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Removal of nitric oxides (NOx) from stationary and transportation sources has been desired for environmental benefits. Selective catalytic reduction (SCR) of NOx by NH3 is attractive for its cost effectiveness and high efficiency but still technically challenging in consideration of operable temperatures. In this research, MnOx-CeOx hybrid nanoparticles supported on graphene aerogel (MnOx-CeOx/GA) are fabricated as the monolithic catalysts for potential applications to low-temperature SCR. The impacts of the particle size along with the amount and valency of catalytic elements in the nanocomposite on the catalytic activities are studied with the help of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The catalyst crystallites are a few tens of nanometers and uniformly disperse on the surface of three-dimensional (3D) directionally aligned hierarchical porous graphene aerogel (GA) networks. The novel nanocomposite catalysts exhibit over 90% NOx conversion rate in a broad temperature range (200–300°C). Addition of CeOx into the MnOx-GA catalysts significantly reduces the operational temperature at the same conversion rate. In addition to Mn4+ ions in the catalysts, the adsorbed oxygen species which can be increased by the presence of low-valence cerium contribute to high catalytic activities in the MnOx-CeOx/GA catalysts.

Novel catalysts with high activity for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures are highly demanded. In this study, mixed-node metal-organic frameworks (MOFs), e.g. Mn@CuBTC with controlled Mn composition in Cu3(BTC)2, were fabricated using postsynthetic exchange method and their structural characteristics and catalytic performances for NH3-SCR reaction were assessed. A series of analyses in terms of structure, surface morphology, texture, and chemical state determined that Mn ions were successfully incorporated into the Cu3(BTC)2 crystal lattice as well as adsorbed on the walls of nanopores in the framework. The pore sizes can be finely tuned in the presence of Mn ions in the cages, which significantly suppressed water adsorption. The NH3-SCR activity of Mn@CuBTC exhibited nearly 100% NOx conversion rate in the temperature range (230–260°C). The superior NH3-SCR performance is attributed to the proper pore sizes, reduced water content, and the synergistic effect between manganese and copper ions in the MOF structure, which enhanced NH3 bound to the active Lewis sites.

In this paper, we consider the following sublinear Kirchhoff problems -a+b∫RN∇u2dxΔu+V(x)u=f(x,u), in RN, where a>0 and b≥0 with N≥3. A new sublinear growth condition is given. When f(x,u) is not odd in u and not integrable in x, we obtain the existence of solutions for the above problem.