The rate of diffusion can be quantified using the diffusion coefficient, which measures how quickly molecules spread out in space. For molecular diffusion, the diffusion coefficient depends on factors such as temperature, pressure, and the nature of the diffusing species. For Knudsen diffusion, the diffusion coefficient depends primarily on the pore size and temperature. Experimental techniques like pulsed field gradient NMR and chromatographic methods are commonly used to measure diffusion coefficients in catalytic systems.
