EFFECTS OF THE COAL-WATER INTERFACE ON CATALYST LOADING AND DISPERSION FOR COAL CONVERSION
Godfried K. Abotsi
Department of Engineering
Clark Atlanta University
Atlanta, Georgia 30314
Friday, May 23, 3:00 pm
Ben Bandy Conference Center
Center for Applied Energy Research
The aim of this work is to enhance catalyst loading and dispersion in coal for improved coal liquefaction by controlling the surface charge properties of coal. The interfacial properties of coal have been applied to coal beneficiation and to the preparation of coal-water slurries. However, they have not been investigated for improved catalyst loading and dispersion in coal prior to coal liquefaction.
In this study, the surface electrochemistry of coal particles were varied by adsorption of surfactants onto the coal or by adjusting the pHs of the coal slurries. The surfactants under investigation include dodecyl dimethyl ethyl ammonium bromide (cationic), sodium dodecyl sulfate (anionic) and Triton (neutral). Zeta potential studies showed that the surface charge densities on the coal suspensions were dependent on the pH of the slurry and on the type and concentration of surfactant used. The coal particles became more negatively charged with increase in the pHs of the coal slurries.
Cationic surfactants generally created positively charged sites on the coal surface, anionic surfactants increased the negative charge densities compared to that on the original coal whereas neutral surfactants had little effect on the surface charge. Compared to the parent coal and those treated with anionic surfactants, higher molybdenum loading onto the coal was obtained after treatment with cationic surfactants. This is attributed to coulombic attraction between the anionic molybdenum species and the cationic coal surface. Liquefaction tests indicate that enhanced coal conversion may be achieved by modification of coal surface with surfactants prior to catalyst loading.