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

• Biomass lactic acid has been proven to be a promising candidate for production of bulk chemicals.
• Mg0.388Al2.408O4 was found to be an efficient catalyst for decarbonylation of lactic acid to acetaldehyde.
• Mg0.388Al2.408O4 material was first utilized in the catalytic decarbonylation reaction.

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, NH3-TPD, CO2-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 Mg0.388Al2.408O4, while at pH > 8, it is ascribed to MgAl2O4 spinel. At low calcination temperature such as 550 °C, Mg0.388Al2.408O4 can be formed, and it enhances crystallinity with an increase of calcination temperature. However, as the calcination temperature exceeded 1200 °C, the structure of Mg0.388Al2.408O4 encountered a serious destruction. Comparative study on catalytic performance for Mg0.388Al2.408O4 and MgAl2O4 spinel suggests that the former has more excellent performance than the latter. Besides mixtures including Mg0.388Al2.408O4 and Al2O3, pure MgO and pure Al2O3 were also investigated on their catalytic performance. In the presence of Mg0.388Al2.408O4, 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%).

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