High performance noble-metal-free NiCo/AC bimetal for gasification in supercritical water

We report high performance Noble-metal-free NiCo/AC bimetal for gasification in supercritical water by the polyol reduction method with chloroplatinic acid as nucleation seed. At 475 °C and 20 min, the carbon efficiency (CE) for gasification of phenol with NiCo/AC has reached about 65%, which represents a more than 20-fold enhancement of carbon efficiency compared to the Co/AC and 6-fold compared to the Ni/AC. The CE of commercial noble Ru/C (5 wt%) catalyst is only about 15% higher than that of NiCo/AC catalyst. The catalyst was characterized by BET, XRD, XPS and TEM. The results indicate smaller and higher disperse of NiCo alloy has been achieved. By using NiCo/AC catalyst, the CE can reach about 90% at 525 °C and 60 min with a 5 wt% phenol, 0.098 kg/m3 density and catalyst loading of 0.5 g/g (the mass of NiCo/AC catalyst/the mass of phenol). The results of GC-MS indicate NiCo/AC can suppress tar successfully. A kinetic modeling was also proposed to describe gaseous product and tar formation, which gives the activation energy (Ea) 123.56 ± 31 kJ/mol and the frequency factor 16.93 ± 0.48 for gaseous products. While for tar formation, the Ea is 112.95 ± 24 kJ/mol and the frequency factor is 13.99 ± 0.37. The successful use of noble-metal-free NiCo/AC shows the potential to replace noble Ru-catalysts in SCWG process for gases fuels by bimetal.