This data collection contains X-ray tomographic scans capturing alumina washcoating of a catalytic particulate filter. Data were acquired and processed at the TOMCAT beamline X02DA of the Swiss Light Source. The collection contains time series for four alumina washcoats with different particle sizes: 6 um, 12 um, 20 um and 6+20 um. The 4D scans were obtained with 0.8 um pixel size and 5 seconds temporal resolution. Please see the related publication for the used imaging sequence. In addition, higher quality scans of coated and dried filters are included in the collection.