The cationic ring-opening polymerization of azetidine to form branched poly(propylenimine) (PPI) is investigated for the purpose of evaluating the utility of PPI/silica composite adsorbents for CO₂ capture. The polymerization kinetics and primary:secondary:tertiary amine distribution are monitored with ¹H NMR during reaction with varied synthesis conditions (i.e., reaction time 20–150 h), temperature (343–353 K), and monomer to acid initiator (here, HClO₄) ratio. It is found that primary amines are converted to tertiary amines with increased polymerization time, while the addition of monomer over the first 6 h of polymerization increases the primary amine content. This suggests a mechanism where the monomer is rapidly consumed, leaving dimers or small oligomers that still contain rings as key reaction centers. The synthesized polymer is neutralized with either NH₄OH or a basic resin and impregnated into mesoporous silica (SBA-15). The CO₂ capture properties of these composite adsorbents are investigated, giving information about the effectiveness of the acid neutralization processes.

中文翻译：

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氮杂环丁烷聚合制备基于聚丙二胺的CO ₂吸附剂的见解

为了评估PPI /二氧化硅复合吸附剂在CO ₂捕集中的用途，研究了氮杂环丁烷的阳离子开环聚合反应以形成支链聚丙二胺（PPI）。聚合反应动力学和伯：仲：叔胺分布与监测¹具有不同的合成条件（即，反应时间20-150 h）中，温度（343-353 K），和单体酸引发剂（在此反应期间H NMR，盐酸₄） 比率。发现随着增加的聚合时间，伯胺被转化为叔胺，而在聚合的前6小时内单体的添加增加了伯胺的含量。这表明单体被快速消耗的机制，从而留下仍含有环作为关键反应中心的二聚体或小的低聚物。合成的聚合物用NH ₄ OH或碱性树脂中和，并浸渍到中孔二氧化硅（SBA-15）中。对这些复合吸附剂的CO ₂捕集性能进行了研究，从而给出了有关酸中和过程有效性的信息。