Calcium complex catalyst, its preparation method and application

Abstract

The application belongs to the field of catalyst and its preparation technology, 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: in an ethanol-water solution, o-nitrobenzaldehyde, p-aminobenzenesulfonic acid and an alkaline additive 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 DEG C, and after filtration and standing of the filtrate, the calcium complex catalyst is obtained. After benzyl alcohol, a solvent and the calcium complex catalyst are mixed, heating reaction is carried out, and benzaldehyde is prepared. The preparation method of the calcium complex catalyst has the characteristics of low cost, high selectivity, stability and greenness.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysts and its preparation technology, and particularly relates to a calcium complex catalyst and its preparation method and application. BACKGROUND

[0002] Benzaldehyde is a key aromatic aldehyde compound, which is widely used in the fields of perfumes, pharmaceutical intermediates and fine organic synthesis. Preparing benzaldehyde from benzyl alcohol by selective oxidation has significant advantages: the raw material is cheap and easy to obtain, the reaction has high atom economy, the by-products are few, and high-purity products can be easily obtained, which meets the needs of green chemical industry and industrial production. However, the core bottleneck of this process is the development of high-efficiency catalysts. At present, mainstream technologies rely on supported noble metals (such as Pd and Au) or their oxide catalysts, which have certain activity, but the cost of noble metals is high and the resources are scarce, which seriously restricts large-scale industrial application.

[0003] In order to reduce the cost of noble metals, existing research has developed different methods, such as CN102719844A discloses a method for preparing benzaldehyde from benzyl alcohol, which uses imidazole ionic liquid, quaternary ammonium salt ionic liquid, quaternary phosphonium salt ionic liquid, pyridine ionic liquid, etc. as catalysts, and is prepared by electrolysis in a supercritical carbon dioxide system. CN102391084A discloses the use of a catalyst of ferrous salt and a co-catalyst of N-hydroxyphthalimide. CN119930412A discloses the use of titanium dioxide catalyst to catalyze benzyl alcohol into benzaldehyde. CN86103821A discloses a method for preparing benzaldehyde from benzyl alcohol by one-step oxidation, which uses tungsten or molybdenum instead of noble metals Ru, Rh and Pd as catalysts.

[0004] However, the above methods are still limited by the "impossible triangle" of selectivity-activity-stability. The ionic liquid system is subject to the problems of recovery difficulty and complexity of supercritical operation; the NHPI / metal salt system faces the problems of free radical over-oxidation and metal pollution; the titanium dioxide catalyst is subject to the problems of spectral response range and by-product reverse conversion; and the early non-noble metal catalysts have problems such as active site sintering and uncontrollable oxidation depth. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a preparation method of a calcium complex catalyst. The prepared catalyst has a crystal structure, and when used for preparing 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 comprises the following steps: adding o-nitrobenzaldehyde, p-aminobenzenesulfonic acid, an alkaline auxiliary agent into an ethanol-water solution, stirring and heating, then adding a calcium source into the above solution, continuing to stir and heat at 70-85 DEG C, filtering, and placing the filtrate to obtain the calcium complex catalyst.

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

[0008] The o-nitrobenzaldehyde, p-aminobenzenesulfonic acid, alkaline auxiliary agent and calcium source are added in the following mass fractions: 1-3 parts, 1-3 parts, 0.2-0.6 parts and 1-5 parts.

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

[0010] Stirring and heating at 60-70 DEG C for 0.5-2 h.

[0011] Then continuing to stir and heat at 70-85 DEG C for 4-6 h.

[0012] Placing the filtrate for 10-15 days.

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

[0014] The calcium complex catalyst is applied to the process for preparing benzaldehyde from benzyl alcohol, specifically, benzyl alcohol, a solvent and the calcium complex catalyst are mixed, and then heated to prepare benzaldehyde.

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

[0016] Specifically, the preparation method of the calcium complex catalyst comprises 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, sodium hydroxide and potassium hydroxide) into an ethanol-water (volume ratio 1:3-4:1) solution, stirring and heating at 60-70 DEG C for 0.5-2 h, then adding 1-5 g of calcium perchlorate tetrahydrate or calcium chloride hexahydrate solid into the above solution, continuing to stir and heat at 70-85 DEG C for 4-6 h, filtering, and placing the filtrate for 10-15 days to obtain a colorless transparent complex single crystal.

[0017] The process for preparing benzaldehyde from benzyl alcohol is as follows: benzyl alcohol, a solvent (acetonitrile, tetrahydrofuran or 1,4-dioxane) and a calcium complex catalyst are added into a 10 mL stainless steel reactor, the air in the reactor is replaced with oxygen with a purity of 99.999%, and then the reaction mixture is stirred at 130°C for 4-7 h, and the conversion rate of benzyl alcohol and the selectivity of benzaldehyde are detected by gas chromatography with an SE-54 chromatographic column (0.25 mm x 0.25 mm x 30 m).

[0018] The calcium complex catalyst of the present application activates oxygen molecules through Lewis acidity or coordination of calcium ions to form a metal-superoxide intermediate (Ca-O-O⁻•). The metal center transfers a single electron to the π antibonding orbital of O2, triggering the activation of O2 to generate a superoxide radical (O2⁻•). The benzyl alcohol molecule forms a monodentate coordination bond (Ca-O-CH2Ph) with the metal center through the hydroxyl oxygen atom, constructing a metal-alcohol complex. Coordination causes polarization of the alpha-C-H bond of benzyl alcohol, significantly reducing the dehydrogenation energy barrier. The activated superoxide radical (O2⁻•) preferentially attacks the antibonding orbital of the alpha-C-H bond of benzyl alcohol as a strong electrophile, and through a synergistic proton-coupled electron transfer mechanism, it abstracts the alpha-H to generate a benzyloxy intermediate (PhCH2O•) and release H2O. O2 inserts into the C-O bond of the benzyloxy intermediate (PhCH2O•) to form a peroxide intermediate (PhCH(O-O⁻)), followed by O-O bond homolysis to generate benzaldehyde (PhCHO) and release •OH radicals.

[0019] Compared with the prior art, the present application has the beneficial effects that:

[0020] (1) The present application uses inexpensive and readily available calcium complexes (such as calcium perchlorate tetrahydrate or calcium chloride hexahydrate) as the core catalyst, which has low raw material cost and is environmentally friendly due to the abundant reserves of calcium element.

[0021] (2) The present application uses calcium ions to form a metal-superoxide intermediate (Ca-O-O⁻•) with O2 through unoccupied d orbitals, efficiently activating oxygen to generate a superoxide radical (O2⁻•); benzyl alcohol coordinates with the calcium center through the hydroxyl oxygen, polarizing the alpha-C-H bond and reducing the dehydrogenation energy barrier by more than 40%, resulting in high selectivity of benzaldehyde and avoiding the generation of peroxide byproducts.

[0022] (3) The catalyst of the present application is used in the process for preparing benzaldehyde from benzyl alcohol, which is green and environmentally friendly, and has strong universality. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The figure is a crystal structure diagram of the calcium complex catalyst.

[0024] Figure 2 The figure is a scanning electron micrograph of the calcium complex catalyst. DETAILED DESCRIPTION

[0025] The application will be further described in conjunction with specific examples.

[0026] The raw materials and auxiliary agents used in the following examples and comparative examples are commercially available products.

[0027] Example 1

[0028] The preparation method of the calcium complex catalyst includes the following steps: adding 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid and 0.4 g of sodium hydroxide into an ethanol-water (volume ratio 1:3) solution, stirring at 65°C for 0.5 h, then adding 1.555 g of calcium perchlorate tetrahydrate solid into the above solution, and continuing to heat and stir at 75°C for 4 h, then filtering, and placing the filtrate for 12 days to obtain colorless transparent complex single crystals. The crystal structure of the calcium complex is determined by X-ray single crystal diffraction technology, as shown in Figure 1 The calcium complex catalyst is monoclinic, the unit cell space group is Cc, the unit cell parameters are a=35.000(10) Å, b=28.000(6) Å, c=14.000(3), β=107.00(3)°, the volume of the crystal is 1312(5) Å3, and the crystal density is 1.527 g / cm 3 The molecular formula of the calcium complex catalyst is C 104 H 117 Ca4N 16 O 63 S8, and the molecular weight is 3015.94. The surface scanning electron microscope image of the prepared calcium complex catalyst is shown in Figure 2

[0029] The process for preparing benzaldehyde from benzyl alcohol is as follows: 0.0216 g of benzyl alcohol, 1.5 g of 1,4-dioxane and 0.06 g of the calcium complex catalyst are added into a 10 mL stainless steel reaction kettle, the air in the reaction kettle is replaced with oxygen with a purity of 99.999%, then the reaction mixture is stirred at 130°C for 6 h, and a gas chromatograph equipped with a SE-54 chromatographic column (0.25 mm x 0.25 mm x 30 m) is used to detect the conversion rate of benzyl alcohol and the selectivity of benzaldehyde.

[0030] Example 2

[0031] ​The preparation method of the calcium complex catalyst comprises the following steps: 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid and 0.56 g of potassium hydroxide are added into an ethanol-water (volume ratio 4:1) solution, heated to 65 DEG C and stirred for 0.5 h, then 1.555 g of calcium perchlorate tetrahydrate solid is added into the above solution, then heated and stirred at 75 DEG C for 4 h, filtered, and the filtrate is left to stand for 10 days to obtain colorless transparent complex single crystals. The crystal structure of the calcium complex is determined by X-ray single crystal diffraction technology.

[0032] The benzyl alcohol preparation benzaldehyde process is different from that in example 1, and the reaction time in the embodiment is 7 h, and the rest is the same as in example 1.

[0033] Example 3

[0034] The preparation method of the calcium complex catalyst comprises the following steps: 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid and 0.56 g of potassium hydroxide are added into an ethanol-water (volume ratio 4:1) solution, heated to 65 DEG C and stirred for 0.5 h, then 1.555 g of calcium perchlorate tetrahydrate solid is added into the above solution, then heated and stirred at 75 DEG C for 4 h, filtered, and the filtrate is left to stand for 10 days to obtain colorless transparent complex single crystals. The crystal structure of the calcium complex is determined by X-ray single crystal diffraction technology.

[0035] The benzyl alcohol preparation benzaldehyde process is different from that in example 3, and the reaction time in the embodiment is 5 h, and the rest is the same as in example 3.

[0036] Example 4

[0037] The preparation method of the calcium complex catalyst comprises the following steps: 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid and 0.56 g of potassium hydroxide are added into an ethanol-water (volume ratio 4:1) solution, heated to 65 DEG C and stirred for 0.5 h, then 1.555 g of calcium perchlorate tetrahydrate solid is added into the above solution, then heated and stirred at 75 DEG C for 4 h, filtered, and the filtrate is left to stand for 10 days to obtain colorless transparent complex single crystals. The crystal structure of the calcium complex is determined by X-ray single crystal diffraction technology.

[0038] The benzyl alcohol preparation benzaldehyde process is different from that in example 3, and the reaction time in the embodiment is 5 h, and the rest is the same as in example 3.

[0039] Example 5

[0040] The preparation method of the calcium complex catalyst comprises the following steps: 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid and 0.4 g of sodium hydroxide are added into an ethanol-water (volume ratio 1:2) solution, heated to 60 DEG C and stirred for 0.5 h, then 1.555 g of calcium perchlorate hexahydrate solid is added into the above solution, then heated and stirred at 75 DEG C for 4 h, filtered, and the filtrate is left to stand for 10 days to obtain colorless transparent complex single crystal. The crystal structure of the calcium complex is determined by X-ray single crystal diffraction technology.

[0041] The benzyl alcohol preparation benzaldehyde process is different from that of Example 3, and the reaction time is 6 h in this embodiment, and the rest is the same as that of Example 3.

[0042] Example 6

[0043] The preparation method of the calcium complex catalyst comprises the following steps: 1.511 g of o-nitrobenzaldehyde, 1.732 g of p-aminobenzenesulfonic acid and 0.4 g of sodium hydroxide are added into an ethanol-water (volume ratio 1:2) solution, heated to 60 DEG C and stirred for 0.5 h, then 1.555 g of calcium perchlorate hexahydrate solid is added into the above solution, then heated and stirred at 75 DEG C for 4 h, filtered, and the filtrate is left to stand for 10 days to obtain colorless transparent complex single crystal. The crystal structure of the calcium complex is determined by X-ray single crystal diffraction technology.

[0044] The benzyl alcohol preparation benzaldehyde process is: 0.0216 g of benzyl alcohol, 1.5 g of acetonitrile and 0.06 g of calcium complex catalyst are added into a 10 mL stainless steel reaction kettle, the air in the reaction kettle is replaced with oxygen with a purity of 99.999%, and then the reaction mixture is stirred at 130 DEG C for 6 h, and the conversion rate of benzyl alcohol and the selectivity of benzaldehyde are detected by gas chromatography with an SE-54 chromatographic column (0.25 mm x 0.25 mm x 30 m).

[0045] Comparative Example 1

[0046] Different from Example 1, no calcium complex catalyst is added, and the rest of the preparation method and steps of the benzyl alcohol preparation benzaldehyde are the same as those of Example 1.

[0047] Comparative Example 2

[0048] Different from Example 2, no calcium complex catalyst is added, and the rest of the preparation method and steps of the benzyl alcohol preparation benzaldehyde are the same as those of Example 2.

[0049] Comparative Example 3

[0050] The difference between Example 3 and the present example is that no calcium complex catalyst is added, and the rest of the preparation method and steps of preparing benzaldehyde from benzyl alcohol are the same as those of Example 3.

[0051] Comparative Example 4

[0052] The difference between Example 4 and the present example is that no calcium complex catalyst is added, and the rest of the preparation method and steps of preparing benzaldehyde from benzyl alcohol are the same as those of Example 4.

[0053] Comparative Example 5

[0054] The difference between Example 5 and the present example is that no calcium complex catalyst is added, and the rest of the preparation method and steps of preparing benzaldehyde from benzyl alcohol are the same as those of Example 5.

[0055] Comparative Example 6

[0056] The difference between Example 6 and the present example is that no calcium complex catalyst is added, and the rest of the preparation method and steps of preparing benzaldehyde from benzyl alcohol are the same as those of Example 6.

[0057] The conversion rate of benzyl alcohol and the selectivity of benzaldehyde in the benzaldehyde prepared in the above examples and comparative examples are detected, and the results are shown in Table 1.

[0058] Table 1. Detection results

[0059]

[0060] From the data in Table 1, it can be seen that: (1) in the presence of the calcium complex catalyst: in the 1,4-dioxane solvent, the temperature is 130°C, and the reaction is carried out for 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, only the reaction time is changed to 7h, the conversion rate of benzyl alcohol can be increased to 94.1%, but the selectivity of benzaldehyde is sharply decreased to 22.9%. In the tetrahydrofuran solvent, the temperature is 130°C, and the reaction is carried out for 4-6h, the conversion rates of benzyl alcohol are 20.5% (4h), 64.8% (5h), and 85.7% (6h), respectively, and the selectivities of benzaldehyde are 94.5% (4h), 33.5% (5h), and 33.1% (6h), respectively. With the increase of the reaction time, the conversion rate of benzyl alcohol will increase, but the selectivity of benzaldehyde will sharply decrease. In addition, in the acetonitrile solvent, the temperature is 130°C, and the reaction is carried out for 6h, the conversion rate of benzyl alcohol is 51.2%, and the selectivity of benzaldehyde is 11.2%. (2) in the absence of the calcium complex catalyst: the conversion rate of benzyl alcohol is 10.8-12.5%, and the selectivity of benzaldehyde is 2.0-2.6%. Therefore, the optimal reaction conditions for preparing benzaldehyde by catalytic oxidation of benzyl alcohol with the calcium complex catalyst are: in the 1,4-dioxane solvent, the temperature is 130°C, and the reaction is carried out for 6h.

Claims

1. A method for preparing a calcium complex catalyst, characterized in that: The following steps are involved: In an ethanol-water solution with a volume ratio of 1:3-4:1, o-nitrobenzaldehyde, p-aminobenzenesulfonic acid, and an alkaline auxiliary agent are added, and the mixture is heated to 60-70°C and stirred for 0.5-2 hours. A calcium source is then added to the solution, and the mixture is heated and stirred at 70-85°C for 4-6 hours. The mixture is filtered and the filtrate is allowed to stand for 10-15 days to obtain a calcium complex catalyst. Nitrobenzaldehyde, p-aminobenzenesulfonic acid, alkaline additives, and calcium source are added in the following parts by mass: 1-3 parts, 1-3 parts, 0.2-0.6 parts, and 1-5 parts; 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.

2. A calcium complex catalyst, characterized in that: The calcium complex catalyst is prepared by the preparation method of claim 1, wherein the calcium complex catalyst is a monoclinic crystal system, the unit cell space group is Cc, the unit cell parameters are: a=35.000(10)Å, b=28.000(6)Å, c=14.000(3), β=107.00(3)°, the crystal volume is 1312(5)Å3, and the crystal density is 1.527g / cm 3 、Molecular formula is C 104 H 117 Ca4N 16 O 63 S8.

3. Use of the calcium complex catalyst according to claim 2, 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.

4. The use of the calcium complex catalyst according to claim 3, characterized in that: The solvent is acetonitrile, tetrahydrofuran or 1,4-dioxane.

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