Green synthesis of a Cu/SiO2 catalyst for efficient H2-SCR of NO

In this work, the synthesis of Cu/SiO2 catalysts starting frompre-formed copper nanoparticle (CuNP) colloidal suspensions was carried out. Two different protocols for the CuNP synthesis were tested: (i) a green approach using water as solvent and ascorbic acid as reducer and stabilizing agent, and (ii) a second solvothermal method involving the use of diethylene glycol as solvent, sodium hypophosphite (NaH2PO2) as reducer, and polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) as stabilizing agents. In addition, and for the sake of comparison, a third catalyst was prepared by solid state conventional grinding of CuO with SiO2. The catalysts were tested in the environmentally relevant catalytic reduction of NOX with H2, in a temperature range from 300 to 500 °C. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) cycles, Raman spectroscopy, and N2 adsorption for specific surface BET measurements. From these techniques CuO and Cu(0) species were detected depending on the synthesis protocol. CuNP size and size distribution in the colloid suspensions were determined by transmission electronic microscopy (TEM). The catalyst prepared from the aqueous suspension (CuAsc/SiO2) exhibited higher NO conversion (100%) and selectivity (85%) toward N2 at the lower reaction evaluated temperature (300 °C). The CuCTAB/SiO2 catalyst obtained by the solvothermal approach showed activity at high reaction temperature (400 °C) preferentially. The metal-support mechanical mixture exhibited a negligible response at low temperature and low conversion (68%) and selectivity (88%) at 500 °C. Nanoparticle size and distribution on the support, together with the metal-support interaction, were postulated as the most plausible parameters governing the catalytic performance of the different Cu/SiO2 materials

Formazione permanente degli insegnanti di matematica. Progetto di una biblioteca distrettuale: bibliografia e schede

Schede bibliografiche di alcuni libri di matematica notevoli per studenti e insegnanti. Presentazion

Gramíneas perennes estivales. ¿Cómo integrarlas a nuestro sistema?.

La utilización de gramíneas perennes estivales puede contribuir a una disminución de riesgos y costos en los sistemas ganaderos, aportandoestabilidad y diversificación en la base forrajera. El presente artículo aborda los principales aspectos a considerar al momento de definir su inclusión, la selección de especie, su instalación y manejo, entre otros

Differential effects of nitrogen, phosphorus and water addition on native grassland seasonal ANPP stability.

Aboveground net primary productivity (ANPP) changes in response to temporal fluctuations in weather (Polley et al.2013) and soil nutrients (Harpole et al 2011). ANPPvariations could potentially affect every ecosystem processes, thus detect changes in ANPP temporal stability has great importance in the design of strategies forgrassland management and conservation. The whole research on grasslands ANPP stability has been focused on year-to-year basis, however test the seasonal stability could be very relevant for forage budget and the provision of ecosystem services. Changes in the factors controlling ANPP, such as nutrient and water addition, could cause contrasting responses in ANPP stability in different seasons of the year due to their specific climatic conditions. However, to date, there is no evidence from field experiments to reveal different seasonal stability responses

Implantación de pasturas perennes en la zona norte con base en festuca: aspectos a tener en cuenta.

La implantación de pasturas perennes involucra el conocimiento de una serie de conceptos de manejo agronómico y de utilización del forraje que posibilitan altas productividades de materia seca de calidad sin comprometer su persistencia