Gamma-alumina nanorods or sheets and synthesis and applications thereof

Abstract

The application discloses a synthesis method for simultaneously regulating size and morphology of gamma-Al2O3 nano materials, and mainly relates to micro-morphology transformation of gamma-Al2O3 nanoparticles from nanorods to nanosheets by changing solution pH value. The method uses aluminum nitrate nonahydrate as an aluminum source, benzene sulfonic acid as a surfactant, adjusts the pH value of the solution through ammonia water, and adopts a hydrothermal method to synthesize gamma-AlOOH nanorods and nanosheets; then, gamma-Al2O3 nanorods and nanosheets are obtained by high-temperature calcination. The prepared gamma-Al2O3 nano materials have excellent catalytic performance in an ethanol dehydration reaction, and show obvious morphology effect.

Description

Technical Field

[0001] This invention relates to a method for preparing γ-Al2O3 nanorods.

[0002] The present invention also relates to a method for preparing γ-Al2O3 nanosheets.

[0003] This invention also relates to a method for morphology control of γ-AlOOH nanomaterials.

[0004] This invention also relates to the catalytic application of the above-mentioned γ-Al2O3 nanomaterials. Background Technology

[0005] As a typical solid acid catalyst, γ-Al₂O₃ is widely used in important industrial processes such as Krauss sulfur production, alcohol dehydration to olefins / ethers, and olefin isomerization. The bulk structure of γ-Al₂O₃ with a spinel structure contains Al₂O₃. 3+ When ions occupy tetrahedral or octahedral sites, their surfaces expose tri-, tetra-, penta-, or hexa-coordinated Al atoms. 3+ Species and three- and four-coordinated O 2- Anions. Different morphologies of γ-Al₂O₃ expose different crystal planes, characteristic of Al. 3+ and O 2- The surface occupancy of species also changes, thus affecting the catalytic activity of γ-Al2O3 nanomaterials. For example, in the ethanol dehydration reaction, the conversion rate of ethylene decreases in the order of γ-Al2O3 nanorods ({100} crystal facets) > γ-Al2O3 hexagonal nanosheets ({100} crystal facets) > γ-Al2O3 rhombic nanosheets ({110} or {111} crystal facets), and the activity is directly proportional to the {100} area exposed by the γ-Al2O3 nanoparticles (J. Catal. 345 (2017) 135-148). Further studies have found that when the proportion of {100} facets in γ-Al2O3 nanosheets increases to 23%, the ethylene yield increases linearly from 36.5% to 54.6%, indicating that the {100} crystal facets of γ-Al2O3 are the active sites for ethylene formation (Appl. Catal. A 556 (2018) 121-128). γ-Al₂O₃ nanotubes with exposed {111} faces significantly improved the yield of C₂H₄ in the ethanol dehydration reaction at 530 K–700 K (ACS Catal. 7 (2017) 4083–4092). Related theoretical calculations indicate that the polar {111} faces with higher surface energy generate a greater density of acidic hydroxyl groups and Lewis acidic centers, which is beneficial for ethanol conversion.

[0006] γ-Al₂O₃ nanomaterials are generally obtained by dehydrating γ-AlOOH (boehmite) at 773K-873K. Therefore, the morphology of the γ-AlOOH precursor determines the size and morphology of the γ-Al₂O₃ nanomaterials. Numerous studies have shown that the pH of the solution significantly affects the growth rate of the {100} crystal facets of γ-AlOOH, thus determining the final morphology of the γ-AlOOH nanoparticles (CrystEngComm 11(2009)1338-1342). However, due to the lack of effective control over Al… 3+ The hydrolysis rate of ions in aqueous solution typically results in γ-AlOOH nanoparticles with sizes ranging from several hundred nanometers to several micrometers. Therefore, the simultaneous controllable synthesis of both the size and morphology of γ-Al₂O₃ nanomaterials remains a research challenge in the field of nanomaterials. Synthesizing γ-Al₂O₃ nanomaterials with similar sizes but different morphologies under similar conditions will help elucidate the structure-activity relationship of catalysts. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing γ-Al2O3 nanorods.

[0008] Another objective of this invention is to provide a method for preparing γ-Al2O3 nanosheets.

[0009] Another objective of this invention is to adjust the pH of the hydrothermal reaction precursor solution using ammonia water, thereby regulating the size and morphology of γ-AlOOH nanomaterials.

[0010] Another object of the present invention is to provide the application of the above-mentioned γ-Al2O3 nanomaterials in the ethanol dehydration reaction.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing γ-Al2O3 nanorods, the process steps of which are as follows:

[0013] (1) Dissolve 1.40-2.80g benzenesulfonic acid and 16.00-20.00g aluminum nitrate nonahydrate in 80mL of water at room temperature to form a homogeneous aqueous solution;

[0014] (2) Add ammonia water (concentration 25-28%) dropwise to the solution prepared in (1) under stirring conditions until the pH reaches 7.0 and stabilizes;

[0015] (3) Take 60-80 mL of the solution from (2) and place it in a 100 mL capacity hydrothermal reactor. React the solution at 150-200℃ for 24-48 h.

[0016] (4) The product of the hydrothermal reaction in (3) was washed by centrifugation with water and ethanol multiple times and dried at 80°C to obtain γ-AlOOH nanorods.

[0017] (5) The γ-AlOOH nanorod product from (4) was calcined at 600℃ for 4-6h at a heating rate of 5℃ / min to obtain γ-Al2O3 nanorods.

[0018] The preferred dosage of benzenesulfonic acid is 1.40-2.80g.

[0019] The preferred dosage of aluminum nitrate nonahydrate is 16.00-20.00g.

[0020] The preferred ammonia concentration is 25-28%.

[0021] The preferred amount of solution used for the hydrothermal reaction is 60-80 mL.

[0022] The preferred hydrothermal reaction temperature is 150-200℃.

[0023] The preferred hydrothermal reaction time is 24-48 hours.

[0024] The preferred roasting time is 4-6 hours.

[0025] A method for preparing γ-Al₂O₃ nanosheets, the process steps of which are as follows:

[0026] (1) Dissolve 1.40-2.80g benzenesulfonic acid and 16.00-20.00g aluminum nitrate nonahydrate in 80mL of water at room temperature to form a homogeneous aqueous solution;

[0027] (2) Add ammonia water (concentration 25-28%) dropwise to the solution prepared in (1) under stirring conditions until the pH reaches 9.0 and stabilizes;

[0028] (3) Take 60-80 mL of the solution from (2) and place it in a 100 mL capacity hydrothermal reactor. React the solution at 150-200℃ for 24-48 h.

[0029] (4) The product of the hydrothermal reaction in (3) was washed by centrifugation with water and ethanol multiple times and dried at 80°C to obtain γ-AlOOH nanosheets.

[0030] (5) The γ-AlOOH nanosheet product from (4) was calcined at 600℃ for 4-6h at a heating rate of 5℃ / min to obtain γ-Al2O3 nanosheets.

[0031] The preferred dosage of benzenesulfonic acid is 1.40-2.80g.

[0032] The preferred dosage of aluminum nitrate nonahydrate is 16.00-20.00g.

[0033] The preferred ammonia concentration is 25-28%.

[0034] The preferred amount of solution used for the hydrothermal reaction is 60-80 mL.

[0035] The preferred hydrothermal reaction temperature is 150-200℃.

[0036] The preferred hydrothermal reaction time is 24-48 hours.

[0037] The preferred roasting time is 4-6 hours.

[0038] A method for controlling the morphology of γ-AlOOH nanomaterials, the synthesis process of which is as follows: 1.40-2.80 g of benzenesulfonic acid and 16.00-20.00 g of aluminum nitrate nonahydrate are dissolved in 80 mL of aqueous solution. The pH value of the solution is adjusted (range from 6.0 to 8.0) by slowly adding ammonia water (concentration 25-28%) at room temperature. Then, 60-80 mL of the mixture is placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 150-200 °C for 24-48 h. The product is washed repeatedly by centrifugation with water and ethanol and dried at 80 °C to obtain... To obtain γ-AlOOH nanorods; or, using 1.40-2.80 g benzenesulfonic acid and 16.00-20.00 g aluminum nitrate nonahydrate dissolved in 80 mL of aqueous solution, the pH of the solution (range from 8.1-9.5) is adjusted by slowly adding ammonia (concentration 25-28%) at room temperature. Then, 60-80 mL of this solution is placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 150-200 °C for 24-48 h. The product is washed repeatedly by centrifugation with water and ethanol and dried at 80 °C to obtain γ-AlOOH nanosheets.

[0039] The preferred amount of benzenesulfonic acid in the γ-AlOOH nanorod precursor solution is 1.40-2.80 g, the preferred amount of aluminum nitrate nonahydrate is 16.00-20.00 g, and the preferred concentration of ammonia water used to adjust the pH is 25-28%.

[0040] The preferred pH value of the γ-AlOOH nanorods before hydrothermal reaction is 6.0-8.0, the preferred reaction time is 24-48 h, and the preferred temperature is 150-200℃.

[0041] The preferred amount of benzenesulfonic acid in the γ-AlOOH nanosheet precursor solution is 1.40-2.80 g, the preferred amount of aluminum nitrate nonahydrate is 16.00-20.00 g, and the preferred concentration of ammonia water used to adjust the pH is 25-28%.

[0042] The preferred pH value of the γ-AlOOH nanosheets before hydrothermal reaction is 8.1-9.5, the preferred reaction time is 24-48 h, and the preferred temperature is 150-200℃.

[0043] The γ-AlOOH precursor was characterized using a Hitachi HT7700 transmission electron microscope and a Rigaku D / MAX-2500 / PC X-ray powder diffractometer. The characterization results are shown in [Figure number missing]. Figure 5-10 All diffraction peaks correspond to γ-AlOOH (JCPDS#21-1307), with morphologies of nanorods and nanosheets, respectively. The size and morphology of the γ-Al₂O₃ nanorods and nanosheets were observed using a Hitachi HT7700 transmission electron microscope and XRD, and the test results are as follows: Figure 1-4 As shown, γ-AlOOH was calcined to obtain γ-Al2O3. The prepared particles have regular shape and uniform size. All diffraction peaks correspond to γ-Al2O3 (JCPDS#29-0063). The average length of the γ-Al2O3 nanorods is 119 nm and the diameter is 8 nm. The average size of the nanosheets is 32 nm and the thickness is 5 nm.

[0044] The application of γ-Al2O3 nanorods in an ethanol dehydration reaction includes the following steps:

[0045] (1) Using the γ-Al2O3 nanorods, take 50mg (40-60 mesh), purge with He at 30mL / min for 1h at 400℃, cool to room temperature, then heat to 250℃ and purge with ethanol / He reaction raw material gas at a volume concentration of 1.55% at a flow rate of 60mL / min for 15h.

[0046] (2) Samples were taken every 25 minutes after the reaction started, and the composition of the reaction products was analyzed online by gas chromatography.

[0047] The preferred dosage of the γ-Al2O3 nanorods is 50 mg, with a mesh size of 40-60 mesh.

[0048] The preferred He purging temperature is 400℃, and the preferred flow rate is 30mL / min.

[0049] The preferred volume concentration of the reaction feed gas is 1.55% ethanol / He, the preferred flow rate is 60 mL / min, and the preferred reaction temperature is 250 °C.

[0050] The application of γ-Al2O3 nanosheets in an ethanol dehydration reaction includes the following steps:

[0051] (1) Using the γ-Al2O3 nanosheets, take 50mg (40-60 mesh), purge with He at 30mL / min for 1h at 400℃, cool to room temperature, then heat to 250℃ and purge with ethanol / He reaction raw material gas with a volume concentration of 1.55% at a flow rate of 60mL / min for 15h.

[0052] (2) Samples were taken every 25 minutes after the reaction started, and the composition of the reaction products was analyzed online by gas chromatography.

[0053] The amount of γ-Al2O3 nanosheets used is 50mg, and the mesh size is preferably 40-60 mesh.

[0054] The preferred He purging temperature is 400℃, and the preferred flow rate is 30mL / min.

[0055] The preferred volume concentration of the reaction feed gas is 1.55% ethanol / He, the preferred flow rate is 60 mL / min, and the preferred reaction temperature is 250 °C.

[0056] Compared with existing methods for synthesizing γ-Al2O3 and γ-AlOOH nanoparticles, this invention has the following characteristics: (1) γ-AlOOH nanomaterials with different morphologies were prepared by hydrothermal method in aqueous solution using benzenesulfonic acid as a surfactant and aluminum nitrate nonahydrate as an aluminum source, with pH adjusted by ammonia water; (2) Benzenesulfonic acid and Al 3+ The complexation of ions can effectively regulate Al 3+ (3) Under different pH conditions, the adsorption of benzenesulfonic acid anions and nitrate anions on specific crystal planes of γ-AlOOH modulates the growth rate of different crystal planes, thereby obtaining nanomaterials with specific sizes and morphologies; (4) γ-Al2O3 nanorods and nanosheets synthesized by benzenesulfonic acid as a surfactant exhibit excellent catalytic activity, ethylene selectivity and stability in ethanol dehydration reaction, which is better than commonly used commercial alumina SB powder and γ-Al2O3 nanomaterials prepared under the same conditions without benzenesulfonic acid.

[0057] This method uses aluminum nitrate nonahydrate as the aluminum source, benzenesulfonic acid as the surfactant, and ammonia water to adjust the pH of the solution to synthesize γ-AlOOH nanorods and nanosheets via a hydrothermal method; then, high-temperature calcination yields γ-Al2O3 nanorods and nanosheets. The prepared γ-Al2O3 nanomaterials exhibit excellent catalytic performance in the ethanol dehydration reaction, displaying a significant morphological effect. Attached Figure Description

[0058] Figure 1 Transmission electron microscopy images and size statistics of γ-Al2O3 nanorods prepared according to Example 1.

[0059] Figure 2 The image shows the powder X-ray diffraction pattern of the γ-Al2O3 nanorods prepared according to Example 1.

[0060] Figure 3 Transmission electron microscopy images and size statistics of γ-Al2O3 nanosheets prepared according to Example 2.

[0061] Figure 4 The image shows the powder X-ray diffraction pattern of the γ-Al2O3 nanosheets prepared according to Example 2.

[0062] Figure 5 Transmission electron microscopy images and size statistics of γ-AlOOH nanorods prepared according to Example 3.

[0063] Figure 6 The image shows the powder X-ray diffraction pattern of the γ-AlOOH nanorods prepared according to Example 3.

[0064] Figure 7 Transmission electron microscopy images and size statistics of γ-AlOOH nanorods prepared according to Example 4.

[0065] Figure 8 The image shows the powder X-ray diffraction pattern of the γ-AlOOH nanorods prepared according to Example 4.

[0066] Figure 9 Transmission electron microscopy images and size statistics of γ-AlOOH nanosheets prepared according to Example 5.

[0067] Figure 10 The image shows the powder X-ray diffraction pattern of the γ-AlOOH nanosheets prepared according to Example 5.

[0068] Figure 11 The performance of the γ-Al2O3 nanorods in the ethanol dehydration reaction was tested according to Example 6.

[0069] Figure 12 The performance of the ethanol dehydration reaction of γ-Al2O3 nanosheets was tested according to Example 7.

[0070] Figure 13 Transmission electron microscopy images and size statistics of γ-AlOOH nanosheets prepared according to Example 8.

[0071] Figure 14 The image shows the powder X-ray diffraction pattern of the γ-AlOOH nanosheets prepared according to Example 8.

[0072] Figure 15 Transmission electron microscopy images and size statistics of γ-Al2O3 nanosheets prepared according to Example 8.

[0073] Figure 16The image shows the powder X-ray diffraction pattern of the γ-Al2O3 nanosheets prepared according to Example 8.

[0074] Figure 17 The performance of the γ-Al2O3 nanosheets in the ethanol dehydration reaction was tested according to Example 9.

[0075] Figure 18 Transmission electron microscopy images and size statistics of γ-Al2O3 nanosheets prepared according to Example 10.

[0076] Figure 19 The powder X-ray diffraction pattern of the γ-Al2O3 nanosheets prepared according to Example 10 is shown.

[0077] Figure 20 The performance of the ethanol dehydration reaction of γ-Al2O3 nanosheets was tested according to Example 11.

[0078] Figure 21 The performance of the commercial alumina SB powder in the ethanol dehydration reaction was tested according to Example 12. Detailed Implementation

[0079] To better understand the present invention, the following embodiments are provided for further illustration, but they should not be construed as limiting the scope of the present invention.

[0080] Example 1

[0081] 1.40 g of benzenesulfonic acid and 18.00 g of aluminum nitrate nonahydrate were dissolved in 80 mL of water. Ammonia (25-28% concentration) was slowly added dropwise with stirring until the pH reached 7.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed sequentially by centrifugation with water and ethanol, dried overnight at 80 °C, and then calcined at 600 °C for 5 h at a heating rate of 5 °C / min. After cooling to room temperature, a white γ-Al₂O₃ powder was obtained. The prepared γ-Al₂O₃ nanoparticles had a relatively regular nanorod shape, with a length range of 30-235 nm, an average length of 119 nm, and a diameter range of 5-12 nm, with an average diameter of 8.5 nm. Electron micrographs are shown below. Figure 1 X-ray diffraction test results ( Figure 2 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#29-0063, indicating the formation of highly crystalline γ-Al2O3 nanomaterials.

[0082] Example 2

[0083] 1.40 g of benzenesulfonic acid and 18.00 g of aluminum nitrate nonahydrate were dissolved in 80 mL of water. Ammonia (25-28% concentration) was added dropwise with stirring until the pH reached 9.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed sequentially by centrifugation with water and ethanol, dried overnight at 80 °C, ground, and then calcined at 600 °C for 5 h at a heating rate of 5 °C / min. After cooling to room temperature, a white γ-Al₂O₃ powder was obtained. The prepared γ-Al₂O₃ nanoparticles have a relatively regular parallelogram shape with a side length of 15-60 nm, an average side length of 32 nm, a thickness of 4-7 nm, and an average thickness of 5 nm. Electron micrographs are shown below. Figure 3 X-ray diffraction test results ( Figure 4 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#29-0063, indicating the formation of highly crystalline γ-Al2O3 nanomaterials.

[0084] Example 3

[0085] 1.40 g of benzenesulfonic acid and 18.00 g of aluminum nitrate nonahydrate were dissolved in 80 mL of water. Ammonia (25-28% concentration) was added dropwise with stirring until the pH reached 7.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed sequentially by centrifugation with water and ethanol, and dried overnight at 80 °C to obtain a white γ-AlOOH powder. The prepared γ-AlOOH nanoparticles have a relatively regular nanorod shape, with a length range of 40-460 nm and an average length of 182 nm, and a diameter range of 5-18 nm and an average diameter of 10 nm. Electron micrographs are shown below. Figure 5 X-ray diffraction test results ( Figure 6 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#21-1307, indicating the formation of highly crystalline γ-AlOOH nanomaterials.

[0086] Example 4

[0087] 1.40 g of benzenesulfonic acid and 18.00 g of aluminum nitrate nonahydrate were dissolved in 80 mL of water. Ammonia (25-28% concentration) was added dropwise with stirring until the pH reached 8.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed sequentially by centrifugation with water and ethanol, and dried overnight at 80 °C to obtain a white γ-AlOOH powder. The prepared γ-AlOOH nanoparticles have a relatively regular nanorod shape, with a length range of 30-270 nm and an average length of 95 nm, and a diameter range of 4-13 nm and an average diameter of 8 nm. Electron micrographs are shown below. Figure 7 X-ray diffraction test results ( Figure 8 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#21-1307, indicating the formation of highly crystalline γ-AlOOH nanomaterials.

[0088] Example 5

[0089] 1.40 g of benzenesulfonic acid and 18.00 g of aluminum nitrate nonahydrate were dissolved in 80 mL of water. Ammonia (25-28% concentration) was added dropwise with stirring until the pH reached 9.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed sequentially by centrifugation with water and ethanol, and dried overnight at 80 °C to obtain a white γ-AlOOH powder. The prepared γ-AlOOH nanoparticles have a relatively regular parallelogram shape with a side length of 15-60 nm, an average side length of 34 nm, a thickness of 3-8 nm, and an average thickness of 5 nm. Electron micrographs are shown below. Figure 9 X-ray diffraction test results ( Figure 10 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#21-1307, indicating the formation of highly crystalline γ-AlOOH nanomaterials.

[0090] Example 6

[0091] The γ-Al₂O₃ nanorods obtained in Example 1 were granulated to 40-60 mesh. 50 mg of the granules were placed in a quartz reaction tube, heated to 400°C, and He gas was introduced at a flow rate of 30 mL / min for purging for 1 h. After cooling to room temperature, the temperature was raised to 250°C, and a reaction gas with a volume concentration of 1.55% ethanol / He was introduced at a flow rate of 60 mL / min to test the ethanol dehydration reaction performance. Figure 11 As shown, the ethanol conversion rate on γ-Al2O3 nanorods was 26%, and the ethylene selectivity was 27%. After 15 h of reaction, the ethanol conversion rate and ethylene selectivity remained basically unchanged, demonstrating good stability.

[0092] Example 7

[0093] The γ-Al₂O₃ nanosheets obtained in Example 2 were granulated to 40-60 mesh. 50 mg of the granules were placed in a quartz reaction tube, heated to 400°C, and He gas was introduced at a flow rate of 30 mL / min for purging for 1 h. After cooling to room temperature, the temperature was raised to 250°C, and a reaction gas with a volume concentration of 1.55% ethanol / He was introduced at a flow rate of 60 mL / min to test the ethanol dehydration reaction performance. Figure 12As shown, the ethanol conversion rate on γ-Al2O3 nanosheets was 34%, and the ethylene selectivity was 33%. After 15 h of reaction, the ethanol conversion rate increased to 36%, and the ethylene selectivity increased to 37%. Overall, the conversion rate remained stable and increased, demonstrating good reactivity and stability.

[0094] Example 8

[0095] 2.6 mL of dodecylbenzenesulfonic acid and 18.00 g of aluminum nitrate nonahydrate were dissolved in 80 mL of water. Ammonia (25-28% concentration) was added dropwise with stirring until the pH reached 9.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed with water and ethanol by centrifugation and dried overnight at 80 °C to obtain a white γ-AlOOH powder. Although the prepared γ-AlOOH nanoparticles also have a nanosheet shape, their regularity is far less than that of the γ-AlOOH product in Example 5. They are polygons with 4-6 sides, a side length of 20-210 nm, an average side length of 76 nm, and a thickness of 4-9 nm with an average thickness of 6 nm. Electron micrographs are shown below. Figure 13 X-ray diffraction test results ( Figure 14 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#21-1307, indicating the formation of highly crystalline γ-AlOOH nanomaterials.

[0096] The γ-AlOOH nanoparticles were calcined (heated to 600℃ at a rate of 5℃ / min for 5 hours, then cooled to room temperature) to obtain a white γ-Al2O3 powder. The morphology remained irregular, consisting of polygons with 4-6 sides, a side length of 10-190 nm, an average size of 58 nm, and a thickness of 4-8 nm with an average thickness of 5 nm. Electron micrographs are shown below. Figure 15 X-ray diffraction test results ( Figure 16 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#29-0063, indicating the formation of highly crystalline γ-Al2O3 nanomaterials.

[0097] Example 9

[0098] The γ-Al₂O₃ nanosheets obtained in Example 8 were granulated to 40-60 mesh. 50 mg of the granules were placed in a quartz reaction tube, heated to 400°C, and He gas was introduced at a flow rate of 30 mL / min for purging for 1 h. After cooling to room temperature, the temperature was raised to 250°C, and a reaction gas with a volume concentration of 1.55% ethanol / He was introduced at a flow rate of 60 mL / min to test the ethanol dehydration reaction performance. Figure 17As shown, the ethanol conversion rate on the γ-Al₂O₃ nanosheets was 24%, and the ethylene selectivity was 25%. After 15 hours of reaction, the ethanol conversion rate dropped to 12%, and the ethylene selectivity dropped to 15%. Both the reactivity and stability were far inferior to the sample in Example 7. This indicates that, under the same conditions, the γ-Al₂O₃ nanomaterials prepared using benzenesulfonic acid as a surfactant exhibited better ethanol dehydration activity and stability than the product prepared using dodecylbenzenesulfonic acid.

[0099] Example 10

[0100] 18.00 g of aluminum nitrate nonahydrate was dissolved in 80 mL of water, and ammonia (25-28% concentration) was added dropwise with stirring until the pH reached 9.0. 70 mL of the solution was placed in a 100 mL hydrothermal reactor and reacted at 150 °C for 48 h. After cooling to room temperature, the product was washed by centrifugation with water and ethanol, dried at 80 °C overnight, and calcined (heated to 600 °C at a rate of 5 °C / min and calcined for 5 h, then cooled to room temperature) to obtain a white γ-Al₂O₃ powder. The morphology was a non-uniformly sized flake, a polygon with 4-6 sides, a side length of 20-200 nm, an average size of 72 nm, a thickness of 4-10 nm, and an average thickness of 6 nm. Electron micrographs are shown below. Figure 18 X-ray diffraction test results ( Figure 19 The diffraction peak positions in the spectrum are consistent with those in the standard card JCPDS#29-0063, indicating the formation of highly crystalline γ-Al2O3 nanomaterials.

[0101] Example 11

[0102] The γ-Al₂O₃ nanosheets obtained in Example 10 were granulated to 40-60 mesh. 50 mg of the granules were placed in a quartz reaction tube, heated to 400°C, and He gas was introduced at a flow rate of 30 mL / min for purging for 1 h. After cooling to room temperature, the temperature was raised to 250°C, and a reaction gas with a volume concentration of 1.55% ethanol / He was introduced at a flow rate of 60 mL / min to test the ethanol dehydration reaction performance. Figure 20 As shown, the ethanol conversion rate on the γ-Al2O3 nanosheets was 21%, and the ethylene selectivity was 20%. After 15 hours of reaction, the ethanol conversion rate remained essentially unchanged, while the ethylene selectivity dropped to 17%. This result is far inferior to that of Example 7, indicating that under the same conditions, without the addition of a surfactant, the ethanol dehydration reaction conversion rate and ethylene selectivity of the prepared γ-Al2O3 nanomaterials are much lower than those of the product using benzenesulfonic acid as a surfactant.

[0103] Example 12

[0104] 50 mg of calcined SB powder (Sasol) granulated to 40-60 mesh was placed in a quartz reaction tube. The temperature was raised to 400°C, and He gas was introduced at a flow rate of 30 mL / min for purging for 1 hour. After cooling to room temperature, the temperature was raised to 250°C, and a reaction feed gas with a volume concentration of 1.55% ethanol / He was introduced at a flow rate of 60 mL / min to test the ethanol dehydration reaction performance. Figure 21 As shown, the ethanol conversion rate on SB powder was 20%, and the ethylene selectivity was 22%. After 15 hours of reaction, the ethanol conversion rate dropped to 15%, and the ethylene selectivity dropped to 16%. These results are far inferior to those in Examples 6 and 7, indicating that the ethanol dehydration reaction performance of commonly used commercial alumina SB powder is much lower than that of γ-Al2O3 nanomaterials prepared using benzenesulfonic acid as a surfactant.

Claims

1. A method for preparing γ-Al₂O₃ nanorods, the characteristic synthesis process of which is as follows: (1) Dissolve 1.40-2.80 g benzenesulfonic acid and 16.00-20.00 g aluminum nitrate nonahydrate in 70-90 mL of water at room temperature to form a homogeneous aqueous solution; (2) Add 25-28% ammonia solution to the solution prepared in (1) under stirring until the pH reaches 6.8-7.2 and stabilizes; (3) Take 60-80 mL of the solution from step (2) and place it in a hydrothermal reactor. Heat the reactor at 150-200 °C. o Hydrothermal reaction under C conditions for 24-48 h; (4) The product of the hydrothermal reaction in step (3) is washed successively by centrifugation with water and ethanol and then rinsed at 60-100°C. o Drying under C conditions yielded γ-AlOOH nanorods; (5) The γ-AlOOH nanorod precursor from step (4) is prepared at a concentration of 1-10 o The heating rate is 550-600 °C / min. o Calcination at C for 4-6 h yielded γ-Al2O3 nanorods with a length of 30-460 nm and a diameter of 5-18 nm.

2. The application of γ-Al2O3 nanorods prepared by the method of claim 1 in the ethanol dehydration reaction.

3. A method for preparing γ-Al₂O₃ nanosheets, characterized in that: Synthesis process: (1) Dissolve 1.40-2.80 g benzenesulfonic acid and 16.00-20.00 g aluminum nitrate nonahydrate in 70-90 mL of water at room temperature to form a homogeneous aqueous solution; (2) Add 25-28% ammonia solution dropwise to the solution prepared in (1) under stirring conditions until the pH reaches 8.8-9.2 and stabilizes; (3) Take 60-80 mL of the solution from step (2) and place it in a hydrothermal reactor. Heat the reactor at 150-200 °C. o Hydrothermal reaction under C conditions for 24-48 h; (4) The product of the hydrothermal reaction in step (3) is washed successively by centrifugation with water and ethanol and then rinsed at 60-100°C. o Drying under C conditions yielded γ-AlOOH nanosheets; (5) The γ-AlOOH nanosheet product from step (4) is prepared at a concentration of 1-10 o The heating rate is 550-600 °C / min. o Calcination at C for 4-6 h yielded γ-Al2O3 nanosheets.

4. The application of γ-Al2O3 nanosheets prepared by the method of claim 3 in the ethanol dehydration reaction.

Images