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CN-121972220-A - Guanidine-functionalized polyacrylonitrile fiber and preparation method and application thereof

CN121972220ACN 121972220 ACN121972220 ACN 121972220ACN-121972220-A

Abstract

The application is suitable for the technical field of materials, and provides a guanidine group functionalized polyacrylonitrile fiber and a preparation method and application thereof, and the application constructs a heterogeneous catalyst with high alkalinity, excellent mechanical stability and convenient recovery through covalently introducing guanidine groups on the surface of the polyacrylonitrile fiber, the hydrogen bond in the molecule of the benzamide monohydroxylate product is used for promoting the spontaneous desorption of the product, so that high-activity catalysis is realized, meanwhile, the poisoning of the catalyst is avoided, the long-term circulation performance is ensured, and a new path is provided for the greening and industrialization of guanidine catalysts. The method has the advantages that the method takes cheap organic amine as a medium, and adopts the method for covalent grafting of guanidine groups for the first time under simple conditions to prepare the alkaline heterogeneous catalyst with low cost and mechanical stability, the water phase catalysis is compatible with green chemistry, the selectivity is precisely controlled, the side reaction is inhibited, the fiber is easy to filter and recycle, the structure and activity in the circulation are stable, the reaction is mild, the substrate adaptability is good, and the large-scale popularization is easy.

Inventors

  • TAO MINLI
  • ZHANG YANFEI
  • WANG HAO
  • MA NING

Assignees

  • 天津大学

Dates

Publication Date
20260505
Application Date
20251201

Claims (10)

  1. 1. The guanidino-functionalized polyacrylonitrile fiber is characterized by having a structural general formula: 。
  2. 2. A method of making the guanidino-functionalized polyacrylonitrile fiber according to claim 1, comprising: immersing polyacrylonitrile fiber into a mixed system of N-methyl-1, 2-ethylenediamine and distilled water, heating and refluxing for reaction, and washing and drying to obtain modified fiber; and (3) under the nitrogen atmosphere, carrying out heating reflux reaction on the modified fiber and the dimethyl cyanamide, and washing and drying to obtain the guanidyl functional polyacrylonitrile fiber.
  3. 3. The method for preparing the guanidine-functionalized polyacrylonitrile fiber according to claim 2, wherein the heating temperature is 100-135 ℃ and the reaction time is 50-70min in the step of immersing the polyacrylonitrile fiber in a mixed system of N-methyl-1, 2-ethylenediamine and distilled water, performing a heating reflux reaction, and then performing washing and drying treatment.
  4. 4. The method for preparing a guanidino-functional polyacrylonitrile fiber according to claim 3, wherein the heating temperature is 130 ℃ and the reaction time is 60min.
  5. 5. The method for preparing the guanidyl functional polyacrylonitrile fiber according to claim 1, wherein in the step of carrying out heating reflux reaction on the modified fiber and the dimethyl cyanamide under the nitrogen atmosphere, and carrying out washing and drying treatment, the heating temperature is 95-110 ℃ and the reaction time is 9-12h.
  6. 6. The method for preparing the guanidino-functional polyacrylonitrile fiber according to claim 5, wherein the heating temperature is 105 ℃ and the reaction time is 12 hours.
  7. 7. The method for preparing the guanidine-functionalized polyacrylonitrile fiber according to claim 2, wherein the step of immersing the polyacrylonitrile fiber in a mixed system of N-methyl-1, 2-ethylenediamine and distilled water, performing a heating reflux reaction, and then performing washing and drying treatment to obtain the modified fiber comprises the following steps: immersing 2.00 g polyacrylonitrile fiber into a mixed system of 40.0 mL N-methyl-1, 2-ethylenediamine and 20.0 mL distilled water, heating and refluxing for reaction at 130 ℃ for 60min, washing with 60-70 ℃ distilled water, and drying at 60 ℃ for 12h to obtain the modified fiber.
  8. 8. The method for preparing the guanidyl functionalized polyacrylonitrile fiber according to claim 1, wherein the step of heating and refluxing the modified fiber and the dimethyl cyanamide under the nitrogen atmosphere, and washing and drying the modified fiber to obtain the guanidyl functionalized polyacrylonitrile fiber comprises the following steps: and (3) under the nitrogen atmosphere, carrying out 105 ℃ heating reflux reaction on 1.0g of the modified fiber and 25mL of dimethyl cyanamide for 12 hours, and washing with 60-70 ℃ ethanol and drying at 60 ℃ for 12 hours to obtain the guanidino functional polyacrylonitrile fiber.
  9. 9. Use of a guanidino-functionalized polyacrylonitrile fiber according to claim 1 for selectively catalyzing a benzamide monomethylation reaction.
  10. 10. A process for the preparation of a benzamide monohydroxylate comprising the steps of: Sequentially adding benzamide, paraformaldehyde, the guanidino-functional polyacrylonitrile fiber according to claim 1 and water into a reaction vessel, heating and stirring to perform a benzamide monohydroxylation reaction; after the reaction is finished, filtering and recovering the guanidine-functionalized polyacrylonitrile fiber, washing, extracting an organic phase, concentrating under reduced pressure, and purifying by a column chromatography to obtain a benzamide monohydroxylate product.

Description

Guanidine-functionalized polyacrylonitrile fiber and preparation method and application thereof Technical Field The application belongs to the technical field of materials, and particularly relates to a guanidino-functionalized polyacrylonitrile fiber, and a preparation method and application thereof. Background The methylolation reaction is one of important functionalization reactions of amide compounds, and by introducing hydroxymethyl into amide molecules, the reactivity and the molecular polarity of the amide compounds can be obviously improved, key active sites are provided for subsequent condensation, esterification, etherification and other reactions, and the methylolation reaction has wide application in synthesis of drug intermediates, preparation of polymer monomers and production of fine chemicals. Traditional methylolation reactions depend on small molecule basic catalysts such as sodium hydroxide, potassium hydroxide, triethylamine, pyridine, 1,5, 7-triazabicyclo [4.4.0] decane (TBD) and the like. Although the catalyst can activate an amide carbonyl group and promote nucleophilic attack of formaldehyde to generate a methylolated product, the catalyst has inherent defects that firstly, the catalyst is mostly a homogeneous system and is difficult to separate from the product after reaction, so that the catalyst is wasted, the purification cost of the product is high and serious environmental burden is caused, and secondly, the homogeneous alkali system is easy to cause excessive methylolation or condensation side reaction, so that the selectivity of the target product is obviously reduced. In order to solve the separation and recovery problems of homogeneous catalysis, researchers propose a guanidine catalyst immobilization thought. Guanidine groups have the dual characteristics of strong alkalinity and hydrogen bond donor and acceptor, and show excellent performance in organic base catalytic reaction. In the prior art, the curing catalyst containing aliphatic guanidine groups is used for crosslinking and curing the silane polymer, and the chiral guanidine catalyst of biaryl frameworks and quinine frameworks is applied to asymmetric Aldol and Michael reactions, so that the catalytic high efficiency and universality of guanidine structures are verified. However, these catalysts still exist in the form of soluble small molecules, belong to a homogeneous system, and cannot be recycled. Subsequent studies have attempted to immobilize guanidine groups to solid supports to form heterogeneous catalysts, such as immobilization to silica gel surfaces by silane coupling, or grafting to supports such as resins, magnetic nanoparticles, and the like. The immobilized catalyst has certain reusability in reactions such as transesterification, biodiesel synthesis and C-C bond construction, but has obvious defects that most of carriers are powdery or nano particles, the mechanical strength is low, the carriers are easy to run off in the stirring and filtering processes, the problems of difficult separation, complex operation and the like are faced in industrial amplification, most of guanidino groups are physically adsorbed or weakened chemical bond combination between the carriers, and the guanidino groups are easy to run off after multiple uses, so that the activity of the catalyst is attenuated. The polymer fiber material has high texture, high strength and surface chemical adjustability, and is attracting attention in the fields of adsorption, separation and catalysis. Polyacrylonitrile (PAN) fiber is used as a common organic polymer material, the molecular chain of the Polyacrylonitrile (PAN) fiber contains rich nitrile groups (-C.ident.N), functional modification can be realized through amination, amidation and other reactions, the Polyacrylonitrile (PAN) fiber has excellent thermal stability and chemical stability, the Polyacrylonitrile (PAN) fiber can keep complete structure in water phase or organic medium, and the fiber morphology is convenient for mechanical separation and recycling. The prior literature reports that guanidine salts or guanidine carbonates can act with PAN fibers to improve the thermal stability of the carbonization process, but the process is only used for material pretreatment, has no organic catalytic function, and does not relate to research on immobilized guanidine groups for molecular reaction catalysis. In summary, the prior art lacks a heterogeneous catalyst with high catalytic activity, high selectivity, good mechanical stability and recyclability, which is used for the methylolation reaction of amide compounds, and has technical bottlenecks in solving the problems of catalyst loss, difficult product separation, side reaction control and the like. Disclosure of Invention The embodiment of the application aims to provide a guanidino-functionalized polyacrylonitrile fiber and a preparation method and application thereof, and aims to solve the problems of difficult separation of a