The Mechanism of Low-Temperature Oxidation of Carbon Monoxide by Oxygen over the PdCl2–CuCl2/γ-Al2O3 Nanocatalyst

Abstract

The state of palladium and copper on the surface of the PdCl2–CuCl2/γ-Al2O3 nanocatalyst for the low-temperature oxidation of CO by molecular oxygen was studied by various spectroscopic techniques. Using X-ray absorption spectroscopy (XAS), powder X-ray diffraction (XRD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), freshly prepared samples of the catalyst were studied. The same samples were also evaluated after interaction with CO, O2, and H2O vapor in various combinations. It was shown that copper exists in the form of Cu2Cl(OH)3 (paratacamite) nanophase on the surface of the catalyst. No palladium-containing crystalline phases were identified. Palladium coordination initially is comprised of four chlorine atoms. It was shown by XAS that this catalyst is not capable of oxidizing CO at room temperature in the absence of H2O and O2 over 12 h. Copper(II) and palladium(II) are reduced to Cu(I) and Pd(I,0) species, respectively, in the presence of CO and H2O vapor (without O2). It was found by DRIFTS that both linear (2114 cm−1, 1990 cm−1) and bridging (1928 cm−1) forms of coordinated CO were formed upon adsorption onto the catalyst surface. Moreover, the formation of CO2 was detected upon the interaction of the coordinated CO with oxygen. The kinetics of CO oxidation was studied at 18–38 °C at an atmospheric pressure for CO, O2, N2, and H2O (gas) mixtures in a flow reactor (steady state conditions).

Alleviating Climate Change and Pollution with Nanomaterials

“…Nanomaterials that can efficiently use carbon dioxide from the air, capture toxic pollutants from water and degrade solid waste into useful products, are being developed. In line with this theme, seven representative articles [1][2][3][4][5][6][7] have been published in this Special Issue:…”

“…Critically unearthed by Bruk et al [7], palladium at the surface of the PdCl 2 -CuCl 2 /-Al 2 O 3 nanocatalyst is present in the form of PdCl 4 2− , containing amorphous particles, while copper exists as crystal nanophases with the crystal structure of paratacamite (Cu 2 (OH) 3 Cl) and cuprous chloride(II) (CuCl 2 .2H 2 O). The interaction with CO and water vapour results in carbonyl complexes, which are intermediaries in carbon dioxide formation.…”

Composition and Activity of Copper-Palladium Catalyst on Carbon Fiber Material for Air Purification from Carbon Monoxide

“…It was established that the carrier not only affects the equilibria of surface complex formation, 1,2 but also changes the degree of palladium oxidation and the phase state of the copper(II) salt. [12][13][14][15][16][17] Due to the presence of many factors that affect the activity of Pd(ІІ)-Cu(II)/ ( -carriers of different origin) catalysts, there is a need to optimize the properties of the carrier, the method of obtaining and determining the operational characteristics of the catalyst in RPE.…”

Estudio teórico de la oxidación de CO con O2 usando catalizadores de Au-Pd y Au-Pt

“…Una posible solución a este problema, es el diseño e implementación de nuevos catalizadores metálicos efectivos para la adsorción del CO y su oxidación selectiva a CO2 [18][19][20]. Este proceso se conoce como "oxidación preferencial de CO" y es de bajo costo y fácil de implementar.…”