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Catalyzed Gasoline Particulate Filters Reduce Secondary Organic Aerosol Production from Gasoline Direct Injection Vehicles
The
effects of photochemical aging on exhaust emissions from two
light-duty vehicles with gasoline direct injection (GDI) engines equipped
with and without catalyzed gasoline particle filters (GPFs) were investigated
using a mobile environmental chamber. Both vehicles with and without
the GPFs were exercised over the LA92 drive cycle using a chassis
dynamometer. Diluted exhaust emissions from the entire LA92 cycle
were introduced to the mobile chamber and subsequently photochemically
reacted. It was found that the addition of catalyzed GPFs will significantly
reduce tailpipe particulate emissions and also provide benefits in
gaseous emissions, including nonmethane hydrocarbons (NMHC). Tailpipe
emissions composition showed important changes with the use of GPFs
by practically eliminating black carbon and increasing the fractional
contribution of organic mass. Production of secondary organic aerosol
(SOA) was reduced with GPF addition, but was also dependent on engine
design which determined the amount of SOA precursors at the tailpipe.
Our findings indicate that SOA production from GDI vehicles will be
reduced with the application of catalyzed GPFs through the mitigation
of reactive hydrocarbon precursors
Impact of Fuel Metal Impurities on the Durability of a Light-Duty Diesel Aftertreatment System
Alkali and alkaline earth metal impurities found in diesel fuels are potential poisons for diesel exhaust catalysts. A set of diesel engine production exhaust systems was aged to 150,000 miles. These exhaust systems included a diesel oxidation catalyst, selective catalytic reduction (SCR) catalyst, and diesel particulate filter (DPF). Four separate exhaust systems were aged, each with a different fuel: ultralow sulfur diesel containing no measureable metals, B20 (a common biodiesel blend) containing sodium, B20 containing potassium, and B20 containing calcium, which were selected to simulate the maximum allowable levels in B100 according to ASTM D6751. Analysis included Federal Test Procedure emissions testing, bench-flow reactor testing of catalyst cores, electron probe microanalysis (EPMA), and measurement of thermo-mechanical properties of the DPFs. EPMA imaging found that the sodium and potassium penetrated into the washcoat, while calcium remained on the surface. Bench-flow reactor experiments were used to measure the standard nitrogen oxide (NOx) conversion, ammonia storage, and ammonia oxidation for each of the aged SCR catalysts. Vehicle emissions tests were conducted with each of the aged catalyst systems using a chassis dynamometer. The vehicle successfully passed the 0.2 gram/mile NOx emission standard with each of the four aged exhaust systems
Unexpected CO Dependencies, Catalyst Speciation, and Single Turnover Hydrogenolysis Studies of Hydroformylation via High Pressure NMR Spectroscopy
Rhodium
bisÂ(diazaphospholane) (BDP) catalyzed hydroformylation
of styrene is sensitive to CO concentration, and drastically different
kinetic regimes are affected by modest changes in gas pressure. The
Wisconsin High Pressure NMR Reactor (WiHP-NMRR) has enabled the observation
of changes in catalyst speciation in these different regimes. The
apparent discrepancy between catalyst speciation and product distribution
led us to report the first direct, noncatalytic quantitative observation
of hydrogenolysis of acyl dicarbonyls. Analysis and modeling of these
experiments show that not all catalyst is shunted through the off-cycle
intermediates and this contributes to the drastic mismatch in selectivities.
The data herein highlight the complex kinetics of RhÂ(BDP) catalyzed
hydroformylation. In this case, the complexity arises from competing
kinetic and thermodynamic preferences involving formation and isomerization
of the acyl mono- and dicarbonyl intermediates and their hydrogenolysis
to give aldehydes
Interception and Characterization of Catalyst Species in Rhodium Bis(diazaphospholane)-Catalyzed Hydroformylation of Octene, Vinyl Acetate, Allyl Cyanide, and 1‑Phenyl-1,3-butadiene
In
the absence of H<sub>2</sub>, reaction of [RhÂ(H) (CO)<sub>2</sub>(BDP)]
[BDP = bisÂ(diazaphospholane)] with hydroformylation substrates
vinyl acetate, allyl cyanide, 1-octene, and <i>trans</i>-1-phenyl-1,3-butadiene at low temperatures and pressures with passive
mixing enables detailed NMR spectroscopic characterization of rhodium
acyl and, in some cases, alkyl complexes of these substrates. For <i>trans</i>-1-phenyl-1,3-butadiene, the stable alkyl complex is
an η<sup>3</sup>-allyl complex. Five-coordinate acyl dicarbonyl
complexes appear to be thermodynamically preferred over the four-coordinate
acyl monocarbonyls at low temperatures and one atmosphere of CO. Under
noncatalytic (i.e., no H<sub>2</sub> present) reaction conditions,
NMR spectroscopy reveals the kinetic and thermodynamic selectivity
of linear and branched acyl dicarbonyl formation. Over the range of
substrates investigated, the kinetic regioselectivity observed at
low temperatures under noncatalytic conditions roughly predicts the
regioselectivity observed for catalytic transformations at higher
temperatures and pressures. Thus, kinetic distributions of off-cycle
acyl dicarbonyls constitute reasonable models for catalytic selectivity.
The Wisconsin high-pressure NMR reactor (WiHP-NMRR) enables single-turnover
experiments with active mixing; such experiments constitute a powerful
strategy for elucidating the inherent selectivity of acyl formation
and acyl hydrogenolysis in hydroformylation reactions
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