1 research outputs found
Transformation of Cerium Oxide Nanoparticles from a Diesel Fuel Additive during Combustion in a Diesel Engine
Nanoscale cerium
oxide is used as a diesel fuel additive to reduce
particulate matter emissions and increase fuel economy, but its fate
in the environment has not been established. Cerium oxide released
as a result of the combustion of diesel fuel containing the additive
Envirox, which utilizes suspended nanoscale cerium oxide to reduce
particulate matter emissions and increase fuel economy, was captured
from the exhaust stream of a diesel engine and was characterized using
a combination of bulk analytical techniques and high resolution transmission
electron microscopy. The combustion process induced significant changes
in the size and morphology of the particles; ∼15 nm aggregates
consisting of 5−7 nm faceted crystals in the fuel additive
became 50–300 nm, near-spherical, single crystals in the exhaust.
Electron diffraction identified the original cerium oxide particles
as ceriumÂ(IV) oxide (CeO<sub>2</sub>, standard FCC structure) with
no detectable quantities of CeÂ(III), whereas in the exhaust the ceria
particles had additional electron diffraction reflections indicative
of a CeO<sub>2</sub> superstructure containing ordered oxygen vacancies.
The surfactant coating present on the cerium oxide particles in the
additive was lost during combustion, but in roughly 30% of the observed
particles in the exhaust, a new surface coating formed, approximately
2–5 nm thick. The results of this study suggest that pristine,
laboratory-produced, nanoscale cerium oxide is not a good substitute
for the cerium oxide released from fuel-borne catalyst applications
and that future toxicity experiments and modeling will require the
use/consideration of more realistic materials