Alkali-metal poisoning effect of total CO and propane oxidation over Co3O4 nanocatalysts

Abstract

Cobalt oxide (Co3O4), a low-cost transitional metal oxide, has been widely studied for catalytic total oxidation of CO and hydrocarbons. However, much less attention has been paid to the poisoning effect due to alkali metals in such oxidation catalysts despite the ease of access to such poisons in both mobile and stationary combustion sources. In this study, the alkali metals such as Na, K and Li were readily deposited onto a Co3O4 catalyst to study their poisoning effect on CO and propane oxidation. 1% doping onto Co3O4 was found to increase the light-off temperature by 50 °C in CO oxidation and over 160 °C in propane oxidation. It is also noted that alkali metals exhibited a ‘locking-effect’ on oxygen of Co3O4, leading to poor oxygen mobility of alkali metal doped catalysts. During the reaction, alkali metals can significantly promote the adsorption of CO2 to form robust surface carbonate species even at high temperature, another reason for the poisoning effect of alkali metals on Co3O4 nanocatalysts for catalytic oxidation.