Nichola McCann

Kinetics and Mechanism of Carbamate Formation from CO2(aq), Carbonate Species, and Monoethanolamine in Aqueous Solution

Removal of carbon dioxide from fossil-based power generation is a potentially useful technique for the reduction of greenhouse gas emissions. Reversible interaction with aqueous amine solutions is most promising. In this process, the formation of carbamates is an important reaction of carbon dioxide. In this contribution, a detailed molecular reaction mechanism for the carbamate formation between MEA (monoethanolamine) and dissolved CO(2) as well as carbonate species in aqueous solution is presented. There are three parallel, reversible reactions of the free amine with CO(2), carbonic acid, and the bicarbonate ion; the relative importance of the three paths is strongly pH dependent. Kinetic and equilibrium measurements are based on (1)H NMR and stopped-flow measurements with rate constants, equilibrium constants, and protonation constants being reported.

Comprehensive Study of the Hydration and Dehydration Reactions of Carbon Dioxide in Aqueous Solution

The reversible interactions of dissolved CO(2) with H(2)O and OH(-) to form H(2)CO(3) and HCO(3)(-) in aqueous solution have been investigated using spectrophotometric stopped-flow measurements. The progress of the reactions was monitored via indicators coupled to the pH changes during the reactions. The study, involving global analysis of the complete data set, spanned the temperature range 6.6-42.8 degrees C and resulted in the evaluation of all rate and equilibrium constants as well as activation parameters for the kinetic data and the reaction enthalpies and entropies for the equilibrium constants.

Tutorial: the modelling of chemical processes.

The modelling of chemical processes entails the computation of the concentration profiles of all reaction species as a function of the reaction time. The basis for the calculations is the system of differential equations (ODEs) that is defined by the reaction mechanism. Most textbooks on chemical kinetics concentrate on those few reaction mechanisms that lead to ODEs with explicit solutions. In this tutorial, we demonstrate that numerical integration is a viable alternative, that it can be applied to any mechanism, and that it is easy to do so. Matlab example programs illustrate the concepts and they allow the reader to explore the effects of changing conditions such as initial concentrations or rate constants etc. Example reaction mechanisms include a zero-th order enzymatic reaction and reactions at non-constant temperature and pH.

Model-Based Data Fitting

Nonlinear data fitting is an important tool for the quantitative analysis of many chemical processes. Its focus is the determination of optimal values for a set of parameters of a chemical model that quantitatively describes a collection of measured data. Aspects discussed in this chapter include (a) differently structured data sets, (b) chemical models that are used to describe chemical processes, and (c) a detailed description of algorithms used for the fitting of linear and nonlinear parameters.