μ-CT Investigation into the Impact of a Fuel-Borne Catalyst Additive on the Filtration Efficiency and Backpressure of Gasoline Particulate Filters

An investigation into the pre-ashing of new gasoline particulate filters (GPFs) has demonstrated that the filtration efficiency of such filters can be improved by up to 30% (absolute efficiency improvement) when preconditioned using ash derived from a fuel-borne catalyst (FBC) additive. The additive is typically used in diesel applications to enable diesel particulate filter (DPF) regeneration and can be added directly into the fuel tank of the vehicle. This novel result was compared with ash derived from lube oil componentry, which has previously been shown to improve filtration efficiency in GPFs. The lube oil-derived ash utilized in this work improved the filtration efficiency of the GPF by approximately 30%, comparable to the ash derived from the FBC additive. The undesirable impact of the ash deposit on backpressure increases was also investigated, and it was established that the use of the FBC additive resulted in a lower backpressure increase versus the equivalent ash loading from lube oil components. Following the real-world vehicle testing and GPF evaluation, the used, intact filters were further analyzed, using micro-focus computed tomography (μ-CT) to assess the ash distribution within the filters. It was established that the FBC-derived ash was predominantly deposited near the outlet plug region of the filter, whereas the lube oil-derived ash was also distributed within the channel walls, which resulted in a higher GPF backpressure. The μ-CT results were therefore key to establishing the differences between these two ash-providing sources and enabled a better understanding of the effect of filter microstructure on macroscopic performance, i.e., GPF efficiency and backpressure results.