Continuous hydrogen production from liquid-phase formic acid dehydrogenation over Pd/AC catalysts: A kinetic study

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: C FA,0 = 1 M, T = 45 degrees C and tau = 66.7 g CAT 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 CO 2 (E a = 53.6 kJ mol - 1 ) as well as sorption onto the catalyst surface without reaction (E a = 36.7 kJ mol -1 ). The catalyst deactivation is attributed to the accumulation of reaction species, including FA/ HCOO - (reversibly sorbed) and CO 2 (irreversibly chemisorbed), on the Pd active sites and the progressive decrease in the Pd 2+ /Pd 0 ratio.