Effect of CeO2 on the properties of the Pd/Co3O4/cordierite catalyst in the conversion of CO, NO, and hydrocarbons

Abstract

The effect of CeO 2 on the properties of the Pd/Co 3 O 4 -CeO 2 /cordierite catalyst is a function of the method of its preparation. The catalyst obtained by the simultaneous deposition of cerium oxide and cobalt oxide showed high activity in the oxidation of CO (CO + O 2 , CO + NO) and extensive oxidation of hexane (C 6 H 14 + O 2 ). This behavior is due to the increased mobility of surface oxygen and increased dispersion of the catalyst components.Key words: cobalt oxide, cerium oxide, palladium, oxidation of CO, extensive oxidation of hexane, surface oxygen.The problem of reducing the amount of palladium group metals (PGM) in catalysts to neutralize the exhaust gases of stationary and moving sources is becoming more acute with the increasing world prices of these metals. One method for reducing the PGM content in catalysts is partial replacement of these metals by other substances [1,2]. Transition metal oxides with high surface oxide mobility are promising components of triple-pathway conversion catalysts. Oxides of cobalt, copper, manganese, and nickel as well as complex systems of these oxides have been found to hold promise [2,3]. Rare earth oxide (REO) doping may increase the activity of transition metal oxide catalysts. Considerable interest has been found in systems containing cobalt oxide (Co 3 O 4 ) with REO (CeO 2 , La 2 O 3 ), which display high activity in the oxidation of CO and hydrocarbons and the reduction of NO and may be used for the purification of automobile exhaust gases [1, 4-6]. The high catalytic activity of mixtures of Co 3 O 4 and CeO 2 is attributed to the formation of Co-O-Ce surface clusters during preparation [1,7]. A synergetic effect increasing activity in the oxidation of CO and C n H m has sometimes been observed upon introducing palladium in the cobalt-cerium oxide catalysts [1].High resistance toward the action of water vapor is a feature of cerium-cobalt systems. Such resistance is important for catalysts for the neutralization of internal combustion engine exhaust gases [4]. Furthermore, palladium-promoted oxide catalysts often display higher activity toward the action of sulfur compounds than Pd/Al 2 O 3 [8]. Thus, catalyst compositions based on Co 3 O 4 modified by rare earth oxide additives and containing small amounts of platinum metals as a promoter may be an alternative to platinum metal catalytic converters.We should note that the studies cited above were devoted to the investigation of the interaction of the active components in bulk catalysts, while structurized catalysts with a ceramic or metal framework-forming material, whose wall thickness is comparable to the depth of the working layer, hold the greatest promise for solving practical problems.

The synergistic effect in Co–Ce oxides for catalytic oxidation of diesel soot

“…24,25 XRD patterns of Co-Ce mixed oxides catalysts are shown in This solid solution is believed to be located at the boundary of both oxides. 26 Considering the fact that no additional peak was distinguished apart from CeO 2 and Co 3 O 4 peaks, the content of the solid solution was absolutely in trace amount if it existed. Therefore, it was likely that peak shifts of Co 3 O 4 can largely be attributed to the incorporation of cerium into Co 3 O 4 .…”

Atmospheric Pressure Plasma for Diesel Particulate Matter Treatment: A Review

“…Commonly used catalysts in these studies include mixed metal oxides such as CuFe 2 O 4 [28], CoAlO, NiAlO, CuAlO, etc. [29,30], a precious gold metal such as Pt-Pd, and rare earth metal oxides such as LaCoO 3 and CoCeO [31][32][33]. The presence of catalysts in DPF enables one to simultaneously remove soot and NO x by the reaction between them, leading to the formation of CO 2 and N 2 , which are non-toxic.…”