Highly efficient and robust Mg0.388Al2.408O4 catalyst for gas-phase decarbonylation of lactic acid to acetaldehyde

Abstract The process for decarbonylation of lactic acid into acetaldehyde over magnesium aluminum oxides was explored. Magnesium aluminum oxides were prepared with co-precipitation method by varying pH values, Mg/Al molar ratios and calcination temperatures. The as-prepared magnesium aluminum oxides were characterized by nitrogen adsorption–desorption, XRD, FT-IR, NH 3 -TPD, CO 2 -TPD and SEM, and were employed to catalyze the gas-phase decarbonylation of lactic acid to produce acetaldehyde. It is found that pH value is a crucial factor for the formation of magnesium aluminum oxides. At pH = 7–8, the obtained magnesium aluminum oxide is indexed to Mg 0.388 Al 2.408 O 4 , while at pH > 8, it is ascribed to MgAl 2 O 4 spinel. At low calcination temperature such as 550 °C, Mg 0.388 Al 2.408 O 4 can be formed, and it enhances crystallinity with an increase of calcination temperature. However, as the calcination temperature exceeded 1200 °C, the structure of Mg 0.388 Al 2.408 O 4 encountered a serious destruction. Comparative study on catalytic performance for Mg 0.388 Al 2.408 O 4 and MgAl 2 O 4 spinel suggests that the former has more excellent performance than the latter. Besides mixtures including Mg 0.388 Al 2.408 O 4 and Al 2 O 3 , pure MgO and pure Al 2 O 3 were also investigated on their catalytic performance. In the presence of Mg 0.388 Al 2.408 O 4 , the stability experiment was performed at high LA LHSV such as 13.0 h −1 . Encouragingly, the decarbonylation reaction of lactic acid proceeded efficiently at around 500 h on stream, and acetaldehyde selectivity remained constant (ca. ∼93%).