Oxidative dehydrogenation of ethanol to acetaldehyde over magnesium aluminium layered double hydroxides catalyst

In this research, the characteristic and catalytic activity of Mg-Al LDH and their metal-modified mixed oxide were investigated. This research was divided into three parts. In the first part, the effect of calcination temperature on catalytic performance via oxidative dehydrogenation of ethanol was elucidated. The results showed that calcination temperature affected the characteristic of Mg-Al LDH, especially basicity. Moreover, the calcination temperature also affected the catalytic performance on oxidative dehydrogenation of ethanol over Mg-Al LDH. The result was consistent with the basicity of catalysts. In the second part, the Mg-Al mixed oxide derived from calcination of Mg-Al LDH was modified by loading metal (Mo, V or Cu) on the surface. The results showed that the catalytic activity of metal-modified catalyst was promoted in both dehydrogenation and oxidative dehydrogenation. The copper-modified catalyst (Cu/Mg-Al) exhibited the highest acetaldehyde yield of 41.8% at 350oC. Furthermore, the metal modification not negatively affected the stability of catalyst on oxidative dehydrogenation of ethanol upon time-on-stream for 10 h. According to further investigate the application of catalyst to bioethanol, the effect of water content in ethanol feed was studied in the third part. It revealed that water content negatively affected the catalytic performance of Cu/Mg-Al catalyst, but this effect would be eliminated at high reaction temperature. Moreover, the effect of reduction temperature on catalytic activity was elucidated by varying the pre-reduction temperature of Cu/Mg-Al catalyst (300 and 400oC). It was found that the pre-reduction step insignificantly affected the catalytic performance.