Citrate or hydrotalcite?: As the precursor of Pt or Ru-doped Ni/Mg(Al)O catalyst for propane oxidative reforming Original Research Article

Trace amounts of Pt- and Ru-doped Ni/Mg(Al)O catalysts were prepared by a citrate method and tested in the oxidative reforming of C3H8 under daily start-up and shut-down (DSS) operation. The activity and the sustainability of the catalysts were compared with those of the Pt- and Ru-doped Ni/Mg(Al)O catalysts derived from hydrotalcite (HT) precursor. The DSS operation of C3H8 reforming was carried out with O2 gas or O2/H2O mixed gas between 200 °C and 600 °C or 700 °C under air purging conditions. The catalysts underwent steaming treatment with H2/H2O mixed gas at 900 °C for 10 h. This allowed us to test the effect of Ni sintering on the catalyst deactivation. Coking was significantly suppressed on both HT- and citrate-derived Ni catalysts. Although both preparations produced highly dispersed Ni particles on the catalysts, the HT-derived catalysts exhibited more finely dispersed Ni particles, resulting in higher activity values than those of the citrate-derived catalysts. The regenerative activity due to redispersion of sintered Ni particles was enhanced over the HT-derived catalysts compared with the activity over citrate-derived catalysts. Although a clear redispersion of Ni particles was not observed in the oxidative reforming, i.e., in the absence of steam, the size decrease in Ni particles was more significant over the HT-derived catalysts than over the citrate-derived catalysts. The Mg(Al)O periclase structure derived from Mg-Al HT likely plays an important role in the regenerative activity of Pt- and Ru-Ni/Mg(Al)O catalysts. Pt-doping was more effective than Ru for the catalyst sustainability in the oxidative reforming of C3H8.