Effect of liquid flow modulation on the stability of noble metal catalysts for alcohol oxidation

M. ALEJANDRA AYUDE; MIRYAN C. CASSANELLO; OSVALDO M. MARTINEZ; PATRICIA M. HAURE

Buenos Aires, Argentina

Congreso; XXII Congreso Interamericano de Ingeniería Química - V Congreso Argentino de Ingenieria Quimica; 2006

CIIQ Confederación Interamericana de Ingenieros Químicos, AAIQ Asociación Argentina de Ingenieros Químicos

The effect of slow ON-OFF liquid flow modulation on the oxidation of aqueous solutions of ethanol using a 0.5% Pd/Al2O3 commercial egg-shell catalyst was investigated in a laboratory scale Trickle Bed Reactor (TBR). The behavior of noble metal catalysts used in alcohol oxidationstrongly depends on the degree of exposure to oxygen. So, ON-OFF modulation of the liquid flow was implemented with the aim of increasing the conversion and/or reaction rate. In this mode of operation, the catalyst was cyclically exposed to oxidative and reductive environments, therefore the TBR behaved as a redox cycle reactor. Experiments were conducted at different liquid flow rates, cycle periods and splits. Significant improvements over the steady state operation were obtained when the catalyst was exposed to a short surplus of oxygen after a longer time of working in the mass transfer limited regime. Proper selection of cycle duration and an adequate start-up protocol are crucial to maintain long term catalytic activity.