Abstract

Rhenium and copper catalysts supported on high surface area graphite have been studied for the hydrogenation of crotonaldehyde using formic acid and pure hydrogen as hydrogen sources in the gas phase. The resulting catalysts were characterized using various techniques, such as Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) and X-ray Photoelectron Spectrosocpy (XPS), Fluorescence TXRF and Temperature programmed surface reaction (TPSR). Catalytic reaction tests were carried out at the temperatures of 140 degrees C and 180 degrees C and ambient pressure, showing good conversion levels for all the catalysts and with remarkable variations in selectivity values. So, with the monometallic rhenium catalyst the desired selectivity to crotyl alcohol when using formic acid is achieved. However, it was unable to carry out such as hydrogenation with pure hydrogen. To better understand these modifications in selectivity depending on the different hydrogen sources, both theoretical and experimental studies of the different surfaces were performed using Density Functional Theory (DFT) and Temperature-Programmed Desorption (TPD). Theoretical studies reveal the different adsorption modes of crotonaldehyde, formic acid and hydrogen depending on the metallic surface centers. Finally, the high conversions obtained with these catalysts confirms the promising future of using alternative molecules, such as formic acid, instead of molecular hydrogen as hydrogenation reactant.