Gaining insight into the synthesis of nanosized pure zeolite NaA

• Gel composition affects the crystal phase, particle size and morphology of the zeolites. • Different morphologies such as chamfered, sharp-edged and rounded cubes can be obtained. • From gel Si/Al = 1 to 3, crystal size decreases. • Increasing supersaturation by lowering the H2O molar composition reduces the particle size. • Zeolite NaA particles down to 68 nm can be consistently produced. • Zeolite NaA adsorption depends on their chemical composition. In zeolite synthesis, controlling and reducing the particle size is advantageous for different processes in which mass transfer occurs through surface active sites. In this work, the hydrothermal synthesis of zeolite NaA has been studied in detail seeking to control the size, morphology and crystal phase of the resulting zeolite particles. Adjusting the crystallization conditions and molar composition of a SiO 2 -Al 2 O 3 -TMA 2 O-Na 2 O-H 2 O system allows for the consistent production of zeolite NaA with a particle size down to 68 nm measured by TEM, using tetramethylammonium (TMA) as the organic structure directing agent (OSDA). Within the composition region in which the LTA zeolite crystallization is favored, syntheses at higher OSDA/Na + and Si/Al ratios produce smaller particles. Depending on the synthesis gel molar formulation, different morphologies and sizes of LTA crystals (in the ∼68-760 nm range) with slightly distinct Si/Al ratios (in the 1.1-2.3 range) can be achieved. The synthesized zeolites were characterized in detail by different techniques, and their textural properties were evaluated through CO 2 and N 2 adsorption and correlated with their composition.