Method for hydrodeoxygenation of lignin by ruthenium-based catalyst under deep eutectic solvent condition
阅读说明：本技术 一种钌基催化剂在深度低共熔溶剂条件下对木质素进行加氢脱氧的方法 (Method for hydrodeoxygenation of lignin by ruthenium-based catalyst under deep eutectic solvent condition ) 是由 常杰 张淑迪 付严 黄晴雯 于 2019-10-12 设计创作，主要内容包括：本发明公开了一种钌基催化剂在深度低共熔溶剂(DES)条件下对木质素进行加氢脱氧的方法。该方法为：将水热残渣和DES加入锥形瓶中,在100-120℃反应3-4h,减压抽滤得到溶解木质素的DES滤液；所述水热残渣：DES为1:20g/g；在氢气氛围下,将溶解木质素的深度低共熔溶剂和50-300mg的催化剂加入高压反应釜中,120-280℃反应2-15h,即得；所述催化剂为Ru/Nb<Sub>2</Sub>O<Sub>5</Sub>、Ru/ZSM-5、Ru/HY、Ru/γ-Al<Sub>2</Sub>O<Sub>3</Sub>或Ru/C。在较低的温度、压力和较短的反应条件下实现了将木质素解聚制备酚类化合物。(The invention discloses a method for hydrodeoxygenation of lignin by a ruthenium-based catalyst under the condition of a Deep Eutectic Solvent (DES). The method comprises the following steps: adding the hydrothermal residue and DES into a conical flask, reacting at 100-120 deg.C for 3-4h, and vacuum filtering to obtain DES filtrate with dissolved lignin; the hydrothermal residue: DES is 1:20 g/g; in thatAdding a deep eutectic solvent for dissolving lignin and 50-300mg of catalyst into a high-pressure reaction kettle in a hydrogen atmosphere, and reacting at the temperature of 120-280 ℃ for 2-15h to obtain the lignin-rich low-temperature eutectic solvent; the catalyst is Ru/Nb 2 O 5 、Ru/ZSM‑5、Ru/HY、Ru/γ‑Al 2 O 3 Or Ru/C. The method realizes the depolymerization of lignin to prepare phenolic compounds under lower temperature, pressure and shorter reaction conditions.)
1. A method for hydrodeoxygenation of lignin by a ruthenium-based catalyst under the condition of a deep eutectic solvent is characterized by comprising the following steps:
(1) preparation of ChCl: acetic acid Deep Eutectic Solvent (DES);
(2) adding the hydrothermal residue and the DES prepared in the step (1) into a conical flask, reacting for 3-4h at the temperature of 100-120 ℃, and performing vacuum filtration to obtain a DES filtrate in which lignin is dissolved; the hydrothermal residue: DES is 1:20 g/g;
(3) adding a deep eutectic solvent for dissolving lignin and 50-300mg of catalyst into a high-pressure reaction kettle in a hydrogen atmosphere, and reacting at the temperature of 120-280 ℃ for 2-15 hours to obtain the lignin-rich low-eutectic solvent; the catalyst is Ru/Nb2O5、Ru/ZSM-5、Ru/HY、Ru/γ-Al2O3Or Ru/C.
2. The method for hydrodeoxygenation of lignin by a ruthenium-based catalyst under the condition of a deep eutectic solvent according to claim 1, wherein in the step (1), the hydrogen bond acceptor is choline chloride (ChCl), the hydrogen bond donor is acetic acid, wherein the molar ratio of the ChCl to the acetic acid is 1:2-1:4, the hydrogen bond acceptor and the hydrogen bond donor are added into a beaker and react for 1-3h at 75-85 ℃, and a clear and transparent solution is obtained, namely the prepared DES.
3. The method for hydrodeoxygenation of lignin by using the ruthenium-based catalyst under the condition of a deep eutectic solvent according to claim 1, wherein in the step (2), the hydrothermal residue is prepared by the following method: reacting eucalyptus powder with water at a solid-to-liquid ratio of 1:10-1:15g/ml at 150-180 ℃ for 0.5-1.5h in a nitrogen atmosphere, filtering under reduced pressure, and drying at 90-110 ℃ to obtain hydrothermal residue.
4. The method for hydrodeoxygenating lignin by using the ruthenium-based catalyst according to claim 1 under the condition of a deep eutectic solvent, wherein the catalyst is prepared by the following steps in the step (3): weighing RuCl3·xH2O, adding a small amount of deionized water to prepare a solution, and adding Nb2O5、ZSM-5、HY、γ-Al2O3Catalyst carrier, wherein the loading amount of metal Ru is 5wt.%, stirring at normal temperature for 10-12h, soaking for 20-24h, baking at 105 ℃ for 10-12h, roasting at 450 ℃ for 3h in a tube furnace under nitrogen atmosphere, reducing at 400 ℃ for 3h under hydrogen atmosphere, and reacting under N2/O2Passivating for 1h at normal temperature in the atmosphere.
5. The method for hydrodeoxygenation of lignin by using the ruthenium-based catalyst under the condition of the deep eutectic solvent according to claim 4, wherein the roasting temperature rise rate under the nitrogen atmosphere is 2-3 ℃/min, and the nitrogen flow is 30-50 ml/min.
6. The method for hydrodeoxygenation of lignin by using the ruthenium-based catalyst under the condition of the deep eutectic solvent according to claim 4, wherein the reduction heating rate is 2-3 ℃/min under a hydrogen atmosphere, and the hydrogen flow is 30-50 ml/min.
7. The method for hydrodeoxygenation of lignin with a ruthenium-based catalyst under deep eutectic solvent conditions as claimed in claim 4, wherein N is2/O2Under atmosphere O2Content 1%, N2/O2The flow rate is 30-50 ml/min.
8. The method for hydrodeoxygenation of lignin under deep eutectic solvent conditions by a ruthenium-based catalyst according to claim 1, wherein the hydrogen pressure in step (3) is 1 MPa.
Technical Field
The invention belongs to the field of lignin hydrodeoxygenation, and particularly relates to a method for hydrodeoxygenation of lignin by a ruthenium-based catalyst under the condition of a deep eutectic solvent.
Background
The lignocellulose biomass mainly comprises three components of lignin, cellulose and hemicellulose, and the lignin is a unique renewable natural high molecular resource containing an aromatic structure, so the lignin has great potential in the aspects of producing fuels, biomass-based materials and phenolic compounds from fossil sources, but the lignin, the cellulose and the hemicellulose are difficult to directly utilize due to the complex chemical bond connection, and therefore the lignin needs to be separated from the three components by adopting a certain method. In recent years, most of lignin used for hydrodeoxygenation is organosolv lignin, and the organosolv lignin needs to consume a large amount of organosolv during extraction, and finally needs to be precipitated by water and also consumes a large amount of water. Some deep eutectic solvents have better solubility to lignin and hardly dissolve to cellulose, so that the selective separation of the cellulose and the lignin can be realized according to different solubilities. The organic solvent lignin needs to be added with additional reaction solvents such as water, ethanol and the like in the subsequent HDO process, so that the lignin dissolved by the deep eutectic solvent can save the organic solvent needed in the lignin extraction process, and the addition of the reaction solvent in the HDO process is also reduced. In an acidic deep eutectic solvent, higher requirements are put on a catalyst for providing lignin HDO, such as high stability, strong acid resistance, high catalytic selectivity and the like in DES. Therefore, it is necessary to prepare a catalyst with high catalytic activity, high acid resistance and high selectivity for HDO of lignin in a deep eutectic solvent system to improve the HDO level of lignin.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for hydrodeoxygenating lignin by using a ruthenium-based catalyst under the condition of a deep eutectic solvent.
The technical scheme of the invention is as follows.
A method for hydrodeoxygenation of lignin by a ruthenium-based catalyst under the condition of a deep eutectic solvent is characterized by comprising the following steps:
(1) preparation of ChCl: acetic acid Deep Eutectic Solvent (DES);
(2) adding the hydrothermal residue and the DES prepared in the step (1) into a conical flask, reacting for 3-4h at the temperature of 100-120 ℃, and performing vacuum filtration to obtain a DES filtrate in which lignin is dissolved; the hydrothermal residue: DES is 1:20 g/g;
(3) adding a deep eutectic solvent for dissolving lignin and 50-300mg of catalyst into a high-pressure reaction kettle in a hydrogen atmosphere, and reacting at the temperature of 120-280 ℃ for 2-15 hours to obtain the lignin-rich low-eutectic solvent; the catalyst is Ru/Nb2O5、Ru/ZSM-5、Ru/HY、Ru/γ-Al2O3Or Ru/C;
(4) after the reaction is finished, cooling the reaction kettle to room temperature by using cold water, carrying out vacuum filtration under reduced pressure, pouring the obtained filtrate into a separating funnel, adding 30-40ml of ethyl acetate, and carrying out qualitative and quantitative analysis on the obtained upper layer liquid by adopting gas chromatography and mass spectrometry (GC-MS) and gas chromatography (GC-FID).
Further, in the step (1), the hydrogen bond acceptor is choline chloride (ChCl) and the hydrogen bond donor is acetic acid, wherein the molar ratio of the ChCl to the acetic acid is 1:2-1:4, the ChCl and the acetic acid are added into a beaker and react for 1-3h at 75-85 ℃ to obtain a clear and transparent solution, namely the prepared DES.
Further, in the step (2), the preparation method of the hydrothermal residue comprises the following steps: reacting eucalyptus powder with water at a solid-to-liquid ratio of 1:10-1:15g/ml at 150-180 ℃ for 0.5-1.5h in a nitrogen atmosphere, filtering under reduced pressure, and drying at 90-110 ℃ to obtain hydrothermal residue.
Further, in the step (3), a preparation method of the catalystThe method comprises the following steps: weighing RuCl3·xH2O, adding a small amount of deionized water to prepare a solution, and adding Nb2O5、ZSM-5、HY、γ-Al2O3Catalyst carrier, wherein the loading amount of metal Ru is 5wt.%, stirring at normal temperature for 10-12h, soaking for 20-24h, baking at 105 ℃ for 10-12h, roasting at 450 ℃ for 3h in a tube furnace under nitrogen atmosphere, reducing at 400 ℃ for 3h under hydrogen atmosphere, and reacting under N2/O2Passivating for 1h at normal temperature in the atmosphere.
Furthermore, the roasting heating rate is 2-3 ℃/min under the nitrogen atmosphere, and the nitrogen flow is 30-50 ml/min.
Furthermore, the reduction heating rate is 2-3 ℃/min under the hydrogen atmosphere, and the hydrogen flow is 30-50 ml/min.
Further, N2/O2Under atmosphere O2Content 1%, N2/O2The flow rate is 30-50 ml/min.
Further, the hydrogen pressure in step (3) is 1 MPa.
In the invention, the Ru/Nb is prepared by adopting an immersion method2O5、Ru/ZSM-5、Ru/HY、Ru/γ-Al2O3Catalyst, commercially available Ru/C catalyst was purchased.
Compared with the prior art, the invention has the following advantages:
according to the invention, the deep eutectic solvent is used for extracting lignin and the hydrodeoxygenation of the lignin are organically combined, so that a large amount of organic solvent required for extracting the lignin and reaction solvent required for adding the lignin HDO are saved, the application range of component separation by using the deep eutectic solvent is widened, and the difference of catalytic activity of different catalysts in a ChCl-acetic acid DES system is researched. The catalyst has larger specific surface area and larger pore size, and the yield of liquid products reaches 20.53 percent and the yield of phenols reaches 18.16 percent after hydrodeoxygenation.
Drawings
FIG. 1 shows Ru/. gamma. -Al obtained in example 12O3The adsorption and desorption curve and the pore diameter distribution diagram of the catalyst.
Detailed Description
The following examples and drawings further illustrate the embodiments of the present invention, but the scope of the present invention is not limited to the following embodiments.
The products and phenolic monomers in the following examples were determined by gas chromatography combined with mass spectrometry (GC-MS) and gas chromatography (GC-FID) analysis, GC detection was calculated using internal standard and n-dodecane as internal standard. The catalyst was characterized by an ASAP2460 four-station fully automated specific surface area and pore size analyzer (pore size distribution calculated by BJH method).