Decomposition of nitrosamines in CO2 capture by aqueous piperazine or monoethanolamine

Environ Sci Technol. 2014 May 20;48(10):5996-6002. doi: 10.1021/es404949v. Epub 2014 Apr 29.

Abstract

Amine scrubbing is an efficient method for carbon capture and sequestration, but secondary amines present in all amine solvents can form carcinogenic nitrosamines. Decomposition kinetics for n-nitrosopiperazine (MNPZ), nitrosodiethanolamine (NDELA), and nitroso-(2-hydroxyethyl) glycine (NHeGly) were measured over a range of temperature, base concentration, base strength, and CO2 loading pertinent to amine scrubbing. MNPZ and NDELA decomposition is first order in the nitrosamine, half order in base concentration, and base-catalyzed with a Brønsted slope of β = 0.5. The activation energy is 94, 106, and 112 kJ/mol for MNPZ, NDELA, and NHeGly, respectively. MNPZ readily decomposes at 150 °C in 5 M piperazine, making thermal decomposition an important mechanism for MNPZ control. However, NHeGly and NDELA are too stable at 120 °C in 7 M monoethanolamine (MEA) for thermal decomposition to be important. Base treatment during reclaiming could rapidly and selectively decompose NHeGly and NDELA to mitigate nitrosamine accumulation in MEA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon Dioxide / chemistry*
  • Environment
  • Ethanolamine / chemistry*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Magnetic Resonance Spectroscopy
  • Nitrosamines / chemistry*
  • Piperazine
  • Piperazines / chemistry*
  • Sodium Hydroxide / chemistry
  • Temperature
  • Water / chemistry*

Substances

  • Nitrosamines
  • Piperazines
  • Water
  • Carbon Dioxide
  • Piperazine
  • Sodium Hydroxide
  • Ethanolamine
  • N-(2-hydroxyethyl)-N-carboxymethylnitrosamine