Preparation method of nickel and cerium doped aluminum sol catalyst prepared based on helicene phosphorus ligand

Abstract

The invention discloses a preparation method of a nickel and cerium doped catalyst prepared from a helicene derivative phosphorus ligand, the catalyst is an aluminum-based sol which takes a chiral helicene derivative phosphite ester compound as a ligand and is doped with transition metal nickel and rare earth metal cerium, and the catalyst is particularly suitable for 1, 2, 3, 4, 5-tetramethyl-1, 3-pentanediol. The method is used for preparing 2-pentene through high-selectivity hydrogenation of 1, 3-pentadiene.

Description

Technical Field

[0001] This invention relates to the field of catalyst material preparation technology, specifically to a method for preparing an aluminum-based sol catalyst using chiral helicene derivative phosphite compounds as ligands and doped with transition metal nickel and rare earth metal cerium. This catalyst is particularly suitable for the highly selective hydrogenation of 1,3-pentadiene to prepare 2-pentene. Background Technology

[0002] 2-Pentene (including cis and trans isomers) is an important chemical intermediate, widely used in the production of fine chemicals such as pentanol, pentanone, and epoxide, and can also be used as a polymerization monomer or comonomer. One of the main industrial routes for obtaining high-purity 2-pentene is through the selective hydrogenation of 1,3-pentadiene (a key component of the C5 fraction in petroleum cracking). This reaction requires precise control of the degree of hydrogenation, aiming to selectively hydrogenate one of the double bonds in the conjugated diene while minimizing its isomerization (to form 1-pentene) or excessive hydrogenation (to form pentane). Therefore, developing catalysts with high activity, high 2-pentene selectivity, and high stability has significant industrial value.

[0003] Currently, catalysts used for the selective hydrogenation of 1,3-pentadiene mainly include the following categories:

[0004] Supported noble metal catalysts such as Pd / Al2O3 and Pd-Ag / Al2O3 have high activity, but they have obvious drawbacks: (a) noble metals are expensive; (b) they still have some activity for the secondary hydrogenation of monoolefins, which leads to excessive hydrogenation to pentane, and the selectivity needs to be improved; (c) they are sensitive to trace amounts of sulfides in the reactants and are easily poisoned.

[0005] Supported non-precious metal catalysts such as Ni / Al2O3 and Cu / Al2O3, although low in cost, generally have the following problems: (a) Ni-based catalysts are difficult to balance between hydrogenation activity and selectivity, which can easily lead to over-hydrogenation; (b) Metal particles are prone to sintering at high temperatures, which leads to a decrease in activity; (c) The selectivity for the target product 2-pentene is usually not ideal, and it is easy to generate 1-pentene by double bond migration.

[0006] Homogeneous coordination catalysts of Ni and Pd phosphine complexes, while exhibiting excellent activity and selectivity, suffer from bottlenecks such as difficulty in separating the catalyst from the product, expensive ligands, and poor thermal stability, which limit their large-scale industrial application.

[0007] Therefore, there is an urgent need to develop a novel heterogeneous catalyst that combines high activity, high 2-pentene selectivity, good stability, and cost advantages. Aluminum sol, as a support precursor, provides high dispersibility and abundant surface sites. Nickel is an economical and effective hydrogenation active component. The introduction of rare earth cerium can improve nickel dispersion, regulate surface electronic properties, and enhance catalyst stability. More importantly, the introduction of helicene derivative phosphorus ligands with specific spatial conformations and electronic properties is expected to construct "selective pockets" on the catalyst surface. Through steric hindrance and electronic effects, these pockets can preferentially promote the hydrogenation of the terminal double bond of 1,3-pentadiene and inhibit further reactions or isomerization of the intermediate 2-pentene, thereby achieving precise control of reaction selectivity at the molecular level. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel method for preparing a nickel- and cerium-doped aluminum sol catalyst. This catalyst is modified with a functional helicene derivative phosphite ligand and has the characteristics of controllable preparation method, highly dispersed active center, high selectivity for 2-pentene, and good stability. It is specifically used for the highly selective hydrogenation of 1,3-pentadiene to prepare 2-pentene.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a nickel- and cerium-doped catalyst using a spiroene derivative phosphorus ligand includes the following steps:

[0011] (1) Preparation of ligand solution: The spiroene derivative phosphite ligand was dissolved in an anhydrous organic solvent to obtain a ligand solution with a concentration of 0.05-0.3 mol / L for later use. The organic solvent was tetrahydrofuran.

[0012] (2) Preparation of doped aluminum sol: The organoaluminum compound, water-soluble nickel salt and water-soluble cerium salt are dissolved in isopropanol according to the set Ni / Al and Ce / Al molar ratios to prepare a solution with a total metal ion concentration of 0.1-0.5 mol / L. Under continuous stirring, deionized water is added dropwise at a temperature of 60-90℃. The amount of deionized water added is controlled to be 5-20 times the molar amount of the organoaluminum compound to control the hydrolysis rate and maintain the system clear and transparent. After the addition is completed, stirring is continued for 2-3 hours to form a uniform and stable nickel-cerium co-doped aluminum sol.

[0013] (3) Ligand bonding: The ligand solution obtained in step (1) is slowly added dropwise to the thermally doped aluminum sol obtained in step (2) under an inert atmosphere. The dropping rate is controlled at 20-40 drops / minute, and the system temperature is maintained at 70-85℃. After the addition is completed, the reaction is stirred for 2 hours. Then, the pH value is adjusted to about 5.6 with 0.02 mol / L NaOH solution. The precipitated precipitate is separated by centrifugation and washed 3 times with ethanol. Then, it is dried at 40℃ for 1-2 hours.

[0014] (4) Heat treatment: The solid catalyst precursor is dried in an inert atmosphere at 80-120°C for 2-5 hours to finally obtain the catalyst.

[0015] Preferably, the spiroene derivative phosphite ligand in step (1) is bis[4-(spiroene)benzyl](4-ethylbenzyl)phosphate, represented by chemical formula 1. Its preparation method can adopt conventional synthesis methods in the art, such as the similar synthesis route in CN114736158B.

[0016] Chemical Formula 1

[0017] Preferably, in step (2), the organoaluminum compound is selected from aluminum isopropoxide, aluminum tert-butoxide, and aluminum sec-butoxide, with aluminum isopropoxide being the most preferred; the water-soluble nickel salt is nickel nitrate or nickel chloride; and the water-soluble cerium salt is cerium nitrate.

[0018] Preferably, in step (2), the molar ratio of Ni to Al is 1:10 to 5:10 and the molar ratio of Ce to Al is 0.1:10 to 1:10, based on the metal elements.

[0019] More preferably, in step (2), the molar ratio of Ni to Al is 2:10 to 3:10 and the molar ratio of Ce to Al is 0.2:10 to 0.8:10, based on the metal elements.

[0020] More preferably, in step (2), the molar ratio of Ni, Ce and Al is 2.4 : 0.35 : 10 based on the metal elements.

[0021] Preferably, in step (2), the amount of deionized water added is controlled to be 5-10 times the molar amount of the organoaluminum compound, more preferably 5-8 times.

[0022] According to another aspect of the present invention, the present invention also provides a nickel- and cerium-doped catalyst prepared from a helicene derivative phosphorus ligand, said catalyst being prepared according to the method described above.

[0023] According to another aspect of the invention, the invention also provides the use of nickel- and cerium-doped catalysts prepared from the spiroene derivative phosphorus ligands in the highly selective hydrogenation of 1,3-pentadiene to 2-pentene.

[0024] According to another aspect of the present invention, a method for the highly selective hydrogenation of 1,3-pentadiene to 2-pentene is also provided. The method is carried out in a fixed-bed or trickle-bed reactor using a nickel- and cerium-doped catalyst prepared from the spiroene derivative phosphorus ligand, at a reaction temperature of 60-100°C, a reaction pressure of 0.8-2.0 MPa, a hydrogen to 1,3-pentadiene molar ratio of 2:1 to 4:1, and a liquid hourly space velocity of 2-8 h⁻¹. -1 .

[0025] Beneficial effects

[0026] Compared with existing technologies, this invention has the following significant advantages: The unique helical chiral structure and rigid steric hindrance of the helical phosphite ligand create a shape-selective microenvironment on the catalyst surface, effectively promoting the formation of 2-pentene from 1,3-pentadiene and strongly inhibiting further hydrogenation (to pentane) and isomerization (to 1-pentene) of 2-pentene, which is difficult to achieve with traditional supported metal catalysts. Nickel and cerium achieve atomic-level uniform doping and high dispersion in the alumina sol matrix, providing abundant and stable active centers. The addition of cerium not only improves the dispersion of nickel, but its oxygen storage and release capabilities also help remove carbon precursors from the catalyst surface, thus significantly improving the catalyst's resistance to carbon deposition and long-term operational stability. Using non-precious metal nickel as the core active component avoids the use of expensive metals such as palladium and platinum, significantly reducing catalyst costs while ensuring excellent performance, and possessing extremely high industrial application potential. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 Transmission electron microscopy (TEM) image of the catalyst prepared in Example 1;

[0029] Figure 2 Transmission electron microscopy (TEM) image of the catalyst prepared in Example 1;

[0030] Figure 3 The figure shows the stability test results of the catalyst prepared in Example 1 after 100 hours of continuous operation. Detailed Implementation

[0031] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0032] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0033] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0034] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0035] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0036] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0037] Example 1

[0038] (1) Weigh 0.5 mmol of bis[4-(spiroenyl)benzyl](4-ethylbenzyl)phosphate (chemical formula 1) ligand, dissolve it in 50 mL of anhydrous tetrahydrofuran, and keep it under nitrogen protection for later use.

[0039] (2) In a 500 mL three-necked flask, add 10 mmol aluminum isopropoxide, 2.4 mmol nickel nitrate hexahydrate, and 0.35 mmol cerium nitrate hexahydrate, and dissolve in 100 mL anhydrous isopropanol. Stir in an oil bath at 80 °C, and slowly add 3.0 mL of deionized water (approximately 167 mmol H2O molecules) at a dropping rate of approximately 1 drop / second. After the addition is complete, continue stirring at 80 °C for 3 hours to obtain a pale yellow, transparent to translucent Ni-Ce co-doped aluminum sol.

[0040] (3) Under a nitrogen atmosphere, the ligand solution from step (1) is slowly added dropwise to the sol from step (2) at 80°C through a constant pressure dropping funnel, with the dropping rate controlled at 20-40 drops / minute, and the addition is completed in about 1 hour. After the addition is complete, the temperature is raised to 85°C, and the reaction is stirred for 2 hours. Then, the pH is adjusted to about 5.6 with 0.02 mol / L NaOH solution. The precipitate is separated by centrifugation and washed 3 times with ethanol, and then dried at 40°C for 1-2 hours.

[0041] (4) The solid catalyst precursor was dried in a nitrogen atmosphere at 80-120°C for 2-5 hours to finally obtain the catalyst Cat-1. ICP-AES analysis showed that its Ni / Al molar ratio was approximately 2.38:1 and its Ce / Al molar ratio was approximately 0.35:1.

[0042] Example 2

[0043] Catalyst Cat-2 was prepared in the same manner as in Example 1, except that 10 mmol aluminum isopropoxide, 2.0 mmol nickel nitrate hexahydrate and 0.2 mmol cerium nitrate hexahydrate were added.

[0044] Example 3

[0045] Catalyst Cat-3 was prepared in the same manner as in Example 1, except that 10 mmol aluminum isopropoxide, 5.0 mmol nickel nitrate hexahydrate and 0.8 mmol cerium nitrate hexahydrate were added.

[0046] Example 4

[0047] Catalyst Cat-4 was prepared in the same manner as in Example 1, except that 10 mmol aluminum isopropoxide, 3.0 mmol nickel nitrate hexahydrate and 0.35 mmol cerium nitrate hexahydrate were added.

[0048] Comparative Example 1 (Nickel-free)

[0049] Catalyst Cat-5 was prepared in the same manner as in Example 1, except that 10 mmol aluminum isopropoxide and 0.35 mmol cerium nitrate hexahydrate were added, and nickel nitrate hexahydrate was not added.

[0050] Comparative Example 2 (without cerium)

[0051] Catalyst Cat-6 was prepared in the same manner as in Example 1, except that 10 mmol aluminum isopropoxide and 2.4 mmol nickel nitrate hexahydrate were added, and cerium nitrate hexahydrate was not added.

[0052] Comparative Example 3 (without spirophosphorus ligand)

[0053] Catalyst Cat-7 was prepared in the same manner as in Example 1, except that the bis[4-(spiroenyl)benzyl](4-ethylbenzyl)phosphate ligand was not added.

[0054] Comparative Example 4 (Conventional Impregnation Catalyst)

[0055] An equal-volume impregnation method was used: 2.4 mmol of nickel nitrate hexahydrate and 0.35 mmol of cerium nitrate hexahydrate were dissolved in 100 mL of deionized water to prepare a solution. 50 mg of a γ-Al₂O₃ support with a specific surface area of ​​approximately 200 m² / g was used. The γ-Al₂O₃ support was impregnated in the above solution for approximately 1-2 hours. After evaporating the solvent by heating, the solution was calcined at 400 °C in hydrogen / nitrogen atmosphere for 3 hours. This catalyst is designated Cat-8 (impregnation method Ni-Ce / Al₂O₃).

[0056] Test Example 1: Catalytic Performance Evaluation

[0057] The selective hydrogenation of 1,3-pentadiene to 2-pentene was used as a model reaction and tested in a fixed-bed microreactor. The reactor was loaded with 0.5 g of catalyst (crushed into 20-40 mesh particles), and the reaction was carried out at 150 °C with a feed solution (1,3-pentadiene dissolved in n-heptane, concentration 10 wt%) and hydrogen gas. The reaction pressure was 1.2 MPa, the hydrogen-to-pentene molar ratio was 3:1, and the liquid hourly space velocity (LHSV) was 4 h⁻¹. -1 The reaction products were analyzed using online gas chromatography (FID detector, capillary column).

[0058] The evaluation results are shown in Table 1 (data were taken 2 hours after the reaction stabilized):

[0059] Table 1 Catalytic performance of various catalysts for the selective hydrogenation of 1,3-pentadiene

[0060] catalyst 1,3-Pentadiene conversion (%) 2-Pentene Selectivity (%) 1-Pentene Selectivity (%) Pentane selectivity (%) Cat-1 99.2 98.5 1.0 0.5 Cat-2 99.5 93.0 6.3 0.7 Cat-3 98.8 96.8 2.5 0.7 Cat-4 97.5 97.9 1.8 0.3 Cat-5 67.8 51.7 40.8 7.5 Cat-6 84.3 82.3 6.2 11.5 Cat-7 89.7 66.7 28.4 4.9 Cat-8 90.0 42.3 37.5 20.2

[0061] As can be seen from the data in Table 1, Cat-1 to Cat-4 prepared by the method according to the present invention all exhibit high conversion rates and 2-pentene selectivity (>93%), with fewer byproducts (1-pentene and pentane), demonstrating the universality and superiority of the technical solution of the present invention.

[0062] Comparative Example 1 (Cat-5, without Ni) showed very low hydrogenation activity, low conversion of 1,3-pentadiene, and almost no selectivity between 2-pentene and 1-pentene.

[0063] Although the catalysts of Comparative Example 2 (Cat-6, Ce-free) and Comparative Example 3 (Cat-7, Spiroene Phosphorus-free) showed a significant improvement in the conversion of 1,3-pentadiene compared to Comparative Example 1 (Cat-5, Ni-free), the selectivity for 2-pentene remained unsatisfactory, and there were issues of excessive hydrogenation and increased isomerization products. This demonstrates that cerium doping and the presence of ligands are crucial for improving selectivity.

[0064] For Comparative Example 4 (conventional impregnation catalyst), although the conversion of 1,3-pentadiene was improved, the selectivity remained poor. This demonstrates the decisive role of the introduction and in-situ bonding of the helicene phosphorus ligand in the method according to the present invention in constructing highly selective active sites. Catalysts prepared by the conventional impregnation method have low metal dispersion and lack fine-tuning of organic ligands, thus resulting in poor performance.

[0065] Test Example 2: Stability Test

[0066] The catalyst Cat-1 from Example 1 was subjected to a long-term test for 100 hours under the conditions of 80°C, reaction pressure of 1.2 MPa, and LHSV of 4 h⁻¹. The results are shown in Table 2 below. Figure 3 As shown, the catalytic performance remained essentially stable (>98%) over 100 hours. This indicates that the catalyst of this invention has excellent long-term stability.

[0067] Table 2

[0068] Running time (hours) 1,3-Pentadiene conversion (%) 2-Pentene Selectivity (%) 0 0 0 2 97.5 98.4 3 99.1 98.5 4 98.9 98.7 5 99 98.7 20 99 98.4 40 99.1 98.5 60 99.2 98.7 80 98.4 97.8 90 95 98.1 100 93 98.1

[0069] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a nickel- and cerium-doped catalyst using a spiroene derivative phosphorus ligand, comprising the following steps: (1) Preparation of ligand solution: The spiroene derivative phosphite ligand was dissolved in an anhydrous organic solvent to obtain a ligand solution with a concentration of 0.05-0.3 mol / L for later use. The organic solvent was tetrahydrofuran. (2) Preparation of doped aluminum sol: The organoaluminum compound, water-soluble nickel salt and water-soluble cerium salt are dissolved in isopropanol according to the set Ni / Al and Ce / Al molar ratios to prepare a solution with a total metal ion concentration of 0.1-0.5 mol / L. Under continuous stirring, deionized water is added dropwise at a temperature of 60-90℃. The amount of deionized water added is controlled to be 5-20 times the molar amount of the organoaluminum compound to control the hydrolysis rate and maintain the system clear and transparent. After the addition is completed, stirring is continued for 2-3 hours to form a uniform and stable nickel-cerium co-doped aluminum sol. (3) Ligand bonding: The ligand solution obtained in step (1) is slowly added dropwise to the thermally doped aluminum sol obtained in step (2) under an inert atmosphere. The dropping rate is controlled at 20-40 drops / minute, and the system temperature is maintained at 70-85℃. After the addition is completed, the reaction is stirred for 2 hours. Then, the pH value is adjusted to about 5.6 with 0.02 mol / L NaOH solution. The precipitated precipitate is separated by centrifugation and washed 3 times with ethanol. Then, it is dried at 40℃ for 1-2 hours. (4) Heat treatment: The solid catalyst precursor is dried in an inert atmosphere at 80-120°C for 2-5 hours to finally obtain the catalyst.

2. The preparation method according to claim 1, characterized in that, The spiroene derivative phosphite ligand mentioned in step (1) is bis[4-(spiroenyl)benzyl](4-ethylbenzyl)phosphate, represented by chemical formula 1: Chemical formula 1.

3. The preparation method according to claim 1, characterized in that, In step (2), the organoaluminum compound is selected from aluminum isopropoxide, aluminum tert-butoxide, and aluminum sec-butoxide, preferably aluminum isopropoxide; the water-soluble nickel salt is nickel nitrate or nickel chloride; and the water-soluble cerium salt is cerium nitrate.

4. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of Ni to Al is 1:10 to 5:10, and the molar ratio of Ce to Al is 0.1:10 to 1:10, based on the metal elements.

5. The preparation method according to claim 4, characterized in that, In step (2), the molar ratio of Ni to Al is 2:10 to 3:10, and the molar ratio of Ce to Al is 0.2:10 to 0.8:10, based on the metal elements.

6. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of Ni, Ce and Al is 2.4 : 0.35 : 10 according to the metal elements.

7. The preparation method according to claim 1, characterized in that, In step (2), the amount of deionized water added is controlled to be 5-10 times the molar amount of the organoaluminum compound, more preferably 5-8 times.

8. A nickel- and cerium-doped catalyst prepared from a helicene derivative phosphorus ligand, wherein the catalyst is prepared by the method according to any one of claims 1 to 7.

9. Use of the nickel- and cerium-doped catalyst prepared from the spiroene derivative phosphorus ligand according to claim 8 in the highly selective hydrogenation of 1,3-pentadiene to 2-pentene.

10. A method for the highly selective hydrogenation of 1,3-pentadiene to prepare 2-pentene, characterized in that, The method employs a nickel- and cerium-doped catalyst prepared from the spiroene derivative phosphorus ligand according to claim 8 in a fixed-bed or trickle-bed reactor. The reaction temperature is 60-100℃, the reaction pressure is 0.8-2.0 MPa, the molar ratio of hydrogen to 1,3-pentadiene is 2:1 to 4:1, and the liquid hourly space velocity is 2-8 h⁻¹. -1 .

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