Alkanolamines are the most popular absorbents used to remove CO 2 from process gas streams. Therefore, the CO 2 reaction with alkanolamines is of considerable importance. The aim of this article is to provide an overview on the kinetics of the reaction of CO 2 with aqueous solutions of alkanolamines. The various reaction mechanisms that are used to interpret experimental kinetic data -zwitterion, termolecular and base-catalyzed hydration -are discussed in detail. Recently published data on reaction kinetics of individual amine systems and their mixtures are considered. In addition, the kinetic behavior of several novel aminebased solvents that have been proposed in the literature is analyzed. Generally, the reaction of CO 2 with primary, secondary and sterically hindered amines is governed by the zwitterion mechanism, whereas the reaction with tertiary amines is described by the base-catalyzed hydration of CO 2 .
N,N-Diethylethanolamine (DEEA), which can be prepared from renewable resources, represents a candidate
alkanolamine for CO2 removal from gaseous streams. In this work, the reaction of CO2 with aqueous solutions
containing N,N-diethylethanolamine (DEEA) was studied in a stirred cell reactor with a plane, horizontal
gas−liquid interface, in the range of temperatures 298−308 K. The DEEA concentration in the aqueous
solutions was varied in the range 2−3 kmol/m3. The liquid-side mass transfer coefficient and a combined
parameter comprising the reaction rate constant and the diffusivity and solubility of CO2 in DEEA solutions
were evaluated. The effect of the addition of piperazine (PIP) as a possible absorption activator was studied,
and it was found that even with a small amount of PIP (0.1 kmol/m3) added, the CO2 absorption rate increased.
In this paper, a novel rate-based description of nonreactive and reactive dividing wall columns is presented. These highly integrated units promise advantages in the context of process intensification. Until now, published studies have been focused on the nonreactive columns, based on equilibrium stage models, whereas the modeling of both dividing wall columns and reactive dividing wall columns, using the rate-based approach, has not been done yet. In the presented model, special attention is given to phenomena that have not been considered in previous publications (e.g., heat transfer through the dividing wall). The model has been applied to a nonreactive, ternary alcohol mixture and successfully validated. The transesterification of carbonates has been identified as an interesting system for the reactive dividing wall column. This reaction system is equilibrium limited and characterized by high conversion, yet low selectivity. Initial simulation studies demonstrate that the selectivity can be significantly increased by means of the reactive dividing wall column. Besides, this highly integrated unit enables a more efficient separation of products and nonconverted reactants, resulting in a reduction in the separation unit number.
One major goal of biology is to provide a quantitative description of cellular physiology. This task is complicated by population effects, which perturb culture conditions and mask the behavior of the individual cell. To overcome these limitations, the construction and operation of a microfluidic bioreactor is presented. The new reactor concept guarantees constant environmental conditions and single cell resolution, thus it was named Envirostat (environment, constant). In the Envirostat, cells are contactless trapped by negative dielectrophoresis (nDEP) and cultivated in a constant medium flow. To control chip temperature, a Peltier device was constructed. Joule heating by nDEP was quantified with Rhodamine B in dependence of applied voltage, field mode, medium conductivity, and flow velocity. The integration of the Joule heating effect in the temperature control allowed setting and maintaining the cultivation temperature. For single cell cultivation of Saccharomyces cerevisiae, medium composition changes below 0.001% were estimated by computational fluid dynamic simulation. These changes were considered not to influence cell physiology. Finally, single S. cerevisiae cells were cultivated for more than four generations in the Envirostat, thus showing the applicability of the new reactor concept. The Envirostat facilitates single cell research and might simplify the investigation of hitherto difficult to access biological phenomena such as the true regulatory and physiological response to genetic and environmental perturbations.
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