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« ContiTech develops first polyamide strut mount for Cadillac chassis vibration control; 25% lighter | Main | UCLA–UC Berkeley paper outlines how CA can boost biofuel production to cut pollution and help the economy » Researchers at Fudan University, with colleagues at the University of Jinan and Chongqing University, have developed alkali- and sulfur-resistant tungsten-based catalysts for SCR NO emissions control. A paper on their work is published in the ACS journal Environmental Science & Technology. Alkali metals and sulfur oxides are two kinds of the well-known poisons of catalysts used in the selective catalytic reduction (SCR) of NO with NH from both stationary and mobile sources. At the 2015 AIChE Annual Meeting in Houston last month, Yasser Jangjou and William Epling presented a paper on sulfur poisoning of the SCR reaction, noting that sulfur is a common automotive catalyst poison even for the newer metal-exchanged small pore zeolite selective catalytic reduction (SCR) catalysts. In 2013, a team from NREL, Oak Ridge National Laboratory, Ford, MECA (Manufacturers of Emission Controls Association) and the University of Tennessee - Knoxville published an SAE paper investigating the impact of alkali (e.g., Na and K) and alkaline earth metals impurities in a light-duty application. They found that alkali metals are volatile at temperatures typically seen in diesel exhaust, allowing them to migrate into the catalyst washcoat leading to catalyst deactivation. However, they also found that there was sufficient unaltered catalyst volume to maintain mandated NO emission levels on the dynamometer after the simulated equivalent of 150,000 miles of exposure. I.e., by loading enough catalyst into the system, the deactivation problem can be managed. In the new work out of China, the researchers note that: Catalysts with acidic V O as an active component are proven to have an excellent resistance against SO poisoning than other “basic” metal oxides such as M O , CuO, CeO , and so on, although the vanadium-based catalysts are prone to poisoning by alkalis due largely to their strong acidity. … In this work, we develop a V O /HWO catalyst with strong resistance simultaneously to alkalis and SO poisoning. Two acidic oxides with strong resistance to SO poisoning, V O and HWO, are designed as an active component and a support, respectively. The HWO have rich size-suitable alkali-trapping sites with high specificity, and can professionally trap alkalis in the presence of high-concentration SO , even though alkalis are initially accumulated on the V O surfaces under normal SCR conditions. Testing showed that the V O /HWO catalyst exhibited strong resistance to alkali poisoning, and the catalysts with high K+ loading of 350 μmol g−1 did not decrease their high SCR activity even in the presence of the high-concentration SO , whereas conventional V O /WO −TiO catalysts almost completely lost SCR activity under the same conditions. The experimental results coupled with theoretical calculations demonstrated that the strong resistance of the V2O5/HWO catalysts to alkali and sulfur poisoning mainly originated from the specific alkali- trapping sites of the HWO. Alkalis accumulated on the catalytically active surface sites of the V O /HWO catalysts could spontaneously migrate into the HWO tunnels during the SCR reactions, and arrived at a separate state from the catalytically active sites, thus leading to simultaneous resistance to alkalis and SO poisoning. Therefore, the V O /HWO catalysts with a hexagonal structure of WO are promising candidates for controlling NO emissions from the stationary source and the mobile source against alkali and sulfur poisoning.


Saffaripour M.,National Research Council Canada | Chan T.W.,Environment Canada | Liu F.,National Research Council Canada | Thomson K.A.,National Research Council Canada | And 3 more authors.
Environmental Science and Technology | Year: 2015

The size and morphology of particulate matter emitted from a light-duty gasoline-direct-injection (GDI) vehicle, over the FTP-75 and US06 transient drive cycles, have been characterized by transmission-electron-microscope (TEM) image analysis. To investigate the impact of gasoline particulate filters on particulate-matter emission, the results for the stock-GDI vehicle, that is, the vehicle in its original configuration, have been compared to the results for the same vehicle equipped with a catalyzed gasoline particulate filter (GPF). The stock-GDI vehicle emits graphitized fractal-like aggregates over all driving conditions. The mean projected area-equivalent diameter of these aggregates is in the 78.4-88.4 nm range and the mean diameter of primary particles varies between 24.6 and 26.6 nm. Post-GPF particles emitted over the US06 cycle appear to have an amorphous structure, and a large number of nucleation-mode particles, depicted as low-contrast ultrafine droplets, are observed in TEM images. This indicates the emission of a substantial amount of semivolatile material during the US06 cycle, most likely generated by the incomplete combustion of accumulated soot in the GPF during regeneration. The size of primary particles and soot aggregates does not vary significantly by implementing the GPF over the FTP-75 cycle; however, particles emitted by the GPF-equipped vehicle over the US06 cycle are about 20% larger than those emitted by the stock-GDI vehicle. This may be attributed to condensation of large amounts of organic material on soot aggregates. High-contrast spots, most likely solid nonvolatile cores, are observed within many of the nucleation-mode particles emitted over the US06 cycle by the GPF-equipped vehicle. These cores are either generated inside the engine or depict incipient soot particles which are partially carbonized in the exhaust line. The effect of drive cycle and the GPF on the fractal parameters of particles, such as fractal dimension and fractal prefactor, is insignificant. © 2015 American Chemical Society. Source


Brezny R.,Manufacturers of Emission Controls Association | Kubsh J.,Manufacturers of Emission Controls Association
SAE Technical Papers | Year: 2013

Original equipment (OE) catalytic converters are designed to last the life of properly tuned and maintained vehicles. Many high mileage vehicles require a replacement converter because the original catalyst was damaged, destroyed, or removed, and the cost of a new OE converter on an older vehicle is difficult to justify. In the U.S., a federal aftermarket converter program has been in place since 1986 (California in 1988) and it has resulted in the replacement of over 50 million converters. Both Federal and California programs have required aftermarket converters to meet minimum performance and durability standards. Increasingly tighter emission standards and durability requirements for new light-duty vehicles have resulted in significant technology improvements in three-way automotive catalysts, however these advancements have not always made their way into aftermarket converters. California amended their aftermarket converter program in 2009, doubling the durability requirements and tightening the emission standards to match the original certification limits of the vehicles. To evaluate the difference in emissions performance between the state-of-the art California Air Resources Board (ARB) aftermarket converters and those offered in the federal market, a test program was designed to compare the two technologies across five LEV I certified vehicles. Federal and ARB converters were aged over a RAT-A cycle to represent 25,000 and 50,000 equivalent road miles of aging. Fresh and aged converters were tested over the FTP-75 test cycle. The ARB converters reduced criteria pollutants by an average of 77% NOx, 60% HC and 63% CO below today's Federal aftermarket converters. The data indicates that significant emission benefits could be achieved by revising federal aftermarket regulations to match those required by California. Copyright © 2013 SAE International. Source


Chan T.W.,Environment Canada | Meloche E.,Environment Canada | Kubsh J.,Manufacturers of Emission Controls Association | Brezny R.,Manufacturers of Emission Controls Association
Environmental Science and Technology | Year: 2014

Black carbon (BC) mass and solid particle number emissions were obtained from two pairs of gasoline direct injection (GDI) vehicles and port fuel injection (PFI) vehicles over the U.S. Federal Test Procedure 75 (FTP-75) and US06 Supplemental Federal Test Procedure (US06) drive cycles on gasoline and 10% by volume blended ethanol (E10). BC solid particles were emitted mostly during cold-start from all GDI and PFI vehicles. The reduction in ambient temperature had significant impacts on BC mass and solid particle number emissions, but larger impacts were observed on the PFI vehicles than the GDI vehicles. Over the FTP-75 phase 1 (cold-start) drive cycle, the BC mass emissions from the two GDI vehicles at 0 °F (-18 °C) varied from 57 to 143 mg/mi, which was higher than the emissions at 72 °F (22 °C; 12-29 mg/mi) by a factor of 5. For the two PFI vehicles, the BC mass emissions over the FTP-75 phase 1 drive cycle at 0 °F varied from 111 to 162 mg/mi, higher by a factor of 44-72 when compared to the BC emissions of 2-4 mg/mi at 72 °F. The use of a gasoline particulate filter (GPF) reduced BC emissions from the selected GDI vehicle by 73-88% at various ambient temperatures over the FTP-75 phase 1 drive cycle. The ambient temperature had less of an impact on particle emissions for a warmed-up engine. Over the US06 drive cycle, the GPF reduced BC mass emissions from the GDI vehicle by 59-80% at various temperatures. E10 had limited impact on BC emissions from the selected GDI and PFI vehicles during hot-starts. E10 was found to reduce BC emissions from the GDI vehicle by 15% at standard temperature and by 75% at 19 °F (-7 °C). © 2014 American Chemical Society. Source

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