A method for preparing alpha-h methyl substituted monophenol by catalyzing carbon dioxide hydrogenation and methylating phenol

Abstract

The application discloses a method for preparing alpha-H methyl-substituted monophenol by catalyzing carbon dioxide hydrogenation and methylating phenol, and specifically comprises the following steps: taking a phenolic compound as a starting raw material, and under the action of an M-ZrO2-In2O3 catalyst, carbon dioxide is hydrogenated to generate a high-activity CH3O* free radical and methylate the phenolic compound to prepare an alpha-H methyl-substituted monophenol compound, wherein M in the catalyst is one or more metals selected from Cu, Ni, Co and Fe and / or metal oxides thereof, and the catalyst is prepared by using a low-temperature reduction method; the conversion rate of the raw material and the selectivity of the product both reach more than 99%; the method can realize carbon dioxide conversion and solidification and prepare high-value chemicals, and has good application prospect and social significance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysis, and particularly relates to a method for synthesizing alpha-H methyl-substituted monophenol compounds by catalyzing carbon dioxide hydrogenation and methylating phenols. BACKGROUND

[0002] With the continuous advancement of industrialization, more and more energy is consumed. At present, the energy of the whole world mainly comes from fossil fuels, and a large amount of carbon dioxide and harmful gases are emitted in the process of exploitation and use, which causes various harmful effects on the living environment of human beings. How to reduce the carbon dioxide emissions caused by human activities has become one of the widely concerned hotspots in recent years. However, the carbon dioxide molecule itself is a linear symmetrical conjugated double bond structure, which determines that the carbon dioxide molecule structure has quite high stability, and the carbon dioxide hydrogenation reaction is a thermodynamically unfavorable reaction. The reaction process will release heat, and needs to overcome the increase of entropy, so that the conversion of carbon dioxide generally needs relatively harsh reaction conditions. At present, the conversion of carbon dioxide mainly has two kinds: hydrogenation to prepare methanol [patent 1 CN202310758842.2] or formic acid [patent 2 CN202310758842.2] and direct carbonylation coupling reaction [literature 1 J. Am. Chem. Soc 2002, 124, 11379], which can be realized by adjusting the composition and structure performance of the catalyst, and is a very promising carbon sequestration and carbon dioxide emission reduction scheme, but the conversion process has problems such as low added value of products or harsh reaction system conditions. Therefore, how to develop a new efficient method for converting carbon dioxide and generating high-value chemicals still has challenges.

[0003] In view of the difficulty of high thermodynamic energy barrier of carbon dioxide hydrogenation, many scholars choose to combine carbon dioxide conversion with other types of reactions, and fix carbon dioxide with high reaction activity molecules to promote the forward movement of carbon dioxide hydrogenation reaction, such as literature 2 [Sci. Adv. 2021, eabi6012] carbon dioxide is fixed on ZnZrO xThe methoxy intermediates generated by the hydrogenation of the solid solution are diffused onto the ZSM-5 to undergo electrophilic substitution with toluene to generate dimethylbenzene. Compared with directly using methanol as an alkylation reagent, the selectivity is increased by 1.5 times. Literature 3 [Angew Chem Int Ed Engl.2023,61,10] reports that the CuFeCr catalyst prepared by coprecipitation can convert carbon dioxide and PET into 1,4-cyclohexanedicarboxylic acid dimethyl ester and p-xylene in one step, with a total yield of up to 80%. Biomass, as the only renewable carbon resource that can replace fossil energy, has attracted more and more attention. In recent years, many scholars have also begun to focus on coupling carbon dioxide with biomass platform molecules to prepare high-value chemicals. For example, furfural [literature 4 Nature 2016, 531, 215], alkyl phenol [literature 5 Chem. Eur. J. 2016, 22, 6798] and guaiacol [literature 6 Sci. Adv. 2023, 9, eadf2966] are used as starting materials to react with carbon dioxide to obtain 2,5-furandicarboxylic acid, salicylic acid derivatives and veratric acid, respectively. SUMMARY

[0004] The present application provides a method for catalyzing the hydrogenation of carbon dioxide and the methylation of phenols to prepare alpha-H methyl-substituted monophenols. The catalyst is composed of metal M (Cu, Ni, Co, Fe) and / or its oxides and ZrO2 and In2O3. It is simultaneously applied to the hydrogenation of carbon dioxide and the methylation of phenols. The high activity of CH3O* free radicals generated during the hydrogenation of carbon dioxide is used to methylate monophenols to prepare high-value alpha-H methyl-substituted monophenol compounds.

[0005] Technical solutions of the present application:

[0006] A method for catalyzing the hydrogenation of carbon dioxide and the methylation of phenols to prepare alpha-H methyl-substituted monophenols. M-ZrO2-In2O3 is used as a catalyst to prepare alpha-H methyl-substituted monophenol compounds by one-pot hydrogenation of carbon dioxide and methylation of phenols. The reaction formula is shown as formula (1), wherein M is one or more metals selected from Cu, Ni, Co and Fe and / or metal oxides thereof.

[0007]

[0008] In formula (1), R1 is H or -OCH3, and R2 is H or CH3.

[0009] The present application takes phenolic compounds as starting materials, designs and prepares high-activity catalysts to make carbon dioxide hydrogenation and methylate phenols to prepare high-value chemicals, which not only affects the phenolic hydroxyl group and benzene ring functional group, but also realizes the conversion of carbon dioxide and the methylation of phenolic compounds. Therefore, the present application designs M-ZrO2-In2O3 catalyst, wherein M is one or more metals selected from Cu, Ni, Co and Fe and / or metal oxides thereof, and innovatively utilizes the CH3O* high-activity free radicals generated by carbon dioxide hydrogenation to methylate the alpha-H in phenolic compounds through C-C bond coupling reaction to prepare alpha-H methyl-substituted monophenol compounds, and the conversion rate of raw materials and the selectivity of products both reach more than 99%.

[0010] Further, in the M-ZrO2-In2O3 catalyst, the molar ratio of M / In2O3 is 0.3-1.5:1, and the molar ratio of ZrO2 / In2O3 is 0.3-1.5:1.

[0011] Further, the preparation of the M-ZrO2-In2O3 catalyst adopts an alkali precipitation method, specifically, M salt, Zr salt and In salt are precipitated by alkali, and then filtration separation, calcination and hydrogen reduction are performed.

[0012] Further, the alkali is one or more selected from NaOH, KOH, NaHCO3 and NH3·H2O, and the M salt, Zr salt and In salt are nitrate, acetate, chloride or sulfate thereof.

[0013] Further, the calcination temperature is 300-600 DEG C, and the calcination time is 1-5 h.

[0014] Further, the hydrogen reduction temperature is 50-200 DEG C, and the reduction time is 0.5-6 h.

[0015] Further, the temperature of carbon dioxide hydrogenation and methylation of phenols is 200-300 DEG C, the reaction pressure is 1-6 MPa, the volume ratio of hydrogen / carbon dioxide is 1-3:1, the solvent is C6-C 16 Straight-chain alkanes or cycloalkanes.

[0016] The present application has the following beneficial effects:

[0017] 1. In the preparation process of the catalyst of the present application, the precursors are reduced by hydrogen at a lower temperature, which can avoid the agglomeration of components at high temperature, promote the uniform dispersion of components, and better match the hydroxyl oxygen and oxygen vacancy number on the catalyst, promote the effective proportional adsorption of carbon dioxide and phenolic compounds on the surface of the catalyst, and make the intermediate after carbon dioxide hydrogenation immediately methylate the nearby adsorbed monophenolic compounds.

[0018] 2, The application innovatively uses CH3O* high-activity free radicals generated by carbon dioxide hydrogenation to prepare alpha-H methyl-substituted monophenol compounds by C-C bond coupling reaction of methylization of alpha-H in phenolic compounds, and the conversion rate of raw materials and the selectivity of products reach more than 99%.

[0019] 3, The application not only converts and solidifies carbon dioxide, but also methylates phenolic compounds to prepare high-value alpha-H methyl-substituted monophenol compounds, and has good application prospect and social significance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 CuO used in Example 1 of the application 1-x X-ray powder diffraction pattern of the ZrO2-In2O3 catalyst, wherein CuO 1-x Cu represents that Cu exists in the form of a mixture of Cu2O and CuO. DETAILED DESCRIPTION

[0021] In order to make the application clearer, the application will be further described below in conjunction with examples. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the application.

[0022] Example 1

[0023] Cu (NO3)2·3H2O, Zr (NO3)2·5H2O and 1.5g In (NO3)3·9H2O were weighed according to the molar ratio of M / In2O3 of 0.7 and the molar ratio of ZrO2 / In2O3 of 1.5, dissolved in 20mL distilled water, and 2.0g NaOH was dissolved in 50mL deionized water. Both were simultaneously dropped into a reaction container and stirred vigorously. The reaction temperature was 30℃. After the reaction, the precipitate was separated by filtration, dried, calcined at 500℃ for 4h, and then reduced at 100℃ in a hydrogen atmosphere for 1h to obtain the catalyst.

[0024] In a high-pressure reaction kettle, 15g n-undecane, 0.4g phenol and 0.1g of the above-mentioned catalyst were added. The air in the kettle was removed by displacement method, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 3, the total pressure was 4MPa, then the temperature was raised to 250℃, the rotation speed was adjusted to 900rpm / min, and the reaction was continued for 15h. The conversion rate of phenol was 100%, the selectivity of 2,6-dimethylphenol was more than 99%, and the activity of the catalyst remained basically unchanged after 6 cycles of reaction.

[0025] Example 2

[0026] Cu(NO3)2*3H2O, Zr(NO3)2*5H2O, 1.5g In(NO3)3*9H2O were weighed according to the molar ratio of M / In2O3 1.0 and ZrO2 / In2O3 0.3, dissolved in 20 mL distilled water, the above solution and ammonia were simultaneously dropped into the reaction container with vigorous stirring, the reaction temperature was 10°C, after the reaction was completed, the precipitate was separated by filtration, dried, calcined at 300°C for 5h, then reduced in hydrogen atmosphere at 250°C for 0.5h to obtain the catalyst.

[0027] In a high-pressure reactor, 15g n-undecane, 0.4g 4-methylphenol, 0.1g of the above catalyst were added, the air in the reactor was removed by displacement method, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 1, the total pressure was 6MPa, then the temperature was raised to 300°C, the rotation speed was adjusted to 900rpm / min, after 15h of reaction, the conversion rate of 4-methylphenol was 100%, the selectivity of 2,4,6-trimethylphenol was more than 99%, after 6 cycles of reaction, the activity of the catalyst remained basically unchanged.

[0028] Example 3

[0029] Cu(NO3)2*3H2O, Zr(NO3)2*5H2O, 1.5g In(NO3)3*9H2O were weighed according to the molar ratio of M / In2O3 1.0 and ZrO2 / In2O3 0.3, dissolved in 20 mL distilled water, the above solution and ammonia were simultaneously dropped into the reaction container with vigorous stirring, the reaction temperature was 10°C, after the reaction was completed, the precipitate was separated by filtration, dried, calcined at 300°C for 5h, then reduced in hydrogen atmosphere at 250°C for 0.5h to obtain the catalyst.

[0030] In a high-pressure reactor, 15g n-undecane, 0.4g guaiacol, 0.1g of the above catalyst were added, the air in the reactor was removed by displacement method, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 3, the total pressure was 1MPa, then the temperature was raised to 300°C, the rotation speed was adjusted to 900rpm / min, after 15h of reaction, the conversion rate of guaiacol was 100%, the selectivity of 2,6-dimethylphenol was more than 99%, after 6 cycles of reaction, the activity of the catalyst remained basically unchanged.

[0031] Example 4

[0032] Ni(CH3COO)2-3H2O, Zr(NO3)2-5H2O, 1.5 g In(NO3)3-9H2O were dissolved in 20 mL distilled water with M / In2O3 molar ratio of 0.3 and ZrO2 / In2O3 molar ratio of 1.5, and 2.0 g NaHCO3 was dissolved in 50 mL deionized water, which were simultaneously dropped into the reaction vessel with vigorous stirring. The reaction temperature was 80 °C. After the reaction, the precipitate was separated by filtration, dried, calcined at 400 °C for 5 h, and then reduced at 250 °C in hydrogen atmosphere for 3 h to obtain the catalyst.

[0033] In a high-pressure reactor, 15 g n-undecane, 0.4 g 4-methylguaiacol, and 0.1 g of the above catalyst were added, the air in the reactor was removed by displacement method, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 2, the total pressure was 5 MPa, then the temperature was raised to 200 °C, the rotation speed was adjusted to 900 rpm / min, and the reaction was continued for 15 h. The conversion of 4-methylguaiacol was 100%, the selectivity of 2,4,6-trimethylphenol was more than 99%, and the activity of the catalyst remained basically unchanged after 6 cycles of reaction.

[0034] Example 5

[0035] FeSO4-7H2O, Zr(NO3)2-5H2O, 1.5 g In(NO3)3-9H2O were dissolved in 20 mL distilled water with M / In2O3 molar ratio of 0.5 and ZrO2 / In2O3 molar ratio of 1.5, and 2.0 g NaOH was dissolved in 50 mL deionized water, which were simultaneously dropped into the reaction vessel with vigorous stirring. The reaction temperature was 30 °C. After the reaction, the precipitate was separated by filtration, dried, calcined at 400 °C for 5 h, and then reduced at 250 °C in hydrogen atmosphere for 6 h to obtain the catalyst.

[0036] In a high-pressure reactor, 15 g n-undecane, 0.4 g phenol, and 0.1 g of the above catalyst were added, the air in the reactor was removed by displacement method, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 2, the total pressure was 4 MPa, then the temperature was raised to 250 °C, the rotation speed was adjusted to 900 rpm / min, and the reaction was continued for 15 h. The conversion of phenol was 100%, the selectivity of 2,6-dimethylphenol was more than 99%, and the activity of the catalyst remained basically unchanged after 6 cycles of reaction.

[0037] Example 6

[0038] CuCl2-2H2O, Zr(NO3)2-5H2O, 1.5g In(NO3)3-9H2O were weighed according to the molar ratio of M / In2O3 0.7 and ZrO2 / In2O3 1.4, dissolved in 20 mL distilled water, and the above solution and ammonia were simultaneously dropped into the reaction container and stirred vigorously. The reaction temperature was 30°C. After the reaction, the precipitate was separated by filtration, dried, calcined at 500°C for 3h, and then reduced at 50°C in a hydrogen atmosphere for 6h to obtain the catalyst.

[0039] In a high-pressure reaction kettle, 15g n-undecane, 0.4g 4-methylphenol, and 0.1g of the above catalyst were added. The air in the kettle was removed by displacement, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 3, the total pressure was 4MPa, then the temperature was raised to 250°C, the rotation speed was adjusted to 900rpm / min, and the reaction was continued for 15h. The conversion rate of 4-methylphenol was 100%, the selectivity of 2,4,6-trimethylphenol was greater than 99%, and the activity of the catalyst remained basically unchanged after 6 cycles of reaction.

[0040] Example 7

[0041] Cu(NO3)2-3H2O, Zr(NO3)2-5H2O, 1.5g In(NO3)3-9H2O were weighed according to the molar ratio of M / In2O3 1.5 and ZrO2 / In2O3 1.0, dissolved in 20 mL distilled water, and 2.0g NaOH was dissolved in 50 mL deionized water. Both were simultaneously dropped into the reaction container and stirred vigorously. The reaction temperature was 40°C. After the reaction, the precipitate was separated by filtration, dried, calcined at 600°C for 2h, and then reduced at 150°C in a hydrogen atmosphere for 1h to obtain the catalyst.

[0042] In a high-pressure reaction kettle, 15g n-undecane, 0.4g 3-methylphenol, and 0.1g of the above catalyst were added. The air in the kettle was removed by displacement, carbon dioxide and hydrogen were introduced, the volume ratio of hydrogen to carbon dioxide was 3, the total pressure was 4MPa, then the temperature was raised to 250°C, the rotation speed was adjusted to 900rpm / min, and the reaction was continued for 15h. The conversion rate of 3-methylphenol was 100%, the selectivity of 2,3,6-trimethylphenol was greater than 99%, and the activity of the catalyst remained basically unchanged after 6 cycles of reaction.

[0043] Comparative Example 1

[0044] The same as Example 1, except that the catalyst was CuO 1-x -In2O3.

[0045] Under the same reaction conditions, the conversion rate of phenol was 83%, and the selectivity of 2,6-dimethylphenol was 58%.

[0046] Comparative Example 2

[0047] As in Example 3, except that the catalyst is CuO 1-x - ZrO2.

[0048] Under the same reaction conditions, the conversion of guaiacol is 43% and the selectivity to 2,6-dimethylphenol is 30%. Comparative Example 3

[0049] As in Example 1, except that the catalyst is ZrO2-In2O3.

[0050] Under the same reaction conditions, the conversion of phenol is 48% and the selectivity to 2,6-dimethylphenol is 18%.

Claims

1. A method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide, characterized in that: Using M-ZrO2-In2O3 as a catalyst, carbon dioxide is hydrogenated and methylated to prepare phenolic compounds in one pot. The reaction formula is shown in formula (1), where M is an oxide of one or more metals selected from Cu, Ni, Co, and Fe. ； Formula (1) Wherein, R1 is H or -OCH3, and R2 is H or CH3.

2. The method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide according to claim 1, characterized in that: In the M-ZrO2-In2O3 catalyst, the M / In2O3 molar ratio is 0.3~1.5:1, and the ZrO2 / In2O3 molar ratio is 0.3~1.5:

1.

3. The method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide according to claim 1, characterized in that: The M-ZrO2-In2O3 catalyst is prepared by an alkali precipitation method, specifically, M salt, Zr salt and In salt are precipitated by alkali, and then separated by filtration, calcined and reduced with hydrogen to obtain the catalyst.

4. The method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide according to claim 3, characterized in that: The base is one or more of NaOH, KOH, NaHCO3, and NH3·H2O, and the M salt, Zr salt, and In salt are all nitrates, acetates, chlorides, or sulfates thereof.

5. The method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide according to claim 3, characterized in that: The calcination temperature is 300~600 °C, and the calcination time is 1~5 h.

6. The method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide according to claim 3, characterized in that: The temperature of hydrogen reduction is 50~200 °C, and the reduction time is 0.5~6 h.

7. The method for preparing α-H methyl-substituted monophenols by catalytically hydrogenating and methylating phenols with carbon dioxide according to any one of claims 1 to 6, characterized in that: The temperature of the carbon dioxide hydrogenation and methylation reaction of phenols is 200-300 ° C, the reaction pressure is 1-6 MPa, and the volume ratio of hydrogen to carbon dioxide is 1-3:1; the reaction is carried out in a solvent, and the solvent is C6-C 16 Straight-chain alkanes or cycloalkanes.

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