Formic acid decomposition over palladium based catalysts doped by potassium carbonate

The introduction of potassium carbonate into Pd/Al₂O₃, Pd/SiO₂and Pd/C catalysts promoted both the catalytic activities and the hydrogen selectivities for the vapor-phase formic acid decomposition, giving values of the turnover frequency (TOF) at 343 K that were 8-33 times higher than those for the undoped samples. The apparent activation energies over all the K-doped samples increased considerably, this showing that there is a difference in the reaction path between the doped and the undoped catalysts. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) has been used to gain an understanding of the nature of the species formed in the Pd/SiO₂catalysts during the reaction. This study showed that a considerable fraction of the HCOOH was condensed in the pores of the catalysts and that the introduction of potassium contributed to the formation of buffer-like solution. The existence of mobile formate ions present in the buffer solution and stabilized by K ions in a K-doped catalyst is an essential factor in the promotion of its activity.