Influence of the properties of mixed oxide catalysts on acrolein production from a mixture of alcohols
Résumé
Acrolein, the simplest of unsaturated aldehydes, has numerous applications as an intermediate product for the synthesis of valuable products1. Currently obtained by oxidation of propylene1, a process based on fossil resources, the synthesis of acrolein requires new production routes from renewable sources. This work proposes a sustainable production of acrolein from a mixture of biosourced methanol and ethanol. In a process of direct oxidation of a methanol/ethanol mixture, the aldehydes are first produced (reaction1), followed by aldolisation and dehydration to acrolein (reaction 2)2,3.
To produce selectively acrolein without COx formation in a single step from alcohols requires developing a catalyst mixture with a good balance between redox sites (FeMoOx) and acid/base mixed oxides. The ratio of acidic to basic sites was optimized by varying the percentages of both oxides in Mg-Al, Mg-Si, etc catalysts. The acid-base properties were determined by adsorption microcalorimetry of probe molecules (NH3, SO2, CH3OH...)4. Figure 1 illustrates the variation in acidity of Mg-Al catalysts as a function of alumina content. Correlations between surface acid/base properties and acrolein selectivity have been established. The contribution of each type of sites to the reaction mechanism will be discussed.
1 W.G. Etzkorn “Acrolein and Derivatives” in Kirk-Othmer Encyclopedia of Chemical Technology, 2009, 1.
2 J.L. Dubois, M. Capron, F. Dumeignil, (Arkema France), WO2014/068213A9, 2014.
3 E. Dumitriu, V. Hulea, C. Chelaru, C. Catrinescu, D. Tichit, R. Durand, Appl. Catal. A: Gen., 1999,178,145.
4 S. Bennici, A. Auroux, “Thermal analysis and calorimetry methods” in Metal Oxide Catalysis, S.D. Jackson and J.S. Hargreaves Eds., Volume 1, Chapitre 9, Wiley-VCH, 2009, 391.