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Low cost and S(sulphur)-tolerant DOCs (Diesel Oxidation Catalysts) are being demanded in emerging countries such as China and India, where Euro 4 and 5 type emission standards are going to be implemented or are being implemented. However, fuel S content is different in the metros vis-à-vis non metros in many emerging countries. In such a scenario, DOCs need to maintain catalytic performance with high S fuel as well as standard low S fuel. This paper describes the development results of S tolerant Pt-Pd based DOCs. A new washcoat technology (WT D) has been developed for EU 4 passive Pt-Pd DOC applications, in which PGM cost was thrifted by replacing part of Pt by Pd. Vehicle test results after thermal ageing and S poisoning demonstrated that the Pt-Pd DOC (Pt:Pd=4:1) prepared with WT D gave similar tailpipe CO (Carbon monoxide) and HC (Hydrocarbon) emission conversions as a commercially available EU 4 passive Pt-only DOC when 50ppm S diesel fuel was used.

The Indian government has announced that India will skip BS V legislation and move to BS VI from 2020. In order to meet this NOx emission standard, most vehicles will need to adopt either NOx Storage Catalyst (NSC) or Selective Catalytic Reduction (SCR). It is shown that these two devices have different NOx reduction temperature windows and different sulfur tolerance. In the LDD application, it is highly important to deal with NOx in the low temperature region directly after a cold start. NSC works in this region with better performance than SCR, but its sulfur tolerance is weaker than SCR. To improve the weakness in low temperature NOx control on SCR, SCRF® which is SCR coated Diesel Particulate Filter (DPF) was developed and it demonstrated an advantage in light-off performance, due to the advantage in temperature conditions, by minimizing heat loss upstream of the SCR device.