Quantitative relations of the batch composition and the Si/Al ratio in the product of zeolites

An analysis of the correlation of the Si/Al ratio of faujasites with the composition of the solution phase from which they were crystallized gives with good accuracy an equation (A1) (SI/Al)(product) = 1 + b . (\SiO2\/\OH-\)(solution) where b is a constant that can be taken from the experiments. For a series of faujasites b = 2 can be observed. The batch composition can be described formally by (A2) NaAlO2 : n (NamH4-mSiO4) : pH(2)O. With some simplifying assumptions it can be concluded that (A3) (Si/Al)(product) = (b + m) . n/(b + n . m) where n is the Si/Al ratio and m the excess alkalinity (NaOH - NaAlO2)/SiO2 of the batch. From a comparison with a large number of experimental data it can be seen that Equation (A3) describes the Si/Al ratios for an extended range of batch compositions and different zeolites with good accuracy, allowing a reliable prediction of the composition of the final product from the parameters of the batch composition. Deviations observed for low Si/Al ratios can be corrected by an additional empirical term 0.3/n - 0.3. The validity of the equation and its limits are tested also for data from the literature, including unusual batch compositions.