Study On Flue Gas Desulfurization Through Catalytic Reduction With Free Radicals

Sulfur dioxide is one of the main pollutants in the atmosphere. It is essential to put more efforts to flue gas desulphurization (FGD). Flue gas desulphurization through catalytic reduction means reduction of sulfur dioxide in flue gas to elemental sulfur through catalytic reaction over some kind of catalyst. Recently this field is drawing more and more attention. But there is yet a disturbing problem to be solved: oxygen in flue gas tends to have a negative effect on the activity of catalyst. Thus the main goal now is to develop an effective method to eliminate the poisoning effect of oxygen on catalyst.It has been reported that some kinds of free radicals such as methyl is ready to react with oxygen in no time. Perovskite-type oxide LaCoO3 is a proper catalyst for the reduction of sulfur dioxide by carbon monoxide. This paper focuses on flue gas desulphurization through catalytic reduction over LaCoO3 with free radicals. It was found that Oxygen in flue gas tended to have a negative effect on the catalytic activity of LaCoO3. The catalyst was poisoned by oxygen and it completely lost its catalytic activity after a certain period of time. The more oxygen there was in flue gas, the faster the catalyst lost its catalytic activity. After activation, LaCoO3 turned into La2O2S and CoS2-x (0≤x<2), which were the active phases. After poisoned by oxygen, they turned completely into oxides of lanthanum and cobalt and La2(SO4)3. Also it was found that poisoned catalyst could be reactivated after sulfurized in activation atmosphere. Free radicals generated by photolysis of acetone could easily react with oxygen, also they tended to react with other components in simulated flue gas such as sulfur dioxide.In conclusion, when catalytic reaction was cooperated with free radicals, oxygen in flue gas could be eliminated so fast that it could not poison the FGD catalyst, thus the catalytic activity of the catalyst was well maintained. The active phase of the catalyst did not get negative influence after introducing free radical reactions, the surface states didn't, either.