Production of H₂-free CO by decomposition of formic acid over ZrO₂ catalysts

Abstract

The decomposition of formic acid (HCOOH) over ZrO2 catalysts synthesized by precipitation method was investigated and their catalytic activity based on unit mass of catalyst was compared by varying the calcination temperature in the 500-1000 degrees C range. The calcined ZrO2 samples were characterized using temperature-programed desorption (TPD) of iso-propanol (IPA), H2O, and HCOOH as well as X-ray diffraction (XRD), pyridine-adsorbed infrared spectroscopy (Py-IR) and N-2 sorption. The catalytic activity as a function of the calcination temperature of ZrO2 showed a volcano-type curve with a maximum at 900 degrees C. The catalytic activity of ZrO2 in the decomposition of HCOOH well correlated with Bronsted acid site density, and it was influenced by the crystalline phase of ZrO2. Furthermore, the evolution of the Bronsted acid site density measured by Py-IR as a function of the calcination temperature was in good accordance with the desorption temperature determined by IPA- and HCOOH-TPD experiments. When H2O vapor was added, the conversion of HCOOH slightly decreased, while the CO selectivity remained almost constant. However, when CO was supplied, the conversion of HCOOH decreased continuously, and the selectivity to H-2 gradually increased, indicating that the formation of zirconium suboxides with characteristics approaching those of metals was successful using CO as a reductant.