Global Change Abstracts The Swiss Contribution - SCNAT

Global Change Abstracts – The Swiss Contribution | Mitigation and Adaptation Technologies
08.1-415
Flame-synthesized LaCoO3-supported Pd 2.
Catalytic behavior in the reduction of NO by
H-2 under lean conditions
Chiarello G L, Ferri D, Grunwaldt J D, Forni L, Baiker A
Italy, Switzerland
Engineering , Meteorology & Atmospheric Sciences
A 0.5 wt% Pd/LaCoO3, prepared by flame-spray pyrolysis
(FP), was tested as catalyst for the low-temperature
selective reduction of NO by H-2 in the
presence of excess O-2. In particular, the effect of
the precalcination and prereduction temperature
on catalytic activity was compared with that of a
similar Pd/LaCoO3 sample prepared by impregnation
with a Pd solution of FP-prepared LaCoO3.
The FP-made catalyst allowed full NO conversion
at 150 degrees C, with 78% selectivity to N-2, thus
outperforming the catalytic behavior of the corresponding
sample prepared by impregnation.
The higher activity of the FP-made catalyst has
been attributed to the formation of segregated Co
metal particles, not present in the impregnated
sample, formed during the precalcination at 800
degrees C, followed by reduction at 300 degrees C.
Two reaction mechanisms can be deduced from
the temperature-programmed experiments. The
first of these, occurring at lower temperatures, indicates
cooperation between the Pd and Co metal
particles, with formation of active nitrates on cobalt,
successively reduced by hydrogen spillover
from Pd. The second, occurring at higher temperature,
allows 50% conversion of NO, with >90% selectivity
to N-2, and involves N adatoms formed by
dissociative NO adsorption over Pd. Prereduction
at 600 degrees C led to a slight increase in catalytic
activity, due to the formation of a Pd-Co alloy,
which is more stable on reoxidization compared
with Pd alone. Moreover, the cooperative reaction
mechanism seems to be favored by the proximity
of Co and Pd in metal particles.
Journal of Catalysis, 2007, V252, N2, DEC 10,
pp 137-147.
08.1-416
Flame-synthesized LaCoO3-supported Pd 1.
Structure, thermal stability and reducibility
Chiarello G L, Grunwaldt J D, Ferri D, Krumeich R,
Oliva C, Forni L, Baiker A
Italy, Switzerland
Engineering , Meteorology & Atmospheric Sciences
Nanosized LaCoO3 (LCO) and 0.5 wt% Pd/LaCoO3
(PdLCO) were synthesized in a single step by
flame-spray pyrolysis (FP) and characterized by
N-2 adsorption-desorption at 77 K (BET), electron
microscopy (HRTEM, STEM-EDXS), in situ XRD, in
situ fluorescence XANES and EXAFS (around the
195
Pd K-edge), EPR, and H-2 TGA-TPR. The stability
of the perovskite structure under different treatments
and the location of Pd were addressed by
calcination at 600 and 800 degrees C and successive
reduction in 10% H-2/He to 300 and 600 degrees
C. The as-prepared Pd LCO exhibited a high
surface area (ca. 100 m(2)/g). Palladium appeared
to be finely dispersed on the FP material and was
partially incorporated in the perovskite lattice.
Calcination at 800 degrees C caused sintering and
substantial incorporation of Pd at the B-site of the
ABO(3) framework. EXAFS revealed that the Pd-O
distance was shorter than in PdO and further decreased
with increasing calcination temperature,
simultaneously with the appearance of a Pd-La
contribution. The reduction process involved
both Pd and Co. In the 100-300 degrees C range,
the reduction of Co3+ to Co2+ (from LaCoO3 to
La2CO 2O 5) and the segregation of Pd in the form
of metal particles occurred. The reduction of Co
was already reversible at 120 degrees C, and the
perovskite structure was restored after exposure
to oxygen. In contrast, Pd remained in the metallic
state. Therefore, the final structure of PdLCO
after mild reoxidation consisted of Pd and Co particles
supported on LaCoO3- In contrast, reduction
at 600 degrees C led to the formation of a Pd-Co
alloy. The composition of PdLCO reduced at different
temperatures is likely to strongly influence
the catalytic processes involved in combustion exhaust
after treatment.
Journal of Catalysis, 2007, V252, N2, DEC 10,
pp 127-136.
08.1-417
Increase of passenger car engine efficiency
with low engine-out emissions using hydrogen-natural
gas mixtures: A thermodynamic
analysis
Dimopoulos P, Rechsteiner C, Soltic P, Laemmle C,
Boulouchos K
Switzerland
Engineering , Energy & Fuels
In this study a state of the art passenger car natural
gas engine was optimised for hydrogen natural
gas mixtures and high exhaust gas recirculation
(EGR) rates in the part load domain. With optimal
combinations of spark timing (ST) and EGR
rate the achievements are significant efficiency
increase with substantially lower engine-out NOx
while total unburned hydrocarbons or CO-engineout
emissions are not affected. Comprehensive investigations
of the parameter space using design
of experiments (DoE) algorithms provided a complete
picture of the potential of such applications.
Combustion analysis on the other hand allowed to