Fe-PILC for selective catalytic reduction of NO by propene under lean-burn conditions
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摘要: 采用羟基铁离子柱撑Na-Mont制备了铁柱撑黏土催化剂(Fe-PILC),铁物种作为柱撑成分,同时充当活性组分,研究其在贫燃条件下催化丙烯选择性还原NO的特性。通过XRD、N2吸附-脱附、H2-TPR、UV-vis、Py-FTIR等方法对催化剂进行物理化学性质表征,进一步研究其反应机理。研究表明,1.0Fe-PILC在450-600 ℃时NO的转化率超过98%,N2的选择性可达97%以上,且抗水蒸气和SO2的能力较强。XRD和N2吸附-脱附研究表明,Fe-PILC中铁物种柱撑进入Na-Mont层间,使催化剂的比表面积和孔容增大。H2-TPR研究表明,Fe-PILC在400 ℃左右还原能力较强,主要体现为Fe3+→Fe2+的还原。UV-vis研究表明,Fe-PILC的脱硝活性与铁氧低聚物种FexOy呈正相关。Py-FTIR研究表明,Fe-PILC表面同时含有Lewis酸和Brønsted酸性位,Lewis酸性位是C3H6与NO进行催化反应的主要活性中心。Abstract: Iron-pillared clays (Fe-PILC) were prepared by ion-exchange method and the iron species act as the pillaring components and active components and their performances for selective catalytic reduction of NO by propene were investigated under lean-burn conditions. XRD, N2 adsorption/desorption, H2-TPR, UV-vis, Py-FTIR, etc were used to characterize the catalysts. The results showed that 1.0Fe-PILC reduced more than 98% of NO at 450-600℃ and the selectivity for N2 reached 97%. The catalytic activity of the 1.0Fe-PILC was slightly influenced by water vapor and SO2. XRD and N2 adsorption/desorption characterization results showed that the iron species entered the Na-Mont interlayer and formed much larger specific surface area and pore volume. H2-TPR results indicated that Fe-PILC had a strong reduction ability at about 400 ℃, which represented the reduction of Fe3+→Fe2+. UV-vis results showed that the denitrification activity of Fe-PILC was positively correlated with the iron oxide oligomer FexOy. Py-FTIR results revealed that Lewis acid and Brønsted acid sites formed on the Fe-PILC surface. The main catalytic activity center of C3H6 and NO reaction was the Lewis acid site.
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Key words:
- lean-burn conditions /
- Fe-PILC /
- C3H6 /
- selective catalytic reduction /
- NO
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表 1 不同催化剂的物理特性
Table 1 Physical properties of different catalysts
Catalyst Fe w/(mg·g-1)a ABET/(m2·g-1) Pore volume v/(cm3·g-1) Pore diameter d/nm Na-Mont - 48.6 0.116 9.58 0.2Fe-PILC 142.91 92.0 0.233 8.11 1.0Fe-PILC 180.25 194.7 0.271 6.26 1.5Fe-PILC 190.49 181.2 0.228 5.56 a: ICP analysis results 表 2 不同催化剂的B酸和L酸含量
Table 2 Brønsted and Lewis acid content of different catalysts
Sample 150 ℃ desorption /(μmol·g-1) 300 ℃ desorption/(μmol·g-1) B L B L Na-Mont 0 45.27 0 23.19 0.2Fe-PILC 2.68 49.01 1.06 35.96 1.0Fe-PILC 4.60 108.87 1.25 58.59 1.5Fe-PILC 2.88 84.63 1.14 52.45 -
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