Kinetic Study of Carbon Monoxide and Propylene Oxidation on Platinum Catalysts

Abstract

were prepared and characterized with respect to surface area, CO chemisorption, temperature-programmed desorption (TPD) of CO 2 , and temperature-programmed reduction (TPR) of H 2 . The effects of basic additives on Pt/Al 2 O 3 for carbon monoxide and propylene oxidation were investigated. The reactions were performed under the stoichiometric and oxygen-deficient conditions. The addition of basic additives slightly decreases the surface area of the catalyst and does not significantly change Pt dispersion. The addition of basic additives also influences the reducibility of Pt/ Al 2 O 3 . The basicity of the catalyst is in the order Pt-K . The promoted Pt/Al 2 O 3 catalysts are much more active than the unpromoted one for CO and C 3 H 6 oxidation under the stoichiometric point. Under oxygen-deficient conditions and in the absence of water, C 3 H 6 conversions on all catalysts studied herein increase with increasing reaction temperature. Nevertheless, this phenomenon contrasts with CO conversion once oxygen is completely reacted. Pt/Al 2 O 3 exhibits the highest C 3 H 6 conversion and the lowest CO conversion among these catalysts, and the addition of CeO 2 , Na 2 O, and K 2 O on Pt/Al 2 O 3 can promote the CO conversion. Under oxygen-deficient conditions and in the presence of water, the water-gas shift and steam re-forming reactions can take place and result in increases of CO and C 3 H 6 conversions. Pt/Al 2 O 3 is the most active catalyst for the steam re-forming reaction and the lowest active catalyst for the water-gas shift reaction among these catalysts. Nevertheless, the addition of basic additives on Pt/Al 2 O 3 catalyst can significantly enhance the water-gas shift reaction that can reduce CO emission. The promotional effect is in the order K 2 O > Na 2 O > CeO 2 , that is the same order as the basicity of the promoted catalysts. Additionally, K 2 O could be a promising additive to a catalytic converter of a two-stroke motorcycle since it can significantly enhance CO conversion. IE960414U X Abstract published in Advance ACS Abstracts, February 15, 1997.

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO2Adsorption Sites

“…21 We conclude that O 2 activation on O*-covered surfaces is limited by the reaction of O 2 with a vacancy to form O* and mobile oxygen adatoms that rapidly migrate among strongly bound O* species. These data and conclusions suggest that the cleavage of O)O bonds occurs rapidly even without the assistance of coadsorbed reactants (e.g., NO* or CO*, as proposed elsewhere 15,22 Figure 3. NO oxidation rate constants increased monotonically with increasing cluster size, 6 concurrently with increases in isotopic oxygen exchange and NO 2 decomposition rates (Figure 2b).…”

Gold, an alternative to platinum group metals in automobile catalytic converters

“…One strategy is based on quickly bringing the catalyst to working temperature, including close-coupled or manifold mounted catalysts [75], electrically heated catalysts [78], exhaust gas ignition (EGI) [79,80] and combustion heated catalysts [81]. A variety of heat storage devices have also been suggested, all of which work on the principle of retaining heat from the time of the last car's shutdown until the following cold start [82].…”

0D Modelling: a Promising Means for After-treatment Issues in Modern Automotive Applications

“…Thus, the monolith temperature (T s ) is computed from an energy balance: (17) with δQ th,in , corresponds to Equation (10). δQ th,ext , designates the external heat transfer: (18) δQ REAC , corresponds to the heat release due to catalytic reactions…”