Congming Tang

Barium sulphate catalyzed dehydration of lactic acid to acrylic acid

Dehydration of lactic acid was performed over various metal sulphates. BaSO4 was found to show an efficient activity for dehydration of lactic acid to acrylic acid due to the moderate acidity on its surface. Under the optimal conditions, 99.8% lactic acid conversion and 74.0% acrylic acid selectivity were achieved over the BaSO4 catalyst.

Strontium pyrophosphate modified by phosphoric acid for the dehydration of lactic acid to acrylic acid

The dehydration of lactic acid to acrylic acid over strontium catalysts was investigated. Strontium catalysts were prepared by a precipitation method. The catalysts were calcined at 500 °C for 6 hours in an air atmosphere and characterized by SEM for morphological features, by XRD for crystal phases, by FTIR for structure, by N2 sorption for specific surface area, and by the Hammett indicator method for acidity. As for bare strontium catalysts, the types of anions have significant effects on the activity due to the acidity difference of corresponding strontium salts. Among the tested anions, the pyrophosphate anion displayed an excellent catalytic performance. Adjusting the impregnated involatile acid concentration and immersion time can change the acidity of the catalysts, resulting in a higher catalytic activity. The dehydration of lactic acid is sensitive to the surface acidity of the catalysts. Moderate acidity of the catalysts can efficiently catalyze the dehydration of lactic acid to acrylic acid. Under the optimal reaction conditions, 100% lactic acid conversion and 72.2% selectivity to acrylic acid were achieved over the phosphoric acid impregnated strontium pyrophosphate catalyst.

Efficient and selective conversion of lactic acid into acetaldehyde using a mesoporous aluminum phosphate catalyst

Although acetaldehyde is a very important compound and has been utilized as a useful synthon for various important chemicals, it has been synthesized in industry through a petroleum route until now. Herein, we have successfully developed a sustainable route using a heterogeneous catalyst. In the presence of mesoporous aluminum phosphate (MAP3), the decarbonylation reaction of lactic acid proceeded efficiently, with 100% lactic acid conversion and ∼92% acetaldehyde selectivity. The catalyst shows high stability for at least 248 h. The unprecedented catalytic performance is due to rich medium acidic sites existing on the catalyst surface.

Sustainable production of acetaldehyde from lactic acid over the carbon catalysts

The synthesis of acetaldehyde from lactic acid over the carbon material catalysts was investigated. The carbon materials were characterized by scanning electron microscopy for morphologic features, by X-ray diffraction for crystal phases, by Fourier transform infrared spectroscopy for functional group structures, by N2 sorption for specific surface area and by ammonia temperature-programed desorption for acidity, respectively. Among the tested carbon catalysts, mesoporous carbon displayed the most excellent catalytic performance. By acidity analysis, the medium acidity is a crucial factor for catalytic performance: more medium acidity favored the formation of acetaldehyde from lactic acid. To verify, we compared the catalytic performance of fresh activated carbon with that of the activated carbon treated by nitric acid. Similarly, the modified activated carbon also displayed better activity due to a drastic increase of medium acidity amount. However, in contrast to fresh carbon nanotube, the treated sample displayed worse activity due to decrease of medium acidity amount. The effect of reaction temperature and time on stream on the catalytic performance was also investigated. Under the optimal reaction conditions, 100% lactic acid conversion and 91.6% acetaldehyde selectivity were achieved over the mesoporous carbon catalyst.

Production of propionic acid via hydrodeoxygenation of lactic acid over FexOy catalysts

The gas-phase hydrodeoxygenation of LA to propionic acid over Fe and its oxides was firstly investigated under various conditions. The catalysts were characterized by nitrogen adsorption–desorption, XRD, FT-IR, H2-TPR and SEM. Fe3O4 as active species was confirmed. Due to that reason, Fe2O3 can be efficiently transformed in situ to Fe3O4 under an atmosphere containing hydrogen derived from decarboxylation/or decarbonylation reaction of lactic acid, which offers the most excellent catalytic performance. The catalyst is sensitive to reaction temperature. LA conversion and its consumption rate increased with an increase of reaction temperature. Similarly, propionic acid selectivity also increased with reaction temperature in the range of 360–390 °C. But with further enhancement of reaction temperature from 390 to 400 °C, it drastically decreased since the formation rate of propionic acid reduced at 400 °C. The catalyst displayed an excellent adaptability in a wide range of LA LHSV except for 1.3 h−1. More importantly, at high LA LHSV of 26.3 h−1, the catalyst offered a satisfactory stability within 100 h on stream. Under the optimal reaction conditions, 96.7% of LA conversion and 46.7% of propionic acid selectivity were achieved.