Porosity Enhancement in Non-Cordierite Honeycomb Monoliths

Resumen

Structured materials, and in particular honeycomb monoliths, havelong offered enormous advantages respect to conventional packed-bedreactors in heterogeneous catalysis, especially for environmentalapplications. Their low pressure drop is the most well-known as theycontain multiple channels open to the flow of effluents. In addition, theyallow maximizing the contact between the catalytically active phases (insolid state) present on or inside the walls of these channels, and the flowing reactant molecules (gas or liquid). Moreover, being unitarystructures honeycomb monoliths can be easily handled or replaced uponsaturation or deactivation. However, methodology to investigate theirtextural properties is not so well developed as for powdered materials,and specifically the modification and/or enhancement of their porosity isnot properly or sufficiently reported, at least in a systematic mode, mostof the scarce references dealing with the widespread cordieritehoneycombs. In this chapter we review different ways to induce andmodulate porosity in non-cordierite honeycomb-type materials, basedboth in our own experience and that from other authors reviewingliterature to date. In particular, special attention is paid to honeycombmaterials which are manufactured by extrusion from natural cheap andabundant resources such as carbon and clays. In these cases, appropriatecombination of thermo-chemical treatments, controlled activation vianatural coal templating, and washcoating with more porous materials likepillared clays allow enhancing the textural properties of the supportmaterials. On the other hand, the most recent technologies as those basedon 3D printing offer and attractive alternative to classical corrugationfollowed by time and energy consuming thermo-chemical methods toincrease surface roughness.