13C-NMR study of acid dissociation constant (pKa) effects on the CO2 absorption and regeneration of aqueous tertiary alkanolamine-piperazine blends

Miho Nitta, Kogoro Hayashi, Yukio Furukawa, Hiroshi Sato, Yasuro Yamanaka

Research output: Contribution to journalConference article


We have studied the concentration changes of chemical species such as CO3 2-/HCO3 -, amine/protonated species, carbonate/protonated species, carbamates/protonated species, etc. in the course of CO2 absorption and those after CO2 release upon heating at 93 °C for 30 min for aqueous blends of piperazine (PZ) and each of 11 tertiary alkanolamines using 13C-NMR spectroscopy. The initial rates of CO2 capture of the blends ranged between 0.125 and 0.167 mol/L min, which were contributed by the rapid formation of PZ monocarbamate. A positive linear correlation was found between the CO2 release amounts of the blends upon heating and the pKa values of the tertiary alkanolamines. The CO2 content captured as PZ mono- And biscarbamates decreased upon heating in the pKa range smaller than 9.34, whereas it increased upon heating in the pKa range higher than 9.55. A tertiary alkanolamine having the pKa smaller than 9.34 is promising as a blend amine with PZ.

Original languageEnglish
Pages (from-to)1863-1868
Number of pages6
JournalEnergy Procedia
Publication statusPublished - 2014 Jan 1
Event12th International Conference on Greenhouse Gas Control Technologies, GHGT 2014 - Austin, United States
Duration: 2014 Oct 52014 Oct 9



  • C-NMR
  • Acid dissociation constant
  • Carbamate
  • Ccs
  • Piperazine
  • Tertiary amine

ASJC Scopus subject areas

  • Energy(all)

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