Study on Catalytic Steam Reforming of Toluene over Ni/Activated Carbon Catalysts Prepared from Adsorption Treatment of Nickel Electroplating Wastewater by Activated Carbon

Abstract

The conditions (adsorption duration and pH) for removal of nickel ions from nickel electroplating wastewater by adsorbing on activated carbon were studied. Ni/AC catalysts prepared by adsorption under alkaline conditions with high removal rate of Ni(II) has been chosen for catalytic steam reforming of toluene, and its catalytic performances were evaluated compared to that of Ni/AC catalysts prepared by impregnation. Alkaline conditions facilitated the removal of Ni(II) from nickel electroplating wastewater by AC and pH=9 in especial, was a critical point above which Ni(II) could be removed efficiently. The removal rate within 20 min reached up to more than 97%. After H2 reduction, the catalytic activity of Ni/AC-Ad was observed in catalytic steam reforming of toluene and then gradually decreased with the reaction time. Both the toluene conversion and hydrogen production with Ni/AC-Ad were about 65% of those with Ni/AC-Im at similar Ni loading rate. Under alkaline conditions, most of the nickel adsorbed on AC was Ni(OH)2 complex. This adsorption state led to a larger average size of nickel particle in Ni/AC-Ad than that in Ni/AC-Im. The uneven size of nickel particles on the surface caused poor dispersion of active spots, agglomeration and sintering, resulting in gradual deactivation of Ni/AC-Ad prepared under alkaline conditions during catalytic steam reforming of toluene.