Modification and sequential treatment of EU-1 zeolite in mild alkali and alkaline-acid conditions

Abstract

EU-1 zeolites were sequentially treated with low-concentration sodium carbonate (Na2CO3) and hydrochloric acid (HCl) solutions. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption, temperature programmed desorption of NH3 (NH3-TPD), solid state 27Al nuclear magnetic resonance (27Al NMR), and the catalytic performances of the treated samples were tested in the xylene isomerization reaction. The results showed that the external surface area and mesoporous volume of the sample sequentially treated with 0.05mol·L−1 Na2CO3 and 0.1mol·L−1 HCl solutions reached 73.9m2·g−1 and 0.162cm3·g−1, respectively. The catalytic performances of EU-1 zeolites were significantly improved, that the activity of the probe reaction increased from 23.03% to 23.61% and the selectivity increased from 85.09% to 87.14% compared with those of parent sample. Furthermore, it was found that only amorphous silica and alumina species was dissolved during the post-treatment process, but the framework structure and the acidic properties of EU-1 zeolite remained intact.