Methyl ethyl ketone combustion over La-transition metal (Cr, Co, Ni, Mn) perovskites

A series of LaBO3 (B = Cr, Co, Ni, Mn) and La0.9K0.1MnO3+delta perovskites have been prepared and tested as catalysts in the combustion of methyl ethyl ketone (MEK) at two concentration levels in air. Complete MEK conversion can be achieved for the most concentrated stream (1250 ppmv, WHSV = 425 h(-1)) at temperatures between 270 degrees C (manganite) and 345 degrees C (chromite). Activity is governed by the nature of the cation in position B and related to reducibility, being comparable for manganite activity with that of the much more expensive Pt-supported catalysts. Doping with K of lanthanum manganite produces an increase in surface area, as well as the formation of non-stoichiometric oxygen and a greater proportion of Mn4+ on the surface. All these factors may have a role in increasing its activity for catalytic combustion. Catalytic results suggest a marked influence of MEK concentration on the combustion rate. MEK oxidation to CO2 goes through acetaldehyde as intermediate product: methyl vinyl ketone and diacetyl (2,3-butanedione) were also formed, albeit in very low amounts. Nevertheless, acetaldehyde yield is zero at complete conversion, so the combustion of MEK can be carried out over these perovskite systems with 100% selectivity for CO2. (C) 2009 Elsevier B.V. All rights reserved.