Amine blends using concentrated piperazine

Le Li, Alexander K. Voice, Han Li, Omkar Namjoshi, Thu Nguyen, Yang Du, Gary T. Rochelle

Research output: Contribution to journalConference articlepeer-review


Blends using concentrated (25-35 wt %) piperazine (PZ) were characterized as solvents for CO2 capture at typical coal flue gas conditions. The new blends are 6 m PZ/2 m hexamethylenediamine (HMDA), 6 m PZ/2 m diaminobutane (DAB), 6 m PZ/2 m bis(aminoethyl)ether (BAE), 5 m PZ/2 m aminoethylpiperazine (AEP), and 5 m PZ/2.3 m 2-amino 2-methyl-propanol (AMP). The CO2 absorption rate of the blends was measured using a wetted wall column (WWC). The CO2 vapor liquid equilibrium was measured at 20-160 °C. Amine vapor pressure measurements are reported to show potential volatility at practical conditions. The rate of thermal degradation was measured from 135 to 175 °C. Oxidative degradation was measured in two semi-batch experiments with different O2 rate at absorber conditions. Advanced parameters are introduced to demonstrate the overall rate and energy performance of the solvents in a real process. The performance of 7 m MEA, 8 m PZ, and six other competitive PZ blends are evaluated based on previous results and presented as basis of comparison. All of the PZ blends have better solubility window than 8 m PZ, with no precipitation at rich loading. The absorption rate of the concentrated PZ blends is similar to that of 8 m PZ and 1.5-2 times higher than 7 m MEA; the solvent capacity is about 20% lower than 8 m PZ and 15% higher than 7 m MEA. Among all of the PZ blends, 5 m PZ/5 m MDEA has the best combination of rate and capacity. Blends using HMDA, AEP, BAE, AMP, and MEA have a high heat of CO2 absorption. Blends using MEA, MDEA, and AMP are not thermally stable, while other blends have good thermal stability. The combination of high Habs and thermal stability leads to good overall energy performance, which is observed for 6 m PZ/2 m HMDA, 6 m PZ/2 m BAE and 5 m PZ/2 m AEP. AMP has relatively high volatility, whereas BAE and AEP are expected to have low volatilities. The only drawback of 6 m PZ/2 m BAE is its high oxidation rate. 6 m PZ/2 m HMDA and 6 m PZ/2 m DAB have good oxidative stability. PZ blends using low viscosity amines will have high absorption rate, and tertiary and hindered amines will contribute to high capacity. Amines with high pKa will improve the blend Habs. For thermal stability, alkanolamines should not be used together with PZ. Highly viscous blends such as 6 m PZ/2 m HMDA are expected to have 10-20% higher cost associated with cross-exchanger design and operation than solvents with low viscosity.

Original languageEnglish (US)
Pages (from-to)353-369
Number of pages17
JournalEnergy Procedia
StatePublished - 2013
Externally publishedYes
Event11th International Conference on Greenhouse Gas Control Technologies, GHGT 2012 - Kyoto, Japan
Duration: Nov 18 2012Nov 22 2012


  • Absorption rate
  • Degradation
  • Oxidation
  • Piperazine
  • Process performance
  • Solvent blends
  • Volatility

ASJC Scopus subject areas

  • General Energy


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