Kinetics study of activated carbons and carbon dioxide systems

Abstract

In this project, we will look into the physical gas adsorptions between carbon dioxide with Maxsorb III. The experiment was carried out at constant temperature and fitted with various isotherm models. The experimental apparatus and procedures followed largely those of previous research. However, some modifications were made in order to obtain better results.

In addition, many techniques were also explored in order to better understand the material properties. Important material properties include surface areas and pore sizes distribution. Some of the more notable techniques used are the Scanning Electron Microscopy and Transmission Electron Microscopy. The Quantachrome Autosorb-I™ analyzer was also used to analyse the features of the porous adsorbent material. The characterization results are discussed in the chapters.

The adsorption experiments were conducted at a range of temperatures, from 278.15K – 328.15K with pressures of up to 25 bar applied to the adsorbent in a closed system. Equilibrium uptake was thus determined by applying the ideal gas law. Using the pressure and uptake data, the experimental data will be modeled with various adsorption isotherms such as Dubinin-Astakhov, Langmuir and Toth’s Isotherm models.

The Langmuir isotherm was found to fit the experimental data better than the other isotherm models. This is also in line with the theoretical models, as D-A was found to be only for suitable for experiments at much higher pressures. However, it must be noted that the experiment was carried out at low pressures of below 25 bar, and this is one of the major limiting factors for the experiment.As for the adsorption kinetics, the Linear Driving Force model provided a good fit between the proposed kinetics model and experimental uptake. However, the graph showed a sharp decline in the initial phases of the kinetics graph which suggests that the use of non isothermal kinetics model could be used to better evaluate the adsorption kinetics.