CN-114797969-B - Preparation method of novel multifunctional polyionic liquid catalyst and catalytic preparation method of lignin-based aromatic compound

Abstract

The invention belongs to the technical field of new material synthesis, and discloses a preparation method of a novel multifunctional polyion liquid catalyst with regular hydrophobic mesoporous and Bronsted-Lewis acid sites and an aromatic monomer prepared by catalytic lignin. The novel multifunctional polyionic liquid catalyst provided by the invention is prepared by carrying out polymerization reaction on Bronsted-Lewis acidic ionic liquid monomers, vinyl modified Fe 3 O 4 nano particles and a long-chain carboxylate anion cross-linking agent with hydrophobicity. Wherein the Fe 3 O 4 nano-particles modified by terminal alkene play a role of a skeleton enhancer, so that the novel multifunctional polyion liquid has definite mesoporous channels. The invention prepares the lignin-based aromatic monomer yield of 24.6wt% through the synergistic catalysis of the acid site, the mesoporous limit and the hydrophobic microenvironment. The catalyst was reused 10 times, and no significant decrease in reaction yield was observed. The catalyst has good industrialized prospect in upgrading heavy carbon resources into high-added-value chemical products.

Inventors

• LIU ZHONGQIU
• YU YUANYUAN
• YING ANGUO
• LIU YUJING
• WANG MEIYING

Assignees

• 曲阜师范大学

Dates

Publication Date

20260512

Application Date

20211207

Claims (6)

1. 1. A preparation method of a multifunctional polyion liquid catalyst is characterized in that the multifunctional polyion liquid catalyst is prepared by polymerization reaction of Bronsted-Lewis acid ion liquid, vinyl modified Fe 3 O 4 nano particles and long-chain carboxylate anion cross-linking agent monomers with hydrophobicity, when the vinyl modified Fe 3 O 4 nano particles participate in the polymerization, the carbon chain length of the cross-linking agent monomers is 6, and the molar ratio of Bronsted-Lewis acid ion liquid to long-chain carboxylate anion cross-linking agent is 1:2, the multifunctional polyion liquid catalyst with regular hydrophobic mesopores and with Bronsted-Lewis acid sites is prepared, and the preparation method of the multifunctional polyion liquid comprises the following steps: (1) Preparing Bronsted-Lewis acidic ionic liquid, namely reacting equimolar amount of 1-vinylimidazole and 1, 3-propane sultone to form quaternary ammonium salt, acidifying by hydrochloric acid to obtain salt with sulfonic acid groups, and then reacting with FeCl 3 ; (2) Preparing vinyl modified Fe 3 O 4 nano-particles, namely carrying out ultrasonic treatment on the Fe 3 O 4 nano-particles and vinyl triethoxysilane in ethanol for 2 hours at room temperature, then adding NH 3 ·H 2 O to adjust the pH to 9, vigorously mechanically stirring at 80 ℃ for 24 h, and washing with ethanol for 3 times; (3) The preparation of hydrophobic long-chain carboxylate anionic cross-linking agent includes adding 1, 2-dibromoethane and 1-vinyl imidazole in the molar ratio of 1 to 2 into acetone, magnetic stirring and heating reflux for 24-h to obtain yellowish solid, ion exchange with basic ion exchange resin and acidification with n-propionic acid, n-caproic acid and n-nonanoic acid.
2. 2. The method for preparing a multifunctional polyionic liquid catalyst according to claim 1, wherein the molar ratio of the salt with a sulfonic acid group to FeCl 3 is 1:0.25-2.25.
3. 3. The method for preparing a multifunctional polyionic liquid catalyst according to claim 1, wherein the vinyl-modified Fe 3 O 4 nano-particles are used as a skeleton enhancer of mesoporous polymeric ionic liquid and are used for promoting the formation of regular mesopores in the multifunctional polyionic liquid catalyst.
4. 4. The method for preparing the multifunctional polyionic liquid catalyst according to claim 1, wherein after the catalytic reaction is finished, the catalyst is separated from the reaction mixture by the magnetic recovery device of the multifunctional polyionic liquid catalyst, so that the recycling is realized.
5. 5. A method for preparing an aromatic monomer by catalyzing lignin by using the multifunctional polyionic liquid catalyst obtained by the preparation method according to claim 1 is characterized in that 20mL n-hexane, 0.1 g of the multifunctional polyionic liquid catalyst and 0.2 g lignin are mixed in an autoclave, the initial hydrogen pressure is 4 MPa, the reaction temperature is 265 ℃, the reaction time is 20 h, and the lignin-based aromatic monomer is prepared.
6. 6. The method of claim 5, wherein the total lignin conversion is 47.9% and the lignin-based aromatic monomer yield is 24.6 wt%.

Description

Preparation method of novel multifunctional polyionic liquid catalyst and catalytic preparation method of lignin-based aromatic compound Technical Field The invention belongs to the technical field of new material synthesis, in particular to the technical field of preparation of lignin-based aromatic monomers, and particularly relates to a novel multifunctional polyion liquid catalyst for preparing lignin-based aromatic monomers, and a preparation method and application thereof. Background Aromatic monomers are key raw materials for the manufacture of a variety of high value-added chemicals, almost all of which are currently obtained from non-renewable fossil fuels. With the rapid exhaustion of fossil resources and the increasing demand for aromatic monomers, the efficient conversion of renewable lignin to aromatic monomers is of great importance, and also presents many challenges, such as the high degree of crosslinking and recalcitrant structure of lignin, which makes depolymerization of lignin difficult. In view of the sustainable development of society and environment, development of advanced technology for valorizing lignin efficiently into high value-added chemicals is urgently needed. Liquid acid catalysts have been widely used in many liquid acid catalytic processes due to their high acid strength, excellent catalytic activity and uniform distribution of acid sites. Although liquid acid catalysts have high catalytic performance in catalyzing lignin, they also cause serious corrosion damage to equipment and are difficult to separate from the liquid reaction mixture. In contrast, solid acid catalysts have some advantages over liquid acid catalysts, such as less corrosiveness, environmental friendliness, and high safety. In particular, solid acid catalysts are relatively easier to separate and recover than liquid acid catalysts. Therefore, there is an urgent need to develop new solid acid catalysts for the directional conversion of lignin to aromatic monomers. Ionic liquids, in particular proton-type ionic liquids, are very important functional liquids. A particular advantage of ionic liquids is that specific anionic moieties can be designed. The metal chloride anion functionalized ionic liquid overcomes the defects of strong corrosiveness, easy hydrolysis, easy deactivation and the like of metal chloride. However, the high mass transfer resistance resulting from the high viscosity and low surface area reduces the competitiveness of metal chloride functionalized ionic liquids as catalysts for industrial applications. Polyionic liquids are also a macromolecular structure, incorporating polyionic liquids into the polymer backbone makes it possible to solve the problems associated with the monomers described above. The mesoporous polyionic liquid has adjustable mesoporous structure and chemical component adjustment, is a novel multifunctional porous material, and is formed by copolymerizing functional ionic liquid, a crosslinking agent and other monomers. The regular hydrophobic mesoporous polyionic liquid catalyst with Bronsted-Lewis acid sites is difficult to prepare by the conventional method. Disclosure of Invention In order to overcome the problems in the related art, the invention provides a novel multifunctional polyion liquid catalyst for preparing lignin-based aromatic monomers, and a preparation method and application thereof. The catalyst provided by the invention is a novel multifunctional polyion liquid which is efficient, environment-friendly, has Bronsted-Lewis acid part, definite mesoporous structure and unique hydrophobicity, and the preparation method comprises the following steps: 1) The preparation method of the Bronsted-Lewis acidic site ionic liquid comprises the steps of forming required quaternary ammonium salt by using equimolar amounts of 1-vinylimidazole and 1, 3-propane sultone, acidifying by using hydrochloric acid to obtain salt with sulfonic acid groups, and finally reacting with FeCl 3. 2) The preparation method of the hydrophobic long-chain carboxylate anion cross-linking agent comprises the steps of adding 1, 2-dibromoethane and 1-vinylimidazole in a molar ratio of 1:2 into acetone, magnetically stirring, heating and refluxing for 24 hours to obtain a pale yellow solid, and carrying out ion exchange through alkaline ion exchange resin. Finally, n-propionic acid, n-hexanoic acid and n-nonanoic acid were used for acidification, respectively. 3) The preparation method of the vinyl modified Fe 3O4 nano-particles comprises the steps of carrying out ultrasonic treatment on the Fe 3O4 nano-particles and vinyl triethoxysilane in ethanol for 2 hours at room temperature, then adding NH 3·H2 O into the mixed solution to adjust the pH value of the solution to 9, then carrying out vigorous mechanical stirring at 80 o ℃ for 24 hours, and finally washing with ethanol for 3 times. 4) The preparation method of the novel multifunctional polyionic liquid catalyst comprises the steps of mixi