还原条件对NiFe_2O_(4-δ)结构稳定性及其催化分解CO_2活性的影响

Effect of reduction condition on structure stability of NiFe_2O_(4-δ) and its catalytic performance of CO_2 decomposition

采用柠檬酸络合法制备NiFe2O4,运用XRD、DTA-TG等手段对其结构进行表征,并探讨还原条件对NiFe2O4-δ的结构稳定性及其催化分解CO2成C反应活性的影响。研究结果表明,由柠檬酸络合法制备的NiFe2O4样品量为0.5g时,利用H2还原制备氧缺位NiFe2O4-δ的最佳还原条件为还原温度320℃、氢气流量40mL/min、还原时间3h。还原温度过高、还原时间过长以及氢气流量过大,均会使NiFeO还原过度,尖晶石结构瓦解而转变成Fe(Ni)合金和α-Fe等。

Nickel ferrite, NiFe2O4, with spinel structure was prepared by citrate coordination method. The samples were characterized by X-ray diffraction (XRD) thermal gravimetric analysis (TGA). When the weight of NiFe2O4 sample was 0.5 g, the optimum reduction condition for the preparation of oxygen-deficient nickel ferrite, NiFe2O4-δ, reduced by H2 was as follows: reduction temperature was 320°C, H2 flow rate was 40 mL&middotmin-1 and reduction time was 3 h. The results also showed that the higher reduction temperature and higher H2 flow rate as well as longer reduction time led to an excessive reduction of NiFe2O4-δ and the destructiveness of its spinel structure, resulting in the formation of Fe-Ni alloy Fe(Ni) as well as α-Fe phase. © 2007 Institute of Coal Chemistry, Chinese Academy of Sciences.