A Cu/Al-MCM-41 mesoporous molecular sieve: application in the abatement of no in exhaust gases

• Main Authors: M. S. Batista, R. A. A. Melo, M. Wallau, E. A. Urquieta-González
• Format: Article
• Language: English
• Published: Brazilian Society of Chemical Engineering 2005-09-01
• Series: Brazilian Journal of Chemical Engineering
• Subjects: Cu-MCM-41; Cu-ZSM-5; NO reduction; Propane oxidation
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322005000300011

Propane oxidation and reduction of NO to N2 with propane under oxidative conditions on a Cu-Al-MCM-41 mesoporous molecular sieve and Cu-ZSM-5 zeolites were studied. Both types of catalysts were prepared by ion exchange in aqueous solutions of copper acetate and characterised by X-ray diffraction (XRD), nitrogen sorption measurement, diffuse reflectance ultra-violet spectroscopy (DRS-UV), diffuse reflectance infra-red Fourier transform spectroscopy (DRIFTS) of the adsorption of CO on Cu+ and temperature-programmed reduction with hydrogen (H2-TPR). The NO reduction was performed between 200 and 500 ºC using a GHSV = 42,000 h-1. H2-TPR data showed that in the prepared Cu-Al-MCM-41 all the Cu atoms are on the surface of the mesopores as highly dispersed CuO, which results in a decrease in specific surface area and in mesopore volume. H2-TPR together with DRIFTS data provided evidence that in Cu/ZSM-5 catalysts, Cu atoms are found as two different Cu2+ cations: Cualpha2+ and Cubeta2+, which are located on charge compensation sites, and their thermo-redox properties were different from those of Cu atoms in Cu-Al-MCM-41. The specific activity of the Cu2+ exchangeable cations in Cu-ZSM-5, irrespective of their nature, was much greater than that of the Cu2+ in Cu-Al-MCM-41, where they are found as CuO.