True Catalytic Behavior of Lactic Acid Dehydration on Zeolite Na-Y in the Gas Phase Measured by Means of a Novel Apparatus Design

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

“…The flow apparatus used in the present work is described in detail elsewhere [31]. In accordance with the desired liquid hourly space velocity (LHSV), the flow reactor was charged with a known amount of catalyst particles or with a homogeneous mixture comprising catalyst particles and quartz glass beads (600-800 lm size, Vogelsberger GmbH, Germany).…”

“…For determining _ m in , a separate experiment has to be carried out before or after the catalytic test, which is described elsewhere [31]. Mass balance was specified by the formula ð _ m out Á 100Þ= _ m in .…”

“…Owing to the metal-free flow apparatus applied in this work, the metal-catalyzed side reaction of LA is avoided [31]. Under these circumstances, LA can exclusively be converted on electrophilic (acidic) or nucleophilic (basic) sites.…”

“…Recently, we have shown that the carbonaceous deposits formed by incomplete evaporation of LA may induce substantial misinterpretation of catalyst deactivation by pretending LA consumption [31]. By means of an optimized flow apparatus, in which evaporation and reaction are performed successively in separate devices, we have been able to successfully avoid the accumulation of such deposits in the catalyst bed.…”

“…In contrast to previous publications, the conversion of LA decreased remarkably with time on stream (TOS), whereas the selectivity to AA was reduced only slightly. Basically, this particular behavior can be explained by the assumption that catalytically active sites are blocked [31].…”