Hydrogenation of methyl benzoate to benzaldehyde over manganese oxide catalysts prepared from Mg/Mn/Al hydrotalcite-like compounds

Mn-Al and Mg-Mn-Al hydrotalcite-like compounds (HTlcs) were synthesized by a coprecipitation method. The activity of the calcined HTlcs for hydrogenation of methyl benzoate to benzaldehyde was tested. The effects of Mn/Al and Mg/Mn ratio, preparation and reaction conditions, and potassium promoter on the catalytic performance of the catalysts were investigated. The prepared catalysts give better performance than conventional 10% Mn/gamma-Al2O3 catalyst. The conversion of methyl benzoate and selectivity to benzaldehyde on 3% K/Mg0.2Mn1.8Al1 catalyst at 390degreesC are 90.0 and 88.0%, respectively. XRD, TPR and CO2-TPD studies show that the redox and basic properties of the catalysts play important roles in the reaction. A suitable degree of reduction and a small number of basic sites on the catalyst lead to a high activity and selectivity to benzaldehyde. (C) 2004 Elsevier B.V. All rights reserved.