In situ sulphated CuO_x/ZrO₂ and CuO_x/sulphated-ZrO₂ as catalysts for the reduction of NO_x with NH₃ in the presence of excess O₂

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• 作者：Daniela Pietrogiacomi ; Alessandro Magliano ; Diana Sannino ; Maria Cristina Campa ; Paolo Ciambelli and Valerio Indovina
• 关键词：NO abatement ; SCR ; Sulphated-ZrO₂ ; Supported copper oxide
• 刊名：Applied Catalysis B ; Environmental
• 出版年：2005
• 期刊代码：4_09263373
• 类别：ce
• 出版时间：2005
• 卷：60
• 期：1-2
• 页码：83-92
• 文件大小：269 K

摘要

Sulphated catalysts containing the same amount of sulphates (2.6 SO₄ nm⁻²) and a different amount of copper (0.3–3.9 Cu atoms nm⁻²), Cu/SZ, were prepared by impregnation of sulphated-ZrO₂ with toluene solutions of Cu(acetylacetonate)₂. Sulphated catalysts containing the same amount of copper (0.3 or 2.5 atoms nm⁻²) and a different amount of sulphates (up to 4.9 SO₂ nm⁻²), Cu/ZS_g, were prepared by sulphation of CuO_x/ZrO₂ (Cu/Z) via the gas-phase. Samples were characterised by Fourier transformed IR spectroscopy. The selective catalytic reduction of NO with NH₃ in the presence of excess O₂ (SCR reaction), the NH₃ + O₂ and the NO + O₂ reactions were studied in a flow apparatus.

Activity and selectivity did not depend on the sulphation method used for catalyst preparation but depended on the amount of copper and sulphate, particularly on the sulphate/copper ratio.

As on Cu/Z, on Cu/SZ Cu^II was active for both SCR and NH₃ + O₂ reactions. The presence of covalent sulphates caused lower reducibility of Cu^II to Cu^I and higher Lewis acid strength of Cu^I in Cu/SZ than in Cu/Z.

For (i) SCR, (ii) NH₃ + O₂ and (iii) NO + O₂, Cu/ZS_g were less active than the parent Cu/Z. As the sulphate content in Cu/ZS_g increased, the NO yield in the NH₃ + O₂ reaction markedly decreased, thus accounting for the increased selectivity in the SCR reaction. In CuO_x/sulphated-ZrO₂ copper ions were less prone reversibly to undergo the redox process Cu^II/Cu^I.

These findings provide new information on the role of copper and sulphate in determining the activity and selectivity for the SCR with NH₃.