以水滑石及类水滑石为前体的Mg/Al、Co/Al及Co/Mg/Al混合氧化物的合成、表征和异丙醇催化性能  

Synthesis,Characterization and Isopropanol Catalytic Reaction of Mg/Al,Co/Al and Co/Mg/Al Mixed Oxides from Hydrotalcite and Hydrotalcite-like Precursors

作　　者：刘炳华[1] 张惠良[1] 沈俭一[1] 

机构地区：[1]南京大学化学系,南京210093

出　　处：《无机化学学报》2005年第1期43-50,共8页Chinese Journal of Inorganic Chemistry

基　　金：国家自然科学基金委与中石化的联合资助重点项目(No.20233040)

摘　　要：以共沉淀法合成的水滑石(HT)和类水滑石(HTLc)为前体制备了镁铝、钴铝、钴镁铝混合氧化物,采用了BET、XRD、TG-DTA、TPR、FTIR和微量量热吸附及异丙醇催化反应进行了研究。结果表明:以HT和HTLc为前体制备的混合氧化物,其比表面积较大、并随着钴含量的增加而降低。在HT中引入Co2+离子后,由于Co2+离子的氧化还原属性,削弱了水滑石层对阴离子的键合能力,从而使其热分解温度及热稳定性降低,导至焙烧后生成的混合氧化物的比表面积比不含钴的2Mg/Al混合氧化物的低。在TPR过程中,镁铝混合氧化物不被还原,而含钴的混合氧化物的还原是经由Co3+→Co2+→Co0的过程。混合氧化物表面含有酸性位和碱性位,并随着钴含量的变化而得到调变。含钴氧化物样品的表面以L酸为主和含有很少量的B酸。异丙醇催化反应生成丙酮的选择性最高,表明样品表面的氧化还原位是主要的,随着钴的加入及含量的增大,异丙醇催化反应的转化率也是增大的。The precursors of the hydrotalcite (HT) and the Co-containing hydrotalcite-like compounds (HTLcs) using coprecipitation method and the mixed oxides of 2Mg/Al, Co/Mg/Al, 1.5Co/0.5Mg/Al and 2Co/Al using calcination of the precursors were prepared. Various measured methods, such as BET, XRD, TG-DTA, TPR, FT-IR, microcalorimetric adsorption and isopropanol catalytic reaction were used to study the physico-chemical properties of these samples. The results showed that the specific surface areas of the mixed oxides derived from the HT and HTLcs precursors are larger whereas decreased with the increase of the Co content in the sample. After the cobalt cations were introduced into the HT structure, due to the redox properties of the cobalt cations, the binding abilities of the HT layers attracted the interlayer anions were weakened, which thence enabled that the thermal decomposition temperature and the thermostability were descended, and after calcination, which resulted in the specific surface areas of the Co-containing mixed oxides are lower than that of the 2Mg/Al sample. In TPR process, the 2Mg/Al sample is not reduced, while the reduction of the Co-containing mixed oxide is via a path of Co3+ to Co2+ and then to Co-0. The surface of the mixed oxide was showed to contain the acidic sites and the basic sites, and with the change of the Co content in sample the acidic sites and the basic sites were gained some adjustments. The FT-IR indicated that on the surface of the Co-containing mixed oxide the Lewis acid sites were the main and the Bronsted acid sites were the less. The acetone selectivity of the isopropanol catalytic reaction was the highest, which indicated that the redox surface sites on these samples were in the dominant position. Due to the addition of Co and the enhancement of the Co content in these samples, the conversion of the isopropanol catalytic reaction was increased also.

关 键 词：前体 异丙醇 混合氧化物 合成 催化反应 比表面积 TPR CO^2+离子 类水滑石 催化性能 

分 类 号：O643[理学—物理化学] O731[理学—化学]