Calcined hydrotalcites for the catalytic decomposition of N2O in simulated process streams

Abstract Various hydrotalcite based catalysts were prepared for testing for the catalytic decomposition of N 2 O. Co Al, Ni Al, Co/Pd Al, Co/Rh Al, and Co/Mg AL substituted hydrotalcites and Co La Al hydroxides offer very good activity at modest temperatures. Precalcination of these materials at ca. 450–500°C, which destroys the hydrotalcite phase, is necessary for optimum activity and life. For Co substituted hydrotalcites, the optimal ratio of Co/Al is 3.0. The temperature for 50% conversion of N 2 O of these calcined cobalt hydrotalcites is ca. 75°C lower than for the previous highly active Co-ZSM-5. These calcined cobalt hydrotalcite materials display sustained life at temperatures in excess of 670°C in an O 2 rich, wet stream with high levels of N 2 O [10%]. Excess O 2 does not seriously impact N 2 O decomposition, but the combination of both water vapor and O 2 does reduce activity by ca. 50%.