Catalytic paper made from ceramic fibres and natural ulexite. Application to diesel particulate removal

Abstract

Ceramic paper discs were made by employing a dual papermaking technique and by partially substituting cellulosic fibres by SiO2-Al2O3 ceramic ones. Ulexite (NaCaB5O6(OH)6·5(H2O)), extracted from the natural mineral, was added as a binder to give ceramic paper the necessary strength for its manipulation and catalytic use.Either La,Co or Ba,Co was incorporated in order to give ceramic paper the capability of trapping NOx and oxidizing soot particles. Structured catalysts were characterised by SEM, FTIR and XRD, and the mechanical properties were also determined. Lanthanum was deposited on ceramic fibres as La2O2CO3 aggregates and barium as BaCO3 filaments, being cobalt deposited as Co3O4 flakes. Mechanical properties indicated that the ceramic paper obtained from natural ulexite proved to be stronger, though less flexible than those prepared using colloidal suspensions as a binder.Diesel soot oxidation activity was determined by TPO either adding or not 0.1% NO into the feeding stream. The thus prepared systems resulted in being active towards soot oxidation, being the value of maximum combustion rate 420°C, which is within the temperature range of diesel exhaust gases.