DYNAMIC BEHAVIOR OF AUTOMOTIVE CATALYSTS .3. TRANSIENT ENHANCEMENT OF WATER-GAS SHIFT OVER RHODIUM
DYNAMIC BEHAVIOR OF AUTOMOTIVE CATALYSTS .3. TRANSIENT ENHANCEMENT OF WATER-GAS SHIFT OVER RHODIUM
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DOI：
10.1016/0021-9517(85)90092-2
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发表时间：
1985-01-01
影响因子：
7.3
通讯作者：
SELL, JA
中科院分区：
文献类型：
--
作者：
HERZ, RK;SELL, JA
通过比较不含Rh催化剂、不含Rh催化剂和不含Ce催化剂的反应，证明了水-气变换反应参与了含Rh催化剂在尾气中的瞬时响应。每个珠状催化剂都安装在汽油发动机排气系统的转化器中。利用红外半导体激光光谱仪对转炉进出口处的尾气中CO浓度进行了高时间分辨率的同时测量。在第一系列实验中，催化剂在富排气条件下稳定下来，然后给1-S暴露在贫排气中。在随后的从贫到富的转变之后，在所有三种催化剂上都观察到了CO排放的瞬时减少。在催化剂上CO排放的减少可以通过CO与催化剂中储存的氧的反应以及CO在催化剂中的吸附和积累来解释。两种含Rh催化剂的CO排放降幅均大于CO和氧的积累和反应所能解释的量，但与Rh上的水-气变换反应的瞬时强化相一致。由贫到富的阶跃响应实验进一步证明了水-气变换参与了三效汽车催化剂的动态行为。在空燃比循环和联邦测试程序的预热部分，时间平均的CO转化率按铂/Rh/Ce&Gt；PtCe&Gt；PtRh的顺序下降。这一排名表明，在驾驶过程中，Ce上的氧气积累和反应对CO转化的贡献略高于Rh上的水-气变换。
The participation of the water-gas shift reaction in the transient response of Rh-containing catalysts in exhaust was demonstrated by comparing the responses of a Pt/Rh/Ce/Al 2 O 3 catalyst, a Rh-free Pt/Ce/Al 2 O 3 catalyst, and a Ce-free Pt/Rh/Al 2 O 3 catalyst. Each of the bead-type catalysts was mounted in a converter in the exhaust system of a gasoline engine. Infrared diode laser spectroscopy was used to measure CO concentrations in exhaust simultaneously at the converter inlet and outlet with high time-resolution. In the first series of experiments, a catalyst was stabilized under rich exhaust and then given a 1-s exposure to lean exhaust. Following the subsequent lean-to-rich transition, a transient reduction in CO emission was observed over all three catalysts. The reduction in CO emission over the Pt Ce catalyst could be explained by reaction of CO with oxygen “stored” in the catalyst and CO adsorption and accumulation in the catalyst. The reductions in CO emissions over the two Rh-containing catalysts were greater than the amounts that could be explained by CO and oxygen accumulation and reaction but were consistent with a transient enhancement of the water-gas shift reaction over Rh. Lean-to-rich step response experiments provided further evidence of the participation of water-gas shift in the dynamic behavior of three-way automotive catalysts. During air-fuel ratio cycling and the warmed-up portion of the Federal Test Procedure, time-averaged CO conversions decreased in the order Pt/Rh/Ce> Pt Ce> Pt Rh. This ranking suggests that oxygen accumulation and reaction over Ce contributes somewhat more to CO conversion during driving than water-gas shift over Rh.