Reactor performance enhancement under periodic operation for the ethanol dehydration over gamma-alumina, a reaction with a stop-effect
The possibility of enhancing reactor performance under forced cycling of the inlet feed was investigated for the ethanol to ethene dehydration reaction over gamma-alumina. This reaction presents a stop-effect, i.e. a drastic increase of the reaction rate for a stepwise decrease in the inlet concentration of ethanol (Koubek et al., 1980a, b; Moravek and Kraus, 1984). This phenomenon is due to an educt inhibition, leading to the existence of an optimal inlet concentration of ethanol under steady-state conditions. Periodic operation can be used advantageously to increase the performance of the ethene production up to values higher than the maximal steady-state value. The maximum enhancement is achieved for short non-symmetric periods, with the major part of the cycle under inert gas. It was shown by simulations that for an integral reactor the parameters of the cycle have to be adjusted to the residence time. Finally the two-sites model developed for the stop-effect (Golay et al., 1997, 1999) is able to predict qualitatively the influence of all the cycle parameters.