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 bis­(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 Rh­(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 H₂, reaction of [Rh­(H) (CO)₂(BDP)] [BDP = bis­(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 η³-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 H₂ 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