ABSTRACT
Asphaltene adsorption on iron oxide (Fe2O3) from toluene solutions and crude oils was determined experimentally and correlated with their stability and
10.1 Introduction .................................................................................................. 178 10.2 Experimental ................................................................................................ 179
10.2.1 Samples and Materials ...................................................................... 179 10.2.2 Adsorption Isotherm Studies of Asphaltene Solutions ..................... 180 10.2.3 Adsorption Kinetics of Asphaltenes from Crude Oils ..................... 180 10.2.4 Determination of Asphaltene Concentration .................................... 180 10.2.5 Evaluation of the Stability and Adsorbed Species Using
Asphaltene Solubility Profile ............................................................ 181 10.2.6 Fluorescence Measurements ............................................................. 181 10.2.7 Size Exclusion Chromatography ....................................................... 181
10.3 Results and Discussion ................................................................................. 182 10.3.1 C5 Asphaltene Adsorption ................................................................ 182
10.3.1.1 Adsorption Isotherm Analysis ........................................... 182 10.3.1.2 Effect of Temperature and Thermodynamic Parameters ... 183 10.3.1.3 Adsorbed Species ............................................................... 184
10.3.2 Crude Oils ......................................................................................... 191 10.3.2.1 Kinetic Analysis of Asphaltene Adsorption ...................... 191 10.3.2.2 Adsorbed Species ............................................................... 194
10.4 Concluding Remarks .................................................................................... 196 References .............................................................................................................. 196
aggregation behavior. The isotherms of pentane asphaltenes from toluene indicate an adsorption process that can be described using the classic Langmuir isotherm. This adsorption process is endothermic in nature. This means that it is driven by the increase of entropy either in the surface or in the solvent. It was also found that the adsorbed species are predominantly asphaltene molecules that form part of aggregates and can be identified as difficult-to-dissolve asphaltenes (DDAs). The kinetic analysis of asphaltene adsorption from three different crude oils on Fe2O3 particles indicates that equilibrium is reached within 24 h. At long contact times (1-72 h), the adsorption kinetics seems to follow a pseudo second order, indicating that in this range, the adsorption is controlled by chemisorption.
