(563b) Life Cycle Of Catalytic Diesel Emission Control Systems

A diverse spectrum of highly capable diesel catalytic emission control systems has emerged in the recent years, in response to stringent environmental regulations in several leading world markets. By taking the brunt of the emission reduction, these highly effective systems allowed the engines to be designed and tuned for maximum fuel efficiency and minimum CO₂ emissions.

Unlike their gasoline emission control predecessors, diesel systems include multiple catalysts with distinct functions, along with a variety of sensors and actuators, thus representing veritable chemical plants. For example, the emission control system commercialized in Cummins-powered 2010 heavy-duty diesel vehicles includes four distinct catalytic devices, a diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (DPF), selective catalytic reduction (SCR) catalyst, and an ammonia slip selective oxidation catalyst (ASC). The system further includes eight sensors, and two fluid injectors, along with the respective controls and diagnostic algorithms. Another system, commercialized by Cummins in 2007 and 2010 Dodge Ram pickups, is based on an NOx adsorber catalyst and represents similar level of sophistication.  Underlying the system-level complexity is the intricacy of the individual catalytic elements, some of which include multiple distinct chemical functions and complex topology.

Predictably, lifecycles of such systems are shaped by the behaviors of the individual catalytic elements and their interactions. These often feature a variety of reversible processes, in response to deposition and removal of various poisons and masking agents, reversible chemical and morphological changes, along with irreversible degradation, often referred to as aging.

In this presentation, we will review several examples of interactions between catalysts in the context of the above diesel emission control systems, emphasizing how the recent advances in their practical application were underpinned by the developments in the broader field of heterogeneous catalysis and reaction engineering.