柴油车氧化催化技术研究进展

 柴油车氧化催化剂(DOC)主要作用在于氧化尾气中的CO、碳氢化合物(HC)和NOx;此外,氧化过程产生一定的热量,有助于下游组分的起燃。本文综述了近年来柴油车氧化催化技术的研究进展。柴油车氧化催化器由壳体、减振层、载体及催化剂四部分构成,其中催化剂是整个催化器的核心部分,决定着DOC的主要性能指标。DOC常用的活性组分有铂、铑和钯等贵金属,助剂为铈、镧等稀土元素和铜、铁、铬、锰等过渡金属,以及碱金属和碱土金属氧化物。本文论述了柴油车氧化催化技术反应过程原理,包括CO氧化、HC氧化和NO_x氧化反应机理;对柴油车氧化催化剂的失活机制包括热失活和化学失活及再生机制进行了综述;最后对柴油车氧化催化技术的发展进行了展望。

Research Progresses in Diesel Oxidation Catalysts

Tightening emission standards for heavy-duty in use diesel required a new effective diesel emission control system. Since 1989, Diesel Oxidation Catalysts (DOCs) have been adopted by Diesel passenger vehicles in Europe and a number of studies on the use of such catalysts to meet current legislation limits have been published. The primary purposes are oxidation of CO, unburned hydrocarbons, and NO, while active hydrocarbon oxidation could be also used to generate exotherms required for downstream components. The main advances for catalysts in the last decade are systematically reviewed. Special attentions are given to the structure of DOCs, fundamental reaction, and the DOCs catalysts deactivation and regeneration. DOCs consist of case package, monolith, damping layer, and catalysts. The precious metal component of the catalyst is typically regarded as the active site for the reaction. The most common precious metals used for DOCs are Pt and Pd. Catalyst deactivation is becoming a constant concern for catalytic converters, because it is a natural phenomenon caused by several methods, including sintering of active sites, poisoning by sulfurous compounds, and washcoat covered by carbon oxidation products. At last, the development tendency for DOC technology is proposed.