Configurational diffusion of asphaltenes in fresh and aged catalyst extrudates. Quarterly progress report, June 20--September 30, 1996

The objective of this research is to determine the relationship between the size and shape of coal and petroleum macromolecules and their diffusion rates i.e., effective diffusivities, in catalyst pore structures. That is, how do the effective intrapore diffusivities depend on molecule configuration and pore geometry. The study involves three tasks: Relationship between effective intrapore diffusion coefficients, molecular size, and pore geometry; Effects of solvent composition, solute concentration, and temperature on the molecular configuration and diffusion rate of coal and petroleum asphaltenes in catalyst pores; and Assessment of diffusional limitations in aged catalysts. This quarter, uptake experiments of coal and petroleum asphaltenes into porous catalyst were performed using different initial concentrations, temperatures, and solvents. The adsorption-diffusion parameters were obtained by simulating the experimental data with the mathematical model. The results showed that the adsorption constants for coal asphaltene fractions at 0.5 mg/cm{sup 3} initial concentration are less than those at 0.05 mg/cm{sup 3}, indicating the non-linearity of coal asphaltene adsorption on porous catalyst. Comparison of uptake results using different solvents showed that the adsorption constants with solvent toluene are much larger than those with THF solvent. The effect of temperature on the adsorptive uptake was complex, with the adsorptivity for coal asphaltenes at 35 C exceeding that at 25 C in the lower (< 10{sup 3}) molecular weight region; while the adsorptivities for petroleum asphaltenes are about the same at 20, 35, and 50 C