate and methanol selectivity for _CO2 is of great research significance.

Summary of the invention

In view of the deficiency that most of the existing _CO2 treatment technologies only involve one link of carbon capture and utilization, the present invention provides a double K-based coupling material and its preparation and application method to solve the problem of _CO2 adsorption capture and catalytic hydrogenation coupling. The specific technical scheme of the present invention is as follows:

A double K-based coupling material is prepared by loading K ₂ CO ₃ on a lattice K-doped Cu/CeZrO ₂ surface, wherein the loading amount of K ₂ CO ₃ is 5wt%-15wt%.

A method for preparing a double K-based coupling material comprises the following steps:

Step 1, dissolving Ce(NO ₃ ) ₂ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O in deionized water, adding citric acid solution dropwise at 90 °C for chelation, stirring until a viscous sol is formed, transferring to a vacuum drying oven at 110 °C for drying for 12 h, cooling to room temperature, and then calcining at 600 °C for 4 h to obtain a CeZrO ₂ solid solution;

Step 2, dissolving KNO ₃ and Cu(NO ₃ ) ₂ in water to prepare solution A, immersing CeZrO ₂ solid solution in solution A for 6 hours, using magnetic stirring during the immersion process, and then drying, and then calcining at 500 ° C in N ₂ atmosphere for 4 hours to obtain lattice K-doped Cu/CeZrO ₂ solid solution;

Step 3, placing the lattice K-doped Cu/CeZrO ₂ solid solution obtained in step 2 in a vacuum impregnator, evacuating the vacuum, impregnating it with an equal volume of K ₂ CO ₃ solution, and then drying it to obtain the final product.

Furthermore, in step 1, the molar ratio of Ce(NO ₃ ) ₂ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O to citric acid is 1:1.2.

Furthermore, in step 2, the mass ratio of K, Cu and _CeZrO2 solid solution is 0.02:0.05:1.

The drying process in step 3 is firstly natural air drying and then drying in an oven at 120°C.

A method for applying a double K-based coupling material for adsorption and catalysis in a _CO2 hydrogenation reaction. The double K-based coupling material is pressed into tablets, crushed and sieved, 1 g of the screened double K-based coupling material is weighed and loaded into a reaction tube with an inner diameter of 8 mm, loaded into a fixed bed, activated with a _H2 / _N2 mixed gas at 350°C and normal pressure for 4 h at a flow rate of 50 mL/min, cooled to 250°C, and a _CO2- containing gas is introduced for an adsorption reaction for 30 min; a mixed gas containing _H2 and _CO2 is introduced at the same temperature and 2 MPa pressure for a catalytic hydrogenation reaction for 30 min.

Furthermore, the sieve mesh number is 60-80 mesh; gas chromatography is used to perform online analysis on the components of the outlet gas to calculate the CO ₂ adsorption amount and CO ₂ conversion rate.

The present invention prepares a double K-based coupling material by doping lattice K and surface loading K ₂ CO ₃ on a Cu/CeZrO ₂ solid solution, wherein the surface-loaded K ₂ CO ₃ is a CO ₂ adsorption center, and K ₂ CO ₃ becomes KHCO ₃ after adsorbing CO _2. KHCO ₃ decomposes between 172°C and 350°C to release CO ₂ molecules, thereby promoting the catalytic hydrogenation reaction of CO ₂ in the same temperature window; the lattice-doped K can increase oxygen vacancies, enhance the activation of the material to CO ₂ molecules, and promote the formation of formate intermediates in the CO ₂ hydrogenation reaction and the further conversion of methanol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the CO2 adsorption and catalytic hydrogenation performance test results of the final products obtained in Examples 1-3 of the present invention and Comparative Example 1.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with specific embodiments and comparative examples. According to the following examples, the present invention can be better understood. However, it is easy for those skilled in the art to understand that the specific material proportions, process conditions and results described in the embodiments are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

Example 1

A method for preparing a double K-based coupling material comprises the following steps:

(1) Dissolve Ce(NO ₃ ) ₂ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O in deionized water, add citric acid solution dropwise at 90 ℃ for chelation, n(Ce ⁴⁺ +Zr ⁴⁺ ):n(citric acid)=1:1.2, stir until a viscous sol is formed, then transfer to a vacuum drying oven at 110 ℃ for 12 h, cool to room temperature and then calcine at 600 ℃ for 4 h to obtain a CeZrO ₂ solid solution.

(2) _KNO3 and Cu( _NO3 ) ₂ were dissolved in water to prepare a solution, and then the _CeZrO2 solid solution was impregnated for 6 hours. The mass ratio of K, Cu and _CeZrO2 solid solution was 0.02:0.05:1. Magnetic stirring was used throughout the impregnation process. After the impregnation, the solution was dried and then calcined at 500°C in _N2 atmosphere for 4 hours to obtain a lattice K-doped Cu/ _CeZrO2 solid solution.

(3) The above-mentioned lattice K-doped Cu/ _CeZrO2 solid solution is placed in a vacuum impregnator. After vacuum treatment, it is impregnated with an equal volume of _K2CO3 solution with _{a K2CO3} loading of 5 wt%. The material is then naturally shade-dried and dried in an oven at 120°C. After drying treatment, _K2CO3 is loaded on the surface of the _lattice K _- doped Cu/ _CeZrO2 solid solution, thereby obtaining a double K-based Cu/ _CeZrO2 solid solution coupling material.

Example 2

A method for preparing a double K-based coupling material comprises the following steps:

(1) Dissolve Ce(NO ₃ ) ₂ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O in deionized water, add citric acid solution dropwise at 90 ℃ for chelation, n(Ce ⁴⁺ +Zr ⁴⁺ ):n(citric acid)=1:1.2, stir until a viscous sol is formed, then transfer to a vacuum drying oven at 110 ℃ for 12 h, cool to room temperature and then calcine at 600 ℃ for 4 h to obtain a CeZrO ₂ solid solution.

(2) _KNO3 and Cu( _NO3 ) ₂ were dissolved in water to prepare a solution, and then the _CeZrO2 solid solution was impregnated for 6 hours. The mass ratio of K, Cu and _CeZrO2 solid solution was 0.02:0.05:1. Magnetic stirring was used throughout the impregnation process. After the impregnation, the solution was dried and then calcined at 500°C in _N2 atmosphere for 4 hours to obtain a lattice K-doped Cu/ _CeZrO2 solid solution.

(3) The above-mentioned lattice K-doped Cu/ _CeZrO2 solid solution is placed in a vacuum impregnator. After vacuum treatment, it is impregnated with an equal volume of _K2CO3 solution, and _{the K2CO3} loading amount is 10wt%. The material is then naturally shade-dried and dried in an oven at 120°C. After drying treatment, _K2CO3 is loaded on the surface of the _lattice K _- doped Cu/ _CeZrO2 solid solution, thereby preparing a double K-based Cu/ _CeZrO2 solid solution coupling material.

Example 3

A method for preparing a double K-based coupling material comprises the following steps:

(1) Dissolve Ce(NO ₃ ) ₂ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O in deionized water, add citric acid solution dropwise at 90 ℃ for chelation, n(Ce ⁴⁺ +Zr ⁴⁺ ):n(citric acid)=1:1.2, stir until a viscous sol is formed, then transfer to a vacuum drying oven at 110 ℃ for 12 h, cool to room temperature and then calcine at 600 ℃ for 4 h to obtain a CeZrO ₂ solid solution.

(2) _KNO3 and Cu( _NO3 ) ₂ were dissolved in water to prepare a solution, and then the _CeZrO2 solid solution was impregnated for 6 hours. The mass ratio of K, Cu and _CeZrO2 solid solution was 0.02:0.05:1. Magnetic stirring was used throughout the impregnation process. After the impregnation, the solution was dried and then calcined at 500°C in _N2 atmosphere for 4 hours to obtain a lattice K-doped Cu/ _CeZrO2 solid solution.

(3) The above-mentioned lattice K-doped Cu/ _CeZrO2 solid solution is placed in a vacuum impregnator. After vacuum treatment, it is impregnated with an equal volume of _K2CO3 solution with _{a K2CO3} loading of 15 wt%. The material is then naturally shade-dried and dried in an oven at 120°C. After drying treatment, _K2CO3 is loaded on the surface of the _lattice K _- doped Cu/ _CeZrO2 solid solution, thereby obtaining a double K-based Cu/ _CeZrO2 solid solution coupling material.

Comparative Example 1

(1) Dissolve Ce(NO ₃ ) ₂ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O in deionized water, add citric acid solution dropwise at 90 ℃ for chelation, n(Ce ⁴⁺ +Zr ⁴⁺ ):n(citric acid)=1:1.2, stir until a viscous sol is formed, then transfer to a vacuum drying oven at 110 ℃ for 12 h, cool to room temperature and then calcine at 600 ℃ for 4 h to obtain a CeZrO ₂ solid solution.

(2) A certain amount of Cu(NO ₃ ) ₂ was dissolved in water to prepare a solution, and then the CeZrO ₂ solid solution was impregnated for 6 hours. The mass ratio of Cu to CeZrO ₂ solid solution was 0.05:1. Magnetic stirring was used throughout the impregnation process. After the impregnation, it was dried and then calcined at 500 ℃ in N ₂ atmosphere for 4 hours to obtain Cu/CeZrO ₂ solid solution, marked as Cu ₅ /CeZrO ₂ .

The CO ₂ adsorption and catalytic hydrogenation performance tests of the final materials obtained in Examples 1-3 and Comparative Example 1 were carried out in a tubular fixed bed reactor with an inner diameter of 10 mm. The catalyst tablets were sieved and then loaded. The loading amount was 1 g. Before the performance test, they were activated in a gas with a volume ratio of H ₂ /N ₂ of 10% to 50% at 350°C and normal pressure for 4 hours. At 250°C, a mixed gas with a volume ratio of CO ₂ :N ₂ = 6:1 was introduced to test its CO ₂ adsorption performance. Then, a mixed gas with a volume ratio of H ₂ :CO ₂ :N ₂ = 72:24:4 was introduced under the same temperature conditions. The reaction pressure was set to 2 MPa to test the CO ₂ catalytic hydrogenation performance. The gas at the reactor outlet was analyzed by gas chromatography, and the component content in the tail gas was quantitatively analyzed by area normalization method.

The specific surface area and pore structure test results of the final materials prepared in Examples 1-3 and Comparative Example 1 are shown in Table 1.

Table 1 Specific surface area and pore structure test results of samples

As shown in Table 1, the specific surface area of Cu ₅ /CeZrO ₂ is 527 m ² /g, and the pore volume is 0.51 cm ³ /g; the specific surface area of the coupling material (K ₂ CO ₃ ) ₅ K ₂ Cu ₅ /CeZrO ₂ with Cu loading and double K base doping decreases to 491 m ² /g, and the pore volume decreases to 0.49 cm ³ /g. The specific surface area and pore volume of the coupling material continue to decrease with the increase of K ₂ CO ₃ loading, and the specific surface area and pore volume of (K ₂ CO ₃ ) ₁₅ K ₂ Cu ₅ /CeZrO ₂ are the smallest, which are 447 m ² /g and 0.43 cm ³ /g, respectively. The HK median pore diameters of the four samples are 1.2nm, 1.2nm, 1.4nm and 1.3nm, respectively, and the pore size distribution of the four samples belongs to the micropore range.

The content of each metal element in different catalysts was tested by inductively coupled plasma emission spectrometry (ICP), and the results are shown in Table 2. The actual content of K element is 0.57%-1.14% lower than expected, the actual content of Cu element is 0.16%-0.25% lower than the theoretical loading, and the actual content of K element is 0.27%-0.41% lower than the theoretical loading. The actual content is highly close to the theoretical loading, and the preparation method of the present invention can complete the precise loading and doping of active components.

Table 2 Analysis of metal element content of samples

The test results of CO ₂ adsorption and catalytic hydrogenation performance of the final products obtained in Examples 1-3 and Comparative Example 1 are shown in FIG1 , where X(CO ₂ ) represents the carbon dioxide conversion rate, S(CH ₃ OH) represents the methanol selectivity, and the reaction conditions are: P=2MPa, T=250°C, H ₂ /CO ₂ =3/1, GHSV=12,000mL/(g·h). As can be seen from FIG1 , the CO ₂ adsorption amount, CO ₂ conversion rate and methanol selectivity of the comparative example Cu ₅ / CeZrO ₂ are 13 mg/g, 3.6% and 63.4%, respectively. After Cu ₅ /CeZrO ₂ is doped with lattice K and surface loaded with K ₂ CO ₃ , the CO ₂ adsorption amount, CO ₂ conversion rate and methanol selectivity of the double K-based coupling material (K ₂ CO ₃ ) ₅ K ₂ Cu ₅ /CeZrO ₂ are improved. The CO ₂ adsorption amount increases with the increase of K ₂ CO ₃ surface loading, while the CO ₂ conversion rate and methanol selectivity first increase and then decrease with the increase of K ₂ CO ₃ surface loading. The double K-based coupling material (K ₂ CO ₃ ) ₁₀ K ₂ Cu ₅ /CeZrO ₂ has the best CO ₂ conversion rate and methanol selectivity, which are 4.3% and 74.7%, respectively. This is because the surface-loaded K ₂ CO ₃ acts as an adsorption aid, which strengthens the adsorption of CO ₂ by the catalyst, providing conditions for the subsequent catalytic hydrogenation of CO ₂ ; the lattice-doped K species can increase oxygen vacancies, strengthen the activation of the catalyst for CO ₂ , and promote the formation of formate intermediates and the further conversion of methanol.

Claims (7)

1. A double-K-based coupling material is characterized in that K ₂CO₃ is loaded on the surface of lattice K-doped Cu/CeZrO ₂, and the loading amount of K ₂CO₃ is 5-15 wt%.

2. A method of preparing the double K-based coupling material of claim 1, comprising the steps of:

Step 1, ce (NO ₃)₂·6H₂ O and Zr (NO ₃)₄·5H₂ O are dissolved in deionized water, citric acid solution is added dropwise at 90 ℃ for chelation, the mixture is stirred to be in a viscous sol state and then is transferred to a vacuum drying oven at 110 ℃ for drying 12 h, and after cooling to room temperature, the mixture is baked at 600 ℃ for 4 h to obtain CeZrO ₂ solid solution;

Step 2, dissolving KNO ₃ and Cu (NO ₃)₂ in water to prepare solution A, immersing CeZrO ₂ solid solution in the solution A for 6 hours, magnetically stirring the immersion process, drying, and calcining for 4 hours at 500 ℃ in an N ₂ atmosphere to obtain a lattice K doped Cu/CeZrO ₂ solid solution;

And 3, placing the Cu/CeZrO ₂ solid solution doped with the lattice K prepared in the step 2 into a vacuum impregnator, performing vacuum pumping treatment, impregnating by adopting an equal volume of K ₂CO₃ solution, and performing drying treatment to obtain a final product.

3. The method for preparing a double-K-based coupling material according to claim 2, wherein Ce (NO ₃)₂·6H₂ O and Zr (molar ratio of NO ₃)₄·5H₂ O to citric acid is 1:1.2) in step 1.

4. The method for preparing a double-K-based coupling material according to claim 2, wherein the mass ratio of K, cu to CeZrO ₂ solid solution in step 2 is 0.02:0.05:1.

5. The method for preparing double-K-based coupling material according to claim 2, wherein the drying treatment in step 3 is natural drying in the shade and then drying in an oven at 120 ℃.

6. An application method of the double-K-based coupling material according to claim 1, which is used for adsorption and catalysis in CO ₂ hydrogenation reaction, wherein the double-K-based coupling material is crushed and sieved after being pressed into tablets, 1g of the screened double-K-based coupling material is weighed and loaded into a reaction tube with the inner diameter of 8mm, the reaction tube is filled into a fixed bed, H ₂/N₂ mixed gas is used for activation for 4 hours under the condition of 350 ℃ and normal pressure, the flow rate is 50mL/min, the temperature is reduced to 250 ℃, and CO ₂ -containing gas is introduced for adsorption reaction for 30-60min; introducing mixed gas containing H ₂ and CO ₂ under the same temperature and 2MPa pressure to perform catalytic hydrogenation reaction for 30-60min.

7. The method of using a double K-based coupling material according to claim 6, wherein the number of pass through the screen is 60-80 mesh; and (3) carrying out on-line analysis on the components of the outlet gas by adopting gas chromatography, and calculating the adsorption quantity of CO ₂ and the conversion rate of CO ₂.