Process and catalyst for preparing aromatic hydrocarbon by hydrodeoxygenation of lignin
Through the three-step process of unsupported catalyst, the stability and cost problems of bio-oil after lignin depolymerization are solved, and efficient conversion into aromatic hydrocarbons is achieved, with industrial application potential.
Patent Information
- Application Number
- CN202411245713.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2024-12-13
AI Technical Summary
In the prior art, bio-oils have high acidity, high viscosity, low calorific value and chemical instability after lignin depolymerization. The cost of precious metal catalysts is high and limits industrial applications. There is a lack of high selectivity and low cost catalysts for adding Hydrogen deoxygenation process.
The unsupported NixMoy catalyst was used for lignin depolymerization and pre-hydrotherapy, and then the unsupported MomCunNik catalyst was used for hydrodeoxygenation. The lignin was efficiently converted into aromatic products through three-step processes. The catalyst had many active sites. High catalytic activity, low price and easy to prepare on a large scale.
It achieves efficient conversion from lignin to aromatic hydrocarbons, inhibits the polymerization of unsaturated hydrocarbons of bio-oils, reduces excessive hydrogenation, improves the selectivity and yield of aromatic hydrocarbon products, reduces process costs, and has industrial potential.
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Figure CN119119138A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of preparing high-value chemicals by depolymerization of lignin, and specifically relates to a three-step process for preparing aromatics by hydrodeoxygenation of lignin and the preparation of a corresponding non-supported catalyst. Background Art
[0002] Lignin is a cross-linked phenolic polymer with a complex three-dimensional spatial structure. Its rich aromatic characteristics provide a huge potential source for the preparation of various functional chemicals. Depolymerization is an indispensable step in upgrading lignin to small-molecule bio-oil. The depolymerized bio-oil is composed of a variety of small-molecule phenolic compounds, such as phenolic monomers, dimers and oligomers. However, the depolymerized bio-oil has a high oxygen content, which makes the bio-oil have problems such as high acidity, high viscosity, low calorific value and chemical instability. Therefore, the lignin macromolecules are usually first depolymerized by breaking bonds to obtain lignin small-molecule compounds, and then catalytic hydrogenation and deoxygenation reactions are carried out to eliminate oxygen in the bio-oil to produce chemicals or fuels with high added value.
[0003] Lignin depolymerization is the result of multiple reactions occurring simultaneously, including the breaking of unit bonds, defunctionalization (decarboxylation, demethylation), hydrodeoxygenation and cross-linking reactions. The specific mechanism depends on the choice of process conditions, such as acid-catalyzed depolymerization, base-catalyzed depolymerization, solvent depolymerization, oxidative depolymerization, rapid pyrolysis and reductive depolymerization.
[0004] There are many types of catalysts used for hydrodeoxygenation of bio-oil from lignin depolymerization. Although most single metal noble metal catalysts mainly produce cyclic saturated hydrocarbon products, some reports show that catalysts such as Pd, Pt, and Ru can achieve high aromatic selectivity under specific conditions. For non-noble metal catalysts, transition metals such as Mo, Fe, Co, Ni, and Cu have been widely used in the hydrodeoxygenation of lignin and its model compounds, and demethylation, demethoxylation, and deoxygenation reactions can occur simultaneously on these catalysts. In addition, studies have shown that sulfide catalysts, carbide catalysts, and phosphide catalysts also have high selectivity in the hydrodeoxygenation reaction of lignin or its model compounds.
[0005] At present, the depolymerization of lignin to produce high-value chemicals has been studied a lot. Chinese patent CN 106753549A discloses a method for producing hydrocarbon fuels by using light phenol products of lignin depolymerization as raw materials, pre-hydrogenating with Raney Ni as catalyst in ethanol solvent, and then completing the hydrodeoxygenation reaction under Pb / Nb2O5-SiO2 or Pt / Nb2O5-SiO2 catalyst. The pre-hydrogenation method can effectively remove the unsaturated double bonds in the lignin cracking products to prevent their high-temperature polymerization. Although this method effectively obtains hydrocarbon fuel components, the precious metal catalyst used in this method may limit its industrial application. Chinese patent CN 108774542 A discloses a method for producing hydrocarbon products by using monocyclic phenol compounds of lignin depolymerization products as raw materials under the action of nano iron powder. This method shows excellent catalytic activity of the catalyst and high hydrodeoxygenation efficiency. This shows that there is great potential in preparing high-value chemicals from lignin depolymerization. Therefore, it is of great significance to develop a green, pollution-free, and highly selective catalyst for the production of aromatic compounds in the lignin depolymerization and hydrodeoxygenation process. Summary of the invention
[0006] The object of the present invention is to provide a method for catalytically depolymerizing lignin and preparing aromatics by hydrodeoxygenation treatment, wherein the method uses real lignin as a reaction raw material, and is carried out through a three-step process of depolymerization, pre-hydrogenation treatment and hydrodeoxygenation, and lignin is efficiently converted into aromatic products. The catalyst used in the method is a non-supported catalyst, which has the characteristics of many active sites and high catalytic activity. In addition, the catalyst is low in price, easy to prepare on a large scale, and the process conditions have the advantages of low energy consumption and low cost, and have the potential for industrialization.
[0007] The present invention is achieved by adopting the following technical solutions:
[0008] (1) Non-loaded Ni x Mo y Catalyst, mixed alcohol solvent and lignin are added to the reactor. After the reactor is sealed, H2 is used to purge the air. Then the reactor is heated to the set pressure, the speed is adjusted to the set speed, and the temperature is raised to the set temperature at a certain heating rate. Under the conditions of total pressure of the reaction system of 2-4 MPa, temperature of 200-300°C, and speed of 400-800 rpm, the crude bio-oil is obtained after the reaction for 4-10 hours. x Mo y The catalyst accounts for 1 to 20% of the total mass of lignin, and the mass ratio of methanol to ethanol is 10:1 to 1:10. x Mo yThe catalyst is prepared by a chemical precipitation method, and the specific preparation method is as follows: nickel acetate (or basic nickel carbonate) and molybdenum trioxide (or ammonium molybdate) are dissolved in water in a molar ratio of 1:3 to 3:1, the nickel acetate (or basic nickel carbonate) solution is stirred and heated at 60 to 90° C., then the molybdenum trioxide (or ammonium molybdate) solution is added, stirred for 10 to 30 minutes, and then ammonia water is added dropwise, the pH value is adjusted to 8 to 10, heated and stirred for 6 to 12 hours, and filtered after standing to room temperature. After the filtration is completed, the catalyst is transferred to an oven at 90 to 120° C. for drying for 8 to 12 hours, and then the dried catalyst precursor is transferred to a muffle furnace at 350 to 550° C. for roasting for 4 to 6 hours, and finally 20 to 40 mesh catalyst particles are obtained by tableting.
[0009] (2) The crude lignin bio-oil obtained in (1) is pre-hydrogenated to obtain a stable bio-oil. This process is carried out in a continuous fixed bed reactor. Before the reaction begins, the catalyst is activated in a fixed bed reactor at 300-400°C in a hydrogen atmosphere for 6-10 hours. The temperature in the reaction system is 100-220°C, and the space velocity is 0.5h -1 ~3h -1 , hydrogen-to-oil ratio 200-600, hydrogen pressure 1-4Mpa. The process uses the same Ni x Mo y catalyst.
[0010] (3) Transfer the stabilized bio-oil after pre-hydrogenation in step (2) to a non-supported Mo m Cu n Ni k The catalyst is activated in a fixed bed reactor at 300-400℃ hydrogen atmosphere for 6-10h before the reaction. The temperature in the reaction system is 200-360℃, and the space velocity is 0.5h -1 ~3h -1 , hydrogen-oil ratio 200-600, hydrogen pressure 1-4Mpa. m Cu n Ni kThe catalyst is prepared by a chemical precipitation method, and the specific preparation method is as follows: molybdenum trioxide (or ammonium molybdate), copper acetate and nickel acetate (or basic nickel carbonate) are dissolved in water according to a molar ratio of 10:1:0.05 to 10:10:3, and then the molybdenum trioxide (or ammonium molybdate) solution, the copper acetate solution and the nickel acetate (or basic nickel carbonate) solution are mixed, heated and stirred at 60 to 90°C for 10 to 30 minutes, and then ammonia water is added dropwise, the pH value is adjusted to 8 to 10, heated and stirred for 6 to 12 hours, and filtered after standing to room temperature. After the filtration is completed, the catalyst precursor is transferred to an oven at 90 to 120°C for drying for 8 to 12 hours, and then the dried catalyst precursor is transferred to a muffle furnace at 350 to 550°C for roasting for 4 to 6 hours, and finally 20 to 40 mesh catalyst particles are obtained by tableting.
[0011] Compared with the prior art, the present invention has the following outstanding effects:
[0012] The three-step process of depolymerization, pre-hydrogenation, and hydrodeoxygenation effectively realizes the conversion of lignin to aromatic products. The second step of pre-hydrogenation uses non-supported Ni x Mo y The low-temperature, high-activity catalyst inhibits the polymerization of unsaturated hydrocarbons in bio-oil and avoids the occurrence of coking. The third step of hydrodeoxygenation uses non-supported Mo m Cu n Ni k The catalyst has high selectivity, is conducive to deoxygenation, and can reduce the occurrence of over-hydrogenation, generating as many aromatic products as possible. x Mo y Catalyst and Mo m Cu n Ni k The catalyst has the characteristics of multiple active sites and high catalytic activity, and the catalyst is low in price and simple in preparation method, which is conducive to industrial application. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 Figures a, b, and c are respectively chromatograms of crude bio-oil generated by cracking lignin under the action of Ni1Mo1 catalyst in Example 2 of the present invention, chromatograms of stable bio-oil after pre-hydrogenation of crude lignin bio-oil under Ni1Mo1 catalyst, and chromatograms of stable bio-oil after pre-hydrogenation under Mo1Cu 0.8 Ni 0.2 Chromatogram of the product after hydrodeoxygenation under the catalyst. It can be seen from the figure that after pre-hydrogenation and hydrodeoxygenation, the lignin crude bio-oil is converted from larger molecules such as phenols and aromatic ester compounds to small aromatic molecules. DETAILED DESCRIPTION
[0014] The following comparative examples and embodiments are further descriptions of the present invention. The following comparative examples and embodiments are only used to explain the present invention, rather than to limit the present invention.
[0015] Comparative Example 1
[0016] The first step is lignin depolymerization. Lignin catalytic cracking is carried out in a reactor. 100g of mixed alcohol solution (methanol: ethanol = 1:1) is ultrasonically mixed with 10g of lignin for 20 minutes and then added to the reactor, and 1g of Ni1Mo1 catalyst is added. After the reactor is sealed, H2 is used to purge the air in the reactor. The hydrogen pressure in the reaction system is 3Mpa, the speed is 600rmp, the reaction time is 4h, and the temperature is 260°C. After the reaction is completed, the reactor is cooled to room temperature. The reactor is opened, the product after the reaction is taken out, the solvent is evaporated, and the crude bio-oil is obtained. Then the weight of the bio-oil is weighed, and the crude bio-oil yield is calculated to be 81.3% according to the bio-oil yield (%) = crude bio-oil mass / lignin mass × 100%.
[0017] The second step is pre-hydrogenation of lignin bio-oil. The lignin cracking bio-oil is pre-hydrogenated in a continuous fixed-bed reactor to obtain stable bio-oil. The fixed-bed reactor is loaded with 10mL Ni1Mo1 catalyst and activated under hydrogen atmosphere at 350℃ for 8h. Then, the reaction system is heated at 200℃ and the space velocity is 2h. -1 The lignin pyrolysis bio-oil was pre-hydrogenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 3Mpa.
[0018] The third step is to hydrodeoxygenate the pretreated bio-oil. The pretreated bio-oil is hydrodeoxygenated in a continuous fixed-bed reactor to obtain aromatic products. The fixed-bed reactor is loaded with 10 mL of Mo1Cu1 catalyst and activated for 8 h in a hydrogen atmosphere at 350 ° C. Then, the reaction system is heated at 320 ° C and the space velocity is 2 h. -1 The pretreated bio-oil was hydrodeoxygenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 1 MPa. The aromatics yield reached 54.3%.
[0019] Comparative Example 2
[0020] The first step is lignin depolymerization. Lignin catalytic cracking is carried out in a reactor. 100g of mixed alcohol solution (methanol: ethanol = 1:1) is ultrasonically mixed with 10g of lignin for 20 minutes and then added to the reactor. 1g of Ni1Mo1 catalyst is added. After the reactor is sealed, H2 is purged to remove the air in the reactor. The hydrogen pressure in the reaction system is 3Mpa, the speed is 600rmp, the reaction time is 4h, and the temperature is 260°C. After the reaction is completed, the reactor is cooled to room temperature. The reactor is opened, the product after the reaction is taken out, and the solvent is evaporated to obtain crude bio-oil. The crude bio-oil yield is calculated to be 81.3%.
[0021] The second step is pre-hydrogenation of lignin bio-oil. The lignin cracking bio-oil is pre-hydrogenated in a continuous fixed-bed reactor to obtain stable bio-oil. The fixed-bed reactor is loaded with 10mL Ni1Mo1 catalyst and activated under hydrogen atmosphere at 350℃ for 8h. Then, the reaction system is heated at 200℃ and the space velocity is 2h. -1 The lignin pyrolysis bio-oil was pre-hydrogenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 3Mpa.
[0022] The third step is to hydrodeoxygenate the pretreated bio-oil. The pretreated bio-oil is hydrodeoxygenated in a continuous fixed-bed reactor to obtain aromatic products. The fixed-bed reactor is loaded with 10 mL of Ni1Mo1 catalyst and activated for 8 h in a hydrogen atmosphere at 350 ° C. Then, the reaction system is heated at 320 ° C and the space velocity is 2 h. -1 The pretreated bio-oil was hydrodeoxygenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 1 MPa. The aromatics yield reached 40.6%.
[0023] Example 1
[0024] The first step is lignin depolymerization. Lignin catalytic cracking is carried out in a reactor. 100g of mixed alcohol solution (methanol: ethanol = 1:1) is ultrasonically mixed with 10g of lignin for 20 minutes and then added to the reactor. 1g of Ni1Mo1 catalyst is added. After the reactor is sealed, H2 is purged to remove the air in the reactor. The hydrogen pressure in the reaction system is 3Mpa, the speed is 600rmp, the reaction time is 4h, and the temperature is 260°C. After the reaction is completed, the reactor is cooled to room temperature. The reactor is opened, the product after the reaction is taken out, and the solvent is evaporated to obtain crude bio-oil. The crude bio-oil yield is calculated to be 81.3%.
[0025] The second step is pre-hydrogenation of lignin bio-oil. The lignin cracking bio-oil is pre-hydrogenated in a continuous fixed-bed reactor to obtain stable bio-oil. The fixed-bed reactor is loaded with 10mL Ni1Mo1 catalyst and activated under hydrogen atmosphere at 350℃ for 8h. Then, the reaction system is heated at 200℃ and the space velocity is 2h. -1 The lignin pyrolysis bio-oil was pre-hydrogenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 3Mpa.
[0026] The third step is to hydrodeoxygenate the pretreated bio-oil. The pretreated bio-oil is hydrodeoxygenated in a continuous fixed-bed reactor to obtain aromatic products. The fixed-bed reactor is filled with 10 mL Mo1Cu 0.9 Ni 0.1 The catalyst was activated in a hydrogen atmosphere at 350°C for 8 h. -1 The pretreated bio-oil was hydrodeoxygenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 1 MPa. The aromatics yield reached 78.5%.
[0027] Example 2
[0028] The first step is lignin depolymerization. The catalytic cracking of lignin is carried out in a reactor. 100g of mixed alcohol solution (methanol: ethanol = 1:1) is ultrasonically mixed with 10g of lignin for 20 minutes and then added to the reactor. 1g of Ni1Mo1 catalyst is added. After the reactor is sealed, H2 is used to purge the air in the reactor. The hydrogen pressure in the reaction system is 3Mpa, the speed is 600rmp, the reaction time is 4h, and the temperature is 260°C. After the reaction is completed, the reactor is cooled to room temperature. The reactor is opened, the product after the reaction is taken out, and the solvent is evaporated to obtain crude bio-oil. The crude bio-oil yield is calculated to be 81.3%. The chromatogram of the crude bio-oil is shown in Figure 1 .
[0029] The second step is pre-hydrogenation of lignin bio-oil. The lignin cracking bio-oil is pre-hydrogenated in a continuous fixed-bed reactor to obtain stable bio-oil. 10 ml of Ni1Mo1 catalyst is loaded in the fixed-bed reactor and activated for 8 hours under hydrogen atmosphere at 350°C. Then, the reaction system is heated at 200°C and the space velocity is 2h. -1 The lignin pyrolysis bio-oil was pre-hydrogenated under the conditions of 300 hydrogen-oil ratio and 3Mpa hydrogen pressure. The chromatogram of the stable bio-oil is shown in Figure 1 .
[0030] The third step is to hydrodeoxygenate the pretreated bio-oil. The pretreated bio-oil is hydrodeoxygenated in a continuous fixed-bed reactor to obtain aromatic products. The fixed-bed reactor is filled with 10 mL Mo1Cu 0.8 Ni 0.2 The catalyst was activated in a hydrogen atmosphere at 350°C for 8 h. -1 The pretreated bio-oil was hydrodeoxygenated under the conditions of 300 hydrogen-oil ratio and 1 MPa hydrogen pressure. The aromatics yield reached 83.7%. The chromatogram of the bio-oil hydrodeoxygenation product is shown in Figure 1 .
[0031] Example 3
[0032] The first step is lignin depolymerization. Lignin catalytic cracking is carried out in a reactor. 100g of mixed alcohol solution (methanol: ethanol = 1:1) is ultrasonically mixed with 10g of lignin for 20 minutes and then added to the reactor. 1g of Ni1Mo1 catalyst is added. After the reactor is sealed, H2 is purged to remove the air in the reactor. The hydrogen pressure in the reaction system is 3Mpa, the speed is 600rmp, the reaction time is 4h, and the temperature is 260°C. After the reaction is completed, the reactor is cooled to room temperature. The reactor is opened, the product after the reaction is taken out, and the solvent is evaporated to obtain crude bio-oil. The crude bio-oil yield is calculated to be 81.3%.
[0033] The second step is pre-hydrogenation of lignin bio-oil. The lignin cracking bio-oil is pre-hydrogenated in a continuous fixed-bed reactor to obtain stable bio-oil. The fixed-bed reactor is loaded with 10mL Ni1Mo1 catalyst and activated under hydrogen atmosphere at 350℃ for 8h. Then, the reaction system is heated at 200℃ and the space velocity is 2h. -1 The lignin pyrolysis bio-oil was pre-hydrogenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 3Mpa.
[0034] The third step is to hydrodeoxygenate the pretreated bio-oil. The pretreated bio-oil is hydrodeoxygenated in a continuous fixed-bed reactor to obtain aromatic products. The fixed-bed reactor is filled with 10 mL Mo1Cu 0.7 Ni 0.3 The catalyst was activated in a hydrogen atmosphere at 350°C for 8 h. -1 The pretreated bio-oil was hydrodeoxygenated under the conditions of hydrogen-to-oil ratio of 300 and hydrogen pressure of 1 MPa. The aromatics yield reached 82.1%.
[0035] In the description of the hydrodeoxygenation process of the stabilized bio-oil after pre-hydrogenation, the effects of bio-oil hydrodeoxygenation under different catalysts are shown in Table 1.
[0036] Table 1 Comparison of hydrogenation effects of the catalyst of the present invention and the comparative catalyst
[0037]
[0038] Table 1 lists the hydrodeoxygenation effects of the pretreated lignin bio-oil under the catalyst and the comparative catalyst. From the data in the above table, it can be found that when the method of the present invention is used to crack and hydrodeoxygenate lignin to prepare aromatics, the change of the catalyst will affect the hydrodeoxygenation effect of the bio-oil. From the results of Comparative Examples 1 and 2, it can be found that the product after hydrodeoxygenation using the Mo1Cu1 catalyst still has a high content of phenols, and the product after hydrodeoxygenation using the Ni1Mo1 catalyst has a high content of cycloalkanes. In Example Mo m Cu n Ni k The product after catalyst hydrodeoxygenation has a high aromatic content, and a relatively low content of phenols and cycloalkanes, which indicates that the catalyst used in this method has high selectivity for the hydrodeoxygenation process of lignin bio-oil and is conducive to the generation of aromatic products.
[0039] Based on the above embodiments, it can be seen that by x Mo y Lignin depolymerization was carried out under the action of catalysts, and non-supported Ni x Mo y Pre-hydrogenation over the catalyst and unsupported Mo m Cun Ni k The three-step process of hydrodeoxygenation under the action of a catalyst effectively realizes the conversion of lignin into aromatics, and this method can obtain a higher aromatics yield.
[0040] The above is a detailed introduction to the process and catalyst for preparing aromatics by hydrodeoxygenation of lignin provided by the present invention. It should be noted that the embodiments described above are exemplary and not limiting of the present invention. Without departing from the technical concept of the present invention, those skilled in the art may improve and modify the technical solution, and these improvements and modifications should be covered within the scope of protection of the claims of the present invention.
Claims
1. A process and catalyst for preparing aromatics by hydrodeoxygenation of lignin, characterized in that The process consists of the following three steps and corresponding catalysts: (1) Using mixed alcohol as solvent, using non-supported Ni x Mo y The catalyst is used to catalyze the depolymerization of lignin to prepare crude bio-oil. This process is carried out in a hydrogen atmosphere. The mixed alcohol and lignin are mixed and added to the reactor. Then, the reaction is carried out for 4 to 10 hours at a total pressure of 2 to 4 MPa, a temperature of 200 to 300°C, and a rotation speed of 400 to 800 rpm. x Mo y The catalyst accounts for 1 to 20% of the total mass of the lignin. (2) The crude lignin bio-oil obtained in the first step was subjected to hydrogenation pretreatment using a non-supported Ni x Mo y The catalyst is heated in a continuous fixed bed reactor at a reaction temperature of 100 to 220°C and a space velocity of 0.5 to 3 h -1 Hydrogenation pretreatment is carried out under the conditions of hydrogen-oil ratio of 200-600 and hydrogen pressure of 1-4MPa to obtain stable bio-oil. (3) The stable bio-oil obtained in the second step is selectively hydrodeoxygenated to produce aromatics using a non-supported Mo m Cu n Ni k The catalyst is heated in a continuous fixed bed reactor at a temperature of 200 to 360°C and a space velocity of 0.5 to 3 h -1 Aromatics are prepared by selective hydrodeoxygenation of stable bio-oil under the conditions of hydrogen-to-oil ratio of 200-600 and hydrogen pressure of 1-4MPa.
2. The process and catalyst for preparing aromatics by hydrodeoxygenation of lignin according to claim 1, characterized in that The mixed alcohol solvent used is a mixed solvent of methanol and ethanol, and the mass ratio of methanol to ethanol is 10:1 to 1:
10.
3. The process and catalyst for preparing aromatics by hydrodeoxygenation of lignin according to claim 1, characterized in that The unsupported Ni x Mo y The catalyst has x:y=1:3-3:1, that is, the molar ratio of nickel and molybdenum atoms in the catalyst is 1:3-3:
1.
4. The process and catalyst for preparing aromatics by hydrodeoxygenation of lignin according to claim 1, characterized in that The unloaded Mo used m Cu n Ni k The catalyst has m:n:k=10:1:0.05-10:10:3, that is, the molar ratio of molybdenum, copper and nickel atoms in the catalyst is 10:1:0.05-10:10:
3.
5. The process and catalyst for preparing aromatics by hydrodeoxygenation of lignin according to claim 1, characterized in that The non-supported Ni x Mo y and Mo m Cu n Ni k The catalyst needs to be activated in a hydrogen atmosphere at 300-400°C for 6-10 hours before use.