Selektive Dehydratisierung von Milchsäure zu Acrylsäure an Zeolith-Katalysatoren [article]

Gregor Näfe, Universität Stuttgart, Universität Stuttgart
2015
Lactic Acid is considered to be a biogenic platform chemical as it is easily available from biomass and can be converted to a variety of industrially used compounds by means of microbial and chemical catalysts. For instance, the dehydration of lactic acid yields acrylic acid, which is an important intermediate for the production of superabsorbent polymers. Still, acrylic acid is produced solely from oil-based precursors. In order to substitute these materials by bio-based resources, the
more » ... ources, the catalyzed conversion of biogenic platforms has to be further investigated, aiming at an efficient and cheap production of compounds, such as superabsorbent polymers. Besides catalyst systems that consist of phosphates or nitrates, zeolites have been used as catalyst for the gas-phase reaction of lactic acid to acrylic acid in the past. Using zeolites, especially those that are modified by alkali-metal salts, high selectivities to acrylic acid can be obtained. However, the performance of such zeolites can significantly suffer from deactivation, by means of which the conversion rate and the selectivity are affected, provided a plug flow reactor is made use of. It is commonly believed that deactivation of the catalyst, in particular the deactivation of zeolite Na-Y, is associated with gradual formation of deposits on the catalyst surface due to degradation of lactic acid and its reaction products, which is why the selectivity of the conversion to acrylic acid is supposed to be reduced with time-on-stream while the conversion rate is expected to be not affected. Compared with this, the present results on the reaction using Na-Y reveal that the deactivation manifests itself in a decline of conversion and in only a small reduction of selectivity. The unique results are the consequence of using an optimized flow apparatus that allows studying the true catalyst deactivation behavior without falsification of the results due to experimental shortcomings. Based on the catalytic performance of a series of zeolites of the type FAU, MOR and MFI [...]
doi:10.18419/opus-1445 fatcat:dx4wmypdzffbbmbvh542m32ujq