Abstract
The effect of matrix on the characteristics of vanadium and nickel poisoning of USY zeolite has been investigated by X-ray diffraction, nitrogen adsorption, and the n-hexane cracking reaction. Alumina (Al 2O 3), magnesia-alumina (MgO·Al 2O 3), alumina-aluminum phosphate (AAP) and magnesia-alumina-aluminum phosphate (MgAAP) were used as matrices of USY. The presence of matrix can increase the resistance of USY to steam deactivation. MgO· Al 2O 3, is better at capturing vanadium than the other matrix materials. This can be attributed to the basicity of magnesium. During steam treatment, H 3VO 4 is formed and migrates to the zeolite. MgO·Al 2O 3can react with H 3VO 4 and, therefore, prevents H 23VO 4 from migrating to the USY surface. Interaction takes place between the vanadium and nickel. This interaction not only inhibits the destruction of USY structure caused by vanadium, but also leads to a decrease in the nickel's ability to produce coke. AAP has a better hydrothermal stability than the other matrices. The effect of matrix on the activities of V-poisoned catalysts decreases in the order: MgO · Al 2O 3 > MgAAP > AAP > Al 2O 3. The effect of matrix on the activities of Ni-poisoned catalysts is decreases in the order: MgO · Al 2O 3≈Al 2O 3 > MgAAP > AAP.
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