Two-Stage Plasma-Catalysis for Diesel NOx Emission Control

Publisher： Science and Technology Network Inc.

ISSN： 1203-8407

Source： Journal of Advanced Oxidation Technologies, Vol.6, Iss.2, 2003-07, pp. : 158-165

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Abstract

Plasma discharges in diesel simulated exhaust gas oxidize NO primarily to NO₂, while forming aldehydes and other partial-oxidation products from hydrocarbons. Appropriate catalysts can react NOx and aldehydes in the presence of oxygen, producing nitrogen. Suitable catalysts include sodium and barium forms of zeolite-Y, and for higher temperatures, high surface area γ-alumina. Combinations of catalysts can be more effective that the individual ones, especially considering temperature transients which occur during vehicle operation. An oxidation catalyst is required following the NOx catalysts, to remove remaining hydrocarbon, aldehydes, and HCN species. A cascaded system consisting of multiple plasma-catalyst stages, can achieve higher NOx conversion and/or more efficient electrical power utilization than a single plasma-catalyst system. Best effort laboratory evaluations on simulated exhaust have achieved 90% NOx conversion. Vehicle tests have yet to show such promising results.