4 research outputs found
Bioethanol Blending Reduces Nanoparticle, PAH, and Alkyl- and Nitro-PAH Emissions and the Genotoxic Potential of Exhaust from a Gasoline Direct Injection Flex-Fuel Vehicle
Bioethanol as an alternative fuel
is widely used as a substitute
for gasoline and also in gasoline direct injection (GDI) vehicles,
which are quickly replacing traditional port-fuel injection (PFI)
vehicles. Better fuel efficiency and increased engine power are reported
advantages of GDI vehicles. However, increased emissions of soot-like
nanoparticles are also associated with GDI technology with yet unknown
health impacts. In this study, we compare emissions of a flex-fuel
Euro-5 GDI vehicle operated with gasoline (E0) and two ethanol/gasoline
blends (E10 and E85) under transient and steady driving conditions
and report effects on particle, polycyclic aromatic hydrocarbon (PAH),
and alkyl- and nitro-PAH emissions and assess their genotoxic potential.
Particle number emissions when operating the vehicle in the hWLTC
(hot started worldwide harmonized light-duty vehicle test cycle) with
E10 and E85 were lowered by 97 and 96% compared with that of E0. CO
emissions dropped by 81 and 87%, while CO<sub>2</sub> emissions were
reduced by 13 and 17%. Emissions of selected PAHs were lowered by
67–96% with E10 and by 82–96% with E85, and the genotoxic
potentials dropped by 72 and 83%, respectively. Ethanol blending appears
to reduce genotoxic emissions on this specific flex-fuel GDI vehicle;
however, other GDI vehicle types should be analyzed
PCDD/F Formation in an Iron/Potassium-Catalyzed Diesel Particle Filter
Catalytic
diesel particle filters (DPFs) have evolved to a powerful
environmental technology. Several metal-based, fuel soluble catalysts,
so-called fuel-borne catalysts (FBCs), were developed to catalyze
soot combustion and support filter regeneration. Mainly iron- and
cerium-based FBCs have been commercialized for passenger cars and
heavy-duty vehicle applications. We investigated a new iron/potassium-based
FBC used in combination with an uncoated silicon carbide filter and
report effects on emissions of polychlorinated dibenzodioxins/furans
(PCDD/Fs). The PCDD/F formation potential was assessed under best
and worst case conditions, as required for filter approval under the
VERT protocol. TEQ-weighted PCDD/F emissions remained low when using
the Fe/K catalyst (37/7.5 μg/g) with the filter and commercial,
low-sulfur fuel. The addition of chlorine (10 μg/g) immediately
led to an intense PCDD/F formation in the Fe/K-DPF. TEQ-based emissions
increased 51-fold from engine-out levels of 95 to 4800 pg I-TEQ/L
after the DPF. Emissions of 2,3,7,8-TCDD, the most toxic congener
(TEF = 1.0), increased 320-fold, those of 2,3,7,8-TCDF (TEF = 0.1)
even 540-fold. Remarkable pattern changes were noticed, indicating
a preferential formation of tetrachlorinated dibenzofurans. It has
been shown that potassium acts as a structural promoter inducing the
formation of magnetite (Fe<sub>3</sub>O<sub>4</sub>) rather than hematite
(Fe<sub>2</sub>O<sub>3</sub>). This may alter the catalytic properties
of iron. But the chemical nature of this new catalyst is yet unknown,
and we are far from an established mechanism for this new pathway
to PCDD/Fs. In conclusion, the iron/potassium-catalyzed DPF has a
high PCDD/F formation potential, similar to the ones of copper-catalyzed
filters, the latter are prohibited by Swiss legislation
Effects of a Combined Diesel Particle Filter-DeNOx System (DPN) on Reactive Nitrogen Compounds Emissions: A Parameter Study
The impact of a combined diesel particle filter-deNO<sub><i>x</i></sub> system (DPN) on emissions of reactive nitrogen
compounds
(RNCs) was studied varying the urea feed factor (α), temperature,
and residence time, which are key parameters of the deNO<sub><i>x</i></sub> process. The DPN consisted of a platinum-coated
cordierite filter and a vanadia-based deNO<sub><i>x</i></sub> catalyst supporting selective catalytic reduction (SCR) chemistry.
Ammonia (NH<sub>3</sub>) is produced in situ from thermolysis of urea
and hydrolysis of isocyanic acid (HNCO). HNCO and NH<sub>3</sub> are
both toxic and highly reactive intermediates. The deNO<sub><i>x</i></sub> system was only part-time active in the ISO8178/4
C1cycle. Urea injection was stopped and restarted twice. Mean NO and
NO<sub>2</sub> conversion efficiencies were 80%, 95%, 97% and 43%,
87%, 99%, respectively, for α = 0.8, 1.0, and 1.2. HNCO emissions
increased from 0.028 g/h engine-out to 0.18, 0.25, and 0.26 g/h at
α = 0.8, 1.0, and 1.2, whereas NH<sub>3</sub> emissions increased
from <0.045 to 0.12, 1.82, and 12.8 g/h with maxima at highest
temperatures and shortest residence times. Most HNCO is released at
intermediate residence times (0.2–0.3 s) and temperatures (300–400
°C). Total RNC efficiencies are highest at α = 1.0, when
comparable amounts of reduced and oxidized compounds are released.
The DPN represents the most advanced system studied so far under the
VERT protocol achieving high conversion efficiencies for particles,
NO, NO<sub>2</sub>, CO, and hydrocarbons. However, we observed a trade-off
between deNO<sub><i>x</i></sub> efficiency and secondary
emissions. Therefore, it is important to adopt such DPN technology
to specific application conditions to take advantage of reduced NO<sub><i>x</i></sub> and particle emissions while avoiding NH<sub>3</sub> and HNCO slip
Biofuel-Promoted Polychlorinated Dibenzodioxin/furan Formation in an Iron-Catalyzed Diesel Particle Filter
Iron-catalyzed diesel particle filters
(DPFs) are widely used for
particle abatement. Active catalyst particles, so-called fuel-borne
catalysts (FBCs), are formed <i>in situ</i>, in the engine,
when combusting precursors, which were premixed with the fuel. The
obtained iron oxide particles catalyze soot oxidation in filters.
Iron-catalyzed DPFs are considered as safe with respect to their potential
to form polychlorinated dibenzodioxins/furans (PCDD/Fs). We reported
that a bimetallic potassium/iron FBC supported an intense PCDD/F formation
in a DPF. Here, we discuss the impact of fatty acid methyl ester (FAME)
biofuel on PCDD/F emissions. The iron-catalyzed DPF indeed supported
a PCDD/F formation with biofuel but remained inactive with petroleum-derived
diesel fuel. PCDD/F emissions (I-TEQ) increased 23-fold when comparing
biofuel and diesel data. Emissions of 2,3,7,8-TCDD, the most toxic
congener [toxicity equivalence factor (TEF) = 1.0], increased 90-fold,
and those of 2,3,7,8-TCDF (TEF = 0.1) increased 170-fold. Congener
patterns also changed, indicating a preferential formation of tetra-
and penta-chlorodibenzofurans. Thus, an inactive iron-catalyzed DPF
becomes active, supporting a PCDD/F formation, when operated with
biofuel containing impurities of potassium. Alkali metals are inherent
constituents of biofuels. According to the current European Union
(EU) legislation, levels of 5 μg/g are accepted. We conclude
that risks for a secondary PCDD/F formation in iron-catalyzed DPFs
increase when combusting potassium-containing biofuels