Pillared graphene oxide solid acid catalyst as well as preparation method and application thereof
By introducing silica and alumina column support between graphene oxide layers, an efficient column-type graphene oxide solid acid catalyst was prepared, which solved the problems of low efficiency and many by-products of traditional catalysts in the cyclohexanol dehydration reaction, achieving high conversion and selectivity, and is suitable for industrial applications.
Patent Information
- Application Number
- CN202510633038.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-16
- Publication Date
- 2025-08-15
AI Technical Summary
Traditional catalysts are inefficient in cyclohexanol dehydration reaction, prone to carbon accumulation and by-products, making it difficult to meet industrial needs.
Silica dioxide and alumina column support are introduced between the graphene oxide layers by freezing and thawing method to form a column-type graphene oxide solid acid catalyst, and SiO2-Al2O3 column support is generated through a double hydrolysis reaction, which increases the specific surface area and pore volume, and can regulate acidity.
At 180°C, the conversion rate of cyclohexanol reaches 99.51%, and the selectivity of cyclohexene reaches 99.09%. The catalyst is simple to prepare and low cost, and is suitable for industrial production.
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Figure CN120479407A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a pillared graphene oxide solid acid catalyst, a preparation method thereof, and application of the catalyst in a cyclohexanol dehydration reaction. Background Art
[0002] The cyclohexanol dehydration reaction is a key process for preparing cyclohexene, an important chemical intermediate, and has broad applications in pharmaceuticals, pesticides, and fine chemicals (The Journal of Chemical Physics. 2024, 160: 231-101). However, traditional cyclohexanol dehydration catalysts, such as zeolite molecular sieves and alumina, suffer from low reaction efficiency at high temperatures, prone to carbon deposition, and high levels of byproducts (Energy Science & Policy. 2023, 1.2: 1-10).
[0003] Graphene oxide, due to its unique two-dimensional structure and rich surface functional groups, is an ideal support for novel solid acid catalysts. Introducing metal oxides between graphene oxide layers through a freeze-thaw method effectively modulates the catalyst's pore structure and acidic site distribution, significantly improving mass transfer efficiency and catalytic activity (Nature Communications. 2023, 4.1: 1373). Summary of the Invention
[0004] The purpose of the present invention is to provide a pillared graphene oxide solid acid catalyst.
[0005] Another object of the present invention is to provide a method for preparing the above catalyst with low cost and simple process.
[0006] Another object of the present invention is to provide the use of the above catalyst in the dehydration reaction of cyclohexanol.
[0007] The above objectives of the present invention are achieved through the following technical solutions.
[0008] The present invention provides a method for preparing a pillared graphene oxide solid acid catalyst, the steps of which are as follows:
[0009] (1) mixing graphene oxide and water at a mass ratio of 1:2500, and stirring at room temperature for 2 to 4 hours to obtain a fully hydrated and highly dispersed graphene oxide aqueous solution;
[0010] (2) freezing an aluminum salt solution having a concentration of 0.021 to 0.064 mol / L into ice cubes, wherein the mass ratio of the aluminum salt to the graphene oxide in step (1) is 0.31 to 0.84:100;
[0011] (3) freezing a silicate solution having a concentration of 0.032 to 0.096 mol / L into ice cubes, wherein the mass ratio of the silicate to the aluminum salt in step (2) is 84.79 to 196.76:100;
[0012] (4) adding the aluminum salt solution ice cubes obtained in step (2) and the silicate solution ice cubes obtained in step (3) to 100 mL of the graphene oxide aqueous solution obtained in step (1) in a manner of melting and releasing at room temperature, stirring while melting until the ice cubes are completely melted, centrifuging and washing three times, and drying at 80-100° C. for 10-12 hours to obtain a pillared graphene oxide solid acid catalyst precursor;
[0013] (5) calcining the pillared graphene oxide solid acid catalyst precursor obtained in step (4) in a hydrogen atmosphere, and then cooling to room temperature in a hydrogen atmosphere to obtain a pillared graphene oxide solid acid catalyst.
[0014] Furthermore, the aluminum salt in step (2) is any one of aluminum chloride hexahydrate, aluminum nitrate nonahydrate and aluminum sulfate 18hydrate.
[0015] Furthermore, the aluminum salt in step (2) is aluminum nitrate nonahydrate.
[0016] Furthermore, the silicate in step (3) is any one of sodium silicate nonahydrate and potassium silicate nonahydrate.
[0017] Furthermore, the silicate in step (3) is sodium silicate nonahydrate.
[0018] Furthermore, the calcination in a hydrogen atmosphere in step (5) refers to calcination in a hydrogen atmosphere at 200-550° C. for 3 hours.
[0019] The pillared graphene oxide solid acid catalyst prepared by the above method has graphene oxide as a carrier, and silicon dioxide and aluminum oxide as pillars and acidic components.
[0020] The pillared graphene oxide solid acid catalyst prepared by the above method can be used in the dehydration reaction of cyclohexanol.
[0021] Furthermore, the dehydration product of cyclohexanol is cyclohexene.
[0022] The cyclohexanol dehydration performance of the pillared graphene oxide solid acid catalyst of the present invention was evaluated. The cyclohexanol dehydration reaction was conducted in a 60 mL batch autoclave. The specific steps and conditions were as follows: 0.5 mL of cyclohexanol, 20 mL of n-dodecane, and 0.2 g of the pillared graphene oxide solid acid catalyst were added to the autoclave. After stirring, 2 MPa of nitrogen was introduced into the autoclave as a protective atmosphere. The temperature was raised to 180°C with continuous stirring and the reaction was allowed to proceed for 1 hour. After completion of the reaction, the dehydration product was analyzed using an Agilent 8806 gas chromatograph using the internal standard method.
[0023] Compared with the prior art, the present invention has the following technical effects:
[0024] (1) Graphene oxide itself has almost no acidity. In the present invention, the graphene oxide is highly dispersed in water and peeled off into graphene oxide nanosheets by freeze-thaw double hydrolysis method, and SiO3 in silicate (such as NaSiO3) is used to form graphene oxide nanosheets. 2- and Al in aluminum salts (such as Al(NO3)3) 3+ A double hydrolysis reaction occurs to generate H2SiO3 and Al(OH)3 precipitates to form a pillared body, and H2SiO3 and Al(OH)3 are then converted into SiO2-Al2O3 pillared graphene oxide solid acid through thermal decomposition.
[0025] (2) The introduction of SiO2-Al2O3 pillared graphene oxide solid acid greatly increases its specific surface area and pore volume, reaching a maximum of 793.16 m 2 / g and 1.18cm 3 / g, and its acid strength and acidity can be adjusted by changing the thermal decomposition temperature (200-550°C). This large specific surface area, large pore volume and adjustable acidity greatly broaden the application field of this solid acid.
[0026] (3) The pillared graphene oxide solid acid catalyst of the present invention has excellent cyclohexanol dehydration performance. Under the reaction conditions of 180°C, the cyclohexanol conversion rate reaches 99.51% and the cyclohexene selectivity reaches 99.09%.
[0027] (4) The catalyst preparation method of the present invention is simple and low-cost, and is very suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 This is the XRD pattern of the SiO2-Al2O3 / GO-5 catalyst of the present invention.
[0029] Figure 2 This is the nitrogen physical adsorption isotherm diagram of the SiO2-Al2O3 / GO-3 catalyst of the present invention.
[0030] Figure 3This is a graph showing the relationship between the acid amount and acid strength of the pillared graphene oxide solid acid catalyst calcined at 200° C. to 400° C. as measured by the Hammett indicator method.
[0031] Figure 4 This is the NH3-TPD diagram of the SiO2-Al2O3 / GO-5 catalyst of the present invention. DETAILED DESCRIPTION
[0032] In order to further illustrate the present invention, the following examples are given, but they do not limit the scope of the invention defined by the claims.
[0033] 1. Preparation of pillared graphene oxide solid acid catalyst
[0034] Example 1
[0035] 1.34 g of a 3% graphene oxide solution was weighed, diluted with 100 mL of water, and stirred thoroughly on a magnetic stirrer for 2 hours to produce a uniform and stable graphene oxide aqueous solution. 20 mL of a 0.064 mol / L aluminum chloride hexahydrate solution and 60 mL of a 0.032 mol / L sodium silicate nonahydrate solution were frozen into ice cubes, then slowly melted at room temperature and added dropwise to the stirred graphene oxide. After the ice cubes were completely melted, the mixture was centrifuged and washed three times. The resulting solid product was dried at 100°C for 10 hours and then ground into a powder. The resulting powder was calcined at 200°C in a hydrogen atmosphere for 3 hours and cooled to room temperature to obtain a pillared graphene oxide solid acid catalyst, represented by SiO2-Al2O3 / GO-1.
[0036] Example 2
[0037] 1.34g of a 3% graphene oxide solution was weighed, diluted with 100mL of water, and stirred thoroughly on a magnetic stirrer for 3 hours to produce a uniform and stable graphene oxide aqueous solution. 40mL of a 0.032mol / L aluminum nitrate nonahydrate solution and 40mL of a 0.048mol / L sodium silicate nonahydrate solution were frozen into ice cubes, then slowly melted at room temperature and added dropwise to the stirred graphene oxide. After the ice cubes were completely melted, the mixture was centrifuged and washed three times. The resulting solid product was dried at 90°C for 11 hours and then ground into a powder. The resulting powder was calcined at 300°C in a hydrogen atmosphere for 3 hours and cooled to room temperature to obtain a pillared graphene oxide solid acid catalyst, represented by SiO2-Al2O3 / GO-2.
[0038] Example 3
[0039] 1.34g of a 3% graphene oxide solution was weighed, diluted with 100mL of water, and stirred thoroughly on a magnetic stirrer for 4 hours to produce a uniform and stable graphene oxide aqueous solution. 60mL of a 0.021mol / L aluminum sulfate 18-hydrate solution and 20mL of a 0.096mol / L sodium silicate nonahydrate solution were frozen into ice cubes, then slowly melted at room temperature and added dropwise to the stirred graphene oxide. After the ice cubes were completely melted, the mixture was centrifuged and washed three times. The resulting solid product was dried at 80°C for 12 hours and then ground into a powder. The resulting powder was calcined at 400°C in a hydrogen atmosphere for 3 hours. After cooling to room temperature, the pillared graphene oxide solid acid catalyst, represented by SiO2-Al2O3 / GO-3, was obtained.
[0040] Example 4
[0041] 1.34g of a 3% graphene oxide solution was weighed, diluted with 100mL of water, and stirred thoroughly on a magnetic stirrer for 3 hours to produce a uniform and stable graphene oxide aqueous solution. 40mL of a 0.032mol / L aluminum chloride hexahydrate solution and 40mL of a 0.048mol / L potassium silicate nonahydrate solution were frozen into ice cubes, then slowly melted at room temperature and added dropwise to the stirred graphene oxide. After the ice cubes were completely melted, the mixture was centrifuged and washed three times. The resulting solid product was dried at 80°C for 12 hours and then ground into a powder. The resulting powder was calcined at 500°C in a hydrogen atmosphere for 3 hours and cooled to room temperature to obtain a pillared graphene oxide solid acid catalyst, represented by SiO2-Al2O3 / GO-4.
[0042] Example 5
[0043] 1.34g of a 3% graphene oxide solution was weighed, diluted with 100mL of water, and stirred thoroughly on a magnetic stirrer for 3 hours to produce a uniform and stable graphene oxide aqueous solution. 40mL of a 0.032mol / L aluminum nitrate nonahydrate solution and 40mL of a 0.048mol / L potassium silicate nonahydrate solution were frozen into ice cubes, then slowly melted at room temperature and added dropwise to the stirred graphene oxide. After the ice cubes were completely melted, the mixture was centrifuged and washed three times. The resulting solid product was dried at 80°C for 12 hours and then ground into a powder. The resulting powder was calcined at 550°C in a hydrogen atmosphere for 3 hours and cooled to room temperature to obtain a pillared graphene oxide solid acid catalyst, represented by SiO2-Al2O3 / GO-5.
[0044] The SiO2-Al2O3 / GO-5 catalyst of the present invention was characterized by XRD. The XRD test was carried out on a Japanese Rigaku Ultima IV X-ray diffractometer. The results are as follows: Figure 1 As shown. It can be seen from the figure that the catalyst has a peak packet at 2θ=24°, which is attributed to the (002) characteristic peak of GO (Carbon Trends.2025,3:100499.). Because SiO2 is an amorphous phase (2θ≈22°), it overlaps with the GO (002) peak (Journal ofNon-Crystalline Solids.2020,531:119841.). The characteristic diffraction peak of Al2O3 was observed at 2θ=43°. Because the particles are small and highly dispersed, the peak shape is smaller. The above analysis shows that a pillared graphene oxide solid acid catalyst containing silica and alumina was successfully prepared.
[0045] The SiO2-Al2O3 / GO-3 catalyst in the present invention was subjected to nitrogen physical adsorption test on the ASAP 2420 physical adsorption instrument of Micromeritics. The results are as follows: Figure 2 As shown. Figure 2 As shown in Figure 2, when calcined at 400 °C, the specific surface area and pore volume of SiO2-Al2O3 / GO-3 reached as high as 793.16 m 2 / g and 1.18cm 3 / g, respectively graphene oxide (10.18m 2 / g and 0.007cm 3 The above analysis shows that at this calcination temperature, silica and alumina can not only maintain structural stability and effectively support the interlayer structure of graphene oxide, but also avoid the problem of pore clogging caused by excessive particle agglomeration.
[0046] The present invention uses the Hammett indicator method to evaluate the relationship between the acid strength and acid amount of the pillared graphene oxide solid acid catalyst calcined at low temperature (200℃~400℃). Figure 3 As shown. Figure 3 It can be seen that the total acid content of the SiO2-Al2O3 / GO catalyst continues to increase as the calcination temperature increases from 200°C to 400°C. The acid content in the weak acid region (6.8-3.3) decreases slightly, shifting toward medium-strong acidity. The acid content in the medium-strong acid region (3.3--3.0) gradually increases, but the system contains almost no strong acid sites (-3.0--8.3). The above analysis shows that the acidity of the catalyst can be controlled by controlling the calcination temperature.
[0047] The present invention uses the NH3-TPD method to test the relationship between the acid strength and acid amount of SiO2-Al2O3 / GO-5 and graphene oxide on a CHEMBET-300 chemical adsorption instrument from Quantachrome. The results are as follows: Figure 4 As shown. Figure 4 As can be seen, graphene oxide has almost no desorption peaks, indicating that it is not inherently acidic. SiO2-Al2O3 / GO-5 exhibits a distinct desorption peak between 100°C and 500°C, indicating the presence of weakly acidic (less than 200°C), moderately acidic (200-400°C), and strongly acidic (greater than 400°C) sites. This analysis suggests that the introduction of silica and alumina significantly enhances the acidity of the catalyst.
[0048] Comparative Example 1
[0049] A single-component alumina-pillared graphene oxide solid acid catalyst, represented by Al2O3 / GO, was prepared in the same manner as in Example 2, except that 40 mL of a 0.032 mol / L aluminum nitrate nonahydrate aqueous solution was frozen into ice cubes, slowly melted at room temperature, and then dropwise added to the continuously stirred graphene oxide. 0.1535 g of sodium hydroxide (3.84 mmol) was then added and stirred for 1 hour.
[0050] 2. Activity Evaluation of the Pillared Graphene Oxide Solid Acid Catalyst of the Present Invention
[0051] Example 6
[0052] Evaluation of Cyclohexanol Dehydration Activity of Pillared Graphene Oxide Solid Acid Catalyst SiO2-Al2O3 / GO-1: Cyclohexanol dehydration reactions using the SiO2-Al2O3 / GO-1 catalyst were conducted in a 60 mL batch autoclave. The following steps and conditions were used: 0.5 mL of cyclohexanol, 20 mL of n-dodecane, and 0.2 g of the SiO2-Al2O3 / GO-1 catalyst were added to the autoclave. After stirring, 2 MPa of nitrogen was introduced into the autoclave as a protective atmosphere. The reaction was heated to 180°C with continuous stirring and allowed to react for 1 hour. After completion of the reaction, the dehydration products were analyzed using an Agilent 8806 gas chromatograph using the internal standard method.
[0053] The activity evaluation of cyclohexanol dehydration reaction of Al2O3 / GO, SiO2-Al2O3 / GO-2, SiO2-Al2O3 / GO-3, SiO2-Al2O3 / GO-4 and SiO2-Al2O3 / GO-5 catalysts was the same as that of SiO2-Al2O3 / GO-1 catalyst, and the reaction results are shown in Table 1.
[0054] Table 1 Cyclohexanol dehydration performance of pillared graphene oxide solid acid catalysts with different calcination temperatures at 180 °C
[0055]
[0056]
[0057] Reaction conditions: 0.2 g catalyst, 4.8 mmol cyclohexanol, 20 ml n-dodecane, 2 MPaN2, 180°C, 1 hour, 1800 r / min
[0058] The results in Table 1 show that the pillared graphene oxide solid acid catalyst prepared in this invention exhibits excellent cyclohexanol dehydration performance. According to the reaction results, at 180°C, the cyclohexanol conversion rate of the Al2O3 / GO catalyst was 10.52%. In comparison, the SiO2-Al2O / GO-1 catalyst increased by 21.48%, the SiO2-Al2O / GO-2 catalyst increased by 845.91%, the SiO2-Al2O / GO-3 catalyst increased by 846.48%, the SiO2-Al2O / GO-4 catalyst increased by 71.10%, and the SiO2-Al2O / GO-5 catalyst increased by 194.49%. The pillared graphene oxide solid acid catalysts prepared in this invention at different calcination temperatures all showed higher activity than the Al2O3 / GO catalyst. The SiO2-Al2O3 / GO-2 catalyst exhibited the best cyclohexanol dehydration performance, achieving a conversion of 99.51% while maintaining a cyclohexene selectivity of 99.09%.
Claims
1. A method for preparing a pillared graphene oxide solid acid catalyst, characterized in that The steps include: (1) mixing graphene oxide and water at a mass ratio of 1:2500, and stirring at room temperature for 2 to 4 hours to obtain a fully hydrated and highly dispersed graphene oxide aqueous solution; (2) freezing an aluminum salt solution having a concentration of 0.021 to 0.064 mol / L into ice cubes, wherein the mass ratio of the aluminum salt to the graphene oxide in step (1) is 0.31 to 0.84:100; (3) freezing a silicate solution having a concentration of 0.032 to 0.096 mol / L into ice cubes, wherein the mass ratio of the silicate to the aluminum salt in step (2) is 84.79 to 196.76:100; (4) adding the aluminum salt solution ice cubes obtained in step (2) and the silicate solution ice cubes obtained in step (3) to the graphene oxide aqueous solution obtained in step (1) in a manner such that they melt and release at room temperature, stirring and reacting while melting until the ice cubes are completely melted, washing by centrifugation, and drying at 80-100° C. for 10-12 hours to obtain a pillared graphene oxide solid acid catalyst precursor; (5) calcining the pillared graphene oxide solid acid catalyst precursor obtained in step (4) in a hydrogen atmosphere, and then cooling to room temperature in a hydrogen atmosphere to obtain a pillared graphene oxide solid acid catalyst.
2. The preparation method of the pillared graphene oxide solid acid catalyst according to claim 1, wherein The aluminum salt in step (2) is any one of aluminum nitrate nonahydrate, aluminum chloride hexahydrate and aluminum sulfate 18hydrate.
3. The preparation method of the pillared graphene oxide solid acid catalyst as claimed in claim 2, wherein The aluminum salt in step (2) is aluminum nitrate nonahydrate.
4. The preparation method of the pillared graphene oxide solid acid catalyst according to claim 1, wherein The silicate in step (3) is any one of sodium silicate nonahydrate and potassium silicate nonahydrate.
5. The preparation method of the pillared graphene oxide solid acid catalyst as claimed in claim 4, wherein The silicate in step (3) is sodium silicate nonahydrate.
6. The preparation method of the pillared graphene oxide solid acid catalyst according to claim 1, wherein The calcination in a hydrogen atmosphere in step (5) refers to calcination in a hydrogen atmosphere at 200-550° C. for 3 hours.
7. A pillared graphene oxide solid acid catalyst prepared by the method according to claim 1.
8. Use of the pillared graphene oxide solid acid catalyst as claimed in claim 7 in the dehydration reaction of cyclohexanol.
9. Use of the pillared graphene oxide solid acid catalyst according to claim 8 in the dehydration reaction of cyclohexanol, characterized in that The dehydration product of cyclohexanol is cyclohexene.