Highly active and poison-tolerant nickel catalysts for tar reforming synthesized through controlled hydrothermal synthesis

Abstract

Nickel catalysts suffer from the loss of tar reforming activity due to poisoning by syngas impurities. The strategy of increasing activity of catalysts through selection of suitable organic precipitants for hydrothermal synthesis was investigated. Catalysts were synthesized from nickel and aluminum nitrates using urea, N,N’-dimethylformamide, N-methylurea, 1,1-dimethylurea and N,N’-dimethylurea as precipitants and screened for naphthalene reforming. The catalyst prepared with urea maintained the highest reforming activity for 10 h in the presence of 50 ppmv H2S (80 % naphthalene conversion, 800 °C). This was attributed to lower chemisorption of sulfur on Ni sites, due to the larger percentage of Ni0 and Ni aluminates which are less susceptible towards sulfidation than NiO. The precipitant also influenced the water gas shift activity which was higher in case of N,N’-dimethylformamide and urea probably due to Ni aluminate formation. Thus, a type of precipitant plays an essential role in tailoring of catalysts for syngas upgrading.