Hydrogen production by oxidative ethanol reforming on Co, Ni and Cu ex-hydrotalcite catalysts

Abstract

Five Co, Ni and Cu oxides derived from hydrotalcite-like precursors ( ex-LDHs) were prepared and tested in the oxidative steam reforming reaction of ethanol under autothermal conditions. Highly crystalline LDH-precursors were obtained using urea hydrolysis method and both the precursors and the calcined ex-LDH oxides were characterized with several physical and chemical techniques. It has been shown that the particle size of the segregated active metal oxide decreases upon increasing the crystallinity of the LDH-precursor. Moreover, these small particle sizes favour the strong interactions between active metals and the amorphous matrix of Al-modifying cations, which cause a high stabilization of the active metal phases. All the ex-LDH catalysts (Co–Zn–Al, Co–Mg–Al, Co–Al, Ni–Mg–Al and Cu–Mg–Al) were tested in the oxidative steam reforming of ethanol with EtOH/H 2O molar ratio ( n H 2 O / n EtOH ) of 2.28 and O 2/EtOH molar ratio ( n O 2 / n EtOH ) of 0.36, at temperatures of 848–898–948 K. All ex-LDH catalysts, apart from Cu-catalyst, reached the full ethanol conversion in the temperature range, and H 2 and CO 2 were the main reaction products. Thus, high absolute H 2 production values of 14.5 L(STP) h −1 g cat −1 at 848 K with CoZnAl ex-LDH catalyst and nearly 18 L(STP) h −1 g cat −1 at 948 K with CoAl and CoMgAl catalysts were reached, which means H 2 selectivity values of 85% at 848 K and 89% at 948 K, respectively.