A three-component Cu/BaO/La 2 O 3 catalyst has been developed as a highly efficient catalyst for the simultaneous removal of carbon soot and NO gas from diesel emissions. The influence of transition metals (Cu, Pd, Ni, Co, and Pt) deposited on BaO/La 2 O 3 supports and cosupports (BaO, SrO, CaO, and CeO 2 ) combined with La 2 O 3 were investigated. The Cu/BaO/La 2 O 3 catalyst completely combusted 50 wt % carbon soot under an O 2 atmosphere, with a T50% temperature of 375 °C. This catalyst also exhibited the highest activity among the investigated catalyst systems for the simultaneous removal of carbon soot and NO gas, even at low temperatures. The absence of carbon soot substantially decreased the NO conversion rate that suggested carbon soot acts as a solid reductant for the NO reduction. The high activity of the Cu/BaO/La 2 O 3 system can be attributed to the high oxygen storage capacity (OSC) of the BaO phase on La 2 O 3 and to the redox properties of the Cu species that are attributable to strong Cu− BaO interactions. The Cu/BaO/La 2 O 3 also exhibits high durability and good recyclability without any appreciable loss of catalytic activity. We propose that the present catalytic reaction consists of two reaction pathways: (i) direct soot oxidation by surface oxygen species and (ii) NO x -assisted soot oxidation. The use of significantly cheaper Cu rather than noble metals makes the Cu/BaO/La 2 O 3 catalyst a strong candidate to satisfy today's industrial requirements because of its lack of a precious metal.
Temporal evolution of ion fragment production from gaseous methylsilane in contact with a hot tungsten wire was measured with a use of a low-energy mass analyzed ion beam system. The mechanisms of molecular fragmentation in the system are similar to those for typical catalytic chemical vapor deposition processes. The fragmentation rates vary during the process due to surface modification of the tungsten wire. The extent of surface modification depends on the tungsten temperature. When the tungsten temperature was set to 1940°C, ion fragments were produced initially but the production terminated about 1h after the start of the experiment. The termination of ion production seems to be caused by the formation of a thick 3C-SiC layer on the tungsten surface, which was identified by x-ray diffraction measurement. When the tungsten temperature was set to 2220°C, ion fragment production continued at least for 8h. In this case the layer of deposited compounds, which mainly consist of WC, W2C, C, and 4H-SiC, was relatively thin.
Three chemical forms of atmospheric tritium, i.e., tritiated water vapor (HTO), hydrogen gas (HT), and hydrocarbons (CH3T), were measured at Kumamoto, Japan during the period between 2003 and 2005. The average concentrations were in the order of HT, CH3T, and HTO. The yearly average HT concentrations were not so different in each year, while that of CH3T showed a large variation. The concentrations of all chemical species have decreased compared to those measured during the period between 1984 and 1995 at Fukuoka, about 100 km north of the present sampling location, suggesting a decrease in emissions of HT and CH3T from their sources for these 8-10 years. The decrease in HTO concentration would be attributed to the decrease of the bomb-produced tritium and to a regional characteristic of the sampling locations; Kumamoto showed lower tritium concentrations in rain than Fukuoka.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.