采用共沉淀法制备了一系列不同SiO2-3插层的Ni-Al类水滑石(Ni-Al LDH),在550℃下焙烧后评价其在乙醇氧化反应中的催化活性。并通过XRD、FT-IR、N2吸-脱附、H2-TPR和NH3-TPD等技术进行表征。结果表明,成功制备了SiO2-3插层Ni-Al水滑石;在反应温度为500℃时,Ni-Al-SiO2-3 LDH[n(Si/Al)=1.5]的焙烧产物作为催化剂表现出优异的乙醇转化率和二氧化碳选择性,分别为98%和97%。层间适量SiO2-3的引入可以改变前驱体中层板上的金属离子与层间阴离子的相互作用,使得焙烧产物中活性氧化性物种NiO的数量增多且易被还原,进而对氧化反应非常有利;而且使得催化剂显示出更高的比表面积,导致活性组分的分散度大大提高;以及更高含量的低温酸可以减少CO的吸附,进而有利于催化乙醇氧化的高活性和高选择性。
A series of Ni-Al hydrotalcite(LDH) with the intercalation of different SiO2-3 contents were prepared by coprecipitation method.Their catalytic activities in ethanol oxidation were investigated after calcination at 550℃.XRD,FT-IR,BET,H2-TPR and NH3-TPD techniques were used to characterize the prepared samples,and it indicated that Ni-Al LDH with the intercalation of SiO2-3 were successfully obtained.At the reacting temperature of 500℃,the calcined product of Ni-Al-SiO2-3 LDH[n(Si/Al)=1.5] exhibited excellent ethanol conversion(98%)and carbon dioxide selectivity(97%).The results showed that the interactive force between the metal ions on the layers and the interlayer anions in the precursor layer can be changed by the appropriate amount of SiO2-3 intercalating the Ni-Al LDH.Therefore the amount of NiO which was the active oxidizing species in the calcined product was increased,and the NiO was easily reduced.As a result,this was benefit to the oxidation reaction.The catalysts also shown higher specific surface area,resulting in a greatly increased dispersion of the active component.And higher contents of low temperature's acid can reduce the adsorption of CO,which was in turn useful for the high activity and the high selectivity in the ethanol oxidation.
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