Porous clay heterostructures (PCHs) intercalated with silica-titania pillars and modified with transition metals as catalysts for the DeNO_x process

摘要

Porous clay heterostructures (PCHs) intercalated with silica as well as silica-titania pillars were obtained from natural montmorillonite. The PCH samples were modified with copper or iron by an ion-exchange method. Detailed characterization of ttie obtained materials included: chemical (EPMA), structural (XRD) and textural (BET) analysis, determination of coordination and aggregation of transition metal species (UV-vis-DRS, EPR) as well as analysis of surface acidity (FT-IR, NH3-TPD). Titanium incorporated into the silica pillars was present mainly in the form of separated cations. Small contribution of polymeric titanium oxides was detected only for the samples with the higher Ti loading. Titanium incorporated into the silica pillars significantly increased the surface acidity of the PCH materials. Transition metals (Cu, Fe) deposited on the surface of PCHs were present mainly in the form of isolated cations and oligomeric metal oxide species. Ti-containing PCHs modified with transition metals was found to be active and selective catalysts of the DeNO_x process. The Cu- and Fe-modified catalysts effectively operated in a broad temperature range of 350-550 °C and 300-500 °C, respectively. The PCH based catalysts were only slightly deactivated by water vapour and SO2.