No abstract

No abstract

Decarbonylation of lactic acid to acetaldehyde over several solid catalysts was investigated. Among the tested catalysts, aluminum sulfate has an excellent activity. In order to further understand the main reason which influenced the catalytic activity, NH3-TPD was used to estimate the acidity of the catalyst. According to the total acid amount, aluminum sulfate has a moderate amount. Heteropolyacids have strong acidity which caused serious carbon deposition on the surface of catalysts, resulting in a rapid deactivation of catalysts. Besides, FT-IR, XRD, and SEM were also utilized to characterize the fresh catalysts and the used. As for the aluminum sulfate catalyst, an evident adsorption band occurs in 2970 cm–1, suggesting a formation of poly lactate on the surface of the catalyst, and led to deactivation of the catalyst. Other parameters such as reaction temperature, lactic acid concentration, and LHSV (liquid hourly space velocity) were also discussed. Inspiringly, at high LHSV, lactic acid was efficiently converted to acetaldehyde via a decarbonylation reaction. As for stability and the recovery of aluminum sulfate, deactivation of the catalyst belongs to temporary deactivation caused by poly lactate covering the active sites of the catalyst, and only at simple calcination under the air atmosphere, the catalyst may be compeletely regenerated. Under the optimal reaction conditions, conversion of lactic acid achieved 100%, and the selectivity of acetaldehyde achieved 92.1% at 380 °C over the aluminum sulfate catalyst.

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 N 2 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.

A mesoporous AlPO4catalyst has been found to show an excellent performance for decarbonylation of lactic acid to acetaldehyde.