Synthesis and characterization of vanadium species coated on alumina, magnesium oxide and hydrotalcite supports to SO_x removal

摘要

Vanadium oxide catalysts coated on MgO, Al2O3 and mixed oxide (obtained by thermal treatment of hydrotalcite) were synthesized and thoroughly characterized by X-ray fluorescence, textural analysis, temperature-programmed reduction (TPR), UV-vis with diffuse reflectance (DRS), XRD, SEM-EDX and XANES. The V2O5 loading was kept around 5 wt.% for all catalysts. The existence of vanadium preferential location in the vicinity of magnesium was ascertained for the mixed oxide. It has been proposed that the vanadium location and its dispersion are governed by the basic magnesium. The DeSO_x tests were carried out gravimetrically in a TCA/MS system at similar temperature conditions of those used in FCC units. The vanadium addition to MgO and MgO + MgAl2O4 supports led to an increase of SO3 pick-up efficiency (the absorption rate was multiplied by two to all supports in presence of vanadium) and the amount of SO3 was largely increased upon vanadium addition to both pristine MgO and mixed oxide. The reduction step of sulfate to H2S and water at lower temperature was also largely improved in presence of vanadium; this value increased five and four times for V/MgO and V/MgO + MgAhO4 catalysts, respectively.