CuO/NiO monolithic catalysts for NO_x removal from nitric acid plant flue gas

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• 作者：Blanco ; Jesú ; s ; Avila ; Pedro ; Suá ; rez ; Silvia ; Yates ; Malcolm ; Martin ; Juan Antonio ; et. al.
• 关键词：Selective catalytic reduction ; Nitrogen oxides ; Nitric acid plants ; Monoliths ; Copper oxide ; Nickel oxide
• 刊名：Chemical Engineering Journal
• 出版年：2004
• 出版时间：January 15, 2004
• 年：2004
• 卷：97
• 期：1
• 页码：1-9
• 全文大小：273 K

文摘

The performance of copper/nickel oxide catalysts supported on ceramic monoliths of γ-alumina/silicate, for the selective catalytic reduction (SCR) of nitrogen oxides in flue gas from nitric acid plants ([NO]/[NO_x]=0.7) has been studied. The monoliths prepared were characterised by thermogravimetry, nitrogen adsorption–desorption, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), electron probe microanalysis wavelength dispersion spectroscopy (EPMA-WDS) and their mechanical strengths were measured. The support composition and heat-treatment temperature was optimised to obtain monolithic structures with satisfactory mechanical and textural properties. Thus, a monolith with a γ-alumina/silicate weight ratio of 2/3 was selected to give the best combination of textual and mechanical properties. The influence of active phase (CuO/NiO) content and operating conditions (residence time, [NH₃]/[NO_x] ratio) on the NO_x conversion and ammonia slip was studied at laboratory scale to determine the optimum conditions for operation at pilot-plant scale. The maximum catalytic activity was achieved for a catalyst with CuO content of 6.3wt. % . At higher active phase concentration a decrease in the catalytic activity was observed, related to the formation of copper oxides crystals detected by XRD. The presence of these species increase the reaction rate of the competitive ammonia oxidation reaction and thus, reduce the ammonia concentration in the outlet. The selected monolithic catalyst was tested at pilot-plant scale with real gases from a nitric acid production plant achieving NO_x conversions of around 90vol. % , with ammonia emissions lower than 10ppm, at 230°C and GSHV (NTP) of 10,600h⁻¹.