Abstract View
Improving Filtration Performance of Ceramic Wall-flow Filters with Heat Resistant Membrane by a Two-step Coating Method
QISHENG OU, David Y. H. Pui, University of Minnesota
Abstract Number: 645
Working Group: Control and Mitigation Technology
Abstract
Gasoline direct injection (GDI) technology improves fuel efficiency but produces higher PM emissions. Gasoline particle filters (GPF) could be necessary for reducing exhaust particles to meet the emission standards. GPF has difficulty to grow and sustain “soot cake layer” and relies more on porous structures of its own substrate wall to ensure efficiency while keeping back pressure low, which is suboptimal and can be challenging at low mileage. Silica-based nano-scale membrane material is developed for improving filtration performance of ceramic wall-flow GPFs, which can sustain high exhaust temperature, be cost-effective, and user and environmentally friendly. The direct coating of silica membrane in a single-step process has a suboptimal tradeoff between efficiency and backpressure – achieving significant efficiency improvement at high backpressure penalty, which is attributed to the deep penetration of silica coating into substrate micropores. A two-step coating method is then successfully developed, starting from a 1st-step coating of removable porous material to occupy the micro-pore structure, followed by a 2nd-step coating of membrane material on top of the 1st coating. Subsequent regeneration removes 1st coating, leaving the 2nd-step membrane coating staying on top of the substrate. Membrane coated ceramic wafers by the two-step coating method show better efficiency-backpressure tradeoff and soot loading capability than the single-step method with the same coating materials. This two-step coating method is tested on a wall-flow core sample, showing significant efficiency enhancement with less than 30% of backpressure penalty. The developed two-step coating method can be potentially used on other filtration substrates, for improved filtration performance in high-temperature air and/or liquid filtration applications.