Study and characterization of carbon xerogels from tannin-formaldehyde system as catalyst support applications

Resumo

This contribution reports the use of an organic gel, xerogel, as catalyst support for Cu. The xerogel was synthesized from the system tannin-formaldehyde at pH 3, using F-127 Pluronic as surfactant. The surface area values were higher than 900 m2/g even after the Cu (10%, wt) impregnation. The morphological analysis by SEM-FEG revealed the presence of spheres arranged in a tridimensional structure. XRD diffractograms showed the presence of CuO and Cu2O crystalline phases combined with the amorphous structure of the porous carbon. From XRD analysis it is possible to infer the Cu species are heterogeneously dispersed on the support with the co-existence of small and larger clusters, which is in agreement with Raman spectroscopy. Raman study also indicated a highly defect/disorder structure of the xerogel derivatives, ensuing the short-range structural order of the carbonic structure and oxygen groups decorating the carbon surface. XPS results corroborate with XRD and Raman results, detecting the presence of CuO and Cu2O. In addition to the mentioned Cu species, XPS also detected Cu0 which may be originated from the chemical interaction between the electron oxygen groups with the Cu precursor. The high surface area and the thermal stability (~ 300 oC) of Cu/XCTF envisages its feasibly for relevant catalytic applications.

Keywords: Carbon xerogels, tannin, renewable process, catalyst support.