Hindered diffusion of coal liquids. Quarterly report No. 10, December 18, 1994--March 17, 1995

Abstract

The design of industrial catalysts requires that the diffusivity of the reacting species within the catalyst be accurately known. Nowhere is this more important than in the area of coal liquefaction and upgrading of coal liquids. In this area one is faced with the task of processing a number of heavy oils, containing metals and other contaminants, in a variety of process dependent solvents. It is important, therefore, on the basis of predicting catalyst activity, selectivity, and optimizing reactor performance, that the diffusivities of these oil species be accurately known. Throughout the experimental runs we will utilize a high pressure, high temperature diffusion of cell system. This diffusion system has been tested through the measurement of the diffusivity of a number of model coal liquids. The following were accomplished this quarter: During this quarter, we have initiated a series of transport investigations under high temperature (360{degrees}) high pressure (500 psi, H{sub 2}) reactive conditions. We have also continued our studies of formation and precipitation of fractal molecular aggregates in porous media. Small-angle scattering as well as precipitation data are analyzed to delineate the structure of the molecular colloidal aggregates that are formed, when a fluid is injected into the pore space of a porous medium to react with, or displace the in-place fluid. The results suggest that these colloidal structures are diffusion-limited particle and cluster aggregates. This is the first conclusive evidence for fractality of such molecular aggregates, which has important implications for their stability and molecular weight distribution, as well as modelling their flow and precipitation in a porous medium.