Deactivation of Copper catalysts for the oxidation of phenol aqueous solutions

MASSA; AYUDE; GONZALEZ; HAURE; FENOGLIO

Rio Grande do Sul, Brasil

Congreso; 11º Congresso de Catálise e 1º Congresso de Catálise no Mercosul; 2001

Copper oxide catalysts supported on g-alumina were prepared using a molten salt method and calcinated at different temperatures. The samples were characterized using techniques such as TPR, XRD, BET areas and AA. Their activity, selectivity and stability were tested for the oxidation of 5g/l of phenol solution in a semi- batch autoclave reactor at 140 °C and 6 atm of oxygen pressure. Phenol conversion vs. time shows a continuous overall decrease in activity for the catalyst calcinated at 900°C (C2). In turn, the catalyst calcinated at 400°C (C1) reach a steady activity plateau of 85 % during the first 40 hrs. After this time phenol, conversion decrease is more pronounced. For both catalysts, the CO2 production decreases with time. Differences in catalytic behavior are explained by means of TPR, XRD and AA analysis performed in fresh and used samples. Catalyst C1 showed a single OCu phase. Higher calcination temperatures favored the formation of a bulk CuAl2O4 phase. The solubilization of the CuO phase is responsible for the activity decrease for catalyst C1. The elution phenomena are less pronounced for catalyst C2, as suggested by TPR profiles. Copper oxide catalysts supported on g-alumina were prepared using a molten salt method and calcinated at different temperatures. The samples were characterized using techniques such as TPR, XRD, BET areas and AA. Their activity, selectivity and stability were tested for the oxidation of 5g/l of phenol solution in a semi- batch autoclave reactor at 140 °C and 6 atm of oxygen pressure. Phenol conversion vs. time shows a continuous overall decrease in activity for the catalyst calcinated at 900°C (C2). In turn, the catalyst calcinated at 400°C (C1) reach a steady activity plateau of 85 % during the first 40 hrs. After this time phenol, conversion decrease is more pronounced. For both catalysts, the CO2 production decreases with time. Differences in catalytic behavior are explained by means of TPR, XRD and AA analysis performed in fresh and used samples. Catalyst C1 showed a single OCu phase. Higher calcination temperatures favored the formation of a bulk CuAl2O4 phase. The solubilization of the CuO phase is responsible for the activity decrease for catalyst C1. The elution phenomena are less pronounced for catalyst C2, as suggested by TPR profiles.