Insights into Azetidine Polymerization for the Preparation of Poly(propylenimine)-Based CO₂ Adsorbents

Abstract

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.

Aziridines and azetidines: building blocks for polyamines by anionic and cationic ring-opening polymerization

“…section 2.5). 8 Furthermore, they noted an increase in molar masses in polymerization mixtures containing no monomeric species. This suggests that both monomer and polymer molecules are capable of activation and deactivation, thus making it more difficult to control the molecular weight and architecture of the resulting hbPEI.…”

“…In contrast, aziridine can only polymerize via CROP to produce (hyper)branched polyethylenimine (hbPEI) with little control over molecular weight, dispersity, and microstructure. [4][5][6][7][8] The situation is similar with azetidine ( Fig. 1), the nitrogen analog of oxetane, which also only forms hyperbranched poly(trimethylenimine) (hbPTMI) via CROP.…”

“…In 2017, Goethals' initial work on the polymerization of unsubstituted azetidine was confirmed by Sarazen and Jones. 8 They provided a report of the cationic polymerization of azetidine, which was impregnated onto a silica scaffold. These porous materials were then employed in the capturing of CO 2 , which is a promising preliminary application of PTMI.…”

Recent developments and consideration issues in solid adsorbents for CO2 capture from flue gas

“…All PEI modified materials exhibited reversible and stable CO 2 adsorption/desorption behaviors in the cycling tests. Jones CW groups contributed great work in grafted aminosilica adsorbents in the past two decades [93][94][95][96][97]. They prepared the hyperbranched aminosilica CO 2 adsorbents by the ring-opening polymerization of aziridine from mesoporous silica and amines.…”

Exploring the Acid Gas Sorption Properties of Oxidatively Degraded Supported Amine Sorbents

“…[51] To this end, there has seen a growing interest in propylene linked aminopolymers and dendrimers, which have been reported to show better oxidative stability than ethylene linked polymers during CO2 adsorption under oxidizing conditions. [51,52] While the influence of oxidative degradation has been well studied on many supported amine species relevant to CO2 capture, [51] scarce few reports exist on how this can influence the sorption properties of different amines for 'amine-poisoning' gases such as SO2 and NO2. As such, in this work, we contrast the influence of isolated primary, secondary and tertiary class 2 aminosilane species, anchored on mesoporous SBA-15, for SO2, NO2 and CO2 (under both simulated flue-gas and atmospheric conditions) under dry conditions to probe the lifetime of such species for selective acid gas sorption.…”