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CN-120795212-B - Preparation method of low molecular weight polyacrylamide

CN120795212BCN 120795212 BCN120795212 BCN 120795212BCN-120795212-B

Abstract

The invention discloses a preparation method of low molecular weight polyacrylamide in the technical field of high molecular synthesis and functional material modification, which comprises the steps of preparing a bimetal doped hierarchical pore carbon nano tube-covalent organic framework composite modified material, and performing surface functionalization, covalent organic framework layer growth, bimetal ion doping and subsequent reduction and calcination treatment on a multi-wall carbon nano tube. Adding deionized water, acrylamide and the modified material into a three-neck flask, introducing nitrogen, stirring to dissolve the acrylamide, preparing an oxidation-reduction initiator solution, dropwise adding the initiator solution into the system under the protection of nitrogen, and carrying out a constant-temperature water bath polymerization reaction at 19-21 ℃. And after the polymerization is finished, washing and filtering a product system, and finally obtaining the low-molecular-weight polyacrylamide by adopting a vacuum freeze drying method. The polyacrylamide prepared by the method has low and controllable molecular weight and good solubility, salt resistance and other performances.

Inventors

  • CHENG HAI
  • LIU QUAN
  • LI SHUAIJUN

Assignees

  • 格润化学(东营)有限公司

Dates

Publication Date
20260512
Application Date
20250812

Claims (9)

  1. 1. The preparation method of the low molecular weight polyacrylamide is characterized by comprising the following steps of: S1, adding deionized water, acrylamide and a bimetal doped hierarchical pore carbon nano tube-covalent organic framework composite modified material into a three-neck flask with a stirrer, a nitrogen inlet tube and a condenser tube, introducing nitrogen, and stirring until the acrylamide is completely dissolved; S2, respectively dissolving potassium persulfate and sodium sulfite in deionized water to prepare an oxidation-reduction initiator solution; S3, dropwise adding the oxidation-reduction initiator solution into the pretreatment system in the step S1 under the protection of continuous nitrogen, and immediately transferring the reaction system to a constant-temperature water bath at 19-21 ℃ for polymerization reaction; s4, after polymerization, washing a product system by deionized water, dispersing the precipitate in the deionized water to prepare a solution, filtering the solution by a filter membrane, and finally drying the solution by a vacuum freeze drying method; The preparation method of the bimetal doped hierarchical pore carbon nano tube-covalent organic framework composite modified material comprises the following steps: A1, dispersing multi-wall carbon nanotubes in a mixed acid solution, carrying out ultrasonic dispersion in an ice bath, carrying out reflux reaction at 60-64 ℃, diluting with deionized water to pH=6-7 after cooling, carrying out suction filtration, washing with deionized water to neutrality, and carrying out vacuum drying at 80-82 ℃, dispersing oxidized multi-wall carbon nanotubes in SOCl2, carrying out reflux reaction at 80-82 ℃ to obtain chlorinated multi-wall carbon nanotubes, then adding excessive ethylenediamine, carrying out reaction at 80-84 ℃ to obtain aminated multi-wall carbon nanotubes, finally dispersing the aminated multi-wall carbon nanotubes in a mixed solution of concentrated sulfuric acid and fuming sulfuric acid, carrying out sulfonation reaction at 60-64 ℃, washing with deionized water to neutrality, and drying at 100-102 ℃ to obtain the multi-level pore carbon nanotubes with carboxyl groups, amino groups and sulfonic groups on the surfaces; A2, dispersing the hierarchical pore carbon nano tube in a mixed solvent of mesitylene and ethanol, performing ultrasonic dispersion, adding 2,4, 6-tris (4-aminophenyl) -1,3, 5-triazine and 1, 4-terephthalic acid, performing ultrasonic dispersion, then adding acetic acid, transferring into a polytetrafluoroethylene reaction kettle, reacting at 120-124 ℃, cooling, centrifugally collecting solid, washing with tetrahydrofuran, ethanol and deionized water in sequence, and performing vacuum drying at 80-82 ℃ to obtain the carbon nano tube with the covalent organic framework layer grown on the surface; A3, dispersing the covalent organic framework layer carbon nano tube in deionized water, performing ultrasonic dispersion, sequentially adding ZrCl4 and Ce (NO 3) 3.6H2O aqueous solution, stirring at room temperature for reaction, centrifugally collecting solids, washing with deionized water, dispersing in ethanol, drying at 60-64 ℃, and roasting at 300-304 ℃ under the protection of nitrogen to obtain the bimetal doped hierarchical pore carbon nano tube-covalent organic framework composite modified material; a4, placing the bimetal doped hierarchical pore carbon nano tube-covalent organic framework composite modified material in a tube furnace, carrying out reduction treatment at 400-404 ℃ in a hydrogen atmosphere, and then calcining at 500-510 ℃ under the protection of nitrogen.
  2. 2. The method for preparing low molecular weight polyacrylamide according to claim 1, wherein in step S1, the nitrogen gas is introduced for 40 to 50 minutes.
  3. 3. The method for producing a low molecular weight polyacrylamide according to claim 1, wherein the temperature of the oxidation-reduction initiator solution in step S2 is 3 to 5 ℃.
  4. 4. The method for preparing low molecular weight polyacrylamide according to claim 1, wherein in step S3, the dropping time is 15 to 20 minutes.
  5. 5. The method for preparing low molecular weight polyacrylamide according to claim 1, wherein in step S4, the number of times of deionized water washing is 4 to 5, the pore size of the filter membrane is 0.22 to 0.24 μm, the temperature of vacuum freeze drying is-45 ℃, and the drying time is 36 to 40 hours.
  6. 6. The method for preparing low molecular weight polyacrylamide according to claim 1, wherein in step A1, the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1, the reflux reaction time is 4-6 hours at 60-64 ℃, the vacuum drying time is 12-14 hours at 80-82 ℃, the reflux reaction time is 12-14 hours at 80-82 ℃, the reaction time is 24-30 hours at 80-84 ℃, and the sulfonation reaction time is 6-8 hours at 60-64 ℃.
  7. 7. The method for preparing low molecular weight polyacrylamide according to claim 1, wherein in the step A2, the reaction time is 72 to 80 hours at 120 to 124 ℃ and the vacuum drying time is 12 to 14 hours at 80 to 82 ℃.
  8. 8. The method for preparing low molecular weight polyacrylamide according to claim 1, wherein in the step A3, the stirring reaction time is 12-14h at room temperature and the roasting time is 2-4h at 300-304 ℃.
  9. 9. The method for producing a low molecular weight polyacrylamide according to claim 1, wherein in step A4, the reduction treatment time at 400 to 404 ℃ is 3 to 4 hours, and the calcination time at 500 to 510 ℃ is 2 to 4 hours.

Description

Preparation method of low molecular weight polyacrylamide Technical Field The invention relates to the technical field of high molecular synthesis and functional material modification, in particular to a preparation method of low molecular weight polyacrylamide. Background In the industrial fields of petroleum exploitation, water treatment, papermaking and the like, low molecular weight polyacrylamide becomes an irreplaceable key high molecular material by virtue of low viscosity, high permeability and good reactivity. The traditional high molecular weight polyacrylamide is difficult to inject and low in diffusion efficiency due to the fact that the molecular weight is generally over million, and the viscosity is too high in the scenes of deep profile control, low permeability reservoir oil displacement, complex stratum water treatment and the like, so that the actual requirements are difficult to meet. In contrast, low molecular weight polyacrylamides with molecular weights below one hundred thousand have not only significantly improved flowability, but also have demonstrated unique advantages in the precise regulation of heterogeneous reservoirs and stable applications in high salt environments through moderate chain length balance thickening and permeability properties. However, the traditional free radical polymerization method is extremely easy to cause chain growth runaway due to extremely high polymerization activity of acrylamide monomers, the molecular weight of the final product is generally higher, the molecular weight distribution is wide, and the low molecular weight product meeting the industrial requirements is difficult to stably obtain. To solve the above problems, researchers have attempted to regulate polymerization reactions by introducing chain transfer agents or inorganic nanoparticles. The chain transfer agent can reduce the molecular weight, but the residual chemical substances not only affect the purity of the product, but also can cause potential harm to the environment and subsequent application, and the inorganic nano particles have weak interaction with the acrylamide monomer due to strong surface inertia, so that the precise regulation and control of polymerization kinetics are difficult to realize, and the molecular weight distribution of the product is uneven and the performance is unstable. In recent years, metal organic frame materials are gradually used for polymerization regulation and control due to the high specific surface area and the designable pore structure, but the pore channel structure with micropores as the main component limits the monomer diffusion efficiency, the collapse of the structure is easy to occur under the high temperature condition, the stability is insufficient in a complex water phase system, and the dual requirements of industrial production on the durability and the controllability of the materials are difficult to meet. Aiming at the technical bottleneck, a novel modified material with high specific surface area, abundant active sites and excellent stability is developed, and the high-performance low-molecular-weight polyacrylamide is a key breakthrough direction for preparing high-performance low-molecular-weight polyacrylamide by precisely regulating and controlling the free radical polymerization process through the strong interaction of the modified material and a polymerization system. According to the invention, a bimetal doped hierarchical pore carbon nanotube and covalent organic framework composite modified material is innovatively adopted, monomer diffusion is promoted through a hierarchical pore structure, polymerization free radicals are captured and stabilized by utilizing coordination action and redox characteristics of bimetal ions, and meanwhile, quenching of the free radicals is accelerated by an electron delocalization effect of a covalent organic framework, so that precise inhibition of polymerization reaction chain growth is realized. The preparation process of the modified material relates to surface functionalization of the multiwall carbon nanotube to enhance hydrophilicity and interaction, in-situ growth of a covalent organic framework to construct an ordered porous structure, precise doping of bimetal ions to regulate and control active site distribution, high-temperature reduction and calcination activation to optimize material structure and performance, and finally, controllable synthesis of low-molecular-weight polyacrylamide is realized through a low-temperature redox initiation system, so that a brand new technical path is provided for precise preparation of industrial-grade low-molecular-weight polyacrylamide. Disclosure of Invention The invention aims to provide a preparation method of low-molecular-weight polyacrylamide, which solves the technical problems of difficult control of molecular weight, wide distribution, poor material stability and residual harmful substances in the existing preparation method of lo