Influence of nitrogen impurity for steam methane reforming over noble metal catalysts

Ammonia by-production for steam methane reforming over alpha alumina (alpha-Al2O3) supported noble metal catalysts was investigated using the methane containing nitrogen feedstock for residential fuel cell. Ammonia is poisonous substance for carbon monooxide preferential oxidation (CO-PROX) catalyst, Pt elctrode, and proton exchange membrane (PEM) in the polymer electrolyte fuel cell system. The ammonia concentrations in the reformed gases at 700 degrees C under SV = 10,000 h(-1) condition over commertial Ni and Ru catalysts were 20 ppm and 81 ppm, respectively. In the case of the Ru catalyst, ammonia concentration almost reached the chemical equilibrium value at 700 degrees C. Ammonia formation performance over 0.5 wt% metal (Rh, Pt, Ir, and Ru) supported on alpha-Al2O3 catalyst prepared by the impregnation method was compared at 700 degrees C under SV = 2,500 h(-1) condition; the ammonia concentrations in the reformed gases over the Rh, Pt, and Ir catalysts were below 0.1 ppm. The order of ammonia formed amount over the catalysts was as follows: Ru > > Rh, Pt, Ir. The ammonia formation can be substantially suppressed during steam reforming of methane containing nitrogen over the Rh, Pt, and Ir catalysts. (C) 2016 Elsevier B.V. All rights reserved.