Reaction distributions in diesel emissions catalysts

了解柴油排放催化剂 目前的预测表明，用于乘用车的柴油发动机将相对于汽油发动机增加。巧合的是，世界大部分地区即将出台的环境政策正在大幅减少柴油发动机的尾气氮氧化物和颗粒物排放。正在开发新技术以满足这些需求。一种这样的技术是NOX储存/还原（NSR），其中NOX作为硝酸盐储存在催化剂上并周期性地还原成N2。另一种是催化颗粒过滤器，其中颗粒物质（烟灰）被捕获在过滤器上并定期氧化为CO2。使用这两种技术，与传统的催化剂性能表征存在突破，因为没有稳态相关操作，并且存在反应动力学、表面物质和温度的显著轴向分布。需要理解这些参数梯度，以便成功地建模、控制和优化NOx减少和颗粒去除。我们提出的，短期目标与柴油机排放控制包括：-的NSR循环的机械描述的发展; -评价硫与NSR催化剂系统的相互作用;和-烟尘氧化的传播的烟尘过滤器的示范。这项研究工作的一个纲领性目标是开发和验证实验方法，用于评估催化反应过程作为催化剂系统内轴向位置的函数。该计划的成功将促进NSR和烟尘过滤器技术在柴油发动机上的实施，并产生更清洁的废气。此外，如果NSR技术确实被证明是有效的，那么它也适用于稀燃汽油发动机，这将导致二氧化碳排放减少和燃料节省，从而抑制当前的燃料需求。

UNDERSTANDING DIESEL EMISSIONS CATALYSTS      Current predictions indicate that diesel engines for passenger vehicles will increase relative to gasoline engines. Coincidentally, upcoming environmental policy throughout most of the world is imposing significant decreases in tailpipe NOX and particulate emissions from diesel engines. New technologies are being developed to meet these demands. One such technology is NOX storage/reduction (NSR) where NOX is stored as nitrates on a catalyst and periodically reduced to N2. Another is catalyzed particulate filters, where particulate matter (soot) is trapped on a filter and periodically oxidized to CO2. With both of these technologies, there is a break with traditional catalyst performance characterization in that there is no steady-state related operation and there are significant axial distributions of reaction kinetics, surface species and temperature. These parameter gradients need to be understood in order to successfully model, control and optimize NOX reduction and particulate removal. Our proposed, short-term objectives with respect to diesel emission control include: - the development of a mechanistic description of the NSR cycle; - evaluation of the interaction of sulfur with the NSR catalyst system; and - demonstration of the propagation of soot oxidation on a soot filter. A programmatic goal of this research effort is the development and validation of experimental methodologies for evaluating catalytic reaction processes as a function of axial position inside a catalyst system. The success of this program will facilitate the implementation of NSR and soot filter technologies onto diesel engines and result in significantly cleaner exhaust. Furthermore, if the NSR technology does prove effective, it is then applicable to lean-burn gasoline engines as well, which would result in CO2 emissions reductions and fuel savings thereby dampening current fuel demands.