Copper-magnesium-aluminum hydrotalcite catalyst for synthesizing tetra-tert-butyl biphenyl diquinone through oxidative coupling of 2, 6-di-tert-butyl phenol and preparation method of copper-magnesium-aluminum hydrotalcite catalyst

Abstract

The invention belongs to the technical field of catalyst preparation and organic synthesis, and discloses a copper-magnesium-aluminum hydrotalcite catalyst for synthesizing tetra-tert-butylbiphenyl diquinone through oxidative coupling of 2, 6-di-tert-butylphenol and a preparation method of the copper-magnesium-aluminum hydrotalcite catalyst, and the preparation method comprises the following steps: (1) dissolving soluble salts of Cu, Mg and Al in water to obtain a mixed salt solution A; (2) dissolving NaOH and / or Na2CO3 in water to obtain an alkali solution B; (3) dissolving a gemini surfactant in a mixed solvent composed of water and lower alcohol to obtain a solution C; (4) under continuous stirring and protective gas atmosphere, dropwise adding the solution A and the solution B into the solution C to form mixed slurry; and (5) carrying out ultrasonic-assisted aging treatment on the mixed slurry at 60-80 DEG C for 6-16 hours, carrying out centrifugal separation, washing the solid until the filtrate is neutral, and drying and grinding the solid to obtain the catalyst. The catalyst has more active sites, and is high in catalytic activity, good in selectivity and easy to separate and recover.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation and organic synthesis, and particularly relates to a copper-magnesium-aluminum hydrotalcite catalyst for oxidatively coupling 2,6-di-tert-butylphenol to form tetra-tert-butyl diphenylquinone and a preparation method thereof. BACKGROUND

[0002] Tetraalkyl diphenylquinone (such as TBDPQ) is a kind of high-performance electron transport material. At present, its industrial production faces many challenges, such as equipment corrosion caused by using homogeneous copper salt catalyst, difficult product separation, and a large amount of phenolic / salt-containing wastewater; the use of noble metal catalysts is costly. Hydrotalcite (LDH) material has potential as a catalyst or carrier in oxidation reactions due to its unique layered structure, adjustable composition, and basicity.

[0003] Patent CN109046355B discloses a method for synthesizing tetramethyl diphenylquinone using copper-based hydrotalcite as a catalyst. The method uses a coprecipitation method and hydrogen peroxide as an oxidizing agent, and the reaction is carried out in an alkaline emulsion system. This method still needs to handle the emulsion system, and does not involve fine-tuning of the microstructure of the catalyst. Patents CN119140106B and CN103263915A respectively involve cerium-modified and platinum-supported hydrotalcite catalysts, but their application fields are CO2 hydrogenation and cinnamyl alcohol hydrogenation. Patent CN116747877A discloses a Pt / Ni / Fe hydrotalcite catalyst, which uses strong acid-etched activated carbon as a hard template and a carrier in the preparation process. The preparation process is complex, and the active metal is the noble metal Pt.

[0004] Therefore, it is of important industrial application value to develop a non-noble metal solid catalyst with simple preparation method, low cost, easy separation, high activity, and good selectivity for efficient oxidative coupling of 2,6-di-tert-butylphenol (2,6B) to form tetramethyl diphenylquinone. There is a lack of reports on fine-tuning of the mesostructure of CuMgAl-LDH catalyst by a soft template method to optimize its catalytic oxidative coupling performance in the prior art. SUMMARY

[0005] In view of the problems in the prior art, the application discloses a copper-magnesium-aluminum hydrotalcite catalyst for oxidative coupling of 2,6-di-tert-butylphenol to form tetra-tert-butyl diphenylquinone and a preparation method thereof.

[0006] In order to achieve the above-mentioned purposes of the application, the following technical solutions are adopted:

[0007] The first aspect of the application provides a preparation method of a copper-magnesium-aluminum hydrotalcite catalyst for oxidative coupling of 2,6-di-tert-butylphenol to form tetra-tert-butyl diphenylquinone, comprising the following steps:

[0008] (1) dissolving soluble salts of Cu, Mg and Al in water to obtain a mixed salt solution A;

[0009] (2) dissolving NaOH and / or Na2CO3 in water to obtain a base solution B;

[0010] (3) dissolving a Gemini surfactant in a mixed solvent composed of water and a lower alcohol to obtain a solution C, wherein the Gemini surfactant is a quaternary ammonium salt type Gemini surfactant with a general formula of

[0011] C n H 2n+1 N + (CH 3)2 -(CH2)S-N + (CH 3)2 C n H 2n+1 ·2Br-, wherein n = 12-16 and s = 2-4;

[0012] (4) adding the mixed salt solution A and the mixed base solution B dropwise into the solution C under continuous stirring and in a protective gas atmosphere to form a mixed slurry;

[0013] (5) subjecting the mixed slurry to ultrasonic assisted aging treatment at 60-80°C for 6-16h, then centrifugally separating, washing the solid until the filtrate is neutral, drying and grinding the solid to obtain a copper magnesium aluminum hydrotalcite catalyst.

[0014] Preferably, the molar ratio of Cu 2+ , Mg 2+ and Al 3+ in the mixed salt solution of step (1) is (0.25-1.5):5:2.

[0015] Preferably, the molar ratio of the Gemini surfactant to the total amount of Cu 2+ , Mg 2+ and Al 3+ is 0.005:1-0.10:1.

[0016] More preferably, the Gemini surfactant in step (3) is 1,2-bis(dodecyldimethylammonium)ethane dibromide (Gemini 12-2-12) with a structural formula as follows:

[0017]

[0018] Preferably, the pH value of the mixed slurry in step (4) is 9.0-10.0.

[0019] Preferably, the ultrasonic temperature in step (5) is 70°C and the time is 12h.

[0020] Preferably, the ultrasonic power in step (5) is 100-300 W, and an intermittent mode (working for 2 s and pausing for 2 s) is adopted.

[0021] Preferably, the soluble salt in step (1) is a nitrate.

[0022] Preferably, the lower alcohol in step (3) is ethanol or isopropanol, and the volume fraction of the lower alcohol in the mixed solvent is 10%-30%, and the protective gas in step (4) is nitrogen.

[0023] Preferably, the solid is washed with hot water and ethanol alternately in step (5) until the filtrate is neutral, and the drying temperature is 60-80 ℃.

[0024] The second aspect of the present application provides a copper-magnesium-aluminum hydrotalcite catalyst prepared by the preparation method of any one of the first aspect.

[0025] The third aspect of the present application provides an application of the copper-magnesium-aluminum hydrotalcite catalyst of the second aspect in catalyzing the oxidative coupling of 2,6-di-tert-butylphenol to form tetra-tert-butylbenzoquinone.

[0026] The fourth aspect of the present application provides a method for preparing tetra-tert-butylbenzoquinone by oxidative coupling of 2,6-di-tert-butylphenol, which comprises the following steps: using n-octanol as a solvent and oxygen as an oxidation source, and using the catalyst of the second aspect of the present application, and reacting at a temperature of 160-190 ℃ and an oxygen pressure of 0.35-0.75 MPa for 0.5-3 h.

[0027] Advantages:

[0028] (1) The gemini surfactant is introduced into the preparation process of the copper-magnesium-aluminum hydrotalcite in the present application, and the gemini surfactant is used as a structure directing agent (soft template). The gemini surfactant has two head groups and two chains, and its structure directing ability and self-assembly characteristics are much better than those of traditional single-chain surfactants, which can more effectively guide the growth and accumulation of hydrotalcite layers, and form more regular and looser mesoporous structures.

[0029] (2) The gemini surfactant (soft template) cooperates with ultrasonic assistance (physical field strengthening) to prepare the catalyst in the present application. The ultrasonic cavitation effect can promote the dispersion of the gemini surfactant micelles and the exertion of the template effect, and accelerate the nucleation / crystallization process at the same time, so that the metal ions are more uniformly distributed, and smaller and more regular hydrotalcite crystal plates are formed, and the surface defect sites can be possibly increased.

[0030] (3) Compared with the catalyst prepared by the ordinary coprecipitation method, the catalyst prepared by the present application has a larger specific surface area, more abundant mesoporous structures and better metal dispersity, and exposes more active sites (HO-Cu 2+-OH). When the catalyst is applied to the oxidative coupling reaction of 2,6-di-tert-butylphenol, the activity and selectivity of TBDPQ of the catalyst prepared by the present application are significantly improved compared with CuMgAl-LDH prepared by common co-precipitation method.

[0031] (4) The catalyst of the present application is a solid catalyst without noble metal, which is easy to separate and recover, avoiding the corrosion and wastewater problems of homogeneous catalysts. The preparation process has mild conditions, and the template used has better degradability than some high molecular templates. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 XRD patterns of the catalysts prepared for Example 1, Example 2 and Comparative Example 1;

[0033] Figure 2 TEM image of the CuMgAl(1:5:2)-LDH catalyst prepared for Example 1. DETAILED DESCRIPTION

[0034] The present application is further described in detail by the following examples, but the scope of protection of the present application is not limited thereto.

[0035] Example 1

[0036] A method for preparing a copper-magnesium-aluminum hydrotalcite catalyst for oxidative coupling of 2,6-di-tert-butylphenol to form tetra-tert-butyl diphenylquinone, the specific steps are as follows:

[0037] (1) 9.6 g of Cu(NO3)2·3H2O, 51.28 g of Mg(NO3)2·6H2O and 30.01 g of Al(NO3)3·9H2O were weighed and dissolved in 250 mL of deionized water to obtain a mixed salt solution A;

[0038] (2) 40 g of NaOH was weighed and dissolved in 250 mL of deionized water to obtain an alkali solution B;

[0039] (3) 1.0 g of 1,2-bis(dodecyldimethylammonium)ethane dibromide (Gemini 12-2-12) surfactant was weighed and dissolved in 150 mL of a mixed solvent of deionized water and 50 mL of ethanol to obtain solution C;

[0040] (4) Under the protection of nitrogen and vigorous stirring, the mixed salt solution A and the alkali solution B were slowly added through a constant pressure dropping funnel into the solution C to form a mixed slurry, and the pH was controlled at 9.5±0.2;

[0041] (5) After the dripping, the mixed slurry was transferred to an ultrasonic reactor and ultrasonic-assisted aging was carried out at 70°C (power 200 W, working 2 s / intermittent 2 s) for 12 hours. After the reaction was completed, the solid was centrifuged and washed with hot water at 60°C and ethanol alternately for several times until the filtrate pH was about 7 and no Br - detection (tested by AgNO3 solution), the obtained solid was dried in a 70°C oven for 12 hours, ground, and passed through a 60-mesh sieve to obtain a copper-magnesium-aluminum hydrotalcite catalyst (denoted as CuMgAl(1:5:2)-LDH catalyst).

[0042] The CuMgAl(1:5:2)-LDH catalyst was tested by the BET method, and the specific surface area thereof was 125 m 2 / g, the average pore size was 15.2 nm, and the pore volume was 0.45 cm 3 / g.

[0043] Example 2

[0044] A method for preparing a copper-magnesium-aluminum hydrotalcite catalyst for oxidatively coupling 2,6-di-tert-butylphenol to form tetra-tert-butyl diphenylquinone, and the specific steps are as follows:

[0045] (1) 4.8 g of Cu(NO3)2·3H2O, 51.28 g of Mg(NO3)2·6H2O, and 30.01 g of Al(NO3)3·9H2O were weighed and dissolved in 250 mL of deionized water to obtain a mixed salt solution A;

[0046] (2) 40 g of NaOH was weighed and dissolved in 250 mL of deionized water to obtain an alkali solution B;

[0047] (3) 1.0 g of 1,2-bis(dodecyldimethylammonium)ethane dibromide (Gemini 12-2-12) surfactant was weighed and dissolved in a mixed solvent composed of 150 mL of deionized water and 50 mL of ethanol to obtain a solution C;

[0048] (4) Under the protection of nitrogen and under vigorous stirring, the mixed salt solution A and the alkali solution B were slowly added to the solution C through a constant-pressure dropping funnel to form a mixed slurry, and the pH was controlled at 9.5±0.2;

[0049] (5) After the dripping, the mixed slurry was transferred to an ultrasonic reactor and ultrasonic-assisted aging was carried out at 70°C (power 200 W, working 2 s / intermittent 2 s) for 12 hours. After the reaction was completed, the solid was centrifuged and washed with hot water at 60°C and ethanol alternately for several times until the filtrate pH was about 7 and no Br - detection (tested by AgNO3 solution), the obtained solid was dried in a 70°C oven for 12 hours, ground, and passed through a 60-mesh sieve to obtain a copper-magnesium-aluminum hydrotalcite catalyst (denoted as CuMgAl(0.5:5:2)-LDH catalyst).

[0050] The specific surface area of the CuMgAl(0.5:5:2)-LDH catalyst was 107 m 2 / g, the average pore size was 16.7 nm, and the pore volume was 0.38 cm 3 / g.

[0051] Comparative Example 1

[0052] A method for preparing a copper-magnesium-aluminum hydrotalcite catalyst for the oxidative coupling of 2,6-di-tert-butylphenol to form tetra-tert-butyl-diphenylbenzoquinone, the specific steps being:

[0053] (1) 51.28 g of Mg(NO3)2·6H2O and 30.01 g of Al(NO3)3·9H2O were weighed and dissolved in 250 mL of deionized water to obtain a mixed salt solution A;

[0054] (2) 40 g of NaOH was weighed and dissolved in 250 mL of deionized water to obtain an alkali solution B;

[0055] (3) 1.0 g of 1,2-bis(dodecyldimethylammonium)ethane dibromide (Gemini 12-2-12) surfactant was weighed and dissolved in 150 mL of a mixed solvent of deionized water and 50 mL of ethanol to obtain solution C;

[0056] (4) Under nitrogen protection and vigorous stirring, the mixed salt solution A and the alkali solution B were slowly added through a constant pressure dropping funnel into the solution C to form a mixed slurry, and the pH was controlled at 9.5±0.2;

[0057] (5) After the dripping was completed, the mixed slurry was transferred to an ultrasonic reactor, and ultrasonic assisted aging (power 200 W, working 2 s / intermittent 2 s) was carried out at 70°C for 12 hours. After the reaction was completed, the solid was centrifuged and washed with 60°C hot water and ethanol alternately for several times until the filtrate pH≈7 and no Br - detection (tested by AgNO3 solution), the obtained solid was dried in a 70°C oven for 12 hours, ground, and passed through a 60 mesh sieve to obtain a copper-magnesium-aluminum hydrotalcite catalyst (denoted as MgAl(5:2)-LDH catalyst).

[0058] The specific surface area of the MgAl(5:2)-LDH catalyst was 98 m 2 / g, the average pore size was 17.5 nm, and the pore volume was 0.34 cm 3 / g.

[0059] Comparative Example 2

[0060] Comparative Example 2 used a co-precipitation method to prepare the catalyst without adding surfactants. Other raw materials were the same as in Example 1. The aging process was as follows: static aging in an oil bath at 80°C for 16 hours. Other treatment processes were the same as in Example 1, and CuMgAl-LDH catalyst was obtained.

[0061] The CuMgAl-LDH catalyst was tested using the BET method, and its specific surface area was 89 m². 2 / g, average pore size 8.5nm, pore volume 0.19cm³ 3 / g.

[0062] Characterization tests:

[0063] 1. XRD characterization

[0064] The catalysts prepared in Examples 1, 2, and 1 (Comparative Example 1) were characterized by XRD, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that all catalyst samples exhibit sharp and symmetrical (003) and (006) diffraction peaks at lower angles, and multiple characteristic diffraction peaks such as (012), (015), (018), (110), and (113) at higher angles. This confirms that all products have successfully formed a typical layered crystal structure of hydrotalcite. With Cu 2+ With the increase in the amount introduced and its proportion in divalent metals, the intensity of the (003) diffraction peak is significantly reduced and the full width at half maximum (FWHM) is significantly broadened, indicating that Cu 2+ The Jahn-Teller effect effectively introduces lattice distortion, thereby leading to a decrease in the crystallinity of the material.

[0065] 2. TEM characterization

[0066] The CuMgAl(1:5:2)-LDH catalyst prepared in Example 1 was characterized by TEM, and the results are as follows: Figure 2 As shown, the sample exhibits a flower-like microsphere structure assembled from ultrathin nanosheets (Fig. a). This open hierarchical structure facilitates the exposure of abundant active sites and promotes mass transfer. A high-resolution TEM image (Fig. b) clearly shows lattice fringes with a spacing of 0.382 nm, corresponding to the (006) crystal plane of the hydrotalcite mineral phase. This is corroborated by X-ray diffraction (XRD) analysis, confirming that the synthesized material possesses a highly crystalline layered structure.

[0067] 3. Catalytic performance test

[0068] The catalysts prepared by Example 1 and Comparative Example 2 were used to catalyze the oxidative coupling of 2,6-di-tert-butylphenol (2,6B) to form tetra-tert-butyl diphenyl-2,6-diphenyl-1,4-benzoquinone (TBDPQ). The specific process was as follows: 5 g of 2,6B, 60 g of n-octanol and 1.0 g of catalyst were added into a 100 mL high-pressure reactor, which was then sealed and purged with oxygen three times, and then filled with oxygen to a pressure of 0.55 MPa. The stirring was started at 1000 rpm, and the temperature was raised to 180°C for 1 hour. After the reaction was completed, the reactor was cooled, and the sample was analyzed.

[0069] The catalytic performance of the catalyst of Example 1 was as follows: the conversion rate of 2,6B was 99.5%, and the selectivity of TBDPQ was 85.7%;

[0070] The catalytic performance of the catalyst of Example 2 was as follows: the conversion rate of 2,6B was 98.2%, and the selectivity of TBDPQ was 81.2%;

[0071] The catalytic performance of the catalyst of Comparative Example 1 was as follows: the conversion rate of 2,6B was 58.2%, and the selectivity of TBDPQ was 41.3%;

[0072] The catalytic performance of the catalyst of Comparative Example 2 was as follows: the conversion rate of 2,6B was 95.3%, and the selectivity of TBDPQ was 78.3%.

[0073] The catalysts prepared by Example 1 and Example 2 using the preparation method of the present application both have good catalytic performance. As compared with the catalytic performance of the catalyst of Comparative Example 1, the catalytic activity and selectivity of the catalyst of Example 1 for the target product are both significantly better than those of Comparative Example 1, because the catalyst of Example 1 has a larger specific surface area, more abundant mesoporous structure and better metal dispersion. As compared with the catalytic performance of the catalyst of Comparative Example 2, the catalytic activity and selectivity of the catalyst prepared by the method of the present application for the target product are both better than those of the catalyst prepared by the ordinary coprecipitation method. This is attributed to the more optimal catalyst texture properties created by the synergistic effect of the gemini surfactant and ultrasonic-assisted aging.

Claims

1. A process for the preparation of a copper-magnesium-aluminum hydrotalcite catalyst for the oxidative coupling of 2,6-di-tert-butylphenol to tetra-tert- butyl-diphenylbenzoquinone, characterized in that The method comprises the following steps: (1) dissolving soluble salts of Cu, Mg and Al in water to obtain a mixed salt solution A; (2) dissolving NaOH and / or Na2CO3 in water to obtain an alkali solution B; (3) dissolving a gemini surfactant in a mixed solvent composed of water and a lower alcohol to obtain solution C, wherein the gemini surfactant is a quaternary ammonium salt type gemini surfactant with a general formula of C n H 2n+1 N + (CH 3)2 -(CH2)S-N + (CH 3)2 C n H 2n+1 ·2Br⁻, wherein n = 12-16, s = 2-4; (4) under continuous stirring and in a protective gas atmosphere, the mixed salt solution A and the mixed alkali solution B are added dropwise into the solution C to form a mixed slurry; (5) the mixed slurry is subjected to ultrasonic assisted aging treatment at 60-80℃ for 6-16 h, then centrifuged, the solid is washed until the filtrate is neutral, and the solid is dried and ground to obtain a copper magnesium aluminum hydrotalcite catalyst.

2. The production method according to claim 1, characterized by, Cu in the mixed salt solution of step (1) 2+ Mg 2+ And Al 3+ The molar ratio is (0.25~1.5):5:

2.

3. The production method according to claim 2, characterized by, Gemini surfactants and Cu 2+ , Mg 2+ and Al 3+ The molar ratio of the total amount is 0.005:1 to 0.10:

1.

4. The production method according to claim 3, characterized by, In step (4), the pH value of the mixed slurry is 9.0-10.

0.

5. The preparation method according to claim 4, characterized in that, In step (5), the ultrasonic power is 100-300 W.

6. The preparation method according to claim 2, characterized in that, In step (1), the soluble salts are nitrate salts.

7. The production method according to claim 6, wherein In step (3), the lower alcohol is ethanol or isopropanol, and the volume fraction of the lower alcohol in the mixed solvent is 10%-30%, and in step (4), the protective gas is nitrogen.

8. The copper magnesium aluminum hydrotalcite catalyst prepared by the preparation method according to any one of claims 1-7.

9. The application of the copper magnesium aluminum hydrotalcite catalyst according to claim 8 in catalyzing the oxidative coupling of 2,6-di-tert-butylphenol to form tetra-tert-butylbenzoquinone.

10. A process for the oxidative coupling of 2,6-di-tert-butylphenol to tetra-tert- butyl-diphenoquinone, characterized in that, The method comprises the following steps: The catalyst according to claim 8 is used in a reaction at a temperature of 160-190℃, an oxygen pressure of 0.35-0.75 MPa, and for 0.5-3 h with n-octanol as a solvent and oxygen as an oxidation source.

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