Study On Catalytic Desulfurization And Denitrification Of Flue Gas Over Modified Ti-pillaring Rectorites

Sulfur dioxide(SO2) and nitric oxide(NO)resulting from the combustion process of coal, are two major air pollutants, which are difficult to be treated, thus caused great attention in the field of air pollution control. Simultaneous catalytic reduction of SO2 and NOX (de-SO2-NOX) technology has being become the hotspot because it could reduce SO2 and NOX in only one process. CO was used as reducing agent to react with SO2 and NO to produce N2 and elemental sulfur, which could also realize the reusing of sulfur resource. Preparation of catalysts is an important factor which affects the performance for desulfurization or denitrification.TiO2-pillaring rectorite (TiO2-Rec) was firstly put forward to be used as catalysts in this process because its special structure and chemical character. TiO2-Rectorite and its modified series catalysts were prepared by sol-gel method. The modification materials are La2O3, CeO2, and CuO. Over these catalysts, separate de-SO2 (desulfurization) and simultaneous de-SO2-NOX (desulfurization and denitrification) were investigated from many aspects, such as carriers, active materials and their contents. The result showed that TiO2-Rectorite has similar property asγ-Al2O3 to be as catalyst support to reduce SO2 to elemental sulfur. Otherwise, its activity could be promoted after the adulteration of active materials. The La doped catalysts have higher de-SO2 activity, the conversions of SO2 all reached above 99%. La2O3-CuO/TiO2-Rec possesses SO2 conversion about 99% at temperature 450℃, and keep activite and stable in the broad temperature range 450-600℃. The Ce doped catalysts were proved to possess higher catalytic activity of simultaneous de-SO2-NO. At temperature 600℃, the conversion of SO2 and NO reached 98% and 84.5% separately, the selectivity to produce CO2 was 95% over CuO-CeO2/ TiO2-Rec. The SEM and X-Ray Diffraction (XRD) were used to characterize the catalysts to explore reaction mechanism, aiming to provide theoretical base for the exploitation of the modified rectorite application in the field of de-SO2 and de-NOX.Catalysts may be poisoned by oxygen (O2) and vapor (H2O) contained in the flue gas, which became the main reason to hinder the popurazation of De-SO2-NOX process. La-M/γ-Al2O3 (M=Fe, Co, Ni) catalysts were investigated in the situ of simulant plant flue gas withot O2/H2O. La-M/γ-Al2O3 (M=Fe, Co) with higher de-SO2 activity were then chosen to be investigated in the presence of O2. Both catalysts lost activity in the presence of O2, while in the same situ, La-Co/γ-Al2O3 possesses higher activity to resist O2. The sequence of the property to resist O2 in different reaction situ as below: 500℃, 1.0%O2﹥500℃, 0.5%O2﹥600℃, 0.5%O2. Spectrum of XRD showed that higher temperature and higher O2 content may accelerate O2 to react with the active sulfides, resulting in the deactivation of catalysts. Over La-Co/γ-Al2O3, the property to resist vapor poisoning was also investigated. The injection of vapor into reaction system led to reduction of de-SO2 activity. The catalysts were not completely deactivated with SO2 conversion still maintained 70%. The more vapor injected, the lower SO2 conversion obtained.