Review of diesel emissions and control

Abstract

This summary covers key and representative developments in diesel emissions regulations, engine developments, and nitrogen oxide (NO x), particulate matter (PM), and hydrocarbon (HC) remediation. In California discussions are taking place on another round of criteria pollutant tightening on light duty. Carbon dioxide (CO2) regulations are being discussed in the developed markets. The US mandates on fuel economy and the proposed standards in Europe and California will result in a paradigm shift, wherein technologies previously rejected based on customer value will now be re-evaluated. Heavy-duty regulatory developments are now focused on Europe, where Euro VI regulations have been proposed for about 2013. The regulations are intended to be technology harmonizing with the US and Japanese regulations. Engines are continuing to make very impressive progress, with clean combustion strategies in active development mainly for US light-duty application. Heavy-duty research engines are more focused on traditional approaches, and will provide numerous engine/aftertreatment options for hitting the tight US 2010 regulations. NO x control is focusing on selective catalytic reduction (SCR) for diverse applications. Zeolite catalysts will be the mainstay for Japan, US, and Euro VI applications. The focus is catalyst improvements and system optimization. Lean NO x traps (LNTs) are effective up to about 70–80 per cent deNO x efficiency, and are being used for light-duty applications with significant improvements coming on precious metal utilization. Diesel particulate filter (DPF) technology is in a state of optimization and cost reduction. Very sophisticated management strategies are being utilized, which open up options for new filter materials and alternative system architectures. New catalyst formulations that oxidize soot at the catalyst—soot interface are emerging and are enhancing regeneration in the first commercial applications. Diesel oxidation catalysts (DOCs) are lighting-off and generating more NO2 for DPF regeneration at lower temperatures. For a more comprehensive review of these technologies the reader is directed to Johnson, T. V., Diesel emissions in review, SAE 2008-01-0121.

Environmentally-benign catalysts for the selective catalytic reduction of NOxfrom diesel engines: structure–activity relationship and reaction mechanism aspects

“…162,165,166,173,179 Two kinds of surface enolic species, adsorbed only on Al sites (CH 2 QCH-CHQCH-O-Al 6 O 5 (OH) 8 ) and bound on or close to Ag (CH 2 QCH-O-Ag, CH 2 QCH-CHQCH-O-Al-Ag) were suggested by DFT calculations over Ag/Al 2 O 3 and Al 2 O 3 , with the simulation molecular structure model and corresponding FTIR spectrum shown in Fig. 3D-F, respectively.…”

“…5,6 Vanadium-based NH 3 -SCR catalysts have also been successfully used for the deNO x process from diesel engines, since 2005. 7,8 However, disadvantages remain for the vanadium-based catalysts, including the toxicity of V 2 O 5 , the narrow operation temperature window, the easy sublimation of V 2 O 5 and phase transformation of the TiO 2 support from anatase to rutile at high temperatures, which greatly restrict their further application, especially when stricter regulations are established for both PM and NO x for diesel engines, and the SCR converter should be installed downstream of the diesel particulate filter (DPF), with timed thermal shock (B800 1C) in the regeneration processes of the DPF system. Therefore, many researchers are trying to develop vanadium-free NH 3 -SCR catalysts with high deNO x efficiency, high N 2 selectivity, excellent hydrothermal stability and insensitivity to co-existing poisoning components in the SCR atmosphere such as H 2 O, SO 2 , HC or alkali metals etc.…”

Effect of Butanol Blends on Nano Particle Emissions from a Stationary Conventional Diesel Engine

“…NO x and PM have adverse effect on human health (Afroz et al, 2003) and the environment. In order to meet the stringent emission legislation limits, diesel particulate filters, lean NO x trap, selective catalytic reduction (advanced after-treatment devices) are typically used to reduce the engine emissions (Johnson, 2010). However, after-treatment devices have penalty effect on the fuel efficiency of the engine (Johnson, 2008;Johnson, 2009).…”

Selective catalytic reduction of NOx by NH3 for heavy-duty diesel vehicles

“…The selective catalytic reduction of NOx with NH3 (NH3-SCR) is one of the most promising technologies for NOx abatement in diesel exhaust [4]. To meet more stringent NOx emission control regulations, many automobile and engine manufacturers in developed countries have developed the industrial application of NH3-SCR technology and used it in commercial vehicles.…”

“…These catalysts have also been introduced for use in diesel vehicles [4][5][6]. However, the toxicity of vanadium species together with the narrow operation temperature window has limited the practical application of vanadium-based catalysts.…”