Continuous hydrogen production from liquid-phase formic acid dehydrogenation over Pd/AC catalysts: A kinetic study
Celia Magaly Casado Martín, A. Quintanilla, José A. Casas
Abstract
Hydrogen production using formic acid (FA) as renewable carrier has been investigated in a fixed bed reactor packed with a commercial Pd/AC catalyst. For the first time, both FA disappearance and evolved gas flow rate have been monitored upon space-time, enabling the elucidation of the FA reaction pathway and the development of a kinetic model that accounts for catalyst deactivation. Nearly complete FA conversion and a production of 10 mL min-1 of hydrogen gas were achieved under the following operating conditions: CFA,0 = 1 M, T = 45 ºC and τ = 66.7 gCAT h L-1. The reaction was found not to be controlled the mass transfer limitations. The kinetic model reveals a first order with respect to FA concentration, with FA disappearing through dehydrogenation into hydrogen and CO2 (Ea = 53.6 kJ mol-1) as well as sorption onto the catalyst surface without reaction (Ea = 36.7 kJ mol-1). The catalyst deactivation is attributed to the accumulation of reaction species, including FA/HCOO- (reversibly sorbed) and CO2 (irreversibly chemisorbed), on the Pd active sites and the progressive decrease in the Pd2+/Pd0 ratio.