Catalytic combustion of gasified biomass over hexaaluminate catalysts: influence of palladium loading and ageing

Abstract

Catalytic combustion of a low-heating value synthetic gas, that resembles the gas from air-blown fluidised bed gasification, was studied over palladium-impregnated lanthanum hexaaluminate catalyst washcoated on 400 cpsi cordierite monoliths. Some of the prepared samples were aged in humidified air at 1000°C up to 30 days. The effects of varied palladium loading, gas hourly space velocity, and fuel composition (ethene, water and ammonia concentrations) were studied by statistical evaluation of the temperatures needed for 10%, 50% and 95% conversion, respectively. The palladium series was compared to manganese-substituted and platinum-impregnated hexaaluminate samples. The results showed that gas hourly space velocity and palladium loading were the two most important factors influencing the ignition temperature of carbon monoxide, hydrogen and methane over palladium catalysts. The activity for methane conversion drops substantially over an aged palladium catalyst compared to a fresh one. A similar drop in methane conversion is observed when comparing the activity of a fresh sample with a high loading of palladium to fresh samples with lower loading of palladium. On the other hand, both the aged catalyst with an initial high loading of palladium and all fresh catalysts, both with high and low loading of palladium, have a high activity for conversion of carbon monoxide and hydrogen.