双金属氧化物TiO2基催化剂的氧化还原性能

摘要

以金属硝酸盐为前驱物,乙二胺四乙酸为助剂,采用正交实验设计和浸渍法制备Cu-Ni、Cu-Fe和Ni-Fe系列TiO2基双金属氧化物催化剂,通过XRD和H2-TPR进行表征,评价其氧化还原性能.结果表明,活性组分为Cu和Fe、物质的量比为0.2:0.2、pH为8.0和400 ℃焙烧的5#催化剂具有优良的氧化还原性能,起始还原温度148 ℃条件下,耗氢量达80.72 mmol·g-1.活性组分、物质的量比、pH值和焙烧温度等催化剂制备参数影响氧化还原反应的难易(起始还原温度)和强弱(耗氢量),Cu和Fe物质的量比为0.2:0.2的催化剂由于协同效应具有最低的起始还原温度和很高的耗氢量.较低物质的量比含Ni活性组分的催化剂由于形成复合金属氧化物固溶体而难以在较低温度被还原,中性或碱性条件下通过氢氧化物脱水生成金属氧化物有助于提高催化剂的耗氢量,400 ℃足以形成适宜的晶型以提高催化剂氧化还原性能.%With metal nitrate as precursor and EDTA as additive agent,TiO2-supported bimetallic oxide catalysts,Cu-Ni,Cu-Fe and Ni-Fe,were prepared by orthogonal design and impregnation method, and characterized by XRD and H2-TPR.The results indicated that the No.5 catalyst obtained at the optimal condition of Cu -Fe 0.2:0.2 mole ratio,8.0 pH value and 400 ℃ calcination temperature-showedthe best redox activity.When initial reduction temperature was 148 ℃,hydrogen consumption was 80.72mmol·g-1.The catalysts' redox difficulty(initial reduction temperature) and intensity(hydrogen consumption) were affected bypreparation parameters including active ingredient,mole ratio,pH value and calcination temperature. Catalyst with Cu - Fe molar ratio of 0.2:0.2 showed the lowest initial reduction temperature and the higher hydrogen consumption due to the synergistic effect.Ni-containing catalysts with lower molar ratio,tending toform complex metal oxide,were difficult to be reduced at lower temperature.Metal oxides formed through hydroxide dehydration under neutral or alkaline conditions were beneficial to increase the hydrogen consumption.Calcinationof 400 ℃ was sufficient to form the crystal phase required for the reaction with higher redox activity.