Nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow and preparation method
By introducing nitrogen species on the carbon substrate material and supporting palladium metal to form a Pd/NC catalyst, the problems of low stability, activity and selectivity of the existing catalytic system are solved, and efficient catalytic vanillin hydrodeoxygenation reaction under mild conditions are achieved.
Patent Information
- Application Number
- CN202510218704.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-05-06
AI Technical Summary
The existing vanillin hydrodeoxygenation catalytic system has problems of low stability, activity and selectivity, and the reaction conditions are harsh, requiring high temperature, high pressure and high hydrogen pressure.
Using a nitrogen-doped carbon catalyst based on hydrogen overflow, a nitrogen species is introduced by adding urea to the carbon substrate material for reflux treatment, and palladium metal is supported on the carbon support, and the palladium metal is reduced by calcination treatment to form a Pd/NC catalyst.
The activity and selectivity of the catalyst are significantly improved, the activity is increased by 18.2 times, and the stability of the catalyst is greatly improved, which can efficiently catalyze the hydrodeoxygenation reaction of vanillin under mild reaction conditions.
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Figure CN119926469A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of thermal catalysis technology, and in particular to a nitrogen-doped carbon catalytic hydrogenation deoxygenation material based on hydrogen overflow and a preparation method thereof. Background Art
[0002] Biomass resources are green and fully renewable resources. Using renewable biomass to replace traditional fossil resources has been considered a potential solution for the sustainable production of liquid fuels and high-value-added chemicals. However, biomass derivatives (such as bio-oil) have disadvantages such as high oxygen content, unstable combustion, and low calorific value. They cannot be used directly and often require some special processing to be effectively upgraded, including hydrodeoxygenation, zeolite cracking, and aqueous phase reforming. Hydrodeoxygenation reaction can significantly reduce the oxygen content of bio-oil and is an important means of upgrading biofuels. Vanillin is an important oxygen-containing compound produced by the pyrolysis of biomass lignin. The main products of vanillin hydrodeoxygenation reaction are vanillyl alcohol and 4-methylguaiacol. 4-methylguaiacol is widely used as an intermediate for drugs or spices, and is a very promising liquid biofuel. Although many important advances have been made in the design of catalytic systems for the hydrodeoxygenation of vanillin to 4-methylguaiacol, the existing catalytic systems still have many shortcomings that need to be overcome, such as: harsh reaction conditions (high temperature and pressure, high hydrogen pressure), poor stability, low energy efficiency, the use of added acid and alkali, etc. In recent years, green chemistry has become an inevitable development trend in the field of chemistry and chemical engineering. Therefore, it is of great significance to develop green, mild reaction conditions, high efficiency, and simple system catalysts for the selective hydrodeoxygenation of vanillin to prepare 4-methylguaiacol.
[0003] In the study of heterogeneous catalytic reactions, the phenomenon of hydrogen overflow is widely present. The transfer behavior of hydrogen active species between different catalytic components realizes the hydrogenation process of reactants at non-dissociated hydrogen active sites, affecting the activity, selectivity and stability of the catalyst catalytic reaction. Usually, hydrogen overflow occurs when the following points are met: (1) there is a metal that can adsorb and dissociate hydrogen, turning it into hydrogen ions or active hydrogen radicals; (2) there is a channel and driving force to realize the transfer of active hydrogen species, or an active hydrogen receiver. In general, the active dissociation of hydrogen in heterogeneous catalysis is achieved by metals containing d-band vacancies, such as rhodium, platinum, rhenium, ruthenium, palladium, etc., which have a moderate interaction force with hydrogen ions and decompose hydrogen ions into active hydrogen species.
[0004] How to improve the activity, stability and selectivity of the catalytic reaction by utilizing the hydrogen overflow phenomenon is one of the solutions to the problems of low stability, activity and selectivity of existing vanillin hydrodeoxygenation catalysts. Summary of the invention
[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow and a preparation method to solve the problems of low stability, activity and selectivity of existing catalysts.
[0006] The technical solution of the present invention to solve the above technical problems is as follows:
[0007] A method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow comprises the following steps:
[0008] (1) adding urea to a carbon substrate material, subjecting the carbon substrate material to a reflux treatment and then drying the reflux treatment to obtain a nitrogen-doped carbon support;
[0009] (2) adding a volatile solvent to the nitrogen-doped carbon support obtained in step (1) to disperse the mixture evenly, then adding a palladium metal salt aqueous solution, stirring and evaporating the solvent, and finally calcining the mixture to obtain the product.
[0010] The beneficial effects of the present invention are as follows: the carbon-based material has the advantages of large specific surface area, high mechanical strength, easy reduction of the metal phase, etc., and also has good acid and alkali resistance, a stable structure under high temperature conditions, and is easy to prepare; the introduction of nitrogen species on the surface of the carbon carrier increases the surface polarity of the catalyst, improves the ability of hydrogen overflow, and can also enhance the adsorption capacity of the reactants, thereby further improving the hydrogenation of the overflowed hydrogen of the reactants on the carbon surface; compared with the traditional Pd / C catalyst, the activity of the Pd / NC catalyst is increased by 18.2 times. In addition, the catalyst prepared by the method of the present invention also greatly improves the stability, providing an effective method for the efficient preparation of hydrogenation catalysts.
[0011] Furthermore, in step (1), the carbon base material includes any one of carbon black, activated carbon and carbon fiber.
[0012] Furthermore, in step (1), the mass ratio of the carbon base material to urea is 1:3-5.
[0013] Furthermore, in step (1), the temperature of the reflux treatment is 75-85°C for 8-12 hours; and the drying temperature is 60-80°C.
[0014] The beneficial effect of adopting the above-mentioned further technical scheme is as follows: the present invention successfully introduces nitrogen species into the surface of the carbon material by refluxing the carbon base material and urea. If the reflux treatment time is too long or too short, too few nitrogen species will be introduced into the surface of the carbon material, thus affecting the catalytic effect.
[0015] Furthermore, the volatile solvent in step (2) includes any one of water, methanol, ethanol, propanol, isopropanol, ether and dichloromethane.
[0016] Furthermore, in step (2), the mass ratio of the nitrogen-doped carbon support to palladium nitrate is 100:3-9.
[0017] Furthermore, the stirring time in step (2) is 30-90 min; the calcination conditions are: in a mixture of hydrogen and rare gas, the temperature is increased to 300-400° C. at a heating rate of 4-6° C. / min and calcined for 1-3 h.
[0018] The beneficial effect of adopting the above-mentioned further technical scheme is as follows: the present invention can reduce the metal palladium ions loaded on the carbon carrier into a single palladium substance by calcining the material at 300-400°C. The heating rate and calcination conditions set by the present invention can effectively improve the uniformity of the reduction reaction and improve the catalytic effect.
[0019] A nitrogen-doped carbon catalytic hydrogenation and deoxygenation material based on hydrogen overflow is prepared by adopting the above preparation method.
[0020] The above-mentioned nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow is used as a catalyst.
[0021] Furthermore, it is used to catalyze the hydrodeoxygenation reaction of vanillin.
[0022] Furthermore, the method for catalyzing the hydrodeoxygenation reaction of vanillin using the nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow as a catalyst comprises the following steps:
[0023] (a) uniformly dispersing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow in an organic solvent, and then adding vanillin thereto;
[0024] (b) introducing hydrogen gas into a high pressure environment and reacting at 20-40° C. under stirring conditions.
[0025] The present invention has the following beneficial effects:
[0026] (1) In the present invention, urea is used to treat the carbon material to introduce a large amount of nitrogen species onto its surface. This step is simple to operate, has mild conditions, and the raw materials are cheap and readily available. The precious metal palladium is loaded onto the surface of the pretreated carbon material by an impregnation method, which has the advantages of simple operation. In addition, the carbon material loaded with the precious metal has many active sites, high catalytic efficiency, and a catalytic conversion rate of more than 99%.
[0027] (2) The catalyst in the present application uses hydrogen as the source of hydrogen ions in catalyzing the hydrogenation and deoxygenation of vanillin, which is in line with the concept of green chemistry development. Compared with the catalyst used for vanillin hydrogenation in the prior art, the catalyst has better activity, making the vanillin conversion rate and the selectivity of 4-methylguaiacol higher than 99%, which can greatly improve the yield and reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 TEM images of carbon black and the NC carrier prepared in Example 1, wherein a is carbon black and b is the NC carrier;
[0029] Figure 2 The metal particle size distribution and high-resolution transmission electron microscopy images of the catalysts obtained in Example 1 and Comparative Example 1 are, among which, a and b are metal particle size distribution images of Pd / C obtained in Comparative Example 1, c is a high-resolution transmission electron microscopy image of Pd / C obtained in Comparative Example 1, d and e are metal particle size distribution images of Pd / NC obtained in Example 1, and f is a high-resolution transmission electron microscopy image of Pd / NC obtained in Example 1;
[0030] Figure 3 The experimental results of the hydrodeoxygenation of vanillin by the catalysts prepared in Example 1 and Comparative Example 1 are shown, wherein a is a diagram showing the effect of hydrodeoxygenation, and b is the TOF values of the two catalysts;
[0031] Figure 4 The cyclic stability test results of the Pd / CN catalyst prepared in Example 1 are shown. DETAILED DESCRIPTION
[0032] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.
[0033] Embodiment 1:
[0034] A method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow comprises the following steps:
[0035] (1) Preparation of NC carrier
[0036] Take 1g of carbon black and 4g of urea and add them into a round-bottom flask. Add 40mL of deionized water and condense and reflux at 80°C for 10h. Place the condensed reflux product in a forced air drying oven and dry it at 70°C to obtain the NC carrier.
[0037] (2) Preparation of Pd / NC supported catalyst
[0038] At room temperature, 300 mg of the NC carrier powder obtained in step (1) was uniformly dispersed in 30 mL of ethanol by ultrasound and stirring, and 1800 μL of a 5 mg / mL aqueous palladium nitrate solution was dropwise added to the suspension. After stirring for 1 hour, the ethanol was completely evaporated to obtain a black solid powder. Finally, the temperature was raised to 350° C. at a rate of 5° C. / min in a H2 / Ar mixed gas (the volume fraction of H2 was 5%), and calcined for 2 hours to obtain a Pd / NC supported catalyst with a Pd loading of 3 wt%.
[0039] Embodiment 2:
[0040] A method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow comprises the following steps:
[0041] (1) Preparation of NC carrier
[0042] Take 1g of carbon black and 4g of urea and add them into a round-bottom flask. Add 40mL of deionized water and condense and reflux at 85°C for 12h. Place the condensed reflux product in a forced air drying oven and dry it at 80°C to obtain the NC carrier.
[0043] (2) Preparation of Pd / NC supported catalyst
[0044] At room temperature, 300 mg of the NC carrier powder obtained in step (1) was uniformly dispersed in 30 mL of ethanol by ultrasound and stirring, and 5400 μL of a 5 mg / mL aqueous palladium nitrate solution was dropwise added to the suspension. After stirring for 1 hour, the ethanol was completely evaporated to obtain a black solid powder. Finally, the temperature was raised to 300° C. at a rate of 6° C. / min in a H2 / Ar mixed gas (the volume fraction of H2 was 5%) and calcined for 2 hours to obtain a Pd / NC supported catalyst with a Pd loading of 9 wt%.
[0045] Embodiment 3:
[0046] A method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow comprises the following steps:
[0047] (1) Preparation of NC carrier
[0048] Take 1g of carbon black and 4g of urea and add them into a round-bottom flask. Add 40mL of deionized water and condense and reflux at 75°C for 8h. Place the condensed reflux product in a forced air drying oven and dry it at 60°C to obtain the NC carrier.
[0049] (2) Preparation of Pd / NC supported catalyst
[0050] At room temperature, 300 mg of the NC carrier powder obtained in step (1) was uniformly dispersed in 30 mL of ethanol by ultrasound and stirring, 3600 μL of a 5 mg / mL aqueous palladium nitrate solution was dropwise added to the suspension, and the mixture was stirred for 1 hour and then heated to completely evaporate the ethanol to obtain a black solid powder. Finally, the mixture was heated to 300° C. at a rate of 5° C. / min in a H2 / Ar mixed gas (the volume fraction of H2 was 5%) and calcined for 3 hours to obtain a Pd / NC supported catalyst with a Pd loading of 6 wt%.
[0051] Comparative Example 1:
[0052] A method for preparing a Pd / C supported catalyst, characterized in that it comprises the following steps:
[0053] At room temperature, 300 mg of carbon black was uniformly dispersed in 30 mL of ethanol by ultrasound and stirring, and 1800 μL of 5 mg / mL palladium nitrate aqueous solution was dropwise added to the suspension. After stirring for 1 hour, the ethanol was completely evaporated by heating to obtain a black solid. Finally, the temperature was raised to 350°C at a rate of 5°C / min in a H2 / Ar mixed gas (the volume fraction of H2 was 5%) and calcined for 2 hours to obtain a Pd / C supported catalyst with a Pd loading of 3 wt%.
[0054] Test example:
[0055] 1. The carbon black raw material, the NC carrier prepared in Example 1, and the catalysts prepared in Example 1 and Comparative Example 1 were characterized by transmission electron microscopy. The characterization results are as follows: Figure 1 and Figure 2 shown.
[0056] Figure 1 TEM images of carbon black raw materials and NC carriers. The results show that nitrogen species appeared on the surface of the NC carrier after urea treatment, indicating the successful introduction of nitrogen species into the NC carrier, enhancing its apparent polarity.
[0057] Figure 2 is the particle size of Pd in the two catalysts prepared in Example 1 and Comparative Example 1, such as Figure 2 As shown in Figures a and d, in the dark field TEM images, the average particle size of Pd / C was measured to be 3.04±0.1nm ( Figure 2 The average particle size of Pd / NC is 2.65±0.04nm ( Figure 2 Meanwhile, the measured lattice fringe spacing is 0.228 nm, corresponding to the (111) crystal plane of the Pd nanoparticles in the high-resolution TEM image ( Figure 2 c and f in the figure), which shows that the metal Pd nanoparticles were successfully loaded on Pd / C and Pd / NC.
[0058] 2. The catalysts prepared in Example 1 and Comparative Example 1 were respectively used to catalyze the hydrodeoxygenation of vanillin to prepare 4-methylguaiacol. The specific method was carried out by the following steps:
[0059] (1) 5 mg of the catalyst material was uniformly dispersed in 2 mL of isopropanol, and then 1 mmol of the reactant vanillin was added;
[0060] (2) The mixture obtained in step (1) was transferred to a 500 mL autoclave, and the mixture was purged with 1 MPa H2 for three times and then reacted in a 1 MPa H2 atmosphere with magnetic stirring and the temperature controlled at 30°C;
[0061] (3) The liquid phase composition was quantitatively analyzed by liquid chromatography and the vanillin conversion rate and 4-methylguaiacol selectivity were recorded.
[0062] The experimental results are as follows Figure 3 As shown. Figure 3 As can be seen in Figure a, the conversion rate of vanillin over the Pd / NC catalyst was 99.38% after 1.5 h of reaction. The TOF value of each exposed Pd atom was 5447 h -1 ( Figure 3 (Figure c). Under the same reaction conditions, the conversion rate of Pd / C catalyst in 1.5h was only 10.29%. The TOF value of Pd / C was 300h -1 , which is 18.2 times lower than that of Pd / NC. Therefore, the urea-treated carbon can greatly improve the catalytic hydrodeoxygenation activity of Pd nanoparticles.
[0063] In addition to significantly improving the activity, the Pd / NC catalyst also improves the selectivity of 4-methylguaiacol. As shown in Figures a and b, at the end of the reaction, the conversion rate of vanillin is 100% and the selectivity of 4-methylguaiacol is 100%. Under the same reaction conditions, the conversion rate of vanillin by the Pd / C catalyst is 95.71%, and the selectivity is only 1.8%. Therefore, the Pd / NC catalyst can simultaneously improve the catalytic activity and selectivity of vanillin hydrodeoxygenation to 4-methylguaiacol.
[0064] 3. Catalyst Cycle Stability Test
[0065] The stability of the catalyst is also an important factor in evaluating the performance of the catalyst. Weigh 20 mg of the Pd / NC catalyst prepared in Example 1, add it to 2 mmol of vanillin, the hydrogen pressure is 1 MPa, the solvent is 4 mL of isopropanol, and the reaction is carried out at 30°C. The Pd / NC catalyst has a reaction cycle of 2 hours. The catalyst can be separated by centrifugation and recycled without treatment. Six cycles are tested.
[0066] The experimental results are as follows Figure 4As shown, the conversion rates of vanillin in the 1st, 2nd, 3rd, 4th, 5th and 6th cycles of the Pd / NC catalyst were 99.92%, 99.6%, 99.85%, 99.68%, 99.21% and 99.54%, respectively, and the selectivity of 4-methylguaiacol was 97.55%, 95.2%, 96.85%, 94.92%, 93.66% and 92.25%, respectively. The results show that the catalyst prepared in Example 1 of the present invention has good catalytic stability. Therefore, the Pd / NC catalyst exhibits high catalytic activity and selectivity as well as good stability while catalyzing the hydrodeoxygenation reaction of vanillin.
[0067] The above experimental results show that the catalyst Pd / NC has high recycling ability in the hydrodeoxygenation of vanillin to prepare 4-methylguaiacol.
[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow, characterized in that: The following steps are involved: (1) adding urea to a carbon substrate material, subjecting the carbon substrate material to a reflux treatment and then drying the reflux treatment to obtain a nitrogen-doped carbon support; (2) adding a volatile solvent to the nitrogen-doped carbon support obtained in step (1) to disperse the mixture evenly, then adding a palladium metal salt aqueous solution, stirring and evaporating the solvent, and finally calcining the mixture to obtain the product.
2. The method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow according to claim 1, characterized in that: The carbon base material in step (1) includes any one of carbon black, activated carbon and carbon fiber.
3. The method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow according to claim 1, characterized in that: In the step (1), the mass ratio of the carbon base material to urea is 1:3-5.
4. The method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow according to claim 1, characterized in that: In the step (1), the temperature of the reflux treatment is 75-85°C for 8-12 hours; and the temperature of the drying is 60-80°C.
5. The method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow according to claim 1, characterized in that: The volatile solvent in step (2) includes any one of water, methanol, ethanol, propanol, isopropanol, ether and dichloromethane.
6. The method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow according to claim 1, characterized in that: In the step (2), the mass ratio of the nitrogen-doped carbon carrier to palladium nitrate is 100:3-9.
7. The method for preparing a nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow according to claim 1, characterized in that: The stirring time in step (2) is 30-90 minutes; the calcination conditions are: in a mixture of hydrogen and rare gas, the temperature is increased to 300-400° C. at a heating rate of 4-6° C. / min and calcined for 1-3 hours.
8. A nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 7.
9. Use of the nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow as claimed in claim 8 as a catalyst.
10. The use of the nitrogen-doped carbon catalytic hydrodeoxygenation material based on hydrogen overflow as claimed in claim 8, characterized in that: Used to catalyze the hydrodeoxygenation reaction of vanillin.