Dissertation > Industrial Technology > Energy and Power Engineering > Internal combustion engine > Diesel engine > Theory

Reaction Kinetics and Characteristics of the Environmental Friendly NH3-SCR Catalysts for Diesel Exhaust Aftertreatment

Author ZhangQingMao
Tutor LvGang
School Tianjin University
Course Power Machinery and Engineering
Keywords Diesel engine Nitrogen oxides Selective Catalytic Reduction Environmentally friendly catalysts Reaction kinetics
Type Master's thesis
Year 2009
Downloads 106
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The selective catalytic reduction (SCR) is recognized internationally as the most promising the diesel engine the of NO x control technology, which has been used widely in developed countries. The lower vanadium-based SCR catalyst activity at low temperatures, high temperature selectivity highly toxic, cost, and other defects, proposed alternative to the low toxicity transition metal oxide V 2 O 5 efficient, environmentally friendly SCR catalyst development ideas and new catalyst formulations, preparation methods, structural features and catalytic reaction mechanism has conducted in-depth research, to obtain the following results: (1) coating material is lower than the surface area, The transition metal oxide instead of the ratio of the surface area of ??the catalyst has little effect; coating material is higher than the surface area, the majority of the transition metal oxide substitution are caused by the specific surface area decreased. (2) For the WO 3 is the co-catalyst, CO 2 O 3 alternative catalyst has the best activity at low temperatures; Sr 2 the O 3 La 2 the the O 3 and Ce 2 O 3 alternative heat catalyst selectivity in vanadium-based catalyst and has a the wider high activity temperature window; Fe 2 O 3 alternative high activity catalyst temperature window similar to the vanadium-based catalyst; temperature and poor selectivity of CuO alternative catalyst, high activation temperature window narrowest. (3) with the reaction of the airspeed increases, the conversion efficiency of alternative-type catalyst NO x First slowly decline, the airspeed exceeds a certain threshold value, the conversion efficiency of the rapid decline in the low-temperature reaction stage, empty speed is more significant impact on the conversion efficiency. Ammonia / nitrogen ratio lt; 1, the NO x conversion efficiency with the increase of ammonia / nitrogen ratio improved; When ammonia / nitrogen ratio ≥ 1 the NO x conversion efficiency was less affected. Oxygen content lt; 1% NO x conversion efficiency greater impact; When the oxygen content gt; 2% NO x conversion efficiency almost no effect . Water vapor so that the low-temperature activity of the alternative type of catalyst reduce, but also its high-temperature activity increased, and little change of the total high activation temperature window. (4) carrier-type Ce 2 O 3 alternative catalyst activity at low temperatures than the corresponding unsupported catalyst decreased slightly improved high-temperature activity, high activity temperature window slightly extended . (5) under the reaction conditions herein set, the substitution of the transition metal oxide catalyst NH 3 -SCR reaction mainly press the ER mechanism, through the variety of catalysts prepared in this paper the intrinsic power science research, and were compared with the findings in the literature, with a lower activation energy (35.02kJ/mol) found that the catalyst was prepared and Co-VW.

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