Characterization of the active sites on the surface of Al2O3 ethanol dehydration catalysts by EPR using spin probes

Several pure and doped alumina samples were characterized by EPR using spin probes and tested in ethanol dehydration. It was found that the concentrations of the electron acceptor sites and the catalytic activity increased when alumina was modified with chlorides and sulfates. Meanwhile, the number of the electron donor sites decreased. A very good correlation between the concentration of the weak acceptor sites and the catalytic activity of the acid-modified catalysts almost passing through the origin of the coordinates was obtained for all the studied samples. Alumina poisoning with sodium resulted in the decrease in the catalytic activity and the concentration of the weak acceptor sites. Therefore, it appears that the weak acceptor sites tested using anthracene are related to the sites active in the ethanol dehydration reaction.

An excellent correlation between the activity of anion-doped alumina catalysts in ethanol dehydration and the concentration of weak acceptor sites capable of ionizing anthracene has been observed.Figure optionsDownload high-quality image (96 K)Download as PowerPoint slideResearch highlights
► A method for characterization of weak acceptor sites on Al2O3 by EPR was developed.
► Chlorides and sulfates promote the Al2O3 catalytic activity in ethanol dehydration.
► Doping with Cl− and SO42- increases the acceptor site concentration on Al2O3.
► Doping with Na has a negative effect on the ethanol dehydration activity.
► The catalytic activity correlates with the concentration of weak acceptor sites.