Zeolites are microporous materials that find use in catalysis and adsorption.
Designing these materials for specific reactions or separations is aided by a detailed knowledge of their structure and composition and of the mechanisms through which they work. The distribution of silicon and aluminum throughout the zeolite is an important parameter because it partially determines the locations of extra-framework cations which in turn determine preferential adsorption and sieving effects. This distribution is usually unknown, however, because of the similar x-ray scattering factors for Si and Al. We have used a Simulated Annealing technique to determine the distribution of Si and Al by combining the local environment information from 29Si NMR with the long-range topology of the zeolite framework.