Alkanolamines such
as monoethanolamine (MEA), diethanolamine (DEA),
and triethanolamine (TEA) are extensively used for CO2 capture
and consumer products. Despite their prevalence in industrial applications,
the fate of alkanolamines in the atmosphere remains relatively unknown.
One likely reaction pathway for these chemicals in the atmosphere
is new particle formation with sulfuric acid. Here, we present the
first experimental results showing the formation of sulfuric acid
dimers enhanced by MEA, DEA, and TEA from the measurement of molecular
clusters. This study examines the nucleation reactions of MEA, DEA,
and TEA with sulfuric acid in a clean, laminar flow reactor. The chemical
compositions and concentrations of the freshly nucleated clusters
were analyzed using a custom-built atmospheric pressure chemical ionization
long time-of-flight mass spectrometer known as the Pittsburgh Cluster
CIMS. Quantum chemical calculations and kinetic modeling of sulfuric
acid-MEA/DEA/TEA clusters were also performed to determine relative
cluster stabilities between these sulfuric acid–base systems.
Experimental results indicate that MEA, DEA, and TEA at the part per
trillion by volume (pptv) concentrations can enhance sulfuric acid
dimer formation rates but to a lesser extent than dimethylamine (DMA).
Thus, MEA, DEA, and TEA will potentially play an important role in
new particle formation in industrial cities where these alkanolamines
are emitted.