Catalytic effect of phosphorus on SO2 oxidation in liquid phase: Experimental and theoretical studies

In this work, experimental and theoretical methods were used to investigate the catalytic effect of P4 on SO2 oxidation in the liquid phase. Experimental results indicated that P4 promoted SO2 oxidation by generating O3. Meanwhile, the desulfurization efficiency was inhibited by H3PO4. Theoretical results indicated that the preferential adsorption of O2 over P4 was beneficial to the formation of O3. Furthermore, the free O atom was a key role in forming O3 and P4O due to the oxidation ability of O3 and P4O for SO2. In the liquid phase desulfurization process, O2 and SO2 were firstly dissolved into the liquid phase. Then, O3 and P4O were generated from the interaction of O2 and P4. Next, SO2 moved close to O3 and was oxidized into SO3 without H3PO4. Finally, SO3 was hydrated into H2SO4 with H3PO4. The oxidation of SO2 by O3 without H3PO4 was the rate-determining step in the desulfurization process. H3PO4 slightly promoted the hydration reaction of SO3 but inhibited the oxidation of SO2. In general, the formation of H3PO4 consumed P4 and led to the decreasing desulfurization efficiency.