Investigation of the effects of biodiesel-based Na on emissions control components

A single-cylinder diesel engine was used to investigate the impact of biodiesel-based Na on emissions control components using specially blended 20% biodiesel fuel (B20). The emissions control components investigated were a diesel oxidation catalyst (DOC), a Cu-zeolite-based NH3-SCR (selective catalytic reduction) catalyst, and a diesel particulate filter (DPF). Both light-duty vehicle, DOC-SCR-DPF, and heavy-duty vehicle, DOC-DPF-SCR, emissions control configurations were employed. The accelerated Na aging is achieved by introducing elevated Na levels in the fuel, to represent full useful life exposure, and periodically increasing the exhaust temperature to replicate DPF regeneration. To assess the validity of the implemented accelerated Na aging protocol, engine-aged lean NOx traps (LNTs), DOCs and DPFs are also evaluated. To fully characterize the impact on the catalytic activity the LNT, DOC and SCR catalysts were evaluated using a bench flow reactor. The evaluation of the aged DOC samples and LNT show little to no deactivation as a result of Na contamination. However, the SCR in the light-duty configuration (DOC-SCR-DPF) was severely affected by Na contamination, especially when NO was the only fed NOx source. In the heavy-duty configuration (DOC-DPF-SCR), no impact is observed in the SCR NOx reduction activity. Electron probe micro-analysis (EPMA) reveals that Na contamination on the LNT, DOC, and SCR samples is present throughout the length of the catalysts with a higher concentration on the washcoat surface. In both the long-term engine-aged DPF and the accelerated Na-aged DPFs, there is significant Na ash present in the upstream channels; however, in the engine-aged sample lube oil-based ash is the predominant constituent. (C) 2011 Elsevier B.V. All rights reserved.

使用一台单缸柴油发动机，采用特殊调配的20%生物柴油燃料（B20）来研究基于生物柴油的钠对排放控制部件的影响。所研究的排放控制部件包括柴油氧化催化剂（DOC）、基于铜沸石的氨选择性催化还原（NH3 - SCR）催化剂以及柴油颗粒过滤器（DPF）。采用了轻型车辆（DOC - SCR - DPF）和重型车辆（DOC - DPF - SCR）的排放控制配置。通过在燃料中引入高含量的钠来实现加速钠老化，以模拟整个使用寿命的暴露情况，并定期提高排气温度来模拟DPF再生。为了评估所实施的加速钠老化方案的有效性，还对发动机老化的稀燃氮氧化物捕集器（LNTs）、DOC和DPF进行了评估。为了全面描述对催化活性的影响，使用台架流动反应器对LNT、DOC和SCR催化剂进行了评估。对老化的DOC样品和LNT的评估表明，由于钠污染，几乎没有失活现象。然而，轻型车辆配置（DOC - SCR - DPF）中的SCR受到钠污染的严重影响，尤其是当一氧化氮是唯一供给的氮氧化物源时。在重型车辆配置（DOC - DPF - SCR）中，未观察到对SCR氮氧化物还原活性的影响。电子探针微分析（EPMA）显示，LNT、DOC和SCR样品上的钠污染在催化剂的整个长度上都存在，且在涂层表面浓度较高。在长期发动机老化的DPF和加速钠老化的DPF中，上游通道都存在大量的钠灰；然而，在发动机老化的样品中，润滑油灰分是主要成分。（C）2011爱思唯尔有限公司。保留所有权利。