- Title
- The effect molecular structural variations has on the CO₂ absorption characteristics of heterocyclic amines
- Creator
- Robinson, K.; McCluskey, A.; Attalla, M.
- Relation
- Energy Procedia Vol. 4, p. 224-231
- Publisher Link
- http://dx.doi.org/10.1016/j.egypro.2011.01.045
- Publisher
- Elsevier BV
- Resource Type
- journal article
- Date
- 2011
- Description
- In-situ ATR FT-IR spectroscopy has been used to investigate the reaction between CO₂ and piperidine, as well as commercially available functionalised piperdine derivatives, e.g., those with methyl-, hydroxyl-, and hydroxyalkyl-substituents. The effect of the substituent’s on CO₂ absorption has been assessed in relation to the prevalent IR identifiable ionic reaction products, along with CO₂ absorption capacity and initial absorption rate. The results obtained highlight the enhanced reactivity of cyclic 2° amines compared to conventional 1° and 2° amines, MEA and DEA respectively. Formation of the COO⁻ derivatives of the 3- and 4-hydroxyl and hydroxyalkyl substituted piperidines were found to be kinetically less favourable than that of piperidine and the 3 and 4-methyl substituted piperdines. As the CO₂ loading of piperidine and the 3- and 4-substituted piperidines exceeded 0.5 mol CO₂/mol amine, hydrolysis of their COO⁻ derivative was observable in the IR spectral profiles. From the subset of amines analysed the 2-alkyl and 2-hydroxyalkyl substituted piperidines were found to favour HCO₃⁻ formation. Despite forming predominantly HCO₃⁻ these amines also exhibited initial absorption rates comparable to that of MEA and DEA, 2-MP in particular was found to exhibit a significantly higher initial absorption rate. Computational calculations at the B3LYP/6- 31+G∗∗ and MP2/6- 31+G∗∗ level of theory revealed that for the 2-alkyl and hydroxyalkyl substituted piperidines a combination of both the electronic effect exerted by the substituent and a reduction in the exposed area on the nitrogen atom will play a role in destabilising the COO⁻ derivative and increasing its susceptibility to hydrolysis.
- Subject
- CO₂; heterocyclic; amine; reactivity; infrared
- Identifier
- http://hdl.handle.net/1959.13/1064001
- Identifier
- uon:17427
- Identifier
- ISSN:1876-6102
- Language
- eng
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