Spherical alumina carrier for propane dehydrogenation and preparation method and catalyst thereof

Abstract

The invention belongs to the field of propane dehydrogenation catalysts, and particularly provides a spherical alumina carrier for propane dehydrogenation, a preparation method of the spherical alumina carrier and a catalyst.The preparation method of the spherical alumina carrier for propane dehydrogenation comprises the following steps that 1, pseudo-boehmite sol and polysaccharide are evenly mixed, and a precursor solution is obtained after curing; (2) dropwise adding the precursor solution into an oil ammonia forming column, and gelatinizing and curing to obtain gel balls; the upper layer of the oil ammonia forming column is a paraffin oil layer, and the lower layer is a composite ammonia water solution; the composite ammonia water solution comprises ammonia water, 2-formylphenylboronic acid and zinc nitrate; and 3) washing the obtained gel balls with deionized water and absolute ethyl alcohol, then transferring the gel balls into an aging solution for aging, filtering, washing, drying, and then roasting to obtain the catalyst. The catalyst prepared by the invention has the advantages of high catalytic activity and coking resistance.

Description

Technical Field

[0001] This application belongs to the field of propane dehydrogenation catalyst technology, and in particular relates to a spherical alumina support for propane dehydrogenation, its preparation method, and the catalyst thereof. Background Technology

[0002] Propylene is a raw material for various chemical products such as polypropylene, propylene oxide, acrylonitrile, and acrylic acid. Global propylene consumption has increased significantly in recent years and continues to grow. For decades, propylene production has primarily relied on fluidized bed catalytic cracking and steam cracking of naphtha and light diesel oil. However, with the excessive consumption of fossil fuels, traditional propylene production technologies can no longer meet the growing market demand.

[0003] Currently, many propylene production technologies have been developed, such as methanol-to-propylene, Fischer-Tropsch water-gas shift reaction, and propane dehydrogenation. Due to the ease of shale gas extraction and abundant propane sources, propane dehydrogenation technology has become a powerful way to fill the propylene supply-demand gap. Compared with other technologies such as integrated refining and chemical production and coal / methanol-to-olefins, the byproduct hydrogen from propane dehydrogenation technology, as a high-value-added product, can enhance the value of the industrial chain and presents unique advantages. The propane dehydrogenation process is thermodynamically disadvantageous and requires a catalyst to complete efficiently. Commonly used propane dehydrogenation catalysts include platinum-based catalysts, chromium-based catalysts, and composite oxide catalysts. Among them, chromium-based catalysts are limited in application due to the high toxicity and easy deactivation of Cr. Platinum-based catalysts are environmentally friendly and have a good affinity for CH bonds, exhibiting excellent propane dehydrogenation activity.

[0004] Although platinum-based catalysts exhibit high activity, they suffer from coking due to excessive CC cracking and deep dehydrogenation. The high temperatures during the reaction and catalyst regeneration processes can induce Ostwald ripening, leading to sintering of platinum nanoparticles and catalyst deactivation. Therefore, developing platinum-based catalysts with superior activity and stability is of significant technological importance. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a spherical alumina support for propane dehydrogenation, its preparation method, and a catalyst.

[0006] This application first provides a method for preparing a spherical alumina support for propane dehydrogenation, comprising the following steps:

[0007] 1) Take pseudoboehmite sol and polysaccharide, mix them evenly, and mature them to obtain the precursor solution;

[0008] 2) The precursor solution is dripped into the oil-ammonia molding column, and gelled and solidified to obtain gel spheres; the upper layer of the oil-ammonia molding column is a paraffin oil layer, and the lower layer is a composite ammonia aqueous solution; the composite ammonia aqueous solution includes ammonia water, 2-formylphenylboronic acid, and zinc nitrate;

[0009] 3) Wash the obtained gel balls with deionized water and anhydrous ethanol, then transfer them to an aging solution for aging, filter, wash, dry, and then calcine to obtain the final product.

[0010] Furthermore, the preparation method of the pseudoboehmite sol includes the following steps: mixing pseudoboehmite solution and deionized water evenly, then adding tannic acid / acetic acid mixed solution dropwise, stirring and letting stand to obtain the product.

[0011] Furthermore, the polysaccharide includes carrageenan and starch.

[0012] Furthermore, the aging solution includes ammonia, ethanol, and DMSO.

[0013] This application provides a spherical alumina support for propane dehydrogenation, which is prepared by the above-described method.

[0014] Furthermore, the specific surface area of ​​the carrier is 150-300 m². 2 / g.

[0015] This application provides a catalyst comprising the above-mentioned spherical alumina support for propane dehydrogenation, a main active component, and a secondary active component; the main active component comprises Pt; and the secondary active component comprises Ce and Sn.

[0016] Furthermore, the loading amount of the main active component is 0.15-1 wt% of the carrier mass based on the weight of Pt.

[0017] Furthermore, the loading of the secondary active component is 2.5-5 wt% of the carrier mass based on Ce weight.

[0018] Furthermore, the loading amount of the secondary active component is 0.2-0.75 wt% of the carrier mass based on the weight of Sn.

[0019] Compared with the prior art, this application has the following beneficial effects:

[0020] This application uses a mixture of boehmite sol and polysaccharides as a precursor solution. In the early stage of alumina gel network growth, the double helix molecular chains of carrageenan in the polysaccharide can enhance the metal coordination sites, and tannic acid can chelate with aluminum ions or hydroxyl hydrates. Both contribute to the formation of finer and more uniform alumina grains, thereby obtaining a more stable and uniform pore distribution morphology. In addition, during the gelation and curing process, ammonia water first performs the first stage of curing, followed by 2-formylphenylboronic acid forming dynamic crosslinks with the amino groups inside the gel. At the same time, zinc ions interact with the coordination sites inside the gel, which not only reduces local acid defects in the support but also provides uniform and stable nucleation sites and electronic environment for subsequent impregnation of active components such as Pt, forming active centers with stronger anti-coking ability and improving the selectivity and catalytic activity of the catalyst. Attached Figure Description

[0021] Figure 1 This is a schematic diagram showing the performance evaluation data of propylene dehydrogenation reaction in Examples 1-2 and the control group of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0025] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0026] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0027] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0028] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0029] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0030] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0031] In this application, room temperature refers to 0~40℃, including but not limited to 10~40℃, or further to 20~30℃.

[0032] Based on extensive experimental research, this application provides a method for preparing a spherical alumina support for propane dehydrogenation, comprising the following steps:

[0033] 1) Take pseudoboehmite sol and polysaccharide, mix them evenly, and mature them to obtain the precursor solution;

[0034] 2) The precursor solution is dripped into the oil-ammonia molding column, and gelled and solidified to obtain gel spheres; the upper layer of the oil-ammonia molding column is a paraffin oil layer, and the lower layer is a composite ammonia aqueous solution; the composite ammonia aqueous solution includes ammonia water, 2-formylphenylboronic acid, and zinc nitrate;

[0035] 3) Wash the obtained gel balls with deionized water and anhydrous ethanol, then transfer them to an aging solution for aging, filter, wash, dry, and then calcine to obtain the final product.

[0036] Furthermore, the preparation method of the pseudoboehmite sol includes the following steps: mixing pseudoboehmite solution and deionized water evenly, then adding tannic acid / acetic acid mixed solution dropwise, stirring and letting stand to obtain the product.

[0037] Furthermore, the polysaccharide includes carrageenan and starch.

[0038] Furthermore, the aging solution includes ammonia, ethanol, and DMSO.

[0039] This application provides a spherical alumina support for propane dehydrogenation, which is prepared by the above-described method.

[0040] Furthermore, the specific surface area of ​​the carrier is 150-300 m². 2 / g.

[0041] This application provides a catalyst comprising the above-mentioned spherical alumina support for propane dehydrogenation, a main active component, and a secondary active component; the main active component comprises Pt; and the secondary active component comprises Ce and Sn.

[0042] Furthermore, the loading amount of the main active component is 0.15-1 wt% of the carrier mass based on the weight of Pt.

[0043] In some specific embodiments, the loading amount of the main active component, based on the weight of Pt, can be 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1% of the carrier mass. Generally, a loading amount of the main active component of 0.5% of the carrier mass, based on the weight of Pt, yields better experimental results.

[0044] Furthermore, the loading of the secondary active component is 2.5-5 wt% of the carrier mass based on Ce weight.

[0045] In some specific embodiments, the loading amount of the secondary active component, based on Ce weight, can be 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt% of the carrier mass. Generally, a better technical effect can be achieved when the loading amount of the secondary active component, based on Ce weight, is 3.5 wt% of the carrier mass.

[0046] Furthermore, the loading amount of the secondary active component is 0.2-0.75 wt% of the carrier mass based on the weight of Sn.

[0047] In some specific embodiments, the loading amount of the secondary active component, based on the weight of Sn, can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, or 0.75% of the carrier mass. Generally, a loading amount of the secondary active component of 0.5 wt% of the carrier mass based on the weight of Sn achieves better technical results.

[0048] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0049] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0050] Example 1

[0051] The preparation method of the spherical alumina support for propane dehydrogenation in this embodiment includes the following steps:

[0052] 1) Weigh 20g of boehmite and 75g of deionized water and stir well. Then slowly add 5g of tannic acid / acetic acid mixed solution, stir and let stand to obtain boehmite sol. Take 100g of boehmite sol and 4g of polysaccharide, mix well, and place in an oven to mature at 80℃ for 2 hours to obtain precursor solution. The mass ratio of tannic acid to acetic acid is 1:4. The polysaccharide consists of 1.5g of carrageenan and 2.5g of corn starch.

[0053] 2) The precursor solution is dripped into the oil-ammonia molding column using a syringe, and gelled and solidified to obtain gel spheres; the upper layer of the oil-ammonia molding column is a paraffin oil layer, and the lower layer is a composite ammonia solution; the components of the composite ammonia solution are: 90% ammonia water, 5% 2-formylphenylboronic acid, and 5% zinc nitrate.

[0054] 3) The obtained gel spheres were washed with deionized water and anhydrous ethanol, then transferred to an aging solution and aged at 80°C for 12 hours. After cooling to room temperature, the aged gel spheres were filtered, washed, and dried in an oven at 60°C for 12 hours. They were then transferred to a muffle furnace and calcined at 700°C for 2.5 hours. The aging solution consisted of 50% ammonia, 40% ethanol, and 10% DMSO. The specific surface area of ​​the carrier was determined to be 265.1 cm² using nitrogen physical adsorption. 2 / g, with an average pore size of 18.8nm.

[0055] The catalyst in this embodiment was prepared by the following steps: 0.019 g of stannous chloride dihydrate and 0.21 g of cerium nitrate hexahydrate were weighed and dissolved in 20 mL of deionized water. Then, 2.82 mL of chloroplatinic acid solution with a concentration of 0.0193 mol / L was added. The pH was adjusted to 8 with 2.5 wt% ammonia solution. 2 g of the spherical alumina support for propane dehydrogenation prepared in this embodiment was added. The mixture was stirred and impregnated for 5 h. The water was removed by rotary evaporation at 60 °C. The mixture was dried at 80 °C for 6 h. Then, it was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the catalyst.

[0056] Example 2

[0057] The preparation method of the spherical alumina support for propane dehydrogenation in this embodiment includes the following steps:

[0058] 1) Weigh 25g of boehmite and 75g of deionized water and stir evenly. Then slowly add 5g of tannic acid / acetic acid mixed solution, stir and let stand to obtain boehmite sol. Take 100g of boehmite sol and 4g of polysaccharide, mix evenly, and place in an oven to mature at 80℃ for 2h to obtain precursor solution. The mass ratio of tannic acid to acetic acid is 1:4. The polysaccharide consists of 1.5g of carrageenan and 2.5g of corn starch. The carrageenan in this embodiment has been modified. The modification method is as follows: mix carrageenan with deionized water to prepare a carrageenan solution with a solid content of 35%, then add a magnesium nitrate solution with a concentration of 5wt%, mix evenly, stir at 60℃ for 1.5h, then evaporate, wash and dry.

[0059] 2) The precursor solution is dripped into the oil-ammonia molding column using a syringe, and gelled and solidified to obtain gel spheres; the upper layer of the oil-ammonia molding column is a paraffin oil layer, and the lower layer is a composite ammonia solution; the components of the composite ammonia solution are: 80% ammonia water, 10% 2-formylphenylboronic acid, and 10% zinc nitrate.

[0060] 3) The obtained gel spheres were washed with deionized water and anhydrous ethanol, then transferred to an aging solution and aged at 80°C for 12 hours. After cooling to room temperature, the aged gel spheres were filtered, washed, and dried in an oven at 60°C for 12 hours. They were then transferred to a muffle furnace and calcined at 700°C for 2.5 hours to obtain the final product. The aging solution consisted of 50% ammonia, 40% ethanol, and 10% DMSO. The specific surface area of ​​the carrier was determined to be 273.8 cm² using nitrogen physical adsorption. 2 / g, with an average pore size of 19.2nm.

[0061] The catalyst in this embodiment was prepared by the following steps: 0.019 g of stannous chloride dihydrate and 0.21 g of cerium nitrate hexahydrate were weighed and dissolved in 20 mL of deionized water. Then, 2.82 mL of chloroplatinic acid solution with a concentration of 0.0193 mol / L was added. The pH was adjusted to 8 with 2.5 wt% ammonia solution. 2 g of the spherical alumina support for propane dehydrogenation prepared in this embodiment was added. The mixture was stirred and impregnated for 5 h. The water was removed by rotary evaporation at 60 °C. The mixture was dried at 80 °C for 6 h. Then, it was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the catalyst.

[0062] control group

[0063] The preparation method of the spherical alumina support for propane dehydrogenation in this control group includes the following steps:

[0064] 1) Weigh 20g of boehmite and 75g of deionized water and stir evenly. Then slowly add 5g of acetic acid mixed solution, stir and let stand to obtain boehmite sol. Take 100g of boehmite sol and 4g of corn starch and mix evenly. Place in an oven and mature at 80℃ for 2 hours to obtain the precursor solution.

[0065] 2) The precursor solution is dripped into the oil-ammonia molding column using a syringe, and gelled and solidified to obtain gel spheres; the upper layer of the oil-ammonia molding column is a paraffin oil layer, and the lower layer is an ammonia solution;

[0066] 3) The obtained gel spheres were washed with deionized water and anhydrous ethanol, then transferred to an aging solution and aged at 80°C for 12 hours. After cooling to room temperature, the aged gel spheres were filtered, washed, and dried in an oven at 60°C for 12 hours. They were then transferred to a muffle furnace and calcined at 700°C for 2.5 hours. The aging solution consisted of 50% ammonia, 40% ethanol, and 10% DMSO. The specific surface area of ​​the carrier was determined to be 227.9 cm² using nitrogen physical adsorption. 2 / g, with an average pore size of 13.1nm.

[0067] The catalyst for this control group was prepared using the following steps: 0.019 g of stannous chloride dihydrate and 0.21 g of cerium nitrate hexahydrate were weighed and dissolved in 20 mL of deionized water. Then, 2.82 mL of 0.0193 mol / L chloroplatinic acid solution was added, and the pH was adjusted to 8 with 2.5 wt% ammonia solution. 2 g of the spherical alumina support for propane dehydrogenation prepared in this control group was added, and the mixture was stirred and impregnated for 5 h. The water was removed by rotary evaporation at 60 °C, and the mixture was dried at 80 °C for 6 h. Then, the mixture was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the final catalyst.

[0068] Performance testing

[0069] The propane dehydrogenation performance of the catalysts from Examples 1-2 and the control group was evaluated using a quartz tube fixed reactor. The catalyst loading was 0.15 g. Under hydrogen conditions, the temperature was increased to 600 °C at a rate of 5 °C / min, and reduction was carried out for 2 h. Propane was then introduced at a pressure of 0.05 MPa, with a hydrogen to propane molar ratio of 0.5 and a WHSV of 6 h. -1 The gaseous products of the propane dehydrogenation reaction were monitored online using gas chromatography. The reactor outlet gas composition included methane, ethane, ethylene, propane, and propylene. Propane conversion rate = (X...) in -X out ) / X in Propane selectivity = Y out / (X in -X out ), X in X represents the volume fraction of imported propane. out Y represents the volume fraction of propane exported. out This represents the volume fraction of propylene exported. Specific test data are as follows: Figure 1 As shown.

[0070] analyze Figure 1It can be seen that the catalyst of this application has high catalytic activity, better propane conversion and propylene selectivity than conventional catalysts, and high stability with better anti-coking performance.

[0071] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing a spherical alumina carrier for propane dehydrogenation, characterized by: Includes the following steps: 1) Take pseudoboehmite sol and polysaccharide, mix them evenly, and mature them to obtain the precursor solution; 2) The precursor solution is dripped into the oil-ammonia molding column, and gelled and solidified to obtain gel spheres; the upper layer of the oil-ammonia molding column is a paraffin oil layer, and the lower layer is a composite ammonia aqueous solution; the composite ammonia aqueous solution includes ammonia water, 2-formylphenylboronic acid, and zinc nitrate; 3) Wash the obtained gel balls with deionized water and anhydrous ethanol, then transfer them to an aging solution for aging, filter, wash, dry, and then calcine to obtain the final product.

2. The method for producing a spherical alumina carrier for propane dehydrogenation according to claim 1, characterized by: The preparation method of the pseudoboehmite sol includes the following steps: mixing pseudoboehmite solution and deionized water evenly, then adding tannic acid / acetic acid mixed solution dropwise, stirring and letting stand to obtain the sol.

3. The method for preparing the spherical alumina support for propane dehydrogenation according to claim 1, characterized in that: The polysaccharides include carrageenan and starch.

4. The method for preparing the spherical alumina support for propane dehydrogenation according to claim 1, characterized in that: The aging solution includes ammonia, ethanol and DMSO.

5. A spherical alumina support for propane dehydrogenation, characterized in that: It is prepared by any one of the preparation methods described in claims 1-4.

6. The spherical alumina support for propane dehydrogenation according to claim 5, characterized in that: The specific surface area of the support is between 150 and 300 m 2 / g.

7. A catalyst, characterized in that: It includes the spherical alumina support for propane dehydrogenation as described in claim 5, a main active component, and a secondary active component; the main active component includes Pt; and the secondary active components include Ce and Sn.

8. The catalyst according to claim 7, characterized in that: The loading of the main active component is 0.15-1 wt% of the carrier mass based on the weight of Pt.

9. The catalyst according to claim 7, characterized in that: The loading of the secondary active component is 2.5-5 wt% of the carrier mass based on Ce weight.

10. The catalyst according to claim 7, characterized in that: The loading of the secondary active component is 0.2-0.75 wt% of the carrier mass based on the weight of Sn.

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