Gasification of glycerol over Ni/γ-Al2O3 for hydrogen production : tailoring catalytic properties to control deactivation

Abstract

The effects of catalyst loading, calcination and reaction temperatures on the structural properties and catalytic behavior of Ni/γ-Al2O3 catalyst system in relation to steam reforming of glycerol and catalyst deactivation were investigated. The results showed that catalyst loading, reaction and calcination temperatures had a profound influence on the structure and catalytic activity in glycerol conversion. Use of high calcination temperature (900-1000 °C) led to phase transformation of the active Ni/Al2O3 to less active spinel specie NiAl2O4 that resulted in a successive change of texture and color. The particle size growth and phase change at this temperature were responsible for the catalyst deactivation and low performance especially among the catalyst calcined at high temperatures. Conversely, at low reaction temperatures, catalyst surfaces were marred by carbon deposition. Whilethe polymeric carbon deposited at metal-support interface was associated with low reaction temperatures, high reaction temperatures were characterized predominantly by both amorphous carbon deposited on the active metal surface and polymeric or graphitic carbon deposited at metal-support interface respectively. Calcination temperature showed no significant influence on the location and type of coke deposited on the catalyst surface. Hence, catalyst loading, calcination and reaction temperatures could be tailored to enhance structural and catalytic properties and guard against catalyst deactivation.