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

Catalytic combustion of a low-heating value synthetic gas, that resembles t he gas from air-blown fluidised bed gasification, was studied over palladiu m-impregnated lanthanum hexaaluminate catalyst washcoated on 400 cpsi cordi erite monoliths. Some of the prepared samples were aged in humidified air a t 1000 degrees C up to 30 days. The effects of varied palladium loading, ga s hourly space velocity, and fuel composition (ethene, water and ammonia co ncentrations) were studied by statistical evaluation of the temperatures ne eded for 10%, 50% and 95% conversion, respectively. The palladium series wa s compared to manganese-substituted and platinum-impregnated hexaaluminate samples. The results showed that gas hourly space velocity and palladium lo ading were the two most important factors influencing the ignition temperat ure 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 o bserved when comparing the activity of a fresh sample with a high loading o f 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 hi gh activity for conversion of carbon monoxide and hydrogen. (C) 1999 Elsevi er Science B.V. All rights reserved.