Gas-Phase Conversion of Glycerol to Acetol: Influence of Support Acidity on the Catalytic Stability and Copper Surface Properties on the Activity

• Autor(a) principal: Braga,Tiago Pinheiro
• Data de Publicação: 2016
• Outros Autores: Essayem,Nadine, Prakash,Swamy, Valentini,Antoninho
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016001202361
• topic: copper catalysts; support acidity; catalytic stability; glycerol conversion; acetol formation

Mesoporous mixed copper-aluminum oxides and copper-silicon oxides were synthesized with polymeric precursors route in order to evaluate the effect of the support acidity on the catalytic stability due to the carbon deposit and the copper surface characteristics on the catalytic activity for the gas-phase conversion of glycerol to acetol. The samples were characterized by different techniques such as inductively coupled plasma (ICP), thermogravimetry and differential thermal analyses (TGA-DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption isotherms, temperature-programmed reduction with H2 (H2-TPR) and microcalorimetry of NH3 adsorption. The metallic copper surface was shown by XPS, which was observed an increase with the copper loading without marked changes between Si or Al support using the same copper content. The Cu-Al catalysts present acidic properties close to that of the pure alumina support while the Cu-Si solid is not acid, as expected. Reduced catalysts were evaluated in the reaction of glycerol conversion. The catalytic results showed a clear dependence of the glycerol conversion to acetol with the Cu metal surface and the initial catalytic properties did not depend on the support acidity, since the copper is the major active site. It was observed 95% of acetol selectivity and 80% of glycerol conversion for the best catalyst. However, the support acidity influenced the catalyst stability, since Cu-Al solid deactivated continuously by contrast to Cu-Si sample, which reached stability after 2 h of reaction. The higher acidity for the Al support leads to a greater carbon deposit compared to Si support, blocking the active sites and providing a rapid catalytic deactivation.