Modeling of two-step CO oxidation light-off on Pt/γ-Al2O3 in the presence of C3H6 and NO

Beneficial Role of Oxygen in CO and Propylene Oxidation over a Pt–Pd-Based Wiremesh Catalyst as a Retrofit Emission Control Device for Four-Stroke Gasoline Spark-Ignited Motorcycles

“…Since C 3 H 6 is adsorbed more strongly than O 2 , the presence of propylene inhibits CO oxidation . The inhibition effect of C 3 H 6 on CO oxidation observed in the present study over the wiremesh catalyst is in line with the results previously reported in the literature in the case of three-way catalyst (TWC) and diesel oxidation catalysts (DOC) using catalysts with monolithic or powdered structures. − Despite the observed shift of the CO light-off profile toward higher temperatures, the final CO conversion in the presence of C 3 H 6 under the rich condition (i.e., 97%) is higher than the corresponding value in the absence of C 3 H 6 (i.e., 73%). The reason is that during co-oxidation of CO and C 3 H 6 , the overall O 2 concentration is higher than that in individual CO oxidation.…”

“…The highest inhibition effect on C 3 H 6 oxidation occurs under the rich condition emphasizing on the significant role of self- and mutual-inhibition under oxygen-deficient environment. Since C 3 H 6 adsorption is more likely at lower temperatures, , injecting excess O 2 and decreasing C 3 H 6 :O 2 ratio in the exhaust gas can assist O 2 interaction and adsorption on the active sites, thereby promoting C 3 H 6 oxidation.…”

Doping Manganese Oxides with Ceria and Ceria Zirconia Using a One-Pot Sol–Gel Method for Low Temperature Diesel Oxidation Catalysts

“…From Figs. 2a and 3a, it can also be noted that CO lightoff curves of the Ce/Mn catalysts display a shoulder in the conversion profile, due to a slight decrease in the reaction rate within the temperature range of 450 K and 500 K. This can be attributed to the competitive adsorption between CO and hydrocarbons; particularly as intermediate species are formed on the surface during C 3 H 6 oxidation in the presence of NOx [7,10]. This shoulder is not observed in the CO light-off curves of OMS-2:60 ( Fig.…”

Spatiotemporal Investigation of the Temperature and Structure of a Pt/CeO2 Oxidation Catalyst for CO and Hydrocarbon Oxidation during Pulse Activation

“…1−3 Controlling these properties is particularly attractive for emission control catalysts since it can markedly reduce the costs of emission control systems for nearly one hundred million vehicles annually. 4 The microscopic structure of such catalysts is highly dynamic, 5 and the initial activity can rapidly diminish due to aging effects such as sintering, 6,7 incorporation into the support, oxidation, or redispersion in case of Pt, which all depend on the working lean (oxygen excess) or rich (fuel excess) conditions. 8,9 Recently, pretreatments involving exposure to oxidizing atmosphere at high temperature followed by reductive pulses were shown to recover or considerably increase the critical low temperature oxidation activity of Pt/CeO 2 -based catalysts.…”

“…Noble metal dispersion and homogeneity are key parameters for adjusting the catalytic performance of supported metal catalysts. − Controlling these properties is particularly attractive for emission control catalysts since it can markedly reduce the costs of emission control systems for nearly one hundred million vehicles annually . The microscopic structure of such catalysts is highly dynamic, and the initial activity can rapidly diminish due to aging effects such as sintering, , incorporation into the support, oxidation, or redispersion in case of Pt, which all depend on the working lean (oxygen excess) or rich (fuel excess) conditions. , Recently, pretreatments involving exposure to oxidizing atmosphere at high temperature followed by reductive pulses were shown to recover or considerably increase the critical low temperature oxidation activity of Pt/CeO 2 -based catalysts. , The concept proposed by Gänzler et al , using reductive gas pulses after a lean treatment allows tuning the noble metal particle dimensions to an optimal size for CO oxidation. This approach is highly important and needs closer examination as more recent studies demonstrated that different reactions require different noble metal particle/cluster size and oxidation state for reaching an optimal activity. ,, For instance, small, reduced Pt particles are efficient for CO oxidation, whereas NO oxidation is promoted by slightly larger Pt particles. , In both cases single site catalysts, as for example, reported for water gas shift reactions, , are less effective than catalysts that contain larger Pt entities. , …”