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Deactivation behavior of alkali-metal zeolites in the dehydration of lactic acid to acrylic acid

: Näfe, G.; López-Martínez, M.-A.; Dyballa, M.; Hunger, M.; Traa, Y.; Hirth, T.; Klemm, E.


Journal of catalysis 329 (2015), pp.413-424
ISSN: 0021-9517
Journal Article
Fraunhofer IGB ()

A series of FAU, MFI, and MOR Na-zeolites with different nSi/nAl ratios and varying exchanged cations Li+, Na+, K+ and Cs+ are investigated as catalysts in the gas phase dehydration of lactic acid to acrylic acid. The conversions and selectivities as well as their time dependence prove to be greatly affected by the structure, the type of alkali-metal and the acidic/basic nature of the zeolite. Analyses of the catalysts after the reaction show a possible reason for the deactivation, viz. the blocking of the active sites due to the formation of deposits of clusters containing carboxyl groups. The deactivation rate is high if large adsorptive clusters can be formed and stabilized by intra- and inter-molecular hydrogen bonds. The conversion of lactic acid into acrylic acid without catalyst deactivation is possible if adsorptive accumulation is effectively excluded, e.g. when using Na-ZSM-5 zeolite.