Effect of pH on the preparation of high pore diameter nano-sized γ-alumina via Multi-step precipitation Method

Mesoporous γ-Al2O3 is one of the most widely used catalyst supports for commercial catalytic applications. The performance of a catalyst strongly depends on the combination of textural and physical properties of the support. Pore size of a support is essential since each catalytic system requires a unique pore size for optimal catalyst loading, diffusion and selectivity [1].In this study, nano-sized γ-Al2O3 samples were synthesized through a Multi-step precipitation method using pH swing technique. These samples are suitable for processes of heavy crude oils Hydrotreating including Hydrodemetallization and Hydrodesulfurization. γ-alumina was prepared using aluminum nitrate as acidic precursor and sodium aluminate as precipitating agent. Textural properties of nano-sized γ-alumina were controlled through adjusting the pH of reaction mixture and number of pH swing cycles. Prepared samples were characterized by XRD and SEM techniques. In addition, specific surface area and pore size distribution of the obtained samples were determined by BET method. XRD patterns revealed that the sample prepared at pH=9 and high number of pH swing cycles has a higher crystallinity. The results of BET analysis showed that synthesized γ-Al2O3 sample have an average pore diameter as high as 15 nm, pore volume of 1.06 cm2/g and specific surface area of 274 m2/g. therefore, it is suitable as a support for Hydrodemetallization (HDM) catalyst.

کلیدواژه ها:

nano-sized γ-Al2O3 ، mesoporous ، Multi-step precipitation method ، pH swing technique ، Hydrotreating