Preparation method and application of a supported Co-Fe bimetallic catalyst

Abstract

This invention discloses a method for preparing a supported Co-Fe bimetallic catalyst and its application, relating to the field of catalyst preparation technology. The method includes the following steps: preparing a TiO2 / Al2O3 composite support; modifying the TiO2 / Al2O3 composite support with Nb2O5; and loading Co-Fe onto the modified TiO2 / Al2O3 composite support via impregnation to obtain the supported Co-Fe bimetallic catalyst. The catalyst is used for the hydrogenation deoxygenation of vanillin to prepare 2-methoxy-4-methylphenol. The preparation method disclosed in this invention yields a low-cost, economical, effective, universally applicable, environmentally friendly, and non-corrosive catalyst. Nb2O5 modification promotes the interaction between the Co-Fe active component and the support surface, preventing the loss of active components during the reaction and improving catalyst stability, thereby enhancing the catalyst's catalytic performance. Applied to the vanillin hydrogenation deoxygenation process, it can improve the yield of 2-methoxy-4-methylphenol under relatively mild reaction conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a preparation method and application of a supported Co-Fe bimetallic catalyst. Background Art

[0002] Bio-oil derived from lignin is limited in its industrial application due to its high viscosity, low calorific value and strong corrosiveness. In order to effectively improve the quality of lignin-derived bio-oil, catalytic hydrogenation and deoxygenation can be used. Vanillin has a variety of different CO / C=O bonds (Caryl-OH, Caryl-OCH3, Calkyl-OAr and C=O), and is a typical lignin-derived platform compound. A series of high value-added chemicals can be prepared by hydrogenation and deoxygenation of vanillin, such as 2-methoxy-4-methylphenol, benzene, and phenol. Among them, 2-methoxy-4-methylphenol is a high value-added biofuel and an important flavor precursor, which can be used to produce flavors and drugs with antibacterial and insecticidal properties. The preparation of 2-methoxy-4-methylphenol by hydrogenation and deoxygenation of vanillin is extremely challenging, and its reaction process includes hydrogenation of aromatic rings, hydrogenation of C=O bonds, and selective hydrogenolysis of oxygen-containing functional groups. Therefore, the key to preparing 2-methoxy-4-methylphenol by hydrodeoxygenation of vanillin is to prepare a high-performance hydrodeoxygenation catalyst.

[0003] In recent years, researchers have developed noble metal catalysts (e.g., Au, Pt, Pd, and Ru) for the hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol. Noble metal catalysts exhibit excellent catalytic activity, but their high cost and scarce resources greatly limit their large-scale application in industry. Therefore, the search for a cheap, highly active, highly selective, and highly stable catalyst for the catalytic hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol has attracted widespread attention. Although the single metal Co-based catalyst is low in cost, the hydrodeoxygenation activity is not ideal and the selectivity needs to be improved, and the stability of the single metal Ni-based and Co-based catalysts has always been a problem to be solved. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a preparation method and application of a supported Co-Fe bimetallic catalyst, and the specific technical scheme is as follows:

[0005] A method for preparing a supported Co-Fe bimetallic catalyst comprises the following steps:

[0006] Step 1: Preparation of TiO2 / Al2O3 composite carrier;

[0007] Step 2: modifying the TiO2 / Al2O3 composite support prepared in step 1 by Nb2O5;

[0008] Step 3: The TiO2 / Al2O3 composite carrier modified in step 2 is loaded with Co-Fe by an impregnation method to obtain the loaded Co-Fe bimetallic catalyst.

[0009] Preferably, step 1 specifically includes the following sub-steps:

[0010] Step 11: Dissolve Ti(SO4)2 in deionized water;

[0011] Step 12: calcining Al2O3 at 550-600°C and adding it to the product obtained in step 11, and adjusting the pH to 7-9;

[0012] Step 13: The product obtained in step 12 is centrifuged and washed, and then calcined at 550-600° C. for 5 h to obtain the TiO2 / Al2O3 composite carrier.

[0013] Preferably, step 2 specifically includes the following sub-steps:

[0014] Step 21: Add Nb(HC2O4)5 and TiO2 / Al2O3 composite carrier into distilled water and disperse them evenly;

[0015] Step 22: centrifuge the product obtained in step 21 and dry it for 12 hours;

[0016] Step 23: calcine the product obtained in step 22 at 350-400°C for 2h to obtain the Nb2O5-modified TiO2 / Al2O3 composite carrier.

[0017] Preferably, step 3 specifically includes the following sub-steps:

[0018] Step 31: Dissolve Co(NO3)2·6H2O and Fe(NO3)3·9H2O in water, then add the TiO2 / Al2O3 composite carrier modified in step 2, disperse evenly and immerse for 12 hours;

[0019] Step 32: centrifuge the product obtained in step 31 and dry it for 12 hours;

[0020] Step 33: heating the product obtained in step 32 to 300-400° C. under a nitrogen atmosphere and calcining for 3 h;

[0021] Step 34: Maintaining the temperature, the product obtained in step 33 is reduced under a hydrogen atmosphere for 3 hours;

[0022] Step 35: The product obtained in step 34 is transferred to a nitrogen atmosphere and cooled to room temperature to obtain the supported Co-Fe bimetallic catalyst.

[0023] Preferably:

[0024] In step 21, the dispersion method is stirring dispersion, and the stirring time is 12 hours;

[0025] The drying temperature in step 22 is 120°C.

[0026] Preferably:

[0027] In step 31, the dispersion method is ultrasonic dispersion, and the dispersion time is 10 minutes;

[0028] The drying temperature in step 32 is 100°C.

[0029] Preferably, step 33 specifically includes the following sub-steps:

[0030] Step 331: placing the product obtained in step 32 in a tube furnace, and heating the temperature to 300-400° C. at a heating rate of 5° C. / min under a nitrogen atmosphere;

[0031] Step 332: Maintain the temperature and calcine for 3 hours.

[0032] The present invention also provides an application of a supported Co-Fe bimetallic catalyst, wherein the supported Co-Fe bimetallic catalyst prepared by any of the preparation methods described above is used for the hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol.

[0033] Preferably, the preparation of 2-methoxy-4-methylphenol by hydrodeoxygenation of vanillin specifically comprises the following steps:

[0034] Step 10: Add 1,4-dioxane, vanillin and the supported Co-Fe bimetallic catalyst into a high-pressure reactor, seal it, and replace the air in the reactor with hydrogen for 4 to 5 times;

[0035] Step 20: After the kettle is evacuated, the temperature is raised to 80-100° C., the pressure in the kettle is adjusted to 1.0-1.2 MPa, and the reaction is stirred for 6 hours;

[0036] Step 30: After the reaction is completed, the autoclave is placed in a cold water bath to cool to room temperature, the reaction liquid in the autoclave is taken out, and the 2-methoxy-4-methylphenol is obtained after filtering.

[0037] Preferably, the stirring method in step 20 is magnetic stirring.

[0038] The preparation method and application of the supported Co-Fe bimetallic catalyst provided by the present invention have the following beneficial effects:

[0039] 1. Low cost, economical and effective, universal, environmentally friendly, and non-corrosive to equipment;

[0040] 2. The interaction between the Co-Fe active components and the support surface is promoted by Nb2O5 modification, thereby preventing the loss of active components during the reaction and improving the stability of the catalyst;

[0041] 3. An innovative idea was proposed to use a Nb2O5-modified TiO2 / Al2O3-supported Co-Fe bimetallic catalyst for the hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol;

[0042] 4. After Nb2O5 modification, the electronic interaction between the Co-Fe active component and the carrier is promoted, thereby improving the catalytic performance of the catalyst. The acid site of the carrier promotes the removal of oxygen-containing functional groups during the hydrodeoxygenation of vanillin. It can be applied to the hydrodeoxygenation process of vanillin to increase the yield of 2-methoxy-4-methylphenol under relatively mild reaction conditions. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below. The description in this section is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0044] This embodiment provides a method for preparing a supported Co-Fe bimetallic catalyst, comprising the following steps:

[0045] Step 1: Preparation of TiO2 / Al2O3 composite carrier.

[0046] Step 2: The TiO2 / Al2O3 composite carrier prepared in step 1 is modified by Nb2O5.

[0047] Step 3: The TiO2 / Al2O3 composite carrier modified in step 2 is loaded with Co-Fe by an impregnation method to obtain a loaded Co-Fe bimetallic catalyst.

[0048] The supported Co-Fe bimetallic catalyst prepared by the preparation method provided in this embodiment has the following beneficial effects:

[0049] 1. Low cost, economical and effective, universal, environmentally friendly, and non-corrosive to equipment;

[0050] 2. Nb2O5 modification promotes the interaction between the Co-Fe active components and the support surface, thereby preventing the loss of active components during the reaction and improving the stability of the catalyst.

[0051] Furthermore, step 1 specifically includes the following sub-steps:

[0052] Step 11: Dissolve Ti(SO4)2 in deionized water.

[0053] Step 12: calcine Al2O3 at 550-600°C and add it to the product obtained in step 11, and adjust the pH to 7-9.

[0054] Step 13: After centrifugal washing, the product obtained in step 12 is calcined at 550-600°C for 5h to obtain a TiO2 / Al2O3 composite carrier.

[0055] Furthermore, step 2 specifically includes the following sub-steps:

[0056] Step 21: Add Nb(HC2O4)5 and TiO2 / Al2O3 composite carrier into distilled water and disperse evenly.

[0057] Step 22: The product obtained in step 21 was centrifuged and dried for 12 hours.

[0058] Step 23: calcine the product obtained in step 22 at 350-400°C for 2h to obtain a TiO2 / Al2O3 composite carrier modified by Nb2O5.

[0059] Furthermore, step 3 specifically includes the following sub-steps:

[0060] Step 31: Dissolve Co(NO3)2·6H2O and Fe(NO3)3·9H2O in water, then add the TiO2 / Al2O3 composite carrier modified in step 2, disperse evenly and soak for 12 hours.

[0061] Step 32: The product obtained in step 31 was centrifuged and dried for 12 hours.

[0062] Step 33: The product obtained in step 32 is heated to 300-400° C. under a nitrogen atmosphere and then calcined for 3 hours.

[0063] Step 34: Maintaining the temperature, the product obtained in step 33 is reduced under a hydrogen atmosphere for 3 h.

[0064] Step 35: The product obtained in step 34 is transferred to a nitrogen atmosphere and cooled to room temperature to obtain a supported Co-Fe bimetallic catalyst.

[0065] Further:

[0066] The dispersion method in step 21 is stirring dispersion, and the stirring time is 12 hours.

[0067] The drying temperature in step 22 is 120°C.

[0068] Further:

[0069] In step 31, the dispersion method is ultrasonic dispersion, and the dispersion time is 10 minutes.

[0070] The drying temperature in step 32 is 100°C.

[0071] Furthermore, step 33 specifically includes the following sub-steps:

[0072] Step 331: Place the product obtained in step 32 in a tube furnace and heat it to 300-400° C. at a heating rate of 5° C. / min under a nitrogen atmosphere.

[0073] Step 332: Maintain the temperature and calcine for 3 hours.

[0074] This embodiment also provides an application of a supported Co-Fe bimetallic catalyst, wherein the supported Co-Fe bimetallic catalyst prepared by any of the preparation methods described above is used for the hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol.

[0075] The supported Co-Fe bimetallic catalyst provided in this embodiment is used for the hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol, which has the following beneficial effects:

[0076] 1. An innovative idea was proposed to use a Nb2O5-modified TiO2 / Al2O3-supported Co-Fe bimetallic catalyst for the hydrodeoxygenation of vanillin to prepare 2-methoxy-4-methylphenol;

[0077] 2. After Nb2O5 modification, the electronic interaction between the Co-Fe active component and the carrier is promoted, thereby improving the catalytic performance of the catalyst. The acid site of the carrier promotes the removal of oxygen-containing functional groups during the hydrodeoxygenation of vanillin. It can be applied to the hydrodeoxygenation process of vanillin to increase the yield of 2-methoxy-4-methylphenol under relatively mild reaction conditions.

[0078] Furthermore, the preparation of 2-methoxy-4-methylphenol by hydrodeoxygenation of vanillin specifically comprises the following steps:

[0079] Step 10: Add 1,4-dioxane, vanillin and a supported Co-Fe bimetallic catalyst into a high-pressure reactor, seal it, and replace the air in the reactor with hydrogen for 4 to 5 times.

[0080] Step 20: After evacuating the autoclave, heat it to 80-100°C, adjust the pressure in the autoclave to 1.0-1.2 MPa, and stir the reaction for 6 hours.

[0081] Step 30: After the reaction is completed, place the autoclave in a cold water bath to cool to room temperature, take out the reaction liquid in the autoclave, and filter it to obtain 2-methoxy-4-methylphenol.

[0082] Furthermore, the stirring method in step 20 is magnetic stirring.

[0083] Specific examples are provided below. The provided examples may enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0084] Example:

[0085] Weigh 24 g of titanium sulfate, dissolve it in deionized water, add 10.2 g of Al2O3 calcined at 600°C to the titanium sulfate solution, adjust the pH value to 9, centrifuge and wash, transfer the solid to a muffle furnace, and calcine at 600°C for 5 hours to obtain a TiO2 / Al2O3 composite carrier;

[0086] First, 53.8 g of niobium oxalate was dissolved in distilled water as a precursor, and then 15 g of TiO2 / Al2O3 composite carrier was dispersed in the above solution. After stirring for 12 hours, it was dried in an oven at 120°C for 12 hours, and the dried solid powder was calcined in a muffle furnace at 350°C for 2 hours.

[0087] The Nb2O5-modified TiO2 / Al2O3 carrier prepared above was loaded with Co-Fe by impregnation method. 1.5 g of the Nb2O5-modified TiO2 / Al2O3 carrier was weighed in a 50 ml beaker. A certain amount of cobalt nitrate hexahydrate and ferric nitrate nonahydrate were weighed, dissolved in 5 ml of distilled water, and added to the beaker containing the Nb2O5-modified TiO2 / Al2O3 carrier. The beaker was ultrasonicated in an ultrasonicator for 10 min, impregnated for 12 h, and then dried in a drying oven at 100°C for 12 h.

[0088] The obtained catalyst precursor was calcined in a tubular furnace under nitrogen conditions, and the temperature was increased to 400°C at a heating rate of 5°C / min;

[0089] The second stage is calcined in a tube furnace at 400°C for 3h;

[0090] The third stage is reduction at 400°C for 3 h under hydrogen conditions in a tubular furnace;

[0091] In the fourth stage, the temperature was lowered to room temperature under nitrogen protection to obtain Co-Fe / Nb2O5@TiO2 / Al2O3 catalyst.

[0092] In a high-pressure reactor with a 50 ml liner, add 10 g of 1,4-dioxane and 1.0 g of vanillin as a reactant, then add 0.1 g of the prepared catalyst, and then put in a magnet;

[0093] After the kettle is sealed, the air in the kettle is replaced with hydrogen 4 times, and then the kettle is evacuated with a vacuum pump, and the kettle is placed in the jacket of an electric heating kettle for heating;

[0094] When the temperature in the autoclave reaches the specified reaction temperature, open the main valve and the air inlet valve of the hydrogen cylinder, increase the pressure to the reaction pressure of 1.0 MPa, and record the reaction start time;

[0095] After 6 hours, the reaction was completed, the electric heating kettle and the main valve of the hydrogen cylinder were closed, and the reactor was placed in a cold water bath to cool to room temperature;

[0096] Take out the cooled reaction solution, filter and quantify;

[0097] Take appropriate amounts of the reaction solution respectively, and use gas chromatography to perform qualitative and quantitative analysis on the products.

[0098] The results are as follows:

[0099] The reaction was carried out at 100°C and 1.0 MPa for 4 hours, and the conversion rate of vanillin was 66.3% and the selectivity of 2-methoxy-4-methylphenol was 76.1%.

[0100] The reaction was carried out at 100°C and 1.0 MPa for 5 hours, and the conversion rate of vanillin was 86.7% and the selectivity of 2-methoxy-4-methylphenol was 91.2%.

[0101] The reaction was carried out at 100°C and 1.0 MPa for 6 hours, with a vanillin conversion rate of 100% and a 2-methoxy-4-methylphenol selectivity of 99.6%.

[0102] Principle description:

[0103] After Nb2O5 modification, the electronic interaction between the Co-Fe active components and the support was promoted, thereby improving the catalytic performance of the catalyst. The acid sites of the support promoted the removal of oxygen-containing functional groups during the hydrodeoxygenation of vanillin.

[0104] The principles and implementation methods of the present invention are described herein using specific examples, and the description of the above embodiments is only used to help understand the method and core ideas of the present invention. The above are only preferred implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention, which should be within the protection scope of the present invention.

Claims

1. A method for preparing a supported Co-Fe bimetallic catalyst, characterized in that: The steps include: S1: Preparation of TiO2 / Al2O3 composite support; S2: modifying the TiO2 / Al2O3 composite support obtained in step S1 by Nb2O5; S3: The TiO2 / Al2O3 composite carrier modified in step S2 is loaded with Co-Fe by an impregnation method to obtain the loaded Co-Fe bimetallic catalyst.

2. The preparation method according to claim 1, characterized in that: Step S1 specifically includes the following sub-steps: S11: dissolving Ti(SO4)2 in deionized water; S12: calcining Al2O3 at 550-600°C and adding it to the product obtained in step S11, and adjusting the pH to 7-9; S13: The product obtained in step S12 is centrifugally washed and then calcined at 550-600° C. for 5 h to obtain the TiO 2 / Al 2 O 3 composite carrier.

3. The preparation method according to claim 1, characterized in that: Step S2 specifically includes the following sub-steps: S21: Add Nb(HC2O4)5 and TiO2 / Al2O3 composite carrier into distilled water and disperse them evenly; S22: The product obtained in step S21 is centrifuged and dried for 12 hours; S23: calcining the product obtained in step S22 at 350-400° C. for 2 h to obtain the Nb2O5-modified TiO2 / Al2O3 composite carrier.

4. The preparation method according to claim 1, characterized in that: Step S3 specifically includes the following sub-steps: S31: Dissolve Co(NO3)2·6H2O and Fe(NO3)3·9H2O in water, then add the TiO2 / Al2O3 composite carrier modified in step S2, disperse evenly and immerse for 12 hours; S32: The product obtained in step S31 is centrifuged and dried for 12 hours; S33: heating the product obtained in step S32 to 300-400° C. under a nitrogen atmosphere and calcining for 3 hours; S34: maintaining the temperature, reducing the product obtained in step S33 under a hydrogen atmosphere for 3 hours; S35: The product obtained in step S34 is transferred to a nitrogen atmosphere and cooled to room temperature to obtain the supported Co-Fe bimetallic catalyst.

5. The preparation method according to claim 3, characterized in that: In step S21, the dispersion method is stirring dispersion, and the stirring time is 12 hours; The drying temperature in step S22 is 120°C.

6. The preparation method according to claim 4, characterized in that: In step S31, the dispersion method is ultrasonic dispersion, and the dispersion time is 10 minutes; The drying temperature in step S32 is 100°C.

7. The preparation method according to claim 4, characterized in that: Step S33 specifically includes the following sub-steps: S331: placing the product obtained in step S32 in a tube furnace, and heating the temperature to 300-400° C. at a heating rate of 5° C. / min under a nitrogen atmosphere; S332: Maintain the temperature and roast for 3 hours.

8. An application of a supported Co-Fe bimetallic catalyst, characterized in that: The supported Co-Fe bimetallic catalyst prepared by the preparation method according to any one of claims 1 to 7 is used for preparing 2-methoxy-4-methylphenol by hydrodeoxygenation of vanillin.

9. The use according to claim 8, characterized in that: The preparation of 2-methoxy-4-methylphenol by hydrodeoxygenation of vanillin specifically comprises the following steps: S10: adding 1,4-dioxane, vanillin and the supported Co-Fe bimetallic catalyst into a high-pressure reactor, sealing the reactor and replacing the air in the reactor with hydrogen for 4 to 5 times; S20: After the autoclave is evacuated, the temperature is raised to 80-100°C, the pressure in the autoclave is adjusted to 1.0-1.2 MPa, and the reaction is stirred for 6 hours; S30: After the reaction is completed, the high-pressure reactor is placed in a cold water bath and cooled to room temperature, the reaction liquid in the reactor is taken out, and the 2-methoxy-4-methylphenol is obtained after filtering.

10. The use according to claim 9, characterized in that: The stirring method in step S20 is magnetic stirring.