Implications of Hydrated Ash on Filtration Efficiency and Performance of Particulate Filters (DPF, GPF, and SCRF)—a Perspective

Particulate filters are used to meet current and future emission-control standards for particle mass and particle number requirements. However, with vehicle operation, non-combustible material (termed as “ash”) collects in the filter leading to an increase in ∆P, lower fuel economy, reduced soot storage space, and lower conversion rates for exhaust gases such as HC, NO, and NO 2 . In most cases, CaSO 4 originating from detergent formulations in the lubricant forms the major component of inorganic ash; CaSO 4 undergoes hydration cycles forming gypsum, along with semi-/hemi-hydrates through a series of transformations that are a function of temperature, time, and humidity. The exact nature of these transformations and the interaction of hydrated species with the filter substrate are poorly understood. The current work highlights the recent serendipitous discovery of hydrated ash structures and their deleterious effects on the filter and informs the automotive emission control community about the strategies for effective management of the filter.