Steam reforming of acetone over Ni- and Co-based catalysts: Effect of the composition of reactants and catalysts on reaction pathways

Abstract

The properties of Ni/Co/Co-Ni/MgAl2O4 catalysts in the steam reforming of acetone (SRA) were investigated regarding the metallic composition and nature of catalytic site. The catalysts were characterized by nitrogen physisorption, X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, and temperature programmed reduction and desorption of acetone. Experimental data revealed that the acetone conversion pathway on the Co, Co-Ni, or Ni catalysts was strongly dependent on the nature of the metal, reaction temperature, and the oxidation state of the metal atoms in nanoparticles surface atoms. Reaction data indicated that the acetone decomposition on reduced metal catalysts at high temperatures (>350°C) occurred mainly via the HC and CCO bonds cleavage, leading to the formation of CO, H2, and C on the metal surface. At low temperatures (200°C) and in the presence of H2 in the reactor feed, the Ni catalyst catalyzed the hydrogenation of the CO and CHx species formed from acetone activation on the metallic sites, producing CH4. For Co-containing catalysts, at low temperatures (200–350°C) the metal nanoparticles surface was in a higher oxidation degree and promoted the oxidation of acetone. At high temperatures (>350°C), the hydrogenation of CHx and CO species to CH4 was determined by the nanoparticle oxidation degree, which decreased in the order Ni>Co-Ni>Co. With increased temperature, the CHx species decomposed to C and H2, instead of being hydrogenated to CH4. The oxidation of C by H2O was favored on Co-containing catalysts. The reaction pathways are discussed based on theoretical data obtained from the literature.