The product yields from cracking a bituminous coal tar In a fixed-bed reactor were determined at various temperatures in the presence and absence of some packing materials. Synthetic zeolttes, Linde LZ-Y82, Norton Zeokn 900-H, and Davison 13-X, as well as a natural zeolite, chabarite, showed strong catalytic activity. I n contrast, molecular sieves 5-A and natural erionite having smaller pore diameters were found to be much less active. Clay minerals such as kaolinite, montmoriibnlte, and Kieselguhr exhibited catalytlc actMtles whlch were similar to those of the zeolites with small pore slzes, but they were still far more effective than quartz particles. I t was found that the zeolite LZ-Y82 was remarkably effective in converting tar to chars and gases in the temperature range of 400 to 500 OC. Among the factors involved for catalytic effectiveness are (I) an effective pore size greater than about 0.7 nm, (ii) a large internal surface area accessible to the tar vapor, and (ill) a large number of strongly acMic sites.

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Diffusion of pentane, cyclohexane, and toluene in nanocomposite films of fumed silica and poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene) is observed by pulse field gradient NMR. The apparent diffusion constant determined in this experiment depends on the time over which the diffusion measurement is made. The pure copolymer and the nanocomposites based on it are inhomogeneous materials phenomenologically similar to a porous system with the fast diffusion domains having an apparent pore size in the micron size range. In this regard the diffusion can be considered to be anomalous with slopes as low as 0.6 in plots of the logarithm of mean-square displacement vs the logarithm of time at short observation times and at lower silica content. The slower diffusing toluene and cyclohexane are influenced to a greater extent by the inhomogeneous structure when motion is considered over the same time. The addition of nanoparticles increases the diffusion constants of the penetrants substantially, and the diffusion constants from NMR are consistent with diffusion constants determined from desorption experiments. At high nanoparticle concentration, the apparent pore size increases and diffusion becomes closer to Fickian. Rotational motion of cylcohexane is characterized by deuterium spin−lattice relaxation time measurements made as a function of temperature on deuterated cyclohexane in the copolymer/nanoparticle composite. Two minima are present in the spin−lattice relaxation data, indicating the presence of two distinct rotational processes. The two processes are interpreted in terms of the presence of two domains just as in the interpretation of the diffusion data. While an increase in nanoparticle concentration increases the apparent diffusion constants at long times, it does not change rotational motion. The increase in translational mobility is attributed to improved connections between the domains.

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