Catalytic decomposition and reduction of N2O over micro-mesoporous materials containing Beta zeolite nanoparticles

摘要

Zeolitic materials with combined micro and mesoporous structure were synthesized using two different approaches. A first series of the samples was obtained by impregnation method. Suspension of Beta nanoparticles was impregnated on SBA-15 mesoporous silica. In the second synthesis route, called non-templating method, Beta nanoparticles were aggregated under specified conditions with the formation of micro-mesoporous material (without the use of the mesopore directing agent). Micropores were present in the zeolite nanoparticles, while mesopores were located in the interparticle space. The combined micro and mesoporous structure of the obtained materials, exhibiting the properties of Beta zeolite, was confirmed by nitrogen sorption measurements, XRD, TGA and DRIFT techniques. The hierarchical porous structure of the samples resulted in an improved accessibility of ion-exchange positions in comparison to conventional Beta zeolite and allowed the introduction of iron, nearly exclusively in the form of monomeric Fe~(3+) cations and oligomeric Fe_xO_y, species. The iron modified micro-mesoporous samples as well as SBA-15 and Beta zeolite (as reference samples), were tested as catalysts of N2O decomposition. The most promising micro-mesoporous sample (Fe-Beta/meso) was tested as catalyst in the reactions of N2O decomposition and N2O reduction with CO at different composition of gas mixture (in the presence of O2, H2O and NO). Catalytic activity of iron-exchanged, micro-mesoporous Beta and conventional Beta zeolites in the reaction of N2O conversion was very similar.