Vanadium supported on carbon-coated monoliths for the SCR of NO at low temperature:effect of pore structure

摘要

Carbon-coated monoliths with different degrees of mesoporosity have been prepared.This has been accomplished by coating cordierite monoliths with a blend of two polymers,viz.Furan resin and polyethylene glycol (PEG),in different proportions.Upon carbonization at 973 K the former yields a carbon coating while the latter pyrolizes generating mesoporosity.Additionally the carbon-coated monoliths were activated with CO_2 to generate microporosity.Vanadium was impregnated in these carbon-coated monoliths by equilibrium adsorption using ammonium metavanadate as precursor and they were tested in the SCR of NO at low temperature.By increasing the amount of PEG,the mesopore volume increases in the range of narrow mesoporosity (2-5 nm).It was found that the more mesopore volume,the more oxygenated surface groups are formed.This turned out to be crucial for the deposition of vanadium in a dispersed fashion and also for the activity in the SCR of NO.On the contrary,the narrow microporosity (<0.7nm) does not contribute to enhance the dispersion of the catalyst.The kinetic rate constants of the monolithic catalyst prepared are in the range of the most active catalyst reported in the literature for the SCR of NO at low temperature.