Decomposition of Nitrosamines in CO₂ Capture by Aqueous Piperazine or Monoethanolamine

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.

Recent progress and new developments in post-combustion carbon-capture technology with amine based solvents

“…However, a study recently published has managed to investigate the decomposition of nitrosamines specifically of those formed from PZ and MEA. Based on this study of decomposition kinetics under basic and stripper temperature conditions of PZ, Fine et al (2014) derived N-nitrosopiperazine (MNPZ) and nitrosodiethanolamine (NDELA), and nitroso-(2-hydroxyethyl) glycine (NHeGly) from their pilot plant samples. Kinetically, MNPZ has been found experimentally to decompose a lot faster in basic medium using NaOH than in PZ solution.…”

Degradation study of piperazine, its blends and structural analogs for CO2 capture: A review

“…N, thermal degradation of MNPZ was pseudo first order that followed Arrhenius temperature dependence with a rate constant of 10.2 × 10 −6 s −1 at 135 • C . Fine et al (2014) in another study, investigated decomposition of nitrosamines formed in PZ, MEA, MDEA, and AMP. Concentration of amines varied from 0.1 to 6 M with a CO 2 loading ranged from 0 to 0.4 mol CO 2 /mol alkalinity.…”

Na2CO3-modified CaO-based CO2 sorbents: the effects of structure and morphology on CO2 uptake

“…3 However, amine scrubbing is expensive and associated with the formation of hazardous by-products such as nitrosamines. 4,5 Therefore, alternative CCS technologies are currently explored, with calcium looping (CaL) being one of the most promising candidates. CaL is based on the reversible carbonation-calcination reaction pair CaO (s) + CO 2 (g) 2 CaCO 3 (s), DH 0 298K = AE178 kJ mol À1…”