Abstract: The formation mechanism of zinc silicate in S Zorb catalyst was studied in view of deactivation and breakage of the catalyst in different degrees during the operation of the S Zorb unit. A series of catalysts with fixed zinc source, different silicon sources and different zinc source were prepared, and the aging tests were carried out in a well type aging furnace under different temperature and atmosphere conditions. The formation of zinc silicate in the catalyst was investigated by the Rietveld method, and the impact of silicon source morphology, SiO₂ content, and ZnO particle size on the formation of zinc silicate in S Zorb catalyst was simulated. The results showed that amorphous SiO₂ reacted with ZnO more easily than the crystalline SiO₂ to form zinc silicate. At 800 ℃, the yield (w) of zinc silicate reached 68.7% when amorphous SiO₂ was used as the silicon source, while the yield (w) of zinc silicate was 10.3% when pure SiO₂ with crystal structure reacted with ZnO. The larger particle size of ZnO, the less zinc silicate was formed. By comparing the formation of zinc silicate in different atmospheres, it was found that the formation of zinc silicate was promoted by the presence of water vapor and SO₂, and the formation of zinc silicate was further accelerated by the co-existence of SO₂ and water vapor.

Key words: S Zorb, desulfurization, zinc silicate, deactivation