Layered clays as SCR deNOx catalysts

Titania-Clay Mineral Composites for Environmental Catalysis and Photocatalysis

The use of titania-based composite materials in the field of heterogeneous catalysis and photocatalysis has a long and rich history. Hybrid structures combining titania nanoparticles with clay minerals have been extensively investigated for nearly four decades. The attractiveness of clay minerals as components of functional materials stems primarily from their compositional versatility and the possibility of using silicate lamellae as prefabricated building blocks ready to be fitted into the desired nanoconstruction. This review focuses on the evolution over the years of synthetic strategies employed for the manufacturing of titania–clay mineral composites with particular attention to the role of the adopted preparative approach in shaping the physical and chemical characteristics of the materials and enabling, ultimately, tuning of their catalytic and/or photocatalytic performance.

The Enhanced Performance of N-Modified Activated Carbon Promoted with Ce in Selective Catalytic Reduction of NOx with NH3

The goal of the study was to modify activated carbon (AC) with nitrogen groups and ceria and to test the obtained materials in low temperature selective catalytic reduction of nitrogen oxides. For that purpose, the starting AC was oxidized with HNO3 of various concentrations, modified with urea and doped with 0.5 wt.% of Ce. It was observed that the increased concentration of acid influenced the catalytic activity, since textural and surface chemistry of activated carbon was changed. The most active sample was that modified with 14 M HNO3 and it reached 96% of NO conversion at 300 °C. Additionally, the addition of Ce improved the catalytic performance of modified AC, and NO was reduced according to oxidation–reduction mechanism, characteristic for supported metal oxides. Nevertheless, the samples promoted with Ce emitted significantly higher amount of CO2 comparing to the non-promoted ones.

The application of modified layered double hydroxides in selective catalytic reduction of nitrogen oxides by ammonia (NH3-SCR)

Selective catalytic reduction with ammonia (NH3-SCR) is very efficient DeNOx technique. According to some problems with the commercial catalyst, novel one should be prepared. Hydrotalcites are potential precursors of the new catalysts of NH3-SCR. In this paper, several attempts to apply these materials in NH3-SCR are presented.

A new V2O5–MoO3–TiO2–SO42−nanostructured aerogel catalyst for diesel DeNOxtechnology

A new V₂O₅–MoO₃–TiO₂–SO₄²⁻nanostructured aerogel catalyst exhibits superior SCR activity compared to the V₂O₅–WO₃/TiO₂commercial catalyst (EUROCAT) at high temperatures (375–500 °C).

Novel CeMo x O y -clay hybrid catalysts with layered structure for selective catalytic reduction of NO x by NH3

A facile method is to prepare novel CeMo_xO_y-clay hybrid catalysts with layered structures by using organic cation modified clay as support. During the preparation process, cerium cations and molybdate anions are easily adsorbed and impregnated into the interlamellar space of the organoclay, and after calcination they undergo transformation to highly dispersed CeMo_xO_y nanoparticles within the interlamellar space of the clay. As expected, the prepared CeMo_0.15O_x-OC-T catalysts with layered structures had high selective catalytic reduction (SCR) activity such as high NO_x conversion of >90% in the wide temperature range of 220–420 °C. Meanwhile, they also exhibit high stability and tolerance to water vapor (5 vol%) and SO₂ (200 ppm), demonstrating that these novel catalysts could serve as a good alternative for NH₃-SCR in practical application.

A facile method is to prepare novel CeMo_xO_y-clay hybrid catalysts with layered structures by using organic cation modified clay as support.

Nitrogen oxide removal over hydrotalcite-derived mixed metal oxides

Rigorous regulations of nitrogen oxide emissions require the development of technologies for their removal from exhaust gases.