Transient kinetics of carbon monoxide oxidation by oxygen over supported palladium/ceria/zirconia three-way catalysts in the absence and presence of water and carbon dioxide
“…It maintains constant air/fuel ratio around the stoichiometric value, where an optimal simultaneous conversion of CO, HC and NO x pollutants is achieved [12][13][14][15]. Additionally, ceria favors the dispersion of noble metal, stabilization of the size and structure of Pd-active centers and increase in thermal stability of catalysts [16]. Among all ceria-related materials, ceria-zirconia mixed oxides have received a particular attention, due to their good thermal resistance to sintering and superior high oxygen storage capacity (OSC) [17].…”
“…It maintains constant air/fuel ratio around the stoichiometric value, where an optimal simultaneous conversion of CO, HC and NO x pollutants is achieved [12][13][14][15]. Additionally, ceria favors the dispersion of noble metal, stabilization of the size and structure of Pd-active centers and increase in thermal stability of catalysts [16]. Among all ceria-related materials, ceria-zirconia mixed oxides have received a particular attention, due to their good thermal resistance to sintering and superior high oxygen storage capacity (OSC) [17].…”
“…1–2% decrease in benzene conversion after the water vapor is introduced into the reaction system. The inhibition induced by water vapor might be due to the competitive adsorption of water and benzene as well as oxygen molecules 44,45 . Fortunately, the benzene conversion could be restored to 100% after cutting off water vapor.Figure 4Effect of water vapor (1.5 vol%) on the activity of Pt/SiC@Al 2 O 3 -1 with Pt mass ratio of 0.176% for oxidation of benzene, WHSV = 60 000 mL g −1 h −1 at 250 °C for 36 h with and without water vapor.
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It would be desirable to remove volatile organic compounds (VOCs) while we eliminate the dusts using silicon carbide (SiC)-based porous ceramics from the hot gases. Aiming at functionalizing SiC-based porous ceramics with catalytic capability, we herein report a facile strategy to integrate high efficient catalysts into the porous SiC substrates for the VOC removal. We demonstrate an aqueous salt method for uniformly distributing fine platinum (Pt) particles on the alumina (Al2O3) layers, which are pre-coated on the SiC substrates as supports for VOC catalysts. We confirm that at a Pt mass loading as low as 0.176% and a weight hourly space velocity of 6000 mL g−1 h−1, the as-prepared Pt/SiC@Al2O3 catalysts can convert 90% benzene at a temperature of ca. 215 °C. The results suggest a promising way to design ceramics-based bi-functional materials for simultaneously eliminating dusts and harmful VOCs from various hot gases.
“…The effects of SV and toluene concentration on the catalytic activity of the 0.90Au 1 It has been reported that in the presence of water, water was adsorbed on the metal oxide support rather than on the precious metals [87]. [23,88].…”
The Ce0.6Zr0.3Y0.1O2 (CZY) nanorods and their supported gold and palladium alloy (zAuxPdy/CZY; z = 0.80-0.93 wt%; x or y = 0, 1, 2) nanoparticles (NPs) were prepared using the cetyltrimethyl ammonium bromide-assisted hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the oxidation of toluene. It is shown that the CZY in zAuxPdy/CZY was cubic in crystal structure, surface areas of CZY and zAuxPdy/CZY were in the range 68-77 m(2) g(-1), and the Au-Pd NPs with a size of 4.6-5.6 nm were highly dispersed on the surface of CZY nanorods. Among all the samples, 0.90Au1Pd2/CZY possessed the highest adsorbed oxygen concentration and the best low-temperature reducibility, and performed the best: T50% and T90% (temperatures required for achieving toluene conversions of 50 and 90%) were 190 and 218 °C at a space velocity of 20 000 mL (g h)(-1), respectively. The partial deactivation due to water vapor introduction was reversible. The active sites might be the surface oxygen vacancies on CZY, oxidized noble metal NPs, and/or interfaces between noble metal NPs and CZY. The apparent activation energies (37-43 kJ mol(-1)) obtained over 0.90-0.93AuxPdy/CZY were much lower than that (88 kJ mol(-1)) obtained over CZY for toluene oxidation. It is concluded that the excellent catalytic performance of 0.90Au1Pd2/CZY was associated with its high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au-Pd NPs and CZY nanorods as well as good dispersion of Au-Pd NPs.
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