Adaptive Global Carbon Monoxide Kinetic Mechanism over Platinum/Alumina Catalysts

Depcik, Christopher; Loya, Sudarshan; Srinivasan, Anand; Wentworth, Travis; Stagg-Williams, Susan M.

doi:10.3390/catal3020517

Cited by 4 publications

(3 citation statements)

References 94 publications

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“…Several studies report the differences in the activity of CO, NO, C 3 H 6 , and CH 4 oxidation on Pt and Pd catalysts during the light-off and the light-out [67,77,[81][82][83]. A typical hysteresis behavior for CO oxidation over Pt/Al 2 O 3 has been extensively studied and reported [49,53,55,56,[84][85][86][87][88][89][90]. Simultaneous oxidation of CO and CH 4 on Pt/Al 2 O 3 and Pt/CeO 2 results in a reverse hysteresis for methane oxidation [5].…”

Section: Origin Of Hysteresis Phenomenon In Low-temperature Co Oxidationmentioning

confidence: 99%

Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts

2018

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There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.

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Section: Origin Of Hysteresis Phenomenon In Low-temperature Co Oxidationmentioning

confidence: 99%

Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts

2018

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“…The large gap in T 50 from the pretreated to the aged sample, however, suggests more than sintering. Typical activation energies for this reaction are near 100 kJ/mol [15,28,29], for which rates double every 10°C.…”

Section: Single Metal Catalystsmentioning

confidence: 99%

The catalytic behavior of precisely synthesized Pt–Pd bimetallic catalysts for use as diesel oxidation catalysts

et al. 2016

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The demands of stricter diesel engine emission regulations have created challenges for current exhaust systems. With advances in low-temperature internal combustion engines and their operations, advances must also be made in vehicle exhaust catalysts. Most current diesel oxidation catalysts use heavy amounts of precious group metals (PGMs) for hydrocarbon (HC), CO, and NO oxidation. These catalysts are expensive and are most often synthesized with poor bimetallic interaction and dispersion. The goal of this work was to study the effect of aging on diesel emission abatement of Pt-Pd bimetallic nanoparticles precisely prepared with different morphologies: well dispersed core-shell versus well dispersed homogeneously alloyed versus poorly dispersed, poorly alloyed particles. Alumina and silica supports were studied. Particle morphology and dispersion were analyzed before and after hydrothermal treatments by XRD, EDX, and STEM. Reactivity as a function of aging was measured in simulated diesel engine exhaust. While carefully controlled bimetallic catalyst nanoparticle structure has a profound influence on initial or low temperature catalytic activity, the differences in behavior disappear with higher temperature aging as thermodynamic equilibrium is achieved. The metallic character of Pt-rich alumina-supported catalysts is such that behavior rather closely follows the Pt-Pd metal phase diagram. Nanoparticles disparately composed as well-dispersed core-shell (via seq-SEA), well-dispersed homogeneously alloyed (via co-SEA), and poorly dispersed, poorly alloyed (via co-DI) end up as well alloyed, large particles of almost the same size and activity. With Pd-rich systems, the oxidation of Pd also figures into the equilibrium, such that Pd-rich oxide phases appear in the high temperature forms along with alloyed metal cores. The small differences in activity after high temperature aging can be attributed to the synthesis methods, sequential SEA and co-DI which give rise, after aging, to a bimetallic surface enriched in Pd.

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“…Another approach is to simulate reaction profiles using kinetic parameters measured for individual reaction steps by conventional methods. Reactions studied using both methods vary from simple CO oxidation [32][33][34][35][36] to CO oxidation in the presence of H2 [37,38], the CO-NO reaction [32,34], hydrocarbon combustion [32,34,39], and methanol steam-reforming [39,40]. In all of these cases, only approximate agreement was observed between the experimental and simulated profiles, both for global models (based on power rate laws), and for microkinetic models.…”

Section: Precedents and Challenges In Variable-temperature Kinetic Anmentioning

confidence: 99%

Rapid extraction of quantitative kinetic information from variable-temperature reaction profiles

Coller

Vicente

Scott

2016

Chemical Engineering Journal

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Analysis of variable-temperature reaction profiles, measured in an isothermal packed-bed reactor (PBR) whose temperature increases during the experiment, has the potential to yield accurate and precise kinetic parameters quickly for some heterogeneous catalysts. The method is demonstrated here for a typical supported nanoparticle catalyst, 2 wt% Pd/Al2O3, in the oxidation of H2, C3H8 and CO by O2. These reactions do not exhibit major changes in activation energy as a function of conversion over the range of reaction conditions analyzed. Reliable and quantitative information about rate laws was extracted readily from the shapes and positions of these profiles, as an alternative to more laborious conventional kinetic analyses. Temperature and pressure gradients were minimized by the use of sieved catalyst particles and large amounts of inert diluent for both the catalyst and feed gas. Curve-fitting of analytical expressions with as few as two adjustable parameters results in remarkable agreement between models and data. First-order profiles are indeed kinetically-limited, without mass and heat transfer effects, while inverse-firstorder profiles deviate from kinetically-controlled behavior at intermediate-to-high conversions. The activation energy and reaction order with respect to the limiting reactant obtained from a single reaction profile (with appropriate data truncation for non-kinetic phenomena, as necessary) are at least as accurate and precise as those obtained from a conventional Arrhenius analysis conducted with data obtained under differential conditions, and are measured in a fraction of the experimental time. Information about more elaborate rate laws can be obtained by global curve-fitting of a family of such profiles recorded with different volumetric flow rates.

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Adaptive Global Carbon Monoxide Kinetic Mechanism over Platinum/Alumina Catalysts

Cited by 4 publications

References 94 publications

Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts

Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts

The catalytic behavior of precisely synthesized Pt–Pd bimetallic catalysts for use as diesel oxidation catalysts

Rapid extraction of quantitative kinetic information from variable-temperature reaction profiles

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