Recent experimental and theoretical studies on Al siting/acid site distribution in zeolite framework

The catalytic performance of zeolite is significantly influenced by the steric constraints and acid property of its active acid sites that resulted from the isomorphous substitution of aluminum (Al) for silicon (Si) in lattice sites. A clear understanding on the relationship of synthesis-Al distribution-catalytic property would be beneficial to the design of zeolite catalyst with desirable acid site distribution for specific reactions. Therefore, recent experimental and theoretical research progresses on the control of Al siting or acid site distribution in zeolite framework are reviewed here with the focus on the effects of gel compositions, including structure-directing agents, Si/Al sources, charge-balance cations and heteroatoms, which are investigated by various spectroscopy techniques, for example, Si-29 and Al-27 MQ/MAS NMR spectroscopy, diffuse reflectance (DR) UV-vis spectroscopy of Co-exchanged samples and extended X-ray absorption fine structure spectroscopy, model catalytic tests and DFT calculations.