Acid-modified clinoptilolite as a support for palladium–copper complexes catalyzing carbon monoxide oxidation with air oxygen
Samples of natural clinoptilolite were modified by an acid–thermal method at nitric acid concentrations of 0.25, 0.5, 1.0, and 3.0 M and a contact time of 30 min. A series of catalysts, K2PdCl4–Cu(NO3)2–KBr/S (S = 0.25H-CLI, 0.5H-CLI, 1H-CLI, and 3H-CLI) was obtained. All samples were investigated by X-ray phase and thermogravimetric analysis, FT-IR spectroscopy, water vapor ad/desorption and pH metric method. Besides, K2PdCl4–Cu(NO3)2–KBr/S samples were tested in the reaction of low-temperature carbon monoxide oxidation. It have been found that, owing to special physicochemical and structural-adsorption properties of 3H-CLI, it promotes formation of the palladium–copper catalyst providing carbon monoxide oxidation at the steady-state mode down to CO concentrations lower than its maximum permissible concentration at air relative humidity varied within a wide range.
Pd(II), Cu(II), and pillared clay based nanocatalysts for low-temperature CO oxidation
Pillared clays (PILCs) are little-studied as supports in compositions of anchored metal complex catalysts. In the work, pillared clay, Al-PILC, was prepared by using Ukrainian natural bentonite, N-Bent, and the aluminum polycation, [Al13O4(OH)24(H2O)12]7+ (Al13), as an intercalating agent. The final product was used for preparing К2PdCl4–Cu(NO3)2–KBr/Al-PILC nanocatalysts by an impregnation method. Initial N-Bent and Al-PILC as well as the nanocompositions based on them were characterized by XRD, FT-IR spectroscopy, DTG–DTA, water vapor adsorption, and pH metry. К2PdCl4–Cu(NO3)2–KBr/$${\bar{\text{S}}}$$S¯ compositions ($${\bar{\text{S}}}$$S¯ were N-Bent or Al-PILC) were tested in the reaction of CO oxidation with air oxygen at temperature of 20 °C and a relative humidity of 67%. It has been found that the preliminary modification of natural bentonite by Al13 intercalation results in formation of the nanostructured catalyst with a crystallite size of 19 nm showing the maximum activity in the reaction under study at CPd(II) = 2.72 × 10−5 mol/g and copper(II) concentrations of 2.9 × 10−5 and 5.9 × 10−5 mol/g.
Ozone decomposition and CO oxidation on CeO2
Abstract The reactions of ozone decomposition and CO oxidation by ozone on CeO2 have been investigated. Kinetic experiments were carried out in a gradientless reactor. Ozone decomposition and CO oxidation were found to proceed in the temperature range 10–70°C. Using EPR, TPD and XPS spectroscopy, two different kinds of oxygen species are observed on the oxide surface, one of them being identified as O−3. It has been established that both oxygen species do not participate in CO oxidation. The oxidant in the low-temperature oxidation of CO is highly reactive atomic oxygen (probably O−), which is produced by ozone decomposition on the oxide surface.