Catalytic Paper Filters for Diesel Soot Abatement: Studies at Laboratory and Bench Scales

A scaling-up of the impregnation process for the preparation of catalytic ceramic papers was developed by which Co and Ce oxides were incorporated on to a ceramic paper structure. To this end, a spray generator and a vacuum system were coupled, allowing the preparation of catalytic ceramic papers in the form of circular sheets 16 cm in diameter and 0.3-cm thick. The catalytic papers were set inside a metallic case in order to conform a diesel particulate filter (DPF), which was tested at bench scale placing the filter at the exhaust pipe of a FIAT turbocharged diesel engine. The catalytic ceramic papers showed elevated capacity to trap soot particles, as opacity measurements indicated. Temperature-programmed oxidation (TPO) was employed to evaluate the performance of the catalytic systems both for the simultaneous combustion of soot and hydrocarbons collected after test bench runs. TPO results for soot combustion on catalytic papers prepared at laboratory scale (1.6 cm diameter) were compared with those obtained for the scaled-up system (16 cm diameter) incorporating soot from a suspension of the carbonaceous particles in n-hexane. Similar activities were obtained, indicating the success of the scaling-up procedure. Bench-scale tests showed that catalytic ceramic papers have mechanical and catalytic properties adequate to be used as DPF.