Calcium complex catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts and preparation thereof, and particularly relates to a calcium complex catalyst and a preparation method and application thereof. The preparation method of the calcium complex catalyst comprises the following steps: adding o-nitrobenzaldehyde, p-aminobenzene sulfonic acid and an alkali aid into an ethanol-water solution, heating and stirring, adding a calcium source into the solution, continuously heating and stirring at 70-85 DEG C, filtering, and standing the filtrate to obtain the calcium complex catalyst. Benzaldehyde is prepared by mixing benzyl alcohol, a solvent and a calcium complex catalyst and then carrying out a heating reaction. According to the preparation method of the calcium complex catalyst provided by the invention, the prepared catalyst has a crystal structure, is used for preparing benzaldehyde from benzyl alcohol, and has the characteristics of low cost, high selectivity, stability and greenness.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts and their preparation, and in particular relates to a calcium complex catalyst and a preparation method and application thereof. Background Art

[0002] Benzaldehyde, a key aromatic aldehyde, is widely used in fragrances, pharmaceutical intermediates, and fine organic synthesis. The selective oxidation of benzyl alcohol to prepare benzaldehyde offers significant advantages: readily available and inexpensive raw materials, high atom economy, few byproducts, and the ability to easily obtain a high-purity product, meeting the demands of green chemical engineering and industrial production. However, the core bottleneck of this process lies in the development of efficient catalysts. Current mainstream technologies rely on supported noble metals (such as Pd and Au) or their oxide catalysts. While these catalysts possess a certain level of activity, the high cost and scarcity of these precious metals severely restrict their large-scale industrial application.

[0003] To reduce the cost of precious metals, various methods have been developed. For example, CN102719844A discloses a method for producing benzaldehyde by oxidizing benzyl alcohol using imidazole ionic liquids, quaternary ammonium salt ionic liquids, quaternary phosphonium salt ionic liquids, pyridine ionic liquids, and the like as catalysts, and electrolysis in a supercritical carbon dioxide system. CN102391084A discloses a method for producing benzaldehyde using a ferrous salt as a catalyst and N-hydroxyphthalimide as a co-catalyst. CN119930412A discloses the use of titanium dioxide as a catalyst to catalyze the conversion of benzyl alcohol to benzaldehyde. CN86103821A discloses a method for producing benzaldehyde by oxidizing benzyl alcohol in one step using tungsten or molybdenum as a catalyst instead of the precious metals Ru, Rh, or Pd.

[0004] However, these approaches are still limited by the "impossible triangle" of selectivity, activity, and stability. Ionic liquid systems are hampered by recycling challenges and the complexity of supercritical operation; NHPI / metal salt systems face free radical overoxidation and metal contamination; titanium dioxide catalysts are constrained by spectral response and byproduct reverse conversion; and early non-precious metal catalysts suffer from issues such as active site sintering and uncontrolled oxidation depth. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing a calcium complex catalyst. The prepared catalyst has a crystalline structure and is used in the preparation of benzaldehyde from benzyl alcohol. It has the characteristics of low cost, high selectivity, stability and greenness.

[0006] The preparation method of the calcium complex catalyst of the present invention comprises the following steps: adding o-nitrobenzaldehyde, p-aminobenzenesulfonic acid, and an alkaline auxiliary agent to an ethanol-water solution, heating and stirring, adding a calcium source to the solution, and then continuing to heat and stir at 70-85°C, filtering, and allowing the filtrate to stand to obtain the calcium complex catalyst.

[0007] The volume ratio of ethanol to water is 1:3~4:1.

[0008] o-Nitrobenzaldehyde, p-aminobenzenesulfonic acid, alkaline additives, and calcium source are added according to the following parts by mass: 1-3 parts, 1-3 parts, 0.2-0.6 parts, and 1-5 parts.

[0009] The alkaline auxiliary agent is one of ammonia water, sodium hydroxide and potassium hydroxide; the calcium source is calcium perchlorate tetrahydrate or calcium chloride hexahydrate.

[0010] Heat to 60~70℃ and stir for 0.5~2h.

[0011] Then continue heating and stirring at 70~85℃ for 4~6h.

[0012] The filtrate was allowed to stand for 10 to 15 days.

[0013] A calcium complex catalyst is prepared by the preparation method of the calcium complex catalyst, wherein the calcium complex catalyst is a monoclinic crystal, a unit cell space group Cc, and a crystal density of 1.527 g / cm 3 .

[0014] The invention discloses an application of a calcium complex catalyst, which is used in a process for preparing benzaldehyde from benzyl alcohol. Specifically, benzyl alcohol, a solvent and the calcium complex catalyst are mixed, and the mixture is heated for reaction to obtain benzaldehyde.

[0015] The solvent is acetonitrile, tetrahydrofuran or 1,4-dioxane, the heating temperature is 130°C, and the heating time is 4 to 6 hours.

[0016] Specifically, the preparation method of the calcium complex catalyst includes the following steps: adding 1-3 g of o-nitrobenzaldehyde, 1-3 g of p-aminobenzenesulfonic acid and 0.2-0.6 g of an alkaline auxiliary agent (one of ammonia water, sodium hydroxide and potassium hydroxide) to an ethanol-water (volume ratio of 1:3-4:1) solution; heating to 60-70°C and stirring for 0.5-2 hours; adding 1-5 g of calcium perchlorate tetrahydrate or calcium chloride hexahydrate solid to the above solution; then continuing to heat and stir at 70-85°C for 4-6 hours; filtering, and letting the filtrate stand for 10-15 days to obtain a colorless and transparent complex single crystal.

[0017] The process for preparing benzaldehyde from benzyl alcohol comprises the following steps: adding benzyl alcohol, a solvent (acetonitrile, tetrahydrofuran or 1,4-dioxane) and a calcium complex catalyst into a 10 mL stainless steel reactor; replacing the air in the reactor with 99.999% pure oxygen; and stirring the reaction mixture at 130° C. for 4 to 7 hours. The conversion rate of benzyl alcohol and the selectivity for benzaldehyde are detected by gas chromatography equipped with an SE-54 chromatographic column (0.25 mm×0.25 mm×30 m).

[0018] In this calcium complex catalyst, calcium ions activate oxygen molecules through Lewis acidity or coordination, forming a metal-superoxide intermediate (Ca-OO⁻•). The metal center transfers a single electron to the π antibonding orbital of O2, triggering the activation of O2 and generating a superoxide radical (O2⁻•). Benzyl alcohol molecules form a monodentate coordination bond (Ca-O-CH2Ph) with the metal center through their hydroxyl oxygen atoms, forming a metal-alcohol complex. The coordination polarizes the α-CH bond of benzyl alcohol, significantly lowering the dehydrogenation energy barrier. The activated superoxide radical (O2⁻•), acting as a strong electrophile, preferentially attacks the antibonding orbital of the α-CH bond of benzyl alcohol, capturing the α-H through a cooperative proton-coupled electron transfer mechanism, generating a benzyloxy intermediate (PhCH2O•) and releasing H2O. O2 inserts into the CO bond of the benzyloxy intermediate (PhCH2O•) to form a peroxy intermediate (PhCH(OO⁻)), which then undergoes OO bond homolysis to generate benzaldehyde (PhCHO) and release •OH radicals.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses cheap and readily available calcium complexes (such as calcium perchlorate tetrahydrate or calcium chloride hexahydrate) as the core catalyst, which has low raw material costs, abundant calcium reserves, and is environmentally friendly.

[0020] (2) The present invention utilizes calcium ions to form a metal-superoxide intermediate (Ca-OO⁻•) with O2 through unoccupied d orbitals, efficiently activating oxygen to generate superoxide radicals (O2⁻•); benzyl alcohol coordinates with the calcium center through the hydroxyl oxygen, polarizing the α-CH bond, reducing the dehydrogenation energy barrier by more than 40%, achieving high selectivity for benzaldehyde and avoiding the formation of peroxidation byproducts.

[0021] (3) The catalyst of the present invention is used in the process of preparing benzaldehyde from benzyl alcohol, which is green, environmentally friendly and has strong universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the crystal structure diagram of the calcium complex catalyst.

[0023] Figure 2 This is a scanning electron micrograph of the calcium complex catalyst. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific embodiments.

[0025] The raw materials and additives used in the following examples and comparative examples are all commercially available products.

[0026] Example 1 The preparation method of the calcium complex catalyst comprises the following steps: adding 1.511g of o-nitrobenzaldehyde, 1.732g of p-aminobenzenesulfonic acid, and 0.4g of sodium hydroxide to an ethanol-water (volume ratio 1:3) solution, heating and stirring at 65°C for 0.5h, then adding 1.555g of solid calcium perchlorate tetrahydrate to the solution, and continuing to heat and stir at 75°C for 4h. The solution is then filtered and the filtrate is allowed to stand for 12 days to obtain a colorless, transparent single crystal of the complex. The crystal structure of the calcium complex was determined by X-ray single crystal diffraction, as shown in FIG. Figure 1 As shown, the calcium complex catalyst is a monoclinic crystal with a unit cell space group of Cc, unit cell parameters: a=35.000(10)Å, b=28.000(6)Å, c=14.000(3), β=107.00(3)°, a crystal volume of 1312(5)Å3, and a crystal density of 1.527g / cm 3 、Molecular formula is C 104 H 117 Ca4N 16 O 63 S8, molecular weight is 3015.94. The surface scanning electron microscopy image of the prepared calcium complex catalyst is as follows Figure 2 shown.

[0027] The process for preparing benzaldehyde from benzyl alcohol comprises the following steps: adding 0.0216 g of benzyl alcohol, 1.5 g of 1,4-dioxane, and 0.06 g of a calcium complex catalyst into a 10 mL stainless steel reactor; replacing the air in the reactor with 99.999% pure oxygen; and stirring the reaction mixture at 130° C. for 6 hours. The conversion rate of benzyl alcohol and the selectivity for benzaldehyde are detected by gas chromatography equipped with an SE-54 chromatographic column (0.25 mm×0.25 mm×30 m).

[0028] Example 2 The preparation method of the calcium complex catalyst comprises the following steps: adding 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid, and 0.56 g of potassium hydroxide to an ethanol-water solution (volume ratio 4:1), heating to 65°C and stirring for 0.5 h, then adding 1.555 g of solid calcium perchlorate tetrahydrate to the solution. Heating and stirring at 75°C for another 4 h are continued, followed by filtration and allowing the filtrate to stand for 10 days to obtain a colorless, transparent single crystal of the complex. The crystal structure of the calcium complex was determined by X-ray single crystal diffraction.

[0029] The process for preparing benzaldehyde from benzyl alcohol is different from that in Example 1 in that the reaction time in this embodiment is 7 h, and the rest is the same as in Example 1.

[0030] Example 3 The preparation method of the calcium complex catalyst comprises the following steps: adding 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid, and 0.35 g of aqueous ammonia to an ethanol-water solution (volume ratio 2:1), heating to 60°C and stirring for 0.5 h, then adding 1.555 g of solid calcium perchlorate tetrahydrate to the solution. Heating and stirring at 75°C for another 4 h are continued, followed by filtration and the filtrate is allowed to stand for 15 days to obtain a colorless, transparent single crystal of the complex. The crystal structure of the calcium complex was determined by X-ray single crystal diffraction.

[0031] The process for preparing benzaldehyde from benzyl alcohol is as follows: 0.0216 g of benzyl alcohol, 1.5 g of tetrahydrofuran, and 0.06 g of a calcium complex catalyst are added to a 10 mL stainless steel reactor, the air in the reactor is replaced with 99.999% pure oxygen, and the reaction mixture is stirred at 130° C. for 4 hours. The conversion rate of benzyl alcohol and the selectivity for benzaldehyde are detected by gas chromatography equipped with an SE-54 chromatographic column (0.25 mm×0.25 mm×30 m).

[0032] Example 4 The preparation method of the calcium complex catalyst comprises the following steps: adding 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid, and 0.4 g of sodium hydroxide to an ethanol-water solution (volume ratio of 1:1), heating to 70°C and stirring for 0.5 h, then adding 1.555 g of solid calcium perchlorate tetrahydrate to the solution. Heating and stirring at 75°C for another 4 h are continued, followed by filtration and allowing the filtrate to stand for 10 days to obtain a colorless, transparent single crystal of the complex. The crystal structure of the calcium complex was determined by X-ray single crystal diffraction.

[0033] The process for preparing benzaldehyde from benzyl alcohol is different from that in Example 3 in that the reaction time in this embodiment is 5 h, and the rest is the same as in Example 3.

[0034] Example 5 The preparation method of the calcium complex catalyst comprises the following steps: adding 1.511g of o-nitrobenzaldehyde, 1.732g of p-aminobenzenesulfonic acid, and 0.4g of sodium hydroxide to an ethanol-water solution (volume ratio of 1:2), heating to 60°C and stirring for 0.5h, then adding 1.555g of solid calcium perchlorate tetrahydrate to the solution. Heating and stirring at 75°C for another 4h are then continued, followed by filtration and the filtrate is allowed to stand for 10 days to obtain a colorless, transparent single crystal of the complex. The crystal structure of the calcium complex was determined by X-ray single crystal diffraction.

[0035] The process for preparing benzaldehyde from benzyl alcohol is different from that in Example 3 in that the reaction time in this embodiment is 6 h, and the rest is the same as in Example 3.

[0036] Example 6 The preparation method of the calcium complex catalyst comprises the following steps: adding 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid, and 0.56 g of potassium hydroxide to an ethanol-water solution (volume ratio 3:2), heating to 60°C and stirring for 2 hours, then adding 2.191 g of solid calcium chloride hexahydrate to the solution. The solution is then heated and stirred at 75°C for another 4 hours, filtered, and the filtrate allowed to stand for 10 days to obtain a colorless, transparent single crystal of the complex. The crystal structure of the calcium complex was determined by X-ray single crystal diffraction.

[0037] The process for preparing benzaldehyde from benzyl alcohol is as follows: 0.0216 g of benzyl alcohol, 1.5 g of acetonitrile and 0.06 g of a calcium complex catalyst are added to a 10 mL stainless steel reactor, the air in the reactor is replaced with 99.999% pure oxygen, and the reaction mixture is stirred at 130° C. for 6 hours. The conversion rate of benzyl alcohol and the selectivity for benzaldehyde are detected by gas chromatography equipped with an SE-54 chromatographic column (0.25 mm×0.25 mm×30 m).

[0038] Comparative Example 1 The difference from Example 1 is that no calcium complex catalyst is added, and the remaining preparation method and steps for preparing benzaldehyde from benzyl alcohol are the same as those in Example 1.

[0039] Comparative Example 2 The difference from Example 2 is that no calcium complex catalyst is added, and the remaining preparation method and steps for preparing benzaldehyde from benzyl alcohol are the same as those in Example 2.

[0040] Comparative Example 3 The difference from Example 3 is that no calcium complex catalyst is added, and the remaining preparation method and steps for preparing benzaldehyde from benzyl alcohol are the same as those in Example 3.

[0041] Comparative Example 4 The difference from Example 4 is that no calcium complex catalyst is added, and the remaining preparation method and steps for preparing benzaldehyde from benzyl alcohol are the same as those in Example 4.

[0042] Comparative Example 5 The difference from Example 5 is that no calcium complex catalyst is added, and the remaining preparation method and steps for preparing benzaldehyde from benzyl alcohol are the same as those in Example 5.

[0043] Comparative Example 6 The difference from Example 6 is that no calcium complex catalyst is added, and the remaining preparation method and steps for preparing benzaldehyde from benzyl alcohol are the same as those in Example 6.

[0044] The conversion rate of benzyl alcohol and the selectivity of benzaldehyde in the benzaldehyde prepared in the above examples and comparative examples are shown in Table 1.

[0045] Table 1 Test results

[0046] From the data in Table 1, we can see that: (1) When a calcium complex catalyst is added: in 1,4-dioxane solvent, the temperature is 130℃, and the reaction time is 6h, the conversion rate of benzyl alcohol is 50.6%, and the selectivity of benzaldehyde is 95.3%. Under the same solvent and reaction temperature conditions, the reaction time is changed to 7h, and the conversion rate of benzyl alcohol can be increased to 94.1%, but the selectivity of benzaldehyde drops sharply to 22.9%. In tetrahydrofuran solvent, the temperature is 130℃, and the reaction time is 4-6h, the conversion rate of benzyl alcohol is 20.5% (4h), 64.8% (5h), and 85.7% (6h), respectively, and the selectivity of benzaldehyde is 94.5% (4h), 33.5% (5h), and 33.1% (6h), respectively. As the reaction time increases, the conversion rate of benzyl alcohol increases, but the selectivity of benzaldehyde drops sharply. In addition, in acetonitrile solvent, at a temperature of 130°C and a reaction time of 6 h, the conversion of benzyl alcohol was 51.2%, and the selectivity for benzaldehyde was 11.2%. (2) Without the addition of a calcium complex catalyst, the conversion of benzyl alcohol was 10.8-12.5%, and the selectivity for benzaldehyde was 2.0-2.6%. Therefore, the optimal reaction conditions for the catalytic oxidation of benzyl alcohol to benzaldehyde using a calcium complex catalyst are: in 1,4-dioxane solvent, at a temperature of 130°C and a reaction time of 6 h.

Claims

1. A method for preparing a calcium complex catalyst, characterized in that: The following steps are involved: In an ethanol-water solution, o-nitrobenzaldehyde, p-aminobenzenesulfonic acid, and an alkaline auxiliary agent are added, and after heating and stirring, a calcium source is added to the above solution. Then, heating and stirring are continued at 70-85°C, and the solution is filtered and the filtrate is allowed to stand to obtain a calcium complex catalyst.

2. The method for preparing a calcium complex catalyst according to claim 1, wherein: The volume ratio of ethanol to water is 1:3~4:

1.

3. The method for preparing a calcium complex catalyst according to claim 1, wherein: o-Nitrobenzaldehyde, p-aminobenzenesulfonic acid, alkaline additives, and calcium source are added according to the following parts by mass: 1-3 parts, 1-3 parts, 0.2-0.6 parts, and 1-5 parts.

4. The method for preparing a calcium complex catalyst according to claim 3, wherein: The alkaline auxiliary agent is one of ammonia water, sodium hydroxide and potassium hydroxide; the calcium source is calcium perchlorate tetrahydrate or calcium chloride hexahydrate.

5. The method for preparing a calcium complex catalyst according to claim 1, wherein: Heat to 60~70℃ and stir for 0.5~2h.

6. The method for preparing a calcium complex catalyst according to claim 5, wherein: Then continue heating and stirring at 70~85℃ for 4~6h.

7. The method for preparing a calcium complex catalyst according to claim 1, wherein: The filtrate was allowed to stand for 10 to 15 days.

8. A calcium complex catalyst, characterized in that: The calcium complex catalyst is prepared by the preparation method of any one of claims 1 to 7, wherein the calcium complex catalyst is a monoclinic crystal with a unit cell space group of Cc and a crystal density of 1.527 g / cm 3 .

9. An application of a calcium complex catalyst, characterized in that: The method is used in a process for preparing benzaldehyde from benzyl alcohol, specifically comprising the steps of mixing benzyl alcohol, a solvent and a calcium complex catalyst, and heating the mixture for reaction to obtain benzaldehyde.

10. The use of the calcium complex catalyst according to claim 9, characterized in that: The solvent is acetonitrile, tetrahydrofuran or 1,4-dioxane.

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