Titanium-pillared clays (Ti-PILCs) were obtained by different ways from TiCl4, Ti(OC3H7)4 and TiOSO4, respectively. Mn-CeOx/Ti- PILCs were then prepared and their activities of selective catalytic reduction (SCR) of NO with NH3 at low-temperature were evaluated. Mn-CeOx/Ti-PILCs were characterized by X-ray diffraction, N2 adsorption, Fourier transform infrared spectroscopy, thermal analysis, temperature-programmed desorption of ammonia and H2-temperature-programmed reduction. It was found that Ti-pillar tend to be helpful for the enlargement of surface area, pore volume, acidity and the enhancement of thermal stability for Mn-CeOx/Ti-PILCs. Mn- CeOx/Ti-PILCs catalysts were active for the SCR of NO. Among three resultant Mn-CeOx/Ti-PILCs, the catalyst from TiOSO4 showed the highest activity with 98% NO conversion at 220°C, it also exhibited good resistance to H2O and SO2 in flue gas. The catalyst from TiCl4 exhibited the lowest activity due to the unsuccessful pillaring process.
Ce-ZrO2 is a widely used three-way catalyst support.Because of the large surface area and excellent redox quality,Ce-ZrO2 may have potential application in selective catalytic reduction(SCR) systems.In the present work,Ce-ZrO2 was introduced into a low-temperature SCR system and CeO2 and ZrO2 supports were also introduced to make a contrastive study.Mn/CeO2,Mn/ZrO2 and Mn/Ce-ZrO2 were prepared by impregnating these supports with Mn(NO3)2 solution,and have been characterized by N2-BET,XRD,TPR,TPD,XPS,FT-IR and TG.The activity and resistance to SO2 and H2O of the catalysts were investigated.Mn/Ce-ZrO2 and Mn/CeO2 were proved to have better low-temperature activities than Mn/ZrO2,and yielded 98.6% and 96.8% NO conversion at 180°C,respectively.This is mainly because Mn/Ce-ZrO2 and Mn/CeO2 had higher dispersion of manganese oxides,better redox properties and more weakly adsorbed oxygen species than Mn/ZrO2.In addition,Mn/Ce-ZrO2 showed a good resistance to SO2 and H2O and presented 87.1% NO conversion,even under SO2 and H2O treatment for 6 hours,and the activity of Mn/Ce-ZrO2 was almost restored to its original level after cutting off the injection of SO2 and H2O.This was due to the weak water absorption and weak sulfation process on the surface of the catalyst.
Boxiong ShenXiaopeng ZhangHongqing MaYan YaoTing Liu
The catalysts of iron-doped Mn-Ce/TiO 2(Fe-Mn-Ce/TiO 2) prepared by sol-gel method were investigated for low temperature selective catalytic reduction(SCR) of NO with NH 3.It was found that the NO conversion over Fe-Mn-Ce/TiO 2 was obviously improved after iron doping compared with that over Mn-Ce/TiO 2.Fe-Mn-Ce/TiO 2 with the molar ratio of Fe/Ti = 0.1 exhibited the highest activity.The results showed that 96.8% NO conversion was obtained over Fe(0.1)-Mn-Ce/TiO 2 at 180°C at a space velocity of 50,000 hr 1.Fe-Mn-Ce/TiO 2 exhibited much higher resistance to H 2 O and SO 2 than that of Mn-Ce/TiO 2.The properties of the catalysts were characterized using X-ray diffraction(XRD),N 2 adsorption,temperature programmed desorption(NH 3-TPD and NOx-TPD),and Xray photoelectron spectroscopy(XPS) techniques.BET,NH3-TPD and NOx-TPD results showed that the specific surface area and NH3 and NOx adsorption capacity of the catalysts increased with iron doping.It was known from XPS analysis that iron valence state on the surface of the catalysts were in Fe3+ state.The doping of iron enhanced the dispersion and oxidation state of Mn and Ce on the surface of the catalysts.The oxygen concentrations on the surface of the catalysts were found to increase after iron doping.Fe-Mn-Ce/TiO2 represented a promising catalyst for low temperature SCR of NO with NH3 in the presence of H2 O and SO2.
Boxiong Shen ,Ting Liu,Ning Zhao,Xiaoyan Yang,Lidan Deng College of Environmental Science and Engineering,Nankai University,Tianjin 300071,China.
