NOx Trap Catalysts and Technologies: Fundamentals and Industrial Applications
Chapter 16: LNT Catalysis at Ford Motor Company – A Case History
Published:13 Jun 2018
C. K. Lambert, J. R. Theis, and G. Cavataio, in NOx Trap Catalysts and Technologies: Fundamentals and Industrial Applications, ed. L. Lietti and L. Castoldi, The Royal Society of Chemistry, 2018, ch. 16, pp. 467-489.
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Ford studied lean NOx traps (LNTs) extensively for over 20 years and used LNTs successfully on both lean burn gasoline and diesel vehicles. Three-way catalysts (TWCs) are remarkable devices that control vehicle emissions of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) with 99.9% effectiveness; however, TWCs do not provide suitable NOx control under lean exhaust conditions. The design and management of LNTs, especially during sulfur removal, is of upmost importance for overall functionality and durability. The maximum thermal limit of LNTs was increased while the deSOx temperature was decreased, enabling their implementation with improved controls. LNTs can generate ammonia, so they are often combined in diesel exhaust systems with selective catalytic reduction (SCR) catalysts or SCR coated diesel particulate filters (SDPFs), providing NOx control during more types of driving conditions than LNT alone. The use of LNTs on gasoline is far less widespread. Despite all the efforts on lean NOx control for gasoline vehicles, the fuel benefits are not enough to justify the extra cost of additional catalysts and associated sensors. This case study summarizes the operational, functional, and compositional differences between LNTs applied to gasoline and diesel vehicles, and what drives the decision for an automaker to choose a particular system.