Effect of Calcination Temperature on Mg-Al Layered Double Hydroxides (LDH) as Promising Catalysts in Oxidative Dehydrogenation of Ethanol to Acetaldehyde

Abstract

Oxidative dehydrogenation of ethanol to acetaldehyde over Mg-Al layered double hydroxides (LDH) and their differently calcined derivative catalysts was investigated in this study. The Mg-Al catalysts were synthesized via co-precipitation method and calcined at different temperatures at 450°C, 600°C and 900°C. It revealed that the calcination temperature affected the physicochemical properties and the catalytic activity of these catalysts toward the oxidative dehydrogenation of ethanol. It was found that ethanol conversion increased with increasing reaction temperature from 200 to 400°C, whereas acetaldehyde selectivity decreased. At low reaction temperature (200-300°C), the non-calcined catalyst (Mg-Al-000) showed the highest ethanol conversion, which can be attributed to the hydroxyl groups on surface having acetaldehyde as a major product. The calcination process led to formation of mixed oxide phase in Mg-Al catalysts as proven by the XRD and FT-IR results. The catalyst calcined at 450°C (Mg-Al-450) exhibited the highest basicity as measured by the CO₂-TPD with ethanol conversion of 45.8% and acetaldehyde yield of 29.7% at 350°C.