This work is concerned with the gas−liquid mass transfer in stirred tanks with gas-inducing impellers.
Experiments were performed to determine the critical impeller speed for the onset of gas induction and the
mass-transfer group k
L
a, using water, n-hexadecane, toluene, acetone, and sunflower oil at various temperatures
as liquids and hydrogen and nitrogen as gases. The use of different liquids and gases allowed the influence
of fluid properties on the mass transfer to be studied. Special emphasis is on reducing the experimental effort
in downscaling, i.e., the use of benchscale autoclaves to mimic industrial conditions. In benchscale tanks, the
capillary pressure is significant, with respect to the static liquid pressure at the impeller, and must be taken
into account to describe the critical impeller speed for gas induction. Downscaling implies relatively low
mass-transfer rates, which can be achieved by operating close to the critical impeller speed. The critical
impeller speed must be included in models for the mass-transfer rate. Our data set of k
L
a values was best
described by a dimensionless correlation, in which a Froude group (based on the stirrer speed N and the
critical stirrer speed N
cr) was used to account for the gas-induction rate, together with the Reynolds number
and Schmidt number, to account for turbulence intensity and fluid properties.
Caterpillar catalysis: Segmented flow in standard GC capillary columns, with a heterogeneous Pd catalyst on the walls, gave rapid information about catalytic processes in them. The residence time and conversion was monitored visually, greatly simplifying bench‐scale optimization. Examples show the benefits of the elimination of pore diffusion and axial dispersion. Further, we demonstrated how to quickly identify deactivating species in multistep synthesis without intermediate workup.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.