CO(2)-free hydrogen can be produced from coal gasification power plants by pre-combustion decarbonisation and carbon dioxide capture. Potassium carbonate promoted hydrotalcite-based and alumina-based materials are cheap and excellent materials for high-temperature (300-500 degrees C) adsorption of CO(2), and particularly promising in the sorption-enhanced water gas shift (SEWGS) reaction. Alkaline promotion significantly improves CO(2) reversible sorption capacity at 300-500 degrees C for both materials. Hydrotalcites and promoted hydrotalcites, promoted magnesium oxide and promoted gamma-alumina were investigated by in situ analytical methods (IR spectroscopy, sorption experiments, X-ray diffraction) to identify structural and surface rearrangements. All experimental results show that potassium ions actually strongly interact with aluminium oxide centres in the aluminium-containing materials. This study unambiguously shows that potassium promotion of aluminium oxide centres in hydrotalcite generates basic sites which reversibly adsorb CO(2) at 400 degrees C.

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Microstructured reactors most often contain a large number of micrometer-sized, parallel channels, instead of a large undivided reaction volume. Individual microchannels behave as plug-flow reactors without significant axial dispersion and with excellent heat and mass transfer properties. However, since the reaction takes place in a large number of parallel channels, it is important that all channels provide equal residence time and amount of catalyst volume. These issues depend not only on the flow distributor design, but also, for example, on the manufacturing tolerances. Correlations are derived to express the conversion of a multichannel microreactor explicitly as a function of the variance of a number of reactor parameters, viz. the channel flow rate, the channel diameter, the amount of catalyst in a channel, and the channel temperature. It is shown that the influence of flow maldistribution on the overall reactor conversion is relatively small, while the influences of variations in the channel diameter and the amount of catalyst coating are more pronounced. The model outcomes are also compared to experimental results of two microreactors with different catalyst distributions, which show that the presented method is able to provide a quick, though rough estimation of the influence of differences between channels on microreactor performance.

A one-dimensional reactor model has been developed to describe the performance of a sorption-enhanced steam-methane reforming and water-gas shift reactor. In part I of this paper, the model is verified using the analytical solution for the breakthrough curve and validated using the results of laboratory-scale CO 2 sorptiononly experiments. Langmuir and Freundlich isotherms are fitted to an experimentally derived adsorption isotherm, while a linear driving force model is used to describe the sorption kinetics. The breakthrough profile is accurately described using the Freundlich isotherm. This holds also when the purge flow or duration of the desorption step are decreased, provided the mass transfer coefficient is changed accordingly during the desorption step. A sensitivity analysis shows that the breakthrough profile is sensitive to the adopted isotherm model and its parameters. The molecular diffusion coefficient affects the slope of the breakthrough curve, while particle size and heat of adsorption show hardly any effect. In part II, the model will be applied to laboratory-scale sorption-enhanced steam-methane reforming experiments.