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相关概念视频

Types of Step-Growth Polymers: Polyesters01:20

Types of Step-Growth Polymers: Polyesters

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The introduction of polyesters has brought major development to the textile industry. The wrinkle-free behavior of polyester blends has eliminated the need for starching and ironing clothes.
Polyesters are commonly prepared from terephthalic acid and ethylene glycol; the crude product is known as poly(ethylene terephthalate) or PET. However, polyesters are synthesized industrially by transesterification of dimethyl terephthalate with ethylene glycol at 150 °C. The two reactants and the...
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Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

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The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
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Polymer Classification: Architecture01:14

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Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
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Step-Growth Polymerization: Overview01:03

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Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
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Polymers02:34

Polymers

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The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the...
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Olefin Metathesis Polymerization: Overview01:13

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Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
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相关实验视频

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Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer
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在聚废物回收利用中去聚合机制和闭环评估.

Jingjing Cao1, Huaxing Liang1, Jie Yang2

  • 1CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China.

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概括
此摘要是机器生成的。

这项研究提出了一种高效的聚乙烯二甲 (PET) 废物回收方法,使用氧气空缺催化剂. 该过程显著提高了单体生产率,并为可持续的塑料废物管理提供了大量的能源节约.

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科学领域:

  • 材料科学 材料科学 材料科学
  • 化学工程是化学工程的重要组成部分.
  • 环境科学 环境科学

背景情况:

  • 聚乙烯二甲 (PET) 废物对环境构成重大挑战.
  • 酒精分解,包括甲醇分解和糖分解,为PET废弃物的价值化提供了一个有前途的途径,可以将其转化为有价值的单体,如二甲基甲甲酸盐 (DMT) 和二-2-乙基甲甲酸盐 (BHET).
  • 现有的PET醇化方法通常效率低,需要恶劣的反应条件.

研究的目的:

  • 开发一个高效和可持续的催化系统,用于在空气下进行PET醇化.
  • 为了阐明由氧空缺促进的PET脱聚合的反应机制.
  • 评估开发的闭环PET回收过程的环境和经济可行性.

主要方法:

  • 在环境空气下使用富含氧气空缺 (Vo) 的催化剂进行PET醇化 (甲醇化和糖化).
  • 使用现场光谱和密度函数理论 (DFT) 计算来研究反应途径.
  • 进行了生命周期评估 (LCA),以评估节能,温室气体排放和成本效益,包括使用PET织废料.

主要成果:

  • 对DMT (505.2 g·gcat-1·h-1) 和BHET (957.1 g·gcat-1·h-1) 实现了高空间时间产量 (STY),与N2条件相比,代表了51倍和28倍的改进.
  • 在Vo-Zn2+-O-Fe3+位点确定了O2辅助的甲醇激活,作为键裂解的关键机制.
  • 证明了显著的环境效益:56.0%的节能和44.5%的温室气体排放减少.
  • 展示了经济优势,在使用PET织废料时,运营成本降低了58.4%.

结论:

  • 富含Vo的催化剂可以在空气下实现高效的PET醇化,显著优于惰性大气下的反应.
  • 该研究提供了对催化过程的机理理解,强调了氧空缺和特定活性位点的关键作用.
  • 这种方法为闭环PET回收提供了一个可持续且经济可行的解决方案,解决了塑料废物积累的全球挑战.