Study of the sulfation kinetics between SO2 and CaO catalyzed by TiO2 nano-particles

The catalytic activity of TiO2 nano-particles, prepared by a sol–gel method, was studied when added in the reaction between SO2 and CaO. The reaction products were analyzed by infrared spectrophotometry (IR) and specific surface area analysis and the kinetics and mechanisms of the sulfation catalyzed by the addition of TiO2 are discussed. The results indicate that nano-TiO2, which serves as an active catalytic center, enhances O2 transfer and is helpful in the diffusion of SO2 from the product layer to the inner unreacted CaO. As a result, the desulfurization efficiency increased. The results also suggest that the SO2 and NO must both be removed simultaneously in order to keep the sulfation rate. The desulfurization reactions are first order for SO2 concentration and zero order for O2 concentration and include two zones, the surface reaction zone and the product layer diffusion zone, with later being the rate limiting step. The apparent activation energy of the desulfurization reaction decreased with the addition nano-TiO2 as compared to that without. The unreacted shrinking reaction core model was used to investigate the reaction kinetics and was shown to describe the course of desulfurization. Lastly, the results obtained through calculation agree with the empirical data.

Research highlights▶ Study the reaction kinetics between SO2 and CaO catalyzed by TiO2 during 800–950 °C. ▶ Reaction was first order and zero order with regard to SO2 and O2 concentrations. ▶ Desulfurization reaction included surface reaction and product layer diffusion zone. ▶ Use shrinking core model calculated kinetic parameters agreeing with experiment data. ▶ The chemisorption of O2 to TiO2 surface forming an active center increasing sulfation.