Effect of sodium addition on the performance of Co–ZnO-based catalysts for hydrogen production from bioethanol

The effect of sodium promoter on cobalt–zinc oxide catalysts was studied. Catalysts with different sodium contents (up to 1% (w/w)) were prepared by a coprecipitation method. They were studied in the steam reforming of ethanol between 523 and 723 K and characterized by transmission electron microscopy, X-ray diffraction, Raman and infrared spectroscopies, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared spectroscopy. A high segregation of sodium on the surface of catalysts took place. The sodium addition had a positive effect on the steam-reforming reaction of ethanol. Under total conversion and in the 623–723 K temperature range, the production of hydrogen from an ethanol–water (C2H5OH:H2O=1:13 molar) mixture (bioethanol) increased (5–8%) with sodium content. In addition, the incorporation of sodium resulted in the stabilization of the catalysts toward deactivation. In particular, the sodium-promoter effect was related to a decrease in carbon deposition, as evidenced by transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy.